US 5,533,946 AGrant
Engine Deceleration Determination Method/System for Updating a Control Parameter
Issue Date:1996-07-09
•8 Claims
•7 Drawing Sheets
Abstract
An adaptive control system/method for an at least partially automated vehicular mechanical transmission system (10) is provided for determining the value of a control parameter (dES/dt) indicative of deceleration of the vehicular engine (E) under minimal fueling.
Metadata
Assignee
- Eaton Corporation
Inventor
- Ronald K. Markyvech
Application Information
Application Number:US 2252716
Filing Date:1994-04-08
Priority Date:1994-04-08
Art Unit:352
Classifications
IPC:
F16H 6340F16H 6104B60K 4106
Field of Search:
4777436478;84;124335424.1
Patent Drawings (7 sheets)
Description
Background of the Invention
1. Related Applications
This application is related to U.S. Ser. No. 08/179,060, entitled ENGINE BRAKE ENHANCED UPSHIFT CONTROL METHOD/SYSTEM, filed Jan. 7, 1994, now U.S. Pat. No. 5,425,689 and assigned to the same assignee, EATON CORPORATION, as is this application.
This application is related to U.S. Ser. No. 08/192,522, entitled METHOD/SYSTEM TO DETERMINE GROSS COMBINATION WEIGHT OF VEHICLES, filed Feb. 7, 1994, now pending and assigned to the same assignee, EATON CORPORATION, as is this application.
This application is related to U.S. Ser. No. 08/226,749, entitled ADAPTIVE SHIFT CONTROL METHOD/SYSTEM, filed Apr. 12, 1994, now pending and assigned to the same assignee, EATON CORPORATION, as is this application.
2. Field of Invention
This invention relates to shift control methods/systems for at least partially automated vehicular mechanical transmission systems wherein the probabilities of successfully completing a selected upshift are evaluated in view of existing vehicle operating conditions, including the expected deceleration of the vehicle engine, and only shifts deemed to be feasible are initiated. In particular, the present invention relates to an adaptive shift control method/system for a partially automated vehicular mechanical transmission system of the type shifting without disengagement of the vehicular master clutch which will determine a value indicative of the current deceleration of the engine under minimal fueling conditions and will use this value as a control parameter.
More particularly, the present invention relates to an adaptive shift control for automated mechanical transmission systems which will continuously (during each upshift) update the value of the control parameter indicative of engine deceleration under conditions of minimal fueling.
3. Description of the Prior Art
Fully automatic transmission systems, both for heavy-duty vehicles, such as heavy-duty trucks, and for automobiles, that sense throttle openings or positions, transmission shaft speeds, vehicle speeds, engine speeds, and the like, and automatically shift the vehicle transmission in accordance therewith, are well known in the prior art. Examples of such transmissions may be seen by reference to U.S. Pat. Nos. 3,961,546; 4,081,065 and 4,361,060, the disclosures of which are incorporated herein by reference.
Semi-automatic transmission systems utilizing electronic control units which sense engine fueling, throttle position, engine, input shaft, output shaft and/or vehicle speed, and utilize automatically controlled fuel throttle devices, gear shifting devices and/or master clutch operating devices to substantially fully automatically implement operator manually selected transmission ratio changes are known in the prior art. Examples of such semi-automatic mechanical transmission systems may be seen by reference to U.S. Pat. Nos. 4,425,620; 4,631,679 and 4,648,290, the disclosures of which are incorporated herein by reference.
Another type of partially automated vehicular transmission system utilizes an automatic or semi-automatic shift implementation system/method for a mechanical transmission system for use in vehicles having a manually only controlled engine throttle means and/or a manually only controlled master clutch. The system usually has at least one mode of operation wherein the shifts to be automatically or semi-automatically implemented are automatically preselected. An electronic control unit (ECU) is provided for receiving input signals indicative of transmission input and output shaft speeds and/or engine speed and for processing same in accordance with predetermined logic rules to determine (i) if synchronous conditions exist, and (ii) in the automatic preselection mode, if an upshift or downshift from the currently engaged ratio is required and to issue command output signals to a transmission actuator and/or an engine fuel controller for shifting the transmission in accordance with the command output signals.
Transmission systems of this general type may be seen by reference to U.S. Pat. Nos. 5,050,079; 5,053,959; 5,053,961; 5,053,962; 5,063,511; 5,081,588; 5,089,962; 5,089,965 and 5,272,939, the disclosures of which are incorporated herein by reference.
While the above-described automatic and/or partially automatic shift implementation type vehicular mechanical transmission systems are well suited for their intended applications, they are not totally satisfactory as they will occasionally initiate an attempted shift, which, due to vehicle operating conditions, should not be permitted and/or cannot be completed. This is especially a concern for upshifts of those automated mechanical transmission systems not provided with an automated clutch actuator and/or an input shaft brake and thus have input shaft deceleration limited to the normal or engine brake-assisted decay rate of the engine without the benefit of an input shaft brake.
In accordance with the inventions of aforementioned co-pending U.S. Ser. No. 08/179,060 and U.S. Pat. No. 5,272,939, the above-discussed drawbacks of the prior art are minimized or overcome by the provision of a shift control method/system for a vehicular at least partially automated mechanical transmission system which, upon sensing an automatic or manual selection of an upshift from a currently engaged gear ratio into a target gear ratio will, based upon currently sensed vehicle operating conditions, determine if the selected upshift is feasible (i.e., probably completible) and only initiate feasible shifts.
A criticism of certain less-than-fully automated mechanical transmission systems (such as transmission systems without automatic master clutch control and/or input shaft brakes) is that under certain conditions they may not be able to complete some shifts they start (i.e., on a grade, low-gear shifts, etc.). However, a transmission system does not have to be able to make all shifts under all conditions, it just needs to be smart enough to know not to start a shift it cannot finish. The transmission control, prior to initiation of an upshift, will make a simple passive test for shiftability and requests for non-feasible upshifts are either modified or cancelled.
Upon selection of an upshift from a currently engaged ratio to a target ratio (usually as a function of engine fueling, throttle position, engine speed, vehicle speed and/or currently engaged ratio) vehicle reaction to a torque break shift transient is predicted, usually on the basis of an assumed or determined vehicle gross combined weight (GCW), and vehicle speed during the shift transient into the target ratio is estimated and compared to expected engine speed (equals input shaft speed and is a function of engine deceleration) during the proposed shift transient to determine if the proposed shift is feasible (i.e., can substantial synchronous be achieved).
If the proposed upshift is not feasible, the shift request may be modified (i.e., a skip shift request changed to single shift) or cancelled for a predetermined period of time (such as 10 seconds).
The foregoing logic was not totally satisfactory, as the control parameter value indicative of engine deceleration was a predetermined, fixed parameter which was possibly inaccurate under existing conditions. For example, engine deceleration may be subject to large variations with changes in temperature and/or use of engine-driven accessories, such as air-conditioning or the like.
Summary of the Invention
In accordance with the present invention, the drawbacks of the prior art are minimized or overcome by the provision of an adaptive upshift control for an at least partially automated vehicular mechanical transmission system which determines feasibility of selected upshifts, initiates only those selected upshifts determined to be feasible and, based upon monitored vehicle conditions, continuously updates the value of the control parameter indicative of vehicle deceleration.
In a preferred embodiment of the present invention, the above is accomplished in a vehicular automated mechanical transmission system control of the type having upshift feasibility determination, during each upshift, by calculating the change of engine speed during the entire period of engine speed decay to a synchronous speed, filtering the current engine deceleration value with previously utilized control parameters, and utilizing the filtered value as the new control parameter.
Accordingly, an adaptive control system/method for a vehicular at least partially automated mechanical transmission system is provided which will prohibit initiation of a selected upshift not deemed feasible and which will adaptively modify the logic rules by which upshift adaptability is determined by continuously updating the value of the control parameter indicative of engine deceleration.
This and other objects and advantages of the present invention will become apparent from a reading of the detailed description of the preferred embodiment taken in connection with the attached drawings.
Brief Description of the Drawings
FIG. 1 is a schematic illustration of the vehicular mechanical transmission system partially automated by the system of the present invention.
FIG. 1A is a schematic illustration of the shift pattern of the transmission of FIG. 1.
FIG. 2 is a schematic illustration of the automatic preselect and semi-automatic shift implementation system for a mechanical transmission system of the present invention.
FIG. 3A is a schematic illustration of logic for differentiating signals representative of current vehicle and engine speed.
FIG. 3B is a schematic illustration of logic for calculating an expected vehicle acceleration during the shift transient when zero engine torque is applied to the drive wheels.
FIGS. 4A and 4B are schematic illustrations, in flow chart format, of the inventive control method of the present invention.
FIG. 5 is a graphical representation of an upshift event illustrating both feasible and not feasible attempted shifts.
FIG. 6 is a graphical representation, similar to FIG. 5, of engine speed and input shaft speed during an upshift.
Description of the Preferred Embodiment
Certain terminology will be used in the following description for convenience in reference only and will not be limiting. The words "upwardly", "downwardly", "rightwardly", and "leftwardly" will designate directions in the drawings to which reference is made. The words "forward", "rearward", will refer respectively to the front and rear ends of the transmission as conventionally mounted in a vehicle, being respectfully from left and right sides of the transmission as illustrated in FIG. 1. The words "inwardly" and "outwardly" will refer to directions toward and away from, respectively, the geometric center of the device and designated parts thereof. Said terminology will include the words above specifically mentioned, derivatives thereof and words of similar import.
The term "compound transmission" is used to designate a change speed or change gear transmission having a multiple forward speed main transmission section and a multiple speed auxiliary transmission section connected in series whereby the selected gear reduction in the main transmission section may be compounded by further selected gear reduction in the auxiliary transmission section. "Synchronized clutch assembly" and words of similar import shall designate a clutch assembly utilized to nonrotatably couple a selected gear to a shaft by means of a positive clutch in which attempted engagement of said clutch is prevented until the members of the clutch are at substantially synchronous rotation. A relatively large capacity friction means are utilized with the clutch members and are sufficient, upon initiation of a clutch engagement, to cause the clutch members and all members rotating therewith to rotate at substantially synchronous speed.
The term "upshift" as used herein, shall mean the shifting from a lower speed gear ratio into a higher speed gear ratio. The term "downshift" as used herein, shall mean the shifting from a higher speed gear ratio to a lower speed gear ratio. The terms "low speed gear", "low gear" and/or "first gear" as used herein, shall all designate the gear ratio utilized for lowest forward speed operation in a transmission or transmission section, i.e., that set of gears having the highest ratio of reduction relative to the input shaft of the transmission.
Referring to FIG. 1, a range-type compound transmission 10 of the type at least partially automated by a semi-automatic mechanical transmission system having an automatic preselect mode of operation is illustrated. Compound transmission 10 comprises a multiple speed main transmission section 12 connected in series with a range type auxiliary section 14. Transmission 10 is housed within a housing H and includes an input shaft 16 driven by a prime mover such as diesel engine E through a selectively disengaged, normally engaged friction master clutch C having an input or driving portion 18 drivingly connected to the engine crankshaft 20 and a driven portion 22 rotatably fixed to the transmission input shaft 16.
The engine E is fuel throttle controlled, preferably electronically, and is connected to an electronic data link DL of the type defined in SAE J 1922 or J 1939 protocol, and the master clutch C is manually controlled by a clutch pedal (not shown) or the like. Typically, the clutch C is utilized only for start-from-stop and for inching operation of the vehicle.
Transmissions similar to mechanical transmission 10 are well known in the prior art and may be appreciated by reference to U.S. Pat. Nos. 3,105,395; 3,283,613 and 4,754,665, the disclosures of which are incorporated by reference.
Partially automated vehicular mechanical transmission systems of the type illustrated may be seen by reference to above-mentioned U.S. Pat. Nos. 5,050,079; 5,053,959; 5,053,961; 5,053,962; 5,063,511; 5,089,965 and 5,272,939.
Although the control method/system of the present invention is particularly useful for those automated mechanical transmission systems not having automatic clutch actuators or input shaft brakes, the present invention is not limited to such use.
In main transmission section 12, the input shaft 16 carries an input gear 24 for simultaneously driving a plurality of substantially identical countershaft assemblies 26 and 26A at substantially identical rotational speeds. The two substantially identical countershaft assemblies are provided on diametrically opposite sides of mainshaft 28 which is generally coaxially aligned with the input shaft 16. Each of the countershaft assemblies comprises a countershaft 30 supported by bearings 32 and 34 in housing H, only a portion of which is schematically illustrated. Each of the countershafts is provided with an identical grouping of countershaft gears 38, 40, 42, 44, 46 and 48, fixed for rotation therewith. A plurality of mainshaft gears 50, 52, 54, 56 and 58 surround the mainshaft 28 and are selectively clutchable, one at a time, to the mainshaft 28 for rotation therewith by sliding clutch collars 60, 62 and 64 as is well known in the prior art. Clutch collar 60 may also be utilized to clutch input gear 24 to mainshaft 28 to provide a direct drive relationship between input shaft 16 and mainshaft 28.
Typically, clutch collars 60, 62 and 64 are axially positioned by means of shift forks associated with the shift housing assembly 70, as well known in the prior art. Clutch collars 60, 62 and 64 may be of the well known nonsynchronized double acting jaw clutch type.
Shift housing or actuator 70 is actuated by compressed fluid, such as compressed air, and is of the type automatically controllable by a control unit as may be seen by reference to U.S. Pat. Nos. 4,445,393; 4,555,959; 4,361,060; 4,722,237; 4,873,881; 4,928,544 and 2,931,237, the disclosures of which are incorporated by reference.
Mainshaft gear 58 is the reverse gear and is in continuous meshing engagement with countershaft gears 48 by means of conventional intermediate idler gears (not shown). It should also be noted that while main transmission section 12 does provide five selectable forward speed ratios, the lowest forward speed ratio, namely that provided by drivingly connecting mainshaft drive gear 56 to mainshaft 28, is often of such a high gear reduction it has to be considered a low or "creeper" gear which is utilized only for starting of a vehicle under severe conditions and, is not usually utilized in the high transmission range. Accordingly, while main transmission section 12 does provide five forward speeds, it is usually referred to as a "four plus one" main section as only four of the forward speeds are compounded by the auxiliary range transmission section 14 utilized therewith.
Jaw clutches 60, 62, and 64 are three-position clutches in that they may be positioned in the centered, nonengaged position as illustrated, or in a fully rightwardly engaged or fully leftwardly engaged position by means of actuator 70. As is well known, only one of the clutches 60, 62 and 64 is engageable at a given time and main section interlock means (not shown) are provided to lock the other clutches in the neutral condition.
Auxiliary transmission range section 14 includes two substantially identical auxiliary countershaft assemblies 74 and 74A, each comprising an auxiliary countershaft 76 supported by bearings 78 and 80 in housing H and carrying two auxiliary section countershaft gears 82 and 84 for rotation therewith. Auxiliary countershaft gears 82 are constantly meshed with and support range/output gear 86 while auxiliary section countershaft gears 84 are constantly meshed with output gear 88.
A two-position synchronized jaw clutch assembly 92, which is axially positioned by means of a shift fork (not shown) and the range section shifting actuator assembly 96, is provided for clutching either gear 86 to output shaft 90 for direct or high range operation or gear 88 to output shaft 90 for low range operation of the compound transmission 10. The "shift pattern" for compound range type transmission 10 is schematically illustrated in FIG. 1A.
Range section actuator 96 may be of the type illustrated in U.S. Pat. Nos. 3,648,546; 4,440,037 and 4,614,126, the disclosures of which are incorporated herein by reference.
Although the range-type auxiliary section 14 is illustrated as a two-speed section utilizing spur or helical type gearing, it is understood that the present invention is also applicable to range type transmissions utilizing combined splitter/range type auxiliary sections, having three or more selectable range ratios and/or utilizing planetary type gearing. Also, any one or more of clutches 60, 62 or 64 may be of the synchronized jaw clutch type and transmission sections 12 and/or 14 may be of the single countershaft type.
For purposes of providing the automatic preselect mode of operation and the automatic or semi-automatic shift implementation operation of transmission 10, an input shaft speed (IS) sensor and an output shaft speed (OS) sensor 100 are utilized. Alternatively to output shaft speed sensor 100, a sensor 102 for sensing the rotational speed of auxiliary section countershaft gear 82 may be utilized. The rotational speed of gear 82 is, of course, a known function of the rotational speed of mainshaft 28 and, if clutch 92 is engaged in a known position, a function of the rotational speed of output shaft 90. Further, with main clutch C fully engaged, input shaft speed (IS) will equal engine speed (ES).
The automatic preselect and automatic or semi-automatic shift implementation control system 104 for a mechanical transmission system of the present invention is schematically illustrated in FIG. 2. Control system 104, in addition to the mechanical transmission 10 described above, includes an electronic control unit 106, preferably microprocessor based, for receiving input signals, from the input shaft speed sensor 98, from the output shaft speed sensor 100 (or, alternatively, the mainshaft speed sensor 102) and from the driver control console 108 from a throttle pedal P position sensor 152 and from the engine E though data link DL. The ECU 106 may also receive inputs from an auxiliary section position sensor 110.
The ECU 106 may be of the type schematically illustrated in U.S. Pat. No. 4,595,986, the disclosure of which is incorporated herein by reference. The ECU is effective to process the inputs in accordance with predetermined logic rules to issue command output signals to a transmission operator, such as solenoid manifold 112 which controls the mainsection section actuator 70 and the auxiliary section actuator 96, and to the driver control console 108, and through the data link DL to engine E.
In the preferred embodiment, the driver control counsel allows the operator to manually select a shift in a given direction or to neutral from the currently engaged ratio, or to select a semi-automatic preselect mode of operation, and provides a display for informing the operator of the current mode of operation (automatic or manual preselection of shifting), the current transmission operation condition (forward, reverse or neutral) and of any ratio change or shift (upshift, downshift or shift to neutral) which has been preselected but not yet implemented.
Console 108 includes three indicator lights 114, 116 and 118 which will be lit to indicate that the transmission 10 is in a forward drive, neutral or reverse drive, respectively, condition. The console also includes three selectively lighted pushbuttons 120, 122, and 124 which allow the operator to select an upshift, automatic preselection mode or a downshift, respectively. A pushbutton 126 allows selection of a shift into neutral.
A selection is made by depressing or pushing any one of buttons 120, 122, 124 or 126 and may be cancelled (prior to execution in the case of buttons 120, 124 and 126) by redepressing the buttons. As an alternative, multiple depressions of buttons 120 and 124 may be used as commands for skip shifts. Of course, the buttons and lighted buttons can be replaced by other selection means, such as a toggle switch and/or a toggle switch and light or other indicia member. A separate button or switch for selection of reverse may be provided or reverse may be selected as a downshift from neutral. Also, neutral may be selected as an upshift from reverse or as a downshift from low.
In operation, to select upshifts and downshifts manually, the operator will depress either button 120 or button 124 as appropriate. The selected button will then be lighted until the selected shift is implemented or until the selection is cancelled.
Alternatively, at a given engine speed (ES) (such as above 1700 RPM), the upshift button may be lit and remain lit until an upshift is selected by pushing the button.
The display/control console also may be of the "R-N-D-H-L" (i.e., reverse-neutral-drive-hold-low) type with a manual upshift and downshift selector.
To implement a selected shift, the manifold 112 is preselected to cause actuator 70 to be biased to shift main transmission section 12 into neutral. This is accomplished by the operator or the ECU controller causing a torque reversal by manually momentarily decreasing and/or increasing the supply of fuel to the engine and/or manually or automatically disengaging the master clutch C. See U.S. Pat. No. 4,850,236, the disclosure of which is incorporated herein by reference. As the transmission is shifted into neutral, and neutral is verified by the ECU (neutral sensed for a period of time such as 1.5 seconds), the neutral condition indicia button 116 is lighted. If the selected shift is a compound shift, i.e., a shift of both the main section 12 and of the range section 14, such as a shift from 4th to 5th speeds as seen in FIG. 1A, the ECU will issue command output signals to manifold 112 to cause the auxiliary section actuator 96 to complete the range shift after neutral is sensed in the front box.
When the range auxiliary section is engaged in the proper ratio, the ECU will calculate or otherwise determine, and continue to update, an enabling range or band of input shaft speeds, based upon sensed output shaft (vehicle) speed and the ratio to be engaged (GR.sub.TARGET), which will result in an acceptably synchronous engagement of the ratio to be engaged. As the operator or the ECU, by throttle manipulation, causes the input shaft speed to fall within the acceptable range, the ECU 106 will issue command output signals to manifold 112 to cause actuator 70 to engage the mainsection ratio to be engaged.
Under certain operating conditions of the vehicle, an automatically or manually selected shift may not be completable. These conditions usually involve upshifts when the vehicle is heavy loaded and/or is traveling against a great resistance, such as in mud, up a steep grade and/or into a strong headwind. To achieve substantial synchronous conditions to complete an upshift, the speed of the input shaft 10 (which substantially equals the speed of the engine E with the master clutch engaged) must be lowered to substantially equal the speed of the output shaft 90 (directly proportional to vehicle speed) multiplied by the target gear ratio. As an automated clutch actuator and input shaft brake are not provided, the speed of the input shaft will decrease with the rate of decay of engine speed. Thus, to achieve substantially synchronous conditions for engagement of the target ratio, IS should substantially equal OS*GR.sub.TARGET and, with the master clutch fully engaged, IS will substantially equal ES.
The sequence of an upshift of the illustrated automated mechanical transmission system is graphically illustrated in FIG. 5. Line 200 represents the input shaft speed (IS) at vehicle conditions prior to the upshift point 202 wherein the current gear ratio (GR) is fully engaged, the master clutch C is fully engaged, and ES=IS=OS*GR. Upon a shift into neutral, as the engine is defueled (i.e., fueling of the engine is reduced to a minimum value), the input shaft speed and engine speed will decay at the constant (but not necessarily linear) rate (dIS/dt) represented by line 204 until idle speed 206 is reached. The expected speed of the output shaft 90 during the shift transient when zero engine torque is applied to the vehicle drive wheels (OS.sub.EXPECTED) multiplied by the target gear ratio, which product is the required synchronous speed of the input shaft/engine, is represented by lines 208 and 210 illustrating, respectively, that product at a lesser or greater resistance to motion of the vehicle. As may be seen, under conditions of lower resistance (line 208), synchronous will occur at point 212 and the selected upshift is feasible while, under conditions of greater resistance (line 210), substantial synchronous will not occur and the selected upshift is not feasible.
In a typical diesel engine of a heavy duty truck, the engine/input shaft decay rate is about 300 to 800 RPM and both the engine and vehicle deceleration may be approximated as linear. The specific rate of decay of the engine and/or input shaft may be predetermined or may be learned by differentiating the value of ES and/or IS signals during a defueling condition (see, for example, aforementioned U.S. Pat. No. 4,361,060). The decay rate may vary considerably, however, with temperature and use of engine-driven accessories.
According to the upshift control method/system of the present invention, selected upshifts are evaluated, prior to initiation thereof, to determine if feasible or not feasible, and not feasible selections are either modified or cancelled. Determination of the engine deceleration control parameter for use in feasibility determination according to the control system/method of the present invention is schematically illustrated, in flow chart format, in FIGS. 4A and 4B.
As may be seen by reference to FIG. 5, if the input shaft speed (IS) (as determined by initial input shaft speed at point 202 and the acceleration of the input shaft (dIS/dt)) will be equal to the product of expected output shaft speed at zero torque to the vehicle drive wheels (OS.sub.EXPECTED), which is determined by initial OS(-IS/GR) and the vehicle acceleration (dOS/dt) at current resistance to vehicle motion, multiplied by the numerical value of the target gear ratio (GR.sub.TARGET) at a value greater than a reference (such as engine idle speed 206), then achieving a synchronous shift into the selected target gear ratio is feasible; if not, achieving a substantially synchronous shift into the selected target gear ratio is infeasible. The OS and dOS/dt signals are, of course, equivalent to vehicle speed and vehicle acceleration signals, respectively. The reference value is illustrated as engine idle speed 206 but can be a lower positive value if the master clutch is manually or automatically disengaged.
For purposes of feasibility determination, for vehicles having a widely variable gross combined weight ("GCW"), i.e., combined weight of vehicle, fuel, cargo (if any) passengers (if any) and operator, the controller will determine current GCW. From this information, the system can determine what the vehicle acceleration (usually a deceleration) will be at zero driveline torque, i.e., the slope of line 208 or 210. Based upon this information and a present or learned value of engine decay rate, i.e., the slope of line 204, which may vary with engine speed, operating temperature, operation of an engine brake, etc., the ECU can then determine if, under current vehicle operating conditions, the system is able to successfully complete the proposed upshift. Based upon this information, the control system can then either (i) issue command signals to implement the proposed upshift, or (ii) modify the proposed shift (usually command a single rather than a skip upshift, or (iii) cancel/prohibit the shift request for a predetermined period of time (such as, for example, about 10 seconds).
Briefly, the acceleration of the vehicle at zero torque to the drive wheels can be approximated by the relationship:
where:
A.sub.i =vehicle acceleration at engine torque i to the drive wheels,
C=a constant,
T.sub.i =engine torque i to the drive wheels, and
W=gross combined vehicle weight.
The above relationship is derived as follows:
where:
T=engine torque
W=gross combined vehicle weight
V=vehicle velocity
G=a factor proportional to grade
A=current acceleration
Ci=constants, related to drivetrain and engaged gear ratio
and where:
C.sub.1 W represents engine torque, delivered to the drive wheels, to overcome rolling resistance;
C.sub.2 V.sub.2 represents engine torque, delivered to the drive wheels, to overcome aerodynamic drag;
C.sub.3 .multidot.G.multidot.W represents engine torque, delivered to the drive wheels, to overcome grade resistance; and
C.sub.4 (W/g)A represents engine torque, delivered to the drive wheels to achieve acceleration A
A change in engine torque to the drive wheels, from T.sub.1 to T.sub.2, is represented:
considering that:
the relationship may be rewritten:
Setting T.sub.2 equal to zero torque,
Preferably, gross combined weight of the vehicle is determined during previous upshift events by comparing vehicle accelerations at differing drive wheel torques. If gross vehicle weight is a known substantially constant value, such as in a bus, than the value for CW may be predetermined and memorized, which allows vehicle deceleration at zero torque under current operating conditions to be determined by sensing current engine torque (T.sub.1) and vehicle acceleration (A.sub.1) and solving for A.sub.0 =A.sub.1 -(T.sub.1 /CW).
FIG. 3A schematically illustrates a logic element or subroutine 220 for differentiating various input signals 222, such as OS and/or ES, to determine the derivatives with respect to time thereof, dOS/dt and/or dES/dt, as output signals 224.
FIG. 3B schematically illustrates a logic element or subroutine 226 wherein input signals 228, including signals indicative of engine torque and vehicle acceleration (dOS/dt), are processed according to the logic rules set forth above to determine an output signal value 230 indicative of expected vehicle acceleration (dOS/dt) during the shift transient when no engine torque is applied to the vehicle drive wheels.
The above system automatically evaluates the feasibility, under current vehicle operating conditions, of manually or automatically preselected shifts and either causes such proposed shifts to be executed, modified or cancelled. In the event of a manually selected upshift determined to be unfeasible, the operator may be issued a tactile, audible or visual warning.
For upshifting of automated transmission systems of the type having an engine controlled in certain situations by the ECU, preferably over an electronic datalink of the type defined in the SAE J1922 or J 1939 protocol, the engine is operated in a "predip" mode prior to disengagement of the existing ratio, in a "synchronizing" mode after a shift from the existing ratio into neutral, and in the "throttle recovery" mode immediately after engagement of the target gear ratio. The engine and input shaft speeds in these modes are illustrated in FIG. 6. In the "predip" mode, fueling is modulated to cause driveline torque reversals to relieve torque lock conditions. In the "synchronous" mode, engine fueling is minimized, allowing engine and input shaft speeds to decay down to a synchronous speed for engaging the target gear ratio (ES=IS=OS*GR.sub.TARGET). In the "throttle recovery" mode, the fueling of the engine is smoothly returned to that value indicated by the operator's positioning of the throttle pedal.
To accurately determine the current engine deceleration value while in the synchronous mode of engine operation, and to minimize the effects of noise, torsionals and the like, it is important that for each measurement, the greatest possible differential between initial and final engine speed be utilized, and that a filtering technique be utilized. Accordingly, to determine a value indicative of current engine deceleration, readings must be taken during the synchronous engine control phase of an upshift, and should include a first reading at or near point A in FIG. 6 when the synchronous engine control phase is first initiated, and a second reading at or near point B in FIG. 6 when the synchronous engine control phase is ended or is about to end. The current value for engine deceleration (dES.sub.CURRENT) will then be (RPM.sub.A -RPM.sub.B).div.(Time.sub.A -Time.sub.B). This value is then filtered to provide an updated control parameter, for example:
The control method/system of the present invention is schematically illustrated in FIGS. 4A and 4B. The engine speed deceleration algorithm or subroutine 300 is preferably entered on a known interval (such as 40 milliseconds) and, thus, an incremented counter may be utilized to provide a timer or clock function. Engine deceleration, of course, is only updated during moving upshifts (i.e., output shaft speed exceeding a minimal value).
The occurrence of point A is taken as the first time operation in the synchronous mode is sensed. The occurrence of point B is taken as the first time operation in the throttle recovery mode is sensed. As no measurable change in engine speed is expected in the cycle time between entering subroutine 300 (i.e., about 40 milliseconds), this is a very accurate method of obtaining the maximum magnitude of change in engine speed during the synchronous operation of each upshift.
Experience with heavy-duty vehicles has shown that a 4:1 to 20:1 filtering technique, preferably about a 7:1 filtering technique, provides suitable responsiveness while filtering out the drivetrain noises due to vibrations, torsionals and the like.
The engine deceleration determination system/method of the present invention is preferably effective to sense the operation, manual or automatic, of engine retarding devices, such as engine exhaust brakes, and will either not determine an engine deceleration control parameter if such devices are in operation or, alternatively, will determine and update separate engine deceleration control parameters for unaided and aided engine deceleration conditions.
Accordingly, it may be seen that a relatively simple and inexpensive shift implementation control system/method for automated mechanical transmission system 10 is provided, which automatically evaluates the feasibility, under current vehicle operating conditions, of successfully completing manually or automatically preselected upshifts and adaptively updates, during each moving upshift, the value of the control parameter indicative of engine deceleration.
Although the present invention has been described with a certain degree of particularity, it is understood that various changes to form and detail may be made without departing from the spirit and the scope of the invention as hereinafter claimed.
Claims
I claim:
1. A control system for determining an updated value of a control parameter (dES/dt.sub.UPDATED) indicative of the rate of change of rotational speed (ES) of a vehicular internal combustion engine (E) in a vehicular automated mechanical transmission system during conditions of reduced fueling of the engine, said transmission system comprising a fuel throttle-controlled engine (E), an operator-set fuel throttle device (P), a multiple-speed change-gear mechanical transmission (10) having an input shaft (16) and an output shaft (90) adapted to drive vehicular drivewheels, said input shaft drivingly connected to said engine by a master friction clutch (C) and a control unit (106) for receiving input signals, including an input signal (ES, IS) indicative of input shaft or engine rotational speed and an input signal (THL) indicative of operator's setting of the throttle device and for processing said signals in accordance with predetermined logic rules to determine control parameters and to issue command output signals to transmission system actuators, including means for controlling fueling of the engine and means (70) for controlling shifting of the transmission, said transmission system performing dynamic upshifts from an engaged ratio into a target gear ratio in a sequence of operations, all without disengagement of the master clutch and regardless of operator's setting of the throttle device, said dynamic upshifts comprising: (a) a predip operation wherein fueling of the engine is manipulated to allow disengagement of the engaged gear ratio; (b) after confirmation of disengagement of the engaged gear ratio, a synchronizing operation wherein fueling of the engine is reduced, allowing engine rotational speed to decrease toward the synchronous speed for engagement of the target ratio (ES=IS=OS*GR.sub.T); and (c) after achieving substantial synchronous rotational speed of said engine and causing engagement of said target gear ratio, a throttle recovery operation wherein fueling of the engine is caused to be controlled by sensed operator setting of said throttling device; said control system characterized by: means for, during the predip operation, sensing engine speed; means for sensing initiation of said synchronizing operation, and upon sensing initiation of said synchronizing operation, means for causing sensed engine speed to equal engine speed initial (RPM.sub.A), and means for starting a timing sequence; means for sensing initiation of the throttle recovery operation, and upon sensing initiation of said throttle recovery operation, means for causing engine speed to equal engine speed final (RPM.sub.B), means for sensing elapsed time from starting of said timing sequence; and means for determining the updated value of the control parameter as a function of the difference between engine speed final and engine speed initial and of the elapsed time.
2. The control system of claim 1 wherein said updated value of said control parameter is determined as a filtered average value.
3. The control system of claim 1 wherein said engine and said control unit communicate over an electronic datalink (DL).
4. The system of claim 1 further comprising means for evaluating feasibility of subsequent upshifts as a function of said updated value.
5. A method for determining an updated value of a control parameter (dES/dt.sub.UPDATED) indicative of the rate of change of rotational speed (ES) of a vehicular internal combustion engine (E) in a vehicular automated mechanical transmission system during conditions of reduced fueling of the engine, said transmission system comprising a fuel throttle-controlled engine (E), an operator-set fuel throttle device (P), a multiple-speed change-gear mechanical transmission (10) having an input shaft (16) and an output shaft (90) adapted to drive vehicular drivewheels, said input shaft drivingly connected to said engine by a master friction clutch (C) and a control unit (106) for receiving input signals, including an input signal (ES, IS) indicative of input shaft or engine rotational speed and an input signal (THL) indicative of operator's setting of the throttle device and for processing said signals in accordance with predetermined logic rules to determine control parameters and to issue command output signals to transmission system actuators, including means for controlling fueling of the engine and means (70) for controlling shifting of the transmission, said transmission system performing dynamic upshifts from an engaged ratio into a target gear ratio in a sequence of operations, all without disengagement of the master clutch and regardless of operator's setting of the throttle device, said dynamic upshifts comprising: (a) a predip operation wherein fueling of the engine is manipulated to allow disengagement of the engaged gear ratio; (b) after confirmation of disengagement of the engaged gear ratio, a synchronizing operation wherein fueling of the engine is reduced, allowing engine rotational speed to decrease toward the synchronous speed for engagement of the target ratio (ES=IS=OS*GR.sub.T); and (c) after achieving substantial synchronous rotational speed of said engine and causing engagement of said target gear ratio, a throttle recovery operation wherein fueling of the engine is caused to be controlled by sensed operator setting of said throttling device; said method characterized by: during the predip operation, sensing engine speed; sensing initiation of said synchronizing operation, and upon sensing initiation of said synchronizing operation, causing sensed engine speed to equal engine speed initial (RPM.sub.A), and starting a timing sequence; sensing initiation of the throttle recovery operation, and upon sensing initiation of said throttle recovery operation, causing engine speed to equal engine speed final (RPM.sub.B), sensing elapsed time from starting of said timing sequence; and determining the updated value of the control parameter as a function of the difference between engine speed final and engine speed initial and of the elapsed time.
6. The method of claim 5 wherein said updated value of said control parameter is determined as a filtered average value.
7. The control method of claim 1 wherein said engine and said control unit communicate over an electronic datalink (DL).
8. The method of claim 5 further comprising evaluating feasibility of subsequent upshifts as a function of said updated value.
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