Vehicle Control System

Abstract

To provide a vehicle control system that can suppress shortage of braking force and destabilization of vehicle behavior when eliminating slipping states in wheels.SOLUTION: A vehicle control system 10 includes: an electric braking control part 21 that controls a fluid-pressure generating part 51; a behavior control part 23 that controls brake mechanisms 15FL, 15FR, 15RL and 15RR; a front motor control part 25a and a rear motor control part 25b that control rotary electric machines 11a and 11b; and an integral control part 27. The behavior control part 23 shuts off distribution of working media of the fluid-pressure generating part 51 to the front brake mechanisms 15FL and 15FR, when slipping states occur in front wheels Fr during execution of regenerative braking by the front motor control part 25a. The electric braking control part 21 increases pressure of a pressure medium of the fluid-pressure generating part 50 more, in comparison with when the slipping states do not occur in the front wheels Fr.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a vehicle control system. [Background technology]

[0002] In recent years, efforts to provide access to sustainable transport systems that take into consideration vulnerable transport participants such as the elderly, people with disabilities, and children have been gaining momentum. To achieve this, we are focusing on research and development to further improve transport safety and convenience through development of vehicle behavior stability. Conventionally, a control device is known that predicts the start of antilock brake control operation and increases frictional braking force and reduces regenerative braking force in advance, thereby suppressing a sudden decrease in deceleration caused by a delayed response of frictional braking force (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-35840 Summary of the Invention [Problem to be solved by the invention]

[0004] In terms of vehicle behavior stability, when wheel slip occurs during deceleration by regenerative braking, it is important to resolve the slip state while suppressing insufficient braking force and destabilization of vehicle behavior. For example, the control device of the above-mentioned prior art controls friction braking force and regenerative braking force before the start of anti-lock brake control operation, but it is difficult to accurately predict vehicle behavior that changes depending on the road surface, braking state, etc., and there is a risk that an appropriate braking force cannot be ensured. For example, when regenerative braking force is switched to friction braking force in conjunction with the operation of anti-lock brake control, there is a risk that the braking force will be insufficient due to pressure fluctuations caused by the opening and closing of valves in the hydraulic circuit for friction braking.

[0005] The present invention aims to solve the above-mentioned problems by suppressing insufficient braking force and destabilization of vehicle behavior when eliminating wheel slippage, thereby contributing to the development of sustainable transportation systems. [Means for solving the problem]

[0006] In order to solve the above problems and achieve the above object, the present invention employs the following aspects. (1): A vehicle control system according to one aspect of the present invention (for example, vehicle control system 10 in the embodiment) includes a rotating electric machine control unit (for example, front motor control unit 25a, rear motor control unit 25b in the embodiment) that controls the operation of a rotating electric machine (for example, front rotating electric machine 11a, rear rotating electric machine 11b in the embodiment) that transfers torque between predetermined wheels (for example, front wheels Fr, rear wheels Rr in the embodiment), and friction braking mechanisms (for example, first front brake mechanism 15FL, second front brake mechanism 15F in the embodiment) for a plurality of wheels (for example, front wheels Fr and rear wheels Rr in the embodiment) including the predetermined wheels. and a friction braking control unit (e.g., electric braking control unit 21 and behavior control unit 23 in the embodiment) that controls the operation of a pressure system (e.g., hydraulic system 50 in the embodiment) that drives the first rear brake mechanism 15R, first rear brake mechanism 15RL, and second rear brake mechanism 15RR) with a pressure medium (e.g., working medium in the embodiment), and if a slippage state occurs in the specified wheel when regenerative braking is performed by the rotating electric machine control unit, the friction braking control unit blocks the flow of the pressure medium to the friction braking mechanism of the specified wheel and increases the pressure of the pressure medium compared to when the slippage state does not occur.

[0007] (2): In the vehicle control system described in (1) above, when a slippage occurs in the specified wheel, the friction braking control unit may increase the pressure of the pressure medium compared to when the slippage does not occur by setting the pressure of the pressure medium in correspondence with the friction braking torque (e.g., total increased friction braking torque TrT in the embodiment) obtained by multiplying the regenerative braking torque (e.g., reversal friction braking torque TrS in the embodiment) reduced by the rotary electric machine control unit by a specified coefficient (e.g., the reciprocal of a specified rear brake coefficient k in the embodiment) while blocking the flow of the pressure medium to the friction braking mechanism of the specified wheel.

[0008] (3): In the vehicle control system described in (1) or (2) above, when the friction braking control unit releases the blockage of the flow of the pressure medium to the friction braking mechanism of the specified wheel, the friction braking control unit may terminate the control to increase the pressure of the pressure medium after a predetermined time compared to when the slip state does not occur. [Effects of the Invention]

[0009] According to the above (1), the friction braking control unit can promote the elimination of the slippage of the specified wheel by blocking the flow of pressure medium to the friction braking mechanism of the specified wheel. The friction braking control unit can prevent a shortage of friction braking force across the entire vehicle by increasing the pressure of the pressure medium flowing to the friction braking mechanisms of wheels other than the specified wheel compared to when no slippage occurs. The friction braking control unit can prevent a shortage of braking force and destabilization of vehicle behavior when eliminating the slippage of the specified wheel.

[0010] In the case of (2) above, the rotating electric machine control unit can promote elimination of the slippage of the specified wheel by switching the regenerative braking torque of the specified wheel to friction braking torque of a wheel other than the specified wheel. When switching to friction braking torque, the friction braking control unit increases the pressure of the pressure medium so as to include the friction braking torque that is insufficient due to the interruption of the flow of pressure medium to the friction braking mechanism of the specified wheel, thereby preventing a shortage of braking force (the sum of friction braking force and regenerative braking force) for the entire vehicle.

[0011] In the case of (3) above, the friction braking control unit releases the blockage of the pressure medium flow to the friction braking mechanism of the specified wheel when the slippage of the specified wheel is resolved, and by terminating the control to increase the pressure of the pressure medium, it is possible to prevent the friction braking force of the entire vehicle from becoming excessive.The friction braking control unit reduces the increase in pressure of the pressure medium to zero after a specified time, thereby preventing abrupt fluctuations in the friction braking force and destabilization of vehicle behavior. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a configuration diagram of a vehicle control system according to an embodiment of the present invention. [Figure 2] 1 is a block diagram showing a functional configuration of a vehicle control system according to an embodiment of the present invention. [Figure 3] FIG. 2 is a configuration diagram of a hydraulic system in the vehicle control system according to the embodiment of the present invention. [Figure 4] FIG. 3 is a diagram showing an example of the correspondence relationship between the vehicle speed, the valve open flag, the braking force, the pressure of the hydraulic system, and the braking torque in the vehicle control system according to the embodiment of the present invention. [Figure 5] FIG. 4 is a diagram showing an example of a correspondence relationship between a valve open flag and a pressure of a hydraulic system in the vehicle control system according to the embodiment of the present invention and a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A vehicle control system according to an embodiment of the present invention will now be described with reference to the accompanying drawings. Fig. 1 is a configuration diagram of a vehicle control system 10 according to an embodiment. Fig. 2 is a block diagram showing the functional configuration of the vehicle control system 10 according to an embodiment. The vehicle control system 10 of the embodiment is mounted on an electric vehicle (vehicle) such as an electric vehicle, a hybrid vehicle, or a fuel cell vehicle. An electric vehicle is driven by a battery as a power source. A hybrid vehicle is driven by a battery and an internal combustion engine as a power source. A fuel cell vehicle is driven by a fuel cell as a power source. Vehicles equipped with the vehicle control system 10 include, for example, front-wheel drive vehicles equipped with a rotating electric motor that generates power for the front wheels, rear-wheel drive vehicles equipped with a rotating electric motor that generates power for the rear wheels, or all-wheel drive vehicles equipped with a rotating electric motor that generates power for both the front and rear wheels.

[0014] As shown in Figures 1 and 2, a vehicle 1 equipped with a vehicle control system 10 includes, for example, a front rotating electric machine 11a and a rear rotating electric machine 11b, a front differential device 13a and a rear differential device 13b, a first front brake mechanism 15FL and a second front brake mechanism 15FR, a first rear brake mechanism 15RL and a second rear brake mechanism 15RR, and a processing device 17.

[0015] The front rotating electric machine 11a exchanges torque with the left and right front wheels Fr, for example, via a front differential 13a. The rear rotating electric machine 11b exchanges torque with the left and right rear wheels Rr, for example, via a rear differential 13b. Each rotating electric machine 11a, 11b is, for example, a three-phase AC brushless DC motor. Each rotating electric machine 11a, 11b generates drive torque for each wheel Fr, Rr by performing power running operation using power supplied from a power conversion device or the like. Each rotating electric machine 11a, 11b performs regenerative operation using rotational power input from each front wheel Fr and each rear wheel Rr, thereby generating power and regenerative braking torque for each front wheel Fr and each rear wheel Rr.

[0016] The front differential 13a connects, for example, the front rotating electric machine 11a to the left and right front wheels Fr. The rear differential 13b connects, for example, the rear rotating electric machine 11b to the left and right rear wheels Rr. Each of the differentials 13a, 13b is, for example, a bevel gear type differential mechanism, and is an open differential that does not have a so-called limited slip differential mechanism. The first front brake mechanism 15FL and the second front brake mechanism 15FR are, for example, friction braking mechanisms provided on the left and right front wheels Fr, respectively. The first rear brake mechanism 15RL and the second rear brake mechanism 15RR are, for example, friction braking mechanisms provided on the left and right rear wheels Rr, respectively. Each of the brake mechanisms 15FL, 15FR, 15RL, and 15RR includes a disc brake, a drum brake, or the like connected to a hydraulic pressure generating unit 51 (described later) that generates hydraulic pressure, for example. Each of the brake mechanisms 15FL, 15FR, 15RL, and 15RR performs friction braking on each of the front wheels Fr and rear wheels Rr, for example, by hydraulic pressure generated by an actuator of the hydraulic pressure generating unit 51 in response to operation of a brake operator by an operator.

[0017] The processing device 17 includes, for example, an electric braking control unit 21, a behavior control unit 23, a front motor control unit 25a, a rear motor control unit 25b, and an integrated control unit 27. Each of the control units 21, 23, 25a, 25b, and 27 is a software function unit that functions when a processor such as a CPU (Central Processing Unit) executes a predetermined program. The software function unit is an ECU that includes a processor such as a CPU, a ROM (Read Only Memory) that stores the program, a RAM (Random Access Memory) that temporarily stores data, and electronic circuits such as a timer. At least a part of each of the control units 21, 23, 25a, 25b, and 27 may be an integrated circuit such as an LSI (Large Scale Integration).

[0018] The vehicle control system 10 of the embodiment includes, for example, a processing device 17 and various sensors mounted on the vehicle 1. The processing device 17 acquires detection value signals output from various sensors of the vehicle 1, and comprehensively controls the rotating electric machines 11a, 11b and the brake mechanisms 15FL, 15FR, 15RL, 15RR. The various sensors include, for example, an operation amount sensor 31, a rotation sensor 33, an acceleration sensor 35, a wheel speed sensor 37, a current sensor 39, a voltage sensor 41, and a temperature sensor 43. The operation amount sensor 31 includes, for example, a brake operation sensor that detects whether or not an operator operates a brake operator and the amount of operation, and an accelerator operation sensor that detects whether or not an operator operates an accelerator operator and the amount of operation. The rotation sensor 33 detects the rotation angle of each of the rotating electric machines 11a, 11b. The acceleration sensor 35 detects the acceleration of the vehicle 1. The wheel speed sensor 37 detects the rotation speed (wheel speed) of each of the front wheels Fr and each of the rear wheels Rr (each wheel). The current sensor 39, the voltage sensor 41, and the temperature sensor 43 each detect, for example, the current, voltage, and temperature of each of the rotating electric machines 11a, 11b and a power storage device such as a battery that exchanges power between each of the rotating electric machines 11a, 11b.

[0019] The electric braking control unit 21 controls, for example, the operation of a hydraulic pressure generating unit 51 that generates hydraulic pressure for each of the brake mechanisms 15FL, 15FR, 15RL, and 15RR. The behavior control unit 23 controls friction braking by each of the brake mechanisms 15FL, 15FR, 15RL, and 15RR based on hydraulic pressure generated by the control of the electric brake control unit 21, for example, in order to suppress sudden changes in the behavior of the vehicle 1 and stabilize its posture. The behavior control unit 23 executes, for example, anti-brake lock control to prevent wheel lock during braking, traction control to prevent wheel slip (slip at each wheel) during acceleration and deceleration, and sideslip suppression control during cornering. The behavior control unit 23 obtains, for example, detection value signals output from the acceleration sensor 35 and the wheel speed sensor 37, and estimates the speed (vehicle speed) of the vehicle 1.

[0020] Each of the front motor control unit 25a and the rear motor control unit 25b includes a power conversion device connected to a power source such as a power storage device mounted on the vehicle 1. The motor control units 25a and 25b control the exchange of power between the front rotating electric machine 11a and the rear rotating electric machine 11b via a power conversion device including, for example, a plurality of switching elements. When the rotating electric machines 11a and 11b are in power running mode, the motor control units 25a and 25b sequentially commutate current to the three phases to generate rotational driving force. When the rotating electric machines 11a and 11b are in regenerative mode, the motor control units 25a and 25b convert AC power input from the three phases into DC power through switching operations of the phases synchronized with the rotation of the rotating electric machines 11a and 11b to generate rotational braking force.

[0021] FIG. 3 is a configuration diagram of the hydraulic system 50 in the vehicle control system 10 according to the embodiment. As shown in FIG. 3, the hydraulic system 50 includes, for example, a hydraulic pressure generating unit 51, a medium flow path 53, a first front valve 55a and a first rear valve 55b, a second front valve 57a and a second rear valve 57b, a reservoir tank 59, a check valve 61, and a pump 63. The hydraulic pressure generating unit 51 includes, for example, a hydraulic cylinder such as a master cylinder that generates hydraulic pressure (master pressure), and an actuator such as an electric motor that is a power source for the hydraulic cylinder. The medium flow path 53 is a flow path for a working medium (pressure medium) such as hydraulic oil that transmits power.

[0022] The first front valve 55a and the first rear valve 55b are, for example, directional control valves, etc. Each valve 55a, 55b is disposed in the medium flow path 53 between the hydraulic pressure generating unit 51 and each brake mechanism 15FL, 15FR, 15RL, 15RR. Each valve 55a, 55b, for example, switches between flowing and blocking the flow of the working medium to each brake mechanism 15FL, 15FR, 15RL, 15RR. The second front valve 57a and the second rear valve 57b are, for example, directional control valves, etc. Each valve 57a, 57b is disposed in the medium flow path 53 between the first front valve 55a and the reservoir tank 59 and between the first rear valve 55b and the reservoir tank 59. Each valve 57a, 57b switches between allowing and blocking the flow of the working medium to and from the reservoir tank 59, for example.

[0023] The reservoir tank 59 stores the working medium. The check valve 61 is disposed in the medium flow path 53 between the reservoir tank 59 and the pump 63. The check valve 61 allows the working medium to flow from the reservoir tank 59 to the pump 63 and prohibits the working medium from flowing back from the pump 63 to the reservoir tank 59. The pump 63 is disposed in the medium flow path 53 between the hydraulic pressure generating unit 51 and the first front valve 55a and the first rear valve 55b. The pump 63 delivers the working medium toward the hydraulic pressure generating unit 51.

[0024] In the hydraulic system 50, for example, when the first front valve 55a and the first rear valve 55b are open, the working medium flows in parallel to the brake mechanisms 15FL, 15FR, 15RL, and 15RR from the hydraulic pressure generating unit 51. For example, when the valves 55a and 55b are open, the pressure of the working medium acting on the front brake mechanisms 15FL and 15FR (Fr pressure) and the pressure of the working medium acting on the rear brake mechanisms 15RL and 15RR (Rr pressure) become the same according to the pressure of the working medium (master pressure) in the hydraulic pressure generating unit 51. When the same pressure is acting, the frictional braking force by the front brake mechanisms 15FL and 15FR and the frictional braking force by the rear brake mechanisms 15RL and 15RR are set in advance to have a predetermined front-to-rear ratio depending on, for example, the size and friction material of the brake mechanisms 15FL, 15FR, 15RL, and 15RR.

[0025] An example of the operation of the vehicle control system 10 according to the embodiment will be described below. 4 is a diagram showing an example of the correspondence relationship between the speed of the vehicle 1, the valve open flag, the braking force, the pressure of the hydraulic system, and the braking torque in the vehicle control system 10 of the embodiment. In the example shown in Fig. 4, the vehicle 1 is in a front-wheel drive state in which the front rotating electric machine 11a generates torque (driving torque and regenerative braking torque) on the left and right front wheels Fr. The integrated control unit 27 acquires the braking force (required braking force) of the vehicle 1 requested by the driver, for example, when the vehicle 1 decelerates after time t1, in accordance with the driver's operation of the accelerator operator and brake operator related to the deceleration of the vehicle 1.

[0026] First, for example, during the period from time t1 to time t2 when the required braking force increases in response to the driver's brake operation, the integrated control unit 27 generates a braking force equivalent to the required braking force by increasing the regenerative braking force of the front rotating electric machine 11a via the front motor control unit 25a. Next, for example, from time t2 to time t3, during a period in which the required braking force increases in response to the driver's brake operation or the like, the integrated control unit 27 increases the frictional braking force of each of the brake mechanisms 15FL, 15FR, 15RL, and 15RR by increasing the master pressure of the hydraulic system 50 via the electric braking control unit 21 and the behavior control unit 23. For example, the electric braking control unit 21 and the behavior control unit 23 open the valves 55a and 55b of the hydraulic system 50 and increase the master pressure of the hydraulic pressure generating unit 51, thereby increasing the pressure of the working medium acting on each of the brake mechanisms 15FL, 15FR, 15RL, and 15RR. For example, when each of the valves 55a and 55b is open, the pressure of the working medium acting on each of the front brake mechanisms 15FL and 15FR (Fr pressure) and the pressure of the working medium acting on each of the rear brake mechanisms 15RL and 15RR (Rr pressure) are equal to the master pressure generated by the hydraulic pressure generating unit 51. The integrated control unit 27 generates a braking force equivalent to the required braking force using the regenerative braking force of the front rotating electric machine 11a and the frictional braking force of each of the brake mechanisms 15FL, 15FR, 15RL, and 15RR.

[0027] Next, when the required braking force is constant, for example, after time t3, and no slippage of the front wheels Fr and rear wheels Rr is detected, as in the period up to time t4, the integrated control unit 27 generates a braking force equivalent to the required braking force by maintaining the regenerative braking force of the front rotating electric machine 11a and the frictional braking force of each brake mechanism 15FL, 15FR, 15RL, 15RR constant.

[0028] Next, for example, at time t4, when the behavior control unit 23 detects a slippage of the front wheels Fr due to the wheel speed of the front wheels Fr falling below a predetermined threshold corresponding to the vehicle speed, for example, due to a change in the road surface to a low-friction road, the behavior control unit 23 starts executing anti-brake lock control. The behavior control unit 23, for example, switches the valve close flag for the first front valve 55a of the hydraulic system 50 from "0," indicating an open state, to "1," indicating a closed state, thereby blocking the flow of working fluid to each of the front brake mechanisms 15FL, 15FR. With the first front valve 55a closed, the working fluid pressure acting on each of the front brake mechanisms 15FL, 15FR (Fr pressure) is at least equal to or lower than the master pressure at time t4, and, for example, changes to a constant pressure or a decreasing tendency from time t4. Meanwhile, with the first rear valve 55b maintained open, the working fluid pressure acting on each of the rear brake mechanisms 15RL, 15RR (Rr pressure) is always equal to the master pressure.

[0029] Then, for example, from time t4 to time t5, during which the front wheels Fr continue to slip, the integrated control unit 27, via the front motor control unit 25a and the electric brake control unit 21, decreases the regenerative braking force of the front rotary electric machine 11a and increases the master pressure of the hydraulic pressure generating unit 51, thereby increasing the pressure of the working fluid acting on each of the rear brake mechanisms 15RL, 15RR (Rr pressure = master pressure). The electric brake control unit 21 increases the master pressure of the hydraulic pressure generating unit 51, for example, compared to when the regenerative braking force is reduced and the frictional braking force is increased in accordance with the required braking force when there is no slippage of the wheels. For example, the electric brake control unit 21 increases the master pressure by a predetermined increase PU so as to further increase the frictional braking force in addition to an increase PS in the master pressure corresponding to the change from regenerative braking force to frictional braking force at the front wheels Fr. The Fr pressure PP shown in FIG. 4 is the amount of decrease in the Fr pressure that occurs from time t4 due to the first front valve 55a being closed, for example.

[0030] The specified increase in master pressure PU includes at least an increase in master pressure PS to compensate for the amount of increase in master pressure that does not act on the front brake mechanisms 15FL, 15FR due to the closed state of the first front valve 55a on the rear brake mechanisms 15RL, 15RR side.

[0031] The electric brake control unit 21 sets the friction braking force to a braking force (second braking force) obtained by, for example, adding a predetermined braking force to a braking force (first braking force) obtained by subtracting the regenerative braking force from the required braking force. The first braking force is, for example, the total friction braking force set when switching from regenerative braking force to friction braking force in a state where no slippage occurs in any of the wheels. The second braking force is, for example, the total friction braking force set when switching from regenerative braking force to friction braking force in a state where slippage occurs in a drive wheel (for example, the front wheel Fr in a front-wheel drive system). The predetermined braking force is a braking force corresponding to the predetermined increase PU in the master pressure described above and the lifting friction braking torque TrU described below.

[0032] When the electric braking control unit 21 switches the regenerative braking force to the frictional braking force, for example, after time t4, the electric braking control unit 21 sets the increased frictional braking torque corresponding to the decrease in the regenerative braking torque as the switched frictional braking torque TrS. For example, the electric braking control unit 21 sets the torque (the total increase in the frictional braking torque) obtained by adding the switched frictional braking torque TrS and the lifting frictional braking torque TrU corresponding to the above-described predetermined braking force as the total increased frictional braking torque TrT (= TrS + TrU). For example, the electric braking control unit 21 sets the torque obtained by multiplying the switched frictional braking torque TrS by a predetermined coefficient as the total increased frictional braking torque TrT. The predetermined coefficient is, for example, when the vehicle is front-wheel drive, the reciprocal of a predetermined rear brake coefficient k (0 < k < 1) set for each of the rear brake mechanisms 15RL and 15RR. That is, the predetermined rear brake coefficient k indicates the ratio of the switched frictional braking torque TrS in the total increased frictional braking torque TrT when the first front valve 55a is in the closed state. For example, the switched frictional braking torque TrS, the lifting frictional braking torque TrU, the total increased frictional braking torque TrT (= TrU + TrS), and the predetermined rear brake coefficient k have a correspondence relationship described by the following mathematical formula.

[0033] Total increased frictional braking torque TrT = Switched frictional braking torque TrS / k Lifting frictional braking torque TrU = Switched frictional braking torque TrS × (1 - k) / k

[0034] For example, during the period from time t4 to time t5, the switched frictional braking torque TrS is the same as the decrease in the regenerative braking torque (= Tra - Trb) from the regenerative braking torque Tra at time t4 to the regenerative braking torque Trb at time t5. The lifting frictional braking torque TrU is the same as the increase in the total braking torque (= Trd - Trc) from the total braking torque Trc (= regenerative braking torque + frictional braking torque = required braking torque) at time t4 to the total braking torque Trd (= regenerative braking torque + frictional braking torque) at time t5.

[0035] Next, for example, at time t5, when the behavior control unit 23 detects that the slippage of the front wheels Fr has been resolved by, for example, the wheel speed of the front wheels Fr exceeding a predetermined threshold value corresponding to the vehicle speed due to the cutoff of the flow of working fluid to the front brake mechanisms 15FL, 15FR and a decrease in regenerative braking force, the behavior control unit 23 stops the execution of the anti-brake lock control. The behavior control unit 23 releases the cutoff of the flow of working fluid to the front brake mechanisms 15FL, 15FR, for example, by switching the valve close flag for the first front valve 55a of the hydraulic system 50 from "1," indicating a closed state, to "0," indicating an open state. With the first front valve 55a open, the pressure of the working fluid acting on the front brake mechanisms 15FL, 15FR (Fr pressure) increases toward the master pressure. Meanwhile, with the first rear valve 55b maintained open, the pressure of the working fluid acting on the rear brake mechanisms 15RL, 15RR (Rr pressure) is equal to the master pressure.

[0036] When the first front valve 55a is switched from the closed state to the open state, the working fluid is drawn toward the front brake mechanisms 15FL, 15FR rather than toward the rear brake mechanisms 15RL, 15RR of the first rear valve 55b, which remains open, and the master pressure (=Rr pressure) temporarily decreases as the Fr pressure increases. After a suitable time has passed, the master pressure (=Rr pressure) and the Fr pressure become equal at a predetermined equilibrium pressure. As described above, the electric brake control unit 21 increases the master pressure of the hydraulic pressure generating unit 51 by a predetermined increase amount PU in advance, for example, during the period from time t4 to time t5, thereby preventing the frictional braking force from being insufficient relative to the required braking force even if the master pressure temporarily decreases, for example, after time t5.

[0037] Then, in order to prevent the frictional braking force from becoming excessive relative to the required braking force after the master pressure temporarily drops after time t5, for example, the electric brake control unit 21 gradually reduces the predetermined increase PU toward zero over a period until time t6, for example. For example, the predetermined time from time t5 to time t6 is set to at least the time required for the master pressure (=Rr pressure) and the Fr pressure to become equal to a predetermined equilibrium pressure. The electric brake control unit 21 reduces the predetermined increase amount PU of the master pressure toward zero, for example, from time t5 to time t6, so that the lifting friction braking torque TrU corresponding to the above-mentioned predetermined braking force decreases toward zero.

[0038] Next, for example, from time t6 to time t7, the integrated control unit 27 switches to frictional braking force at the front wheels Fr and rear wheels Rr until the regenerative braking force at the front wheels Fr becomes zero, and ensures the required braking force using only frictional braking force.

[0039] FIG. 5 is a diagram showing an example of the correspondence relationship between the valve open flag and the pressure of the hydraulic system 50 in the vehicle control system 10 of the embodiment and a comparative example. In the embodiment and comparative example shown in FIG. 5, for example, by executing anti-brake lock control from time t4 to time t5, the first front valve 55a of the hydraulic system 50 is closed, and then the regenerative braking force on the front wheels Fr is replaced with frictional braking force. In the embodiment, as described above, a predetermined increase in master pressure PU is set to compensate for the portion of the master pressure increase PS that does not act on the front wheels Fr after time t4, which corresponds to the change from regenerative braking force to frictional braking force. A comparative example is, for example, a case where the predetermined increase in master pressure PU is not set.

[0040] In each of the embodiments and comparative examples, when the first front valve 55a of the hydraulic system 50 is switched from a closed state to an open state due to the suspension of anti-brake lock control, for example, after time t5, the master pressure (=Rr pressure) temporarily decreases as the Fr pressure increases. In the comparative example, the master pressure of hydraulic pressure generating unit 51 is not increased in advance by a predetermined increment PU, and therefore, for example, a temporary drop in master pressure after time t5 results in a state in which the frictional braking force is insufficient relative to the required braking force. For example, a decrease in frictional braking force corresponding to the drop in master pressure PD in the comparative example makes it impossible to ensure the frictional braking force required for the required braking force (=required braking force - regenerative braking force). In contrast to this, in the embodiment, the master pressure of the hydraulic pressure generating unit 51 is increased in advance by a predetermined increment PU, so that even if the master pressure temporarily decreases, for example, after time t5, the master pressure necessary to obtain the friction braking force (=required braking force - regenerative braking force) required for the required braking force can be secured.

[0041] As described above, according to the vehicle control system 10 of the embodiment, when a slip occurs at the front wheels Fr that are subjected to regenerative braking, the behavior control unit 23 cuts off the flow of working fluid to each of the front brake mechanisms 15FL, 15FR and switches the regenerative braking torque at the front wheels Fr to friction braking torque, thereby promoting the elimination of the slip. The electric brake control unit 21 increases the pressure (master pressure) of the working fluid flowing through each of the rear brake mechanisms 15RL, 15RR compared to when a slip does not occur, thereby preventing a shortage of frictional braking force across the entire vehicle. By setting a predetermined increase in master pressure PU, the electric brake control unit 21 can prevent a shortage of braking force and destabilization of vehicle behavior when a slip occurs at the front wheels Fr.

[0042] The integrated control unit 27 can promote the elimination of the slippage of the front wheels Fr by switching from regenerative braking torque at the front wheels Fr to friction braking torque. The electric brake control unit 21 sets the increase in master pressure PS corresponding to the switching to a predetermined increase in master pressure PU, which is an increase that compensates for the portion of the master pressure increase PS that does not act on the front wheels Fr due to the closed state of the first front valve 55a, thereby preventing a shortage of braking force (the sum of friction braking force and regenerative braking force) for the entire vehicle.

[0043] The electric brake control unit 21 responds to the temporary drop in master pressure that occurs when the first front valve 55a is switched to the open state when the slippage of the front wheels Fr is resolved by using a predetermined increase in master pressure PU, thereby preventing a shortage of frictional braking force and overall braking force throughout the vehicle.

[0044] When the slippage of the front wheels Fr is resolved, the electric brake control unit 21 reduces the predetermined increase PU in the master pressure toward zero over a predetermined period of time, thereby preventing the frictional braking force of the entire vehicle from becoming excessive and preventing sudden fluctuations in the frictional braking force and destabilization of the vehicle behavior.

[0045] (Variation) Modifications of the embodiment will be described below. Note that the same parts as those in the above-described embodiment will be denoted by the same reference numerals, and descriptions thereof will be omitted or simplified. In the above-described embodiment, the vehicle 1 is in a front-wheel drive state in which the front rotary electric machine 11a generates torque (driving torque and regenerative braking torque) on the left and right front wheels Fr, as in the example shown in Fig. 4, but is not limited to this. For example, the vehicle 1 may be in a rear-wheel drive state in which the rear rotary electric machine 11b generates torque (driving torque and regenerative braking torque) on the left and right rear wheels Rr, or in an all-wheel drive state in which torque is generated on all wheels by the rotary electric machines 11a, 11b, etc.

[0046] For example, in the case of rear-wheel drive, when a slippage occurs in the rear wheel Rr, the behavior control unit 23 executes anti-brake lock control to switch the first rear valve 55b of the hydraulic system 50 from an open state to a closed state, thereby cutting off the flow of working fluid to each of the rear brake mechanisms 15RL, 15RR. Then, for example, over the period during which the slippage of the rear wheel Rr continues, the integrated control unit 27 decreases the regenerative braking force of the rear rotary electric machine 11b and increases the master pressure of the hydraulic pressure generating unit 51, thereby increasing the pressure of the working fluid acting on each of the front brake mechanisms 15FL, 15FR (Fr pressure=master pressure). For example, in the case of rear-wheel drive, the predetermined coefficient by which the shifting friction braking torque TrS is multiplied to set the total increased friction braking torque TrT is the reciprocal of a predetermined front brake coefficient h set for each front brake mechanism 15FL, 15FR. Note that the predetermined front brake coefficient h is set, for example, as h=1-k, where k is the predetermined rear brake coefficient in the embodiment. For example, when the first rear valve 55b is in a closed state, the shifting friction braking torque TrS, the lifting friction braking torque TrU, the total increased friction braking torque TrT (=TrU+TrS), and the predetermined front brake coefficient h (=1-k) have a correspondence relationship described by the following mathematical formula.

[0047] Total increased friction braking torque TrT = Repositioning friction braking torque TrS / (1-k) Lifting friction braking torque TrU = Re-holding friction braking torque TrS × k / (1-k)

[0048] In the above-described embodiment, the vehicle 1 includes the front rotating electric machine 11a connected to the left and right front wheels Fr and the rear rotating electric machine 11b connected to the left and right rear wheels Rr, but is not limited to this. For example, each wheel may be provided with an individual rotating electric machine, or an individual rotating electric machine may be provided for each appropriate combination of multiple wheels.

[0049] In the above-described embodiment, the predetermined increase amount PU in master pressure is set to an increase amount for compensating for the master pressure increase amount PS, which corresponds to switching from regenerative braking force to frictional braking force, not acting on the front wheels Fr due to the closed state of the first front valve 55a, at the rear wheels Rr. However, this is not limited to this. For example, the predetermined increase amount PU may further include an increase amount for compensating for the decrease amount PP in Fr pressure, which is decreased by the behavior control unit 23, at the rear wheels Rr. Also, for example, in the case of rear-wheel drive or all-wheel drive, the front wheels Fr and rear wheels Rr may be interpreted interchangeably.

[0050] The embodiments of the present invention are presented as examples and are not intended to limit the scope of the invention. These embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are intended to be included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0051] 1...vehicle, 10...vehicle control system, 11a...front rotating electric machine (rotating electric machine), 11b...rear rotating electric machine (rotating electric machine), 13a...front differential, 13b...rear differential, 15FL...first front brake mechanism, 15FR...second front brake mechanism, 15RL...first rear brake mechanism, 15RR...second rear brake mechanism, 17...processing device, 21...electric braking control unit (friction braking control unit), 23...behavior control unit (friction braking control unit), 25a...front motor control unit (rotating electric machine control unit), 25b...rear Motor control unit (rotating electric machine control unit), 27...integrated control unit, 31...operation amount sensor, 33...rotation sensor, 35...acceleration sensor, 37...wheel speed sensor, 39...current sensor, 41...voltage sensor, 43...temperature sensor, 50...hydraulic system (pressure system), 51...hydraulic pressure generating unit, 53...medium flow path, 55a...first front valve, 55b...first rear valve, 57a...second front valve, 57b...second rear valve, 59...reservoir tank, 61...check valve, 63...pump, Fr...front wheel, Rr...rear wheel.

Claims

1. a rotating electric machine control unit that controls the operation of a rotating electric machine that exchanges torque with a predetermined wheel; a friction braking control unit that controls the operation of a pressure system that drives friction braking mechanisms of a plurality of wheels including the predetermined wheel by a pressure medium; Equipped with The friction braking control unit is If a slip state occurs in the specified wheel when regenerative braking is being performed by the rotary electric machine control unit, the flow of the pressure medium to the friction braking mechanism of the specified wheel is blocked, and the pressure of the pressure medium to the friction braking mechanism of wheels other than the specified wheel among the plurality of wheels is increased compared to when the slip state does not occur, The pressure increase of the pressure medium is In addition to the increase in pressure of the pressure medium corresponding to the changeover of the regenerative braking force to the frictional braking force at the predetermined wheel, the pressure of the pressure medium is increased by a predetermined increase so as to increase the frictional braking force. Vehicle control system.

2. The friction braking control unit is When a slippage occurs in the predetermined wheel, the pressure of the pressure medium is increased compared to when the slippage does not occur by setting the pressure of the pressure medium in accordance with the friction braking torque obtained by multiplying the regenerative braking torque reduced by the rotating electric machine control unit by a predetermined coefficient while the flow of the pressure medium to the friction braking mechanism of the predetermined wheel is blocked. The vehicle control system of claim 1 .

3. The friction braking control unit is When the interruption of the flow of the pressure medium to the friction braking mechanism of the predetermined wheel is released, the control for increasing the pressure of the pressure medium compared to when the slip state does not occur is terminated after a predetermined time.

3. The vehicle control system according to claim 1 or 2.

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