Vehicle control system

Abstract

To inhibit, in a vehicle having a transmission that transmits power via a frictional engagement device, the frictional engagement device of the transmission from slipping when the vehicle moves backward.SOLUTION: A periodic increase / decrease change in the output rotation speed of an automatic transmission is detected during backward traveling, and when the increase / decrease change satisfies an input torque limit start condition (S1) which is a protection execution condition, input torque limit control (S2 to S4) is executed as protection control for suppressing slippage of a frictional engagement device that is engaged during backward traveling, so that deterioration in durability due to slippage of the frictional engagement device or the like is suppressed. In particular, the periodic increase / decrease change in the output rotation speed of the automatic transmission occur due to the slip grip of rear wheels. Therefore, by suitably setting the protection execution condition, it is possible to properly suppress slippage of the frictional engagement device, and suppress deterioration in vehicle quality such as driving performance caused by execution of excessive protection control more than necessary.SELECTED DRAWING: Figure 5

Description

Technical Field

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[0001] The present invention relates to a control device for a vehicle, and particularly to a technique for protecting a friction engagement device of a transmission.

Background Art

[0002] Patent Document 1 proposes a technique for increasing the belt clamping pressure to prevent belt slippage when a vehicle equipped with a belt-type continuously variable transmission reverses downhill and climbs uphill.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The technique described in Patent Document 1 is a technique specific to a vehicle equipped with a belt-type continuously variable transmission. However, it has been found that in a vehicle equipped with a transmission that transmits power through a friction engagement device such as a clutch, the friction engagement device of the transmission may slip when the vehicle reverses downhill and climbs uphill. That is, when the vehicle starts, vertical vibration of the drive wheels called power hop may occur due to the action of the suspension device. However, when a rear-wheel drive vehicle reverses downhill and climbs uphill, the frictional force between the drive wheels and the road surface becomes small. Therefore, due to the change in the frictional force during the vertical movement of the drive wheels caused by power hop, slip-grip in which the drive wheels repeatedly slip and grip is likely to occur. When the rotational speed of the drive wheels periodically increases and decreases due to this slip-grip, a large load is applied to the friction engagement device of the transmission in relation to the input torque from the power source, and slip may occur.

[0005] The present invention was made against the above circumstances, and its objective is to suppress slippage of the friction engagement device of a transmission when the vehicle is moving in reverse, in a vehicle having a transmission that transmits power via a friction engagement device. [Means for solving the problem]

[0006] The present invention relates to a vehicle control device in which (a) the vehicle is driven by the rotational drive of the rear wheels by a drive force source, and (b) a fluid transmission device and a transmission that transmits power via a friction engagement device are arranged in series in the power transmission path between the drive force source and the rear wheels, from the drive force source side, (c) when a periodic increase or decrease in the rotational speed of the output shaft of the transmission is detected during reverse driving, and when the increase or decrease in the rotational speed of the friction engagement device satisfies predetermined protection execution conditions in which slippage of the friction engagement device is predicted, the component protection control unit performs protection control to suppress slippage of the friction engagement device of the transmission that is engaged during reverse driving, and (d) the component protection control unit As the aforementioned protective control, This is characterized by performing at least one of the following: a control that limits the input torque of the transmission and a control that increases the engagement force of the friction engagement device. [Effects of the Invention]

[0007] In such vehicle control systems, the periodic increase or decrease in the rotational speed of the transmission's output shaft is detected during reverse driving, and this increase or decrease in speed is detected. Slip is predicted in the friction engagement device. When the protection execution conditions are met, protective control is executed to suppress slippage of the friction engagement device, thereby suppressing the deterioration of durability caused by slippage of the friction engagement device. In particular, periodic fluctuations in the rotational speed of the transmission output shaft are caused by slip-grip of the rear wheels, so by appropriately setting the protection execution conditions, slippage of the friction engagement device can be appropriately suppressed when protection is necessary, and excessive protective control that would impair vehicle quality such as driving performance can be prevented. [Brief explanation of the drawing]

[0008] [Figure 1]This diagram illustrates a schematic configuration of a drive system for a hybrid electric vehicle equipped with a control device, which is one embodiment of the present invention. The diagram also shows the control functions for various types of control and the main components of the control system. [Figure 2] This is a schematic diagram illustrating an example of an automatic transmission found in the hybrid electric vehicle shown in Figure 1. [Figure 3] Figure 2 is a diagram illustrating the relationship between the multiple shift ranges and multiple forward gear stages in the D range of the automatic transmission and the engagement / disengagement state of the friction engagement device. [Figure 4] Figure 1 shows an example of a hydraulic control circuit in a hybrid electric vehicle, illustrating the part related to the friction engagement device of the automatic transmission. [Figure 5] Figure 1 is a flowchart that specifically illustrates the input torque limiting control performed by the component protection control unit functionally included in the electronic control unit of the hybrid electric vehicle. [Figure 6] Figure 1 is a flowchart illustrating the line pressure maximum pressure control performed by the component protection control unit functionally included in the electronic control unit of the hybrid electric vehicle. [Figure 7] Figures 5 and 6 illustrate the relationship between the implementation of input torque limiting control and maximum line pressure control, the type of driving range, and the implementation of traction control. [Figure 8] Figures 1 and 2 to 4 illustrate the torque acting on the clutch C3 of the automatic transmission when the rear wheels of the hybrid electric vehicle experience slip-grip due to power hop. [Figure 9] This is an example of a time chart showing the changes in the operating state of each part when input torque limiting control and line pressure maximum pressure control are performed according to the flowcharts in Figures 5 and 6 during reverse starting of the hybrid electric vehicle shown in Figure 1. [Figure 10] This is an example of a time chart showing the changes in the operating state of each part in a conventional case where neither the input torque limit control shown in Figure 5 nor the line pressure maximum pressure control shown in Figure 6 is performed when a hybrid electric vehicle shown in Figure 1 starts moving in reverse. [Modes for carrying out the invention]

[0009] The present invention is suitably applied to FR (front-engine, rear-drive) type rear-wheel drive vehicles in which the power source, such as an engine, is mounted at the front of the vehicle. However, it can also be applied to rear-wheel drive vehicles in which the power source is mounted in the center or rear of the vehicle, and to front and rear wheel drive vehicles in which the front wheels are also driven as drive wheels. The power source may be an engine alone, or it may be applied to hybrid electric vehicles equipped with an engine and an electric motor as power sources, or to electric vehicles that run solely on an electric motor. The transmission is configured to include at least a friction engagement device, such as a hydraulic type, that is engaged when driving in reverse. For example, a stepped transmission such as a planetary gear type or parallel shaft type having a D range for forward driving and an R range for reverse driving is suitably used. A forward / reverse switching device that simply switches between forward and reverse is also acceptable, or a combination of a forward / reverse switching device and a continuously variable transmission such as a belt type is also acceptable. A transmission that performs reverse driving by the reverse rotation of the electric motor, which is the power source, may also be used. Fluid-type power transmission systems are devices that transmit power through fluid. Torque converters, which have a torque amplification effect, are preferably used, but fluid couplings and the like can also be used.

[0010] The protection execution conditions for which the component protection control unit performs protection control are determined, for example, based on the rotational acceleration of the output shaft corresponding to the output side iner shuttle of the transmission. For example, it may be determined that the protection execution conditions are met when a rapid deceleration occurs where the deceleration value of the rotational acceleration is less than or equal to a predetermined protection judgment acceleration, and when the state exceeds that protection judgment acceleration, and the rapid deceleration occurs again within a predetermined repetition judgment time. As protection execution conditions, it is sufficient to determine whether the deceleration value of the rotational acceleration is less than or equal to a predetermined protection judgment acceleration, or whether the absolute value of the rotational acceleration is greater than or equal to a predetermined protection judgment acceleration. In addition, protection execution conditions can be determined based on factors other than rotational acceleration, such as the amplitude or period of periodically increasing or decreasing fluctuations in rotational speed, allowing for various ways in which slip of the friction engagement device can be predicted. Furthermore, the component protection control unit may also define protection execution conditions other than those related to the rotational speed of the output shaft, such as the input torque of the transmission being greater than or equal to a predetermined protection judgment torque. The protective control performed by the component protection control unit preferably includes at least one of the following: input torque limiting control, which limits the input torque of the transmission; and engagement force increase control, which increases the engagement force of the friction engagement device. The engagement force increase control is configured to set the line pressure to the maximum pressure, for example, if the friction engagement device is hydraulic and engaged by line pressure, but it may also be sufficient to simply increase the engagement force of a specific friction engagement device. The protective control by the component protection control unit should ideally be performed during reverse driving when rear wheel slip-grip is likely to occur due to power hopping, but it can also be performed during forward driving. [Examples]

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, the drawings have been simplified or modified as appropriate for illustrative purposes, and the dimensional ratios, angles, shapes, etc. of each part are not necessarily depicted accurately.

[0012] Figure 1 is a schematic diagram of the drive system of a hybrid electric vehicle 10 (hereinafter simply referred to as electric vehicle 10) equipped with an electronic control device 90 as a control device, which is one embodiment of the present invention. The diagram also shows the control functions for various controls related to the electric vehicle 10 and the main parts of the control system. In Figure 1, the electric vehicle 10 is a parallel-type hybrid electric vehicle equipped with an engine 12 and a rotating machine MG as a driving force source for driving. The electric vehicle 10 is also equipped with a power transmission device 16 provided in the power transmission path between the engine 12 and the drive wheels 14. The drive wheels 14 are the left and right rear wheels, and the electric vehicle 10 is an FR-type rear-wheel drive vehicle with the engine 12 and rotating machine MG mounted on the front side of the vehicle.

[0013] Engine 12 is an internal combustion engine such as a gasoline engine or a diesel engine. Engine torque Te, which is the output torque of engine 12, is controlled by an electronic control device 90 through engine control equipment 50, which includes a throttle actuator, fuel injection device, ignition device, etc. Rotating machine MG is a motor generator that has the function of an electric motor that generates mechanical power from electricity and a generator that generates electricity from mechanical power, for example a three-phase AC synchronous motor, and is connected to a battery 54 via an inverter 52. Rotating machine MG's torque Tmg and rotational speed Nmg are controlled by the inverter 52 controlled by the electronic control device 90. Rotating machine MG generates power for driving using electricity supplied from the battery 54 via the inverter 52, either in place of or in addition to engine 12. The rotating machine MG also generates electricity by regenerative control, which allows it to function as a generator when it is rotated by the power of the engine 12 or the driven force input from the drive wheels 14, and also generates regenerative braking when connected to the drive wheels 14. The electricity generated by the rotating machine MG is stored in the battery 54 via the inverter 52. The battery 54 is an energy storage device that sends and receives power to the rotating machine MG.

[0014] The power transmission device 16 includes, within a case 18, which is a non-rotating member attached to the vehicle body, a K0 clutch 20, a torque converter 22, and an automatic transmission 24 in series from the engine 12 side, and a rotary electric machine MG is connected to the power transmission path between the K0 clutch 20 and the torque converter 22. The K0 clutch 20 is a clutch provided between the engine 12 and the rotary electric machine MG in the power transmission path between the engine 12 and the drive wheels 14, and is an engine disconnection / connection device that connects and disconnects between the rotary electric machine MG and the engine 12. The torque converter 22 is provided between the rotary electric machine MG and the automatic transmission 24, and is a fluid transmission device that transmits power via hydraulic oil OIL, which is a fluid, and is connected to the engine 12 via the K0 clutch 20. The automatic transmission 24 is connected to the torque converter 22, and is a transmission provided in series with the torque converter 22 between the engine 12 and the rotary electric machine MG and the drive wheels 14. The power transmission device 16 includes a propeller shaft 28 connected to an output shaft 26, which is an output rotating member of the automatic transmission 24, a differential gear 30 connected to the propeller shaft 28, a pair of drive shafts 32 connected to the differential gear 30, and the like. Further, the power transmission device 16 includes an engine connection shaft 34 that connects the engine 12 and the K0 clutch 20, an MG connection shaft 36 that connects the K0 clutch 20 and the torque converter 22, and the like, and the rotor of the rotary electric machine MG is connected to the MG connection shaft 36.

[0015] The K0 clutch 20 is a wet or dry (wet in the embodiment) friction engagement device constituted by a multi-plate or single-plate clutch pressed by a hydraulic actuator. The K0 clutch 20 has its control state, such as an engaged state or a released state, switched by changing the K0 torque Tk0, which is the torque capacity of the K0 clutch 20, by the regulated K0 hydraulic pressure PRk0 supplied from a hydraulic control circuit 56. In the engaged state of the K0 clutch 20, the rotor of the rotary electric machine MG, the pump impeller 22a, and the engine 12 are integrally rotated via the engine connection shaft 34. In the released state of the K0 clutch 20, the power transmission between the rotor of the rotary electric machine MG, the pump impeller 22a, and the engine 12 is interrupted, and the engine 12 can be stopped.

[0016] The torque converter 22 includes a pump impeller 22a connected to the MG connecting shaft 36 and a turbine impeller 22b connected to an input shaft 38 which is an input rotating member of the automatic transmission 24. The pump impeller 22a is connected to the engine 12 via the K0 clutch 20 and is directly connected to the rotating electrical machine MG. The pump impeller 22a is an input member of the torque converter 22, and the turbine impeller 22b is an output member of the torque converter 22. The MG connecting shaft 36 is also an input rotating member of the torque converter 22. The input shaft 38 is also an output rotating member of the torque converter 22 integrally formed with a turbine shaft that is rotationally driven by the turbine impeller 22b. The torque converter 22 includes a LU clutch 40 that connects the pump impeller 22a and the turbine impeller 22b. The LU clutch 40 is a direct connection clutch that connects the input and output rotating members of the torque converter 22, that is, a lock-up clutch.

[0017] The operating state, that is, the control state of the LU clutch 40 is switched by changing the LU clutch torque Tlu, which is the torque capacity of the LU clutch 40, by the regulated LU hydraulic pressure PRlu supplied from the hydraulic control circuit 56. The control states of the LU clutch 40 include a fully open state in which the LU clutch 40 is released, a slip state in which the LU clutch 40 is engaged with slippage, and a fully engaged state in which the LU clutch 40 is engaged. When the LU clutch 40 is in the fully open state, the torque converter 22 is in a torque converter state in which a torque amplification effect can be obtained. Also, when the LU clutch 40 is in the fully engaged state, the torque converter 22 is in a lock-up state in which the pump impeller 22a and the turbine impeller 22b are integrally rotated.

[0018] The automatic transmission 24 is a known planetary gear type automatic transmission comprising, for example, one or more sets of planetary gears and a plurality of engagement devices CB. The engagement devices CB are hydraulic friction engagement devices consisting of multi-plate or single-plate clutches and brakes pressed by hydraulic actuators, and band brakes tightened by hydraulic actuators. Each engagement device CB is switched between engaged and disengaged states by changing its respective torque capacity, the CB torque Tcb, which is supplied by a regulated CB hydraulic pressure PRcb from a hydraulic control circuit 56.

[0019] The automatic transmission 24 is a stepped transmission that can form multiple forward and reverse gears with different gear ratios γ (= input rotational speed Ni / output rotational speed No) by engaging any of the engagement devices CB. The automatic transmission 24 is switched by the electronic control device 90 according to the driver's (= driver's) accelerator operation and driving conditions such as vehicle speed V, that is, multiple gears are selectively formed. Also, when all of the engagement devices CB are released, it becomes neutral, which cuts off power transmission. The input rotational speed Ni is the rotational speed of the input shaft 38 and is the input rotational speed of the automatic transmission 24. The input rotational speed Ni is the same as the turbine rotational speed Nt, which is the output rotational speed of the torque converter 22. The output rotational speed No is the rotational speed of the output shaft 26 and is the output rotational speed of the automatic transmission 24.

[0020] In the power transmission system 16, when the K0 clutch 20 is engaged, the power output from the engine 12 is transmitted from the engine connecting shaft 34 to the drive wheels 14 via the K0 clutch 20, MG connecting shaft 36, torque converter 22, automatic transmission 24, propeller shaft 28, differential gear 30, and drive shaft 32 in sequence. Also, regardless of the control state of the K0 clutch 20, the power output from the rotating machine MG is transmitted from the MG connecting shaft 36 to the drive wheels 14 via the torque converter 22, automatic transmission 24, propeller shaft 28, differential gear 30, and drive shaft 32 in sequence. The left and right drive wheels 14 are each attached to the vehicle body via a suspension system 66.

[0021] The electric vehicle 10 is equipped with a mechanical oil pump MOP58, an electric oil pump EOP60, a pump motor 62, and the like. The MOP58 is connected to the pump impeller 22a and is rotationally driven by a power source (engine 12, rotary machine MG) to discharge hydraulic oil used in the power transmission device 16. The pump motor 62 is an electric motor dedicated to the EOP60 for rotationally driving the EOP60. The EOP60 is rotationally driven by the pump motor 62 to discharge hydraulic oil, and can discharge hydraulic oil at any timing, including when the electric vehicle 10 is stopped. The hydraulic oil discharged by the MOP58 and EOP60 is supplied to the hydraulic control circuit 56. The hydraulic control circuit 56 outputs CB hydraulic pressure PRcb, K0 hydraulic pressure PRk0, LU hydraulic pressure PRlu, etc., which are adjusted based on the hydraulic oil discharged by the MOP58 and / or EOP60. The hydraulic fluid (OIL) is supplied to the torque converter 22 for power transmission, as well as for lubrication and cooling of various parts. The hydraulic fluid is stored in an oil reservoir such as an oil pan located at the bottom of the case 18, and is also pumped up by the MOP 58 and / or EOP 60 and supplied to the hydraulic control circuit 56.

[0022] Figure 2 is a schematic diagram illustrating a specific example of an automatic transmission 24. This automatic transmission 24 is composed of a total of four planetary gear sets: a single-pinion type first planetary gear set 42, a double-pinion type second planetary gear set 44, a single-pinion type third planetary gear set 46, and a single-pinion type fourth planetary gear set 48. The first planetary gear set 42 and the second planetary gear set 44 constitute a so-called Ravigneau type planetary gear train. This automatic transmission 24 is equipped with four clutches C1 to C4 and two brakes B1 and B2 as the engagement devices CB, and these engagement devices CB are individually engaged and disengaged as shown in the operation table in Figure 3, thereby forming multiple shift ranges with different power transmission states depending on the combination of their engagement and disengagement states. Specifically, for example, a D (Drive) range for forward driving, an R (Reverse) range for reverse driving, a P (Parking) range for parking, and an N (Neutral) range for neutral, which disconnects power transmission, are formed. In the D range for forward driving, it is possible to switch between 10 forward gears (1st gear to 10th gear) with different gear ratios γ, and in the R range for reverse driving, a single reverse gear is established. In the N and P ranges, power transmission is disconnected by releasing all clutches C1 to C4 and brakes B1 and B2. In the operation table in Figure 3, "B2in" and "B2out" refer to a pair of hydraulic actuators provided on brake B2, and brake B2 is engaged and released by both hydraulic actuators B2in and B2out.

[0023] The clutches C1-C4 and brakes B1 and B2 are engaged and disengaged, respectively, by a hydraulic control circuit 56, as shown in Figure 4. The hydraulic control circuit 56 includes the MOP 58 and EOP 60, which are hydraulic pressure sources, as well as a primary regulator valve 102, linear solenoid valves SLT, SL1-SL6, and an on / off solenoid valve SC1. The hydraulic fluid OIL pumped up by the MOP 58 and / or EOP 60 is first regulated to a predetermined line pressure PL by the primary regulator valve 102. A linear solenoid valve SLT is connected to the primary regulator valve 102, and this linear solenoid valve SLT is electrically controlled by an electronic control device 90. That is, according to the line pressure control command signal Sslt supplied from the electronic control device 90, a signal pressure Pslt is output with a modulator hydraulic pressure Pmo, which is approximately constant, as the source pressure. When the signal pressure Pslt is supplied to the primary regulator valve 102, the spool of the primary regulator valve 102 is moved axially in accordance with the signal pressure Pslt, thereby adjusting the relief oil volume and regulating the line pressure PL. This line pressure PL is regulated according to, for example, the accelerator opening θacc, which is the output requirement. The linear solenoid valve SLT is an electromagnetic pressure regulating valve for line pressure adjustment, and the primary regulator valve 102 is a hydraulic control valve that regulates the line pressure PL in accordance with the signal pressure Pslt supplied from the linear solenoid valve SLT. The line pressure adjustment device 100 is composed of these primary regulator valve 102 and linear solenoid valve SLT.

[0024] The hydraulic fluid OIL at line pressure PL, regulated by the line pressure adjustment device 100, is supplied via the supply oil passage 104 to the linear solenoid valves SL1-SL6, the on / off solenoid valve SC1, etc. The linear solenoid valves SL1-SL6 and the on / off solenoid valve SC1 are provided in correspondence with the hydraulic actuators of the clutches C1-C4 and brakes B1 and B2, respectively. By controlling the output hydraulic pressure of each according to the CB hydraulic control command signal Scob supplied from the electronic control device 90, the clutches C1-C4 and brakes B1 and B2 are individually engaged and disengaged. The linear solenoid valves SL1-SL6 are electromagnetic pressure regulating valves, and the on / off solenoid valve SC1 is an electromagnetic on / off valve, both corresponding to electromagnetic valves for shift control that switch the range and gear stage of the automatic transmission 24. Note that Figure 4 is a hydraulic circuit diagram of the part related to the hydraulic control of the automatic transmission 24, and the hydraulic circuits related to the hydraulic control of the K0 clutch 20 and LU clutch 40 are omitted.

[0025] Returning to Figure 1, the electric vehicle 10 is equipped with an electronic control unit 90 as a control device that performs various types of control. The electronic control unit 90 is composed of a so-called microcomputer, for example, which includes a CPU, RAM, ROM, input / output interface, etc. The CPU performs various types of control of the electric vehicle 10 by performing signal processing according to a program stored in ROM in advance, while utilizing the temporary storage function of RAM. The electronic control unit 90 is composed of multiple computers, such as those for engine control, MG control, and hydraulic control, as needed.

[0026] The electronic control unit 90 receives various signals based on values ​​detected by various sensors (for example, engine speed sensor 70, turbine speed sensor 72, output speed sensor 74, MG speed sensor 76, accelerator pedal position sensor 78, throttle valve position sensor 80, brake switch 82, battery sensor 84, oil temperature sensor 86, lever position sensor 88, etc.) installed in the electric vehicle 10. These signals include various types of signals (for example, engine speed Ne, which is the rotational speed of the engine 12; turbine speed Nt, which is the same as the input speed Ni; output speed No, which corresponds to the vehicle speed V; MG speed Nmg, which is the rotational speed of the rotating machine MG; accelerator pedal position θacc, which represents the driver's power request amount based on the amount of operation of the accelerator operating member 79 such as the accelerator pedal; throttle valve position θth, which is the opening degree of the electronic throttle valve; brake ON signal Bon, which is a signal indicating that the brake pedal for activating the wheel brakes is being operated by the driver; battery temperature THbat, battery charge / discharge current Ibat, and battery voltage Vbat of the battery 54. Signals such as the oil temperature THoil, which is the temperature of the hydraulic fluid OIL in the hydraulic control circuit 56, and the operating position POSsh of the shift lever 64 provided in the electric vehicle 10 are supplied.

[0027] The shift lever 64 is located near the driver's seat and is a shift operating member operated by the driver to switch the shift ranges P, R, N, and D, which are the power transmission states of the automatic transmission 24. It has multiple operating positions POSsh. P, R, N, and D are provided as operating positions POSsh, and by moving to these operating positions POSsh, the driver can select the respective shift ranges P, R, N, and D. The P position is the operating position for selecting the P range for parking, in which the automatic transmission 24 is in a neutral state where power transmission is cut off and the rotation of the output shaft 26 is mechanically prevented. The neutral state is in which all engagement devices CB of the automatic transmission 24 are released. The R position is the operating position for selecting the R range for reverse driving, in which the automatic transmission 24 is in the reverse gear position. The N position is the operating position for selecting the N range, in which the automatic transmission 24 is in a neutral state, similar to the P position. The D position is an operating position for selecting the D range for forward driving, which automatically switches between multiple forward gears of the automatic transmission 24 according to driving conditions such as vehicle speed V and accelerator opening θacc. The shift lever 64 may be positioned and held in each of the P, R, N, and D operating positions POSsh, or it may be an automatic return type that automatically returns to a predetermined home position. In addition, a push-button switch or the like may be used as a shift operating member to select each of the above shift ranges.

[0028] The electronic control unit 90 outputs various command signals (for example, engine control command signal Se for controlling engine 12, MG control command signal Smg for controlling rotating machine MG, CB hydraulic control command signal Scb for controlling engagement device CB, K0 hydraulic control command signal Sk0 for controlling K0 clutch 20, LU hydraulic control command signal Slu for controlling LU clutch 40, line pressure control command signal Sslt for regulating line pressure PL, EOP control command signal Seop for controlling EOP 60, etc.) to each device installed in the electric vehicle 10. The hydraulic control circuit 56 is equipped with linear solenoid valves SL1 to SL6 controlled by the CB hydraulic control command signal Scob, an on / off solenoid valve SC1, a linear solenoid valve SLT controlled by the line pressure control command signal Sslt, and multiple solenoid valves that switch oil passages and control hydraulic pressure according to the K0 hydraulic control command signal Sk0 and the LU hydraulic control command signal Slu. When the engagement device CB, K0 clutch 20, and LU clutch 40 are held in the engaged state, the line pressure PL, which has been regulated by the line pressure control command signal Sslt, is supplied as is to maintain the engaged state.

[0029] The electronic control unit 90 functionally includes a hybrid control unit 92, a gear shift control unit 94, a traction control unit 96, and a component protection control unit 98 in order to realize various controls in the electric vehicle 10.

[0030] The hybrid control unit 92 has the function of coordinating the operation of the engine 12 and the rotating machine MG, and comprises an engine control unit 92a that controls the engine 12 and an MG control unit 92b that controls the rotating machine MG. The hybrid control unit 92 calculates the amount of drive requested by the driver to the electric vehicle 10 by, for example, applying the accelerator opening θacc and the vehicle speed V to the drive request amount map. The amount of drive request is, for example, the requested drive torque Trdem at the drive wheels 14. The hybrid control unit 92 considers the transmission loss, auxiliary load, the gear ratio γ of the automatic transmission 24, the torque ratio of the torque converter 22, the rechargeable power Win and dischargeable power Wout of the battery 54, etc., and determines, for example, the requested TC input torque Ttcdem, which is the input torque of the torque converter 22 necessary to achieve the above requested drive torque Trdem. It outputs an engine control command signal Se to control the engine 12 and an MG control command signal Smg to control the rotating machine MG so that the requested TC input torque Ttcdem can be obtained. The rechargeable power Win and dischargeable power Wout of battery 54 are calculated by the electronic control unit 90 based on, for example, the battery temperature THbat and the charge state value (SOC) of battery 54. The charge state value (SOC) of battery 54 is a value that indicates the charge state of battery 54, i.e., the remaining charge, and can be calculated based on, for example, the battery charge / discharge current Ibat and the battery voltage Vbat.

[0031] The hybrid control unit 92 switches to a BEV (Battery Electric Vehicle) driving mode, which is a motor driving mode in which the rotating machine MG is driven solely by power from the battery 54, if the required TC input torque Ttcdem can be met by the output of the rotating machine MG alone. In BEV driving mode, the K0 clutch 20 is disengaged to stop the engine 12, and BEV driving is performed using only the rotating machine MG as the driving force source. In this BEV driving mode, the MG torque Tmg is controlled to achieve the required TC input torque Ttcdem. On the other hand, if the required TC input torque Ttcdem cannot be met without using at least the output of the engine 12, the hybrid control unit 92 switches to an HEV (Hybrid Electric Vehicle) driving mode, which is an engine driving mode. In HEV driving mode, the K0 clutch 20 is engaged to perform engine driving, i.e., HEV driving, using at least the engine 12 as the driving force source. In this HEV driving mode, the engine torque Te is controlled to achieve all or part of the required TC input torque Ttcdem, and the MG torque Tmg is controlled to compensate for the torque that is insufficient with respect to the required TC input torque Ttcdem from the engine torque Te. On the other hand, even if the required TC input torque Ttcdem can be met by the output of the rotating machine MG alone, the hybrid control unit 92 will activate the HEV driving mode when warming up the engine 12, etc. is necessary. In this way, the hybrid control unit 92 switches between the BEV driving mode and the HEV driving mode by automatically stopping the engine 12 during HEV driving, restarting the engine 12 after it has stopped, starting the engine 12 during BEV driving, automatically stopping the engine 12 while the vehicle is stopped, or starting the engine 12.

[0032] When the D range is selected, the transmission control unit 94 makes a transmission change decision for the automatic transmission 24 using a predetermined transmission map, for example, with driving conditions such as vehicle speed V and accelerator opening θacc as variables, and performs automatic transmission control by outputting a CB hydraulic control command signal Scrb to the hydraulic control circuit 56 to automatically switch between multiple forward gears of the automatic transmission 24 as needed. Furthermore, when the driver operates the shift lever 64 or a manual transmission operating member located near the driver's seat and a transmission change instruction signal is supplied, manual transmission control is performed to switch the forward gears of the automatic transmission 24 according to that transmission change instruction.

[0033] The gear shift control unit 94 also performs garage control, which switches the shift range of the automatic transmission 24 according to the switched operating position POSsh when the shift lever 64 is operated and the operating position POSsh is switched. Garage control performs reverse range switching, which switches the automatic transmission 24 from one range to the other when a reverse shift operation is performed in which the shift lever 64 is switched from one range to the other, such as switching the shift range from the D range and the R range, to the other, and also performs various range switching, which switches the shift range between the non-driving ranges of P range and N range and the driving ranges of D range and R range.

[0034] The traction control unit 96 stabilizes the vehicle's behavior by suppressing skidding and wheel spin, and ensures a predetermined driving force. It controls the operation of the engine 12 and the rotating machine MG, which are the driving force sources, and controls the braking force of all wheels, including the drive wheels 14, via a wheel brake control device (not shown). Systems such as ABS (Antilock Brake System) and VSC (Vehicle Stability Control) can also be considered examples of the traction control unit 96.

[0035] The component protection control unit 98 is designed to prevent the engagement device CB of the automatic transmission 24 from slipping when the vehicle is reversing downhill and then climbing uphill, thereby protecting the engagement device CB. Specifically, when the vehicle starts moving, the suspension system 66 can cause vertical vibrations of the drive wheels 14, known as power hops. When a rear-wheel-drive vehicle like the electric vehicle 10 is reversing downhill and then climbing uphill, the frictional force between the drive wheels 14 and the road surface decreases. As a result, slip-grip is more likely to occur due to changes in frictional force during the vertical movement of the drive wheels 14 caused by power hops. When the rotational speed of the drive wheels 14 fluctuates periodically due to these slip-grips, a large load is placed on the engagement device CB in relation to the input torque Tin that is input from the power source (engine 12 or rotating machine MG) through the torque converter 22 to the automatic transmission 24, potentially causing slippage.

[0036] Referring specifically to the automatic transmission 24 shown in Figures 2 to 4, in the R range where reverse driving is possible, clutches C2 and C3 and brake B2 are engaged to form the reverse gear. Based on the diameter dimensions, pressure receiving area, and torque distribution ratio of these hydraulic actuators, we assume that, for example, clutch C3 is the most prone to slipping. Figure 8 is an example of the torque TC3 acting on clutch C3. The input torque TC3in, shown by the dashed line, and the output torque TC3out, shown by the dashed line, are added together to form the total torque TC3total, shown by the solid line. This total torque TC3total acts on clutch C3, and slip occurs when this total torque TC3total exceeds the torque capacity tc3capa of clutch C3. The input torque TC3in is obtained by multiplying the input torque Tin, which is input to the automatic transmission 24 according to the accelerator opening θacc, by the distribution ratio, and it changes relatively smoothly. The output torque TC3out is calculated by multiplying the output inert torque Tinert on the automatic transmission 24 by its share ratio, and here it periodically increases or decreases due to changes in rotational resistance caused by slip-grip of the drive wheels 14. In this case, when the rotational speed of the drive wheels 14 decreases during deceleration, the output torque TC3out applied to the clutch C3 acts on the positive side, increasing the load on the clutch C3, while when the rotational speed of the drive wheels 14 increases during acceleration, the output torque TC3out applied to the clutch C3 acts on the negative side.

[0037] The component protection control unit 98 is designed to protect the clutch C3 from slipping due to slip-grip of the drive wheel 14. Since the periodic increase and decrease fluctuations of the output rotational speed No of the automatic transmission 24 correspond to the inertar torque Tinert, the unit performs protection control based on the periodic increase and decrease fluctuations of the output rotational speed No. Specifically, it performs signal processing according to steps S1 to S4 of the flowchart in Figure 5 (hereinafter, the steps will be omitted and simply referred to as S1 to S4; the same applies to other flowcharts), and suppresses clutch C3 slippage by implementing input torque limiting control to limit the input torque Tin as needed.

[0038] In S1 of Figure 5, it is determined whether the input torque limiting start condition is met. The input torque limiting start condition is a protection execution condition, and in this embodiment, the input torque limiting start condition is met if all of the following (a) to (c) are met, and input torque limiting control from S2 onwards is executed. On the other hand, if any one of (a) to (c) is not met, the process terminates.

[0039] (a) All of the following (i) to (iii) are true. This requirement (a) relates to the inert shuttle Tinert etc. which is input in reverse from the drive wheel 14 side, and is a requirement concerning the output rotational speed No. (i) The state Noac ≤ noacs continues for a definite time of ta or longer. Noac is the output rotational acceleration, which is the rate of change of the output rotational speed No, and is a variable corresponding to the inert shuttle clutch Tinert, while noacs is a predetermined protective judgment acceleration. The protective judgment acceleration noacs is a condition for determining whether or not the clutch C3 may slip, and is a negative value when the output rotational speed No decreases during deceleration. It may be a constant value, but it may also be set variably based on vehicle conditions such as the input torque Tin. In this embodiment, for example, a constant value of about -2500 (rpm / s) is set. The confirmation time ta is for eliminating instantaneous detection errors, etc., and for example, a constant time of about 10 (ms) is set. If this condition (i) is met, it means that the output rotational speed No is rapidly decelerating due to the grip of the drive wheels 14. (ii) After (i), the state Noac > noacs continues for a fixed time tb or longer. This means that the output rotational acceleration Noac is increasing from a minimum, and the deceleration of the output rotational speed No is decreasing or changing towards an increase. The fixed time tb is used to eliminate instantaneous detection errors, and a constant time of about 10 ms is set. (iii) If (i) is true again within the repeated judgment time tc from (ii), This is for determining whether the fluctuation is due to periodic increases or decreases caused by slip-grip of the drive wheels 14 resulting from power hop. The period of fluctuation in the output rotational speed No is determined by the vehicle weight, suspension device 66, etc., and the repetition determination time tc is set to a constant value for each vehicle type, for example, but may be set to a variable value based on the vehicle weight, etc. In this embodiment, for example, a constant value of about 200 (ms) is set.

[0040] (b) Not during a gear shift transient, garage control transient, or engine start / stop control transient. In other words, this is the case when the automatic transmission 24 is not being controlled by the gear shift control unit 94, the garage control unit 94 is not being controlled by the gear shift control unit 94, the engine 12 is not being started by the hybrid control unit 92, and the engine 12 is not being stopped by the hybrid control unit 92. This is because it is not appropriate to perform these controls and the input torque limit control below S2 simultaneously.

[0041] (c) Tin≧tins holds. If the input torque Tin is small, there is no risk of clutch C3 slipping; therefore, the requirement is that the input torque Tin is equal to or greater than a predetermined protection judgment torque tins. The protection judgment torque tins may be a fixed value predetermined, or it may be set variably based on the torque capacity tc3capa of clutch C3, etc. In this embodiment, for example, a fixed value of about 300 (Nm) is set.

[0042] If the judgment in S1 above is YES (affirmative), S2 to S4 are executed as input torque limiting control, which corresponds to protective control that suppresses and protects against clutch C3 slippage. In S2, the input torque Tin is limited. Specifically, an engine control command signal Se or an MG control command signal Smg is output to reduce the torque Te of the engine 12, which is the driving force source, or the torque Tmg of the rotating machine MG, so that the input torque Tin is reduced by a predetermined reduction amount. The reduction amount may be predetermined to a constant value so as to suppress clutch C3 slippage, but it may also be set variably based on vehicle conditions such as the minimum value of the output rotational acceleration Noac. If the reduction amount is large, it will affect driving performance such as off-road capability, so it is desirable to keep it to the minimum necessary, and in this embodiment, for example, a constant value of about 100 (Nm) is set. Instead of the input torque Tin of the automatic transmission 24, the TC input torque Ttc, which is the input torque of the torque converter 22, may be reduced by a predetermined reduction amount.

[0043] In S3, it is determined whether the input torque limit termination condition has been met. The input torque limit in S2 is continued until the input torque limit termination condition is met. If the input torque limit termination condition is met, S4 is executed to terminate the input torque limit control. Since input torque limiting can impair driving performance, it is desirable to limit it to the minimum necessary. The input torque limit termination condition is set to be met, for example, when either (a) or (b) below is satisfied. (a) When the accelerator is released, with the accelerator opening θacc being approximately 0. (b) The output rotational acceleration Noac is equal to or greater than a predetermined acceleration and there is no clutch slippage, and this condition is maintained for a predetermined period of time or longer.

[0044] As described in (a) above, the input torque limit is released when the accelerator is released, allowing for a quick response when the accelerator operating member 79 is operated again for re-acceleration. The predetermined acceleration in (b) is, for example, the same as or higher (close to 0 or positive) the protection determination acceleration noacs, and the predetermined time is, for example, the repetition determination time tc. If the output rotational acceleration Noac does not fall below the predetermined acceleration during the repetition determination time tc, it can be determined that the fluctuations in the increase or decrease of the output rotational speed No due to the slip-grip of the drive wheels 14 caused by power hop have converged, and the possibility of clutch C3 slipping has decreased. Whether or not clutch slippage has occurred can be determined by multiplying the output rotational speed No by the gear ratio γ to obtain the input rotational speed equivalent value No × γ, and whether or not this input rotational speed equivalent value No × γ is approximately the same as the actual input rotational speed Nin. The predetermined time in (b) may be set to be longer than the repetition determination time tc.

[0045] Figure 9 is an example of a time chart illustrating the changes in accelerator opening θacc, rotational speeds Nmg, Nin, No × γ, output rotational acceleration Noac, input torque Tin, and line pressure PL when starting uphill in reverse in R range, according to the flowchart in Figure 5. At time t1 in Figure 9, fluctuations in output rotational speed No due to slip-grip of the drive wheel 14 begin to occur, and in the Es region of the output rotational acceleration Noac column, the minimum value of the increase-decrease change in output rotational acceleration Noac becomes less than or equal to the protection judgment acceleration noacs, thus satisfying the input torque limit start condition of S1, and at time t2, input torque limit control of S2 or less is started. By reducing the input torque Tin with this input torque limit control, clutch C3 slip is suppressed. The fact that the input rotational speed Nin in the rotational speed column and the input rotational speed equivalent value No × γ, which is obtained by multiplying the output rotational speed No by the gear ratio γ, are approximately the same means that no slip is occurring in the engagement device CB, including the clutch C3 that is engaged in the R range. Then, in the time chart of Figure 9, at time t3, the decision of S3 becomes YES as the accelerator is released, and S4 is executed, ending the input torque limit control.

[0046] The time chart for the C3 torque TC3 in Figure 8, as in Figure 9, shows that when input torque limiting control is performed, the input torque Tin is reduced before the total torque TC3total reaches the torque capacity tc3capa of the clutch C3, thereby reducing the input side torque TC3in and preventing clutch C3 from slipping.

[0047] In addition to the input torque limit control according to the flowchart in Figure 5, or instead of the input torque limit control, the component protection control unit 98 performs line pressure maximum pressure control according to the flowchart in Figure 6, setting the line pressure PL to the maximum pressure PLmax as needed. In this embodiment, line pressure maximum pressure control according to the flowchart in Figure 6 is performed in parallel with the input torque limit control according to the flowchart in Figure 5. Line pressure maximum pressure control is an engagement force increase control that increases the engagement force of the clutch C3, and corresponds to protection control that suppresses and protects against slippage of the clutch C3.

[0048] In SS1 of Figure 6, it is determined whether or not the maximum line pressure initiation condition is met. The maximum line pressure initiation condition is a protection execution condition, and for example, the same condition as the input torque limit initiation condition of S1 in Figure 5 is set. Maximum line pressure control is a control that suppresses slip by increasing the engagement force of the clutch C3, and since it does not have the same risk of affecting driving performance as input torque limit control, it is not necessarily required to set the same condition as the input torque limit initiation condition of S1 in Figure 5. For example, the protection judgment acceleration noacs may be increased (bringing it closer to 0), or conditions (b) and (c) may be omitted, thereby relaxing the initiation conditions for maximum line pressure control compared to input torque limit control and widening the operating range in which maximum line pressure control is executed.

[0049] If the judgment in SS1 above is YES, SS2 to SS4 are executed to control the maximum line pressure, and in SS2, the line pressure PL is set to the maximum pressure PLmax. Specifically, a line pressure control command signal Sslt is output to the linear solenoid valve SLT of the line pressure adjustment device 100, which sets the line pressure PL to the maximum pressure PLmax, taking precedence over the control of the line pressure PL based on the accelerator opening θacc, etc. As a result, the engagement devices CB, including the clutch C3 that can be engaged in the R range, are all held engaged at the maximum pressure PLmax, and slip of these engagement devices CB is suppressed regardless of the slip-grip of the drive wheels 14. The maximum pressure PLmax is determined according to the discharge capacity of the hydraulic power sources MOP 58 and EOP 60 of the hydraulic control circuit 56, and in this embodiment, it is controlled to a value of approximately 1800 (kPa).

[0050] In SS3, it is determined whether the line pressure maximum termination condition has been met. SS2 is repeated until the line pressure PL remains at its maximum state (PLmax), while SS4 is executed to terminate the line pressure maximum control once the condition is met. Since prolonged line pressure maximum control promotes a rise in the hydraulic fluid temperature, the line pressure maximum termination condition is defined to be met, for example, when either (a) or (b) below is satisfied. (a) The output rotational acceleration Noac is equal to or greater than a predetermined acceleration and there is no clutch slippage, and this condition is maintained for a predetermined period of time or longer. (b) The input rotational speed Nin is less than or equal to a predetermined value.

[0051] The above (a) is the same condition as (b) of the input torque limit termination condition for S3 in Figure 5, and it can be determined that the fluctuations in the increase or decrease of the output rotational speed No due to the slip-grip of the drive wheel 14 caused by power hop have subsided, and the possibility of clutch C3 slipping has decreased. The predetermined value in (b) is, for example, the rotational speed at which engine stop can be avoided.

[0052] The time chart in Figure 9 shows the case where input torque limit control is performed according to the flowchart in Figure 5, and line pressure maximum control is performed according to the flowchart in Figure 6. At time t2, input torque limit control starts and line pressure maximum control starts simultaneously, controlling the line pressure PL to reach its maximum pressure PLmax. In other words, when the line pressure maximum start condition for SS1 is the same as the input torque limit start condition for S1, line pressure maximum control starts simultaneously with the start of input torque limit control. Furthermore, since the line pressure PL is originally set to its maximum pressure PLmax depending on the accelerator opening θacc, etc., when starting in reverse driving, the state of maximum pressure PLmax is maintained when line pressure maximum control is performed, and the state of maximum pressure PLmax is maintained regardless of the accelerator off operation at time t3, thereby suppressing clutch C3 slip. Then, at time t4, for example, by satisfying condition (a) of the line pressure maximum termination condition for SS3, the line pressure maximum control is terminated in SS4, and the line pressure PL is controlled according to normal control based on the accelerator opening θacc, etc.

[0053] On the other hand, Figure 10 shows an example of a time chart for starting uphill in reverse in R range in a conventional case where neither the input torque limit control nor the maximum line pressure control is performed, similar to Figure 9. At time t1, the increase or decrease in output rotational speed No due to slip and grip of the drive wheels 14 begins, just as in Figure 9. However, even when the minimum value of the increase or decrease in output rotational acceleration Noac falls below the protection judgment acceleration noacs, the input torque limit control is not performed, so the increase or decrease in output rotational speed No (input rotational conversion value No × γ in Figure 10) continues to increase. When the total torque TC3total of clutch C3 exceeds the torque capacity tc3capa, clutch C3 begins to slip, and clutch C3 slippage begins at time t2. The dashed line in the rotational speed column between times t2 and t3 represents the input rotational conversion value No × γ, and the solid line represents the input rotational speed Nin. The difference between the two indicates that clutch C3 is slipping. The slip of clutch C3 continues even after the accelerator is released, and the slip of clutch C3 is resolved around time t3 when the brake ON signal Bon turns ON in response to the brake operation.

[0054] The component protection control unit 98 also determines whether or not to implement the input torque limit control and line pressure maximum pressure control shown in Figures 5 and 6 based on the type of driving range and whether or not traction control is being implemented by the traction control unit 96, as shown in Figure 7. That is, in the D range for forward driving, since there is a low possibility of the drive wheels 14 slipping and gripping due to power hop, neither input torque limit control nor line pressure maximum pressure control is implemented, regardless of whether traction control is being implemented (ON) or not (OFF). In the R range for reverse driving, if traction control is not being implemented (OFF), both input torque limit control and line pressure maximum pressure control are implemented. Also, when traction control is being implemented (ON) in the R range, input torque limit control, which affects the driving force, is not implemented, but line pressure maximum pressure control is implemented. Whether or not traction control is being implemented can be determined by, for example, setting a flag to indicate whether or not traction control is being implemented. The decision in Figure 7 is preferably made before implementing S1 and SS1 in Figures 5 and 6, but it may also be made only if the decision in S1 and SS1 is YES. In addition, conditions related to other vehicle conditions that cause slip-grip of the drive wheels 14 or slip of the clutch C3 due to power hop may be set, such as conditions related to the road surface gradient limited to when reversing downhill and then climbing uphill, conditions related to the vehicle speed V limited to when the vehicle starts, and conditions related to the vehicle weight that are related to slip-grip of the drive wheels 14, and a decision may be made on whether or not to implement input torque limit control or line pressure maximum pressure control.

[0055] As described above, the electronic control unit 90 of the electric vehicle 10 in this embodiment is functionally equipped with a component protection control unit 98. When driving in reverse, it detects periodic increases and decreases in the output rotational speed No of the automatic transmission 24, and if the increase and decrease in

[0056] Although embodiments of the present invention have been described in detail above with reference to the drawings, this is merely one embodiment, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art. [Explanation of symbols]

[0057] 10: Hybrid electric vehicle (vehicle) 12: Engine (driving force source) 14: Drive wheels (rear wheels) 16: Power transmission device (power transmission path) 22: Torque converter (fluid transmission device) 24: Automatic transmission (transmission) 26: Output shaft 90: Electronic control device (control device) 98: Component protection control unit MG: Rotating machine (driving force source) SB: Engagement device (friction engagement device) C1~C4: Clutch (friction engagement device) B1, B2: Brake (friction engagement device) No: Output rotational speed (rotational speed of the output shaft) Noac: Output rotational acceleration S1: Input torque limit start condition (protection execution condition) SS1: Line pressure maximum pressure start condition (protection execution condition) S2~S4: Input torque limit control (protection control) SS2~SS4: Line pressure maximum pressure control (protection control)

Claims

[Claim 1] In a vehicle control device, the vehicle moves by the rotational drive of the rear wheels by a power source, and the power transmission path between the power source and the rear wheels is arranged in series with a fluid-type transmission device and a transmission that transmits power via a friction engagement device from the power source side, The transmission has a component protection control unit that, when detecting a periodic increase or decrease in the rotational speed of the output shaft of the transmission during reverse driving, and when the increase or decrease in the rotational speed of the transmission meets the predetermined protection execution conditions for which slippage of the friction engagement device is predicted, executes protective control to suppress slippage of the friction engagement device of the transmission that is engaged during reverse driving. The component protection control unit performs at least one of the following as protection control: control to limit the input torque of the transmission and control to increase the engagement force of the friction engagement device. A vehicle control device characterized by the following features.

Images