JP2021167611A - Control device of vehicle - Google Patents

Abstract

To suppress engine stall even at a very low temperature of a hydraulic fluid in switching a shift position of an automatic transmission from a non-travel position to a travel position when a vehicle is stopped in an operation state of an engine and in a state of applying braking force to a driving wheel.SOLUTION: In a case when a shift position is switched from a non-travel position to a travel position when a vehicle is stopped in an operation state of an engine and in a state of applying braking force to driving wheels, an operation state of an engagement device for starting by a time to execute a brake-off operation, is kept in a slip state in transients to switch the engagement device for starting from a release state to an engagement state, so that differential rotation between a transmission input shaft and the driving wheels is allowed, LU dragging torque is reduced, and driving system load torque is reduced. Thus, engine stall can be suppressed even at a very low temperature of a hydraulic fluid in switching the shift position to the travel position during stop of the vehicle.SELECTED DRAWING: Figure 4

Description

The present invention relates to a vehicle control device including an engine, an automatic transmission having a starting engagement device, and a wet multi-plate clutch provided between the engine and the automatic transmission.

The automatic transmission includes an engine and an automatic transmission that forms a part of a power transmission path between the engine and the drive wheels, and the automatic transmission cannot transmit power in the shift position of the automatic transmission. It has a starting engagement device that switches the operating state from the released state to the engaged state when the automatic transmission is switched from the non-traveling position in the state to the traveling position in which the automatic transmission can transmit power. Vehicle controls are well known. For example, the vehicle control device described in Patent Document 1 is that. In Patent Document 1, when the shift position of the automatic transmission is switched from the non-traveling position to the traveling position, the command pressure of the engaging hydraulic pressure of the starting engaging device is first set to the starting engaging device in the released state. It is disclosed that the initial control pressure for promptly filling the hydraulic cylinder into the hydraulic cylinder is set, and then the constant pressure standby pressure lower than the initial control pressure is maintained for a predetermined time and then gradually increased with a predetermined gradient. There is.

Japanese Unexamined Patent Publication No. 2006-46354

By the way, a vehicle in which a clutch is provided in a power transmission path between an engine and an automatic transmission is also well known. This clutch is, for example, a known torque converter lockup clutch. On the other hand, when the vehicle is stopped in the operating state of the engine and the braking force is applied to the drive wheels, when the starting engaging device is switched from the released state to the engaged state, the input of the automatic transmission is input. The rotating members in the power transmission path from the rotating member, that is, from the output rotating member of the clutch to the drive wheels are integrally connected and stopped rotating. At this time, if the clutch is in the released state, a differential rotation occurs in the clutch and the occurrence of engine stall is prevented. On the other hand, when the clutch provided between the engine and the automatic transmission is a wet multi-plate clutch, in the wet multi-plate clutch released, the lower the temperature of the hydraulic oil, the higher the viscosity of the hydraulic oil. Is increased, so that a large drag torque is likely to be generated. The drag torque of the wet multi-plate clutch is the load torque of the drive system of an automatic transmission or the like applied to the engine. Then, when the starting engagement device is switched to the engaged state when the vehicle is stopped while the engine is running and the driving wheels are applied with braking force, when the hydraulic oil is extremely low temperature, there are many wet surfaces. Since the load torque of the drive system applied to the engine, including the drag torque of the plate clutch, increases, there is a risk of engine stall.

The present invention has been made in the context of the above circumstances, and an object of the present invention is to shift position of an automatic transmission when the vehicle is stopped in a state where the engine is running and a braking force is applied to the drive wheels. It is an object of the present invention to provide a vehicle control device capable of suppressing engine stall even when the hydraulic oil is extremely low temperature when switching from a non-traveling position to a traveling position.

The gist of the first invention is (a) between the engine, an automatic transmission forming a part of a power transmission path between the engine and the drive wheels, and between the engine and the automatic transmission. A wet multi-plate clutch provided in the power transmission path of the above, and a wheel brake device that is operated so as to apply a braking force corresponding to the operation of the brake operating member by the driver to the drive wheels, and the automatic shift The machine is in an operating state when the shift position of the automatic transmission is switched from a non-traveling position in which the automatic transmission is in a state in which power transmission is not possible to a traveling position in which the automatic transmission is in a state in which power transmission is possible. Is a control device of a vehicle having a starting engaging device that can be switched from an released state to an engaged state, and (b) the driving state of the engine and the operation of the wheel brake device causes the drive wheels to have the above-mentioned. When the shift position is switched from the non-traveling position to the traveling position when the vehicle is stopped with braking force applied, an engaging pressure is applied to the starting engaging device. During the transition to switch the operating state of the starting engaging device from the released state to the engaged state, the engagement with the starting engaging device is performed after it is determined that the rotational speed of the input rotating member of the automatic transmission has started to decrease. The pressure is lowered from the engagement pressure before it is determined that the rotation speed of the input rotating member of the automatic transmission has started to decrease, and the braking force is released until the braking operating member is operated. The purpose is to control the starting engaging device so as to maintain the operating state of the starting engaging device in a slipped state.

According to the first invention, when the shift position of the automatic transmission is switched from the non-traveling position to the traveling position when the vehicle is stopped in the operating state of the engine and the braking force is applied to the drive wheels. In the transition in which an engaging pressure is applied to the starting engaging device to switch the operating state of the starting engaging device from the released state to the engaged state, the rotation speed of the input rotating member of the automatic transmission decreases. The braking force applied to the drive wheels is reduced by lowering the engagement pressure with respect to the starting engagement device after it is determined that it has started than the engagement pressure before it is determined that the rotation speed of the input rotating member of the automatic transmission has started to decrease. Since the starting engaging device is controlled so as to maintain the operating state of the starting engaging device in the slip state until the operation of the brake operating member is performed, the input rotating member of the automatic transmission is used. In other words, the differential rotation between the output rotating member of the wet multi-plate clutch and the drive wheel or axle is allowed, the drag torque in the wet multi-plate clutch is reduced, and the load torque of the drive system applied to the engine is reduced. Be forced to. Therefore, when the shift position of the automatic transmission is switched from the non-running position to the running position when the vehicle is stopped while the engine is running and the driving wheels are braked, even when the hydraulic oil is extremely low. Engine stall can be suppressed.

The period of waiting for switching the operating state of the starting engaging device to the fully engaged state is until the operation of the brake operating member for releasing the braking force is performed, and in that period, the starting engagement is performed. Since the operating state of the device is maintained in the slip state, the operating state of the starting engaging device is quickly switched from the slip state to the fully engaged state after the operation of the brake operating member that releases the braking force. As a result, when the accelerator is turned on after the operation of the brake operating member that releases the braking force, the starting engagement device is likely to be in a state where the engagement is completed or a state close to the engagement completion. Occurrence is suppressed. As described above, in the first invention, the engine stall resistance is improved while the deterioration of the drivability performance is suppressed.

It is a figure explaining the schematic structure of the vehicle to which this invention is applied, and also is the figure explaining the main part of the control function and the control system for various control in a vehicle. It is a time chart explaining an example of the case of normal time of P, N → R, D garage control. It is a figure explaining the relationship between the drive system load torque and the occurrence of an engine stall. It is a flowchart explaining the main part of the control operation of an electronic control device, and the shift position of an automatic transmission is changed from a non-traveling position to a traveling position when the vehicle is stopped in a state where the engine is running and a braking force is applied to the drive wheels. It is a flowchart explaining the control operation for suppressing an engine stall even when the hydraulic oil is extremely low temperature at the time of switching. It is a figure which shows an example of the time chart when the control operation shown in the flowchart of FIG. 4 is executed.

Hereinafter, examples of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram for explaining a schematic configuration of a vehicle 10 to which the present invention is applied, and is a diagram for explaining a control function and a main part of a control system for various controls in the vehicle 10. In FIG. 1, the vehicle 10 includes an engine 12, drive wheels 14, and a power transmission device 16 provided in a power transmission path between the engine 12 and the drive wheels 14.

The engine 12 is the power source for the vehicle 10. The engine 12 is a known internal combustion engine such as a gasoline engine or a diesel engine. The engine 12 is an engine torque Te which is an output torque of the engine 12 by controlling an engine control device 50 including a throttle actuator, a fuel injection device, an ignition device, and the like provided in the vehicle 10 by an electronic control device 90 described later. Is controlled.

The power transmission device 16 is an output rotating member of the torque converter 20 connected to the engine 12, the automatic transmission 22 connected to the torque converter 20, and the automatic transmission 22 in the case 18 as a non-rotating member attached to the vehicle body. It is provided with a reduction gear mechanism 26 connected to the transmission output gear 24, a differential gear 28 connected to the reduction gear mechanism 26, and the like. Further, the power transmission device 16 includes a pair of drive shafts 30 and the like connected to the differential gear 28. In the power transmission device 16, the power output from the engine 12 is sequentially transmitted to the drive wheels 14 via the torque converter 20, the automatic transmission 22, the reduction gear mechanism 26, the differential gear 28, the drive shaft 30, and the like. Unless otherwise specified, the above-mentioned power agrees with torque and force.

The torque converter 20 is a fluid transmission device provided in a power transmission path between the engine 12 and the automatic transmission 22 and includes a pump impeller 20p and a turbine impeller 20t. The pump impeller 20p is an input member of the torque converter 20 and is connected to the crank shaft 32 of the engine 12. The turbine impeller 20t is an output member of the torque converter 20 and is connected to the transmission input shaft 34. The crank shaft 32 is also an input rotating member of the torque converter 20. The transmission input shaft 34 is an input rotating member of the automatic transmission 22, and is also an output rotating member of the torque converter 20 integrally formed with the turbine shaft that is rotationally driven by the turbine impeller 20t.

The torque converter 20 includes a lockup clutch LU as a direct clutch that connects the pump impeller 20p and the turbine impeller 20t, that is, connects the input / output rotating members of the torque converter 20. The lockup clutch LU is a wet friction engagement device composed of a multi-plate clutch pressed by an actuator. That is, the lockup clutch LU is a wet multi-plate clutch provided in the power transmission path between the engine 12 and the automatic transmission 22. The lockup clutch LU is the LU clutch torque which is the torque capacity of the lockup clutch LU by the LU hydraulic PRlu which is the engagement hydraulic pressure of the pressure-regulated lockup clutch LU supplied from the hydraulic control circuit 52 provided in the vehicle 10. By changing the Tlu, the operating state can be switched.

The operating states of the lockup clutch LU include a completely released state in which the lockup clutch LU is released, a slip state in which the lockup clutch LU is engaged with slipping, and a lockup clutch LU. There is a fully engaged state, which is an engaged state. When the lockup clutch LU is completely released, the torque converter 20 is put into a torque converter state in which a torque amplification effect can be obtained. Further, when the lockup clutch LU is put into a completely engaged state, the torque converter 20 is put into a lockup state in which the pump impeller 20p and the turbine impeller 20t are integrally rotated. In the locked-up state of the torque converter 20, the power of the engine 12 is transmitted to the transmission input shaft 34 without passing through the fluid in the torque converter 20. Further, in the slip state of the lockup clutch LU, the lockup clutch LU is slip-operated so that the LU slip amount Nluslp, which is the slip amount in the lockup clutch LU, becomes the target LU slip amount Nluslptgt. The slip amount is the slip rotation speed of the clutch, which is the difference rotation speed between the input / output rotation members, which is the difference between the input / output rotation speeds of the clutch. The LU slip amount Nluslp is the difference rotation speed (= pump rotation speed Np-turbine rotation speed Nt) between the input / output rotation members of the lockup clutch LU. For example, when the vehicle 10 is in the driving state, the lockup clutch LU is in the slip state, so that the engine rotation speed Ne is suppressed from rising as compared with the completely released state, or the vehicle is muffled as compared with the fully engaged state. Sound etc. are suppressed. The pump rotation speed Np is the input rotation speed of the torque converter 20, and is the same value as the rotation speed of the crank shaft 32, that is, the engine rotation speed Ne, which is the rotation speed of the engine 12. The turbine rotation speed Nt is the output rotation speed of the torque converter 20, and is the same value as the AT input rotation speed Ni, which is the rotation speed of the transmission input shaft 34. The AT input rotation speed Ni is the input rotation speed of the automatic transmission 22.

The automatic transmission 22 is a stepped transmission that forms a part of a power transmission path between the engine 12 and the drive wheels 14. The automatic transmission 22 is a known planetary gear type automatic transmission including, for example, a plurality of sets of planetary gear devices and a plurality of engaging devices CB.

The engaging device CB is a hydraulic friction engaging device composed of a wet multi-plate or single-plate clutch or brake pressed by a hydraulic actuator, a band brake tightened by the hydraulic actuator, or the like. Each of the engaging devices CB has an engaging torque Tcb, which is a torque capacity, due to each engaging hydraulic pressure PRcb of the pressure-adjusted engaging device CB output from, for example, each solenoid valve SL or the like in the hydraulic control circuit 52. By being changed, the operating state such as the engaged state, the disengaged state, and the slip state can be switched. The engagement hydraulic pressure PRcb is an engagement pressure with respect to the engagement device CB for switching the operating state of the engagement device CB.

In the automatic transmission 22, the rotating elements of the plurality of sets of planetary gears are partially connected to each other, either directly or indirectly via the engaging device CB, or the transmission input shaft 34, the case 18, and the like. Alternatively, it is connected to the transmission output gear 24.

The automatic transmission 22 has a gear ratio γ (= AT input rotation speed Ni / AT output rotation speed No) due to engagement of any of the engagement devices CB, for example, a predetermined engagement device. It is a stepped transmission in which any one of a plurality of different gears (also referred to as a gear) is formed. The AT output rotation speed No is the rotation speed of the transmission output gear 24, that is, the output rotation speed of the automatic transmission 22.

In the automatic transmission 22, for example, a plurality of forward gears such as a first gear and a second gear, and one reverse gear are formed. The gear ratio γ of the first gear is the largest, and the gear ratio γ on the higher side becomes smaller. Further, for example, when all the engaging devices CB are released, the automatic transmission 22 is put into a neutral state in which no gear stage is formed. The neutral state of the automatic transmission 22 is, for example, a state in which the automatic transmission 22 cannot transmit power.

In the automatic transmission 22, the gear stages formed according to the accelerator operation of the driver (that is, the driver), the vehicle speed V, and the like are switched by the electronic control device 90 described later, that is, a plurality of gear stages are selectively formed. NS. For example, in the shift control of the automatic transmission 22, the shift is executed by grasping any one of the engaging devices CB, that is, the shifting is executed by switching between the engagement and the disengagement of the engaging device CB, so-called. Clutch-to-clutch shifting is performed.

The vehicle 10 includes a mechanical oil pump 54. The oil pump 54 is connected to the pump impeller 20p and is rotationally driven by the engine 12 to discharge the hydraulic oil OIL used in the power transmission device 16. The hydraulic oil OIL discharged by the oil pump 54 is supplied to the flood control circuit 52. The hydraulic control circuit 52 supplies each engaging oil pressure PRcb of the engaging device CB, LU oil pressure PRlu of the lockup clutch LU, and the like, which are adjusted based on the hydraulic oil OIL discharged by the oil pump 54. The hydraulic oil OIL is also used as a lubricating oil for lubricating each part of the power transmission device 16.

The vehicle 10 includes a wheel brake device 56. The wheel brake device 56 includes a wheel brake 58 provided on each of the drive wheel 14 and each wheel of the driven wheel (not shown), a brake master cylinder (not shown), and the like, and each wheel is controlled by the wheel brake 58. Give power. The wheel brake device 56 supplies brake hydraulic pressure to wheel cylinders (not shown) provided on each of the wheel brakes 58 in response to, for example, a driver stepping on the brake pedal 60. In the wheel brake device 56, normally, the master cylinder hydraulic pressure having a magnitude corresponding to the brake operation amount Bra, which is generated from the brake master cylinder, is supplied to the wheel cylinder as the brake hydraulic pressure. The brake pedal 60 is a brake operating member operated by the driver and provided in the vehicle 10 for operating the wheel brake 58. The brake operation amount Bra is a signal indicating the magnitude of the depression operation of the brake pedal 60 by the driver corresponding to the depression force of the brake pedal 60. In this way, the wheel brake device 56 is operated so as to apply a braking force corresponding to the operation of the brake pedal 60 by the driver to the drive wheels 14. On the other hand, in the wheel brake device 56, for example, during ABS control, skid suppression control, vehicle speed control, etc., the brake oil required for each control is supplied to the wheel cylinder in order to generate braking force by the wheel brake 58. Will be done.

Further, the vehicle 10 includes an electronic control device 90 as a controller including a control device of the vehicle 10 related to, for example, switching control of an operating state of the engagement device CB. The electronic control device 90 is configured to include, for example, a so-called microcomputer provided with a CPU, RAM, ROM, an input / output interface, etc., and the CPU follows a program stored in the ROM in advance while using the temporary storage function of the RAM. Various controls of the vehicle 10 are executed by performing signal processing. The electronic control device 90 includes computers for engine control, hydraulic control, and the like, if necessary.

The electronic control device 90 includes various sensors provided in the vehicle 10 (for example, engine rotation speed sensor 62, turbine rotation speed sensor 64, output rotation speed sensor 66, accelerator opening sensor 68, throttle valve opening sensor 70, airflow). Various signals based on the values detected by the meter 72, intake air temperature sensor 74, brake pedal sensor 76, G sensor 78, shift position sensor 80, oil temperature sensor 82, engine water temperature sensor 84, etc. (for example, engine rotation speed Ne, AT input) The turbine rotation speed Nt, which is the same value as the rotation speed Ni, the AT output rotation speed No corresponding to the vehicle speed V, the accelerator opening θacc, which is the amount of operation of the accelerator pedal 86 provided in the vehicle 10, and the opening of the electronic throttle valve. Throttle valve opening θth, intake air amount Qair of engine 12, intake air temperature THair which is intake temperature, brake on signal Bon which is a signal indicating a state where the brake pedal 60 is operated by the driver, brake operation amount Bra, The front-rear acceleration Gx and the left-right acceleration Gy of the vehicle 10, the operation position POSsh of the shift lever 88 provided in the vehicle 10, the hydraulic oil temperature THoil which is the temperature of the hydraulic oil OIL in the hydraulic control circuit 52, and the temperature of the cooling water of the engine 12. The engine cooling water temperature THEng, etc.) is supplied respectively.

Further, from the electronic control device 90, various command signals and the like (for example, for controlling the engine 12) are transmitted to each device and the like provided in the vehicle 10 (for example, the engine control device 50, the hydraulic control circuit 52, the wheel brake device 56, etc.). Engine control command signal Se, AT hydraulic control command signal Sat for controlling the operating state of the engaging device CB, LU hydraulic control command signal Sl for controlling the operating state of the lockup clutch LU, braking force by the wheel brake 58 Brake control command signal Sb, etc.) for controlling the engine is supplied. This AT hydraulic control command signal Sat is each hydraulic command for driving each solenoid valve SL that regulates each engaging hydraulic PRcb supplied to each hydraulic actuator of the engaging device CB, and is output to the hydraulic control circuit 52. Will be done.

The accelerator pedal 86 is an accelerator operating member operated by the driver for making an acceleration request to the vehicle 10. The accelerator opening degree θacc is a signal indicating the magnitude of the driver's acceleration operation, and is the amount of the driver's accelerator operation.

The shift lever 88 is a shift operation member for artificially selecting a plurality of types of shift positions in the automatic transmission 22, that is, a shift that receives a request for switching the shift position of the automatic transmission 22 by being artificially operated. It is an operating device. The shift lever 88 is operated by the driver to the operation position POSsh corresponding to the shift position of the automatic transmission 22.

The operating position POSsh includes, for example, P, R, N, D operating positions. The P operation position is a parking operation position for selecting the parking position (= P position) of the automatic transmission 22. The P position of the automatic transmission 22 is a shift position of the automatic transmission 22 in which the automatic transmission 22 is in the neutral state and the rotation of the transmission output gear 24 is mechanically blocked. The neutral state of the automatic transmission 22 is, for example, a state in which the automatic transmission 22 cannot transmit power. The state in which the rotation of the transmission output gear 24 is mechanically blocked is a state in which the transmission output gear 24 is non-rotatably fixed by a known parking lock mechanism. The R operation position is a reverse travel operation position for selecting the reverse travel position (= R position) of the automatic transmission 22. The R position of the automatic transmission 22 is a shift position of the automatic transmission 22 that enables the vehicle 10 to travel backward. The N operating position is a neutral operating position that selects the neutral position (= N position) of the automatic transmission 22, that is, the neutral position. The N position of the automatic transmission 22 is a shift position of the automatic transmission 22 in which the automatic transmission 22 is in the neutral state. The D operation position is a forward travel operation position for selecting the forward travel position (= D position) of the automatic transmission 22. The D position of the automatic transmission 22 is a shift position of the automatic transmission 22 that enables the vehicle 10 to travel forward. The P position and the N position of the automatic transmission 22 are non-traveling positions in which the automatic transmission 22 cannot transmit power. The D position and the R position of the automatic transmission 22 are traveling positions in which the automatic transmission 22 can transmit power.

The electronic control device 90 includes an engine control means, that is, an engine control unit 92, a hydraulic control means, that is, a hydraulic control unit 94, and a braking force control means, that is, a braking force control unit 96, in order to realize various controls in the vehicle 10. ..

The engine control unit 92 calculates the drive request amount for the vehicle 10 by the driver, for example, by applying the accelerator opening degree θacc and the vehicle speed V to the drive request amount map. The drive request amount map is a relationship that is experimentally or designedly obtained and stored in advance, that is, a predetermined relationship. The drive required amount is, for example, the required drive torque Trdem [Nm] in the drive wheels 14. As the drive required amount, the required driving force Fredem [N] in the drive wheels 14, the required AT output torque in the transmission output gear 24, and the like can also be used. In the calculation of the drive request amount, the AT output rotation speed No or the like may be used instead of the vehicle speed V. The engine control unit 92 controls the engine 12 so as to obtain the engine torque Te that realizes the required drive torque Trdem in consideration of the transmission loss, the auxiliary load, the gear ratio γ of the automatic transmission 22, and the like. The command signal Se is output to the engine control device 50.

The hydraulic control unit 94 functions as a transmission control means for controlling the operating state of the engaging device CB in the automatic transmission 22, that is, a transmission control unit 94a, and a lockup clutch that controls the operating state of the lockup clutch LU. It includes a control means, that is, a function as a lockup clutch control unit 94b.

The transmission control unit 94a determines the shift of the automatic transmission 22 by using, for example, a shift map having a predetermined relationship, and switches the gear stage of the automatic transmission 22 as necessary. The AT hydraulic control command signal Sat for switching the operating state and executing the shift control is output to the hydraulic control circuit 52. The shift map has, for example, a predetermined relationship having a shift line for determining the shift of the automatic transmission 22 on two-dimensional coordinates with the vehicle speed V and the required drive torque Trdem as variables. In the shift map, the AT output rotation speed No or the like may be used instead of the vehicle speed V, or the required driving force Frdem, the accelerator opening θacc, the throttle valve opening θth, or the like may be used instead of the required driving torque Trdem. You may.

In the transmission control unit 94a, the shift switching signal Ssh as the shift position switching command of the automatic transmission 22 is a non-traveling signal Spn corresponding to the non-traveling position of the automatic transmission 22, or the automatic transmission 22 travels. It is determined whether or not the travel signal Sdr corresponds to the position. When the transmission control unit 94a determines that the shift switching signal Ssh has been switched from the non-traveling signal Spn to the traveling signal Sdr, the transmission control unit 94a switches the operating state of the starting engagement device Cst from the released state to the engaged state. The AT hydraulic control command signal Sat is output to the hydraulic control circuit 52. As a result, the shift position of the automatic transmission 22 is switched from the non-traveling position to the traveling position. The non-traveling signal Spn is, for example, a shift switching signal P and a shift switching signal N. The travel signal Sdr is, for example, a shift switching signal D and a shift switching signal R. The shift switching signals Ssh P, R, N, D are basically the same as the operation position POSsh P, R, N, D, but the shift known for switching the shift position of the automatic transmission 22 When the by-wire method is adopted, the two do not always match. In this embodiment, the switching of the shift lever 88 between the P and N operating positions and the R and D operating positions, that is, the switching of the shift switching signal Ssh between the non-traveling signal Spn and the traveling signal Sdr is garage-shifted. The switching control of the operating state of the starting engagement device Cst accompanying the garage shift is referred to as garage control. Further, the garage shift from the P, N operation position to the R, D operation position, that is, the garage shift from the non-travel signal Spn to the travel signal Sdr is referred to as a P, N → R, D garage shift. Further, with the P, N → R, D garage shift, the control for switching the shift position of the automatic transmission 22 from the non-traveling position to the traveling position, that is, the operating state of the starting engaging device Cst is changed from the released state to the engaged state. The control to switch to P, N → R, D garage control is called.

The starting engaging device Cst is one of the engaging devices for forming the gear stage of the automatic transmission 22 used at the time of starting the vehicle 10 in the engaging device CB. The gear stage of the automatic transmission 22 used when the vehicle 10 starts is, for example, the first gear stage in the D operation position and the reverse gear stage in the R operation position. As described above, the automatic transmission 22 has a starting engaging device Cst in which the operating state is switched from the released state to the engaged state when the shift position of the automatic transmission 22 is switched from the non-traveling position to the traveling position. ing.

FIG. 2 is a time chart illustrating an example of a normal case of P, N → R, and D garage control. In FIG. 2, the tsh time point indicates the time point when the shift switching signal Ssh is switched from the non-traveling signal Spn (P or N) to the traveling signal Sdr (D or R). The hydraulic command in the figure is an AT hydraulic control command signal Sat for switching the starting engaging device Cst from the released state to the engaged state. This is a Cst hydraulic command for adjusting the pressure. The Cst hydraulic command is issued by a constant pressure maintenance pressure and a constant pressure maintenance pressure at a pressure lower than the rapid filling pressure, following the rapid filling pressure and the rapid filling pressure for packing in the hydraulic actuator of the starting engagement device Cst. It includes the fully engaged maintenance pressure after the coupling device Cst is engaged. When the engine 12 is operating and the vehicle 10 is stopped, when the starting engagement device Cst is in the released state, the turbine rotation speed Nt is set to be approximately the same as the engine rotation speed Ne or a value in the vicinity of the engine rotation speed Ne. However, during the transition when the starting engagement device Cst is switched from the released state to the engaged state, the turbine rotation speed Nt is reduced toward the AT output rotation speed No, and the starting engaging device Cst is in the engaged state. Then, the turbine rotation speed Nt (= No × γ) is matched with the AT output rotation speed No and is set to zero.

The lockup clutch control unit 94b determines, for example, which state the lockup clutch LU is in the operating state by using a lockup area diagram which is a predetermined relationship, and realizes the determined state. LU hydraulic control command signal Slu is output to the hydraulic control circuit 52. The lockup area diagram has a predetermined relationship having a lockup off area, a slip operation area, and a lockup on area on two-dimensional coordinates having, for example, a vehicle speed V and an accelerator opening degree θacc as variables. In the lockup area diagram, the AT output rotation speed No or the like may be used instead of the vehicle speed V, or the required drive torque Trdem, the required drive force Fridem, or the throttle valve opening θth may be used instead of the accelerator opening θacc. Etc. may be used.

Normally, the braking force control unit 96 is a brake control command for realizing a braking force of a magnitude corresponding to the driver's depression operation of the brake pedal 60 (for example, the brake operation amount Bra, the increasing speed of the brake operation amount Bra). The signal Sb is output to the wheel brake device 56. Further, the braking force control unit 96 outputs a brake control command signal Sb to the wheel brake device 56 to realize the braking force required for each control, for example, during ABS control, skid suppression control, vehicle speed control, and the like. do.

Here, when the vehicle 10 is stopped in the operating state of the engine 12 and the braking force is applied to the drive wheels 14, the starting engagement device Cst accompanies the P, N → R, and D garage shifts. When switched to the engaged state, the rotating members in the power transmission path from the transmission input shaft 34 to the drive wheels 14, that is, the power transmission path from the output rotating member of the lockup clutch LU to the drive wheels 14, are integrally connected. The rotation is stopped. At this time, since the lockup clutch LU is in the released state, a differential rotation occurs in the lockup clutch LU to prevent engine stall.

By the way, since the lockup clutch LU is a wet multi-plate clutch, drag torque is generated even when it is in the released state. The drag torque of the lockup clutch LU is the load torque of the drive system of the automatic transmission 22 or the like applied to the engine 12. Therefore, if the drag torque of the lockup clutch LU is large, an engine stall may occur during garage control for switching the starting engaging device Cst to the engaged state. The lower the hydraulic oil temperature THoil, the higher the viscosity (viscosity agrees) of the hydraulic oil OIL, so the drag torque of the lockup clutch LU tends to increase. This is noticeable when the warm THoil is extremely low. In response to the phenomenon of engine stall as described above, during the P, N → R, D garage shift, the starting engagement device Cst is engaged from the released state after the braking force applied to the drive wheels 14 is released. It is conceivable to switch to the combined state. In such a case, when the accelerator pedal 86 is depressed, that is, the accelerator is turned on after the operation of the brake pedal 60 for releasing the braking force, the starting engagement device Cst is in a completed engagement state or is engaged. If it is not in a state close to, it may lead to a shock when the vehicle starts. In this embodiment, the load torque of the drive system is referred to as a drive system load torque Tatls. The drive system load torque Tatls may be regarded as the loss torque of the automatic transmission 22.

Therefore, the transmission control unit 94a sets P, N → R, when the vehicle 10 is stopped in a state where the engine 12 is operating and a braking force is applied to the drive wheels 14 by the operation of the wheel brake device 56. When switching the operating state of the starting engagement device Cst from the released state to the engaged state with the D garage shift, that is, when switching the shift position of the automatic transmission 22 from the non-traveling position to the traveling position, the starting staff During the transition to switch the operating state of the starting engaging device Cst from the released state to the engaged state by giving the engaging flood control PRcb to the coupling device Cst, after determining that the turbine rotation speed Nt has begun to decrease, the starting staff The operation of the brake pedal 60, that is, the brake, is performed by lowering the engaging flood control PRcb with respect to the coupling device Cst to be lower than the engaging flood control PRcb before determining that the turbine rotation speed Nt has begun to decrease, and releasing the braking force applied to the drive wheels 14. The AT hydraulic control command signal Sat for controlling the starting engaging device Cst so as to maintain the operating state of the starting engaging device Cst in the slip state until the off operation is performed is sent to the hydraulic control circuit 52. Output.

In the above-mentioned control, after the turbine rotation speed Nt starts to decrease, the engagement hydraulic pressure PRcb of the starting engagement device Cst is lowered as compared with before the turbine rotation speed Nt starts to decrease, and the starting engaging device Cst slips. It is maintained in a state. This means that, for example, the engagement hydraulic pressure PRcb before the turbine rotation speed Nt starts to decrease becomes the engagement hydraulic pressure PRcb capable of switching the starting engagement device Cst to the engagement state as illustrated in FIG. Because it is.

The transmission control unit 94a determines that, for example, when the amount of decrease in the turbine rotation speed Nt with respect to the engine rotation speed Ne exceeds a predetermined decrease amount, the turbine rotation speed Nt begins to decrease. Alternatively, the transmission control unit 94a determines that, for example, when the reduction speed of the turbine rotation speed Nt exceeds a predetermined reduction speed, the turbine rotation speed Nt starts to decrease. The predetermined reduction amount and the predetermined reduction speed are predetermined threshold values that can be determined, for example, that the starting engagement device Cst has started to have the engagement torque Tcb.

FIG. 3 is a diagram illustrating the relationship between the drive system load torque Tatls and the occurrence of engine stall. In FIG. 3, the "engine torque" is the torque generated by the engine 12, that is, the engine torque Te. The "engine surplus torque" is the torque obtained by subtracting the "engine load torque" from the engine torque Te, and is represented by the engine surplus torque Tesp. The "engine load torque" is the torque used for driving an auxiliary machine or the like among the engine torque Te, and is represented by the engine load torque Teld. The engine load torque Teld is, for example, an air conditioner load torque for driving a compressor for an air conditioner (“air conditioner, etc.” in the figure) and an auxiliary load torque for driving an engine auxiliary machine (“engine auxiliary” in the figure). The machine "), the engine drag torque ("engine drag "in the figure), which is the sliding torque, that is, the drag torque during operation of the engine 12, and the like are included. On the other hand, the drive system load torque Tatls are the LU drag torque (“LU clutch drag” in the figure), which is the drag torque of the lockup clutch LU, and the torque converter capacity (“T / C” in the figure), which is the capacity of the torque converter 20. Capacity ”), oil pump drive torque (“O / P torque” in the figure), which is the torque required to drive the oil pump 54, and the like are included.

When the automatic transmission 22 is in the P position or the N position, the starting engaging device Cst is in the released state, and the total torque of the LU drag torque and the torque converter capacity is the drag of the starting engaging device Cst. Only torque (“Cst clutch drag” in the figure) is generated. The starting engagement device Cst is, for example, a wet multi-plate clutch. When the automatic transmission 22 is in the P position or the N position, the drive system load torque Tatls is lower than the engine surplus torque Tesp, and engine stall does not occur. On the other hand, when the automatic transmission 22 is in the D position or the R position and the starting engagement device Cst is in the fully engaged state, the automatic transmission 22 has both the LU drag torque and the torque converter capacity. It is made larger than the case of the P position or the N position, and as shown in the figure, when the drive system load torque Tatls exceeds the engine surplus torque Tesp, an engine stall occurs. On the other hand, when the automatic transmission 22 is in the D position or the R position and the starting engaging device Cst is in the slip state, the LU drag torque is increased according to the slip amount of the starting engaging device Cst. The total torque with the torque converter capacity is reduced, and the drive system load torque Tatls is lower than the engine surplus torque Tesp, so that the occurrence of engine stall is avoided.

Instead of performing the P, N → R, D garage control by the normal garage control, which is the normal P, N → R, D garage control as shown in FIG. 2, the braking force is always applied to the drive wheels 14. While the brake pedal 60 is being operated, that is, the brake-on operation is being performed, the starting engagement device Cst may be maintained in a slipped state by P, N → R, D garage control. In the example, P, N → R, and D garage control for maintaining the starting engagement device Cst in the slip state is performed only when the brake-on operation is performed and the occurrence of engine stall is predicted. In this embodiment, the P, N → R, and D garage controls that maintain the starting engagement device Cst in the slip state are referred to as engine stall prediction garage controls.

The electronic control device 90 further includes a state determination means, that is, a state determination unit 98 in order to execute the garage control at the time of engine stall prediction. The state determination unit 98 includes a function as an engine stall prediction determination unit, that is, an engine stall prediction determination unit 98a.

The state determination unit 98 determines whether or not the brake-on state is a state in which the brake-on operation has been performed. From a different point of view, the state determination unit 98 determines whether or not the brake is off, which is a state in which the brake on operation is not performed.

The engine stall prediction determination unit 98a determines whether or not engine stall is predicted during P, N → R, and D garage control based on whether or not the drive system load torque Tatls exceeds the engine surplus torque Tesp. That is, the engine stall prediction judgment is performed.

The engine stall prediction determination unit 98a calculates, for example, the LU drag torque, the torque converter capacity of the torque converter 20, and the oil pump drive torque, and totals them to calculate the drive system load torque Tatls. The engine stall prediction determination unit 98a calculates the shear torque Fluf using the following equation (1), for example, as the LU drag torque. In the following equation (1), "Nluslp" is the LU slip amount Nluslp, "Slu" is the contact area of the friction material in the lockup clutch LU stored in advance, and "μoil" is the hydraulic oil temperature stored in advance. The viscosity of the hydraulic oil OIL according to THoil, and "hlu" is the clearance of the friction material in the lockup clutch LU stored in advance. The engine strike prediction determination unit 98a calculates the speed ratio e (= Nt / Ne) of the torque converter 20 based on, for example, the engine rotation speed Ne and the turbine rotation speed Nt, and combines the speed ratio e with the torque converter capacity of the torque converter 20. The torque converter capacity of the torque converter 20 is calculated by applying the speed ratio e to a predetermined operating characteristic of the torque converter 20 which is a predetermined relationship. In the predetermined operating characteristics of the torque converter 20, the smaller the speed ratio e, the larger the torque converter capacity of the torque converter 20. The engine stall prediction determination unit 98a calculates the oil pump drive torque by applying the engine rotation speed Ne or the like to, for example, the oil pump characteristics having a predetermined relationship. The hydraulic oil temperature THoil may be added to the calculation of the oil pump drive torque.

Tluf = Nluslp x Slu x μoil / hlu ・ ・ ・ (1)

The engine stall prediction determination unit 98a calculates, for example, the engine torque Te and the engine load torque Teld, respectively, and subtracts the engine load torque Teld from the engine torque Te to calculate the engine surplus torque Tesp. The engine stall prediction determination unit 98a calculates an estimated value of engine torque Te by applying, for example, the throttle valve opening degree θth and the engine rotation speed Ne to a known engine torque map having a predetermined relationship. In calculating the engine torque Te, the intake air amount Qair may be used instead of the throttle valve opening degree θth. Further, when the intake air temperature THair is low, the engine torque Te becomes large because the air density is high as compared with when the intake air temperature THair is high. The engine stall prediction determination unit 98a may correct the estimated value of the engine torque Te by using, for example, the air density calculated based on the intake air temperature THair or the atmospheric pressure. The engine stall prediction determination unit 98a calculates, for example, the air conditioner load torque, the auxiliary machine load torque, and the engine drag torque, and totals them to calculate the engine load torque Teld. The engine stall prediction determination unit 98a calculates the air conditioner load torque according to the operating state of the compressor for the air conditioner, for example, using the compressor characteristics which are a predetermined relationship. The engine stall prediction determination unit 98a calculates the auxiliary machine load torque by applying the engine rotation speed Ne or the like to the engine auxiliary machine characteristics having a predetermined relationship, for example. The engine stall prediction determination unit 98a calculates the engine drag torque based on, for example, the engine cooling water temperature THEng and the elapsed time from the engine start. As time elapses from the start of the engine, the temperature of the sliding portion rises, the sliding resistance is reduced, and the engine drag torque is reduced. In calculating the engine drag torque, the temperature of the engine oil may be used instead of the engine cooling water temperature THeng.

When the transmission control unit 94a determines that the shift switching signal Ssh has been switched from the non-travel signal Spn to the travel signal Sdr, the state determination unit 98 determines that the brake is not on, or predicts engine stall. If the determination unit 98a determines that the drive system load torque Tatls does not exceed the engine surplus torque Tesp and the occurrence of engine stall is not predicted, P, N → R, D garage control is performed by normal garage control. ..

When the transmission control unit 94a determines that the shift switching signal Ssh has been switched from the non-travel signal Spn to the travel signal Sdr, the state determination unit 98 determines that the brake is on, and the engine stall prediction determination unit 98a When it is determined that the drive system load torque Tatls exceeds the engine surplus torque Tesp and the occurrence of engine stall is predicted, P, N → R, and D garage control is performed by the garage control at the time of engine stall prediction. The transmission control unit 94a predicts that an engine stall will occur when the state determination unit 98 determines that the brake is off during the execution transition of the garage control at the time of engine stall prediction, or when the engine stall prediction determination unit 98a determines that the engine stall occurs. If it is determined that the engine stall is not performed, the P, N → R, D garage control is switched to the normal garage control, or the garage control at the time of engine stall prediction is terminated and the starting engagement device Cst is changed from the slip state to the engaged state. Switch to.

The transmission control unit 94a is determined by the state determination unit 98 to be in the brake-off state during the execution transition of the garage control at the time of engine stall prediction, and after switching the starting engagement device Cst from the slip state to the engagement state, When the state determination unit 98 determines again that the brake is on, the start engagement device Cst is provided on the condition that the engine stall is predicted to occur by the engine stall prediction determination unit 98a. Is switched from the engaged state to the slip state or the released state. As a result, the occurrence of engine stall due to the re-brake-on operation is avoided.

The transmission control unit 94a controls the CST slip amount Ncstslp, which is the slip amount in the starting engagement device Cst, in the garage control at the time of engine stall prediction. The transmission control unit 94a has, for example, a slip state of the starting engaging device Cst with a predetermined CST slip amount Ncstslp so that a delay in switching to the engaging state of the starting engaging device Cst does not occur after the brake off operation. To control. Alternatively, the transmission control unit 94a is for suppressing a decrease in durability due to a heat load of the friction fastening element constituting the starting engaging device Cst during a control transition in which the starting engaging device Cst is in a slip state, for example. The slip state of the starting engagement device Cst is controlled by a predetermined CST slip amount Ncstslp. Alternatively, the transmission control unit 94a suppresses a decrease in the friction coefficient of the friction material due to the heat load of the friction fastening element constituting the starting engaging device Cst during a control transition in which the starting engaging device Cst is in a slip state, for example. The slip state of the starting engagement device Cst is controlled by a predetermined CST slip amount Ncstslp.

The transmission control unit 94a is predetermined to suppress a decrease in durability due to a heat load of the friction fastening element constituting the starting engaging device Cst during a control transition in which the starting engaging device Cst is in a slip state, for example. When the slip control time has elapsed, the control for putting the starting engaging device Cst into the slip state may be terminated and the starting engaging device Cst may be switched to the engaged state. Alternatively, the transmission control unit 94a suppresses a decrease in durability due to a heat load of the friction fastening element constituting the starting engaging device Cst during a control transition in which the starting engaging device Cst is in a slip state, for example. , The supply of hydraulic oil OIL, which is a lubricating oil for lubricating the starting engagement device Cst, may be increased.

The direction in which the vehicle 10 travels may be the uphill direction. In such a case, when the starting engagement device Cst is switched from the slip state to the engagement state due to the brake-off operation during the execution transition of the garage control at the time of engine stall prediction, the slope is such that the vehicle 10 cannot climb the slope. If so, the drive wheels 14 may not rotate and an engine stall may occur. Even if engine stall is predicted during the P, N → R, D garage shift, if the vehicle 10 cannot climb the slope after the brake-off operation, the P, N → R, D garage control is not executed. It is preferable to keep the starting engagement device Cst in the released state.

When the engine stall prediction determination unit 98a determines that the engine stall is predicted, the state determination unit 98 uses the engine surplus torque Tesp, the slope of the travel path calculated based on the front-rear acceleration Gx, and the like. It is determined whether or not the vehicle 10 is unable to climb the slope. That is, the state determination unit 98 determines whether or not the vehicle 10 is climbing a slope that cannot be climbed.

When the transmission control unit 94a determines that the shift switching signal Ssh has been switched from the non-travel signal Spn to the travel signal Sdr, the state determination unit 98 determines that the brake is on, and the engine stall prediction determination unit 98a Even if it is determined that the engine stall is predicted to occur, if the state determination unit 98 determines that the vehicle 10 cannot climb the slope, P, N → R, D garage control is performed. Do not execute and keep the starting engagement device Cst in the released state. While the state determination unit 98 determines that the vehicle 10 cannot climb the slope, the transmission control unit 94a is in charge of starting until the engine stall prediction determination unit 98a determines that the occurrence of engine stall is not predicted. The combiner Cst is maintained in the released state.

If the starting engagement device Cst is in the released state when the vehicle 10 cannot climb a slope, there is a concern that the vehicle 10 will slide down when the brake-off operation is performed. On the other hand, when the starting engagement device Cst is maintained in the released state by the transmission control unit 94a, the braking force control unit 96 of the vehicle 10 with respect to the drive wheels 14 and the driven wheels (not shown). A brake hold is performed to apply the braking force required to prevent sliding down.

FIG. 4 is a flowchart illustrating a main part of the control operation of the electronic control device 90, in which the automatic transmission 22 is shifted when the vehicle is stopped in the operating state of the engine 12 and the braking force applied to the drive wheels 14. It is a flowchart explaining the control operation for suppressing an engine stall even when the hydraulic oil OIL is extremely low temperature when switching a position from a non-running position to a running position, and is executed repeatedly, for example. FIG. 5 is a diagram showing an example of a time chart when the control operation shown in the flowchart of FIG. 4 is executed.

In FIG. 4, first, in step S10 corresponding to the function of the transmission control unit 94a (hereinafter, step is omitted), it is determined whether the shift switching signal Ssh is the traveling signal Sdr (D or R). If the judgment of S10 is denied, this routine is terminated. If the determination in S10 is affirmed, it is determined in S20 corresponding to the function of the state determination unit 98 whether or not the brake is on. If the determination in S20 is affirmed, the engine stall prediction determination is performed in S30 corresponding to the function of the engine stall prediction determination unit 98a based on whether or not the drive system load torque Tatls exceeds the engine surplus torque Tesp. If the judgment of S20 is denied, or if the judgment of S30 is denied, the P, N → R, D garage control is the normal garage control in S40 corresponding to the function of the transmission control unit 94a. It will be done at. If the determination in S30 is affirmed, it is determined in S50 corresponding to the function of the state determination unit 98 whether or not the vehicle 10 is climbing to the extent that it cannot climb. If the judgment of S50 is affirmed, in S60 corresponding to the functions of the transmission control unit 94a and the braking force control unit 96, the slip state or engagement of the starting engagement device Cst by P, N → R, D garage control is performed. The switching to the combined state is not executed, the starting engaging device Cst is maintained in the released state, and the brake hold is activated. Following this S60, the above S30 is executed. On the other hand, if the judgment of S50 is denied, in S70 corresponding to the function of the transmission control unit 94a, P, N → R, D garage control is performed by garage control at the time of engine stall prediction, and engagement for starting is performed. The device Cst is maintained in a slipped state. Next, in S80 corresponding to the function of the state determination unit 98, it is determined whether or not the brake is off. When the determination of S80 is denied, the engine stall prediction determination is performed in S90 corresponding to the function of the engine stall prediction determination unit 98a in the same manner as in the above S30. If the determination of S90 is affirmed, the above S70 is executed. If the determination in S80 is affirmed, or if the determination in S90 is denied, slip control that puts the starting engagement device Cst in a slip state in S100 corresponding to the function of the transmission control unit 94a. Is released, and the starting engagement device Cst is switched to the engaged state.

FIG. 5 shows an example of an embodiment in which the P, N → R, and D garage controls are performed by the garage control at the time of engine stall prediction. In FIG. 5, the time point t1 indicates the time point when the shift switching signal Ssh is switched from the non-traveling signal Spn (P or N) to the traveling signal Sdr (D or R). The engine stall prediction determination has been performed since the phase [1] before the time point t1, and at the time point t1, it is determined whether or not to implement the garage control at the time of engine stall prediction after the phase [3]. In this embodiment, it is determined that the occurrence of engine stall is predicted, and it is determined that the garage control at the time of engine stall prediction is performed. In the phase [2] from the time point t1 to the time point t2, the garage control is usually performed so as to secure the driving force for starting as quickly as possible. When the reduction speed of the turbine rotation speed Nt exceeds the predetermined reduction speed, the hydraulic command of the starting engagement device Cst is reduced (see the time t2), and the phase up to the time t3 when the brake is off is set [3]. Then, the starting engagement device Cst is maintained in the slipped state. The reason why the hydraulic command is temporarily set to zero at t2 is to quickly reduce the turbine rotation speed Nt. After that, when the hydraulic command is set to a constant value, the starting engagement device Cst is maintained in the slip state. The slip amount is set in consideration of the decrease in the durability of the friction material of the starting engagement device Cst while reducing the loss torque (= drive system load torque Tatls) of the automatic transmission 22 so as to avoid the occurrence of engine stall. The value of the oil pressure command is set to. In the phase [4] from the time t3 when the brake is off, the hydraulic command of the starting engaging device Cst is raised, and the starting engaging device Cst is switched to the engaged state to prepare for starting. The increase in the hydraulic command of the starting engagement device Cst is adjusted to a value that suppresses the shock. In the phase [4], while it is determined that the engine stall is expected to occur, the value of the hydraulic command of the starting engagement device Cst becomes a certain pressure or higher in case the brake is turned on again. Not set high. When the brake is turned on again, the hydraulic command of the starting engaging device Cst is lowered at the same time as the braking is turned on, and the starting engaging device Cst is slipped or released before the engine stalls. It is considered to be in a state. In this embodiment, the accelerator is turned on at t4 while the brake is off. In the phase [5] from the time t4, the vehicle travels according to the accelerator-on operation. In the phase [5] as well as in the phase [4], while it is determined that the engine stall is expected to occur, the oil pressure command of the starting engagement device Cst is prepared in case the brake is turned on. The value of is not set higher than a certain pressure and the brake is turned on, and at the same time, the hydraulic command of the starting engaging device Cst is lowered, and the starting engaging device Cst is in a slipped state or before the engine stalls. It is released. In this embodiment, the brake-on operation is performed at t5. In the phase [6] from the time t5, the hydraulic command of the starting engagement device Cst is lowered to avoid engine stall when the vehicle is stopped in the brake-on state. In this embodiment, the starting engagement device Cst is in the slip state, but it may be in the released state. In order to respond to the brake-on operation, the hydraulic command of the starting engagement device Cst is lowered with the aim of releasing the starting engagement device Cst on the premise that the engine stall is not generated, but the engine stall. If this can be avoided, it is desirable to shift the starting engagement device Cst to the slip state. In the phase [6], if it is determined that the occurrence of engine stall is not predicted, the engaged state of the starting engaging device Cst is maintained as it is.

As described above, according to the present embodiment, when the vehicle 10 is stopped in the operating state of the engine 12 and the braking force applied to the drive wheels 14, the shift position of the automatic transmission 22 is not traveled. When switching from the position to the running position, the turbine rotation speed during the transition in which the engagement hydraulic pressure PRcb is applied to the starting engagement device Cst to switch the operating state of the starting engagement device Cst from the released state to the engaged state. After it was determined that Nt had begun to decrease, the engagement hydraulic pressure PRcb with respect to the starting engagement device Cst was made lower than the engagement hydraulic pressure PRcb before it was determined that the turbine rotation speed Nt had begun to decrease, and was applied to the drive wheels 14. Since the starting engaging device Cst is controlled so as to maintain the operating state of the starting engaging device Cst in the slip state until the brake-off operation for releasing the braking force is performed, the transmission input shaft 34 The difference rotation between the drive wheel 14 and the drive wheel 14 is allowed, the LU drag torque is reduced, and the drive system load torque Turbs is reduced. Therefore, when the shift position of the automatic transmission 22 is switched from the non-traveling position to the traveling position when the vehicle is stopped in the operating state of the engine 12 and the braking force is applied to the drive wheels 14, when the hydraulic oil OIL is extremely low. Even so, engine stall can be suppressed.

The period of waiting for switching the operating state of the starting engaging device Cst to the fully engaged state is until the brake-off operation for releasing the braking force is performed, and in that period, the starting engaging device Since the operating state of the Cst is maintained in the slip state, the operating state of the starting engagement device Cst is quickly switched from the slip state to the fully engaged state after the brake-off operation. As a result, when the accelerator-on operation is performed after the brake-off operation, the starting engagement device Cst is likely to be in a state where the engagement is completed or a state close to the engagement completion, so that the occurrence of a shock at the time of starting the vehicle is suppressed. Will be done. As described above, according to the present embodiment, the engine stall resistance is improved while the deterioration of the drivability performance is suppressed.

Although the examples of the present invention have been described in detail with reference to the drawings, the present invention also applies to other aspects.

For example, in the above-described embodiment, the lockup clutch LU provided in the torque converter 20 has been exemplified as a wet multi-plate clutch provided in the power transmission path between the engine 12 and the automatic transmission 22. It is not limited to the mode. The wet multi-plate clutch provided in the power transmission path between the engine 12 and the automatic transmission 22 is, for example, a torque converter 20 with a lockup clutch LU, which is a starting engagement device provided in the automatic transmission 22. It may be replaced with a simple wet multi-plate clutch Cw such as Cst. In such a case, when the vehicle 10 is stopped in the brake-on state, the wet multi-plate clutch Cw is in the released state as in the lockup clutch LU. When the vehicle starts, for example, the wet multi-plate clutch Cw is slid and controlled toward the engaged state.

Further, in the above-described embodiment, the starting engaging device Cst may be any engaging device for forming the gear stage of the automatic transmission 22 used when the vehicle 10 of the engaging device CB starts. For example, one of the engaging devices that can easily control the slip state at the time of garage control at the time of engine stall prediction may be used. Further, as the gear stage of the automatic transmission 22 used when the vehicle 10 starts, the first speed gear stage is exemplified in the D operation position, but for example, in the slippery road surface condition, the second speed gear stage starts the vehicle 10. Sometimes used.

Further, in the above-described embodiment, a plurality of forward gear stages and one reverse gear stage are formed as automatic transmissions that form a part of the power transmission path between the engine 12 and the drive wheels 14. The planetary gear type automatic transmission 22 is illustrated, but the present invention is not limited to this mode. The automatic transmission 22 may be a stepped transmission in which a plurality of gear stages are selectively formed by selectively engaging a plurality of engaging devices. Alternatively, for example, the automatic transmission forming a part of the power transmission path between the engine 12 and the drive wheels 14 may be a known belt-type continuously variable transmission or the like. When the automatic transmission is a belt-type continuously variable transmission, the starting engagement device switches the operating state from the released state to the engaged state when the shift position of the automatic transmission is switched from the non-traveling position to the traveling position. Is provided independently of the continuously variable transmission, but is included in a known forward / backward switching device that constitutes an automatic transmission together with a belt-type continuously variable transmission, for example, a forward clutch or a reverse gear. Brake etc. In a broad sense, the concept of this belt-type continuously variable transmission includes a chain-type continuously variable transmission.

Further, in the above-described embodiment, the power of the engine 12 is transmitted to the automatic transmission 22 via the torque converter 20, but the present invention is not limited to this mode. For example, instead of the torque converter 20, another fluid type transmission device such as a fluid coupling having no torque amplification action may be used.

It should be noted that the above is only one embodiment, and the present invention can be implemented in a mode in which various changes and improvements are made based on the knowledge of those skilled in the art.

10: Vehicle 12: Engine 14: Drive wheels 22: Automatic transmission 34: Transmission input shaft (input rotating member)
56: Wheel brake device 60: Brake pedal (brake operating member)
90: Electronic control device (control device)
Cst: Starting engagement device LU: Lock-up clutch (wet multi-plate clutch)

Claims (1)

An engine, an automatic transmission forming a part of a power transmission path between the engine and the drive wheels, and a wet multi-plate clutch provided in the power transmission path between the engine and the automatic transmission. The automatic transmission is provided with a wheel brake device that is operated so as to apply a braking force corresponding to the operation of the brake operating member by the driver to the drive wheels, and the shift position of the automatic transmission is the automatic transmission. When the machine is switched from the non-traveling position where power transmission is not possible to the traveling position where the automatic transmission is capable of power transmission, the operating state is switched from the released state to the engaged state. A control device for a vehicle that has a device,
The shift position is switched from the non-traveling position to the traveling position when the vehicle is stopped in the operating state of the engine and the braking force is applied to the drive wheels by the operation of the wheel braking device. In the case, the rotation of the input rotating member of the automatic transmission is performed during a transition in which an engaging pressure is applied to the starting engaging device to switch the operating state of the starting engaging device from the released state to the engaged state. After it is determined that the speed has begun to decrease, the engagement pressure with respect to the starting engagement device is made lower than the engagement pressure before it is determined that the rotation speed of the input rotating member of the automatic transmission has begun to decrease. A vehicle characterized in that the starting engaging device is controlled so as to maintain the operating state of the starting engaging device in a slip state until the brake operating member is operated to release the power. Control device.

Images