GB2151048A - Power train control method with selectable modes - Google Patents

Abstract

A method of controlling a power train of an automotive vehicle is disclosed which comprises adjusting data on which the engine operates and data on which the transmission operates to those required for a mode instructed by a driver through a data input device, and controlling the engine and the transmission on said adjusted data. <IMAGE>

Description

SPECIFICATION Power train control method with selectable modes BACKGROUND OF THE INVENTION The present invention relates to a method of controlling a power train of an automotive vehicle. The term "power train" is used herein to mean a power generating and delivery system which includes an engine and a transmission.

The power train of this kind is used for example as a drive system of an automotive vehicle. Until recently, it has been the common practice in controlling the power train to control an engine in a discrete manner from controlling a transmission as reported for example in an SAE technical paper 830423 published by Society of Automotive Engineering (SAE). In controlling an engine, an engine controller detects data from various portions of the engine and adjusts a fuel supply, an ignition timing, an EGR flow rate and an intake air flow rate to optimal values resulting from computations on the detected data. In controlling a transmission, a transmission controller detects an engine load and a vehicle speed, and decides a gear position to be established in the transmission and performs a lock-up control based on the result of computations on the detected data.

One of great tasks now to be tackled by the automotive manufactures is to enhance fuel economy and power performance. However, there have been limits and no satisfactory measures have been proposed to solve the task. One measure, although not satisfactory, is to allow a driver to switch the operating characteristics of a transmission between a fuel economy emphasized mode, a power performance emphasized mode and a standard or normal mode which is situated between the former two.

According to this measure, a transmission controller is caused to decide a gear position and carry out a lock-up control in the transmission in accordance with the selectable mode instructed by the driver. However, this measure poses a problem that a sufficiently enhanced fuel economy is not attained during the fuel economy emphasized mode and a sufficiently high power performance is not attained in the power performance emphasized mode because, since the engine and the transmission are controlled by different controllers, respectively, in a discrete manner, the operating characteristics of the engine cannot always adjust to those required for the selectable mode instructed by the driver and thus the power train as a whole cannot adjust satisfactorily to the mode instructed by the driver.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of controlling a power train of an automotive vehicle wherein the power train as a whole can adjust sufficiently well to a mode instructed by a driver such that, for example, sufficiently good fuel economy is given during a fuel economy emphasized mode and a sufficiently high power performance is given during a power performance emphasized mode.

According to the present invention, there is provided a method of controlling a power train of an automotive vehicle having a data input device operable to instruct one of a plurality of selectable modes, the power train including an engine and a transmission, the method comprising: generating a mode signal indicative of that one of the plurality of selectable modes which is instructed by the input device; adjusting data on which the engine operates and data on which the transmission operates to those required for the mode indicated by the mode signal; and controlling the engine and the transmission on the data adjusted to the mode indicated by the mode signal.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a plan view of an automotive vehicle illustrating a control system for carrying out a method according to the present invention; Figure 2 is a block diagram illustrating a control unit with its various input and output signals; Figure 3 is a detailed block diagram of the control unit; Figure 4 illustrates a control concept carried out by the control unit; Figures 5(A) and 5(B), when combined, illustrate in detail the control relationship among programs stored in the control unit; Figure 6 shows how an output torque and a fuel consumption rate of an engine vary against a variation in air fuel ratio; Figure 7 shows how the output torque and the fuel consumption rate of the engine vary against a variation in EGR rate;; Figures 8(a), 8(b) and 8(c) show optimal shift patterns for an economy mode, a normal mode and a powerful mode, respectively; and Figure 9 show optimal lock-up ranges for the economy mode, the normal mode and the powerful mode, respectively.

DETAILED DESCRIPTION OF THE INVEN TION Hereinafter, the present invention is described in detailed based on an illustrated embodiment.

Referring to Fig. 1, there is shown one example of a control system for carrying out a method according to the present invention together with a power train of an automotive vehicle which is to be controlled. In the Figure, 1 L, 1 R designate left and right front wheels, respectively, 2L, 2R designate left and right rear wheels, 3 designates an engine, 4 designates a transmission (automatic transmission), 5 designates a propeller shaft, 7 designates a differential gear, 8L, 8R designate left and right rear axles. The front wheels 1L, 1 R designate change direction wheels which are controlled by a steering wheel 9 to change direction of the automotive vehicle.

The rear wheels 2L, 2R are driving wheels of the automotive vehicle which receive the output of the engine 3 that is delivered via the transmission 4, propeller shaft 5, differential gear 7 and axles 8L, 8R.

The start, operation and stop of the engine 3 is controlled by an ignition switch 10. The engine 3 can increase its output as the accelerator pedal 11 is depressed. The output of the engine 3 is delivered in the above mentioned delivery path to the rear wheels 2L, 2R, enabling the vehicle to run. The vehicle can be stopped by depressing a brake pedal 12 and parked by manipulating a parking brake 13.

The transmission 4, which forms together with the engine 3 a power train to be controlled by the method according to the present invention, is rendered to establish a selected power delivery path in response to a manipulated position assumed by a select lever 14, such as a parking (P) range, a reverse (R) range, a neutral (N) range, a forward automatic drive (D) range, a manual second (II) brake range or a manual first (I) brake range and delivers the power from the engine 3 to the propeller shaft 5 with a selected gear position in a selected one of the drive ranges R, D, II and I.

The power train control system for carrying out the method according to the present invention comprises a control unit 1000 which is common to the engine 3 and the transmission 4. This control unit is always supplied via an electric path 1 6 with an electric power which serves as a direct continuously connected electric power source from a vehicle battery 1 5 and it operates on an electric power from the vehicle battery 1 5 which is supplied thereto as a main power source via a power source relay 1 7 that is closed when the ignition switch 10 is turned ON.Although they are described later, those signals are fed to the control unit 1000 which are a signal from the ignition switch 10 via an electric path 18, a signal from the accelerator pedal 11 via an electric path 19, a signal from the brake pedal 1 2 via an electric path 20, a signal from the parking brake lever 1 3 via an electric path 21, a signal from the select lever 14 via an electric path 22, signals indicative of a crank angle of the engine 3, a crankshaft torque, an intake air flow rate and a temperature via a wire harness 23, and signals indicative of an output shaft revolution speed of the transmission 4 and an output shaft torque thereof via a wire harness 24.Based on these input signals arithmetic operations are performed and the results are fed via the wire harnesses 23, 24 to the engine 3 and the transmission 4, respectively, thereby to control them. The control unit 1000 is also supplied via an electric path 26 with data input signals from a data input device 25 manually operable by a driver, alters its operation mode depending on these data input signals and feeds various kinds of data via an electric path 27 to a display 28 where the data is displayed.

Referring to Fig. 2, these input and output signals to and from the control unit 1000 are described in detail one after another. Among the input signals, an ignition switch signal 101 is indicative of which one of operation positions the ignition switch 10 assumes including a LOCK position, an OFF position, an ACCESSORY position, an ON position and a START position, and it is fed to the control unit 1000 via the electric path 1 8. Since the functions when the ignition switch 10 assumes these operation positions are well know, the description is omitted. A select signal 102 is indicative of which one of the before mentioned drive ranges P, R, N, D, II, I is selected via the electric path 28.An accelerator signal 103 which is a voltage signal variable in proportion to the depression degree of the accelerator pedal 11 is obtained by a potentiometer and fed to the control unit 1000 via the electric path 19. A brake signal 104 which is a voltage signal variable in proportion to the depression degree of the brake pedal 1 2 is obtained by a potentiometer and the like and fed to the control unit 1000 via the electric path 20. A parking brake signal 105 is obtained by a potentiometer and the like that is movable with the parking brake lever 13, which signal is a voltage signal variable in proportion to an operating position of the parking brake lever 1 3 and fed to the control unit 1000 via the electric path 21.

Instead, the brake signal 104 and the parking brake signal 105 may be obtained by pressure sensors, each responsive to a bias force (a braking force) of a brake element. The signals 103, 104 and 105, although they were described previously as analog signals, may take the digital form by using encoders and the like.

A data input signal 106 is a signal from a key board of the data input device 25 or a switch and fed to the control unit 1000 via the electric path 26. The data input signal 106 specifies one of operation modes of the control unit 1000, for example a standard mode (a normal mode) or a power perform ance emphasized mode (a powerful mode) or a fuel economy emphasized mode (an eco nomy mode). Such -data input signal 106 is found in Laid-open Japanese Patent Application 58-13140. The main power source 107 is fed to the control unit 1000 via the power source relay 1 7 from the vehicle battery 1 5.

The continuously connected power source 108 is always fed to the control unit 1000 via the electric path 1 6 from the battery 1 5.

A crank angle signal 1 20 is a pulse signal which is generated each time the engine crankshaft has turned through a predetermined angle, which signal is fed to the control unit 1000 via the wire harness 23. This signal is generated by a phtoelectric detector which detects a light passing through a slit plate, i.e., a disc rotatabie with the crankshaft and formed with equiangularly distant slits. A crankshaft torque signal 121 is a voltage signal variable in proportion to the torque impressed on the crankshaft, the torque being detected using the piezoelectric effect. This signal is fed to the control unit 1000 via the wire harness 23. This signal 121 can be obtained by a torque sensor which is described in Laid-open Japanese Patent Application 53-12447.The air flow signal 122 is a signal variable in inverse proportion to the intake air flow rate admitted to the engine, and it is fed to the control unit 1000 via the wire harness 32. This signal is obtained by an air flow meter usually used in a fuel injection type engine. An engine temperature signal 1 23 is a signal variable in proportion to a coolant temperature of the engine 3, which signal is fed to the control unit 1000 via the wire harness 23. This signal is obtained by a thermistor which is sensitive to the temperature of an engine coolant.

All of the above mentioned input signals except the crankshaft torque signal 1 21 can be easily obtained in the manner as described in Laid-open Japanese Patent Application 57-185501.

An output shaft revolution speed signal 1 40 is a signal variable in proportion to the revolution speed of the output shaft of the transmission 4, which signal is fed to the control unit 1000 via a wire harness 24. This signal can be obtained by computing on a cycle or a frequency of a pulse signal that is generated by a similar means used to generate the crank angle signal 1 20. The output torque signal 141 is a voltage signal which is proportional to the output shaft torque of the transmission 4, which signal is fed to the control unit 1000 via the wire harness 24. This signal can be generated by a similar torque sensor used to generate the crankshaft torque signal 1 21.

Hereinafter, output signals are described.

The power source relay control signal 201 is provided to effect ON/OFF control of the power source relay 1 7 such that when the engine is in operation where the ignition switch 10 is placed to ON or START position, the power source relay 1 7 is turned ON, connecting the main power source 107 from the battery 1 5 via this power source relay 1 7 to the control unit 1000, and the power source relay 1 7 is kept closed even after the ignition switch 10 has been turned OFF until saving of the data is completed, keeping the connection of the main power source 107 to the control unit 1000.The data output signal 202 is delivered via the electric path 27 to the display 28, causing same to display a reduction ratio established in the transmission 4, a range selected by the select lever 14, and a result of diagnosis of the power train control system. One example of this data output signal 202 is described in Laid-open Japanese Patent Application 58-13140 where the data input signal 106 is also described.

An air flow control signal 220 contains an instruction that is responsive to the accelerator signal 103 and is supplied via the wire harness 23 to the well known throttle actuator, such as disclosed in Published Japanese Application 58-25853, mounted to the engine 3, causing the throttle actuator to adjust the throttle opening degree to a level corresponding to the depression degree information (accelerator signal 103) of the accelerator pedal 11, thereby to adjust the air flow rate admitted to the engine 3 to a value corresponding to the air flow control signal 220.A response time between input of the accelerator signal and output of the air flow control signal 220 is adjusted such that the rate of change in throttle opening degree is normal during the before mentioned normal mode and thus the engine 3 can accelerate or decelerate normally in response to the depression of the accelerator pedal. The response time is set such that the rate of change in the throttle opening degree is slow during the economy mode so as to reduce the fuel consumption. To this end, the above mentioned basic response time is corrected by differentiation after putting a delay element, i.e., 1 /(1 + Ts) for example, between input of the accelerator signal 103 and output of the air flow control signal 220.

During the powerful mode, the response time is set such that the rate of change in the throttle opening degree is rapid and the engine respond quickly so as to enhance power performance. To this end, the basic response time is corrected by differentiation after putting an advance element, i.e., 1 + Ts, for example, between input of the accelerator signal 103 and output of the air flow control signal 220. For idle operation, the air flow control signal 220 adjusts the throttle opening degree via the throttle actuator so as to keep the idle revolution speed constant in a manner as described in Laid-open Japanese Patent Application 55-160137.When the data input signal 106 instructs a constant speed crusing, the air flow control signal 220 adjusts via the throttle actuator the throttle opening degree on a result of comparison of a measured vehicle speed with an instructed vehicle value (a feedback control) in order to cause the vehicle to run at the instructed vehicle speed value.

The fuel injection control signal 221 is a pulse signal which controls the opening time of a fuel injection valve mounted to the engine, which signal is delivered from the control unti 1000 via the wire harness 23. As described in Laid-open Japanese Patent Application 55-125334, a basic control concept is that the above mentioned valve opening duration (fuel injection amount), which is proportional to the intake air flow rate, is computed on the crank angle signal 120 and the air flow signal 122, and then this result is corrected in various manners, and the result is output in terms of the fuel injection control signal 221 in synchronous with the operation of the engine 3. During the normal mode, the fuel injection amount related information to be carried by the fuel injection control signal 221 is such as to attain an air fuel ratio which is indicated by AN in Fig. 6.During the powerful mode and the economy mode, the information to be carried by the fuel injection control signal 221 differs from mode to mode which will be described hereinafter. This is described referring to Fig. 6 which shows how output torque T,A and fuel consumption rate FCA vary against variation in air fuel ratio (A/F). During the powerful mode, the fuel injection amount carried by the fuel injection control signal 221 provides an air fuel ratio as indicated by Ap at which the output torque TRA is maximum. The fuel injection control signal 221 for this mode is obtained by multiplying a certain value with the basic fuel injection valve opening duration or adding a certain value to the basic fuel injection valve opening duration.During the economy mode, the fuel injection amount carried by the fuel injection control signal 221 provides an air fuel ratio indicated by AE at which the fuel consumption rate FCA is minimum. The fuel injection control signal 221 for this mode is given by reducing the basic fuel injection valve opening duration with correction coefficient.

As described in Laid-open Japanese Patent Applications 57-185501 and 54-58165, the ignition control signal 222 is a signal which controls the ignition energy and the ignition timing by controlling in synchronous with the crank angle signal 120, the time during which current is allowed to pass through a primary coil of an ignition coil provided to the engine 3 and the termination timing of the current supply. This signal is delivered from the control unit 1000 via the wire harness 23. The ignition energy is controlled such that it is kept unchanged with a variation in the engine revolution speed (the cycle or the frequency of the crank angle signal 120) and a variation in the voltage of the battery 15, and the ignition timing is determined on the engine revolution speed and crankshaft torque taking the output torque, fuel economy and exhaust gases into account.Referring to how the ignition timing is determined, since the ignition timing is set to an optimal point where the torque is maximum and the fuel consumption rate is minimum, this means that it is not necessary to alter the ignition timing even if the mode switches. However, the proper ignition timing where the torque is maximum and the fuel consumption rate is minimum shifts also in response to the before mentioned alteration of the fuel injection control signal 221 and the air flow control signal, and an alteration, which will be later described, of an EGR control signal 223, a reduction ratio control signal 240, and a lock-up control signal 241 as a result of mode change. Thus, it is necessary that the ignition timing be altered accordingly.To this end, one measure is to prepare a plurality of tables of the ignition timings corresponding in number to the number of selectable modes and one of the tables is selected and used which corresponds to the instructed selectable mode in computing ignition timing which is to be carried by the ignition control signal 222. Alternatively, the basic ignition timing values in a table are uniformly corrected in resonse to a mode instructed so as to provide the proper ignition timing signal for the mode which is to be carried by the ignition control signal 222.

As described in Laid-open Japanese Patent Application 55-32918, the EGR control signal 223 carries an information related to the opening degree of an exhaust gas recirculation valve (exhaust gas recirculation rate), which signal is delivered from the control unit 1000 via the wire harness 23. During the above mentioned normal mode, the above mentioned valve opening degree, i.e., an exhaust gas recirculation amount (an exhaust gas recirculation rate), is determined on the engine revolution speed and crankshaft torquf taking into account the exhaust gases and the fuel economy such that an exhaust gas recirculation rate as indicated by EN as shown in Fig. 7 is given. The information to be carried by the EGR control signal 223 differs from the powerful mode to the economy mode, as will be described hereinafter. This is described referring to Fig. 7 which illustrates how the output torque Trp of the engine and the fuel consumption rate FCE thereof vary against the variation in the exhaust gas recirculation (EGR) rate. During the powerful mode, the information to be carried by the EGR control signal 223 provides an EGR rate Ep where the torque TrE is maximum, whereas during the economy mode, it provides an EGR rate where the fuel consumption rate FCE is minimum. The alteration of the EGR control signal 223 responsive to a switching between the modes may be carried out by using a plurality of tables corresponding in number to the modes.

The reduction ratio control signal 240 carries an information related to a reduction ratio (gear position) to be established in the transmission 4 and delivered from the control unit 1000 via the wire harness 24. The reduction ratio is determined on the input torque to the transmission (the engine crankshaft torque), i.e., the signal 121, or the engine load detected with the signal (accelerator signal 103, intake air flow signal 122) corresponding to the signal 121, and the vehicle speed (output shaft revolution speed signal 140) taking the driving torque, fuel economy vibrations into account. As described in Laid-open Japanese Patent Applications 57-47056, 56-24255 and 56-24256, the reduction ratio control signal 240 controls various kinds of shift solenoids of the transmission 4 in order to establish the desired gear position.Describing to the detail, the information to be carried by the reduction ratio control signal 240 is determined on various gear position tables (gear shift patterns) as shown in Figs. 8(a), 8(b) and 8(c).

The table as illustrated in Fig. 8(a) is selected to be used during the economy mode, the table as illustrated in Fig. 8(b) during the normal mode, and the table as illustrated in Fig. 8(c) during the powerful mode. As will be understood from the shift pattern schedules shown in these Figures, shift points on upper portions of the shift lines 1-2, 2-3, 3-2 and 2-1 are moved toward high vehicle speed side from Fig. 8(a) toward Fig. 8(c) via Fig.

8(b) so that there is a growing tendency that a low gear position is maintained till higher vehicle speed is attained. Thus the shift pattern in Fig. 8(a) is for the fuel economy emphasized mode, the shift pattern as illustrated in Fig. 8(c) for power performance emphasized and the shift pattern shown in Fig. 8(b) for the mode having an intermediate character between both of them.

The lock-up control signal 241, which controls connection and disconnection between the input and output elements of the torque converter in the transmission 4, is delivered from the control unit 1000 via the wire harness 24. As described in Laid-open Japanese Patent Applications 56-24255, 56-24256 and 57-33253, the lock-up control signal 241 is determined on the crankshaft torque (signal 121) and the vehicle speed (signal 140) taking the fuel economy and vibrations into account.As shown in Fig. 9 for example, during the normal mode, the lock-up of the torque converter owing to the above connection is rendered to take place in an operating range enclosed by a fully drawn line LN, the lock-up is render to take place in a lock-up range enclosed by a broken line Lp during powerful mode, and the lock-up is rendered to take place in a lock-up range enclosed by a two-dot chain line LE during economy mode.

Describing these lock-up ranges, the lock-up range for the normal mode is a range where there occur no substantial vibrations at acceleration and deceleration during the normal mode, the lock-up range for the powerful mode is a range which although it is narrow as compared to the lock-up range for the normal mode, in order to utilize the torque multiplication function for acceleration, extends to cover area where the lock-up is required for effective engine braking and the lock-up range for economy mode is a range which is sufficiently wide to the extent that no substantial vibrations take place at acceleration and deceleration.The lock-up control signal 241 which is determined in the above manner controls a relative rotation (a slip) between the input and output elements by controlling the above mentioned connection and disconnection within the torque converter, thus allowing the torque converter to operate in its most proper state for the selectable mode instructed.

Hereinafter, referring to Fig. 3, a practical example of the architecture of the control unit 1000 is described.

In this Figure, 1100 designates a signal shaper circuit which forms an input portion of the before mentioned various input signals 101 to 107, 120 to 123, 140, 141. It functions to eliminate noise of these input signals and absorbs surge thereof so as to prevent malfunction of the control unit 1000 caused by the noise and destruction thereof caused by the surge, and it also performs amplification of the various input signals and conversion thereof so as to shape these signals, thereby to allow an input interface circuit 1 200 to perform an accurate operation.The input interface circuit 1 200 effects analog to digital (A/D) conversion of the various input signals which have been shaped by the circuit 1100, counts pulses for a predetermined time, converts these signals into digital coded signals which can be read as input data by a centeral processing unit (CPU) 1 300 and stores them in the corresponding internal registers. The CPU 1 300 operates in synchronous with a clock signal generated based on an oscillating signal generated by a crystal oscillator 1310.The CPU 1300 is connected via a bus 1 320 to the input interface circuit 1200, a memory 1400, an output interface circuit 1 500 and an operation timer circuit 1 350. When, in operation, it executes a control program stored in a mask ROM 1410 and a PROM 1420 of the memory 1400, the CPU 1 300 reads various input data from the corresponding registers within the input interface circuit 1200, performs arithmetic operations on this input data to generate various output data, delivers this output data to the corresponding registers within the output interface circuit 1 500 with a predetermined timing.

The memory 1400 is a storage device including in addition to the above mentioned mask ROM 1410 and the PROM 1420, a RAM 1430 and a storage holding memory 1440.

The mask ROM 1410 is used to permanently store control programs and data used in executing the programs. The PROM 1 420 is used to permanently store vehicle speed values, control programs which are subject to alteration depending upon the engine 3 and the transmission in terms of their kinds, which data are written into the PROM 1420 when the latter is installed in the control system.

The RAM 1430 is a random access memory which is able to read and write data and used to temporarily store intermediate data resulting from arithmetic operations performed by the CPU 1300, and temporarily store the final data resulting from the arithmetic operations performed by the CPU 1300, and temporarily store the final data resulting from the arithmetic operations executed by the CPU 1 300 before they are delivered to the output interface circuit 1 500. The storage contents immediately disappear when the main power source 107 is disconnected when the ignition switch 10 is turned OFF.The storage holding memory 1440 is used to store such data as those intermediate data and final data of the arithmetic operations executed by the CPU 1 300 which are to be held even after the automotive vehicle stops its dperation, and it can hold the above mentioned data owing to the continuously connected power source 108 even after the main power source 107 is disconnected when the ignition switch 10 is turned OFF.

The operation timer circuit 1 350 is provided to reinforce the facilities of the CPU 1 300. It comprises a multiplication circuit for speeding processing in the CPU 1300, an interval timer for causing an interrupt signal upon elapse of a predetermined time and a free-running counter used for measuring a time elapsed in the CPU 1 300 for effecting a shift from a predetermined event to a next event and measuring the instant when the event takes place. The output interface circuit 1 500 stores the output data from the CPU 1 300 into the corresponding internal registers.It converts this data into pulse signals or into switching signals which go into "1" or "0" before delivering them to a drive circuit 1 600. The drive circuit 1 600 is a power amplifier circuit which performs voltage or current amplification of the signals from the output interface circuit 1 500 so as to produce the before mentioned various output signals 201, 202, 220 to 223,240,241.

Designated by 1 700 is a backup circuit which is activated by a monitor signal 1 710 caused by monitoring the signals produced by the drive circuit 1 600. When it is activated indicating that the CPU 1 300 or the memory 1400 has failed to normally operate due to trouble, the backup circuit 1 700 receives a portion of the signals from the signal shaper circuit 1100 and generates output signals which enables the engine 3 and the transmission 4 to continue to operate such that the automotive vehicle can continue its running and also a switching signal 1 730 informing the occurrence of a trouble.The signals 1 720 and 1 730 are supplied to a switching circuit 1750, causing the switching circuit 1 750 to cut off signals from the output interface circuit 1 500 and supply in lieu thereof the signals 1 720 from the backup circuit 1 700 to the drive circuit 1600, thereby to enable the automotive vehicle to safely run to an auto repair shop.

Designated by 1 800 is a power source circuit which is supplied with the main power source 107 and the continuously connected power source 108. The power source circuit 1800 supplies a constant voltage 1810 of 5 V from the main power source 107 to the input interface circuit 1 200, CPU 1 300, memory 1400, output interface circuit 1 500 and operation timer circuit 1 350. It also sup plies another constant voltage 1 820 of 5 V to the backup circuit 1700, a signal 1 830 indicative of "ON" or "OFF" state of the ignition switch 10 to the input interface circuit 1200, a reset signal 1 840 and a stop signal 1 850 for stopping the operation of the CPU 1 300 to the bus 1320, a constant voltage 1860 for the internal A/D converter to the input interface circuit 1200, and a main voltage 1 870 to the signal shaper circuit 1100.

drive circuit 1 600 and switching circuit 1 750.

Besides, the power source circuit 1 800 sup plies a constant voltage 1 800 of 5 V from the continuously connected power source 108 to the storage holding memory 1440 for enabling same to operate even after the ignition switch 10 has been turned OFF.

Referring to Fig. 4, control programs for the control unit of the above construction and processing thereby are generally described.

The control programs comprise and can be generally divided into four groups, i.e., an initialize program 3000, a background pro gram group 4000, an interrupt handling pro gram group 5000 and a subprogram group 3100.

When the ignition switch 10 is turned ON and thus the main power source 107 is ,Eonnected, the reset signal 1 840 is generated by the power source circuit 1800, causing the control programs to be initiated to run from a RESET shown in Fig. 4. First, the initialize program 3000 is caused to run so as to set initial values in the RAM 1430, input and output interface circuits 1200, 1 500 (initialization). After the initialization, the execution of the background program 4000 is caused and repeated. This program group comprises a plurality of programs listed in the correspond ing items and these listed programs are caused to run sequentially in the order of arrangement of the items.Entry of an interruption signal causes an interruption if it occurs during the execution of the background program 4000, causing switching along a path as indicated by a broken arrow (1) to the interrupt handling program group 5000 which begins with INTERRUPT. (Although not so in this embodiment, the interruption of the initialize program 3000 may be possible if so desired.) After identifying the interrupt signal, the program group 5000 selects one of a plurality of programs therein in response to the identified result and causes the selected program to run. After execution of the selected program, switching back to the interrupted portion of the background program group 4000 occurs along a path as indicated by a broken arrow (2), thus causing it to rerun.

If another new interruption signal enters during the execution of the interrupt handling program group 5000, switching to INTER RUPT along a path as indicated by a broken arrow (3) occurs, and a comparison is made between the interrupt handling program under execution and another interrupt handling program corresponding to the new interrupt signal so as to decide which one should be executed. In response to the decision result, one possibility is that the new interrupt signal causes switching to the new program corresponding to the new interrupt signal along a path as indicated by a broken line arrow (4) and after execution of this new program, the interrupted program is caused to rerun.

Another possibility is that after executing the program under execution, switching occurs to the new program corresponding to the new interrupt signal along a path as indicated by a broken line arrow (5).

Among the plurality of programs belonging to the background program group 4000 and the plurality of programs belonging to the interrupt handling program group 5000, those which are frequently used are labelled as subprogram group 3100. When, during execution of a program belonging to the background program group 4000 or the interrupt handling program group 5000, a need for the above mentioned subprogram arises, switching to the subprogram 3100 occurs along a path indicated by a broken line arrow (6) or (8) or (10), causing the needed program therein to run. After the execution of this program needed, switching back to the interrupted program occurs along a path as indicated by a broken line arrow (7) or (9) or (11), causing it to rerun.Although it is possible to interrupt a subprogram under execution to cause another subprogram to be executed or to cause the interrupt handling program group 5000, this is not illustrated here in this Figure for the sake of avoiding complexity.

If an interruption of a program causes a problem, entry of such interruption can be prohibited before the execution of the program till the end of the execution.

The detail of the control programs is illustrated in Fig. 5 which is hereinafter used in detail description of the control program.

When the ignition switch 10 is turned ON and the main power source 107 is connected, the reset signal 1 840 is generated, causing the initialize program 3000 to run from a specified address called "reset vector address." The initialize program 3000 is executed to prepare arrangements for execution of various programs which follow by setting initial values in the CPU 1300, RAM 1430, input/output interface circuits 1200, 1 500 (initializing). With this program, all of the locations in the RAM to be used by this microcomputer are cleared and all of the instructions necessary for operation of the input and output interface circuits 1200, 1 500 and the operation timer circuit 1350, and the operation thereof is initiated.These instructions include an instruction to release an instruction mask for handling interruption signals, an instruction to set frequency of timer interruption, an instruction to set a measuring time for measuring each of various revolution speeds and vehicle speed, an instruction to set a constant or constants relating to each of output signal for one of various controls, and an instruction to set an initial state of each of the outputs. After initialization, an instruction authorizing an interruption is issued to the CPU 1300.

The execution of the background program 4000 continues during the normal operation of the CPU 1300, i.e., the operation of the CPU 1 300 when there is no interruption requirement. With the background program group 4000, jobs which require less emergency are executed when the CPU 1 300 is free, such as jobs requiring long operation time and jobs computing steady-state control constants. The background program group 4000 includes a steady-state control data computation program 4100, a low speed correction data computation program 4200, a learning control program 4300 and a check program 4400. These programs are executed sequentially in a predetermined order such that the top program is executed again after the execution of the bottom program and this cycle is repeated.In this manner, the control unit 1000 continues to generate the output signals 201, 202, 220 to 223, 240, 241 during the steady state operation of the automotive vehicle. The signals 220 to 223 are generated to control the engine 3 and the signals 240, 241 are generated for controlling the transmission 4 so as to adjust the engine 3 and the transmission 4 to the steady state operation of the automotive vehicle. The signal 201 is generated to hold the power source relay 1 7 in ON state so as to keep connection to the main power source 107 and the signal 202 is generated to cause the display 28 to display necessary information.

The interrupt handling program group 5000 is caused to run by an interruption of the execution of the background program group 4000 (or the initialize program 3000 if desired). The interrupt handling program group 5000 comprises a timer interrupt handling program 5100 (5110, 5120, 5130) an angle coincident interrupt handling program 5200 (5210), an A/D conversion handling program 5300 (5310), an external interruption (or a privileged interruption) handling program 5400 (5410), a revolution measurement end interruption handling program 5500 (5510), an external pulse interruption handling program 5600, an overflow interruption handling program 5700, and a data receive interruption handling program 5800 (5810) which are caused to be executed by the corresponding interruptions.It also includes a group of priority-basis-executing programs which are executed on priority which is decided by a job execution priority decision program 6000, which group of programs includes an acceleration control program 6100, a deceleration control program 6200, a start control program 6300, a shift control program 6400, a lock-up control program 6500, an engine stall prevention program 6600, a time synchronizing control program 6700, an angle synchronizing control program 6750 and a data input/output program 6800.

Describing these programs subsequently, entry of a timer interrupt causes a selection of the timer interruption program 5100 where the A/D conversion activation program 5120 is executed. This program 5120 manages the measurement of analog input signals by activating the A/D converter and switching the multiplexer in effecting the A/D conversion of the analog input signals for use in the subsequent control by switching the multiplexer.

Then, the clock signal output program 5110 is executed. This program generates a clock signal with a predetermined cycle which indicates normal operation of each of the CPU 1300, memory 1400, output interface circuit 1500, and thus informs the operating state of each of them. Finally, time synchronizing job activation reservation program 51 30 is executed and places an activation of a time synchronizing control program 6700 (i.e., an activation requirement of this program) in the job execution priority program 6000. The time synchronizing control program processes jobs to be carried out in synchronous with a cycle of a cyle of the clock signal.

Entry of an angle coincidence interruption (i.e., an interruption which occurs whenever the engine assumes a predetermined crank angle) causes the selection of the angle coincident interruption handling program 5200.

This program causes an angle synchronizing job activation reservation program 5210 to place the activation (i.e., the activation requirement) of a job handling program (an angle synchronizing control program 6750) which needs to be processed in synchronous with the revolution of the engine on the job execution priority decision program 6000.

Entry of an A/D BUSSY flag check interruption causes a selection of the A/D conversion end handling program 5300 where a decision is made on checking the A/D BUSSY flag whether or not the A/D conversion has ended. When it has ended, an operation state dependent job activation reservation program 5310 instructs the storage of A/D converted data into the corresponding location in the RAM 1 430 in accordance with A/D conversion channel data, and although this will be specifically described later, it decides the operation state of the automotive vehicle on a time series data of the A/D converted values relating to the acceleration signal 103 and places the activation requirement of an appropriate operation state dependent job handling program for this operating state (such as the acceleration control program, deceleration control program and start control program) on the job execution priority decision program 6000.

Entry of an external interruption causes a selection of the external interruption handling program 5400. The external interruption, i.e., an emergency interruption, is generated when the main power source 107 is disconnected.

The program 5400 is selected by entry of this interruption. This program 5400 causes the execution of a power off data holding program 5410 where data to be preserved for learning control and the like are moved from the RAM 1430 to the storage holding memory 1440.

Entry of engine revolution measurement end interruption causes a selection of the revolution measurement end interruption handling program 5500. According to this program, the activation of an engine stall decision RPM computation program 5510 is caused. This program 5510, where an engine revoluton speed is read to decide whether or not the engine may stall, places an activation requirement of an engine stall prevention control program 6600 on the job execution priority program 6000 when the engine may stall.

The external pulses interruption handling program 5600 is caused to be executed upon manipulation of a key on a key board or entry of a pulse signal from an external device. This program causes execution of a corresponding control to the pulse signal. The overflow interruption handling program 5700 is caused to be executed by entry of an interruption which is generated upon overflow of the timer and performs a predetermined process.

The data receive interruption handling program 5800 is caused to be executed by entry of a data receive interruption and causes the execution of the received data handling job activation program 5810. With the execution of this program 5810, the received data is stored at a predetermined location in the RAM 1430 and then the activation of the received data handling job (i.e., the requirement for the activation thereof) is placed on the job execution priority program 6000.

The job execution priority decision program 6000 receives the various activation requirements of job handling programs selected by the above mentioned interrupt handling programs and causes the contents of the corresponding bits (flags) in the RAM 1430 to the selected job programs to go from "0" to "1".

Since a predetermined execution priority level is originally allocated to each job program of all, the sequence of location and bit for each job program is determined in accordance with the predetermined priority level. In the case of this program, a check is made starting with the high-order bit in sequentially down to the low-order bit in a location in the RAM 1430, and when a program is reserved, this program is executed and the reservation indicator is cancelled (by resetting the flag to "O"). When the execution of this program ends, the JOB execution priority decision program 6000 is executed and a reserved program of the next lower priority level is caused to be executed and the reservation therefor is cancelled, and after the execution of all of the reserved programs has ended, switching to the background program 4000 occurs.

Hereinafter, a group of those job programs which are to be executed on the priority determined by the program 6000 are described. The acceleration control program 6100 computes output control data relating to optimal fuel injection amount, ignition timing, exhaust gas recirculation flow rate, intake air flow rate, reduction ratio and lock-up schedule for the degree of acceleration.For example, in the case of a rapid acceleration (i.e., in the case of rapid increase in the accelerator signal 1 03), they are controlled such that for increasing the output of the engine, the fuel injection amount is increased, the ignition timing is advanced, the EGR flow rate is reduced and the intake air flow rate is increased, and besides for increasing the output torque from the transmission 4, the lockup of the torque converter is released and the reduction ratio is increased.

A deceleration control program 6200 computes, at deceleration, various control output data which are optimal for the degree of deceleration, vehicle speed and engine revolution speed. At deceleration, the engine 3 is controlled such that the fuel injection amount is zero or very small and the transmission 4 is controlled such that the reduction ratio and the operating state af the torque converter cooperate with each other to provide the most appropriate deceleration feel.

The start control program 6300 computes various output data for controlling the engine 3 and the transmission 4 such that a sufficiently great starting torque is obtained at the start of the automotive vehicle without caus ingtany slip of the driving wheels 2L, 2R.

The shift control program 6400 computes various output data used for controlling the shift in the transmission 4 and the output torque and the revolution speed of the engine 3 in order to prevent substantial shocks from being transmitted to vehicle passengers during the shifting operation in the transmission 4.

The lock-up control program 6500 computes various output data for controlling lockup operation of the torque converter and the output of the engine in order to reduce shocks occurring upon lock-up operation and relesese thereof.

The engine stall prevention control program 6600 is caused to be executed when it is anticipated that the engine stall tends to occur by deciding a state of variation in the engine revolution speed during the execution of said program 551 0. It computes various control output data so as to control the engine 3 and the transmission 4 such that, for preventing the engine stall, the engine output is increased immediately and the load is decreased.

The time synchronizing control program 6700 which is reserved and executed after lapse of each cycle, updates various data and writes the control data of the preceding cycle into the output interface circuit 1 500.

The execution of an angle synchronizing program 6750, which is reserved and executed whenever the engine 3 assumes a predetermined crank angle, updates various data and writes control data into the output interface circuit 1 500.

The data input/output control program 6800, which is reserved and executed upon lapse of predetermined time or upon entry of a data receive interruption, stores the date after deciding the content thereof upon data reception, alters the state of control and outputs of the content of the data upon effecting data transmission.

The operation of the above described embodiment is described taking as a representative example the case where the driver manipulates the data input device 25 and alters the selectable instructed mode. When the mode switches, the interrupt handling program 5000 causes a data receive interruption and selects the data receive interruption program 5800. This program 5800 causes the received data handling job activation reservation program 5810 and stores the instructed mode, i.e., the normal mode or powerful mode or economy mode, into a predetermined location in the RAM 1430 and places a reservation for activation of the received data (selected mode) related job in the job execution priority decision program 6000.Upon receiving the requirement for activation of the job, the program 6000 sets a predetermined bit (flag) of a predetermined location in the RAM 1430 corresponding to this job from "0" state to "1" state. The program 6000 causes the execution of the data input/output program 6800 and at the same time reset the flag to "0" state. The data input/output program 6800 issues instructions so as to determine in the before described manner the air flow control signal 220, fuel injection control signal 221, ignition timing signal 222, EGR control signal 240 and lock-up control signal 241 which are suitable for the mode.

Subsequently, after the control has returned to the background program 4000, the steadystate control data computation program 4100, low speed correction data computation program 4200, learning program 4300 and check program 4400 are executed based on the above mentioned instructions, thus controlling the engine 3 by the signal 220 to 223 in accordance with the driver's instructions and controlling the transmission 4 by the signals 240 and 241 in accordance with the driver's instructions.

In the case the data input device 25 cannot generate the data receive interruption signal, the contents of the programs 5800 (5810) may be included into the timer interruption handling program 5100. In this case, entry of the timer interruption causes the control unit 1000 to instruct the data input device 25 to transmit a data indicative of an instructed mode. This instructed mode indicative data transmitted causes the data input/output program 6800 to run in the before mentioned manner. Although the above example has been described in connection with three different modes, i.e., the normal mode, the powerful mode and the economy mode, it ispos- sible to carry out the invention in the case where there are more than three modes.

Where there are selectable modes more than three, it is convenient to effect selection by using numerical data set by a single switch rather than the use of the corresponding num ber of switches to the modes. Besides, a change between modes may be made more smooth only with more fine fractionalization.

It is also possible to carry out continuous change between modes in response to an output generated by a potentiometer. Of course, the above mentioned change of modes has to be carried out within the con straints imposed in consideration of noise, vibrations and exhaust gas regulations.

As described above, since with the power train control method according to the present invention, not only the operating character istics of a transmission 4 but also those of an engine 3 are altered in response to a selectable mode instructed by a driver to adjust to the instructed selectable mode, the combination effect thereof causes a power train as a whole to adjust satisfactorily to the instructions by the driver, so that when fuel economy emphasized mode (economy mode) is selected, a sufficiently high enhancement of fuel economy as required is obtained, and when the power performance emphasized mode (powerful mode) is selected, a sufficiently high power performance as required is obtained, thus making it possible to control the power train as required by the driver.

Claims (2)

1. A method of controlling a power train of an automotive vehicle having a data input device operable to instruct one of a plurality of selectable modes, the power train including an engine and a transmission, the method comprising: generating a mode signal indicative of that one of the plurality of selectable modes which is instructed by the input device; adjusting data on which the engine operates and data on which the transmission operates to those required for the mode indicated by said mode signal; and controlling the engine and the transmission on said data adjusted to the mode indicated by said mode signal.

2. A method of controlling a power train of an automotive vehicle as claimed in claim 1 and substantially as hereinbefore described with reference to the accompanying drawings.