US 4,991,097 AGrant
Method of Stall Torque Management for an Electronic Automatic Transmission System
Issue Date:1991-02-05
•4 Claims
•6 Drawing Sheets
Abstract
A method of reducing stall torque from the engine to the transmission based on a desired engine speed to minimize the potential interference and possible damage to any of the electronically controlled transmission components for an automatic transmission.
Metadata
Assignee
- Chrysler Corporation
Inventors
- Francis M. Fodale
- Howard L. Benford
- Maurice B. Leising
Application Information
Application Number:US 1885979
Filing Date:1988-04-29
Priority Date:1988-04-29
Art Unit:234
Classifications
IPC:
B60K 4118F02P 5145G05D 1702
Field of Search:
74364851;852;858;860;866;872424.01-431.12
Patent Drawings (6 sheets)
Description
Background of the Invention
1. Field Of The Invention
The present invention relates to an automatic transmission primarily intended for motor vehicle use, and more particularly to a method of reducing stall torque from an engine to a transmission that is controlled electronically and hydraulically.
2. Description Of Related Art
Generally speaking land vehicles require three basic components. These components comprise a power plant (such as an internal combustion engine) a power train and wheels. The internal combustion engine produces force by the conversion of the chemical energy in a liquid fuel into the mechanical energy of motion (kinetic energy). The function of the power train is to transmit this resultant force to the wheels to provide movement of the vehicle.
The power train's main component is typically referred to as the "transmission". Engine torque and speed are converted in the transmission in accordance with the tractive-power demand of the vehicle. The vehicle's transmission is also capable of controlling the direction of rotation being applied to the wheels, so that the vehicle may be driven both forward and backward.
A conventional transmission includes a hydrodynamic torque converter to transfer engine torque from the engine crankshaft to a rotatable input member of the transmission through fluid-flow forces. The transmission also includes frictional units which couple the rotating input member to one or more members of a planetary gearset. Other frictional units, typically referred to as brakes, hold members of the planetary gearset stationary during flow of power. These frictional units are usually brake clutch assemblies or band brakes. The drive clutch assemblies can couple the rotating input member of the transmission to the desired elements of the planetary gearsets, while the brakes hold elements of these gearsets stationary. Such transmission systems also typically provide for one or more planetary gearsets in order to provide various ratios of torque and to ensure that the available torque and the respective tractive power demand are matched to each other.
Transmissions are generally referred to as manually actuated or automatic transmissions. Manual transmissions generally include mechanical mechanisms for coupling rotating gears to produce different ratio outputs to the drive wheels.
Automatic transmissions are designed to take automatic control of the frictional units, gear ratio selection and gear shifting. A thorough description of general automatic transmission design principals may be found in "Fundamentals of Automatic Transmissions and Transamles," Chrysler Corporation Training Manual No. TM-508A. Additional descriptions of automatic transmissions may be found in U.S. Pat. No. 3,631,744, entitled "Hydromatic Transmission," issued Jan. 4, 1972 to Blomquist, et al., and U.S. Pat. No. 4,289,048. entitled "Lock-up System for Torque Converter," issued on Sept. 15. 1981 to Mikel, et al. Each of these patents is hereby incorporated by reference.
In general, the major components featured in such an automatic transmission are: a torque converter as above-mentioned; fluid pressure-operated multi-plate drive or brake clutches and/or brake bands which are connected to the individual elements of the planetary gearsets in order to perform gear shifts without interrupting the tractive power; one-way clutches in conjunction with the frictional units for optimization of power shifts, and transmission controls such as valves for applying and releasing elements to shift the gears (instant of shifting), for enabling power shifting, and for choosing the proper gear (shift point control) dependent on shift-program selection by the driver (selector lever), accelerator position, the engine condition and vehicle speed.
The control system of the automatic transmission is typically hydraulically operated through the use of several valves to direct and regulate the supply of pressure. This hydraulic pressure control will cause either the actuation or deactuation of the respective frictional units for effecting gear changes in the transmission. The valves used in the hydraulic control circuit typically comprise spring-biased spool valves, spring-biased accumulators and ball check valves. Since many of these valves rely upon springs to provide a predetermined amount of force, it will be appreciated that each transmission design represents a finely tuned arrangement of interdependent valve components While this type of transmission control system has worked well over the years, it does have its limitations. For example, such hydraulically controlled transmissions are generally limited to one or a very small number of engines and vehicle designs. Therefore, considerable cost is incurred by an automobile manufacturer to design, test, build, inventory and repair several different transmission units in order to provide an acceptable broad model line for consumers.
Additionally, it should be appreciated that such hydraulically controlled transmission systems cannot readily adjust themselves in the field to compensate for varying conditions such as normal wear on the components, temperature swings and changes in engine performance over time. While each transmission is designed to operate most efficiently within certain specific tolerances, typical hydraulic control systems are incapable of taking self-corrective action on their own to maintain operation of the transmission at peak efficiency.
However in recent years, a more advanced form of transmission control system has been proposed, which would offer the possibility of enabling the transmission to adapt itself to changing conditions. In this regard, U.S. Pat. No. 3,956,947, issued on May 18, 1976 to Leising, et al., which is hereby incorporated by reference, sets forth a fundamental development in this field. Specifically, this patent discloses an automatic transmission design which features an "adaptive" control system that includes electrically operated solenoid-actuated valves for controlling certain fluid pressures. In accordance with this electric/hydraulic control system, the automatic transmission would be "responsive" to an acceleration factor for controlling the output torque of the transmission during a shift from one ratio of rotation (between the input and output shafts of the transmission) to another. Specifically, the operation of the solenoid-actuated valves would cause a rotational speed versus time curve of a sensed rotational component of the transmission to substantially follow along a predetermined path during shifting.
3. Objects Of The Present Invention
It is one of the principal objects of the present invention to provide a significantly advanced electronically controlled transmission which is fully adaptive. By fully adaptive it is meant that substantially all shifts are made using closed-loop control (i.e., control based on feedback). In particular, the control is closed loop on speed, speed ratio, or slip speed of either N.sub.t (turbine of the torque converter) and N.sub.e (engine) or a combination of N.sub.t and N.sub.o (output) which will provide the speed ratio or slip speed. This transmission control is also capable of "learning" from past experience and making appropriate adjustments on that basis.
Another object of the present invention is to provide an automatic transmission in which the shift quality is maintained approximately uniform regardless of the engine size, within engine performance variations or component condition (i.e. the transmission control system will adapt to changes in engine performance or in the condition of the various frictional units of the transmission).
It is a more specific object of the present invention to provide a method of reducing stall torque from an engine to a transmission in response to predetermined conditions existing in the transmission.
This application is one of several applications filed on the same date, all commonly assigned and having similar Specification and Drawings, these applications being identified below.
Commonly assigned application Ser. No. 07/187,772, filed Apr. 29, 1988 now U.S. Pat. No. 4,875,391 has been printed in its entirety. The Figures and the entire Specification of that application are specifically incorporated by above copending applications, reference is made to the reference. For a description of the above mentioned U.S. Pat. No. 4,875,391.
Summary of the Invention
To achieve the foregoing objects, the present invention provides a comprehensive four-speed automatic transmission system. While this transmission system particularly features a fully adaptive electronic control system, numerous other important advances are incorporated into this unique transmission system, as will be described below in detail.
The transmission control system includes a microcomputer-based controller which receives input signals indicative of engine speed, turbine speed, output speed (vehicle speed), throttle angle position, brake application, predetermined hydraulic pressure, the driver selected gear or operating condition (PRNODDL), engine coolant temperature, and/or ambient temperature. This controller generates command or control signals for causing the actuation of a plurality of solenoid-actuated valves which regulate the application and release of pressure to and from the frictional units of the transmission system. Accordingly, the controller will execute predetermined shift schedules stored in the memory of the controller through appropriate command signals to the solenoid-actuated valves and the feedback which is provided by various input signals.
Another primary feature of the present invention is to provide an adaptive system based on closed-loop control. In other words, the adaptive control system performs its functions based on real-time feedback sensor information, i.e., the system takes an action which affects the output, reads the effect, and adjusts the action continuously in real-time. This is particularly advantageous because the control actuations can be corrected as opposed to an open loop control in which signals to various elements are processed in accordance with a predetermined program.
In accordance with one aspect of the present invention, a method is provided to reduce stall torque from the engine to the transmission based on a desired engine speed N.sub.e to minimize the potential interference and possible damage to any of the electronically controlled transmission components.
Brief Description of the Drawings
Other objects, features and advantages of the present invention will become more fully apparent from the following detailed description of the preferred embodiment, the appended claims and in the accompanying drawings in which:
FIGS. 26A-H illustrate the engine torque management methodology according to the present invention; FIGS. 26A-D are flow charts of the engine torque management methodology; and FIGS. 26E-H are shift tape graphs with and without engine torque management.
Engine Torque Management Method
Referring to FIGS. 26A through 26D, a method is disclosed to control the engine torque and coordinate its output in response to conditions existing in the transmission 100. More specifically, certain conditions which occur in the transmission 100 will dictate that the torque output from the engine must be controlled in such a way so as to minimize the potential for interference and possible damage with any of the electronically controlled transmission components.
To this end, the methodology begins in the FIG. 26A in block 2920 by beginning a group of steps in the engine control module starting with the saving in memory of a normal spark advance setting. In other words, a normal spark advance is the spark advance that the engine controller 3020 will calculate on its own without regard to what is happening in the transmission 100.
Following through to the next step in decision block 2922, a redundant check is performed to make sure that the engine controller 3020 has acknowledged to the transmission controller 3010 that a control signal has teen received from the transmission controller 3010. If the engine controller 3020 has not yet acknowledged receipt of the signal from the transmission controller 3010, the receipt is acknowledged in block 2924. If the transmission controller 3010 has been acknowledged as checked in decision block 2922, the routine falls through to block 2926.
As previously mentioned, blocks 2922 and 2924 are a redundant check of the acknowledgment of the receipt of a control signal from the transmission controller 3010 to the engine controller 3020. The purpose for the signal from the transmission controller 3010 to the engine controller 3020 is to time the shift event and communicate this to the engine controller 3020 to prevent unwanted conditions from interfering with the shift event in the transmission 100 though the signals are generated and/or received later in the below-described methodology. The blocks 2922 and 2924 exist here to provide a redundant check of the acknowledgement of such a signal to provide additional diagnostic information regarding the mechanism to transmit the signal between the transmission controller 3010 and the engine controller 3020 More specifically, this signal may be transmitted between the transmission controller 3010 and engine controller 3020 by means of a hardwire or by means of a data bus. In the case of a data bus, since instant access to the bus might not be possible, it is recommended that the communication of the shift event signal be handled on a hardware basis and the acknowledgement be handled at a later time as allowed by the data bus protocols.
The next portion of the methodology of engine torque management can be broken into two major sections. The first section deals with the portion of the FIG. 26A beginning with decision blocks or diamonds 2926 and 2934 which deal with the launch or break-away condition. The second major section of the engine torque management methodology is illustrated in FIG. 26A by referring to diamond 2938 and 2946 for the engine torque management under conditions of a shift event at wide open throttle (WOT).
Returning now to the section of FIG. 26A dealing with the launch or break-away condition, the overall control strategy in this condition is to control the engine speed N.sub.e directly, which results in an indirect control of the differential speed between the engine and the turbine 128 of the torque converter 110. This indirectly controls the torque on the torque converter 110 which provides the input into the transmission 100. It should be noted that the torque on the torque converter 110 is the item that must be controlled within certain ranges during a launch or break-away condition. In other words, it is desired to control the engine speed N.sub.e such that the desirable torque, which is acceptable during a launch or break-away condition, will stay within the prescribed boundaries.
Referring again to diamond 2926, certain conditions are checked to see if spark control is needed during launch. More specifically, these conditions include a throttle angle greater than a predetermined value such as approximately 26 degrees and a vehicle or output speed N.sub.o less than a predetermined value such as approximately six miles per hour. These conditions represent those at which peak torques will occur which will be the maximum conditions probably experienced. If the operation of the engine and transmission 100 can be managed properly during these peak torque conditions, the durability and life of the transmission 100 can be extended.
Returning again to diamond 2926, if the conditions of throttle angle and output speed N.sub.o are such that spark control is needed at launch, the methodology advances to block 2928 to look up or calculate a desired maximum engine speed N.sub.e for the current output speed N.sub.o. The concept behind the utilization of a table or a formula to get the desired maximum engine speed N.sub.e with a given output speed N.sub.o is derived from the fact that transmission input (or turbine torque) is equal to the engine torque as multiplied by the torque converter 110 with the amount of multiplication depending on the ratio between the engine N.sub.e and turbine N.sub.t speeds. Using the characteristics of the torque converter 110, a table of engine speed N.sub.e versus turbine speed N.sub.t can be created so that turbine torque is a constant for the launch or break-away condition. Turbine speed N.sub.t is replaced by vehicle or output speed N.sub.o in the table or formula because the latter is already sensed by the engine controller 3020 and is a good approximation.
The methodology next advances to block 2930 to compute an error term which is equal to the difference between the actual engine speed and the desired maximum engine speed. It is desired to control this error term and drive it to zero by adjusting the spark advance versus the error as shown in block 2932. This can be done in many ways, namely by using integration or adjustment methods including formula or look-up tables. The important thing is to drive the error term to zero and adjust the spark advance to accomplish that result. Next, the methodology returns to the main program.
Returning now to diamond 2926, if the conditions are not right for a spark control to occur during launch, the methodology branches from diamond 2926 to diamond 2934 to check to whether or not the launch spark control methodology is finishing. If so, the methodology advances to block 2936 to return the spark advance to its normal condition as determined by the engine controller 3020 and originally sensed through block 2920. In this particular embodiment, the spark advance is merely ramped up to the normal values. It should be appreciated that this can be accomplished in many ways. Next, the methodology returns to the main engine control routine.
If launch spark control is not just finishing at diamond 2934, the methodology advances to diamond 2938 to determine whether the conditions are right for a shift spark control at wide open throttle (WOT). More specifically, wide open throttle is defined as en the throttle angle is greater than or equal to a predetermined value such as 53 degrees, for example. If the conditions are right for a wide open throttle shift spark control, the methodology advances to diamond 2940 and determines whether a start shift signal has been received. More specifically, the engine controller 3020 is signalled by the transmission controller 3010 via a hardwire, for example, between the two. Upon reception of this "start-of-shift" signal, the mythology advances to block 2942 and acknowledges receipt of the signal over the CCD bus. The methodology then advances to block 2944 and the spark advance is held to a predetermined minimum level until an "end-of-shift" signal is received. The ramp down and up and the mimum spark advance level are collectively calibrated for both shifts to achieve a predetermined value such as a 20% reduction in shift energy. Shift energy is determined experimentally. Oncoming element or clutch pressure is measured and then multiplied by delta turbine speed, the difference between old and new gear turbine speeds, to get clutch shift power. Shift power is then integrated over the tie of the shift to get clutch shift energy. Once the spark advances has been ramped down to the minimum level or, if it is already there, held to that value, the methodology returns to the rain engine control program.
Returning to diamond 2940, if the start-of-shift signal has not been received for a wide open throttle shift, the methodology advances to diamond 2946 and determines ether an end-of-shift signal has been received. If the end-of-shift signal has been received, the methodology advances to block 2948 and acknowledges receipt of the end-of-shift signal over the CCD bus. The methodology then advances to block 2950 and ramps the spark advance up to its normal level. The methodology then returns to the main engine control program.
Returning to diamond 2938, if the conditions are not right for shift spark control for a de open throttle shift, the methodology advances to block 2952 and uses a predetermined normal spark advance value. The methodology then returns to the main engine control program. Similarly, at decision block 2946, if an end-of-shift signal has not been received, the methodology advances to block 2952 to use a normal spark advance value. The methodology then returns to the main engine control program.
The above-described engine torque management routine, with respect to a shift condition at wide open throttle, is done from an open loop perspective. That is, predetermined conditions are stored and utilized in the methodology which end up approximating the control desired. However, physical differences between the transmission and engines and even engine controllers which occur during the manufacturing process due to tolerances of components and variations in the componentry due to temperature and other physical conditions, can cause unique characteristics for the individual transmissions, engines, and/or controllers. Therefore, each system will have its own "signature". more specifically, there is no feedback provided in the above routine to adapt or confirm that the control was exactly as theoretically desired.
Therefore, additional methods are proposed which can be implemented essentially anywhere in the engine torque management shift controls for wide open throttle conditions as described above. Two control methods, in particular, are of note. The first can be performed in the transmission controller 3010 and the second can be performed in the engine controller 3020. Both methods rely on the feedback of information available in the individual controllers to closely approximate the shift energy that the articular clutches in the transmission 100 must absorb, by calculating the shift power from the available pieces of information. Next, the shift power is integrated to approximate the shift energy which must be absorbed. It should be appreciated that the methods proposed are calculations and that, without the addition of a pressure sensor to sense the actual pressure on the specific clutch at issue, a direct measurement and subsequent calculation of the actual shift power will be impossible.
Referring to FIGS. 26B and 26C, the two routines are displayed. The first routine which shall be described is from the perspective of closing the loop for wide open throttle shift energy management and the second routine from the perspective of the engine controller 3020.
Referring to FIG. 26B, the routine can, as above-described, be placed essentially anywhere in the transmission module to work with the engine torque management controls for shifting at wide open throttle described in FIG. 26A. The routine or methodology is begun in block 2954 and a calculation is performed to approximate shift power. This is done by utilizing the various parameters available in the transmission controller 3010, namely, turbine speed N.sub.t, the duty cycle (DC) cf the clutches, and the conditions of the pressure switches 646, 648 and 650 which will only be energized or de-energized at certain pressure levels. The calculation is performed essentially by multiplying the approximation of the pressure on the specific clutch in question which is derived from the duty cycle information and the pressure switches, multiplied by the turbine speed N.sub.t.
Next, the routine falls through to block 2956 to calculate the shift energy by integrating the above calculated shift power over time. This calculation represents the approximate shift energy which must be absorbed by the particular clutch during the shift. The routine then falls through to block 2958 to calculate the shift energy error which is equal to a desired shift energy minus the actual shift energy calculated above, the desired shift energy is a predetermined amount which is a maximum condition beyond which the clutch should not be forced to operate. The routine falls through to block 2960 to transmit the error signal calculated in block 2958 to the engine controller 3020.
Next, in block 2962, the engine controller 3020 must take over from the transmission controller 3010 in block 2962 to adjust the spark advance for the particular shift versus the error term. This utilizes the ramp spark advance to a minimum level from block 2944 in FIG. 26A. The adjustment described in block 2962 is used in the next shift which is the result of an accumulated adaptation from previous shifts.
Referring now to the second routine to manage engine torque, the routine is also displayed in FIG. 26C and is from the perspective of the control done in the engine controller 3020. Referring to block 2964, a calculation of the engine horsepower (hp) is made during the shift condition. This is done by the engine controller 3020 taking advantage of various parameters available to it, namely, parameters such as air flow engine speed N.sub.e, injector pulse width (an indirect measure of the amount of fuel used), spark advance, etc. From these variables, the engine horsepower is approximated.
Next, in block 2966, the methodology correlates the calculated engine horsepower with tables stored in memory to approximate the amount of shift power which would be transmitted to the clutches in the electronically controlled transmission 100. This table is experimentally derived and can also be accomplished by means of using a formula. In block 2968, the methodology calculates the shift energy that the clutches in the transmission 100 must absorb. This, as previously stated, is an approximation. In block 2970, the methodology calculates the shift energy error which is the difference between a desired shift energy and that calculated as actual shift energy in block 2968. The desired shift energy is a maximum amount that is predetermined and stored in memory.
Next, in block 2972, the engine controller 3020 adjusts the shift spark versus the error term for use on the next shift. The above "closed loop" methods to age the engine torque during wide open throttle shifts are both performed from an "after the fact" perspective.In other words, they are computed after the shift has occurred and utilized for the next occurrence of the condition.
A technique to handle the "closing the loop" engine torque management during wide open throttle shifts by the engine controller 3020 is also illustrated in FIG. 26D. This routine essentially replaces blocks 2942 and 2944 of FIG. 26A.
The methodology begins in block 2974 with the calculation of the current engine horsepower versus time or r.p.m. This again is an approximation of the engine horsepower above-described with respect to block 2964.
Next, the methodology falls through to block 2976 to correlate the calculated current engine horsepower to a stored table or formula of current electronically transmission shift power. This is analogous to what occurs in block 2966 which has been described above. The methodology then falls through to block 2978 to compare the current shift power found during the correlation in block 2976 with another stored expression, namely, the nominal desired power trace representing a nominal shift power curve. This is used in block 2980 to calculate a power error which is equal to the difference between the nominal desired power trace and the actual shift power correlated from block 2976.
Next, the methodology advances to block 2982 to look up or calculate a spark advance to be used for this particular shift based on the calculated power error from block 2980. The methodology then advances to block 2984 to calculate the shift energy which will be used for further adjustments when next the routine is used. This is similar to the adjustments described with respect to blocks 2962 and 2972.
Referring to FIG. 26E, a shift tape for wide open throttle (WOT) launch without stall torque management is shown. When the operator depresses the accelerator pedal for WOT, the throttle angle represented by curve 2986 flares up immediately and levels off at WOT. This causes engine speed N.sub.e, represented by curve 2987, and spark advance, represented by curve 2988, to also increase and level off at a predetermined value. Correspondingly, wheel torque, represented by curve 2989, flares to a peak before it declines due to a drop off in torque multiplication in the torque converter 110. Wheel torque is a qualitative measure of engine torque.
Referring to FIG. 26F, a shift tape for wide open throttle (WOT) launch with stall torque management according to the present invention is shown. The throttle angle curve 2986, rises from rest to WOT as previously described. The N.sub.e curve 2987 also increases until it reaches a theoretical N.sub.e versus N.sub.o limit which is used to maintain a theoretical amount of torque on the turbine 128. The spark advance curve 2988 is continuously adjusted to control N.sub.e along a desired N.sub.e line (N.sub.e vs. N.sub.o limit). This is accomplished by measuring an error of N.sub.e versus the desired N.sub.e line and computing the error. The spark advance is their adjusted in proportion to the error by a predetermined method such as by point slope interpolation. As a result, N.sub.e is managed, effectively managing engine torque. This can be qualitatively seen in the wheel torque curve 2989, which represents engine torque, by the elimination of a peak, leaving a rough but relatively flat wheel torque curve.
Referring to FIG. 26G, a shift tape for a first to second (1-2) gear upshift without engine torque management is shown. Throttle angle is represented by curve 2990. Thottle angle is at WOT by the time to make the shift occur. A shift timing signal represented by curve 2991 denotes the beginning of the shift at point 2992 and the end of the shift at point 2993. Throttle angle is at WOT before the beginning of the shift.
At the beginning of the shift, N.sub.e, represented by curve 2944, and N.sub.t, represented by curve 2995, rise to a peak and fall to a predetermined value by the end of the shift. The fluid pressure in the apply element (two/four shift clutch 308), represented by curve 2996, starts to increase at the beginning of the shift and levels off to a fairly constant value from approximately half way during the shift to the end of the shift. Shift energy is calculated as the difference between N.sub.t minus N.sub.j multiplied by the net pressure in the oncoming clutch (which is actual pressure minus fill pressure). Similarly, wheel torque, represented by curve 2998 levels off to a fairly constant value from approximately half way during the shift to the end of the shift. Spark advance is represented by curve 2997 and is fairly constant at the beginning of the shift and fails to its normal value by the end of the shift.
Referring to FIG. 26H, the spark advance 2997 is ramped down to the predetermined value at the start of shift at point 2992. The spark advance 2997 is held at the predetermined value until the end of shift at point 2993 where it is ramped up to predetermined normal value. As a result, the fluid pressure 2996 in the apply element (two/four shift clutch 308) does reach the same level as above, but also has a depression or valley 2999 in it until the end of shift. Correspondingly, N.sub.t 2995 falls off more rapidly as the transmission 100 changes gears, i.e. first to second gear. This results from a drop in N.sub.e curve 2994, making for rougher control but less shift energy which is calculated as described above. Thus, a drop in fluid pressure of the oncoming or apply clutch and N.sub.t indicate a lower shift energy.
The present invention has been described in an illustrative manner. It is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation.
Obviously, many modifications and variations are possible in light of the above teachings. Therefore, the subject invention may be practiced otherwise than as specifically described.
Claims
What is claimed is:
1. In a vehicle having an engine and throttle means and a transmission system including an input member, torque converter assembly transmitting torque between the engine and the input member, an output member, a gear assembly for changing the ratio of torque between the input member and the output member, a plurality of friction elements for shifting the gear assembly, a fluid actuating device being movable to engage or disengage at least one friction element, at least one solenoid-actuated valve for directing fluid flow between a fluid source and the fluid actuating device for moving the fluid actuating device, a plurality of sensors for providing signals indicative of measurement data, an engine controller and transmission controller having memory for processing and storing the signals and predetermined values and providing output signals, a method of controlling engine torque from a vehicle engine to an electronically controlled transmission in response to a launch or break-away condition of the transmission, said method comprising the steps of: sensing a speed of the engine; sensing a speed of the output member; saving in memory of an engine controller a normal spark advance setting; determining whether predetermined conditions are right for launch spark control to control engine speed directly; selecting a desired maximum engine speed based on the output speed if the conditions are right for launch spark control; calculating an error term equal to the difference between the actual engine speed and a desired maximum engine speed; and driving the error term to zero by adjusting the normal spark advance setting saved in memory based on the error term.
2. A method as set forth in claim 1 including the step of: determining whether the launch spark control is just finishing if the predetermined conditions are not right for launch spark control; and returning the spark advance to the normal spark advance setting saved in memory if the launch spark control is just finishing.
3. A method as set forth in claim 1 including the steps of determining whether a control signal has been acknowledged by the engine controller from a transmission controller; acknowledge receipt of the control signal by the engine controller to the transmission controller if the engine controller has not yet acknowledged receipt of the control signal.
4. In a vehicle having an engine and throttle means and a transmission system including an input member, torque converter assembly transmitting torque between the engine and the input member, an output member, a gear assembly for changing the ratio of torque between the input member and the output member, a plurality of friction elements for shifting the gear assembly, a fluid actuating device being movable to engage or disengage at least one friction element, at least one solenoid-actuated valve for directing fluid flow between a fluid source and the fluid actuating device for moving the fluid actuating device, a plurality of sensors for providing signals indicative of measurement data, an engine controller and transmission controller having memory for processing and storing the signals and predetermined values and providing output signals, a method of controlling engine torque from a vehicle engine to an electronically controlled transmission in response to a launch or break-away condition of the transmission, said method comprising the steps of: sensing a speed of the engine; sensing a speed of the output member; saving in memory of an engine controller a normal spark advance setting; determining whether a control signal has been acknowledged by the engine controller from a transmission controller; acknowledging receipt of the control signal by the engine controller to the transmission controller if the engine controller has not yet acknowledged receipt of the control signal; determining whether predetermined conditions are right for launch spark control to control engine speed directly; selecting a desired maximum engine speed based on the output speed of the transmission if the conditions are right for launch spark control; calculating an error term equal to the difference between the actual engine speed and a desired maximum engine speed; driving the error term to zero by adjusting the spark advance based on the error term; determining whether the launch spark control is just finishing if the predetermined conditions are not right for launch spark control; and returning the spark advance to the normal spark advance setting saved i memory if the launch control is just finishing.
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- M. Suga et al., "The Control of the Lockup Clutch Used in the Microprocessor Controlled Automatic Transmission," 1 Mech. E. (1985).