Shift control apparatus and method for hybrid transmission applicable to hybrid vehicle

[0001] 1. Field of the Invention

[0002] The present invention relates to shift control apparatus and method for a hybrid transmission suitable for use in a hybrid vehicle in which a main power source such as an engine and motor/generators are mounted. The present invention particularly relates to the shift control apparatus and method which are capable of having a differential equipment (unit) interposed between the main power source and the motor/generators carry out a continuously variable shift operation.

[0003] 2. Description of the Related Art

[0004] Such a kind of hybrid transmission as described above, for example, includes a differential unit having two degrees of freedom and which is constituted by a planetary gear group or so forth. An input from the engine which is the main power source, an output to a drive system, and a plurality of motor/generators are mutually coupled to respective revolutional members of the differential unit so that powers from the motor/generators permit the continuously variable shift operation. In the above-described hybrid transmission, the motor/generators are driven by means of an electric power of a battery. However, when this driving is carried out, it is necessary for the motor/generators to be driven at a power equal to or lower than a power rating of the battery in the same case as the drive for a normally available electrical equipment.

[0005] A Japanese Patent Application First Publication No. Heisei 9-191506 published on Jul. 22, 1997 exemplifies a previously proposed technique controlling the drive torque to the motor/generators (function as motors) in accordance with a state of the battery. In the previously proposed technique disclosed in the above-identified Japanese Patent Application First Publication, an electric vehicle in which a motor is driven along with a charge-and-discharge of the battery which serves as a power source is prerequisite. When a state variable of the battery is varied by a reference value or more such as reductions in a battery voltage or a battery residual capacity equal to or lower than a reference value, a response speed of a torque control for a drive torque command to the motor is slowed so that an earlier deterioration of the battery is prevented.

[0006] However, if the above-described technique is used to the hybrid transmission of the above-described type which is the prerequisite, viz., the hybrid transmission in which the input from the engine (main power source), the output to the drive system, and the motor/generators are mutually coupled via the differential unit having the two degrees of freedom and the powers from the motor/generators can modify limitlessly a ratio between input and output revolutions of the transmission (shift ratio) by means of the powers from the motor/generators, the battery residual capacity or battery voltage is lowered to a value equal to or lower than the reference value or a battery temperature is raised by a value equal to or higher than a reference value. At this time, if a control form is adopted in which the response speed is slowed to the command of the motor/generator, the following problems occur.

[0007] In details, in such a kind of the hybrid transmission as described above, the drive torque to the output of the drive system and a shift speed (input revolution acceleration) are mutually related to each other. As described in the previously proposed technique, if the drive torques of the motor/generators in accordance with only the state of the battery without the shift speed (input revolution acceleration) taken into consideration are limited, there is a possibility that the shift speed (input revolution acceleration) is in an opposite direction to a direction that the driver has expected. If the shift speed (input revolution acceleration) is in the opposite direction that the driver has desired, an input revolution speed variation (engine revolution speed variation) which is opposite to that the driver has expected from a driving operation occurs. There is a possibility of the shift such that a sense of incompatibility is given to the driver. Then, there is an anxiety that a reduction of a shift quality is introduced.

[0008] It is, therefore, an object of the present invention to provide shift control apparatus and method for a hybrid transmission of a hybrid vehicle in which corrections for the drive torque command value and input revolution acceleration command value are made in such a manner that a combination of a target drive (or driving) torque and a target input revolution acceleration fall within a realizable region, the drive torque command value and input revolution acceleration command value contribute to controls over the main power source (engine) and motor/generators so that a deterioration of the battery developed when the combination of the target drive (driving) torque and the target input revolution acceleration which fall out of the realizable region contributes to the control over the main power source (engine) and the motor/generators is prevented from occurring, and which are capable of eradicating the anxiety on the reduction in the shift quality by making this correction in such a way that the shift speed (input revolution acceleration) is not in the opposite direction to that in which the driver has expected to be directed

[0009] According to one aspect of the present invention, there is provided a shift control apparatus for a hybrid transmission, comprising: a plurality of revolutional members which are enabled to be arranged on a predetermined lever diagram; a differential unit having two degrees of freedom such that if revolution states of two revolutional members thereof are determined, the revolutional states of the other revolutional members are determined, an input of a main power source (ENG), an output to a drive system, and a plurality of motor/generators (MG1, MG2) are coupled to the respective revolutional members of the differential unit to adjust a power from the motor/generators in such a manner that a shift ratio between the main power source and the drive system is varied continuously; a target drive torque calculating section that calculates a target drive torque (T*_oO) to the drive system in accordance with a driving condition; a target input revolution speed calculating section that calculates a target input revolution speed (ω*_E) of one of the revolutional members which is coupled to the main power source (ENG); a target input revolution acceleration calculating section that calculates a target input revolution acceleration (u_io) to converge an actual input revolution (ωi) into the target input revolution speed (ω*i); and a target value correcting section that corrects at least one of the target drive torque (T*_oO) and the target input revolution (u_io) to be a value within a realizable region to be set as a drive torque command value (T*o) and an input revolution acceleration command value (u_io) in such a manner that polarities of the target drive torque (T*_oO) and the target input revolution acceleration (u_io) are left unchanged, in a case where a combination of the target drive torque with the target input revolution acceleration falls out of a realizable region on two-dimensional coordinates of the drive torque and the input revolution acceleration related to a combination of the drive torque and the input revolution acceleration which is feasible in a state of the present motor/generators, a battery for the motor/generators (MG1, MG2), and the main power source, the drive torque command value (T*o) and the input revolution acceleration command value (u_io) contributing to controls of the main power source and the motor/generators (3) in place of the target drive torque (T*_oO) and the target input revolution acceleration (u_io).

[0010] According to another aspect of the present invention, there is provided a shift control method for a hybrid transmission, the hybrid transmission comprising: a plurality of revolutional members which are enabled to be arranged on a predetermined lever diagram; and a differential unit having two degrees of freedom such that if revolution states of two revolutional members thereof are determined, the revolutional states of the other revolutional members are determined, an input of a main power source, an output to a drive system, and a plurality of motor/generators (MG1, MG2) are coupled to the respective revolutional members of the differential unit to adjust a power from the motor/generators in such a manner that a shift ratio between the main power source and the drive system is varied continuously, and the shift control method comprising: calculating a target drive torque (T*o) to the drive system in accordance with a driving condition; calculating a target input revolution speed (ω*_E) of one of the revolutional members which is coupled to the main power source (ENG); calculating a target input revolution acceleration (u_io) to converge an actual input revolution (ωi) into the target input revolution speed (ω*i); and correcting at least one of the target drive torque (T*_oO) and the target input revolution acceleration (u_io) to be a value within a realizable region to be set as a drive torque command value (T*o) or an input revolution acceleration command value (u_io) in such a manner that polarities of the target drive torque (T*o) and the target input revolution acceleration (u_io) are left unchanged, in a case where a combination of the target drive torque (T*o) with the target input revolution acceleration (u_io) falls out of a realizable region on two-dimensional coordinates of the drive torque (To) and the input revolution acceleration {(d/dt)ωi} related to a combination of the drive torque and the input revolution acceleration which is feasible in a state of the present motor/generators, a battery (P_B) for the motor/generators (MG1, MG2), and the main power source, the drive torque command value (T*o) and the input revolution acceleration command value (u_i) contributing to controls of the main power source (ENG) and the motor/generators (MG1, MG2) in place of the target drive torque (T*_oO) and the target input revolution acceleration (u_io).

[0011] This summary of the invention does not necessarily describe all necessary features so that the invention may also be a sub-combination of these described features.

[0038] Reference will hereinafter be made to the drawings in order to facilitate a better understanding of the present invention.

[0039] FIG. 1A shows a hybrid transmission to which a shift control apparatus in a first preferred embodiment according to the present invention is applicable. In the first embodiment, the hybrid transmission constitutes a transaxle for a front-engine-front-drive (so called, FF) car. In FIG. 1A, a reference numeral 1 denotes a transmission casing in which a Ravigneaux type planetary gear set 2 located at a left side in an axial direction of transmission casing 1 (leftward direction and rightward direction as viewed from FIG. 1A) is incorporated and a composite current two-layer motor 3 located at a right side in the axial direction of transmission casing 1 is incorporated. An engine (main power source) ENG is disposed at an outside (leftward direction) of the transmission casing 1. Ravigneaux type planetary gear set 2, engine ENG, and composite current two-layer motor 3 is coaxially disposed on a main axial line of the hybrid transmission. In transmission casing 1, a countershaft 6 and a differential gear unit 7 are juxtaposed to the main axial line with an offset and are also incorporated into transmission casing 1. Left and right driven road wheels 8 are drivingly coupled to differential gear unit 7.

[0040] Ravigneaux type planetary gear set 2 is a combination of two single pinion planetary gear groups 4 and 5 having a common pinion P2. One of the planetary gear groups located nearer to engine ENG is a first single pinion planetary gear group 4 and the other of the planetary gear groups is a second pinion planetary gear group 5. First single pinion planetary gear 4 is constituted by a sun gear S2 and a ring gear R2 to both of which a long pinion P2 are meshed. A second single pinion planetary gear group 5 is provided with a sun gear S1, a ring gear R1, and a large-diameter short pinion P1 meshed to both of the sun gear S1 and ring gear R1. The short pinion P1 is meshed with a common pinion P2. In addition, pinions P1 and P2 of the planetary gear groups 4 and 5 are revolutionally supported by means of common carrier C.

[0041] Ravigneaux type planetary gear set 2 has a main elements of four revolutional members of sun gear S1, sun gear S2, ring gear R2, and carrier C and is constituted by a differential unit 2 having the two degrees of freedom such that if the revolution speeds of the two revolutional members are determined, the revolution speeds of the other members are determined. An order of revolution speed of the four revolutional members is sun gear (fastest) S1, ring gear R2, carrier C, and sun gear S2 as shown by a lever diagram shown in FIG. 1B.

[0042] Composite current two-layer motor 3 is constituted by an inner rotor 3ri, an annular outer rotor 3ro enclosing inner rotor 3ri, both rotors being revolutionally and coaxially supported within transmission casing 1, a ring shaped stator 3s coaxially mounted in an annular stator 3s is fixedly mounted on transmission casing 1. Annular coil (stator) 3s and inner rotor 3ri constitutes a first motor/generator MG1 and annular coil (stator) 3s and outer rotor 3ro constitutes a second motor/generator MG2. Each of motor/generators MG1 and MG2 functions as a motor which outputs individual direction and velocity (including a stop) in accordance with a supply current when the composite current is supplied as a load and functions as a generator developing an electric power in accordance with a revolution by means of an external force. As shown in the lever diagram of FIG. 1B, in the revolution speed order from the four revolution speed members of Ravigneaux type planetary gear set 2, in the order of sun gear S1, ring gear R2, carrier C, and sun gear S2, first motor/generator MG1, the input from engine ENG which is the main power source, and the output to the road wheel drive system (Out), and second motor/generator MG2 are coupled.

[0043] If this connection is described in details in the following on the basis of FIG. 1A, ring gear R2 serves as an input element to which the engine revolution is inputted as described above. A crankshaft of engine ENG is coupled to ring gear R2. Sun gear S1 is coupled to first motor/generator MG1 (rotor 4ri) via a hollow axle 11 extended toward a rearward direction opposite to engine ENG. Sun gear S2 is coupled to motor/generator MG2 (rotor 4ro) via hollow axle 12 fitted to hollow axle 11 and motor/generator MG1 with a clearance.

[0044] Carrier C serves as an output element on which the revolution is outputted to the wheel drive system. An output gear 14 is coupled to carrier C via a hollow connecting member (output axle) 12. Output axle 14 is disposed between Ravigneaux type planetary gear set 2 and composite current two-layer motor 3 and revolutionally (rotatably) supported within transmission casing 1. Output gear 14 is meshed with counter gear 15 on a countershaft 6. An output revolution of transmission from output gear 14 is transmitted to differential gear unit 7 via counter gear 15 and via countershaft 6. Differential gear unit 7 distributes the output revolution from transmission into left and right driven wheels 8. These elements described above constitute a road wheel drive system.

[0045] The hybrid transmission whose structure has been heretofore described can be represented by the lever diagram shown in FIG. 1B. A lateral axis of the lever diagram shown in FIG. 1B denotes a ratio of distances between the respective revolution members determined according to a gear ratio of the planetary gear of the planetary gear groups 4 and 5. That is to say, when the distance between ring gear R2 and carrier C is 1, the ratio of distance between sun gear S1 and ring gear R2 is denoted by a and the ratio of distance between carrier C and sun gear S2 is denoted by β. A longitudinal axis of the lever diagram denotes a revolution speed of each revolutional member. In details, an engine revolution speed ω_E to ring gear R2 (transmission input revolution speed (ω_i), a revolution speed ω₁ of) motor/generator) sun gear S1, revolution speed ωo of the transmission output (Out) from carrier C, and revolution speed ω₂ of sun gear S2 (motor/generator MG2). If the revolution speeds of the two revolutional members are determined, the other two revolutional members are determined.

[0046] A shift operation of the hybrid transmission will hereinafter be described with reference to the lever diagram shown in FIG. 1B. The shift operation when a (vehicular) forward (positive) revolution is outputted includes two modes of EV mode and EIVT mode and a backward (reverse) revolution is outputted includes a REV shift operation. In the EV mode, as shown in lever EV shown in FIG. 1B, the output (Out) to the road wheel drive system is determined only by means of a power from both of motor/generators MG1 and MG2 (or one of the motor/generators) with engine ENG stopped. In the EIVT mode, as illustrated in lever EIVT mode of FIG. 1B, the output (Out) to the road wheel drive system is determined by means of the powers from engine ENG and both of the motor/generators MG1 and MG2.

[0047] The REV shift operation for the backward (reverse) revolution output is not dependent upon the power from engine ENG as shown by a lever REV in FIG. 1B but according to the positive revolution of the one motor/generator MG1, or the reverse revolution of the other motor/generator MG2, or both of the motor/generators (MG1, MG2) revolution from carrier C is outputted to output (Out).

[0048] A shift control system of hybrid transmission carrying out the shift operation control in each mode described above is constituted as shown in FIG. 2. A hybrid controller 21 performs an integration control of both engine ENG and the hybrid transmission. Hybrid controller 21 supplies commands on target torque T*_E and on target revolution speed (ω*_E) (target input revolution speed ω*₁) of engine ENG to an engine controller 22. Engine controller 22 drives engine ENG to have engine ENG achieve this target values T*_E and ω*_E (ω*_i). Hybrid controller 21, furthermore, supplies command signals on target torques T*₁ and T*₂ of motor/generators MG1 and MG2 to motor controller 23. Motor controller 23 controls motor/generators MG1 and MG2 by means of an inverter 24 and a battery 25 to achieve target torques T*₁ and T*₂. Hybrid controller 21 inputs a signal from an accelerator opening angle sensor 26 to detect an accelerator opening angle APO from an accelerator pedal depression depth, a signal from a vehicle speed sensor 27 to detect a vehicle speed VSP (which is proportional to output revolution speed (=ωo), and a signal from an engine speed sensor 28 to detect the engine speed ω_E (=input revolution speed, ω_i).

[0049] Hybrid controller 21 carries out a mode selection to achieve the driving state that the driver has desired from the accelerator pedal depression depth (accelerator opening angle) APO and vehicle speed VSP, and a charged state of battery 25 (SOC state of charge (carrying out enabling power) and executes the shift control in accordance with the selection mode to determine and command the target engine torque T*_E, target engine speed ω*_E (ω*i), and target motor/generator torques T*₁ and T*₂.

[0050] It is noted that revolution speed information inputted to hybrid controller 21 is not limited to engine speed ω_E (ωi) and vehicle speed VSP (vehicle speed and output revolution speed ωo). Since the differential unit constituted by Ravigneaux type planetary gear set 2 has two degrees of freedom, the revolution speeds of any two of the revoltutional members may be inputted to hybrid controller 21.

[0051] FIG. 3 shows a functional block diagram of hybrid controller 21. Hybrid controller 21 includes an input revolution servo controlling section 102, a target value correcting section 103, a motor/generator torque distributing section 104, a motor/generator torque command value determining section 105, and a target engine torque correcting section 106. Target value generating section 101 calculates a target driving torque T*_oO to the road wheel drive system, a target engine revolution speed ω*_E, and a target engine torque T*_Eo from an accelerator pedal depression depth (opening angle) APO, the vehicle speed VSP, and a battery charge state SOC (bringing out enabling power).

[0052] Hence, at first, target driving torque T*_oO to transmission output gear 14 is calculated using a drive torque map shown in FIG. 4 from accelerator depression depth (opening angle of the accelerator APO), vehicle speed VSP. Vehicle speed VSP is calculated using the following equation (1) from, for example, output axle revolution speed ωo.
VSP=k_v·ωo  (1),
wherein kv denotes a constant determined according to a radius of a tire and a final gear ratio. Next, target value generating section 101 calculates a target driving power P*o from target driving torque T*o and output revolution speed ωo as follows:
P*o=ωo×T*o  (2).
Next, target value generating section 101 determines a target battery charge-and-discharge quantity P*_B in such a manner that, as SOC becomes high, the battery discharge quantity becomes increased and, as SOC becomes low, the battery charge quantity becomes increased.

[0053] Finally, target engine revolution speed ω*i and target engine torque T*_EO are calculated as follows from target driving power P*o, engine speed ωi, and target battery charge-and-discharge quantity P*_B. The target engine power P*_E is set in such a way that target engine power P*_E, target driving power P*o, and target charge-and-discharge quantity P*_B have the relations expressed by the following equation:
P*_E=P*o+P*_B  (3).
Next, target engine (revolution) speed ω*E at which the fuel consumption becomes optimum when the target engine power P*_E is generated by the engine is searched from target engine power P*_E using a fuel consumption optimum target engine speed map shown in FIG. 5.

[0054] In order to supply target engine power P*E with the engine and to make an engine operating point a fuel consumption optimum point, there is a thought that a value of target engine power P*_E divided by target engine revolution speed ω*_E should be target engine torque T*_E. However, target value correcting section 103 as will be described later often limits the 4engine (input) revolution acceleration during a shift transient state. In this case, target engine revolution speed ω*E is not be realized. As described above, in a case wherein target engine revolution speed ω*_E is not realized, target engine power P*_E cannot be obtained. Therefore, target engine torque T*_EO is a value of target engine power P*_E divided by an actual engine (revolution) speed ω_I, as expressed by the following equation.

[0055] $\begin{array}{cc}{T}_{\mathrm{EO}}^{*}=\frac{P_E^{*}}{{\omega }_i}.& \left(4\right)\end{array}$

[0056] It is noted that if target engine revolution speed ω*_E is coincident with actual engine (revolution) speed WE during a steady state, the engine torque gives an engine torque whose fuel consumption is optimum. Referring to FIG. 3, an input revolution servo controlling section 102 inputs a deviation between target engine revolution speed ω*_E and actual engine revolution speed ω_E and calculates a target engine (input) revolution acceleration u_io so that the deviation of the input revolution (engine revolution) is decreased. When this calculation is carried out, target engine (input) revolution acceleration u_io may be calculated, for example, using a sliding mode controller as shown in the following equation.

[0057] $\begin{array}{cc}{u}_{\mathrm{io}}=K\frac{\sigma }{\sigma +\varepsilon }.& \left(5\right)\end{array}$
σ=ω*_E−ωi  (6),

wherein ε denotes a constant determining an upper limit of target engine (input) revolution acceleration u_io and denotes a positive constant which makes target engine (input) revolution acceleration u_io continuous in a proximity to zero of σ.

[0058] Referring to FIG. 3, target value correcting section 103 serves to correct target drive torque (or target driving torque) T*_oO and target engine (input) revolution acceleration u_io to a value within the realizable region in a case where a combination of the drive torque To and engine (input) revolution acceleration dωi/dt (or expressed as {(d/dt)ωi} which can be realized under the present engine and state of the battery is expressed on two-dimensional coordinates shown in FIG. 6 with the drive torque To as a lateral axis and with an engine (input) revolution acceleration dω_i/dt as a longitudinal axis and the target drive (driving) torque T*_oO and target engine (input) revolution acceleration dΩ_i/dt falls out of the realizable region expressed on two-dimensional coordinates shown in FIG. 6.

[0059] A relationship from among drive torque To, engine (input) revolution acceleration dω_i/dt, engine revolution speed ωi, output revolution speed ωo, running resistance torque T_R, engine torque T_E, and battery charge-and-discharge quantity P_B is expressed in the following equation (7).

[0060] $\begin{array}{cc}\left(k_{\mathrm{ii}}{\omega }_i+k_{\mathrm{io}}{\omega }_o\right)\frac{d{\omega }_i}{\mathrm{ct}}+\left(k_{\mathrm{oi}}{\omega }_i+k_{00}{\omega }_o\right)T_o=k_R{T}_R+k_E{T}_E+P_B.& \left(7\right)\end{array}$

[0061] It is noted that k_ii, k_io, k_oi, k_oo, k_R, and k_E denote constants determined according to the specifications (inertia moment and radius of revolutional elements in the planetary gear unit of the hybrid system). In this equation (7), it is possible to detect the present engine speed ω_i and output revolution speed ωo are detectable and running resistance torque T_R and engine torque T_E can be estimated using, for example, an external disturbance observer. As shown in FIG. 6, with lateral axis as the drive torque To and longitudinal as engine (input) revolution acceleration dωi, the two-dimensional coordinates is formed. From the range of battery charge-and-discharge quantity using the above equation (7), a region in which drive torque To and engine (input) revolution acceleration dωi/dt fall in a battery rated power (a realizable region) is obtained as shown in A of FIG. 6.

[0062] In this two-dimensional coordinate, suppose that a target operating point determined according to target drive (or driving) torque T*_oO and target engine (input) revolution acceleration u_io. If this target operating point falls out of the realizable region, target operating point does not fall within the battery rated power so that a life of the battery becomes short. Hence, as described below, signs of these target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io is corrected within the value of the realizable region to define a drive torque command value T*o and target engine (input) revolution acceleration u_i. A method of correcting target drive (driving) torque T*_oO and target revolution acceleration u_io will be described below with reference to FIGS. 7A, 7B, and 7C.

[0063] In FIGS. 7A, 7B, and 7C, a target operating point expressed by the combination of target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io before the correction is denoted by o (circle in white) and a command operating point expressed as a combination of a drive torque command value T*o and target engine (input) revolution acceleration u_i after the correction of these physical values is made is denoted by • (circle in black).

[0064] Target operating point ? shown in FIG. 7A indicates a running state at a certain target drive (driving) torque T*_oO without shift (engine (input) revolution acceleration dωi/dt=0). After this, when accelerator pedal is depressed, target operating point ? of FIG. 7A is moved to a broken line denoted by FIG. 7B. In FIG. 7B, since target operating point is present within the realizable region A, the corrections for target drive (driving) torque T*oD and target engine (input) revolution acceleration u_io is not carried out.

[0065] Thereafter, when target operating point o is moved furthermore as denoted by a broken line in FIG. 7C, target operating point o becomes out of realizable region A and the combination of target drive (driving) torque T*_oO and target engine acceleration u_io cannot be realized which is fastest responded cannot be achieved but also becomes out of the battery rated power so that the life of the battery becomes introduced. In this case, target value correcting section 103, in the two-dimensional coordinates of drive torque To and engine (input) revolution acceleration dωi/dt shown in FIG. 7C, assumes the point of circle black • nearest to the target operating point o which is on a line segment denoted by a solid line connecting between the origin on the two-dimensional coordinate and target operating point o corresponding to the combination of target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io. Then, target value correcting section corrects target drive (driving) torque T*_oO and target engine acceleration u_io at the target operating point ? to drive torque T*o and engine (input) revolution acceleration u_i at command operating point • and these corrected drive torque T*o and engine (input) revolution acceleration u_i is set as the drive torque command value and engine acceleration command value and commanded to motor/generator torque distributing section 104.

[0066] Target value correcting section 103 executes the correction process of target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io (determination of drive torque command value T*o and engine (input) revolution acceleration command value u_i) in accordance with a flowchart shown in FIG. 8.

[0067] At a step S10, target value correcting section 103 derives realizable region A expressed on the two-dimensional coordinate of drive torque To and engine (input) revolution acceleration (d/dt)ωi shown in FIGS. 6 and 7 and two boundary lines prescribing this region. These two boundary lines can be calculated in the following equation in which P_B in equation (7) is replaced with a battery rated power±P_Bmax.

[0068] $\begin{array}{cc}\left(k_{\mathrm{ii}}{\omega }_i+k_{\mathrm{io}}{\omega }_o\right)\frac{d{\omega }_i}{dt}+\left(k_{\mathrm{oi}}{\omega }_i+k_{\mathrm{oo}}{\omega }_o\right)T_0=k_R{T}_R+k_E{T}_E+P_{B\max }.& \left(8\right)\\ \left(k_{\mathrm{ii}}{\omega }_i+k_{\mathrm{io}}{\omega }_o\right)\frac{d{\omega }_i}{dt}+\left(k_{\mathrm{oi}}{\omega }_i+k_{\mathrm{oo}}{\omega }_o\right)T_o=k_R{T}_R+k_E{T}_E-P_{B\max }.& \left(9\right)\end{array}$

[0069] At step S11, target value correcting section 103 derives points of intersections (x₁, y₁) and (x₂, y₂) of a straight line denoted by a bold solid line shown in FIG. 7C, passing through target operating point o which is the combination of target drive (driving) torque x₀ (=T*_oO) and target engine (input) revolution acceleration y₀ (=u_io) expressed in the equation (9) and an origin 0 of the two-dimensional coordinates and boundary lines calculated from the above equations (8) and (9) (wherein x₁<x₂ and x₁ and x₂ denote drive torques and y₁ and y₂ denote engine (input) revolution accelerations).

[0070] $\begin{array}{cc}\frac{d{\omega }_i}{dt}=\frac{u_{\mathrm{io}}}{T_{\mathrm{oO}}^{*}}{T}_o.& \left(10\right)\end{array}$

[0071] At a step S12, target value correcting section 103 determines whether x₀ falls between x₁ and x₂. If x₀ is determined to be within x₁ and x₂ (yes), the routine goes to a step S13 since target drive (driving) torque T*o and target engine (input) revolution acceleration u_io falls within a realizable region A. If x₀ is determined not to fall within x₁ and x₂ (no), the control goes to a step S14 since target drive (driving) torque and target engine (input) revolution acceleration is out of realizable region A.

[0072] At step S13 selected when the above-described target drive (driving) torque and target engine (input) revolution acceleration fall within the realizable region A, target operating point o which is the combination of target drive (driving) torque x₀ (=T*_oD) and target engine (input) revolution acceleration y₀(=U_io) is directly set as the post-correction drive torque command value T_o* and target drive engine (input) revolution acceleration u_io is directly set as the post-correction engine (input) revolution acceleration u_i. At step S14 selected when the above-described target drive (driving) torque and target engine (input) revolution acceleration do not fall within realizable region A. The operating points of one of both of (x₁. y₁) and (x₂, y₂) which is nearer to (x₀, y₀) is served as the command operating point and the drive torque T*_o and engine (input) revolution acceleration u_i are respectively set as the post-correction drive torque command value T*_o and the post-correction engine (input) revolution acceleration command value u_i. Hence, post-correction drive torque command value T*o and post-correction engine (input) revolution acceleration value u_i have the same sign (polarity) as target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io.

[0073] Referring back to FIG. 3, motor/generator torque distributing section 104 determines target torques (target motor/generator torques) T*₁₀ and T*₂₀ of motor/generators MG1 and MG2 to achieve post-correction drive torque command value T*o and post-correction engine (input) revolution acceleration command values u_i (transmission command value) even in the steady state nor in the transient state. To determine this target torques T*₁₀ and T*₂₀, the following relationship is established from among engine (input) revolution acceleration dω_i/dt, running resistance torque T_R, engine torque T_E, and the relationship between torques T_{1 and T2} of motor/generators MG1 and MG2.

[0074] $\begin{array}{cc}\frac{d{\omega }_i}{dt}=b_{11}{T}_R+b_{12}{T}_E+b_{13}{T}_1+b_{14}{T}_2.& \left(11\right)\end{array}$

[0075] In addition, the following relationship is established from among drive torque To, running resistance torque T_R, engine torque T_E, and motor/generator torques T₁ and T₂ are established.
T₀=b₂₁T_R+B₂₂T_E+b₂₃T₁+b₂₄T₂  (12).
When equation (11) and equation (12) are combined, the following equation is established.

[0076] $\begin{array}{cc}\left[\begin{array}{c}{T}_1\\ T_2\end{array}\right]=A_c^{-1}\left(\left[\begin{array}{c}\frac{d{\omega }_i}{dt}\\ T_0\end{array}\right]-B_c\left[\begin{array}{c}{T}_R\\ T_E\end{array}\right]\right).A_C=\left[\begin{array}{cc}{b}_{13}& b_{14}\\ b_{23}& b_{24}\end{array}\right],B_c=\left[\begin{array}{cc}{b}_{11}& b_{12}\\ b_{21}& b_{22}\end{array}\right]& \left(13\right)\end{array}$

[0077] If, in equation (13), drive torque To is replaced with post-solution drive torque command value T*o, target engine (input) revolution acceleration (d/dt)ωi is replaced with post-correction engine revolution command value u_i, furthermore, torques T₁ and T₂ of motor/generators MG1 and MG2 are replaced with target motor/generator torques T*₁₀ and T*₂₀, the following equation is obtained, the following equations are obtained. From this equation, target motor/generator torques T*₁₀ and T*₂₀ can be obtained.

[0078] $\begin{array}{cc}\left[\begin{array}{c}{T}_{10}^{*}\\ T_{20}^{*}\end{array}\right]=A_c^{-1}\left(\left[\begin{array}{c}{u}_i\\ T_0^{*}\end{array}\right]-B_c\left[\begin{array}{c}{T}_R\\ T_E\end{array}\right]\right).& \left(14\right)\end{array}$

[0079] It is noted that, running resistance torque T_R and engine torque T_E may directly be detected or, alternatively, may be estimated using an external disturbance observer. In either case, these running resistance torque T_R and engine torque T_E may easily be determined.

[0080] A motor/generator torque command value determining block 105 in FIG. 3 determines motor/generator torque command values T*₁ and T*₂ by correcting target motor/generator torques T*₁₀ and T*₂₀ to values within the torque range in which target motor/generator torques T*₁₀, T*₂₀ can be outputted in a case where each target motor/generator torques T*₁₀ and T*₂₀ obtained by motor/generator torque distributing section 104 as described above is in excess of a mechanically output enabled torque range and in a case where the achieved target motor/generator torque T*₁₀ and T*₂₀ is in excess of the battery rated power.

[0081] Thus, motor/generator torque command value determining section 105 limits motor/generator torques T*₁₀ and T*₂₀ within an output enabled torque range and limits the same target motor/generator torques to become excessive with respect to the battery rated power. These limitations serve to function to protect a earlier deterioration of motor/generators MG1 and MG2 and to protect a demand exceeding the battery rated power from deteriorating the battery at an early timing.

[0082] One example of an algorithm executed by motor/generator torque command value determining section 105 in which target motor/generator torques T*₁₀, T*₂₀ are corrected to values within the output enabled operating enabling (operable) range to determine motor/generator torque command value T*₁ and T*₂ will be described in details with reference to an operational flowchart shown in FIG. 9.

[0083] At a step S20, motor/generator torque command value determining section 105 determines whether each of target motor/generator toques T*₁₀ and T*₂₀ is within the mechanically output enabled torque range and is within the operable region not exceeding the battery rated power.

[0084] The operable region of target motor/generator torques T*₁₀ and T*₂₀ will be described with reference to two-dimensional coordinates of FIG. 10, with torque T₁ of first motor/generator taken along a lateral axis of FIG. 10 and torque T₂ of second motor/generator MG2 taken along a longitudinal axis of FIG. 10.

[0085] In details, the following relationship is established from among battery charge-and-discharge quantity P_B, revolution speed ω₁ and torque T₁ of first motor/generator MG₁, and revolution speed ω₂ and torque T₂ of second motor/generator MG₂.
P_B=ω₁T₁+ω₂T₂  (15).

[0086] It is noted that the present engine (revolution) speed ω₁ and output revolution speed ω_o are detectable. Using equation (15), a region FA which is a region in which the drive torque and engine revolution speed fall within the battery rated power from the range of battery charge-and-discharge quantity P_B is obtained as shown in FIG. 10. Next, a mechanical operation range of composite current two-layer motor 3 can be determined as a region FB shown in FIG. 10 as appreciated from the following explanation. That is to say, in the case of composite current two-layer motor 3, the following relationship is present between revolution speeds x₁ and ω₂ of the first and second motor/generators MG1 and MG2 and mechanical torque maximum values T_1max and T_2max. Torque maximum value T_1max of first motor/generator MG1 is expressed by a non-linear function f, of torque maximum value T_2max of second motor/generator MG2 and of revolution speeds ω₁ and ω₂ of both motor/generators MG1 and MG2.
T_1max=f₁(T_2max, ω₁, ω₂)  (16).
Using equation (16), from the present revolution speeds ω₁ and ω₂ of first and second motor/generators MG1 and MG2, a relationship between mechanical torque maximum values T_1max and T_2max of first and second motor/generators MG1 and MG2 is obtained. From this relationship, a mechanical operation range of composite current two-layer motor 3 can be obtained as denoted by region FB of FIG. 10.

[0087] Furthermore, in order to prevent engine (input) revolution acceleration (shift speed) from being placed in the proximity to zero by a predetermined value y_min when target motor/generator torques T*₁₀ and T*₂₀ are corrected, a torque range of first and second motor/generators MG1 and MG2 at a time when engine (input) revolution acceleration indicates a value toward the engine revolution speed acceleration side than the predetermined value y_min at a time when the ante-correction target motor/generator torques T*₁₀ and T*₂₀ are achieved is determined as a region FC in FIG. 10. This region FC is set using equation (11) so as to satisfy the following conditions.
If b₁₁T_R+b₁₂T_E+b₁₃T*₁₀+b₁₄T*₂₀≦0, b₁₁T_R+b₁₂T_E+b₁₃T₁+b₁₄T₂≦y_min  (17).
If b₁₁T_R+b₁₂T_E+b₁₃T*₁₀+b₁₄T₂≦0, b₁₁T_R+b₁₂T_E+b₁₃T₁+b₁₄T₂≦y_min  (18).
It is noted that the above-described predetermined value y_min may be set as follows:

[0088] $\begin{array}{cc}{y}_{\min }=\mathrm{ky}\frac{{\sigma }_y}{\left[{\sigma }_y\right]+{\varepsilon }_y},& \left(19\right)\end{array}$
wherein σy: a deviation between target input revolution speed and actual input revolution speed, εy: a positive constant to make continuous y_min when σy=0, and Ky denotes a positive constant obtained by experiments or computer simulation.

[0089] A region FX on which the above-described region FA in the two-dimensional coordinate, region FB, and region FC are overlapped, on the two-dimensional coordinates of both of motor/generator torques shown in FIG. 10 is the above-described operable region. In a case where three conditions described below are satisfied, target motor/generator torques T*₁₀, T*₂₀ fall in the operable region FX.

(Condition 1)

[0090] The battery charge-and-discharge quantity P_B obtained by substituting target motor/generator torques T*₁₀ and T*₂₀ into equation (15) is equal to or below a battery rated power.

(Condition 2)

[0091] Target motor/generator torque T*₁₀ is smaller than torque maximum value T_imax of first motor/generator MG1 obtained by substituting target motor/generator torques T*₂₀ into equation (16) and target motor/generator torque T*₂₀ is smaller than torque maximum value T_2max of motor/generator torque MG2 obtained by substituting target motor/generator torque T*₁₀ into equation (16).
(Condition 3)
If b₁₁T_R+b₁₂T_E+b₁₃T*₁₀+b₁₄T*₂₀≧0, target motor/generator torques T*₁₀ and T*₂₀ satisfy the relationship of equation (17) and, if b₁₁T_R+b₁₂T_E+b₁₃T*₁₀+b₁₄T*₂₀≦0, target/motor generator torques T*₁₀ and T*₂₀ satisfy the equation (18).

[0092] At a step S20 in FIG. 9, motor/generator torque command value determining section 105 determines whether the above-described three conditions are satisfied and both of target motor/generator torques T*₁₀ and T*₂₀ fall within operable region FX shown in FIG. 10.

[0093] If both of target motor/generator torques T*₁₀ and T*₂₀ fall within the operable region FX at step S20, the routine goes to a step S21. At step S21, motor/generator torque command value determining section 105 directly sets target motor/generator torques T*₁₀ and T*₂₀ without correction as motor/generator torque command values T*₁ and T*₂. If target motor/generator command values T*₁₀ and T*₂₀ are out of operable region FX, at a step S22, motor/generator torque command value determining section 105 corrects target motor/generator torques T*₁₀ and T*₂₀ to values within operable region FX in such a manner that a variation of the drive torque is minimized and sets the corrected target motor/generator torques T*₁₀ and T*₂₀ as motor/generator torque command values T*₁ and T*₂.

[0094] The correction procedures carried out at steps S21 and S22 of FIG. 9 for target motor/generators T*₁₀ and T*₂₀ will hereinafter be described on the basis of FIG. 11 in which operable region FX is extracted from FIG. 10.

[0095] In FIG. 11, o denotes an ante-correction operating point which is a combination of target motor/generator torques T*₁₀ and T*₂₀ which are before the correction processing and • denotes a post-correction operating point which is a combination of motor/generator torque command values of T*₁ and T*₂. A straight line passing through ante-correction operating point o indicates the combination of motor/generator torques T_{1 and T2} which develops the same drive torque as drive torque To which can be obtained from equation (12) achievable according to the realization of ante-correction target motor/generator torque command values T*₁₀ and T*₂₀.

[0096] Patterns on the correction procedures of target motor/generator torques T*₁₀ and T*₂₀ are three patterns of pattern A, pattern B, and pattern C. Individual patterns thereon will be described below.

<<Pattern A>>

[0097] This pattern is a case where the ante-correction operating point o (target motor/generator torques T*₁₀ and T*₂₀) is present in operable region FX. In this case, as described above with reference to step S21 of FIG. 9, target motor/generator torques T*₁₀ and T*₂₀ are not corrected and these are set directly as the post-correction motor/generator torque command values T*₁ and T*₂.

<Pattern B>>

[0098] Pattern B is a case where ante-correction operating point o (target motor/generator torques T*₁₀ and T*₂₀) is out of operable region FX but an equi(equivalent)—drive torque straight line passing through the ante-correction operating point o is intersected across operable region FX. In this case, at step S22 of FIG. 9, operating point • nearest to ante-correction operating point o and which is on the equi-drive torque straight line passing through the ante-correction operating point o and falls within the operable region FX is set as a post-correction operating point. The motor/generator torque command values T₁ and T₂ at this post-correction operating point ? are post-correction motor/generator torque command values T*₁ and T*₂. In this case, the drive torque is not changed even by the correction of target motor/generator torques T*₁₀ and T*₂₀ which (motor/generator torque command values T*₁ and T*₂).
<Pattern C>>
Pattern C is a case where ante-correction operating point o (target motor/generator torques T*₁₀, T*₂₀) falls out of operable region FX and the equi-drive torque straight line is not intersected with the operable region FX. In this case, the operating point which can generate the same drive torque as the drive torque obtained by the achievement of ante-correction target motor/generator torques T*₁₀ and T*₂₀ is not present, Therefore, at step S22 of FIG. 9, the operating point ? which is within the operable region FX and which is nearest to the equi-drive torque straight line passing through ante-operating point o is set as the post-correction operating point. The correction of target motor/generator torques T*₁₀ and T*₂₀ are corrected so that motor/generator torques T₁ and T₂ at this post-correction operating point ? is set as the post-correction motor/generator torque command values T*₁ and T*₂. In this case, the variation in the drive torque along with the correction of target motor/generator torques T*₁₀ and T*₂₀ (motor/generator torque command values T*₁ and T*₂) can be suppressed at minimum.

[0099] According to the corrections of target motor/generator torques T*₁₀ and T*₂₀ described above, if the combination of target torques T*₁₀ and T*₂₀ of both motor/generators MG1 and MG2 (ante-correction operating point o in FIG. 11), as described in pattern A and pattern C, is out of operable region FX determined according to the rated-power of the battery and the capabilities of motor/generators MG1 and MG2, this combination is corrected to the value within operable region FX to provide a combination of motor/generator torque command values T*₁ and T*₂. (post-correction operating point • of FIG. 11). This combination contributes on the control over motor/generators. Therefore, drive commands which exceed the capabilities of motor/generators MG1 and MG2 themselves and the rated power of the battery are not received. Consequently, reductions of the life of the battery and of durability of motor/generators MG1 and MG2 can be avoided.

[0100] When the corrections of target motor/generators T*₁₀ and T*₂₀ are carried out, the corrections are made so that the polarities of the drive torque and engine (input) revolution acceleration according to the post-correction motor/generator torque command values T*₁ and T*₂ are the same as the drive torque and engine (input) revolution acceleration by means of ante-correction target motor/generator torques T*₁₀ and T*₂₀. The generation of the drive torque and the engine (input) revolution acceleration which are opposite to the desired drive torque and the desired engine (input) revolution acceleration by means of the ante-correction target motor/generator torques can be avoided. An unnatural variation in the drive torque and shift speed can be prevented and unpleasant vehicular acceleration/deceleration and the problems on the transmission quantity having the sense of incompatibility can be eliminated.

[0101] When the corrections of target motor/generator torques T*₁₀ and T*₂₀ are made, motor/generator torque command values T*₁ and T*₂ are determined to be the same value as the driving torque obtained by the drive torque by means of ante-correction target motor/generator torques T*₁₀ and T*₂₀ or the value within the region which is nearest to the drive torque described above. Hence, even if the correction of target motor/generator torques T*₁₀ and T*₂₀ is made, the variation in the drive torque is present or an unpleasant vehicular acceleration/deceleration feeling can be eliminated with at least the variation in the drive torque minimized.

[0102] In addition, when target motor/generator torques T*₁₀ and T*₂₀ are corrected, within a region of the two-dimensional coordinates of T_{1 and T2} in which the engine (input) revolution acceleration dωi/dt (shift speed) indicates a value toward which the ante-correction revolution acceleration side than predetermined value y_min between 0 and ante-correction revolution acceleration obtained by the ante-correction target motor/generator torques T*₁₀ and T*₂₀, the correction is carried out so that a difference between the drive torques before and after the corrections of target motor/generator torques T*₁₀ and T*₂₀ is minimized and the target motor/generator torques T*₁₀ and T*₂₀ are corrected to be set as motor/generator torque command values T*₁ and T*₂. Hence, the variation of the drive torque is minimized so that an unpleasant vehicular acceleration or deceleration feeling can be suppressed with the shift speed faster than predetermined value y_min maintained even if target motor/generator torques T*₁₀ and T*₂₀ are corrected.

[0103] Referring back to FIG. 3, target engine torque correcting section 106 serves to correct target engine torque T*_EO in such a manner that a power needed to the gear shift is provided from the engine. The following relationship is present from among a power Pi required for the revolution speed variation of the revolutional members constituting the power transmission mechanism, engine power P_E, motor/generator power P_B, and drive power Po.
P_E+P_B=P_i+P_o  (20).
Hence, even when the revolution speed of any revolutional member in the hybrid transmission such as during the shift operation, it is necessary to supply the power needed for the gear shift by means of engine ENG or motor/generators MG1 and MG2 in order to achieve the target drive (driving) torque.

[0104] However, since motor/generator power P_B is equal to battery charge-and-discharge quantity, a load on the battery is increased when the power required for the shift by means of motor/generators MG1 and MG2 and there is a possibility that the increase of the load exceeds the battery rated power. Because motor/generators MG1 and MG2 compensates for the lack of engine power due to a lag with respect to the target value of the engine torque. Therefore, the power required for the shift is supplied from the engine. It is noted that, as in the case of the hybrid transmission in the first embodiment, the power from a plurality of power sources using the differential unit constituted by the planetary gear mechanism is outputted to the drive axle, a revolutional system kinetic energy as conventional transmission is often not monotonously varied according to the gear ratio depending upon a specification of the hybrid transmission.

[0105] The relationship between the gear shift ratio i_c of the hybrid transmission and kinetic energy U is as shown in FIG. 12A. The revolutional kinetic energy U takes a minimum value at a certain predetermined gear ratio i_co. Hence, in the conventional transmission, although the sign of the revolution kinetic energy variation is the same provided that the direction of the shift is constant, In the case of the hybrid transmission, even if the shift direction is constant, the direction of the revolutional kinetic energy variation is changed with a shift ratio of i_c0 as a boundary, as shown in FIG. 12B. Therefore, in a case where the engine serves to compensate for the required power, a sign of a compensation quantity is needed to be reversed with the shift ratio of i_c0 as a boundary. Herein, the compensation quantity when the power required for the gear shift is provided by the engine is calculated. The kinetic energy U of the revolutional system of the hybrid-transmission can be expressed in the following equation.

[0106] $\begin{array}{cc}U=\sum _{j=1}^n\frac{1}{2}{I}_j{\omega }_j^2,& \left(21\right)\end{array}$
Wherein n denotes the number of revolutional members in the hybrid transmission. If the kinetic energy U described in equation (21) is differentiated with respect to time, the following equation can be obtained,

[0107] $\begin{array}{cc}\frac{dU}{dt}=\sum _{j=1}^n{I}_j{\omega }_j.& \left(22\right)\end{array}$

[0108] In equation (22), the revolution speed of each revolutional member due to the constraint of the revolution speeds of the planetary gear mechanism is given by a linear coupling between engine revolution speed ωi and output revolution speed ωo.

[0109] $\begin{array}{cc}\frac{dU}{dt}=\left(m_{\mathrm{ii}}\frac{d{\omega }_i}{dt}+m_{\mathrm{oi}}\frac{d{\omega }_o}{dt}\right)\omega i_i+\left(m_{\mathrm{io}}\frac{d{\omega }_i}{dt}+m_{\mathrm{oo}}\frac{d{\omega }_o}{dt}\right){\omega }_o.& \left(23\right)\end{array}$

[0110] In equation (23), m_ii, m_io, m_oi, and m_oo denotes constants determined according to the specifications of the hybrid transmission.

• • [0111] dU/dt expressed in equation (23) is a power Pi required for the shift and dωi/dt in equation (23) is the post-correction target engine revolution speed, or obtained from equation (11), or dω_o/dt can be obtained from the following equation (24).

[0112] $\begin{array}{cc}\frac{d{\omega }_o}{dt}={b^{\prime }}_{11}{T}_R+{b^{\prime }}_{21}{T}_E+{b^{\prime }}_{13}{T}_1+{b^{\prime }}_{14}{T}_2.& \left(24\right)\end{array}$

[0113] In equation (24), b′₂₁, b′₂₂, b′₂₃, and b′₂₄ denote constants determined according to the specifications of the hybrid transmission. Target engine torque T*EO is corrected as follows to determine engine torque command value T*_E in order to provide the engine for the power required for the shift.

[0114] $\begin{array}{cc}T{*}_E=T{*}_{\mathrm{EO}}+\frac{p_i}{{\omega }_i}.& \left(25\right)\end{array}$

[0115] If equation (25) is used, the sign of compensation quantity of the power required for the shift is automatically changed with the shift ratio i_co as a boundary. The shift ratio i_co is determined using equation (23). As expressed in the following equation (26), the shift ratio when dU/dt=0 is a kinetic energy minimum gear shift ratio i_cO.

[0116] $\begin{array}{cc}{i}_{\mathrm{co}}=-\frac{m_{\mathrm{ii}}\frac{d{\omega }_i}{dt}+m_{\mathrm{oi}}\frac{d{\omega }_o}{dt}}{m_{\mathrm{io}}\frac{d{\omega }_i}{dt}+m_{\mathrm{oo}}\frac{d{\omega }_o}{dt}}=-\frac{m_{\mathrm{ii}}+m_{\mathrm{oi}}\frac{d{\omega }_o}{d{\omega }_i}}{m_{\mathrm{io}}+m_{\mathrm{oo}}\frac{d{\omega }_o}{d{\omega }_i}}.& \left(26\right)\end{array}$
As expressed in equation (26), kinetic energy minimum shift ratio i_cO is dependent upon input revolution acceleration dωi/dt and output revolution acceleration dω_o/dt. However, during the shift at which the power required for the shift becomes large, the following assumption can be made:
dω_o/dω_i=0  (27).
Using equation (26), kinetic energy minimum gear shift ratio i_co may be the constant.

[0117] $\begin{array}{cc}{i}_{\mathrm{co}}=-\frac{m_{\mathrm{ii}}}{m_{\mathrm{io}}}.& \left(28\right)\end{array}$
In a case of the hybrid transmission in which an engine clutch which is clutched or released between engine ENG and hybrid transmission, each value of m_ii, m_io, m_oi, and m_oo is different dependent upon the clutch state and release state. Consequently, as appreciated from equations (26) and (28), kinetic energy minimum shift ratio i_co is different depending upon the clutched state of engine clutch.

[0118] In the first embodiment of the shift control apparatus, as described above with reference to FIG. 7C and FIG. 8 (step S14), if the combination of target drive (or driving) torque T*_oO and target engine (input revolution acceleration u_io is out of realizable region A, these target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io are corrected so as to change the values within realizable region A and to be set as drive torque command value T*_oO and engine (input) revolution acceleration command value u_i to contribute to controls of engine ENG and motor/generators MG1 and MG2. Hence, an earlier deterioration of the battery developed in the case where target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io which are out of realizable region A directly contribute on the controls of engine ENG and motor/generators MG1 and MG2 can be prevented.

[0119] Then, when target drive (driving) torque

[0120] T*_oO and target engine (input) revolution acceleration u_io are corrected to the values within realizable region A, both signs (polarities) of the corrected drive torque command value T*o and engine (input) revolution acceleration command value u_i are not changed from those of target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io. Hence, if post-correction drive torque command value T*o and engine (input) revolution acceleration command value u_i are used for the controls of engine ENG and motor/generators MG1 and MG2, the shift speed (engine (input) revolution acceleration) is not reversed in the opposite direction that the driver has expected, the situation in which the input revolution speed change which is opposite to the driver's expectation from the driving operation occurs can be avoided, and the anxiety such that the shift gives unpleasant feeling to the driver can be eliminated.

[0121] FIGS. 13A through 13D and FIG. 14 show a correction processing on the target drive (driving) torque and target engine (input) revolution acceleration of the shift control apparatus in a second embodiment according to the present invention. FIGS. 13A through 13D and FIG. 14 correspond to the realizable region diagrams and flowchart of FIGS. 7A through 7C and FIG. 8.

[0122] In the second embodiment, since the structure of the hybrid transmission, the shift control system, and block diagrams dependent on the shift control function are the same as those of the first embodiment shown in FIGS. 1 through 3, the explanations thereof will herein be omitted. Only the correction method of target drive (driving) torque T*_oO and target engine acceleration u_io will be explained with reference to the realizable region diagram in FIGS. 13A through 13D and with reference to the control program shown in FIG. 14.

[0123] In FIGS. 13A, 13B, 13C, and 13D, the target operating point represented by ante-correction target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io are denoted by the white circle ? and the command operating point represented by the post-correction drive torque command value T*o and target engine (input) revolution acceleration u_i is denoted by the black circle •. Target operating point o shown in FIG. 13A indicates a running state without the shift by a certain target drive (driving) torque T*_oO (engine (input) revolution acceleration (d/dt)ωi=0). Thereafter, when the accelerator pedal is depressed, target operating point o is moved as denoted by a broken line of FIG. 13B. However, since target operating point o is placed within realizable region A in FIG. 13B, the correction of target derive torque T*_oO and target engine (input) revolution acceleration u_io is not carried out. Thereafter, when target operating point o is furthermore moved as denoted by a broken line shown in FIG. 13C, target operating point o is out of realizable region A so that the combination of target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_i, which correspond to earliest cannot only be achieved but also does not fall within the rated power of the battery. Consequently, the reduction of the life of the battery is introduced. In this case, target value correcting section 103, on the two-dimensional coordinate of drive torque To and two-dimensional coordinate of engine (input) revolution acceleration (d/dt)ωi shown in FIG. 13C, derives in the following way command operating point • on the basis of target operating point o corresponding to the combination of target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io. Then, target value correcting section 103 sets drive torque T*o and engine (input) revolution acceleration u_i at this command operating point • as the drive torque command value and the engine (input) revolution acceleration command value.

[0124] When command operating point • is determined, since a degree of requirement of the achievement of target drive (driving) torque T*_oO is higher than target engine (input) revolution acceleration u_io particularly when such a shift that both of target driver torque T*_oO and target engine (input) revolution acceleration u_io are abruptly varied occurs. Hence, target drive (driving) torque T*_oO is not corrected but is directly set as drive torque command value T*o but engine (input) revolution acceleration u_io is corrected. Thus, target operating point o which corresponds to the combination of target drive (or driving) torque T*_oO and target engine (input) revolution acceleration u_io is moved by a minimal displacement within realizable region A. At this time, a point • to which above described point ? is moved by minimal displacement is set as command operating point. In more details, a point • which is nearest to target operating point o, which is within realizable region A, and which is on a line segment (a line segment by which target drive (or driving) torque T*_oO is maintained) passing through target operating point o corresponding to the combination of target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io and denoted by a dot-and-dash line parallel to an engine (input) revolution acceleration axis which is a longitudinal axis of FIG. 13C is the command operating point. The drive torque T*o and engine (input) revolution acceleration u_io at this point of is set as the drive torque command value and the engine (input) revolution acceleration command value. Thereby, during the shift operation, while compensating for the achievement of target drive (driving) torque T*o whose degree of importance is high, a minimum correction of only target engine (input) revolution acceleration u_io can move target operating point o to command operating point • within realizable operating region A.

[0125] When target operating point o corresponding to target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io furthermore moved as a broken line shown in FIG. 13D, post-correction engine (input) revolution acceleration command value indicates a small value as denoted by y₂ derived in the way described with reference to FIG. 13C. Thus, this command value becomes smaller than preset engine revolution (input) acceleration lower limit set value y_min. In this way, if engine (input) revolution acceleration command value u_i which becomes smaller than lower limit set value y_min is allowed, engine (input) revolution acceleration command value u_i becomes extremely small so that almost no shift occurs. In worst case, engine (input) revolution acceleration command value u_i indicates a negative value and the situation such that a sense of incompatibility of the shift is developed.

[0126] To avoid such a worst case, as shown in FIG. 13D, in a case where target operating point o is moved, a point of intersection between one of two boundary lines prescribing realizable region A which is nearer to target operating point o (which is called a realizable region boundary line) and a line representing engine revolution (input revolution) acceleration lower limit value y_min is set as command operating point •. Drive torque T*o and engine (input) revolution acceleration u_i at this command operating point • is set as the drive torque command value and the engine (input) revolution acceleration command value. Therefore, the same action and advantage can be achieved, while avoiding engine (input) revolution acceleration command value u_i which does not become less than engine revolution (input revolution) acceleration lower limit set value y_min, thus, while the sense of incompatibility for the shift is prevented from occurring, target operating point ? is moved to command operating point ? within the realizable region A with a minimum correction of target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io. According to the above-described correction, since the correction of target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io can be made smoothly and continuously, development of unnatural vehicular acceleration shock and the development of the engine revolution speed variation can be prevented.

[0127] Target value correcting section 103 executes the above-described correction of target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io (determination of drive torque command value T*o and engine (input) revolution acceleration u_i) in accordance with the operational flowchart shown in FIG. 14. That is to say, at a step S30, target value correcting section 103 derives realizable region A represented on the two-dimensional coordinate of drive torque To and engine (input) revolution acceleration (d/dt)ωi shown in FIGS. 13A through 13D in the same process as described at step S10 shown in FIG. 8 and calculates the two boundary lines prescribing this region according to equations (8) and (9). At a step S31, target value correcting section 103 derives points of intersections (x₀, y₁) and (x₀, y₂) between a straight line passing target operating point (x₀, y₀) corresponding to the combination of target drive (driving) torque x₀ (=T*_oO) and target engine (input) revolution acceleration y₀ (=u_io) shown in FIGS. 13A through 13D and expressed in the following equation and which is parallel to the longitudinal axis, viz., engine (input) revolution acceleration axis of FIGS. 13A through 13D and the two boundary lines prescribing realizable region A as shown in FIGS. 13A through 13D (It is noted that y₁<y₂).
T_o=T*_oO  (29).

[0128] At a step S32, target value correcting section 103 determines whether y₀ is present between y₁ and y₂. If y₀ is present between y₁ and y₂, the routine goes to a step s33 since the combination of target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io fall within realizable region A as shown in FIGS. 13A and 13B. If y₀ is not present between y₁ and y₂ at step S32, the routine goes to a step S34 since the combination of target drive (driving) torque T*o and target engine (input) revolution acceleration u_io is out of realizable region A as shown in FIGS. 13C and 13D.

[0129] At step S33 which is selected when the combination of target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io falls within realizable region A, target operating point ? which is the combination of target drive (driving) torque x_o (=T*_oO) and target engine (input) revolution acceleration y₀ (=u_io) is directly set as the command operating point. Target drive (driving) torque T*_oO is set directly as post-correction target drive (driving) torque command value T*_o and target drive engine (input) revolution acceleration u_io is directly set as post-correction engine (input) revolution acceleration command value u_i.

[0130] At step S34 which is selected when the combination of target drive (or driving) torque T*_oO and target engine (input) revolution acceleration u_io are out of realizable region A, target value correcting section 103 derives a point of intersection (x₀, y_c) between the realizable region boundary line nearer to target operating point (x₀, y₀) and the line expressing T_o=x₀ as shown in FIGS. 13C and 13D. It is noted that the point of intersection (x₀, y_c) is a point wherein target drive (driving) torque T*_oO is not changed but target input revolution acceleration u_io is moved to a point of y_c which is within realizable region A and which is nearest to y₀. At the next step S35, equation (19) is used to calculate engine (input) revolution acceleration lower limit set value y_min.

[0131] At the next step S36, target value correcting section 103 determines whether y_c is located nearer to y₀ side than y_min as shown in FIG. 13C. If with reference to y_min y_c is located toward y₀ side, a sufficient engine (input) revolution acceleration can be obtained (a sufficient shift speed can be obtained) so that the routine goes to a step S37. If, as shown in FIG. 13D, y_c is not located toward y_c, the sufficient engine (input) revolution acceleration is not obtained but the above-described problems may occur so that the routine goes to a step S38.

[0132] At step S37 selected when the sufficient engine (input) revolution acceleration can be obtained (sufficient shift speed can be obtained), as shown in FIG. 13C, point of intersection (x₀, y_c) is set as command operating point, drive torque T*o and engine revolution speed u_i at this command operating point are set as post-correction drive torque command value T*_o and post-correction engine (input) revolution acceleration command value u_i. At step S38 selected when no sufficient engine (input) revolution acceleration is obtained (no sufficient shift speed is obtained), as shown in FIG. 13D, the point of intersection at which one of the two realizable region boundary lines which is nearer to target operating point (x₀, y₀) is intersected with the line expressing engine (dω_i/dt)=y_min is set as command operating point. At this command operating point, drive torque T*_o and engine acceleration u_i are set, respectively, as post-correction drive torque command value T*_o and post-correction engine (input) revolution acceleration command value u_i.

[0133] The polarities (signs) of post-correction drive torque command value T*_o and engine (input) revolution acceleration command value u_i are the same as those of target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io in the same way as described in the first embodiment. Hence, the same action and advantages as described in the first embodiment can be achieved. While engine (input) revolution acceleration command value u_i is not smaller than engine (input) revolution acceleration (input revolution) lower limit set value y_min, hence, no sense of incompatibility for the shift is given, target operating point (x₀, y₀) can be moved to command operating point • within realizable region A with the minimum correction for target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io so that the same action and advantages as the first embodiment can be achieved.

[0134] FIG. 15 shows an operational flowchart executed by target value correcting section 103 of the shift control apparatus in a third preferred embodiment according to the present invention, viz., the correction procedure on target drive (driving) torque and target engine (input) revolution acceleration. In the third embodiment, the structure of the hybrid transmission, the shift control system, and shift control function-dependent block diagram are the same as those shown in FIGS. 1 through 3. Hence, these explanations will be omitted herein. The correcting method for only target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io will be described hereinbelow on the basis of the control program shown in FIG. 15.

[0135] In the second embodiment shown in FIGS. 13A through 13D and FIG. 14, when target operating point ? which corresponds to the combination of target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io is out of realizable region A, target drive (driving) torque T*_oO is not corrected so much but target engine (input) revolution acceleration u_io is mainly corrected. However, in the third embodiment, on contrary to this, target engine (input) revolution acceleration u_io is not so corrected but target drive (driving) torque T*_oO is mainly corrected.

[0136] The target value correcting section 103 in this embodiment calculates two boundary lines prescribing realizable region A expressed on the two-dimensional coordinates (refer to FIGS. 13A through 13D) of the drive torque T*_o and engine (input) revolution acceleration (d/dt)ωi at a step S40 shown in FIG. 15, in the same processing as step S30 of FIG. 14. At the next step S41, target value correcting section 103 drives points of intersections (x₁, y₀) and (x₂, y₀) between the straight line passing through target operating point (x₀, y₀) correspond to target drive (driving) torque x₀ (=T*_oO) and engine (input) revolution acceleration y₀ (=u_io) and parallel to the drive torque axis (lateral axis of FIGS. 13A through 13D) and two realizable region boundary lines (wherein x₁<x₂)=

[0137] $\begin{array}{cc}\frac{d{\omega }_i}{dt}=u_{\mathrm{io}}.& \left(30\right)\end{array}$

[0138] At a step S42, target value correcting section 103 determines whether x₀ falls within an intermediate between x₁ and x₂. If x, is determined to be present between x₁ and x₂, the routine goes to a step S43 since the combination of target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io falls within realizable region A. If x₀ is determined not to fall between x₁ and x₂, since the combination of target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io is out of realizable region A, the routine goes to a step S44. At step S43 selected when the combination of target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_i, is within realizable region A, target operating point which is the combination of target drive (driving) torque x₀ (=T*_oO) and target engine (input) revolution acceleration y₀(=u_io) is set directly to command operating point and target drive (driving) torque T*_oO is set directly as post-correction drive torque command value T*_o, and target drive engine (input) revolution acceleration u_io is directly set as post-correction engine (input) revolution acceleration command value u_i.

[0139] At step S44 selected when the combination of target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io is out of realizable region A, target value correcting section 103 derives the point of intersection (x_c, y₀) between one of the two boundary lines prescribing the realizable region which is nearer to target operating pint (x_o, y_o) and the line expressing (d/dt)ωi=y₀. It is noted that the point of intersection (x_c, y₀) is a point with target input revolution acceleration u_io unchanged and target drive (driving) torque T*_oO is moved to a point x_c within realizable region A which is nearest to x₀. At the next step S45, a drive torque lower limit set value x_min is calculated using the following equation.

[0140] $\begin{array}{cc}{X}_{\min }=\mathrm{Kx}·\frac{{\sigma }_x}{{\sigma }_x+{\varepsilon }_x}.& \left(31\right)\end{array}$
It is noted that σ_x denotes a deviation between target engine (input) revolution speed and actual input revolution speed, ε_x denotes a positive constant with σ_x=0 continuous for x_min. Kx denotes a positive constant obtained, for example, by a previously experiments and computer simulations.

[0141] At the next step S46, target value correcting section 103 determines whether x_c is located toward x₀ side with respect to x_min. If x_c is located toward x₀ side with respect to x_min, the sufficient drive torque can be obtained and the routine goes to a step S47. If x_c is not located toward x₀ side, a sufficient drive torque cannot be obtained and the routine goes to a step S48. At step S47 selected when the sufficient drive torque is obtained, the point of intersection (x_c, y₀) is the command operating point and drive torque T*o and engine (input) revolution acceleration u_io at this command operating point is set to post-correction drive torque command value T*o and post-correction engine (input) revolution acceleration command value u_i. At step S48 selected when no sufficient drive torque is obtained, a point of intersection between one of the two realizable region boundary lines which is nearer to target operating point (x₀. y₀) and the line expressing drive torque To=x_min. is the command operating point. The drive torque T*o and engine (input) revolution acceleration command value u_i, respectively, at this command operating point, are set to post-correction drive torque command value T*_o and post-correction engine (input) revolution acceleration command value u_i.

[0142] Hence, post-correction drive torque command value T*o and engine (input) revolution acceleration command value u_i have respectively the same polarities of target drive (driving) torque T*_oO and target engine acceleration u_io as described in the second embodiment. The same action and advantages can be achieved. While drive torque command value T*o is smaller than predetermined drive torque limit value set value x_min, target operating point (x_o, y_o) can be moved to the command operating point within realizable region A with minimum correction of target drive (driving) torque T*_oO and target engine (input) revolution u_io.

[0143] FIG. 16 shows another type of hybrid transmission in which motor/generators MG1 and MG2 are individually and independently installed as different from motor/generators MG1 and MG2 which is constituted by compound current two-layer motor 3. That is to say, circular ring shaped stators 3sl and 3s2 are coaxially arranged and fixedly mounted within transmission casing 1, and rotors 3rl and 3r2 are revolutionally supported by means of stators 3sl and 3s2. Circular ring shaped stator 3S1 and rotor 3rl constitute first motor/generator MG1 near to engine ENG and circular ring shaped stator 3s2 and rotor 3r2 constitute second motor/generator MG2 which is located far away from engine ENG.

[0144] Motor/generators MG1 and MG2 function as respectively motors in accordance with a supply current when a current is supplied to ring shaped stators 3sl and 3s2, individually, in an individual direction. When no current is supplied, each generator is acted which develops the electrical power in accordance with the revolution by means of an external force.

[0145] When motor/generators MG1 and MG2 are coupled to Ravigneaux type planetary gear set 2, rotor 3r2 of first motor/generator MG1 is coupled to sun gear S1 of Ravigneaux type planetary gear set via axle 11 and a rotor 3r2 of second motor/generator MG2 is coupled to sun gear S2 via axle 12.

[0146] In a case where the hybrid transmission is used having the above-described motor/generators MG1 and MG2 as shown in FIG. 16. a control current of motor/generators MG1 and MG2 is required to be supplied to ring shaped stators 3sl and 3s2 individually. Hence, the control system is as shown in FIG. 17 in place of those shown in FIG. 12. That is to say, in the case of FIG. 2, a single inverter common to both motor/generators MG1 and MG2 is only installed. However, in the case of FIG. 17, an inverter 24a for ring shaped stator 3s1 of the first motor/generator MG1 and an inverter 24b for ring shaped stator 3s2 is individually installed for ring shaped stator 3s2 of second motor/generator MG2.

[0147] In this embodiment, hybrid controller 21 is shown in the form of functional block diagram as shown in FIG. 3. In this embodiment, however, the processes in target value correcting section 103 and motor/generator command value determining section 105 are different from that shown in FIG. 3.

[0148] The process at target value correcting section 103 is, in the same way as described in first, second, and third embodiments, such that, in a case where the target operating point corresponding to the combination of target drive (driving) torque and target engine (input) revolution acceleration is out of realizable region on the two-dimensional coordinate on the drive torque and engine (input) revolution acceleration, these target drive (driving) torque and/or target engine (input) revolution acceleration are corrected to the drive torque command value and engine (input) revolution acceleration command value on the command operating point within the realizable region. In this preferred embodiment, the realizable region on the two-dimensional coordinates on the drive torque and engine (input) revolution acceleration is different from realizable region denoted by A shown in FIGS. 6, 7A through 7C, and 13A through 13D, as will be described below.

[0149] From the relationship among drive torque To, engine (input) revolution acceleration (d/dt)ωi, engine revolution speed ωi, output revolution speed ωo, running resistance torque T_R, engine torque T_E, and battery charge-and-discharge quantity P_B, the two-dimensional coordinate with the lateral axis taken as drive torque To and the longitudinal axis taken as engine (input) revolution acceleration (d/dt)ωi, a realizable region which falls within the battery rated power is represented as A shown in FIG. 6. In this embodiment, a region BC of drive torque and engine (input) revolution acceleration by means of a torque mechanically generable through motor/generators MG1 and MG2 is derived as shown in FIG. 18 and a region D shown in FIG. 19 which is an overlapped region between region BC and region A is called realizable region.

[0150] Before explanation of the derivation of region BC, engine (input) revolution acceleration of the hybrid transmission is expressed as in equation (11) and the drive torque is expressed as in equation (12). I_cb₂₄×equation (11)−b₁₄×equation (12).

[0151] $\begin{array}{cc}\begin{array}{c}{I}_c{b}_{24}\frac{d{\omega }_i}{dt}-b_{14}{T}_0=\left(I_c{b}_{24}{b}_{11}-I_c{b}_{14}{b}_{21}+1\right)T_R+\\ I_c\left(b_{24}{b}_{12}-b_{14}{b}_{22}\right)T_E+\\ I_c\left(b_{24}{b}_{13}-b_{14}{b}_{23}\right)T_1.\end{array}& \left(32\right)\end{array}$

[0152] In addition, the following equation can be derived from I_cb₂₃×equation (11)−b₁₃×equation (12).

[0153] $\begin{array}{cc}\begin{array}{c}{I}_c{b}_{23}\frac{d{\omega }_i}{dt}-b_{13}{T}_o=\left(I_c{b}_{23}{b}_{11}-I_c{b}_{13}{b}_{21}+1\right)T_R+\\ Ic\left(b_{23}{b}_{12}-b_{13}{b}_{22}\right)T_E+\\ I_C\left(b_{23}{b}_{14}-b_{13}{b}_{24}\right)T_2.\end{array}& \left(33\right)\end{array}$

[0154] Using equation (32), from the torque range generable mechanically by motor/generator MG1, the drive torque mechanically generable torque of motor/generator and a region B of engine (input) revolution acceleration can be obtained from FIG. 18. In addition, using equation (33), from a torque range that second motor/generator MG2 mechanically generable, a region C of the drive torque mechanically generable by second motor/generator and engine (input) revolution acceleration can be obtained as shown in FIG. 18. In a case where the independent two motor/generators MG1 and MG2 are used, a region B is uniquely determined without exception from the revolution speed of the present motor/generator MG1 and region C is uniquely determined without exception from the revolution speed of the present motor/generator MG2. It is noted that a region on which region B and region C are overlapped is assumed to be BC.

[0155] Then, as shown in FIG. 19, a realizable region D between drive torque and engine revolution speed is assumed on which region A and region BC are overlapped is assumed. In each of the above-described first through third embodiments, since motor/generators are constituted by the composite current two-layer motor 3, region BC is not obtained. A dependent relationship is present as expressed in equation (16) between revolution speed of motor/generator MG2, maximum torque T_1max of motor/generator MG1, and maximum torque T_2max of second motor/generator MG2. This dependent relationship causes the dependent relationship between regions B and C, as shown in FIG. 20, under the revolution speed of present motor/generator MG1 and revolution speed of present motor/generator MG2, as shown in FIGS. 20A, 20B, and 20C. Region B is narrower as T_2max becomes smaller (T_1max becomes larger) and wider as T_2max becomes larger, (T_1max is smaller). On the other hand, region C becomes wider as T_2max becomes smaller (T_1max becomes larger), as shown in FIGS. 20A, 20B, and 20C. As described above, since region B and region C are variable, region BC on which both are overlapped is variable. It is difficult to include this region BC in realizable region D, as shown in FIG. 19.

[0156] Hereinafter, the process by means of target value correcting section 103 shown in FIG. 3 is executed in accordance with the flowchart shown in FIG. 21 in place of the program shown in FIG. 8. At a step S250, target value correcting section 103 determines whether target operating point which is the combination of target drive (driving) torque x₀ (=T*₀₀) and target engine (input) revolution acceleration y₀ (=u_io) falls within realizable region D described above so as to determine whether target engine torque T*_oO and target engine (input) revolution acceleration u_io are feasible.

[0157] The determination of feasibility is based on the determination of whether target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io are feasible when the following three conditions are satisfied.

(Condition 1)

The battery-and-discharge quantity when target drive (driving) torque T*_oO and target engine acceleration u_io are substituted into equation (7) is equal to or below the battery rated power.

(Condition 2)

T₁ when target drive (driving) torque T*_oO and target revolution acceleration u_io are substituted into equation (32) is a torque mechanically generable at the present revolution speed of the first motor/generator MG1.

(Condition 3)

T2 when target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io are substituted into equation (33) is a mechanically generable torque at the present revolution speed of the motor/generator MG2.

[0158] In a case where target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io are determined to be feasible (realizable) at step S50, at a step S51, target value correcting section 103 sets the target operating point which is a combination of target drive (driving) torque x₀ (=T*_oO) and target engine (input) revolution acceleration y₀ (=u_io) directly as the command operating point, target drive (driving) torque T*_oO is set directly as post-correction drive torque command value T*_o, target drive engine (input) revolution acceleration u_io is directly set as post-correction engine acceleration command value u_i.

[0159] In a case where target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io are determined not to be realizable at step S50, at a step S52, from among points of intersections at which a line segment connecting an origin and the target operating point (x₀, y₀) is intersected with boundary lines of origin A, origin B, and origin C, one point of intersection which is within the realizable region D and which is nearest to target operating point is the command operating point, the drive torque T*o and engine (input) revolution acceleration u_i are respectively set as post-correction drive torque command value T*o and as post-correction engine (input) revolution acceleration value u_i.

[0160] In this embodiment, the process carried out by motor/generator torque command value determining section 105 shown in FIG. 3 is such that, in the same manner as described in each embodiment, when target motor/generator torques T*₁₀ and T*₂₀ from motor/generator torque distributing section 104 are in excess of mechanically output enable torque range or in excess of the battery rated power (is out of operable region), these are output enable range and a value within the battery rated power, these are corrected to values thereof within output enable torque range and battery rated power to form motor/generator torque command values T*₁ and T*₂. Thereby, motor/generator torque command value determining section 105 functions as the protection function against the deterioration of motor/generators MG1 and MG2, earlier deterioration of battery, performs a protection function described above, and performs a fail safe function.

[0161] Hence, also in this embodiment, motor/generator torque command value determining section 105 in accordance with a determination result of step S20 shown in FIG. 9, in details, in accordance with the determination of whether motor/generator torques T*₁₀ and T*₂₀ are within the operable region or are out of the operable region performs the same process as step S21 and step S22. The determination method at step S20 at which the contents of processes of any step should be executed is different. Hereinafter, the details thereof will herein be described. When this determination is carried out, in other words, when target motor/generator torques T*₁₀ and T*₂₀ are determined to fall within operable region. When the determination whether it is out of the region, this determination is made on the basis of regional diagram shown in FIG. 22.

[0162] It is noted that FIG. 22 shows the regional diagram used in this embodiment. In FIG. 22, the lateral axis denotes a torque T, of first motor/generator torque MG1 and the longitudinal axis denotes a torque T₂ of the second motor/generator MG2 so that the two-dimensional coordinates are formed. On the two-dimensional coordinates, an operable region FX which can achieve toques of first and second motor/generators MG1 and MG2 is shown. The region FA and region FC are the same as those described with reference to FIG. 10. and the duplicate explanation will herein be omitted.

[0163] Next, to derive a mechanical operable region of independent two motor/generators MG1 and MG2, in a case of the hybrid transmission having independent two motor/generators MG1 and MG2, an operable range of the torque of first motor/generator MG1 is uniquely determined according to the revolution speed of motor/generator MG1 and the operable range of the torque of the second motor/generator MG2 is uniquely determined according to the revolution speed of motor/generator MG2. Hence, using the relationship between revolution speeds ω₁ and ω₂ of first and second motor/generators MG₁ and MG₂ and maximum torques T_1max and T_2max of first and second motor/generators MG1 and MG2, maximum torque T_1max of first motor/generator MG1 is obtained from the present revolution speed ω₁ of first motor/generator MG1 and maximum torque T_2max of second motor/generator MG2 is obtained from the present revolution speed ω₂ Of second motor/generator MG2.

[0164] From these motor/generator maximum torques T_1max and T_2max, a mechanical operable region FB of motor/generators MG1 and MG2 is obtained as shown in FIG. 22. In the case of the hybrid transmission having independent two motor/generators MG1 and MG2, operable region FB is a rectangular shape. An overlapped area between region FB and region FC are operable region FX of motor/generators MG1 and MG2.

[0165] On the basis of FIG. 22, the target value correcting section 103 determines whether target motor/generator torques T*₁₀ and T*₂₀ are within operable region FX or out of operable region FX. When the following four conditions are satisfied, it can be determined that motor/generator torques T*₁₀ and T*₂₀ are within operable region FX.

(Condition I)

In FIG. 23A, battery charge-and-discharge quantity Obtained by substituting target motor/generator torques T*₁₀ and T*₂₀ into equation (15) is equal to or lower than battery rated power.

(Condition II)

In FIG. 22A, target motor/generator torque T*₁₀ is present within a range of maximum torque T_1max of motor/generator MG1 obtained from the present revolution speed ω₁ of motor/generator MG1.

(Condition III)

[0166] In FIG. 23B, target motor/generator torque T*₂₀ is present within a range of maximum torque T_1max of motor/generators MG1 obtained from the present revolution speed W2 of motor/generator MG2

(Condition IV)

[0167] If b₁₁T_R+b₁₂T_E+b₁₃T*₁₀+b₁₄T*₂₀≦0, target motor/generator torques T*₁₀ n T*₂₀ satisfy the relationship of equation (17) described above and if b₁₁T_R+b₁₂T_E+b₁₃T*₁₀+b₁₄T*₂₀≦0. both of target motor/generator torques T*₁₀, T*₂₀ satisfy the relationship of equation (18).

[0168] In this embodiment, when the above-described four conditions are satisfied at step S20 in FIG. 9, target motor/generator torques T*₁₀ and T*₂₀ are within operable region FX and the step S21 of the same drawing is executed. When, at step S20 of FIG. 9, the above-described four conditions are not satisfied, the step S22 is executed since motor/generator torques T*₁₀, T*₂₀ are out of operable region FX. Therefore, the same action and advantages as described in each of the first through third embodiment can be achieved.

[0169] FIG. 24 shows a correction procedure of target drive (driving) torque and target engine (input) revolution acceleration in place of FIG. 21 and to be executed in a fifth preferred embodiment of the shift control apparatus according to the present invention.

[0170] In this embodiment, the hybrid transmission is the same as FIG. 16 and the shift control system is the same as FIG. 17. Furthermore, hybrid controller 21 in FIG. 16 is the same as FIG. 3 when the functional block diagram is shown. Target value correcting section 103 executes the flowchart of FIG. 24 in place of FIG. 21.

[0171] Herein, a processing of the flowchart shown in FIG. 24 executed by target value correcting section 103 will be described below.

[0172] At a step S60, in the same way as described at step S50 shown in FIG. 21, depending upon whether the target operating point which is the combination of target drive (driving) torque x₀ (=T*_oO) and target engine (input) revolution acceleration y₀ (=u_io) falls within realizable region D shown in FIG. 19, a kind of check by means of target value correcting section 103 is made as to whether target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io is feasible.

[0173] If, at step S60, the determination is made that target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io are determined to be feasible, the routine goes to a step S61. At step S61, the target operating point is set directly as the command operating point which is the combination of target drive (driving) torque x₀(=T*_oO) and target engine (input) revolution acceleration y₀ (=u_io), target drive (driving) torque T*_oO is directly set as post-correction drive torque command value T*O, and target engine (input) revolution acceleration u_io is directly set as post-correction engine (input) revolution acceleration command value u_i. In a case where, at step S60, if determination is made that target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io are not feasible, the routine goes to a step S62. In the same way as described with reference to step S34 in FIG. 14, target value correcting section 103 derives points of intersections (x₀, y_c) between boundary lines of regions A, B, and C (refer to FIGS. 18 and 19) which are nearest to target operating point (x₀, y₀) within realizable region D and a line expressing To=x₀. It is noted that point of intersection (x₀, y_c) is a point at which target drive (driving) torque T*_oO is left unchanged and target input revolution acceleration u_io is moved to a point y_c within realizable region D which is nearest to y₀.

[0174] At the next step S63, target value correcting section 103 calculates engine (input) revolution acceleration lower limit set value y_min in the same way as described with reference to step S35 of FIG. 14. At the next step S64, in the same way as step S36 in FIG. 14, target value correcting section 103 determines whether y₀ falls within y₀ side with respect to y_min. If y_c is located at y₀ side with respect to y_min, the sufficient engine (input) revolution acceleration (the sufficient shift speed) can be obtained. Thus, the routine goes to a step S66. If y_c is not located toward y₀ side with respect to y_min, the routine goes to a step S66.

[0175] At a step S65 selected when the sufficient engine (input) revolution acceleration is obtained (the sufficient shift speed is obtained), in the same way as step S37 in FIG. 14, the point of intersection (x₀, y_c) is set as the command operating point, the drive torque T*o and engine (input) revolution acceleration u_i at this command operating point are set as post-selection drive torque command value T*o and post-correction engine input revolution acceleration command value u_i. At the step S66 selected when the engine (input) revolution acceleration cannot be obtained sufficiently (a sufficient shift speed is not obtained), in the same way as described with reference to step S38 in FIG. 14, a point of intersection which is nearest to the target operating point (x₀, y₀) within realizable region D from among the point of intersections at which the boundary lines of regions A, B, and C (refer to FIGS. 18 and 19) are intersected with the line representing the engine (input) revolution acceleration (d/dt)ωi=y_min is set as the command operating point, drive torque T*o and engine (input) revolution acceleration u_i at this command operating point are set as post-correction drive torque command value T_o* and post-correction engine (input) revolution acceleration command value u_i.

[0176] Hence, the post-correction drive torque command value To* and engine (input) revolution acceleration command value u_i have the same polarities as those of the target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io. The same action and advantages as described in each of the previously described embodiments can be achieved. While the sense of incompatibility with the shift is prevented from occurring (engine revolution (input revolution) acceleration command value u_i does not become a value lower than (predetermined) engine revolution (input revolution) acceleration lower limit value y_min, target operating point (x₀, y₀) can be moved to the command operating point within realizable region D with minimum correction of target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io. Consequently, the same action and advantages as described in each of the first through fourth embodiments can be achieved.

[0177] FIG. 26 shows a correction processing of target drive (driving) torque and target engine (input) revolution acceleration in place of FIG. 21 to be executed by the shift control apparatus of the hybrid transmission in a sixth preferred embodiment according to the present invention. The hybrid transmission in the sixth embodiment is the same as that shown in FIG. 16 and the shift control system is the same as that shown in FIG. 17. Furthermore, hybrid controller 21 in FIG. 16 is the same as depicted in FIG. 3. However, target value correcting section 103 in this embodiment is different from that shown in FIG. 3 in that target value correcting section 103 in this embodiment executed the flowchart shown in FIG. 25 in place of that shown in FIG. 21. Hereinafter, the processing of flowchart that target value correcting section 103 executes will be described below with reference to the flowchart of FIG. 25.

[0178] At a step S70, target value correcting section 103 determines whether the target operating point which is the combination of target drive (driving) torque x₀(=T*_oO) and target engine (input) revolution acceleration y₀(=u_io) falls within realizable region D shown in FIG. 19 so as to determine whether target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io are feasible.

[0179] In a case where, at step S70, target value correcting section 103 determines that target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io are feasible, at a step S71, in the same way as contents of step S51 shown in FIG. 21, the target operating point which is the combination of target drive (driving) torque x₀ (=T*_oO) and target revolution acceleration y₀ (=u_io) is set directly as the command operating point, target drive (driving) torque T*_oO is directly set as post-correction drive torque command value T*o, and target drive engine (input) revolution acceleration u_io is directly set as post-correction engine (input) revolution acceleration command value u_i.

[0180] In a case where, at step S70, target value correcting section 103 determines that target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io are not feasible, the routine goes to a step S72. AT step S72, in the same way as described in step S44 shown in FIG. 15, target value correcting section 103 derives a point of intersection (x_c, y₀) between one of the boundary lines of regions A, B, and C (refer to FIGS. 18 and 19) which is nearest to target operating point (x₀, y₀) and which is within realizable region D and a line expressing (d/dt)ωi=y₀.

[0181] Next, at a step S74, target value correcting section 103 determines whether x_c is located toward x₀ side with respect to x_min, in the same way as described at step S46 shown in FIG. 15. If x_c is located toward x₀ side with respect to x_min, the drive torque can sufficiently be obtained and the routine goes to a step S75. If x_c is not located toward x₀ side with respect thereto, the sufficient drive torque cannot be obtained so that the routine goes to a step S76.

[0182] At step S75 selected when the sufficient drive torque is obtained, in the same manner as the step S41 of FIG. 15, point of intersection (x_c, y₀) is set as the command operating point, drive torque T*o and engine (input) revolution acceleration u_i is set as post-correction drive torque command value T*_o and post-correction engine (input) revolution acceleration command value u_i. On the other hand, at step S76 selected when the sufficient drive torque cannot be obtained, in the same way as described at step S38 shown in FIG. 13, point of intersection which is nearest to target operating point (x₀, y₀) within realizable region D from among the points of intersections between the boundary lines of regions A, B, and C (refer to FIGS. 18 and 19) and a line expressing drive torque To=x_min is set as the command operating point. Drive torque T*_o and engine (input) revolution acceleration u_i at this command operating point are set, respectively, as post-correction drive torque command value T*o and post-correction engine (input) revolution acceleration command value u_i.

[0183] Hence, the polarities (signs) of post-correction drive torque command value T*_o and post-correction engine (input) revolution acceleration command value u_i are the same as those of target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io. Thus, the same action and advantages as those of each of the first through fifth embodiments can be achieved. While preventing drive torque command value T*_o from becoming lower than drive torque lower limit value x_min, target operating point (x₀, y₀) can be moved to the command operating point within realizable region D with minimum correction of target drive (driving) torque T*_oO and target engine (input) revolution acceleration u_io.

[0184] Various changes and modifications may be made without departing from the scope and sprit of the present invention which is defined in the appended claims.

[0185] The entire contents of a Japanese Patent Application No. 2003-100773 (filed in Japan on Apr. 3, 2003) are herein incorporated by reference. The scope of the invention is defined with reference to the following claims.