WO2012108001A1

WO2012108001A1 - Drive control device for front and rear wheel drive vehicle

Info

Publication number: WO2012108001A1
Application number: PCT/JP2011/052644
Authority: WO
Inventors: 矢野　雅也
Original assignee: トヨタ自動車株式会社
Priority date: 2011-02-08
Filing date: 2011-02-08
Publication date: 2012-08-16

Abstract

Provided is a drive control device for a front and rear wheel drive vehicle capable of improving the stability of vehicle behavior during regenerative braking of the front and rear wheel drive vehicle. When torque transmission is limited by a control coupling device (54), a regenerative braking torque determination means (132) sets the regenerative braking torque (Tgr) of a second electric motor (M2) to be smaller than that generated when the torque transmission is not limited. When the torque transmission is limited, if the regenerative braking torque (Tgr) of the second electric motor (M2) is not changed from that generated when the torque transmission is not limited, vehicle behavior tends to become unstable compared to that when the torque transmission is not limited because rear drive wheels (32) slip. Accordingly, compared to a case in which the regenerative braking torque (Tgr) of the second electric motor (M2) is generated without considering when the torque transmission is limited by the control coupling device (54), it is possible to improve the stability of vehicle behavior during regenerative braking of a vehicle (6). Such effect becomes significant particularly when, for example, a road has a low-μ.

Description

Drive control device for front and rear wheel drive vehicle

The present invention relates to a technique for controlling a regenerative braking torque of a motor in a vehicle drive device in which the motor is regeneratively operated by torque from a drive wheel.

During regenerative braking in front and rear wheel drive traveling, the regenerative braking torque of the electric motor is transmitted to one of the front wheels and the rear wheels, and the electric motor is connected to the other of the front wheels and the rear wheels via a torque distribution device. A drive control device for a front and rear wheel drive vehicle to which the regenerative braking torque is transmitted is well known. For example, the drive control apparatus for four-wheel drive vehicles of patent document 1 is the example. In the four-wheel drive vehicle of Patent Document 1, the one wheel is a rear wheel, the other wheel is a front wheel, and the torque distribution device is a clutch device in which transmission torque is changed according to engagement force. . And the drive control apparatus of the patent document 1 transmits a part of the regenerative braking torque of the motor to the front wheels by engaging the clutch device during regenerative operation of the motor, that is, during regenerative braking. By doing in this way, while ensuring the stability of the vehicle behavior at the time of the regenerative braking of the electric motor, the fuel efficiency can be improved by the regenerative operation of the electric motor. For example, the fuel efficiency is a travel distance per unit fuel consumption, and the improvement in fuel efficiency is an increase in the travel distance per unit fuel consumption, or the fuel consumption rate ( = Fuel consumption / drive wheel output) is reduced. Conversely, a reduction in fuel consumption means that the travel distance per unit fuel consumption is shortened, or the fuel consumption rate of the entire vehicle is increased. This definition of fuel consumption is the same throughout the specification.

JP 2010-149745 A Japanese Patent Laid-Open No. 2005-082048

In the drive control device of Patent Document 1, since the regenerative braking torque of the motor is distributed and transmitted to each of the front wheels and the rear wheels during regenerative braking of the motor, for example, the same torque as the regenerative braking torque is The stability of the vehicle behavior is further improved compared to the case where the vehicle behavior is transmitted only to the wheels. However, depending on the state of the torque distribution device (clutch device), for example, it is assumed that the maximum torque capacity of the torque distribution device is reduced and torque transmission of the torque distribution device is limited. When torque transmission is limited in such a torque distribution device, the regenerative braking torque of the motor is distributed and transmitted to each of the front and rear wheels in the same manner as when non-torque transmission is limited. Assuming that the motor is regeneratively operated as a premise, most or all of the regenerative braking torque of the motor premised on vehicle braking by the front wheels and the rear wheels is transmitted to the rear wheels, so that the rear wheels easily slip. Vehicle behavior could become unstable.

The present invention has been made against the background of the above circumstances, and an object of the present invention is to provide a drive control device capable of improving the stability of vehicle behavior during regenerative braking of front and rear wheel drive vehicles. is there.

To achieve the above object, the gist of the present invention is that (a) during regenerative braking in front and rear wheel drive traveling, the regenerative braking torque of the motor is transmitted to one of the front wheels and the rear wheels, and the front wheels And a drive control device for front and rear wheel drive vehicles in which the regenerative braking torque of the electric motor is transmitted to the other of the rear wheels via a torque distribution device, and (b) torque transmission of the torque distribution device When the torque transmission is limited, the regenerative braking torque of the electric motor is set to be smaller than that when the torque distribution device of the torque distribution device is limited.

In this way, when the torque transmission is limited, the distribution ratio of the regenerative braking torque of the motor transmitted to the other wheel is lower than when the non-torque transmission is limited, while the torque transmission is transmitted to the one wheel. Since the regenerative braking torque distribution ratio is increased, if the regenerative braking torque does not change from that at the time of non-torque transmission restriction, the one wheel slips and the vehicle behavior tends to become unstable. Since the regenerative braking torque is made smaller than that when the non-torque transmission is limited, the regenerative braking torque of the motor is generated without considering the torque transmission limitation of the torque distribution device. The stability of vehicle behavior can be improved during regenerative braking. In particular, the effect of the present invention becomes remarkable on a low μ road where the friction coefficient of the wheel against the road surface is small, such as an icy road. The torque distribution device may increase or decrease the transmission torque to the other wheel continuously or stepwise. For example, the torque distribution device is a power interrupting device that selectively sets the transmission torque to zero. There is no problem.

Here, preferably, when the torque transmission is restricted, the temperature of the torque distribution device is equal to or higher than a predetermined torque distribution device temperature determination value. In this way, it is possible to easily determine whether or not the torque transmission is limited by detecting the temperature of the torque distribution device.

Preferably, (a) the regenerative braking torque of the electric motor is limited to a predetermined maximum allowable regenerative braking torque, or (b) the maximum allowable regenerative braking torque is set to the non-torque when the torque transmission is limited. By setting it smaller than when the transmission is restricted, the regenerative braking torque of the motor is made smaller when the torque transmission is restricted than when the non-torque transmission is restricted. In this case, the regenerative braking torque of the electric motor can be easily reduced by changing the setting of the maximum allowable regenerative braking torque.

Preferably, when the torque transmission is restricted, the maximum allowable regenerative braking torque is set so that the regenerative braking torque of the electric motor is not transmitted to the other wheel, so that the slip of the one wheel does not occur. In this way, since the regenerative braking torque of the electric motor is limited to the same magnitude as that of a two-wheel drive vehicle that travels by driving only the one wheel, the slip of one wheel is sufficiently suppressed. Thus, sufficient stability of vehicle behavior can be secured.

It is a figure for demonstrating the drive device for vehicles provided in the part time type four-wheel drive vehicle which is a front-and-rear wheel drive vehicle to which this invention was applied, and the electronic control apparatus for controlling it. FIG. 2 is a skeleton diagram for explaining a configuration of a power transmission device and a transfer provided in the part-time four-wheel drive vehicle of FIG. 1. It is a functional block diagram for demonstrating the principal part of the control function with which the electronic control apparatus shown in FIG. 1 was equipped. It is a figure showing the relationship between the maximum torque capacity and coupling temperature of the control coupling apparatus shown in FIG. It is the figure which illustrated the relationship between the front-wheel braking force and the rear-wheel braking force in each at the time of the torque transmission restriction | limiting of the control coupling apparatus shown in FIG. FIG. 2 is a flowchart for explaining a main part of a control operation of the electronic control device shown in FIG. 1, that is, a control operation for generating a vehicle braking force when a part-time four-wheel drive vehicle performs regenerative braking traveling. FIG. 7 is a flowchart for explaining the main part of the control operation of the electronic control device shown in FIG. 1 together with FIG. 6, and is a flowchart showing a subroutine executed in step SA <b> 3 of FIG. 6. It is the figure which showed an example of the electric vehicle which remove | excluded the engine, the power distribution mechanism, and the 1st electric motor from the part time type | mold four-wheel drive vehicle of FIG.

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

FIG. 1 shows a vehicle drive device 8 provided in a part-time four-wheel drive vehicle 6 (hereinafter referred to as a vehicle 6) that is a front and rear wheel drive vehicle to which the present invention is applied, and an electronic control device for controlling the vehicle drive device 8. 10 is a diagram for explaining 10. FIG. The electronic control device 10 corresponds to the drive control device in the present invention. The vehicle drive device 8 of the present embodiment is suitably used for a hybrid vehicle that employs a part-time 4WD system based on a front engine rear wheel drive system (FR).

As shown in FIG. 1, a vehicle 6 includes an electronic control device 10, a vehicle drive device 8 including an engine 12 and a power transmission device 14, a transfer 16, a front propeller shaft 18, and a front wheel differential gear device. 20, a pair of front wheel axles 22, a rear propeller shaft 24, a rear wheel differential gear device 26, a pair of rear wheel axles 28, a pair of front wheel front drive wheels 30, and a front drive wheel 30 thereof. And a rear drive wheel 32 which is a pair of rear wheels having the same wheel diameter. In FIG. 1, for example, a driving force (driving torque) generated by an engine 12 that is an internal combustion engine such as a gasoline engine or a diesel engine is transmitted to a transfer 16 via a power transmission device 14. The driving force transmitted to the transfer 16 is distributed to the front propeller shaft 18 and the rear propeller shaft 24. The driving force transmitted to the front propeller shaft 18 is transmitted to the pair of left and right front drive wheels 30 via the front wheel differential gear unit 20 and the front wheel axle 22. On the other hand, the driving force transmitted to the rear propeller shaft 24 is transmitted to the pair of left and right rear driving wheels 32 via the rear wheel differential gear device 26 and the rear wheel axle 28. The front-wheel differential gear device 20 and the rear-wheel differential gear device 26 are well-known so-called bevel gear types, and a pair of left and right front wheel axles 22 and rear wheel axles 28 while allowing a difference in rotation. Are driven to rotate. The front drive wheel 30 corresponds to the other wheel of the present invention, and the rear drive wheel 32 corresponds to one wheel of the present invention.

FIG. 2 is a skeleton diagram for explaining the configuration of the power transmission device 14 and the transfer 16 shown in FIG. In FIG. 2, the power transmission device 14 includes an input shaft 36 connected to the crankshaft of the engine 12, a power distribution mechanism 46 connected to the input shaft 36, and power to the power distribution mechanism 46 in the transmission case 34. The first electric motor M1 that is connected so as to be able to transmit and controls the differential state of the power distribution mechanism 46, and the second electric motor M2 that is connected to the output shaft 44 so as to rotate integrally with the output shaft 44 are shared. It is equipped on the axis RC1. The power transmission device 14 according to the present embodiment is an electric that continuously changes a speed ratio γ0 (rotational speed Nin of the input shaft 36 / rotational speed Nout of the output shaft 44), which is a rotational speed ratio of the output shaft 44 to the input shaft 36. It functions as a continuously variable transmission. The output shaft 44 is an output side rotation member of the power transmission device 14, but also corresponds to an input side rotation member of the transfer 16. The power distribution mechanism 46 includes a sun gear S0 connected to the first electric motor M1, a planetary gear P0, a carrier CA0 connected to the input shaft 36 and supporting the planetary gear P0 so as to rotate and revolve, and a planetary gear. This is a single pinion type planetary gear device that includes a ring gear R0 that meshes with the sun gear S0 via P0 and is connected to the output shaft 44. The first electric motor M1 and the second electric motor M2 (hereinafter referred to as the electric motor M when not particularly distinguished) selectively function as an electric motor that generates driving torque and function as a generator that generates regenerative torque. The rotating machine is configured by, for example, an AC synchronous motor generator. Further, a power storage device 50 that is a battery and an inverter 48 for controlling the motors M1 and M2 are provided in the vehicle drive device 8 (see FIG. 1), and the power storage device 50, the first electric motor M1, and the second The electric motor M2 is connected to be able to exchange electric power with each other. Each of the first electric motor M1 and the second electric motor M2 is controlled by the electronic control device 10 via the inverter 48, generates electric energy by regenerative operation, and stores (charges) the electric energy in, for example, the power storage device 50. For example, the second electric motor M2 is transmitted from one or both of the front drive wheels 30 and the rear drive wheels 32 during coasting when the accelerator is off (coast driving) or when the vehicle is braked by operating the brake pedal 96. A regenerative operation for converting the kinetic energy of the vehicle 6 into electrical energy is performed. Accordingly, the second electric motor M2 corresponds to the electric motor that generates the regenerative braking torque in the present invention. Since the power transmission device 14 is configured symmetrically with respect to the axis RC1, the lower side is omitted in the skeleton diagram of FIG. In this embodiment, the rotational speed Nin of the input shaft 36 is the same as the engine rotational speed Ne because the input shaft 36 is connected in series to the crankshaft of the engine 12.

In the power transmission device 14 configured as described above, in the differential state in which the rotating elements (the sun gear S0, the ring gear R0, and the carrier CA0) of the power distribution mechanism 46 are relatively rotatable with respect to each other, and the differential action works. The output of the engine 12 is distributed to the first electric motor M1 and the output shaft 44, and at the same time, a part of the distributed output of the engine 12 is stored with the electric energy generated from the first electric motor M1, or the second electric motor. M2 is driven to rotate. The rotation speed of the first electric motor M1 is controlled so that the rotation of the output shaft 44 is continuously changed regardless of the predetermined rotation of the engine 12, whereby the speed ratio γ0 of the power distribution mechanism 46 is increased from the minimum value γ0min to the maximum. A continuously variable transmission state that functions as an electrical continuously variable transmission that is continuously changed to the value γ0max is set.

2, the transfer 16 distributes the driving force output from the power transmission device 14 to the front propeller shaft 18 and the rear propeller shaft 24. The transfer 16 according to the present embodiment is provided between a transmission device 52 for transmitting torque between the output shaft 44 and the front propeller shaft 18, and between the output shaft 44 and the front propeller shaft 18. And a control coupling device 54 that restricts the rotation and controls the front-rear driving force distribution. The control coupling device 54 corresponds to the torque distribution device according to the present invention.

The transmission device 52 is interposed between the drive gear 56 connected to the output shaft 44, the driven gear 60 that is an input rotation member of the control coupling device 54, and the drive gear 56 and the driven gear 60. And an intermediate gear 62 for transmitting power between 56 and 60.

The control coupling device 54 is, for example, a so-called friction engagement device that transmits torque by friction, that is, a friction clutch. Specifically, the control coupling device 54 includes a wet multi-plate type hydraulic friction engagement device in which a plurality of friction plates stacked on each other are pressed by a hydraulic actuator, and both sides on which both are inserted. The rotating member, that is, the driven gear 60 and the coupling output shaft 64 connected in series to the front propeller shaft 18 are selectively connected. In this control coupling device 54, the hydraulic pressure (engagement pressure) of the hydraulic oil supplied to the hydraulic actuator is adjusted by the electronic control device 10 shown in FIG. ) Is continuously changed. Therefore, by adjusting the engagement pressure, the torque distribution ratio between the front drive wheel 30 and the rear drive wheel 32 is 0 (front drive wheel): 100 (rear drive wheel) to 50 (front drive wheel). : 50 (rear drive wheel) is continuously controlled. For example, when the control coupling device 54 is fully engaged, the driven gear 60 and the coupling output shaft 64 rotate integrally, and when the control coupling device 54 is half-engaged. The torque transmitted from the output shaft 44 of the power transmission device 14 to the front propeller shaft 18 changes according to the engagement force. On the other hand, when the control coupling device 54 is disengaged, that is, released, torque transmission between the driven gear 60 and the coupling output shaft 64 is interrupted, and the output torque from the power transmission device 14 is the rear propeller. It is transmitted only to the shaft 24. That is, the vehicle 6 is in a two-wheel drive state by the rear drive wheels 32.

In the transfer 16 configured as described above, torque that distributes output torque from the power transmission device 14 to the front propeller shaft 18 and the rear propeller shaft 24 in accordance with the operating state (engaged state) of the control coupling device 54. The distribution ratio is adjusted. That is, the control coupling device 54 functions as a torque distribution device that distributes the output torque from the power transmission device 14 to the front drive wheels 30 and the rear drive wheels 32. For example, during regenerative braking in front-rear wheel drive traveling, that is, four-wheel drive traveling, the regenerative braking torque Tgr of the second electric motor M2 is transmitted to the rear drive wheel 32 and the front drive wheel 30 is connected to the front drive wheel 30 via the control coupling device 54. The regenerative braking torque Tgr of the second electric motor M2 is transmitted.

Returning to FIG. 1, the vehicle 6 applies a braking torque to the front drive wheel 30 that generates a braking torque on the front drive wheel 30 according to the supplied hydraulic pressure, and to the rear drive wheel 32 according to the supplied hydraulic pressure. A rear wheel hydraulic brake 92 is generated, and a brake hydraulic control circuit 94 that supplies hydraulic pressure to the front wheel hydraulic brake 90 and the rear wheel hydraulic brake 92 is provided. The brake hydraulic control circuit 94 includes, for example, a hydraulic pump and an accumulator that generate hydraulic pressure to perform ABS control and VSC control, and an electromagnetic valve that adjusts the hydraulic pressure supplied to each

hydraulic brake

90 and 92 independently, such as a linear solenoid valve. The electronic control device 10 supplies the hydraulic pressure generated by the master cylinder 98 or the hydraulic pressure generated by the hydraulic pump in accordance with the brake depression force F _BR of the brake pedal 96 and the brake depression speed SPD _BR by the driver. Is supplied to each of the

hydraulic brakes

90 and 92 according to a command from, and the supplied hydraulic pressure is controlled. The braking torque generated on the front drive wheel 30 and the rear drive wheel 32 by the front wheel hydraulic brake 90 and the rear wheel hydraulic brake 92, respectively, is supplied from the brake hydraulic control circuit 94 to the front wheel hydraulic brake 90 and the rear wheel hydraulic brake 92. The hydraulic pressure can be increased or decreased according to the hydraulic pressure supplied to each.

1, the electronic control device 10 is a control device for controlling the operation of the vehicle drive device 8 and the brake hydraulic pressure control circuit 94. The electronic control device 10 includes a plurality of so-called microcomputers including a CPU, a ROM, a RAM, an input / output interface, and the like. The electronic control device 10 uses a temporary storage function of the RAM, and signals according to a program stored in the ROM in advance. Various controls are executed by performing the processing. The various controls include, for example, hybrid drive control that calculates the required outputs of the engine 12 and the electric motor M and gives commands to each device so that the required outputs are obtained, and the engine output that controls the output of the engine according to the commands. Control, motor output control for controlling the operation of the motor M as a driving force source or generator according to the command, and front / rear driving force distribution control for controlling the torque capacity of the control coupling device 54 to control the front / rear driving force distribution and so on.

The electronic control device 10 is supplied with various signals from sensors and switches provided in the vehicle. For example, a signal representing the engine rotational speed Ne from the engine rotational speed sensor 100, a signal representing the rotational speed Nout of the output shaft 44 corresponding to the vehicle speed V from the output shaft rotational speed sensor 102, and a first motor from the first motor rotational speed sensor 104 A signal representing a rotation speed N _{M1 of M1} (hereinafter referred to as a first motor rotation speed N _M1 ), a rotation speed N _M2 of the second motor M2 from the second motor rotation speed sensor 106 (hereinafter referred to as a second motor rotation speed N _M2 ). ), A signal representing the rotation speed Nf of the front drive wheel 30 (hereinafter referred to as front wheel rotation speed Nf) from the front wheel rotation speed sensor 108, and a rotation speed Nr (hereinafter referred to as rear wheel rotation speed sensor 110) of the rear wheel rotation speed sensor 110. a signal representing a) of the rear wheel rotational speed Nr, representative of a brake pedal force F _BR and the brake depression speed SPD _BR from a brake sensor 112 No., detected signal representing the operation amount i.e. the accelerator opening Acc of the accelerator pedal from an accelerator opening sensor 114, the temperature TEMP _CP control coupling device 54 from the coupling temperature sensor 116 (hereinafter, coupling of the ring temperatures TEMP _CP) as A signal representing the hydraulic oil temperature in the control coupling device 54, a signal representing the state of charge SOC of the power storage device 50, that is, the remaining charge SOC, etc. are supplied from the power storage device 50, respectively.

From the electronic control unit 10, for example, a command signal for controlling the output of the engine 12, a command signal for controlling the operation of the electric motor M, a command signal for controlling the operation of the control coupling device 54, brake hydraulic pressure Various signals such as a command signal for controlling the operation of the control circuit 94 are output.

FIG. 3 is a functional block diagram for explaining the main part of the control function provided in the electronic control unit 10. As shown in FIG. 3, the electronic control unit 10 includes a hybrid control unit 120 as a hybrid control unit, a regenerative braking travel determination unit 122 as a regenerative braking travel determination unit, and a vehicle braking force determination unit as a vehicle braking force determination unit. 124, a required charging amount determining unit 126 as a required charging amount determining unit, a torque transmission limit determining unit 128 as a torque transmission limit determining unit, and a maximum allowable regenerative braking torque setting unit 130 as a maximum allowable regenerative braking torque setting unit. And a regenerative braking torque determining unit 132 as a regenerative braking torque determining unit, a front and rear wheel torque distribution control unit 134 as a front and rear wheel torque distribution control unit, and a vehicle braking execution unit 136 as a vehicle braking execution unit. .

3, the hybrid control means 120 controls the operation of the engine 12 and the electric motor M based on various signals supplied to the electronic control device 10 from each sensor, switch, and the like. For example, while instructing the engine output control device 121 to operate the engine 12 in an efficient operating range, the distribution of the driving force between the engine 12 and the second electric motor M2 and the reaction force due to the power generation of the first electric motor M1 The speed ratio γ0 as an electric continuously variable transmission of the power transmission device 14 is controlled by changing it optimally. Further, when the regenerative braking travel determining means 122 described later determines that the regenerative braking traveling should be performed, the hybrid control means 120 sets the first electric motor M1 in the idling state and transmits power from the input shaft 36 to the output shaft 44. While shutting off, the engine 12 is temporarily stopped to improve fuel consumption.

The regenerative braking travel determination means 122 determines whether or not to perform decelerating travel that causes the vehicle 6 to travel while decelerating, that is, regenerative braking travel that brakes the vehicle 6 while regenerating the second electric motor M2. Specifically, the regenerative braking travel determination unit 122 determines whether or not to perform the regenerative braking travel based on the vehicle speed V, the accelerator opening degree Acc, and the like. For example, the regenerative braking is performed when the vehicle speed V is equal to or higher than the determination reference vehicle speed stored in the electronic control device 10 in advance and the accelerator opening Acc is less than the determination reference accelerator opening stored in the electronic control device 10 in advance. Judge that it should run. The determination reference accelerator opening is experimentally set to such a small opening that it can be determined that the accelerator pedal is not depressed, for example. The determination reference vehicle speed is experimentally set to a vehicle speed V at which it can be determined that applying a braking force equal to or higher than an engine brake in a normal engine vehicle is in line with the driver's intention.

When the regenerative braking travel determination unit 122 determines that the regenerative braking travel should be performed, the vehicle braking force determination unit 124 determines a target vehicle braking force that is a target value of the vehicle braking force F _VL in the regenerative braking travel. F _VL * is sequentially determined. From the target vehicle braking force F _{VL *} is made vehicle braking along the intention of the driver driving performance and driving comfort relationships predetermined experimentally so as not to impair, the vehicle speed V, the brake pressing force F _BR, And the brake depression speed SPD _{BR and the} like. For example, the target vehicle braking force F _VL * is determined to increase as the brake depression force F _BR increases.

The requested charge amount determining means 126 sequentially detects the remaining charge SOC of the power storage device 50, and based on the remaining charge SOC determined in advance from an experimentally determined relationship, The required charging amount to be charged, that is, the generated power to be generated by the regenerative operation of the second electric motor M2, is sequentially determined. For example, the requested charge amount determining unit 126 determines the generated power to be generated by the second electric motor M2 as the remaining charge SOC of the power storage device 50 is lower.

The torque transmission restriction determining means 128 determines whether or not the control coupling device 54 is in a torque transmission restricted state in which torque transmission of the control coupling device 54 is restricted from a predetermined normal use, that is, the control coupling device. It is determined whether or not the torque transmission is limited when the torque transmission is limited more than the predetermined normal use. Since the control coupling device 54 is in the torque transmission limit state at a high temperature, specifically, the torque transmission limit determination means 128 sequentially detects the coupling temperature TEMP _CP , and the coupling temperature TEMP _CP is Then, it is sequentially determined whether or not it is equal to or greater than a predetermined coupling temperature determination value TEMP1 so that it can be determined whether or not the torque transmission of the control coupling device 54 is limited. Then, the torque transmission restriction determination unit 128 determines that the torque transmission restriction of the control coupling device 54 is in effect when the coupling temperature TEMP _CP is equal to or higher than the coupling temperature determination value TEMP1. On the other hand, when the coupling temperature TEMP _CP is less than the coupling temperature determination value TEMP1, it is determined that the non-torque transmission limit of the control coupling device 54, that is, the predetermined normal use time. The coupling temperature determination value TEMP1 corresponds to the torque distribution device temperature determination value of the present invention.

Here, the relationship between the maximum torque capacity that is the maximum controllable torque capacity of the control coupling device 54 and the coupling temperature TEMP _CP will be described with reference to FIG. FIG. 4 shows the relationship between the maximum torque capacity and the coupling temperature TEMP _CP . As shown in FIG. 4, as a whole, the maximum torque capacity of the control coupling device 54 tends to decrease as the coupling temperature TEMP _CP is higher, and the predetermined common use shown by being surrounded by a two-dot chain line L01 in FIG. In the normal temperature range, which is the temperature range of the hour, the rate of decrease of the maximum torque capacity with respect to the coupling temperature TEMP _CP is small. However, when the coupling temperature TEMP _CP exceeds the normal temperature range and exceeds the use limit temperature TEMP1, which is a higher temperature, the reduction rate of the maximum torque capacity increases, and the maximum torque capacity is equal to the coupling temperature TEMP _CP. The higher the value, the smaller. Therefore, the control coupling device 54 is normally used in the normal temperature range, but when the coupling temperature TEMP _CP exceeds the use limit temperature TEMP1, the control coupling device 54 causes the torque from the engine 12 or the electric motor M to be used. Is not transmitted to the front drive wheels 30 and the torque transmission is limited. In this case, for example, the vehicle 6 is equivalent to a rear wheel drive vehicle that exclusively exhibits the driving force by the rear drive wheels 32. Therefore, the use limit temperature TEMP1 is experimentally obtained in advance, and the use limit temperature TEMP1 is preset as the coupling temperature determination value TEMP1.

Maximum allowable regenerative braking torque setting means 130, when the vehicle braking force determining means 124 determines a target vehicle braking force F _{VL *,} the upper limit allowable value of the regenerative braking torque Tgr generated by the regenerative operation of the second electric motor M2 T1GR The maximum allowable regenerative braking torque T1gr is sequentially set. For example, the maximum permissible regenerative braking torque T1gr is intended to be set larger as the brake pedal force F _BR is large, for improving the fuel efficiency is the maximum allowable regenerative so that it can regenerate more electrical energy the second electric motor M2 The braking torque T1gr is preferably set large.

Further, the setting condition of the maximum allowable regenerative braking torque T1gr differs depending on the determination of the torque transmission limit determination means 128. That is, if the maximum allowable regenerative braking torque setting means 130 determines that the non-torque transmission limit of the control coupling device 54 is determined by the torque transmission restriction determination means 128, the regenerative braking torque Tgr is equal to the front drive wheel 30. The front drive wheel 30 and the rear drive are assumed to be transmitted to each of the rear drive wheels 32 at a predetermined torque distribution ratio, for example, “50 (front drive wheel): 50 (rear drive wheel)”. The maximum allowable regenerative braking torque T1gr of the second electric motor M2 is set so that each slip of the wheel 32 does not occur. For example, the vehicle speed V, the brake pedaling force F _BR , and the brake are determined based on a relationship that is experimentally determined in advance so that the slip of the front drive wheel 30 and the rear drive wheel 32 does not occur under the predetermined torque distribution ratio. The maximum allowable regenerative braking torque T1gr is set based on the stepping speed SPD _{BR and the} like. On the other hand, when the maximum allowable regenerative braking torque setting means 130 determines that the torque transmission restriction of the control coupling device 54 is at the time of the torque transmission restriction by the torque transmission restriction judgment means 128, the regenerative braking torque Tgr is The maximum allowable regenerative braking torque T1gr of the second electric motor M2 is set so that the rear drive wheel 32 does not slip, assuming that it is transmitted only to the drive wheel 32 and not to the front drive wheel 30. For example, the vehicle speed V and the brake pedal force F _BR are determined based on a relationship that is experimentally determined in advance so that the regenerative braking torque Tgr is transmitted only to the rear drive wheel 32 so that the rear drive wheel 32 does not slip. The maximum allowable regenerative braking torque T1gr is set based on the brake depression speed SPD _{BR and the} like. However, the maximum allowable regenerative braking torque setting means 130 determines whether or not the target vehicle control determined by the vehicle braking force determination means 124 regardless of whether the torque transmission limit of the control coupling device 54 or the non-torque transmission limit. The maximum allowable regenerative braking torque T1gr of the second electric motor M2 is set within a range equal to or less than the torque (target vehicle braking force conversion torque) obtained by converting the power F _VL * into the torque around the output shaft 44. That is, if the maximum allowable regenerative braking torque T1gr set based on the relationship determined experimentally in advance exceeds the target vehicle braking force conversion torque, the maximum allowable regenerative braking torque T1gr is equal to the target vehicle braking force conversion torque. Set to the same value. Since the maximum allowable regenerative braking torque T1gr so is in the range of less than the target vehicle braking force conversion torque, the maximum allowable regenerative braking torque T1gr, the target vehicle braking force F _{VL *} similarly to driving performance and driving comfort It is set so as not to impair the performance. Further, the maximum allowable regenerative braking torque setting means 130 sets the maximum allowable regenerative braking torque T1gr as described above for the non-torque transmission restriction and the torque transmission restriction of the control coupling device 54, respectively. The rear drive wheel 32 slips more when Tgr is transmitted only to the rear drive wheel 32 than when the regenerative braking torque Tgr is transmitted to each of the front drive wheel 30 and the rear drive wheel 32. Since it is easy, the maximum allowable regenerative braking torque setting means 130 sets the maximum allowable regenerative braking torque T1gr smaller than when the non-torque transmission is limited when the torque transmission is limited. For example, the maximum allowable regenerative braking torque T1gr when the torque transmission is limited is set to about half that when the non-torque transmission is limited.

The regenerative braking torque determining means 132 is configured so that when the maximum allowable regenerative braking torque setting means 130 sets the maximum allowable regenerative braking torque T1gr, the second required charging amount determined by the charging request amount determining means 126 is obtained. The regenerative braking torque Tgr of the electric motor M2 is sequentially determined. However, the regenerative braking torque determining means 132 determines the regenerative braking torque Tgr within a range equal to or less than the maximum allowable regenerative braking torque T1gr determined by the maximum allowable regenerative braking torque setting means 130. In other words, the regenerative braking torque determination means 132 limits the regenerative braking torque Tgr to the maximum allowable regenerative braking torque T1gr or less. For example, if the regenerative braking torque Tgr determined so as to obtain the required charging amount exceeds the maximum allowable regenerative braking torque T1gr, the regenerative braking torque Tgr is set to the same value as the maximum allowable regenerative braking torque T1gr. . As described above, the regenerative braking torque determining means 132 limits the regenerative braking torque Tgr of the second electric motor M2 to the maximum allowable regenerative braking torque T1gr or less, and as described above, the maximum allowable regenerative braking torque T1gr when the torque transmission is limited is As a result, the regenerative braking torque determining unit 132 sets the regenerative braking torque Tgr smaller than that when the non-torque transmission is limited. It will be. In other words, when the maximum allowable regenerative braking torque setting means 130 sets the maximum allowable regenerative braking torque T1gr smaller than when the torque transmission is limited, the regenerative braking torque determination means 132 sets the torque transmission limit. Sometimes the regenerative braking torque Tgr is determined to be smaller than when the non-torque transmission is limited.

The front and rear wheel torque distribution control means 134 determines that the torque transmission restriction judgment means 128 determines that the non-torque transmission restriction of the control coupling device 54 is occurring. The torque distribution ratio of the regenerative braking torque Tgr transmitted to each is sequentially determined, and the torque capacity of the control coupling device 54 is hydraulically controlled so that the determined torque distribution ratio is achieved. For example, the torque distribution ratio of the regenerative braking torque Tgr is expressed by the slip ratio of the rear drive wheel 32 calculated from the rotational speed difference (= Nr−Nf) between the front wheel rotational speed Nf and the rear wheel rotational speed Nr. Based on a predetermined vehicle state, a predetermined relationship (map) is determined so that each of the front drive wheels 30 and the rear drive wheels 32 does not slip. In short, the front-rear wheel torque distribution control means 134 is the same as the front-rear wheel drive control (four-wheel drive control, 4WD control) generally performed during front-rear wheel drive travel (four-wheel drive travel, 4WD travel). Thus, the torque capacity of the control coupling device 54 is controlled based on the vehicle state so that the front drive wheel 30 and the rear drive wheel 32 do not slip or are unlikely to slip.

On the other hand, the front and rear wheel torque distribution control means 134 controls the torque capacity of the control coupling device 54 when it is determined by the torque transmission restriction determination means 128 that the torque transmission limit of the control coupling device 54 is present. Do not perform hydraulic control.

When the regenerative braking torque determining unit 132 determines the regenerative braking torque Tgr of the second electric motor M2, the vehicle braking execution unit 136 outputs the regenerative braking torque Tgr from the second electric motor M2. The motor regenerative braking control for controlling the motor is executed. Furthermore, when the regenerative braking force Fgr generated by the regenerative braking control of the electric motor (regenerative braking torque Tgr converted into the braking force) is less than the target vehicle braking force _FVL * determined by the vehicle braking force determination means 124. The deficiency (= F _VL * −Fgr) of the regenerative braking force Fgr with respect to the target vehicle braking force F _VL * is compensated by the mechanical braking force Fm generated by the operation of the front wheel hydraulic brake 90 and the rear wheel hydraulic brake 92. Hydraulic brake combined braking control is executed in parallel with the electric motor regenerative braking control. As a result, the vehicle braking execution means 136 makes the vehicle braking force F _VL (= Fm + Fgr), which is the sum of the mechanical braking force Fm and the regenerative braking force Fgr, coincide with the target vehicle braking force F _VL *. be able to. The total of the front wheel side mechanical braking force Fmf due to the operation of the front wheel hydraulic brake 90 and the rear wheel side mechanical braking force Fmr due to the operation of the rear wheel hydraulic brake 92 is the mechanical braking force Fm. In the hydraulic brake combined braking control, each of the front wheel side mechanical braking force Fmf and the rear wheel side mechanical braking force Fmr is determined by the vehicle braking force F _VL ( = Femf + Femr) and the front wheel braking force Femf exerted from charge fraction i.e. front drive wheels 30 of the front drive wheels 30 of the vehicle braking force F representative fraction i.e. the rear drive wheel of the side drive wheels 32 after of _VL 32 Is controlled so that the relationship with the rear wheel braking force Femr exerted from the above approaches a predetermined ideal braking force distribution curve L0 _BR (see FIG. 5). Therefore, in the hydraulic brake combined braking control, if the front and rear wheel torque distribution control means 134 changes the torque distribution ratio of the regenerative braking torque Tgr to the front drive wheels 30 and the rear drive wheels 32 by the hydraulic control of the control coupling device 54. The front wheel side mechanical braking force Fmf and the rear wheel side mechanical braking force Fmr are changed according to the change in the torque distribution ratio. This control will be described with reference to FIG. Note that the ideal braking force distribution curve L0 _BR is experimentally determined in advance so as to stabilize the vehicle behavior during vehicle braking, and is stored in the electronic control unit 10.

FIG. 5 is a diagram illustrating the relationship between the front wheel braking force Femf and the rear wheel braking force Femr when the torque transmission is restricted and when the non-torque transmission is restricted. In FIG. 5, the horizontal axis represents the front wheel braking force Femf, the vertical axis represents the rear wheel braking force Femr, and the ideal braking force distribution curve L0 _BR passes through the origin (Femf = 0, Femr = 0) and the front wheel braking force Femf is It is expressed as a straight line with a constant gradient that increases as the rear wheel braking force Femr increases.

First, the non-torque transmission restriction will be described. In Figure 5, when the non-torque transmission limited, the maximum allowable regenerative braking force F1gr obtained by converting the maximum permissible regenerative braking torque T1gr the braking force is the one configured to G _4WD. Then, the regenerative braking limit line which is a straight line L0 _4WD connecting the G _4WD on G _4WD and the vertical axis on the horizontal axis in FIG. 5 represents the maximum allowable regenerative braking force F1gr during the non-torque transmission limited. The regenerative braking limit line is a boundary line corresponding to the maximum allowable regenerative braking force F1gr and indicating the allowable limit of regenerative braking by the second electric motor M2. Specifically, the regenerative braking limit line will be described. If the regenerative braking force Fgr is determined in the regenerative braking possible region A0 _4WD on the origin side in FIG. 5 with L0 _4WD as a boundary, the regenerative braking torque Tgr is determined within the range of the maximum allowable regenerative braking torque T1gr or less. It will be. In FIG. 5, for example, the regenerative braking point indicating the regenerative braking force Fgr when the regenerative braking torque Tgr is determined to be the same value as the maximum allowable regenerative braking torque T1gr when the non-torque transmission is limited is indicated as a point P0 _4WD. Yes. The sum of the front wheel braking force Femf (horizontal axis) indicated by the regenerative braking point P0 _4WD and the rear wheel braking force Femr (vertical axis) is the regenerative braking force Fgr, and the front wheel braking force Femf (lateral) indicated by the regenerative braking point P0 _4WD. The ratio between the shaft) and the rear wheel braking force Femr (vertical axis) is determined according to the torque capacity of the control coupling device 54 controlled by the front and rear wheel torque distribution control means 134. Further, when the regenerative braking force Fgr showing the regenerative braking point P0 _4WD is less than the target vehicle braking force F _{VL *} is the execution of the hydraulic brake combination brake control, the front wheel braking force Femf and a rear wheel braking force Femr The mechanical braking force Fm is generated so that the relationship approaches the ideal braking force distribution curve L0 _BR . FIG. 5 shows an example of a relationship between the front wheel braking force Femf and the rear wheel braking force Femr in the hydraulic brake combined braking control when the non-torque transmission is limited as a point P1 _4WD . In the hydraulic brake combined braking control, the difference between the point P1 _4WD and the regenerative braking point P0 _4WD in FIG. 5 indicates the front wheel side mechanical braking force Fmf and the rear wheel side mechanical braking force Fmr. In FIG. 5, since the difference in the vertical axis direction between the point P1 _4WD and the regenerative braking point P0 _4WD is zero, the rear wheel side mechanical braking force Fmr is zero, and the point P1 _4WD and the regenerative braking point P0 _4WD The difference DF01 _{4WD in} the horizontal axis direction represents the front wheel side mechanical braking force Fmf.

Next, the torque transmission restriction time will be described. In Figure 5, when the torque transfer limit, maximum allowable regenerative braking force F1gr is the one configured to G _FR. When the torque transmission is limited, the control coupling device 54 can hardly transmit torque, so the traveling state of the vehicle 6 is exclusively the two-wheel drive state by the rear drive wheels 32, that is, the FR traveling state or a traveling state equivalent thereto. The maximum allowable regenerative braking torque T1gr during the torque transmission limited as described above is set to be smaller than when the non-torque transmission limited, G _FR in FIG. 5 is set to be smaller than G _4WD. Then, the regenerative braking limit line of the straight line L0 _FR connecting the G _FR on G _FR and the vertical axis on the horizontal axis in FIG. 5 represents the maximum allowable regenerative braking force F1gr when the torque transfer limit. Specifically, if the regenerative braking force Fgr is determined within the regenerative braking possible region A0 _FR on the origin side in FIG. 5 with the regenerative braking limit line L0 _FR as a boundary, the regenerative braking torque Tgr is the maximum allowable regenerative braking. It is determined within the range of torque T1gr or less. In FIG. 5, for example, the regenerative braking point indicating the regenerative braking force Fgr when the regenerative braking torque Tgr is determined to be the same value as the maximum allowable regenerative braking torque T1gr when the torque transmission is limited is shown as a point P0 _FR . . Since the traveling state of the vehicle 6 when the torque transmission is limited is the FR traveling state or a traveling state equivalent thereto, the front wheel braking force Femf (horizontal axis) indicated by the regenerative braking point P0 _FR is zero or substantially zero. In other words, the regenerative braking point P0 _FR is on the vertical axis or substantially on the vertical axis. When the regenerative braking force Fgr indicated by the regenerative braking point P0 _FR is less than the target vehicle braking force F _VL *, the front wheel is controlled by executing the hydraulic brake combined braking control as in the non-torque transmission restriction. The mechanical braking force Fm is generated so that the relationship between the braking force Femf and the rear wheel braking force Femr approaches the ideal braking force distribution curve L0 _BR . FIG. 5 shows an example of the relationship between the front wheel braking force Femf and the rear wheel braking force Femr in the hydraulic brake combined braking control when the torque transmission is limited as a point P1 _FR . In the hydraulic brake combination brake control, in the same manner as when the non-torque transmission limited, in FIG. 5, the horizontal axis direction of the difference DF01 _FR between the point P1 _FR regenerative braking point P0 _FR is a front-wheel-side mechanical braking force Fmf In addition, the difference DF02 _{FR in} the vertical axis direction between the point P1 _FR and the regenerative braking point P0 _FR represents the rear wheel side mechanical braking force Fmr.

FIGS. 6 and 7 are flowcharts for explaining a main part of the control operation of the electronic control unit 10, that is, a control operation for generating the vehicle braking force _FVL when the vehicle 6 performs regenerative braking traveling. The flowchart of FIG. 6 is repeatedly executed with an extremely short cycle time of, for example, about several milliseconds to several tens of milliseconds, and the flowchart of FIG. 7 is executed at step (hereinafter, “step” is omitted) SA3 of FIG. It is a subroutine.

In FIG. 6, in SA1 corresponding to the regenerative braking traveling determination means 122, it is determined whether or not the regenerative braking traveling should be performed. The determination is made based on, for example, the vehicle speed V and the accelerator opening Acc. If the determination of SA1 is affirmative, that is, if the regenerative braking travel is to be performed, the process proceeds to SA2. On the other hand, if the determination of SA1 is negative, the flowchart of FIG. 6 ends.

In SA2 corresponding to the vehicle braking force determining means 124, the target vehicle braking force _FVL * in the regenerative braking traveling is determined. After SA2, the process proceeds to SA3.

In SA3, the regenerative braking travel is performed. In other words, the vehicle braking force F _VL is controlled to coincide with the target vehicle braking force F _VL * while the regenerative operation of the second electric motor M2 is performed during vehicle travel. Specifically, the flowchart of FIG. 7 is executed. When the flowchart of FIG. 7 ends, SA3 ends. Therefore, the flowchart of FIG. 6 ends and is executed again from SA1.

7, the remaining charge SOC of the power storage device 50 is detected, and the state of the remaining charge SOC is determined. Specifically, the generated power to be generated by the second electric motor M2 in the regenerative braking traveling is determined based on the remaining charge SOC of the power storage device 50. For example, the generated power is determined to be larger as the remaining charge SOC of the power storage device 50 is lower. Moreover, the regenerative braking torque Tgr of the second electric motor M2 determined in SB4 or SB8 described later increases as the generated power increases. That is, the regenerative braking torque Tgr increases as the remaining charge SOC of the power storage device 50 decreases. After SB1, the process proceeds to SB2. Note that SB1 corresponds to the charge request amount determination unit 126.

In SB2 corresponding to the torque transmission restriction determination means 128, a state determination is made as to whether the 4WD system for performing the four-wheel drive traveling normally operates without any restriction. Specifically, it is determined whether or not the control coupling device 54 is normal, in other words, whether or not the non-torque transmission limit of the control coupling device 54 is in effect. The determination is made based on the coupling temperature TEMP _CP . That is, when the coupling temperature TEMP _CP is lower than the coupling temperature determination value TEMP1, it is determined that the non-torque transmission limit of the control coupling device 54 is being reached. On the other hand, when the coupling temperature TEMP _CP is equal to or higher than the coupling temperature determination value TEMP1, it is determined that the torque transmission of the control coupling device 54 is limited. If the determination of SB2 is affirmative, that is, if the coupling temperature TEMP _CP is less than the coupling temperature determination value TEMP1, it is determined that the non-torque transmission limit of the control coupling device 54 is present, and SB3 Move on. On the other hand, when the determination of SB2 is negative, that is, when the coupling temperature TEMP _CP is equal to or higher than the coupling temperature determination value TEMP1, it is determined that the torque transmission of the control coupling device 54 is limited, Move on to SB7.

In SB3 corresponding to the maximum allowable regenerative braking torque setting means 130, the regenerative braking torque Tgr is transmitted to each of the front drive wheels 30 and the rear drive wheels 32 at a predetermined torque distribution ratio, in other words, regenerative braking. Assuming that four-wheel regenerative braking is performed in which torque Tgr is transmitted to each of the front drive wheel 30 and the rear drive wheel 32, the maximum allowable regenerative braking torque T1gr is set to each of the front drive wheel 30 and the rear drive wheel 32. Is set so that no slip occurs. However, in SB3, the maximum allowable regenerative braking torque T1gr is set within the range of the target vehicle braking force conversion torque below corresponding to SA2 target vehicle braking force F _{VL *} determined in the FIG. After SB3, the process proceeds to SB4.

In SB4 corresponding to the regenerative braking torque determining means 132, the regenerative braking torque Tgr of the second electric motor M2 is determined (set) so as to obtain the generated power determined in SB1. However, the regenerative braking torque Tgr is limited to the maximum allowable regenerative braking torque T1gr set in SB3. After SB4, the process proceeds to SB5.

In SB5, the vehicle state represented by the slip ratio of the rear drive wheel 32 is determined. In other words, such a vehicle state is detected or estimated. For example, the ease of slipping of the

wheels

30 and 32 such as road surface conditions is determined. After SB5, the process proceeds to SB6.

In SB6, the torque distribution ratio of the regenerative braking torque Tgr transmitted to each of the front drive wheels 30 and the rear drive wheels 32 is determined based on the vehicle state determined in SB5. Then, hydraulic control for controlling the torque capacity of the control coupling device 54 is performed so that the determined torque distribution ratio is achieved. As a result, the regenerative braking torque Tgr is also distributed to the front drive wheels 30. SB5 and SB6 correspond to the front and rear wheel torque distribution control means 134.

In SB7 corresponding to the maximum allowable regenerative braking torque setting means 130, it is assumed that the regenerative braking torque Tgr is transmitted only to the rear drive wheel 32 and not to the front drive wheel 30, in other words, the regenerative braking torque Tgr is rear side. Assuming that two-wheel regenerative braking (FR regenerative braking) transmitted only to the drive wheels 32 is performed, the maximum allowable regenerative braking torque T1gr is set so that the rear drive wheels 32 do not slip. Therefore, as illustrated in the relationship of “G _FR <G _4WD ” in FIG. 5, the maximum allowable regenerative braking torque T1gr is set when set at SB7 than when set at SB3. It will be set smaller. However, as with the SB3 At SB7, the maximum allowable regenerative braking torque T1gr is set within a range of the target vehicle braking force conversion torque corresponding to the target vehicle braking force F _{VL *} determined at SA2 of FIG. 6 Is done. After SB7, the process proceeds to SB8.

In SB8 corresponding to the regenerative braking torque determining means 132, the regenerative braking torque Tgr of the second electric motor M2 is determined (set) so as to obtain the generated power determined in SB1. However, the regenerative braking torque Tgr is limited to the maximum allowable regenerative braking torque T1gr set in SB7. After SB8, the process proceeds to SB9.

In SB9, the regenerative braking force Fgr obtained by converting the regenerative braking torque Tgr determined at SB4 or SB8 in braking force, whether less than SA2 the target vehicle braking force F _{VL *} determined in the FIG. 6 Is judged. If the determination in SB9 is affirmative, i.e., when the regenerative braking force Fgr is less than the target vehicle braking force F _{VL *} proceeds to SB 10. On the other hand, if the determination at SB9 is negative, the operation proceeds to SB11.

In SB10, the electric motor regenerative braking control for controlling the second electric motor M2 is executed such that the regenerative braking torque Tgr determined in SB4 or SB8 is output from the second electric motor M2. At the same time, the brake control combined with the hydraulic brake is executed by a command to the brake hydraulic control circuit 94. In the brake control combined with hydraulic brake 94, one or both of the front-wheel hydraulic brake 90 and the rear-wheel hydraulic brake 92 It is actuated so as to compensate for the shortage of the power Fgr with respect to the target vehicle braking force F _{VL *.}

In SB11, the electric motor regenerative braking control is executed so that the regenerative braking torque Tgr determined in SB4 or SB8 is output from the second electric motor M2. However, the hydraulic brake combined braking control is not executed. SB9 to SB11 correspond to the vehicle braking execution means 136.

As described above, according to the present embodiment, the regenerative braking torque determination means 132 sets the regenerative braking torque Tgr of the second electric motor M2 when the torque transmission limit of the control coupling device 54 is less than when the non-torque transmission is limited. Set smaller. Further, if the regenerative braking torque Tgr of the second electric motor M2 is not different from that at the non-torque transmission limit when the torque transmission is restricted, the rear drive wheels 32 slip and the vehicle compared with the non-torque transmission restriction. The behavior tends to be unstable. Accordingly, the stability of the vehicle behavior is improved during the regenerative braking of the vehicle 6 as compared with the case where the regenerative braking torque Tgr of the second electric motor M2 is generated without taking into account the torque transmission limitation of the control coupling device 54. Can be made. In particular, such an effect of the present embodiment becomes remarkable on a low μ road where the friction coefficient of the

wheels

30 and 32 against the road surface is small, such as an icy road.

Further, according to the present embodiment, the time when the torque transmission of the control coupling device 54 is limited is a case where the coupling temperature TEMP _CP is equal to or higher than the predetermined coupling temperature determination value TEMP1. Therefore, by detecting the coupling temperature TEMP _CP , it is possible to easily determine whether or not the torque transmission of the control coupling device 54 is limited.

Further, according to the present embodiment, the regenerative braking torque Tgr of the second electric motor M2 is limited to the maximum allowable regenerative braking torque T1gr or less, and the maximum allowable regenerative braking torque T1gr is set when the torque transmission is limited by the control coupling device 54. The regenerative braking torque Tgr is determined to be smaller than that when the non-torque transmission is restricted by setting the torque smaller than when the non-torque transmission is restricted. Therefore, the regenerative braking torque of the electric motor can be easily reduced by changing the setting of the maximum allowable regenerative braking torque T1gr.

Further, according to the present embodiment, when the maximum allowable regenerative braking torque setting unit 130 determines that the torque transmission limit of the control coupling device 54 is determined by the torque transmission limit determination unit 128, the regenerative braking is performed. Assuming that the torque Tgr is transmitted only to the rear drive wheel 32 and not to the front drive wheel 30, the maximum allowable regenerative braking torque T1gr of the second electric motor M2 is set so that the rear drive wheel 32 does not slip. . Accordingly, the regenerative braking torque Tgr of the second electric motor M2 is limited to a size equivalent to that of a two-wheel drive vehicle that travels by driving only the rear drive wheels 32, that is, a rear wheel drive vehicle, and is equivalent to that of a rear wheel drive vehicle. Since the torque distribution ratio of the front and rear wheels is the torque distribution ratio at which the rear drive wheels 32 are most likely to slip, the slip of the rear drive wheels 32 is sufficiently suppressed, and the stability of the vehicle behavior can be sufficiently ensured.

As mentioned above, although the Example of this invention was described in detail based on drawing, this is an embodiment to the last, and this invention is implemented in the aspect which added various change and improvement based on the knowledge of those skilled in the art. Can do.

For example, in the above-described embodiment, the control coupling device 54 is constituted by a wet multi-plate hydraulic friction engagement device, but one or two bands wound around the outer peripheral surface of the rotating drum. It may be a band brake or the like whose one end is tightened by a hydraulic actuator, or may be a control coupling device constituted by an electromagnetic clutch or a magnetic powder clutch.

Further, in the above-described embodiment, in SB2 of FIG. 7, it is determined whether or not the torque transmission of the control coupling device 54 is limited when the torque transmission is limited more than a predetermined normal use. Although it is made based on the ring temperature TEMP _CP , it may be made based on a state quantity other than the coupling temperature TEMP _CP . For example, in the case of coupling failure, in addition to the coupling temperature, abnormal noise, vibration, input / output speed difference, actuator stroke amount, in the case of hydraulic coupling, detection of hydraulic abnormality, electrical control coupling The case may be made based on short circuit detection or the like.

In the above-described embodiment, the vehicle drive device 8 includes the power distribution mechanism 46 and the first electric motor M1 as a differential mechanism. For example, the vehicle drive device 8 includes the first electric motor M1 and the power distribution mechanism 46. Alternatively, it may be a drive device for a so-called parallel hybrid vehicle in which the engine 12, the clutch, the second electric motor M2, and the output shaft 44 are connected in series. In addition, since the said clutch between the engine 12 and the 2nd electric motor M2 is provided as needed, the structure for which the said drive device for parallel hybrid vehicles is not equipped with the clutch can also be considered.

In the above-described embodiment, the vehicle 6 includes the engine 12, the power distribution mechanism 46, and the first electric motor M1, but for example, as shown in FIG. 8, the engine 12, the power distribution mechanism 46, and the first electric motor. A so-called electric vehicle that travels with the power from the second electric motor M2 without the M1 may be used.

In the above-described embodiment, the vehicle 6 is a four-wheel drive vehicle based on the rear wheel drive system, but may be a four-wheel drive vehicle based on the front wheel drive system. For example, in a four-wheel drive vehicle based on the front wheel drive system, the control coupling device 54 is not interposed between the transmission device 52 and the front drive wheel 30, and the transmission device 52 and the rear drive wheel 32 Intervened in between. When the vehicle 6 is a four-wheel drive vehicle based on the front wheel drive system, the front drive wheel 30 corresponds to one wheel of the present invention, and the rear drive wheel 32 corresponds to the other wheel of the present invention. To do. 7, assuming that the regenerative braking torque Tgr is transmitted only to the front drive wheel 30 and not to the rear drive wheel 32, the maximum allowable regenerative braking torque T1gr does not cause the front drive wheel 30 to slip. Is set as follows.

In FIG. 2 of the above-described embodiment, the ring gear R0 and the second electric motor M2 of the power distribution mechanism 46 are directly connected to the output shaft 44 of the power transmission device 14. However, a manual transmission or an automatic transmission is used for the ring gear R0. In addition, it may be interposed between the second electric motor M2 and the output shaft 44.

6: Vehicle (front and rear wheel drive vehicle)
10: Electronic control device (drive control device)
30: Front drive wheel (front wheel, other wheel)
32: Rear drive wheel (rear wheel, one wheel)
54: Control coupling device (torque distribution device)
M2: Second electric motor (electric motor)

Claims

During regenerative braking in front and rear wheel drive traveling, the regenerative braking torque of the electric motor is transmitted to one of the front wheels and the rear wheels, and the other wheels of the front wheels and the rear wheels are A drive control device for front and rear wheel drive vehicles to which a regenerative braking torque of an electric motor is transmitted,
Drive control for front and rear wheel drive vehicles characterized in that, when torque transmission is restricted in which torque transmission of the torque distribution device is restricted, the regenerative braking torque of the electric motor is made smaller than that when non-torque transmission of the torque distribution device is restricted. apparatus.
2. The drive control for front and rear wheel drive vehicles according to claim 1, wherein the time when the torque transmission is limited is a case where the temperature of the torque distribution device is equal to or higher than a predetermined torque distribution device temperature determination value. apparatus.
The regenerative braking torque of the electric motor is limited to a predetermined maximum allowable regenerative braking torque or less,
When the torque transmission is limited, the maximum allowable regenerative braking torque is set to be smaller than that when the non-torque transmission is limited, so that the regenerative braking torque of the motor is smaller than when the torque transmission is limited. The drive control device for a front and rear wheel drive vehicle according to claim 1 or 2.
The maximum allowable regenerative braking torque is set so that the regenerative braking torque of the electric motor is not transmitted to the other wheel when the torque transmission is limited, so that the slip of the one wheel does not occur. 4. A drive control device for a front and rear wheel drive vehicle according to 3.