JPH11170990A - Braking device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a braking device for vehicles capable of arbitrarily regulating the braking force, recovering the kinematic energy in decelerating a vehicle and utilizing the energy to the braking action and the accelerating action, and easily realizing an anti-lock brake system, etc. SOLUTION: When the braking force is generated by operating a hydraulic pump motor 9 mounted on a vehicle as a pump, the discharge pressure of the hydraulic pump motor 9 is arbitrarily regulated by first and second hydraulic control valves 15, 18 and a relief valve 16, the discharge pressure of the hydraulic pump motor 9 is accumulated in an accumulator 11, the kinematic energy during the braking is recovered in the accumulator 11, and the recovered energy in the accumulator 11 is supplied to the hydraulic pump motor 9 or a hydraulic brake unit 7 by first to third hydraulic control valves 15, 18, 17 and the relief valve 16 and re-utilized in the braking and accelerating action.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering kinetic energy lost when a vehicle is decelerated and for performing subsequent braking operation and starting / starting.
The present invention relates to a vehicular braking device which can improve the energy efficiency of a vehicle by effectively utilizing the acceleration operation, and is also suitable for making the braking function intelligent.

[0002]

2. Description of the Related Art In recent years, brake systems for vehicles have been actively provided with intelligent brake functions such as an anti-lock brake system and a traction control system. In order to cope with such an intelligent system, an electric brake system is being promoted.

[0003] As for the electrification of the brake device, a method of electrifying a friction material driving mechanism itself for pressing a friction material such as a brake pad against a rotating body such as a brake disc, and a method of hydraulically pressing the friction material against the rotating body are used. The method can be roughly classified into a method of electrically driving a pressure generating device as a generation source, and various types have been developed and proposed.

[0004]

However, in the conventional electric brake device, in any case, during braking, electric energy is supplied from a battery mounted on the vehicle to the friction material driving mechanism or the driving portion of the pressure generating device. There is a problem that the electric energy of the brake device increases the consumption of electric energy in the vehicle, and the onboard battery needs to have higher performance.

[0005] In addition, the conventional brake device generally includes:
When the vehicle decelerates, all kinetic energy is converted into heat and discarded, which has been a factor in reducing the energy efficiency of the vehicle. Therefore, a braking energy regenerating device that improves the energy efficiency of a vehicle by recovering the kinetic energy lost when the vehicle decelerates as hydraulic energy and using the recovered hydraulic energy as drive energy when the vehicle starts / accelerates is also proposed. (See Japanese Patent No. 2503818).

However, the braking energy regenerating device disclosed in the above-mentioned Japanese Patent Publication No. 2503818 is used in combination with an air brake device, and controls two systems, a pneumatic control system and a hydraulic control system for the regenerative device. There was a problem that a system was required and the configuration became complicated. Also, since the braking energy regenerating device is provided between the propeller shaft of the vehicle and the transmission, energy recovery during braking and reuse of the recovered energy cannot be performed independently for each wheel. There is a problem that it cannot be effectively used for an antilock brake system, a traction control system, and the like, which require individually controlling the braking torque or the driving torque of each wheel.

The present invention has been made in view of the above circumstances, and not only can adjust the braking force arbitrarily, but also recovers kinetic energy when the vehicle decelerates and uses the recovered energy for braking operation and starting / acceleration operation. To improve the energy efficiency of the vehicle and to recover and reuse the recovered energy independently for each wheel, so that brake functions such as an anti-lock brake system and a traction control system can be used. An object of the present invention is to provide a vehicular braking device capable of easily realizing intelligentization and suppressing an increase in consumption of electric energy in a vehicle due to electrification of a braking device.

[0008]

A vehicle braking device according to the present invention for achieving the above object comprises a braking energy regenerating unit mounted on wheels, and a control device for controlling the braking energy regenerating unit. The braking energy regenerating unit is a hydraulic brake unit that brakes the wheels by hydraulic pressure, and a hydraulic motor that is connected to a wheel shaft, operates as a hydraulic pump with the rotational force of the wheels, and rotationally drives the wheel shafts by supplying hydraulic pressure. An operating hydraulic pump motor, an accumulator for accumulating hydraulic pressure, a reservoir for storing hydraulic oil, and connecting the accumulator to a discharge port of the hydraulic pump motor when operating the hydraulic pump motor as a hydraulic pump, and connecting the reservoir with the hydraulic pump motor. A first pump connected to a suction port of the hydraulic pump motor;
When the hydraulic pump motor is operated as a hydraulic motor, the accumulator is connected to the suction port of the hydraulic pump motor and the reservoir is connected to the discharge port of the hydraulic pump motor. A first hydraulic switching valve forming an oil passage connection state of No. 2 and an oil passage between the discharge port of the hydraulic pump motor and the accumulator, and changing a check pressure by a control signal from the control device. A possible relief valve, a second hydraulic switching valve that opens and closes an oil passage between the relief valve and the accumulator, and supplies the hydraulic pressure stored in the accumulator to the hydraulic brake unit or returns the hydraulic pressure to the reservoir A third hydraulic switching valve, wherein the control device controls the first to third hydraulic switching valves and the relief valve to perform predetermined braking. Or a driving force, characterized in that the action on the wheel.

According to the above configuration, during braking,
The hydraulic pump motor is operated as a hydraulic pump.
At this time, the check pressure of the relief valve is controlled according to the required braking force, and at the same time, when the check pressure of the relief valve is lower than the hydraulic pressure stored in the accumulator, the accumulated pressure of the accumulator is changed to the discharge port of the hydraulic pump motor. Actuate the second hydraulic switching valve so as not to act on
When the check pressure of the relief valve is higher than the hydraulic pressure stored in the accumulator, the second hydraulic switching valve is operated such that the hydraulic pressure output from the hydraulic pump motor is stored in the accumulator. This way,
The drive torque for rotating the hydraulic pump acts as a load on the wheels and serves as a braking force for reducing the rotation of the wheels. The driving torque for rotating the hydraulic pump is determined by the pump discharge pressure. In the above configuration, the accumulator can be separated from the discharge port of the hydraulic pump motor by the second hydraulic switching valve. An inconvenient situation in which the pump discharge pressure is determined can be avoided. Further, by adjusting the check pressure by the relief valve, the discharge pressure of the hydraulic pump motor can be adjusted to an arbitrary value.

If the check pressure of the relief valve is lower than the hydraulic pressure stored in the accumulator, the hydraulic pressure exceeding the check pressure is released to the reservoir, but the check pressure of the relief valve is lower than the hydraulic pressure stored in the accumulator. When the pressure is high, the hydraulic pressure output from the hydraulic pump motor is accumulated in the accumulator by the second hydraulic switching valve, and a part of the kinetic energy during deceleration (the amount not consumed as heat) is supplied to the accumulator as hydraulic pressure. Collected.

When the braking force by the accumulated pressure is insufficient for the required braking force, the hydraulic brake unit is operated by the hydraulic pressure accumulated in the accumulator to compensate for the braking force. The hydraulic switching valve 3 is operated. This makes it possible to obtain a sufficient braking force.

When the vehicle starts and accelerates, the hydraulic pressure accumulated in the accumulator is supplied to the hydraulic pump motor, and the hydraulic pump motor operates as a hydraulic motor to transmit driving force to wheels. The second hydraulic switching valve is controlled. By performing the operation control in this manner, the energy recovered at the time of deceleration of the vehicle can be effectively used for the braking operation and the start / acceleration operation, so that the energy efficiency of the vehicle can be improved.

When the accumulator is operated to accumulate pressure or when the hydraulic pump motor is operated as a hydraulic motor, the maximum check pressure of the relief valve is set to be equal to or less than the maximum allowable pressure of the components of the device and the oil passage. This can prevent damage to hydraulic equipment and oil passages due to overload.

In the vehicle braking device according to the present invention, the braking energy regenerating unit mounted on the wheel includes:
With a configuration in which a hydraulic brake unit is combined, it is possible to equip each wheel. Therefore, the braking energy regenerating unit is provided for each wheel, and the control device performs the first to third braking according to the rotation of the wheel or the state of the vehicle.
If it is configured to control the hydraulic switching valve and the relief valve of
Energy recovery and reuse of the recovered energy can be performed independently for each wheel.

Further, in the case of the vehicle brake system of the present invention, the hydraulic brake unit of the braking means is operated by the hydraulic pressure accumulated in the accumulator when the vehicle decelerates, and an electric motor or the like which consumes a large amount of electric energy is used. The electric energy is only used for controlling the operation of the first to third hydraulic switching valves and the relief valve.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a vehicular braking system according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.
As shown in FIG. 1, the vehicle braking device 10 according to the first embodiment includes a braking energy regeneration unit 3 provided for each wheel of the vehicle, and a control device (not shown) that controls the braking energy regeneration unit 3. Consists of The control device is installed at an appropriate position away from wheels on a vehicle body on which a power device such as an engine is mounted.

As shown in the figure, the braking energy regenerating unit 3 is connected to a wheel shaft 21 by a hydraulic brake unit 7 for braking the wheels by hydraulic pressure, and operates as a hydraulic pump by the rotational force of the wheels. A hydraulic pump motor 9 operating as a hydraulic motor that rotationally drives the wheel shaft 21, an accumulator 11 for accumulating hydraulic pressure,
A reservoir 13 for storing hydraulic oil, first to third hydraulic switching valves 15, 18 and 17, and a relief valve 16 are provided.

When operating the hydraulic pump motor 9 as a hydraulic pump, the first hydraulic switching valve 15 sets the valve position to the position A, and connects the accumulator 11 to the first port (discharge port) of the hydraulic pump motor 9. Exit)
9a, the reservoir 13 is connected to a second port (suction port) 9b of the hydraulic pump motor 9 to form a first oil passage connection state (the state shown in FIG. 1).
When the hydraulic pump motor 9 is operated as a hydraulic motor, the valve position is set to the position B, the accumulator 11 is connected to the suction port 9b, and the reservoir 13 is connected to the discharge port 9a. A road connection state is formed.

The relief valve 16 has a structure in which the check pressure can be changed by a control signal from the control device, and is provided in an oil passage 14 between the discharge port 9a of the hydraulic pump motor 9 and the accumulator 11. I have. The check pressure is changed by adjusting the amount of deflection of the valve spring 16a by an appropriate linear motion device 16b using a stepping motor or a solenoid.

The second hydraulic switching valve 18 controls opening and closing of the oil passage 14 between the relief valve 16 and the accumulator 11. The third hydraulic switching valve 17
Supplies the hydraulic pressure accumulated in the accumulator 11 to the hydraulic brake unit 7, holds the hydraulic pressure supplied to the hydraulic brake unit 7, or returns the hydraulic pressure of the hydraulic brake unit 7 to the reservoir 13.

The hydraulic brake unit 7 brakes a pair of friction members 71 and 72 disposed so as to sandwich a brake disk 22 that rotates integrally with wheels by a hydraulic piston 75 housed and held in a cylinder portion 74 of a caliper 73. This is a hydraulic disc brake that generates a braking force by pressing against the disc 22. The hydraulic pressure accumulated in the accumulator 11 is supplied to the cylinder portion 74 of the caliper 73 via the third hydraulic pressure switching valve 17.

The control unit receives various signals such as a steering angle, a brake pedal depression force, a wheel speed, a yaw rate, etc. from various sensors and switches (not shown) mounted on the vehicle to detect a rotation state of each wheel and a running state of the vehicle. Then, based on the various signals obtained, by independently controlling the braking energy regeneration units 3 provided for each wheel, in order to optimize the braking torque and the driving torque given to each wheel,
The first to third hydraulic switching valves 15, 18, 17 of each braking energy regenerating unit 3 and the direct acting device 16 b of the relief valve 16 are controlled.

More specifically, the control device sets the valve position of the first hydraulic switching valve 15 to position A when the vehicle is decelerated (during braking), and sets the hydraulic pump motor 9
Is operated as a hydraulic pump. At this time, the linear motion device 16b is controlled so that the check pressure of the relief valve 16 according to the required braking force based on the brake pedal depression force signal is obtained. That is, by controlling the check pressure of the relief valve 16 so that the discharge pressure of the hydraulic pump motor 9 is proportional to the required braking force, a braking force based on a pressure accumulation proportional to the brake pedal depression force can be obtained. The relief valve 16
If the check pressure is lower than the hydraulic pressure stored in the accumulator 11, the relief valve 16 and the second hydraulic switching valve 18 are connected so that the stored pressure in the accumulator 11 does not act on the discharge port 9a of the hydraulic pump motor 9. Oil path 14 between
The valve is closed by the second hydraulic pressure switching valve 18 in which the valve position is set to the position A. Also, relief valve 1
When the check pressure of No. 6 is higher than the hydraulic pressure stored in the accumulator 11, the hydraulic pressure output from the hydraulic pump motor 9 is stored in the accumulator 11 so that
The relief valve 16 and the second hydraulic switching valve 18 are controlled by the second hydraulic switching valve 18 in which the valve position is set to the position B.
Is opened.

When the required braking force is insufficient with the accumulated braking force, the control unit operates the hydraulic brake unit 7 with the hydraulic pressure accumulated in the accumulator 11 to control the braking force. In order to supplement the power, the valve position of the third hydraulic switching valve 17 is switched to position C, and the third hydraulic switching valve 17 is operated. Further, the control device sets the valve position of the third hydraulic switching valve 17 to position B when the braking force of the hydraulic brake unit 7 is maintained. When the brake of the vehicle is released, the control device controls the first
The valve positions of the hydraulic switching valve 15, the second hydraulic switching valve 18, and the third hydraulic switching valve 17 are set to the positions shown in the drawing. That is, the valve position of the first hydraulic switching valve 15 is set to position A, the valve position of the second hydraulic switching valve 18 is set to position A, and the hydraulic oil output from the pump motor 9 is set. At the same time, the valve position of the third hydraulic switching valve 17 is set to the position A, the check pressure of the relief valve 16 is set to the minimum value (substantially zero), and the hydraulic pressure supplied to the hydraulic brake unit 7 is set. Is returned to the reservoir 13 to reduce the pressure.

At the time of start / acceleration, the control device switches the valve position of the second hydraulic switching valve 18 to the position B and sets the valve position of the first hydraulic switching valve 15 to the position B. The accumulator 11
The hydraulic pressure accumulated in the suction pump 9 of the hydraulic pump motor 9
b, and the hydraulic pump motor 9 operates as a hydraulic motor to transmit driving force to the wheels.

Further, at the time of accumulating the pressure in the accumulator 11 or operating the hydraulic pump motor 9 as the hydraulic motor at the maximum output, the maximum check pressure of the relief valve 16 is used for the components of the device and the oil passage. Set the pressure below the maximum allowable pressure to prevent damage to hydraulic equipment and oil passages due to overload.

According to the vehicle braking device 10 of the present embodiment, when the vehicle is braked, the driving torque for rotating the hydraulic pump acts as a load on the wheels to provide a braking force for reducing the rotation of the wheels. . The driving torque for rotating the hydraulic pump is determined by the pump discharge pressure.
Since the accumulator 11 can be disconnected from the discharge port 9a of the hydraulic pump motor 9 by the hydraulic pressure switching valve 18, the inconvenience in which the pump discharge pressure is determined by the accumulated pressure of the accumulator 11 can be avoided. Further, by increasing or decreasing the check pressure of the relief valve 16, the discharge pressure of the hydraulic pump motor 9 can be adjusted to an arbitrary value.

That is, the pump discharge pressure at the time of braking is arbitrarily set irrespective of the accumulated pressure of the accumulator 11 by adjusting the check pressure in the relief valve 16 and opening and closing the oil passage 14 by the second hydraulic switching valve 18. Therefore, even when gentle braking is required, it is possible to prevent a Gack'n effect or the like caused by the high pressure of the accumulator 11 acting as a pump load, and perform good braking.

When the check pressure by the relief valve 16 is lower than the hydraulic pressure stored in the accumulator 11, the hydraulic pressure exceeding the check pressure is released to the reservoir 13, but the check pressure of the relief valve 16 is reduced by the accumulator 1.
When the hydraulic pressure is higher than the hydraulic pressure stored in the hydraulic pump 1, the hydraulic pressure output from the hydraulic pump motor 9 is stored in the accumulator 11 by the second hydraulic switching valve 18, and a part of the kinetic energy during deceleration (as heat) The unconsumed amount) is collected by the accumulator 11 as hydraulic pressure. Then, for the required braking force, the accumulator 11
If the braking force due to the pressure accumulation in
Since the braking force is supplemented by operating the hydraulic brake unit 7 with the hydraulic pressure accumulated in the accumulator 11, a necessary and sufficient braking force can be obtained.

At the time of start / acceleration, the hydraulic pump motor 9 operates as a hydraulic motor to transmit driving force to wheels, so that energy recovered at the time of deceleration of the vehicle is effectively used for braking operation and start / acceleration operation. Therefore, the energy efficiency of the vehicle can be improved.

Then, the vehicle braking device 10 of the present embodiment
In the above, the braking energy regenerating unit 3 is provided for each wheel, and the control device can control the braking energy regenerating units 3 independently of each other, so that energy recovery and reuse of the recovered energy can be performed independently for each wheel. Therefore, it is easy to realize intelligent brake functions such as an anti-lock brake system and a traction control system. That is, when the skid of the wheel is detected during the braking by the accumulated pressure, the linear force device 16b is controlled to reduce the check pressure of the relief valve 16, thereby reducing the braking force. By setting the valve position of the third hydraulic pressure switching valve 17 to the position A, the braking force is reduced and the wheel skid can be eliminated. Also, start /
When the slip of the driving wheel is detected during acceleration, each of the valves 15, 1
6, 17, and 18 to apply a braking force to the drive wheels,
The slip can be suppressed.

In this embodiment, the hydraulic brake unit 7 of the braking means is operated by the hydraulic pressure accumulated in the accumulator 11 when the vehicle decelerates, and uses an electric motor or the like which consumes a large amount of electric energy. No
The electric energy is supplied to the first to third hydraulic switching valves 15, 18,
Since only the amount used for controlling the operation of the relief valve 17 and the relief valve 16 is sufficient, it is also possible to suppress an increase in consumption of electric energy in the vehicle due to the electric control of the brake device. The above description of the operation of the first hydraulic switching valve 15 in each of the valve positions A and B is for when the vehicle is moving forward, and when the vehicle is moving backward, the position B is used for accumulating braking, and the position A is used for assisting the driving force. Becomes

FIG. 2 shows a second embodiment of the vehicular braking apparatus according to the present invention. In the vehicle braking device 25 of the second embodiment, the pump shaft of the hydraulic pump motor 9 in the braking energy regeneration unit 3 of the first embodiment is detachably connected to the wheel shaft 21 via the clutch means 24. Since the configuration other than the point that the clutch means 24 is added is the same as that of the first embodiment, the description is omitted. The clutch means 24 may have a configuration in which the operation can be controlled by a control device (not shown).
For example, a known clutch device such as an electromagnetic clutch can be used. As described above, in the configuration in which the wheel shaft 21 and the pump shaft of the hydraulic pump motor 9 are connected via the clutch means 24, the wheel shaft 21 and the pump shaft are separated from each other by the clutch means 24 when braking is not performed. In addition, it is possible to reliably prevent an extra load from acting on the wheel shaft 21.

[0034]

According to the vehicle brake system of the present invention, the hydraulic pump motor is operated as a hydraulic pump during braking. At this time, the check pressure of the relief valve is controlled according to the required braking force, and at the same time, when the check pressure of the relief valve is lower than the hydraulic pressure stored in the accumulator, the accumulated pressure of the accumulator is changed to the discharge port of the hydraulic pump motor. The second hydraulic switching valve is operated so as not to act on the accumulator, and when the check pressure of the relief valve is higher than the hydraulic pressure stored in the accumulator, the hydraulic pressure output by the hydraulic pump motor is stored in the accumulator. Then, the second hydraulic switching valve is operated.

In this case, the drive torque for rotating the hydraulic pump acts as a load on the wheels, and becomes a braking force for reducing the rotation of the wheels. The drive torque for rotating the hydraulic pump is determined by the pump discharge pressure,
In the above configuration, since the accumulator can be separated from the discharge port of the hydraulic pump motor by the second hydraulic pressure switching valve, an inconvenience in which the pump discharge pressure is determined by the accumulated pressure of the accumulator can be avoided. Further, by adjusting the check pressure by the relief valve, the discharge pressure of the hydraulic pump motor can be adjusted to an arbitrary value. Therefore, the pump discharge pressure can be set arbitrarily irrespective of the accumulated pressure of the accumulator, and it is possible to perform good braking without causing a Gack'n effect or the like.

If the check pressure of the relief valve is lower than the hydraulic pressure stored in the accumulator, the hydraulic pressure exceeding the check pressure is released to the reservoir, but the check pressure of the relief valve is lower than the hydraulic pressure stored in the accumulator. When it is high, the hydraulic pressure output from the hydraulic pump motor is accumulated in the accumulator by the second hydraulic switching valve, and a part of the kinetic energy during deceleration (the amount not consumed as heat) is applied to the accumulator. As a result.

If the required braking force is not sufficient with the braking force by the accumulated pressure, the hydraulic brake unit is operated by the hydraulic pressure accumulated in the accumulator to compensate for the braking force. The hydraulic switching valve 3 is operated. This makes it possible to obtain a sufficient braking force.

When the vehicle is started / accelerated, the hydraulic pressure accumulated in the accumulator is supplied to the hydraulic pump motor, and the hydraulic pump motor operates as a hydraulic motor to transmit driving force to wheels. The second hydraulic switching valve and the relief valve are controlled. By performing the operation control in this manner, the energy recovered at the time of deceleration of the vehicle can be effectively used for the braking operation and the start / acceleration operation, so that the energy efficiency of the vehicle can be improved.

Further, at the time of accumulating the pressure in the accumulator or operating the hydraulic pump motor as a hydraulic motor, the check pressure of the relief valve is set to be equal to or less than the maximum allowable pressure of the components of the device or the oil passage. Thereby, it is possible to prevent the hydraulic equipment and the oil passage from being damaged due to the overload.

In the vehicle braking device according to the present invention, the braking energy regenerating unit mounted on the wheels includes:
With a configuration in which a hydraulic brake unit is combined, it is possible to equip each wheel. Therefore, the braking energy regenerating unit is provided for each wheel, and the control device performs the first to third braking according to the rotation of the wheel or the state of the vehicle.
If it is configured to control the hydraulic switching valve and the relief valve of
Since the energy can be recovered and the recovered energy can be reused independently for each wheel, it is easy to realize intelligent brake functions such as an anti-lock brake system and a traction control system.

In the case of the vehicular braking apparatus of the present invention, the hydraulic brake unit of the braking means is operated by the hydraulic pressure accumulated in the accumulator when the vehicle decelerates, and an electric motor or the like which consumes a large amount of electric energy is used. Since the electric energy is only used for controlling the operation of the first to third hydraulic switching valves and the relief valve, the electric control of the brake device may increase the electric energy consumption in the vehicle. It can also be suppressed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of a vehicular braking device according to the present invention.

FIG. 2 is a block diagram showing a configuration of a second embodiment of the vehicular braking device according to the present invention.

[Explanation of symbols]

 Reference Signs List 3 braking energy regeneration unit 7 hydraulic brake unit 9 hydraulic pump motor 10 vehicular braking device 11 accumulator 13 reservoir 15 first hydraulic switching valve 16 relief valve 17 third hydraulic switching valve 18 second hydraulic switching valve 21 wheel shaft 22 Brake disc 75 Hydraulic piston

Claims (3)

[Claims] 1. A braking energy regenerating unit mounted on a wheel, and a control device for controlling the braking energy regenerating unit, the braking energy regenerating unit comprising: a hydraulic brake unit for braking the wheel by hydraulic pressure; A hydraulic pump motor that is connected to a shaft, operates as a hydraulic pump with the rotational force of the wheels, and operates as a hydraulic motor that rotationally drives the wheel shaft by supplying hydraulic pressure, an accumulator for accumulating hydraulic pressure, and a reservoir for storing hydraulic oil When operating the hydraulic pump motor as a hydraulic pump, the accumulator is connected to a first port of the hydraulic pump motor and the reservoir is connected to a second port of the hydraulic pump motor.
A first oil path connection state connected to a port is formed, and when the hydraulic pump motor is operated as a hydraulic motor, the accumulator is connected to a second port of the hydraulic pump motor and the reservoir is connected to the hydraulic pump motor. A first hydraulic switching valve for establishing a second oil passage connection state connected to the first port of the hydraulic pump motor;
A relief valve provided in an oil passage between a port and the accumulator and capable of changing a check pressure by a control signal from the control device; and a second valve for opening and closing an oil passage between the relief valve and the accumulator. A hydraulic switching valve,
A third hydraulic switching valve that supplies the hydraulic pressure accumulated in the accumulator to the hydraulic brake unit or returns the hydraulic pressure to the reservoir, wherein the control device includes the first to third hydraulic switching valves and the relief valve And a predetermined braking force or driving force is applied to the wheels by controlling the braking force. 2. During braking, the hydraulic pump motor is operated as a hydraulic pump, the discharge pressure of the pump is adjusted by changing the check pressure of the relief valve, and the hydraulic pump motor is appropriately controlled by the second hydraulic switching valve. A braking force is generated by accumulating the output hydraulic pressure in the accumulator, and when the braking force by the accumulated pressure is insufficient for the required braking force, the braking force is accumulated by the accumulator. 2. The vehicle braking device according to claim 1, wherein the control device operates to operate the third hydraulic switching valve to operate a hydraulic brake unit to supplement a braking force. 3. The vehicle according to claim 1, wherein the first and second hydraulic pump motors are configured to supply a hydraulic pressure accumulated in the accumulator to the hydraulic pump motor during acceleration and transmit the driving force to wheels by operating as a hydraulic motor. The vehicle braking device according to claim 1, wherein the hydraulic switching valve is controlled.