Transmission, and control system and control method for the transmission

When torque transmission through the transmitting torque variable mechanism (e.g., an assist clutch) is changed to torque transmission through a meshing gearing after the gearshift, a controlled variable per unit time when the transmitting torque variable mechanism is released is determined or varied according to the vehicle operating condition after a gearshift has been completed. A degraded gearshift feel as a result of axle vibration at the end of the gearshift can thereby be suppressed.

BACKGROUND OF THE INVENTION

The present invention relates to a control method and a control system for an automatic transmission.

A motor vehicle with a manual transmission offers better fuel economy as compared with a motor vehicle mounted with a transmission using a torque converter. It is, however, difficult in such a motor vehicle as that with the manual transmission to manipulate a clutch and an accelerator in a coordinated manner when getting the motor vehicle started. If the coordinated operations of the clutch and the accelerator do not go well when the vehicle is started, a large shock occurs as the clutch is engaged. If there is a short supply of a clutch pressure, the engine speed rises sharply, which is commonly referred to as a “revving up phenomenon.” If the clutch is quickly engaged when the engine speed is yet to reach a sufficient level, or when the vehicle is started on an uphill slope, the engine can stall.

To solve these problems, a system that automates the clutch and a gearshift using a manual transmission mechanism has been developed. The system is what is called an automated manual transmission, or automated MT.

The conventional automated MT has the disadvantage that there is an interruption of a driving torque occurring from release and engagement operations of the clutch during control for gearshifts. This can at times give passengers of the vehicle a sense of discomfort.

A vehicle provided with an automatic transmission has been proposed to avoid the torque interruption during the gearshift. A known approach to the problem is an assist clutch serving as a transmitting torque variable mechanism provided for the conventional automated MT (see, for example, Japanese Patent No. 2703169). The assist clutch provides control, during a gearshift, for synchronizing rotations and transmitting torque properly for the gearshift. In a vehicle such as that described above, an assist clutch torque release control is provided. In the assist clutch torque release control, after the gearshift to a new meshing gearing has been completed, torque transmitted by the assist clutch is reduced, while torque transmitted by the new meshing gearing after the gearshift is increased.

When the torque transmission through the assist clutch is changed to the torque transmission through the meshing gearing after the gearshift, torque vibration in a transmission output can occur due to a torque step depending on how the assist clutch is controlled. The assist clutch, on the other hand, transmits torque through slippage. This presents a durability problem arising from a quantity of heat generated.

SUMMARY OF THE INVENTION

In view of the foregoing, it is therefore an object of the present invention to suppress torque vibration occurring during a gearshift, and at the same time to extend a service life of a clutch.

To achieve the foregoing object, the present invention determines or varies a controlled variable per unit time according to a vehicle operating condition, when the transmitting torque variable mechanism is released after the gearshift has been completed.

When the torque transmission through the transmitting torque variable mechanism (e.g., an assist clutch) is changed to the torque transmission through the meshing gearing after the gearshift, torque vibration in the transmission output can occur due to a torque step depending on how the transmitting torque variable mechanism is controlled. At this time, the controlled variable may be set or varied so that the transmitting torque variable mechanism is released at a mild pace according to the vehicle operating condition. If this is done, a degraded gearshift feel as a result of axle vibration at the end of the gearshift can be suppressed.

The pace at which the transmitting torque variable mechanism is released may be increased or decreased according to a vehicle operating condition, for example, the quantity of heat generated by the transmitting torque variable mechanism. This can suppress generation of heat from the transmitting torque variable mechanism, leading to enhanced durability.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first arrangement of a motor vehicle control system according to a preferred embodiment of the present invention will be described with reference toFIG. 1.

FIG. 1is a skeleton diagram showing a first system configuration of a motor vehicle control system according to a preferred embodiment of the present invention. The system includes an engine1as a driving power source, an engine speed sensor (not shown) measuring a speed of the engine1, a device regulating an engine torque (not shown; for example, an electronic controlled throttle), and a fuel injection system (not shown) for injecting the amount of fuel corresponding to the amount of intake air. Controlling the amount of intake air, the amount of fuel, ignition timing, and the like using an engine control unit101allows the torque of the engine1to be controlled accurately. The driving power source is not limited only to a gasoline engine as in the above example. A diesel engine, a natural gas engine, an electric motor, or the like perfectly serves the purpose.

An input shaft clutch input disc2is coupled to the engine1. The torque of the engine1can be transmitted to, or shut off from, a transmission input shaft10by engaging the input shaft clutch input disc2with, or releasing the same from, an input shaft clutch output disc3. A dry type single plate clutch is generally used as an input shaft clutch. Any type of friction transmission mechanisms can still be used, including a wet type multiple disc clutch and an electromagnetic clutch. The transmission input shaft10is provided with a first drive gear4, a second drive gear5, a third drive gear6, a fourth drive gear7, a fifth drive gear8, a reverse drive gear (not shown), and a seventh drive gear201.

A hydraulically driven actuator22is used for controlling a thrust force (an input shaft clutch torque) between the input shaft clutch input disc2and the input shaft clutch output disc3. Regulating the thrust force (the input shaft clutch torque) allows an output from the engine1to be transmitted to, or shut off from, the transmission input shaft10.

The first drive gear4, the second drive gear5, the third drive gear6, the fourth drive gear7, the fifth drive gear8, and the reverse drive gear are secured in position. The seventh drive gear201, on the other hand, is rotatably mounted on the transmission input shaft10. There is also provided a sensor29for detecting the speed of the transmission input shaft10. The sensor29functions as a system for detecting an input shaft speed.

A transmission output shaft18is provided with a first driven gear12, a second driven gear13, a third driven gear14, a fourth driven gear15, a fifth driven gear16, and a reverse driven gear (not shown), rotatably mounted thereon. A seventh driven gear202is fixed onto the transmission output shaft18. The first driven gear12is in mesh with the first drive gear4. The second driven gear13is in mesh with the second drive gear5. The third driven gear14is in mesh with the third drive gear6. The fourth driven gear15is in mesh with the fourth drive gear7. The fifth driven gear16is in mesh with the fifth drive gear8. The reverse driven gear (not shown) is in mesh with the reverse drive gear through a reverse rotation gear (not shown). The seventh driven gear202is in mesh with the seventh drive gear201.

A first meshing gearing19is provided as a meshing gearing between the first driven gear12and the second driven gear13. The first meshing gearing19causes the first driven gear12to be engaged with the transmission output shaft18. Or, the first meshing gearing19causes the second driven gear13to be engaged with the transmission output shaft18.

Rotating torque transmitted from the first drive gear4or the second drive gear5to the first driven gear12or the second driven gear13is therefore transmitted to the first meshing gearing19. The rotating torque is thereby transmitted to the transmission output shaft18through the first meshing gearing19.

A second meshing gearing20is provided as a meshing gearing between the third driven gear14and the fourth driven gear15. The second meshing gearing20causes the third driven gear14to be engaged with the transmission output shaft18. Or, the second meshing gearing20causes the fourth driven gear15to be engaged with the transmission output shaft18.

Rotating torque transmitted from the third drive gear6or the fourth drive gear7to the third driven gear14or the fourth driven gear15is therefore transmitted to the second meshing gearing20. The rotating torque is thereby transmitted to the transmission output shaft18through the second meshing gearing20.

A third meshing gearing21is provided as a meshing gearing between the fifth driven gear16and the reverse driven gear (not shown). The third meshing gearing21causes the fifth driven gear16to be engaged with the transmission output shaft18. Or, the third meshing gearing21causes the reverse driven gear to be engaged with the transmission output shaft18.

Rotating torque transmitted from the fifth drive gear8or the reverse drive gear to the fifth driven gear16or the reverse driven gear is therefore transmitted to the third meshing gearing21. The rotating torque is thereby transmitted to the transmission output shaft18through the third meshing gearing21.

The meshing gearing19,20,21described above may be a constant-mesh type. The gearing may even be a clutch provided with a friction transmission mechanism that is used to accomplish rotation synchronization for meshing (what is called a synchromesh).

To transmit the rotating torque of the transmission input shaft10to the first meshing gearing19, the second meshing gearing20, or the third meshing gearing21, the following engagement must be effected. Specifically, either one of the first meshing gearing19, the second meshing gearing20, and the third meshing gearing21is moved in an axial direction of the transmission output shaft18, thereby bringing the meshing gearing into engagement with any one of the first driven gear12, the second driven gear13, the third driven gear14, the fourth driven gear15, the fifth driven gear16, and the reverse driven gear. To bring any one of the first driven gear12, the second driven gear13, the third driven gear14, the fourth driven gear15, the fifth driven gear16, and the reverse driven gear into engagement with the transmission output shaft18, either the first meshing gearing19, the second meshing gearing20, or the third meshing gearing21is to be moved. To move either the first meshing gearing19, the second meshing gearing20, or the third meshing gearing21, a shift/select mechanism27is operated using a shift first actuator23, a shift second actuator24, a select first actuator25, and a select second actuator26.

Bringing either one of the first meshing gearing19, the second meshing gearing20, and the third meshing gearing21into engagement with any one of the first driven gear12, the second driven gear13, the third driven gear14, the fourth driven gear15, the fifth driven gear16, and the reverse driven gear allows the rotating torque of the transmission input shaft10to be transmitted to the transmission output shaft18through either the first meshing gearing19, the second meshing gearing20, or the third meshing gearing21. In addition, there is provided a sensor30for detecting the speed of the transmission output shaft18. The sensor30functions as a system for detecting an output shaft speed.

The shift/select mechanism27may be configured using a shifter rail, a shifter fork, and the like. The shift/select mechanism27may even be formed into a drum type. The shift/select mechanism27is also provided with a position holding mechanism (not shown) for holding gear positions, thereby preventing gears from coming off position during running.

An assist clutch203,204is also provided as one type of the transmitting torque variable mechanism. An assist clutch input disc203and an assist clutch output disc204are engaged with each other when the seventh drive gear201is connected to the assist clutch input disc203and the transmission input shaft10is connected to the assist clutch output disc204. This allows the torque of the seventh driven gear202to be transmitted to the transmission output shaft18.

A hydraulically operated actuator205is used for controlling a thrust force (or an assist clutch torque) between the assist clutch input disc203and the assist clutch output disc204. The output from the engine1can be transmitted or shut down by regulating this thrust force (the assist clutch torque).

The transmitting torque variable mechanism may be formed using a friction transmission mechanism, a motor-generator, or the like. The friction transmission mechanism refers to a mechanism that generates a frictional force using a thrust force of a friction surface, thereby transmitting torque. A typical application of the friction transmission mechanism is a friction clutch. The friction clutch is available in several different varieties. The varieties include the dry type single plate clutch, a dry type multi-plate clutch, the wet type multiple disc clutch, an electromagnetic clutch, and the like.

The control system in accordance with the preferred embodiment of the present invention uses the wet type multiple disc clutch as the friction transmission mechanism for the assist clutch203,204. Any other type of transmitting torque variable mechanism can be used.

As explained in the foregoing, the rotating torque of the transmission input shaft10is transmitted from the first drive gear4, the second drive gear5, the third drive gear6, the fourth drive gear7, the fifth drive gear8, the reverse drive gear, and the seventh drive gear201through the first driven gear12, the second driven gear13, the third driven gear14, the fourth driven gear15, the fifth driven gear16, the reverse driven gear, and the seventh driven gear202to the transmission output shaft18. The rotating torque is then transmitted to an axle (not shown) through a differential gear (not shown) connected to the transmission output shaft18.

The input shaft clutch actuator22controls the thrust force (the input shaft clutch torque) between the input shaft clutch input disc2and the input shaft clutch output disc3. The assist clutch actuator205controls the thrust force (the assist clutch torque) between the assist clutch input disc203and the assist clutch output disc204. A hydraulic pressure control unit102controls the hydraulic pressure for the input shaft clutch actuator22and the assist clutch actuator205as detailed in the following. Specifically, the hydraulic pressure control unit102controls a current flowing through a solenoid valve (not shown) provided for each actuator. A stroke of a hydraulic cylinder (not shown) provided for each actuator is thereby adjusted to achieve an intended level of hydraulic pressure for each actuator. The transmitting torque of each clutch is thus controlled.

The hydraulic pressure control unit102also controls a current flowing through a solenoid valve (not shown) provided for the select first actuator25and the select second actuator26. A stroke of a hydraulic cylinder (not shown) provided for each of these actuators is thereby adjusted to achieve an intended level of hydraulic pressure for each actuator. Either the first meshing gearing19, the second meshing gearing20, or the third meshing gearing21is thus selected and moved as necessary.

Further, the hydraulic pressure control unit102controls a current flowing through a solenoid valve (not shown) provided for each of the shift first actuator23and the shift second actuator24. A stroke of a hydraulic cylinder (not shown) provided for each of these actuators is thereby adjusted to achieve an intended level of hydraulic pressure for each actuator. A load for operating the first meshing gearing19, the second meshing gearing20, and the third meshing gearing21can thus be controlled.

The control system in accordance with the preferred embodiment of the present invention uses hydraulic actuators for the shift first actuator23and the shift second actuator24, and the select first actuator25and the select second actuator26, all used for driving the shift/select mechanism27. Use of an electric actuator operated by an electric motor or the like is nonetheless possible.

A single actuator may be used instead of the shift first actuator23and the shift second actuator24. Further, a single actuator may also be used instead of the select first actuator25and the select second actuator26. A shifter rail, a shifter fork, and the like may be used to form a mechanism for operating the first meshing gearing19, the second meshing gearing20, and the third meshing gearing21. Or a drum type, or any other type of mechanism may be formed for moving the dog clutch19,20,21.

The control system in accordance with the preferred embodiment of the present invention uses hydraulic actuators for the input shaft clutch actuator22and the assist clutch actuator205. Use of an electric actuator operated by an electric motor or the like is nonetheless possible.

Controlling the amount of intake air, the amount of fuel, ignition timing, and the like using the engine control unit101allows torque of the engine1to be controlled accurately. A power train control unit100controls the hydraulic pressure control unit102and the engine control unit101. The power train control unit100, the engine control unit101, and the hydraulic pressure control unit102exchange information between each other using communications means103.

The control system in accordance with the preferred embodiment of the present invention uses hydraulic actuators. This results in the hydraulic pressure control unit102being used for controlling the hydraulic actuators. With the electric actuator operated by the electric motor or the like, however, an electric motor control unit is to be used instead of the hydraulic pressure control unit102.

FIG. 2is a block diagram showing input/output (I/O) signals sent and received by the power train control unit100, the engine control unit101, and the hydraulic pressure control unit102through the communications means103. The power train control unit100is formed as a control unit including an input portion100i, an output portion100o, and a computer100c. Similarly, the engine control unit101is formed as a control unit including an input portion101i, an output portion101o, and a computer101c. The hydraulic pressure control unit102is also formed as a control unit including an input portion102i, an output portion102o, and a computer102c. An engine torque command value tTe is sent from the power train control unit100to the engine control unit101using the communications means103. To achieve tTe, the engine control unit101controls the amount of intake air, the amount of fuel, ignition timing (not shown), and the like of the engine1. There are provided inside the engine control unit101means (not shown) for detecting an engine torque that serves as an input torque for the transmission. The engine control unit101detects a speed Ne of the engine1and an engine torque Te generated by the engine1. The engine control unit101then sends signals representing the information to the power train control unit100using the communications means103. A torque sensor may be used for the engine torque detection means. Another possible approach for the engine torque detection means is to use estimation means making an estimate based on engine parameters, such as an injector injection pulse width, an intake pipe vacuum, the engine speed, and the like.

The power train control unit100sends signals representing the following information to the hydraulic pressure control unit102: an input shaft clutch target torque TTqSTA, a target shift load Fsft, a target select position tpSEL, and an assist clutch target torque TTqa. The hydraulic pressure control unit102controls the input shaft clutch actuator22so as to achieve the input shaft clutch target torque TTqSTA. The input shaft clutch input disc2and the input shaft clutch output disc3are thereby engaged with, or released from, each other.

To achieve the target shift load Fsft and the target select position tpSEL, the hydraulic pressure control unit102controls the shift first actuator23, the shift second actuator24, the select first actuator25, and the select second actuator26, thereby operating the shift/select mechanism27. A shift position or a select position are thereby controlled to eventually engaged or release the first meshing gearing19, the second meshing gearing20, and the third meshing gearing21. In addition, to achieve the assist clutch target torque TTqa, the hydraulic pressure control unit102controls the assist clutch actuator205to engage or release the assist clutch input disc203and the assist clutch output disc204.

The hydraulic pressure control unit102detects a position signal rpSTA, a shift position signal rpSFT, and a select position signal rpSEL indicating that the input shaft clutch is engaged or released. The hydraulic pressure control unit102transmits these signals to the power train control unit100.

Signals representing an input shaft speed Ni and an output shaft speed No are applied to the power train control unit100from the input shaft speed sensor29and the output shaft speed sensor30, respectively. In addition to these signals, a range position signal RngPos indicating a shift lever position such as a P range, an R range, an N range, a D range, or the like, a signal representing an accelerator pedal depression amount Aps, and an ON/OFF signal Brk from a brake switch for detecting whether or not a brake pedal is depressed are applied to the power train control unit100. If, for example, a driver places the shift lever in the D range or the like and depresses an accelerator pedal, the power train control unit100determines that the driver intends to start a vehicle or accelerate the vehicle. If, for example, the driver depresses the brake pedal, the power train control unit100determines that the driver intends to decelerate or stop the vehicle. The power train control unit100then sets the engine torque command value tTe, the input shaft clutch target torque TTqSTA, the target shift load Fsft, and the target select position tpSEL so as to achieve the driver's intention.

Further, a gearshift position is set from a vehicle speed Vsp calculated from the output shaft speed No and the accelerator pedal depression amount Aps. To execute a gearshift operation into the gearshift position thus set, the engine torque command value tTe, the input shaft clutch target torque TTqSTA, the target shift load Fsft, the target select position tpSEL, and the assist clutch target torque TTqa are then set.

Specific control operations performed during the gearshift in the motor vehicle control system according to the preferred embodiment of the present invention will be described with reference toFIGS. 3 through 13.

Overall control operations performed during the gearshift in the motor vehicle control system according to the preferred embodiment of the present invention will first be described with reference toFIG. 3.

FIG. 3is a flowchart showing control operations performed during the gearshift in the motor vehicle control system according to the preferred embodiment of the present invention. Specific operations of the gearshift control described hereunder that have previously been programmed in the computer100cof the power train control unit100are executed repeatedly at a predetermined cycle. That is, operations of steps301through311given in the following are executed by the power train control unit100. In step301, the power train control unit100reads parameters. In step302, a gearshift operation is started by setting the gearshift position based on the vehicle speed Vsp and the accelerator pedal depression amount Aps. In step303(a release control phase), release control is executed to release the gear. In step304, it is determined whether or not the release control is completed. If it is determined that the release control is completed, the control operation proceeds to step305. If it is determined that the release control is yet to be completed, step303is re-executed. In step305(a rotation synchronization control phase), the assist clutch torque is controlled so as to make the input speed synchronized with a speed (a target speed) corresponding to the next gearshift position. In step306, it is determined whether or not the rotation synchronization control is completed. If it is determined that the rotation synchronization control is completed, the control operation proceeds to step307. If it is determined that the rotation synchronization control is yet to be completed, step305is re-executed. In step307(an engagement control phase), gear engagement control is executed. In step308, it is determined whether or not the engagement control is completed. If it is determined that the engagement control is completed, the control operation proceeds to step309. If it is determined that the engagement control is yet to be completed, step307is re-executed. In step309(an assist clutch release phase), an assist clutch torque release control is executed. In step310, it is determined whether or not the assist clutch torque release control is completed. If it is determined that the assist clutch torque release control is completed, the control operation proceeds to step311. If it is determined that the assist clutch torque release control is yet to be completed, step310is re-executed. The assist clutch torque release control is completed if the assist clutch target torque is 0.

In step311(a gearshift termination phase), the gearshift control is terminated.

Details of a timer indicating an elapsed time of specific control operations performed during the gearshift in the motor vehicle control system according to the preferred embodiment of the present invention will be described with reference toFIG. 4.

FIG. 4is a flowchart showing details of the timer indicating an elapsed time of specific control operations performed during the gearshift in the motor vehicle control system according to the preferred embodiment of the present invention.

Specific details of the timer described hereunder that have previously been programmed in the computer100cof the power train control unit100are executed repeatedly at a predetermined cycle. That is, operations of steps401and402given in the following are executed by the power train control unit100.

In step401, it is determined whether or not the assist clutch torque release control is being provided. If it is determined that the assist clutch torque release control is being provided, the control operation proceeds to step402. In step402, an assist clutch torque release control timer Tmr_tof counts up. If it is determined that the assist clutch torque release control is not being provided, the control operation proceeds to step403. In step403, the assist clutch torque release control timer Tmr_tof is reset.

Operations of a first control in step309(the assist clutch release control phase) performed as part of the gearshift control in the motor vehicle control system according to the preferred embodiment of the present invention will be described with reference toFIGS. 5 and 6.

FIG. 5is a flowchart showing control provided in step309(the assist clutch torque release control phase) ofFIG. 3. In step501, parameters are read. In step502, it is determined whether or not the current operation is immediately after the start of the assist clutch torque release control phase. If the assist clutch torque release control phase timer Tmr_tof is 0, the control operation proceeds to step503. If the assist clutch torque release control phase timer Tmr_tof is not 0, the control operation proceeds to step504. In step503, an assist clutch torque release speed dTTqa is calculated. The assist clutch torque release speed dTTqa in step503is a function of a transmission input torque Tqin. In step504, an assist clutch target torque at assist clutch torque release is calculated.

FIG. 6shows typical setting values for the function f1of step503shown inFIG. 5. It is desirable that the setting value for the function f1of step503be set to a greater value as the transmission input torque Tqin becomes greater. It is also desirable that the function f1be set uniquely for each of different gearshift positions. In step503, the assist clutch torque release speed dTTqa is calculated from the transmission input torque Tqin. Instead of using the transmission input torque Tqin, the assist clutch torque release speed dTTqa may be calculated from an accelerator opening, a vehicle acceleration, a step in a transmission output torque as calculated using transmission input torque×reduction gear ratio after gearshift—transmission input torque×assist gear ratio, a quantity of heat generated by the assist clutch, and the like.

FIGS.7(A1) through (G2) are timing charts showing conditions of the first control performed as part of the gearshift control shown inFIGS. 5 and 6.

FIG.7(A1) and FIG.7(A2) represent a transmission input torque transmitted to the transmission input shaft10shown inFIG. 1. FIG.7(B1) and FIG.7(B2) represent the speed of the transmission input shaft10shown inFIG. 1. FIG.7(C1) and FIG.7(C2) represent a position (a shift position) of the first meshing gearing19shown inFIG. 1. FIG.7(D1) and FIG.7(D2) represent a command current applied to the hydraulic pressure control unit102driving the assist actuator205shown inFIG. 1. FIG.7(E1) and FIG.7(E2) represent an actual hydraulic pressure for driving the assist actuator205shown inFIG. 1. FIG.7(F1) and FIG.7(F2) represent the assist clutch torque. FIG.7(G1) and FIG.7(G2) represent the output torque of the transmission output shaft18shown inFIG. 1. The abscissa represents time.

FIGS.7(A1) through7(G1) show the transmission input torque, the input shaft speed, the shift position, the command current, the actual hydraulic pressure, the assist clutch torque, and the transmission output torque, respectively, at different timings during a gearshift from the combination of gears4and12(hereinafter referred to as a “1st speed”) to the combination of gears5and13(hereinafter referred to as a “2nd speed”).

Similarly, FIGS.7(A2) through7(G2) show the transmission input torque, the input shaft speed, the shift position, the command current, the actual hydraulic pressure, the assist clutch torque, and the transmission output torque, respectively, at different timings during the gearshift from the 1st speed to the 2nd speed. The values of the transmission input torque shown in FIGS.7(A2) through7(G2) differ from those shown in FIGS.7(A1) through7(G1).

When a gearshift command to the 2nd speed is issued at time t1during running in the 1st speed, gearshift control is started. When the command current is gradually increased as shown in a period of time from time t1to time t2of FIG.7(D1) and FIG.7(D2), the actual hydraulic pressure gradually increases as shown in the period of time from time t1to time t2of FIG.7(E1) and FIG.7(E2). The assist clutch torque also gradually increases as shown in the period of time from time t1to time t2of FIG.7(F1) and FIG.7(F2).

At this time, the transmission output torque gradually decreases as shown in the period of time from time t1to time t2of FIG.7(G1) and FIG.7(G2). Then at time t2, the first meshing gearing19, which has so far been engaged with the 1st speed side, is set into a state to be released. This is because torque transmitted by the gears201and202causes torque transmitted by the gears4and12to be decreased to a value that allows the first meshing gearing19to be released.

When the first meshing gearing19is in the state to be released, the actuator27is controlled so as to release the first meshing gearing19, which has been engaged with the1st speed side, bringing the first meshing gearing19into a neutral position to initiate an actual gearshift, as shown in a period of time from time t2to time t3in FIG.7(C1) and FIG.7(C2).

When the first meshing gearing19is in the neutral position, the assist clutch torque is controlled to bring the input shaft speed to a level corresponding to the 2nd speed. When the input shaft speed reaches a level corresponding to the 2nd speed as shown at time t4of FIG.7(B1) and FIG.7(B2), the first meshing gearing19is allowed to engage with the 2nd speed side as shown in a period of time from time t4to time t5of FIG.7(B1) andFIG. 7(B2).

When the command current is gradually decreased as shown in a period of time from time t5to time t6, during which the first meshing gearing19is engaged in the 2nd speed, the actual hydraulic pressure gradually decreases as shown in the period of time from time t5to time t6of FIG.7(E1) and FIG.7(E2). The assist clutch torque also gradually decreases as shown in the period of time from time t5to time t6of FIG.7(F1) andFIG. 7(F2). At this time, the transmission output torque gradually increases as shown in the period of time from time t5to time t6of FIG.7(G1) and FIG.7(G2). When the release of the assist clutch torque is completed at time t6, torque is then transmitted only with the 2nd speed gear.

The command current applied to the hydraulic pressure control unit102that drives the assist actuator205ofFIG. 1is controlled so that the assist clutch torque release speed changes as shown in a portion encircled in FIG.7(F1) and in a portion encircled in FIG.7(F2). This reduces axle vibration at the end of the gearshift in each of different cases of varying values of the transmission input torque.

FIGS.8(A1) through (G2) are timing charts showing conditions of a second control performed as part of the gearshift control shown inFIGS. 5 and 6.

FIGS.8(A1) and FIG.8(A2) represent the transmission input torque transmitted to the transmission input shaft10shown inFIG. 1. FIG.8(B1) and FIG.8(B2) represent the speed of the transmission input shaft10shown inFIG. 1. FIG.8(C1) represents the position (the shift position) of the first meshing gearing19shown inFIG. 1. FIG.8(C2) represents the position (the shift position) of the first meshing gearing19and the second meshing gearing20shown inFIG. 1. FIG.8(D1) and FIG.8(D2) represent the command current applied to the hydraulic pressure control unit102driving the assist actuator205shown inFIG. 1. FIG.8(E1) and FIG.8(E2) represent the actual hydraulic pressure for driving the assist actuator205shown inFIG. 1. FIG.8(F1) and FIG.8(F2) represent the assist clutch torque. FIG.8(G1) and FIG.8(G2) represent the output torque of the transmission output shaft18shown inFIG. 1. The abscissa represents time.

FIGS.8(A1) through8(G1) show the transmission input torque, the input shaft speed, the shift position, the command current, the actual hydraulic pressure, the assist clutch torque, and the transmission output torque, respectively, at different timings during a gearshift from the 1st speed to the 2nd speed.

FIGS.8(A2) through8(G2) show the transmission input torque, the input shaft speed, the shift position, the command current, the actual hydraulic pressure, the assist clutch torque, and the transmission output torque, respectively, at different timings during the gearshift from the 2nd speed to the combination of gears6and14(hereinafter referred to as a “3rd speed”).

When a gearshift command to the 2nd speed is issued at time t1during running in the 1st speed, gearshift control is started. If a gearshift command to the 3rd speed is issued at time t1during running in the 2nd speed, gearshift control is started. When the command current is gradually increased as shown in a period of time from time t1to time t2ofFIG. 8(D1) and FIG.8(D2), the actual hydraulic pressure gradually increases as shown in the period of time from time t1to time t2of FIG.8(E1) and FIG.8(E2). The assist clutch torque also gradually increases as shown in the period of time from time t1to time t2of FIG.8(F1) and FIG.8(F2).

At this time, the transmission output torque gradually decreases as shown in the period of time from time t1to time t2of FIG.8(G1) and FIG.8(G2). Then at time t2, the first meshing gearing19, which has so far been engaged with the1st speed side, is set into a state to be released during the gearshift from the 1st speed to the 2nd speed. During the gearshift from the 2nd speed to the 3rd speed, the first meshing gearing19, which has so far been engaged with the 2nd speed side, is set into a state to be released.

This is because torque transmitted by the gears201and202causes torque transmitted by the gears4and12to be decreased, during the gearshift from the 1st speed to the 2nd speed, to a value that allows the first meshing gearing19to be released. In addition, during the gearshift from the 2nd speed to the 3rd speed, on the other hand, the torque transmitted by the gears201and202causes torque transmitted by the gears5and13to be decreased to the value that allows the first meshing gearing19to be released.

When the first meshing gearing19and the second meshing gearing20are in the state to be released, the actuator27is controlled, during the gearshift from the 1st speed to the 2nd speed, so as to release the first meshing gearing19, which has been engaged with the 1st speed side. The first meshing gearing19is thereby brought into a neutral position as shown in a period of time from time t2to time t3in FIG.8(C1). Then, the assist clutch torque is controlled to bring the input shaft speed to a level corresponding to the 2nd speed. During the gearshift from the 2nd speed to the 3rd speed, on the other hand, the actuator27is controlled so as to release the first meshing gearing19, which has been engaged with the 2nd speed side, thereby bringing the first meshing gearing19into a neutral position as shown in a period of time from time t2to time t3in FIG.8(C2). Then, the assist clutch torque is controlled to bring the input shaft speed to a level corresponding to the 3rd speed.

During the gearshift from the 1st speed to the 2nd speed, when the input shaft speed reaches a level corresponding to the 2nd speed as shown at time t4of FIG.8(B1), the first meshing gearing19is allowed to engage with the 2nd speed side as shown in a period of time from time t4to time t5of FIG.8(B1). During the gearshift from the 2nd speed to the 3rd speed, when the input shaft speed reaches a level corresponding to the 3rd speed as shown at time t4of FIG.8(B2), the second meshing gearing20is engaged with the 3rd speed side as shown in a period of time from time t4to time t5of FIG.8(B2).

During the gearshift from the 1st speed to the 2nd speed, the command current is gradually decreased as shown in a period of time from time t5to time t6, during which the first meshing gearing19is engaged with the 2nd speed. During the gearshift from the 2nd speed to the 3rd speed, on the other hand, the command current is gradually decreased as shown in a period of time from time t5to time t6, during which the second meshing gearing20is engaged with the 3rd speed. The actual hydraulic pressure then gradually decreases as shown in the period of time from time t5to time t6of FIG.8(E1) and FIG.8(E2). The assist clutch torque also gradually decreases as shown in the period of time from time t5to time t6of FIG.8(F1) and FIG.8(F2). At this time, the transmission output torque gradually increases as shown in the period of time from time t5to time t6of FIG.8(G1) andFIG. 8(G2). When the release of the assist clutch torque is completed at time t6, torque is then transmitted only with the 2nd speed gear.

The command current applied to the hydraulic pressure control unit102that drives the assist actuator205ofFIG. 1is controlled so that the assist clutch torque release speed changes as shown in a portion encircled in FIG.8(F1) and in a portion encircled in FIG.8(F2). This reduces axle vibration at the end of the gearshift in each of different cases of varying reduction gear ratios at the end of the gearshift.

Operations of a second control in step309(the assist clutch torque release control phase) performed as part of the gearshift control in the motor vehicle control system according to the preferred embodiment of the present invention will be described with reference toFIG. 9.

FIG. 9is a flowchart showing control provided in step309(the assist clutch torque release control phase) ofFIG. 3. In step901, parameters are read. In step902, an actual transmission output torque RTqo is calculated. The actual transmission output torque RTqo may be directly detected using a torque sensor or estimated based on changes in the output shaft speed or the like. In step903, it is determined whether or not the current operation is immediately after the start of the assist clutch torque release control phase. If the assist clutch torque release control phase timer Tmr_tof is 0, the control operation proceeds to step904. If the assist clutch torque release control phase timer Tmr_tof is not 0, the control operation proceeds to step906. In step904, transmission output torque at the end of gearshift TTqo is calculated using the transmission input torque Tqin and a reduction gear ratio after the gearshift Gro. In step905, the assist clutch target torque at assist clutch torque release TTqa is set to 0. In step906, a transmission output torque deviation at the end of gearshift ETqo is calculated using the transmission output torque at the end of gearshift TTqo and the actual transmission output torque RTqo. In step907, a feedback amount TTqaFB is calculated based on the transmission output torque deviation at the end of gearshift ETqo. In step908, the assist clutch target torque at assist clutch torque release TTqa is set to TTqaFB.

FIGS.10(A1) through (G1) are timing charts showing conditions of the gearshift control shown inFIG. 9. FIG.10(A1) represents transmission input torque transmitted to the transmission input shaft10shown inFIG. 1. FIG.10(B1) represents the speed of the transmission input shaft10shown inFIG. 1. FIG.10(C1) represents a position (a shift position) of the first meshing gearing19shown inFIG. 1. FIG.10(D1) represents a command current applied to the hydraulic pressure control unit102driving the assist actuator205shown inFIG. 1. FIG.10(E1) represents an actual hydraulic pressure for driving the assist actuator205shown inFIG. 1. FIG.10(F1) represents the assist clutch torque.FIG. 10(G1) represents the output torque of the transmission output shaft18shown inFIG. 1. The abscissa represents time.

FIGS.10(A1) through10(G1) show the transmission input torque, the input shaft speed, the shift position, the command current, the actual hydraulic pressure, the assist clutch torque, and the transmission output torque, respectively, at different timings during a gearshift from the 1st speed to the 2nd speed.

When a gearshift command to the 2nd speed is issued at time t1during running in the 1st speed, gearshift control is started. When the command current is gradually increased as shown in a period of time from time t1to time t2of FIG.10(D1), the actual hydraulic pressure gradually increases as shown in the period of time from time t1to time t2ofFIG. 10(E1). The assist clutch torque also gradually increases as shown in the period of time from time t1to time t2of FIG.10(F1). At this time, the transmission output torque gradually decreases as shown in the period of time from time t1to time t2of FIG.10(G1). Then at time t2, the first meshing gearing19, which has so far been engaged with the 1st speed side, is set into a state to be released. This is because torque transmitted by the gears201and202causes torque transmitted by the gears4and12to be decreased to a value that allows the first meshing gearing19to be released.

When the first meshing gearing19is in the state to be released, the actuator27is controlled so as to release the first meshing gearing19, which has been engaged with the 1st speed side. The first meshing gearing19is thereby brought into a neutral position to initiate an actual gearshift, as shown in a period of time from time t2to time t3in FIG.10(C1). When the first meshing gearing19is in the neutral position, the assist clutch torque is controlled to bring the input shaft speed to a level corresponding to the 2nd speed.

When the input shaft speed reaches a level corresponding to the 2nd speed as shown at time t4of FIG.10(B1), the first meshing gearing19is allowed to engage with the 2nd speed side as shown in a period of time from time t4to time t5of FIG.10(B1). When the command current is decreased as shown in a period of time from time t5to time t6, during which the first meshing gearing19is engaged with the 2nd speed, the actual hydraulic pressure decreases as shown in the period of time from time t5to time t6of FIG.10(E1). The assist clutch torque also decreases as shown in the period of time from time t5to time t6of FIG.10(F1). At this time, the transmission output torque gradually increases as shown in the period of time from time t5to time t6of FIG.10(G1). When the release of the assist clutch torque is completed at time t6, torque is then transmitted only with the 2nd speed gear. This eliminates torque vibration in the transmission output, thereby reducing axle vibration at the end of the gearshift.

Operations of a third control in step309(the assist clutch torque release control phase) performed as part of the gearshift control in the motor vehicle control system according to the preferred embodiment of the present invention will be described with reference toFIGS. 11 and 12.

FIG. 11is a flowchart showing control provided in step309(the assist clutch torque release control phase) ofFIG. 3. In step1101, parameters are read. In step1102, it is determined whether or not the current operation is immediately after the start of the assist clutch torque release control phase. If the assist clutch torque release control phase timer Tmr_tof is 0, the control operation proceeds to step1103. If the assist clutch torque release control phase timer Tmr_tof is not 0, the control operation proceeds to step1105. In step1103, the assist clutch target torque at assist clutch torque release TTqa is calculated. In step1104, the assist clutch target torque at assist clutch torque release calculation is preformed. The assist clutch target torque at assist clutch torque release TTqa is a function of the transmission input torque Tqin and the assist clutch torque release control phase timer Tmr_tof.

FIG. 12shows a typical first setting value for the function f2of step1104shown inFIG. 11. The first setting value of the function f2in step1104is the same as that of the assist clutch target torque at assist clutch torque release calculated in steps902through908ofFIG. 9.

This eliminates the need for detecting the actual transmission output torque. The same effect can therefore be produced even without using an expensive torque sensor. The approach lightens calculation load, since there is no need of calculating the feedback amount as calculated in steps1406and1407ofFIG. 9.

It is desirable that the first setting value of the function f2in step1104be set to a greater value as the transmission input torque Tqin becomes greater. It is also desirable that the function f2be set uniquely for each of different gearshift positions when releasing the assist gear clutch torque.

FIGS.13(A1) through (G1) are timing charts showing conditions of the gearshift control shown inFIGS. 11 and 12. FIG.13(A1) represents transmission input torque transmitted to the transmission input shaft10shown inFIG. 1. FIG.13(B1) represents the speed of the transmission input shaft10shown inFIG. 1. FIG.13(C1) represents a position (a shift position) of the first meshing gearing19shown inFIG. 1. FIG.13(D1) represents a command current applied to the hydraulic pressure control unit102driving the assist actuator205shown inFIG. 1. FIG.13(E1) represents an actual hydraulic pressure for driving the assist actuator205shown inFIG. 1. FIG.13(F1) represents the assist clutch torque.FIG. 13(G1) represents the output torque of the transmission output shaft18shown inFIG. 1. The abscissa represents time.

FIGS.13(A1) through13(G1) show the transmission input torque, the input shaft speed, the shift position, the command current, the actual hydraulic pressure, the assist clutch torque, and the transmission output torque, respectively, at different timings during a gearshift from the 1st speed to the 2nd speed.

When a gearshift command to the 2nd speed is issued at time t1during running in the 1st speed, gearshift control is started. When the command current is gradually increased as shown in a period of time from time t1to time t2of FIG.13(D1), the actual hydraulic pressure gradually increases as shown in the period of time from time t1to time t2ofFIG. 13(E1). The assist clutch torque also gradually increases as shown in the period of time from time t1to time t2of FIG.13(F1). At this time, the transmission output torque gradually decreases as shown in the period of time from time t1to time t2of FIG.13(G1). Then at time t2, the first meshing gearing19, which has so far been engaged with the 1st speed side, is set into a state to be released. This is because torque transmitted by the gears201and202causes torque transmitted by the gears4and12to be decreased to a value that allows the first meshing gearing19to be released.

When the first meshing gearing19is in the state to be released, the actuator27is controlled so as to release the first meshing gearing19, which has been engaged with the1st speed side. The first meshing gearing19is thereby brought into a neutral position to initiate an actual gearshift, as shown in a period of time from time t2to time t3in FIG.13(C1).

When the first meshing gearing19is in the neutral position, the assist clutch torque is controlled to bring the input shaft speed to a level corresponding to the 2nd speed. When the input shaft speed reaches a level corresponding to the 2nd speed as shown at time t4of FIG.13(B1), the first meshing gearing19is allowed to engage with the 2nd speed side as shown in a period of time from time t4to time t5of FIG.13(B1).

When the command current is decreased as shown in a period of time from time t5to time t6, during which the first meshing gearing19is engaged with the 2nd speed, the actual hydraulic pressure decreases as shown in the period of time from time t5to time t6of FIG.13(E1). The assist clutch torque also decreases as shown in the period of time from time t5to time t6of FIG.13(F1).

At this time, the transmission output torque gradually increases as shown in the period of time from time t5to time t6of FIG.13(G1). When the release of the assist clutch torque is completed at time t6, torque is then transmitted only with the 2nd speed gear. This eliminates torque vibration in the transmission output, thereby reducing axle vibration at the end of the gearshift.

FIG. 14shows a typical second setting value for the function f2of step1104shown inFIG. 11.

The second setting value for the function f2of step1104is a setting value obtained by adjusting the first setting value for the function f2of step1104in consideration of response of the actual hydraulic pressure for driving the assist actuator205ofFIG. 1. It is desirable that the second setting value of the function f2in step1104be set to a greater value as the transmission input torque Tqin becomes greater. It is also desirable that the function f2be set uniquely for each of different gearshift positions when releasing the assist gear clutch torque.

FIGS.15(A1) through (G1) are timing charts showing conditions of the gearshift control shown inFIGS. 11 and 14. FIG.15(A1) represents a transmission input torque transmitted to the transmission input shaft10shown inFIG. 1. FIG.15(B1) represents the speed of the transmission input shaft10shown inFIG. 1. FIG.15(C1) represents a position (a shift position) of the first meshing gearing19shown inFIG. 1. FIG.15(D1) represents a command current applied to the hydraulic pressure control unit102driving the assist actuator205shown inFIG. 1. FIG.15(E1) represents an actual hydraulic pressure for driving the assist actuator205shown inFIG. 1. FIG.15(F1) represents the assist clutch torque.FIG. 15(G1) represents the output torque of the transmission output shaft18shown inFIG. 1. The abscissa represents time.

FIGS.15(A1) through13(G1) show the transmission input torque, the input shaft speed, the shift position, the command current, the actual hydraulic pressure, the assist clutch torque, and the transmission output torque, respectively, at different timings during a gearshift from the 1st speed to the 2nd speed.

When a gearshift command to the 2nd speed is issued at time t1during running in the 1st speed, gearshift control is started. When the command current is gradually increased as shown in a period of time from time t1to time t2of FIG.15(D1), the actual hydraulic pressure gradually increases as shown in the period of time from time t1to time t2ofFIG. 15(E1). The assist clutch torque also gradually increases as shown in the period of time from time t1to time t2of FIG.15(F1). At this time, the transmission output torque gradually decreases as shown in the period of time from time t1to time t2of FIG.15(G1). Then at time t2, the first meshing gearing19, which has so far been engaged with the 1st speed side, is set into a state to be released. This is because torque transmitted by the gears201and202causes torque transmitted by the gears4and12to be decreased to a value that allows the first meshing gearing19to be released.

When the first meshing gearing19is in the state to be released, the actuator27is controlled so as to release the first meshing gearing19, which has been engaged with the 1st speed side. The first meshing gearing19is thereby brought into a neutral position to initiate an actual gearshift, as shown in a period of time from time t2to time t3in FIG.15(C1). When the first meshing gearing19is in the neutral position, the assist clutch torque is controlled to bring the input shaft speed to a level corresponding to the 2nd speed. When the input shaft speed reaches a level corresponding to the 2nd speed as shown at time t4of FIG.15(B1), the first meshing gearing19is allowed to engage with the 2nd speed side as shown in a period of time from time t4to time t5of FIG.15(B1).

When the command current is decreased as shown in a period of time from time t5to time t6, during which the first meshing gearing19is engaged in the 2nd speed, the actual hydraulic pressure decreases as shown in the period of time from time t5to time t6ofFIG. 15(E1). The assist clutch torque also decreases as shown in the period of time from time t5to time t6of FIG.15(F1). At this time, the transmission output torque increases as shown in the period of time from time t5to time t6of FIG.15(G1). When the release of the assist clutch torque is completed at time t6, torque is then transmitted only with the 2nd speed gear. This eliminates torque vibration in the transmission output, thereby reducing axle vibration at the end of the gearshift.

In accordance with the present invention, release control of the transmitting torque variable mechanism can be optimally provided according to vehicle operating conditions.

While the invention has been described in its preferred embodiments, it is to be understood that the words which have been used are words of description rather than limitation and that changes within the purview of the appended claims may be made without departing from the true scope and spirit of the invention in its broader aspects.