JP3384321B2 - Braking force control device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called parallel hybrid vehicle having an engine and a motor generator, for example, or an electric vehicle having a motor generator only as a prime mover. For example, when the motor generator is regeneratively operated during braking. In addition, the present invention relates to a braking force control device that controls the braking force due to the working fluid pressure applied to the braking cylinder of each wheel.

[0002]

2. Description of the Related Art As such a braking force control device, there is, for example, the one described in JP-A-5-161210.

During braking, this braking force control device brakes the wheels by applying hydraulic pressure to a hydraulic brake as is used in general engine automobiles, and at the same time originally uses a motor generator as an electric motor as a generator. That is, the regenerative operation is performed, a part of the braking force is obtained by the regenerative torque of the motor generator, and the battery is charged with the electric power regenerated by the motor generator. Then, at the time of initial braking when the kinetic energy of the vehicle is the largest, by making the regenerative braking force of the driving wheels exceed the ideal distribution characteristic that is the ideal braking force distribution of the front and rear wheels, the energy recovery effect by the regenerative braking can be obtained. I am trying to show it.

[0004]

When the motor generator is regeneratively operated, regenerative cooperative control of the working fluid pressure is generally performed. With this regenerative cooperative control, the depression amount of the brake pedal is detected by, for example, the master cylinder pressure,
The amount obtained by subtracting the braking force by the regenerative torque of the motor generator from the braking force corresponding to the master cylinder pressure is
As a fluid pressure braking device, the working fluid pressure is mainly controlled so as to be reduced so as to be exerted by a braking cylinder provided on each wheel.

[0005] For example, "Toyota Prius Vehicle Manual"
In the braking force control device described in, as the source pressure of the working fluid pressure, using a working fluid pressure from a working fluid pressure booster different from the master cylinder, for example, called a booster,
This is controlled by a pressure control valve for increasing and decreasing pressure to a predetermined pressure.

However, although the above braking force control device can collect electric power relatively efficiently and has a high fuel consumption effect, on the other hand, there is a problem that the braking force distribution tends to be unstable. That is, the braking force of the front wheels and the braking force of the rear wheels have an ideal distribution of the braking force associated with the movement of the load, and even if the braking force distribution corresponding to this braking force distribution is set in advance, this braking force distribution is set. When the working fluid pressure to the braking cylinders of all four wheels is reduced from the power distribution state, the front wheel side to which the braking force due to the regenerative torque is applied becomes excessive braking force, for example, antilock brake control is started early. It causes problems such as being lost. This is because, for example, when the braking force due to the regenerative torque is applied only to the rear wheels, the rear wheels are in a state of excessive braking force.

Therefore, the present invention has been made by paying attention to the above-mentioned conventional problems, and suppresses the influence of the fluctuation of the braking force distribution of the front and rear wheels during the regenerative operation, and maximizes the regenerated electric power. It is an object of the present invention to provide a braking force control device capable of enhancing the fuel efficiency effect.

[0008]

In order to achieve the above object, a braking force control device according to claim 1 of the present invention is an electric device for applying an electric braking force to either the front or rear left or right wheel. Braking means, a fluid pressure braking means for applying a braking force to the wheel by the working fluid pressure to the braking cylinder of each wheel, and the electric braking means when the electrical braking force of the electric braking means is applied. Dynamic pressure control means for reducing the working fluid pressure to the braking cylinder corresponding to the dynamic braking force, and the braking force control device provided with the working fluid pressure control means,
A predetermined wheel working fluid pressure control means for reducing only working fluid pressure to a braking cylinder of a wheel to which an electric braking force of the electric braking means is applied; and a vehicle speed detecting means for detecting a vehicle speed,
When the vehicle speed detected by the vehicle speed detection means exceeds a preset vehicle speed threshold value, the working fluid pressure is reduced by only the predetermined wheel working fluid pressure control means. .

According to the first aspect of the invention, when the electric braking force is applied by the electric braking means, the working fluid pressure corresponding to the electric braking force is reduced from the working fluid pressure to the braking cylinder. The total braking force is controlled so as not to change before and after the application of the electric braking force. At this time, when the vehicle speed exceeds the vehicle speed threshold value, the working fluid pressure control means controls the working fluid pressure to the braking cylinder of the wheel to which the electric braking force is applied only by the predetermined wheel working fluid pressure control means. Control.

Here, the electric braking force of the electric braking means such as a motor generator stabilizes to a relatively small value in a region where the vehicle speed is higher than a certain level, and the electric braking force is stabilized in a medium and low speed region. Tends to be relatively large, for example, a vehicle speed threshold value is set according to the vehicle speed at which this electric braking force stabilizes at a relatively small value, and the wheel braking cylinder to which the electric braking force is applied is set. By reducing only the working fluid pressure of the vehicle by an amount equivalent to the electric braking force according to the vehicle speed threshold value, the braking force distribution between the front and rear wheels in the vehicle speed region exceeding the vehicle speed threshold value is stabilized, and possible electric power is obtained. Can be regenerated to improve fuel efficiency.

A braking force control device according to a second aspect of the present invention is
The working fluid pressure control means comprises four-wheel working fluid pressure control means for simultaneously reducing working fluid pressure to the braking cylinders of the four wheels, and when the vehicle speed detected by the vehicle speed detecting means is equal to or less than the vehicle speed threshold value. At least the four-wheel working fluid pressure control means is configured to reduce the working fluid pressure.

According to the second aspect of the present invention, when the vehicle speed is equal to or lower than the vehicle speed threshold value, the working fluid pressure is reduced by the four-wheel working fluid pressure control means. , When the electric braking force becomes relatively large and there is a possibility that the electric braking force generated by the electric braking means is large, the operation to the braking cylinders of the four wheels is performed according to this electric braking force. By simultaneously reducing the fluid pressure, it is possible to recover as much regenerative electric power as possible and improve the fuel efficiency effect.

Further, the braking force control device according to a third aspect of the present invention is characterized in that the vehicle speed threshold value is set based on an electric braking force characteristic of the electric braking means.

[0014]

According to the braking force control device of the first aspect of the present invention, when the vehicle speed exceeds the vehicle speed threshold value, the wheel to which the electric braking force of the electric braking means is applied to the braking cylinder is actuated. Since only the fluid pressure is reduced, when the vehicle speed exceeds the vehicle speed threshold value, it is possible to stabilize the distribution of the braking force of the front and rear wheels and collect the possible electric power to enhance the fuel efficiency effect.

Further, in the braking force control device according to the second aspect of the present invention, when the vehicle speed is equal to or lower than the vehicle speed threshold value, the four-wheel working fluid pressure control means applies the working fluid pressure to all the four braking cylinders. Since the pressure is reduced at the same time, it is possible to enhance the fuel efficiency by maximally recovering the electric power that can be regenerated in the vehicle speed range below the vehicle speed threshold value.

Further, in the braking force control apparatus according to the third aspect of the present invention, the vehicle speed threshold value is set based on the electric braking force characteristic of the electric braking means. The switching to the wheel working fluid pressure control means can be accurately performed, and the fuel consumption effect can be further enhanced.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an example in which the braking force control device according to the present invention is applied to a so-called FF type parallel hybrid vehicle.

EG is a gasoline engine, and this engine EG is connected to the transmission T / M via a clutch CL, and is composed of, for example, a three-phase induction motor / generator in the middle of the connection. AC type motor generator M
G is inserted. The output shaft of the transmission T / M is connected to the drive wheels (front wheels) W _FL and W _FR . Therefore, the front left and right wheels W _FL , W _FR can be driven by both the engine EG and the motor generator MG that is powered. Conversely, if the motor generator MG is regeneratively operated, the front left and right wheels W _FL , W _FR are regeneratively braked. Torque, that is, electric braking force acts, and at the same time, electric power regenerated by the motor generator MG is charged in a battery (not shown). In addition to the role of a so-called running clutch, the clutch CL stops the engine EG and the clutch CL when the torque of the engine EG is not required, for example.
Is also used to disconnect the connection between the engine EG and the drive system.

The drive wheels W _FL , W _FR and the non-drive wheels W _RL ,
Wheel cylinders 1FL to 1RR as braking cylinders are attached to W _RR , and the supply pressure to these wheel cylinders 1FL to 1RR is adjusted by a brake actuator unit 10 controlled by a brake control unit 9 described later. It is like this.

The engine EG is provided with an electronically controlled throttle valve in an intake pipe line (not shown) whose opening degree is adjusted by a rotation angle according to the number of steps using a step motor as an actuator. It is controlled by the engine control unit 37. The engine control unit 37 is configured to include a microcomputer and the like, and has a motor generator control unit 3 described later.
The engine EG is driven in response to a command signal from 8 for instructing the start and stop of the engine EG.

The motor generator control unit 38 includes a microcomputer and the like,
An accelerator operation amount signal from an accelerator operation amount sensor (not shown) provided on the accelerator pedal, an engine speed from a rotation speed sensor (not shown) provided on the engine EG,
The motor generator MG, the clutch CL, and the engine EG are controlled based on the actual gear ratio of the transmission T / M, the vehicle speed, and the like.

That is, for example, when it is determined from the accelerator pedal operation amount signal that the accelerator pedal is in the depressed state by referring to a preset traveling pattern control map or the like, the current traveling state of the vehicle is the motor generator MG.
It is determined whether it is a motor travel area in which only the engine EG is traveled, an engine travel area in which only the engine EG is traveled, or a hybrid travel area in which only the engine EG is used for normal travel and the motor generator MG is used during acceleration. The engine EG, the motor generator MG, and the clutch CL are controlled according to the determined traveling area.

When it is determined that the accelerator pedal is open, if the vehicle speed is zero, it is determined that the vehicle is stopped and the clutch CL is opened. If the vehicle speed is not zero and the antilock brake control process executed by the brake control unit 9 is not operating, the amount of power generation is detected by referring to an energy recovery amount calculation map (not shown), for example. The electric power generation amount of the motor generator MG is set based on the electric power generation amount and the vehicle speed, and the motor generator MG is operated as a generator according to the electric power generation amount to control the so-called regenerative braking state, and the electric energy thereof is stored in a battery (not shown). to recover. on the other hand,
When the antilock brake control process in the brake control unit 9 is operating, the regenerative braking of the motor generator MG is stopped based on the actual braking status information from the brake control unit 9 described later.

The transmission T / M is controlled by a transmission control unit 39. The transmission control unit 39 is configured to include a microcomputer and the like, and for example, a target gear ratio set based on a vehicle speed, an engine speed, an accelerator pedal operation amount, an input speed and an output speed of the transmission T / M. The transmission T is adjusted so that the gear ratio calculated based on
/ M gear shift control is performed, and the target gear ratio is set based on, for example, a preset gear shift pattern control map. The gear ratio increases as the vehicle speed decreases, and the gear shift increases as the accelerator pedal operation amount increases. The gear ratio is controlled so that the gear ratio increases and the gear ratio increases as the engine speed increases.

FIG. 2 shows an example of the brake actuator unit 10. The brake actuator unit 10 is a four-wheel integrated control in which the working fluid pressure to all four wheels is cut off from the master cylinder to perform pressure increase / decrease control. Actuator unit 5, an anti-lock brake control actuator unit 6 for avoiding the locking tendency of each wheel and ensuring both a braking distance and a steering effect, and only the working fluid pressure to the front wheels is mainly reduced. A front wheel control actuator unit 7 for controlling is provided.

The master cylinder 2 shown in the figure is capable of outputting an equal working fluid pressure corresponding to the amount of depression of the brake pedal 2 to two systems. Basically, the wheel cylinder of the front left wheel (hereinafter simply referred to as the front left wheel). 1FL and wheel cylinder for rear right wheel (rear right wheel cylinder) 1
The RR is connected to one system of the master cylinder 2 and has a front right wheel wheel cylinder (front right wheel cylinder) 1F.
R and a rear left wheel cylinder (rear left wheel cylinder) 1RL are connected to the other system of the master cylinder 2 to form a so-called X piping type. As is well known, the advantage of this X piping system is that even if an abnormality occurs in either one of the piping systems, the other piping system remains on the front wheel side and the rear wheel side, and on the vehicle left side and the right side. The point is that the braking force is balanced and the vehicle stability is secured. A booster 4 is interposed between the brake pedal 3 and the master cylinder 2, and details of the structure and the like will be described later.

Here, in order to facilitate understanding, the structure of each wheel cylinder 1FL to 1RR side from the structure of the antilock brake control actuator unit 6 will be described. The structure of the pressure control valve in the actuator unit 6 for controlling the anti-lock brake is similar to that of the existing conventional recirculation type. For example, one system from the master cylinder 2 is branched into two and the other system is branched. Is also branched into two, and the respective wheel cylinders 1FL to 1RR are connected to the respective branch destinations via pressure-increasing control valves 51FL to 51RR for antilock brake control. These pressure increase control valves 51FL to 51RR are normally open two-position switching solenoid valves. In addition, each of the pressure increasing control valves 51FL to 51RR is provided with each wheel cylinder 1
The check valves 52FL to 52RR that allow only the return of the working fluid from the FL to 1RR to the master cylinder 2 side are bypass-connected.

Further, on the downstream side of the pressure increasing control valves 51FL to 51RR for controlling the antilock brake, pressure reducing control valves 53FL to 53RR for controlling the antilock brake, which are normally closed two-position switching solenoid valves, are connected. Reservoirs 54P, 5 common to the output side for each system
4S and the pumps 55P and 55S are branched and connected to each other, and the damper 5
The discharge side of each pump 55P, 55S is connected to each system of the master cylinder 2 via 6P, 56S.

The antilock brake control actuator unit 6 is controlled by an ABS controller 9a which constitutes the brake control unit 9 based on a wheel speed signal from a wheel speed sensor.
That is, the relationship between each wheel speed and the vehicle body speed is monitored based on the detection signal of a wheel speed sensor (not shown), and when the slip ratio becomes equal to or more than a predetermined value and each wheel is likely to lock, the pressure increase control valve 51FL to 51RR and pressure reduction control valves 53FL to 53RR are operated to control the working fluid pressure to reduce, hold, and increase pressure to prevent wheel locking.

Further, in this embodiment, the pressure increasing control valves 51FL, 51 for controlling the front left and right wheels antilock brakes are used.
Downstream of FR and front left and right wheel cylinders 1FL, 1F
A front wheel control actuator unit 7 is interposed between the R and R. This front wheel control actuator unit 7
Is a normally open two-position switching solenoid valve interposed between the front left and right wheel anti-lock brake control pressure increasing control valves 51FL and 51FR and the front left and right wheel cylinders 1FL and 1FR. Wheel decompression control switching valves 41FL and 41FR, and check valves 42FL and 42FR bypass-connected to the front left and right wheel cylinders 1FL and 1FR to allow only recirculation to the master cylinder 2 side, and further bypass-connected to the check valves 42FL and 42FR. A proportioning valve 43 capable of substantially reducing the working fluid pressure to the front left and right wheel cylinders 1FL, 1FR.
It consists of FL and 43FR. Incidentally, the output pressure of the proportioning valves 43FL and 43FR is smaller than the input pressure on the master cylinder 2 side when it is relatively low, as shown in FIG. A pressure increasing gradient is applied little by little, and when the input pressure exceeds a predetermined value, a pressure increasing gradient that is the same as the pressure increasing gradient of the input pressure is applied. In this embodiment, the output pressure is the vehicle deceleration α [G] (Gravit) in the region where the pressure increase gradient is equal to the input pressure.
y: Working fluid pressure characteristics that generate a braking force difference equivalent to (gravitational acceleration). The α corresponds to α in the electric braking force characteristic of the motor generator MG described later.

The front wheel control actuator unit 7
Is controlled mainly by the regenerative braking controller 9b that constitutes the brake control unit 9.
That is, when the motor generator is regeneratively operated, the front left and right wheel depressurization control switching valves 41FL, 41
Close the FR to operate the proportioning valve 43F.
Front left and right wheel cylinder 1FL,
The working fluid pressure of 1FR is controlled to be lower than the supply pressure on the master cylinder 2 side. That is, the vehicle of this embodiment is of the FF type, and both the engine and the motor generator are connected only to the front wheels. Therefore, since the regenerative torque generated by the motor generator is also applied only to the front wheels, the front left and right wheel cylinders 1F corresponding to the braking force generated by the regenerative torque.
It is necessary to reduce the working fluid pressure of L, 1FR. Conversely, if the regenerative torque from the motor generator is applied only to the front wheels, the working fluid pressure of all four wheel cylinders would have been reduced. The problem becomes larger, for example, the antilock brake control is started early. Therefore, in this embodiment, the working fluid pressure of the front left and right wheel cylinders 1FL, 1FR is reduced by the proportioning valves 43FL, 43FR by the braking force due to the regenerative torque. However, the regenerative torque generated by the motor generator changes depending on, for example, the vehicle speed. In this embodiment, for example, the proportioning valve can reduce the pressure by a small amount of regenerative torque, which is relatively stable and can be generated at medium and high speeds.

Next, the booster 4 and the working fluid pressure source for the booster 4 will be described before the four-wheel integrated control actuator unit 5. In the hybrid vehicle as in the present embodiment, the engine may be stopped, so the electric pump 11 is used as the working fluid pressure source for the booster 4. The electric pump 11 draws in the working fluid in the main reservoir 8 and the check valve 1
2 and discharge. An accumulator 13 is connected to the discharge side of the electric pump 11 and further connected to the input side of the booster 4. By arranging pressure switches 14 and 15 on the upstream side and the downstream side of the accumulator 13 so that the electric pump 11 operates regardless of which of the pressure switches is lowered, the working fluid pressure in the accumulator 13 That is, the fluid pressure supplied to the booster 4 can be maintained above a predetermined value.

The basic structure of the booster 4 is the same as the existing one. That is, in the state where the brake pedal 3 is not depressed as shown in FIG. 4 (the state where the brake pedal 3 is depressed), the input shaft 71 is retracted to the right in the figure, and as a result, the steel ball 72 is Since it is pressed against the valve seat 73 by the spring 74, the working fluid pressure from the accumulator 13 taken in from the outer periphery of the piston 75 is applied to the piston 7 concerned.
5 cannot flow into the cylinder chamber 76 inside, and the force for pressing the piston 75 is not generated. The cylinder chamber 76 also communicates with the inside of the booster body 70.
A rod 77 connected to the master cylinder 2 is extended to the piston 75. In addition, reference numerals 78,
Reference numeral 79 is a return spring for retracting the piston 75 and the rod 77 to the right in the figure in a state where the brake pedal 3 is not depressed.

When the brake pedal 3 is stepped on from this state, the input shaft 71 is moved leftward in the figure against the elastic force of the spring 80 interposed between the input shaft 71 and the valve seat 73, and the tip portion thereof is moved. Moves the steel ball 72 together with the holder 82 to the left in the drawing against the elastic force of the spring 74, so that the steel ball 72 is separated from the valve seat 73. Then, the working fluid pressure from the accumulator 13 flows into the cylinder chamber 76 in the piston 75 from the gap between the input shaft 71 and the valve seat 73 through the port 81 formed in the input shaft 71. Since the piston 75 is pressed leftward in the figure together with the valve seat 73, the rod 77 is moved to the master cylinder 2 side, and the working fluid pressure in the master cylinder 2 is increased. Of course, after this, the piston 75 together with the valve seat 73 is also replaced by the input shaft 71.
May be pushed to the left, but since the piston is always pushed first by the working fluid pressure, a large propulsive force can be obtained even if the pedaling force of the brake pedal 3 is small. The working fluid pressure in 2 is boosted.

Next, when the brake pedal 3 is stopped while the brake pedal 3 is still depressed to some extent, the valve seat 73 is pressed by the elastic force of the spring 80.
And the input shaft 71 are separated from each other, and as a state, the input shaft 71 is retracted relatively to the right in the drawing with respect to the valve seat 73 (however, the input shaft 7
1 is in contact with the steel ball 72), and the steel ball 72 is pressed against the valve seat 73 again by the elastic force of the spring 74, so that the gap between the two is closed and the working fluid pressure in the cylinder chamber 76 is closed. Is enclosed, and an auxiliary force for maintaining the piston 75 and the rod 77 in the state of moving to the master cylinder 2 side is obtained by the enclosed pressure.

On the other hand, from this state, the brake pedal 3
Input shaft 7 becomes free when you release your foot from it
1 is further retracted rightward in the figure by the spring 80, and the steel ball 72 and the input shaft 71 are separated from each other while the steel ball 72 remains in contact with the valve seat 73. Then, the working fluid pressure in the cylinder chamber 75 flows through the gap between the input shaft 71 and the valve seat 73 in the flow path 83 and the input shaft guide 84 formed from the tip of the input shaft 71. It flows back to the main reservoir 8 through the passages 85 and 86 and the passage 87 formed in the booster body 70.

As described above, in the booster 4 of the present embodiment, the working fluid pressure from the accumulator 13 always flows into the cylinder chamber 76 to increase the pressure from the start of depression of the brake pedal 3. Therefore, in the present embodiment, a flow for increasing the working fluid pressure in the cylinder chamber 76 with the depression of the brake pedal 3 and taking it out as a working fluid pressure from a fluid pressure source different from the working fluid pressure of the master cylinder 2. A passage 88 was formed in the valve body 70. The working fluid pressure taken out from here is taken into the actuator unit 5 for four-wheel integrated control, which will be described later, and is used for braking force control during regeneration.

Next, the overall structure of the four-wheel integrated control actuator unit 5 will be described. First, for each system of two working fluid pressures from the master cylinder 2,
Regenerative switching valves 21P and 21S, which are two-position switching pilot valves that use the working fluid pressure extracted from the booster 4 as a pilot pressure, are interposed. The regenerative switching valve 21P, 2 consisting of this two-position switching pilot valve
The P port of 1S is connected to the output side of each system of the master cylinder 2, and its A port is branched to the antilock brake control pressure increasing control valves 51FL to 51RR, and its B port is a stroke composed of a kind of accumulator. It is connected to the simulators 22P and 22S. The regenerative switching valves 21P and 21S communicate with the P port and the A port in a normal state where there is no pilot pressure, and also check valves 20P and 20S.
Allows only reflux from B port to P port and A port. Further, in the switching state by the pilot pressure, the A port is shut off and the P port and the B port are connected. By the way, the stroke simulator 22P, 2
The 2S return spring has a spring constant equivalent to the working fluid pressure reaction force generated in the booster 4 and the master cylinder 2, and the excess working fluid is returned to the main reservoir 8. In addition, each regeneration switching valve 21
Pressure sensors 2 are provided on the upstream and downstream sides of P and 21S, respectively.
3P, 23S and pressure sensors 24P, 24S are provided.

On the other hand, the working fluid pressure extraction system of the booster 4 is provided with the regeneration switching valve 21 via a fail-safe valve 25 which is a normally closed electromagnetic two-position switching valve.
It is branched and supplied as the pilot pressure of P, 21S. In addition, this fail-safe valve 25 has a booster 4
A check valve 26 that permits only the return to the side and a bypass valve 27 that is a normally closed two-position switching pilot valve are connected in parallel by bypass, and the pilot pressure of the bypass valve 27 is the downstream pressure of the fail-safe valve 25. (Or the downstream pressure of the bypass valve 27 itself). Accordingly, when the fail-safe valve 25 is opened in principle, its downstream pressure, that is, the bypass valve 27.
Since the pilot pressure of the
When the fail-safe valve 25 is closed when the working fluid pressure from the booster 4 is low, the downstream pressure, that is, the pilot pressure of the bypass valve 27 is reduced, so that the bypass valve 27 is also closed. .

Further, the orifice 2 is provided between the fail-safe valve 25 and each regenerative switching valve 21P, 21S.
8, the regeneration switching valve 2 is provided in the orifice 28.
The check valve 29 which permits only the inflow to 1P and 21S (the pilot pressure thereof) is bypass-connected. Although one orifice 28 and one check valve 29 are provided on the upstream side of the branch in the drawing as a representative, one orifice is provided on the downstream side of the branch, that is, each regenerative switching valve 21.
You may make it interpose every P and 21S.

Further, on the downstream side of the fail-safe valve 25 or on the downstream side of the bypass valve 27, a pressure increasing control valve 30 for four-wheel integrated control, which is a normally open two-position switching solenoid valve, and a normally closed two-position valve. A four-wheel integrated control depressurization control valve 31, which is a switching solenoid valve, and a four-wheel integrated control reservoir 32 are connected in series, and the return amount of the reservoir 32 is returned to the main reservoir 8. The pressure increasing control valve 30 for the four-wheel integrated control is provided.
And the four-wheel integrated control depressurization control valve 31 are connected to the input port of the pressure control cylinder 16. The four-wheel integrated control pressure-increasing control valve 30 includes a check valve 33 that allows only the recirculation from the pressure control cylinder 16.
And a relief valve 34 that relieves the upstream side working fluid pressure of the pressure increase control valve 30 at a predetermined pressure or more are connected in parallel by bypass. Further, a check valve 35 that allows only the return from the four-wheel overall control reservoir 32 is bypass-connected to the four-wheel overall control depressurization control valve 31. Further, a pressure sensor 36 for detecting the input working fluid pressure of the pressure control cylinder 16 may be attached if necessary.

The pressure control cylinder 16 has cylinder portions 18P and 18S having pistons 17P and 17S, which have the same shape, that is, at least the pressure receiving area on the input side and the pressure receiving area on the output side are the same, and face each other in one cylinder body. And each cylinder portion 18P, 18S
The output ports of are connected to the respective systems from the master cylinder 2 on the downstream side of the regeneration switching valves 21P and 21S. Of course, each cylinder part 18P, 18S
The return springs 19P and 19S are also of the same specifications including the spring constant. That is,
Two cylinder parts 18 are provided for the input working fluid pressure.
The same working fluid pressure can be output from P and 18S to each of the two systems from the master cylinder 2. Further, the so-called pressure receiving area ratio between the pressure receiving area on the input side and the pressure receiving area on the output side of each of the pistons 17P and 17S is the master cylinder 2
The ratio of the output pressure to the working fluid pressure taken out of the booster 4 is substantially equal to the ratio.

The four-wheel integrated control actuator unit 5 is mainly composed of the brake control unit 9.
Is controlled by the above-described regenerative braking controller 9b. That is, when no abnormality is detected as the braking force control device, the fail safe valve 2
When 5 is opened and the brake pedal 3 is depressed with the antilock brake control not being performed, the working fluid pressure taken out from the booster 4 is increased.
The bypass valve 27 whose pilot pressure is the downstream pressure of the fail-safe valve 25 is also switched and opened. Further, the downstream pressure of the fail-safe valve 25 passes through a check valve 29 and the regeneration switching valves 21P, 21P.
Since the pilot pressure is also supplied to S, the regenerative switching valves 21P and 21S are switched, and the downstream side, that is, the wheel cylinders 1FL to 1RR side is shut off, and each system of the master cylinder 2 has the stroke simulator 22P. , 22S. Therefore, the working fluid pressure of each system of the master cylinder 2 operates the pistons in the stroke simulators 22P and 22S, but its return spring generates a reaction force equivalent to the reaction force in the master cylinder 2 and the booster 4, The driver does not feel uncomfortable when depressing the brake pedal 3.

On the other hand, since the regenerative torque by the motor generator can be obtained from the vehicle speed, the gear ratio, etc. as described above, the braking force of the front left and right wheels is calculated in advance, and the pressure sensor 23P on the master cylinder side is calculated. , 23S
The braking force when the working fluid pressure is supplied to each of the wheel cylinders 1FL to 1RR is calculated from the working fluid pressure detected in 1., and the braking force composed of the difference value between the two and the wheel cylinder side pressure sensors 24P, 24S. The output pressure from the pressure control cylinder 16 is controlled so that the braking force corresponding to the detected working fluid pressure matches. Here, since the pressure control cylinder 16 can supply the same working fluid pressure to the two X piped systems, in order to control the pressure increase / decrease in the same manner, the pressure control cylinder 16 must be controlled. It suffices to control the input pressure to the pressure increase / decrease. At this time,
The ratio between the output pressure and the input pressure of the pressure control cylinder 16 is determined by the pistons 17P, 1 of the two cylinder portions 18P, 18S.
Since it is the inverse ratio of the pressure receiving area ratio of 7S, the required working fluid pressure, that is, the amount of increase or decrease in the input pressure with respect to the amount of increase or decrease in the output pressure is set. Then, the four-wheel integrated control pressure-increasing control valve 30 and the four-wheel integrated control pressure-decreasing valve 31 may be controlled to open and close according to the amount of increase or decrease of the input pressure. In addition,
The working fluid pressure reduced by the four-wheel integrated control decompression valve 31 is basically stored in the four-wheel integrated control reservoir 32.

Further, for example, when the regeneration switching valve is of a solenoid drive type, an electrical structure for driving the solenoid is required, and if the regeneration operation time due to the depression of the brake pedal 3 becomes longer as described above. ,
For example, there is a problem that the excitation time of the solenoid becomes long and the amount of heat generation becomes large, and the energy loss becomes large. However, in the present embodiment, in order to drive the regeneration switching valves 21P and 21S, the brake pedal Three
Since the working fluid pressure in the booster 4 that constantly occurs during stepping on is used as the pilot pressure, the structure is simplified and an excessive amount of heat generation and energy loss can be suppressed and prevented.

Further, even when the brake pedal 3 is depressed during the regenerative operation and the working fluid pressure taken out from the booster 4 is reduced by slightly returning the brake pedal 3, the regeneration switching valve 21P. , 2
Since the pilot pressure to 1S is reduced only slowly through the orifice 28, the regenerative switching valve 21
It is possible to prevent the P and 21S from accidentally returning to the normal position and to continue the regenerative cooperative control. On the other hand, when the brake pedal 3 is stepped on, the working fluid pressure taken out from the booster 4 flows from the check valve 29 side as the pilot pressure of the regeneration switching valves 21P, 21 without passing through the orifice 28, so that the necessary responsiveness is secured. can do.

Further, when the brake pedal 3 is released from this state, the working fluid pressure taken out from the booster 4 is also reduced as described above, so that the regeneration switching valve 2
The pilot pressure of 1P, 21S is also slowly reduced through the orifice 28, and the regeneration switching valves 21P, 2S
1S returns to the normal position, and the master cylinder 2 is again connected to the wheel cylinders 1FL to 1RR side. Also,
The working fluid in the four-wheel integrated control reservoir 32 passes through the check valve 35, and together with the working fluid in the pressure control cylinder 16, the check valve 33 and the check valve 2.
Return to booster 4 through 6.

Incidentally, when the antilock brake control is to be started while the brake pedal 3 is being depressed, the regenerative operation is stopped, and the regenerative coordinated control of the braking force is also stopped.

If an abnormality is detected without the brake pedal 3 being depressed, the fail safe valve 2 is detected.
When the valve 5 is closed, the bypass valve 27 is also kept closed even when the brake pedal 3 is next stepped on, so that the working fluid pressure in the booster 4 is not supplied to the downstream side thereof and the regenerative switching valve 21P. , 21S is the master cylinder 2
And the wheel cylinders 1FL to 1RR are maintained in a communicating state, and a fail-safe function is obtained.

On the other hand, if an abnormality is detected while the brake pedal 3 is being depressed, the fail-safe valve 25 is immediately closed as described above. However, at this time, even if the fail-safe valve 25 is closed, the downstream pressure of the fail-safe valve 25, that is, the working fluid pressure on the booster 4 side of the check valve 26 is high, so the pilot pressure of the regeneration switching valves 21P and 21S is sealed. Therefore, the regenerative switching valve 21P,
21S remains blocked from the working fluid system from the master cylinder 2. However, at this time, the pilot pressure of the enclosed regenerative switching valves 21P and 21S, that is, the downstream pressure of the fail-safe valve 25 acts as the pilot pressure of the bypass valve 27, so that the bypass valve 27 is maintained in the open state. Therefore, as a similar fail-safe measure, the pressure increasing control valve 30 for controlling four wheels is integrated.
Is maintained in the open state and the four-wheel integrated decompression control valve 31 is maintained in the closed state. Therefore, the working fluid pressure taken out from the booster 4 continues to be supplied to the two systems through the pressure control cylinder 16, so at least the brake is applied. The braking by the working fluid pressure can be maintained until the foot is released from the pedal 3. Since the pressure receiving area ratio of the pistons 17P, 17S of the two cylinder parts 18P, 18S of the pressure control cylinder 16 is set to the ratio of the output pressure of the master cylinder 2 and the working fluid pressure taken out from the booster 4, The working fluid pressure from the pressure control cylinder 16 obtained from time to time becomes the same as that from the master cylinder 2, stabilizing the braking force and causing no discomfort.

Besides this, the piston 1 of the two cylinder portions 18P and 18S of the pressure control cylinder 16 is also provided.
By setting the pressure receiving area ratio of 7P, 17S to the ratio of the output pressure of the master cylinder 2 and the working fluid pressure taken out from the booster 4, the working fluid pressure from the pressure control cylinder 16 becomes equal to that from the master cylinder 2. Therefore, the control mode on the downstream side of the antilock brake control actuator unit can be shared with that for the working fluid pressure from the master cylinder 2 to facilitate control.

The brake control unit 9 is
The slip state of the wheel is detected to control the antilock brake control actuator unit 6, and the working fluid pressure to the wheel cylinders 1FL to 1RR is adjusted so that the slip rate of the wheel matches the reference slip rate. The ABS controller 9a, and the four-wheel integrated control actuator unit 5 and the front-wheel control actuator unit 7 depending on the operating conditions of the ABS controller 9a and the motor generator controller 38.
Is controlled to adjust the working fluid pressure to the wheel cylinders 1FL to 1RR, so-called regenerative braking control 9b. Then, these ABS controller 9a and regenerative braking controller 9
Each of b is configured to include a microcomputer or the like, and the engine control unit 37, the motor generator controller 38, and the transmission control unit 39 perform control while performing mutual communication.

The ABS controller 9a controls the working fluid pressure to the wheel cylinders 1FL to 1RR as described above, and the slip ratio of any of the wheels becomes a predetermined value or more, and the corresponding wheel cylinders 1FL to 1R.
When the pressure reducing control for reducing the working fluid pressure to R is started, the ABS operation flag F _ABS is set to F _ABS = 1 and is output to the motor generator control unit 38 and the regenerative braking controller 9b.

The regenerative braking controller 9b reduces the working fluid pressure equivalent to the electric braking force generated when the motor generator MG is driven as a generator, so as to reduce the front wheel control actuator unit 7 and the front wheel control actuator unit 7 according to the vehicle speed. One of the four-wheel integrated control actuator units 5 is drive-controlled. That is, the electric braking force applied to the vehicle by operating the motor generator MG as a power generator is offset by the braking force decrease caused by reducing the working fluid pressure to the wheel cylinders 1FL to 1RR, and the electric braking force is reduced. The total braking force is not increased before and after applying the braking force.

Further, the regenerative braking controller 9b inputs the ABS operation flag F _ABS from the ABS controller 9a, the ABS operation flag is F _ABS = 1 and the pressure reduction control of the working fluid pressure by the antilock brake control processing is started. When it is detected, the four-wheel integrated control actuator unit 5 and the front-wheel control actuator unit 7 stop the regenerative cooperative pressure reduction for reducing the working fluid pressure to each of the wheel cylinders 1FL to 1RR.

FIG. 5 is a flow chart showing an example of the regenerative cooperative pressure reducing process in the regenerative braking controller 9b. This process is a process executed when the motor generator MG is regeneratively operated, and is executed, for example, in a predetermined cycle set in advance.

First, in step S1, it is determined whether or not braking is started depending on whether or not the brake switch control signal is in the ON state. If it is determined that braking is started, the process proceeds to step S2, and if not, the process proceeds to step S3. To do.

In step S2, it is determined whether or not the regenerative cooperative pressure reduction can be performed based on whether or not the antilock brake control flag F _ABS is set to "1". If the lock brake control process is not performed, the process proceeds to step S4a, and if not, the process proceeds to step S3.

In step S4a, the wheels (not shown)
Vehicle speed V based on the value detected by the speed sensor _SPDetected, then
The process proceeds to step S4b, and the vehicle speed V_SPIs the vehicle speed threshold V
_AIs greater than. And the vehicle speed V_SPBut
V_SP> V_AIf so, the process proceeds to step S5, and V_SP
> V_AIf not, the process proceeds to step S6.

In step S5, the regenerative coordinated pressure reduction is performed only by the front wheel control actuator unit 7, and then the process ends. That is, the control signal for closing the front wheel control switching valves 41FL and 41FR is output. At this time, when the regenerative coordinated pressure reduction is being performed by the four-wheel integrated control actuator unit 5, that is, for example, when the regenerative coordinated pressure reduction by the four-wheel overall control actuator unit 5 is started in advance, the flag set When it is detected that the regenerative coordinated depressurization is being performed by the four-wheel integrated control actuator unit 5 by referring to the four-wheel integrated control, the four-wheel integrated control pressure increase control valve 3 is detected.
A control signal for opening 0 and closing the four-wheel integrated control depressurization control valve 31 is output to stop the regenerative cooperative depressurization by the four-wheel integrated control actuator unit 5.

On the other hand, in step S6, the regenerative coordinated pressure reduction is performed only by the four-wheel integrated control actuator unit 5, and then the process ends. That is, the electric braking force BF _REG that can be generated by the motor generator MG is calculated from the vehicle speed V _SP and the state of charge SOC of the battery (not shown) by searching the control map of FIG. 6, for example.
For example, the electric braking force BF _REG, and the like multiplied by a predetermined proportionality factor, four-wheel overall pressure reduction amount ΔP that corresponds to the BF _{RE G}
Calculate _REG-TTL . And the four-wheel integrated reduced pressure amount ΔP
_It outputs a control signal to the pressure increasing control valve 30 and the pressure reducing control valve 31 for four-wheel integrated control for achieving _REG-TTL . At this time, the front wheel control actuator unit 7
When the regenerative coordinated pressure reduction is being performed by, for example, when it is detected that the regenerative coordinated pressure reduction set in advance when the front wheel control actuator unit 7 starts the regenerative coordinated pressure reduction is performed. A control signal for opening the front wheel control switching valves 41FL and 41FR is output to stop the regenerative coordinated pressure reduction by the front wheel control actuator unit 7.

Next, for example, the electric braking force BF _REG calculated in step S6 by searching the control map of FIG. 6 or the like.
The calculation principle of will be described. The motor generator of the present embodiment has a characteristic that the electric braking force BF _REG changes according to the vehicle speed V _SP , as shown in FIG. 6, for example. That is, at a vehicle speed of about zero, the electric braking force BF _REG has a negative value in order to generate a so-called creep torque, that is, the driving force is applied, and the vehicle speed V _SP is increased from that point. with the electrical braking force BF _{RE G} increases in the area of positive value to. However, the increasing slope gradually decreases in the low speed region of the vehicle speed V _SP , and the vehicle deceleration β
Limiter is applied to a considerable extent. Further, when the vehicle speed V _SP is accelerated, it turned electrical braking force BF _REG is decreasing, the vehicle deceleration over the high-speed range from the middle-speed range of about vehicle speed V _A alpha (alpha
<Β) Asymptotically stable and stable. Also, the regenerative braking force BF _{REG that} can be generated depending on the battery state of charge SOC
Changes, for example, when the battery state of charge SOC is high (the battery is sufficiently charged), the motor generator MG cannot generate power, that is, the limiter acts, so that the regenerative braking force BF _REG also decreases. However, in the hybrid vehicle as in the present embodiment, since the battery is set to run with battery power as much as possible, the battery is rarely always fully charged. Therefore, the battery charge state SOC is the regenerative braking force BF _REG. It is used to correct

In FIG. 6, the electric braking force BF
_The vehicle speed V _{A at} which _REG gradually _{approaches the} vehicle deceleration α corresponds to the vehicle speed threshold V _A. Next, the operation of the above embodiment will be described based on the control map of FIG.

Now, when the driver depresses the brake pedal 3 and the motor generator MG is regenerated by the motor generator control unit 38 in the running vehicle, the calculation process of FIG. 5 is started accordingly. Then, when the brake switch control signal is ON and the antilock brake control flag _FABS is reset, that is, when the brake pedal is depressed and the antilock brake control is not started, the calculation process of FIG. 5 is performed. Step S1 and step S
After 2, the process proceeds to step S4a. And the vehicle speed V _SP
Is detected, and then at step S4b, the vehicle speed V _SP at this time is detected.
Is greater than the vehicle speed threshold V _A , step S
5, the regenerative coordinated pressure reduction is performed only by the front wheel control actuator unit 7. That is, the switching valves 41FL, 41FR for controlling the front wheels are controlled to be in the closed state, and the proportioning valves 43FL, 43F are accordingly controlled.
The R reduces the working fluid pressure to the front left and right wheel cylinders 1FL and 1FR.

At this time, as shown in FIG. 6, when the vehicle speed V _SP is higher than the vehicle speed threshold value V _A , the electric braking force characteristic of the motor generator MG with respect to the vehicle speed gradually approaches the vehicle deceleration rate α. Stabilize. On the other hand, the working fluid pressure characteristics of the proportioning valve 43FL, 43FR are
As shown in FIG. 3, the working fluid pressure characteristic is such that a braking force difference corresponding to about α [G] is generated at the vehicle deceleration, so the vehicle deceleration α [G By applying a pressure reduction corresponding to this while applying an electric braking force BF _REG of a certain degree, the total braking force to the front wheels can be held constant, and therefore the braking force distribution of the front and rear wheels at this time is It does not change before and after regenerating the motor generator MG.

When the foot is released from the brake pedal 3 or the anti-lock brake control is started in this state, the process proceeds from step S1 or step S2 to step S3, and the front wheel control switching valves 41FL and 41FR.
Control the open state. As a result, the front left and right wheel cylinders 1FL, 1FR are communicated with the antilock brake control actuator unit 6, and the pressure reduction control up to that point is completed. Of course, in such a case, the regenerative operation of the motor generator is also released, so the total braking force applied to the front wheels does not fluctuate except for the amount of change due to the antilock brake control.

When the vehicle speed V _SP becomes equal to or lower than the vehicle speed threshold value V _{A in a} state where the brake pedal 3 is continuously depressed to decelerate and the anti-lock brake control is not started, the calculation processing of FIG.
6 and the actuator unit for four-wheel integrated control 5
The regenerative coordinated depressurization is performed only by That is, since the regenerative coordinated pressure reduction is being performed by the front wheel control actuator unit 7, the front wheel control switching valves 41FL, 41F.
Control R to open. As a result, the front left and right wheel cylinders 1FL and 1FR are communicated with the antilock brake control actuator unit 6, and the regenerative coordinated pressure reduction by the front wheel control actuator unit 7 ends.
Further, as described above, the electric braking force BF _REG that can be generated by the motor generator MG is calculated, the four-wheel integrated reduced pressure amount ΔP _REG-TTL corresponding to the electric braking force BF _REG is calculated, and the four-wheel integrated A control signal is output to the pressure increasing control valve 30 and the pressure reducing control valve 31 for four-wheel integrated control according to the pressure reducing amount ΔP _REG-TTL .

Here, the electric braking force characteristic of the motor generator MG with respect to the vehicle speed is as shown in FIG.
_{When SP} is equal to or lower than the vehicle speed threshold V _A , the electric braking force becomes larger than the electric braking force corresponding to the vehicle deceleration α. On the other hand, proportioning valve 43FL, 43F
The working fluid pressure characteristics of R, as shown in FIG. 3, because they become a working fluid pressure characteristics so as to generate the braking force difference corresponding to the degree α [G] in vehicle deceleration, the vehicle speed V _SP is the vehicle speed When the value is equal to or less than the threshold value V _{A, although} the pressure reduction equivalent to the electric braking force BF _REG cannot be performed only by the front wheel control actuator unit 7, the four-wheel integrated control actuator unit 5 performs the regenerative coordinated pressure reduction. Braking force B
It is possible to sufficiently reduce the pressure equivalent to F _REG .

When the brake pedal 3 is released or the anti-lock brake control is started in this state, the process proceeds from step S1 or step S2 to step S3, and the pressure increasing control valve 30 for four-wheel integrated control is opened. Status,
The decompression control valve 31 is controlled to the closed state. As a result, the regenerative cooperative pressure reduction by the four-wheel integrated control actuator unit 5 is completed.

Therefore, as described above, the electric braking force BF by the motor generator MG is generated in any vehicle speed range.
_Since it is possible to reduce the pressure corresponding to _REG , it is possible to reliably regenerate regenerated electric power and enhance the fuel efficiency effect.

Here, when the working fluid pressure to the four wheels is simultaneously regeneratively and cooperatively reduced by the four-wheel integrated control actuator unit 5 against the electric braking force from the motor generator MG, the braking force distribution on the front wheel side is distributed. If it becomes too large, the braking force tends to be excessive, and the antilock brake control process operates early. Particularly during high-speed traveling, the deceleration of the vehicle may be reduced as a result of the antilock brake control process being activated early. However, when the vehicle speed V _SP is higher than the vehicle speed threshold value V _{A, since the} regenerative coordinated pressure reduction is performed only by the front wheel control actuator unit 7, the braking force distribution does not change before and after the regenerative operation of the motor generator MG. . Therefore, when the vehicle speed V _SP is higher than the vehicle speed threshold value V _A, it is possible to prevent the antilock brake control process from operating early.

On the other hand, when the vehicle speed V _SP is equal to or lower than the vehicle speed threshold value V _A , the four-wheel integrated control actuator unit 5 performs the regenerative coordinated pressure reduction, so that the antilock brake control process may operate early. Since the vehicle speed _SP is simultaneously subjected to the regenerative coordinated pressure reduction for the four wheels from the low speed region to the medium speed region where the vehicle speed threshold is equal to or lower than the vehicle speed threshold V _A , the vehicle travels even if the antilock brake control process is activated early. There is no problem because the stability is within the range.

Further, in the above embodiment, the vehicle speed threshold value V _A is set according to the electric braking force characteristic of the motor generator MG with respect to the vehicle speed.
Regenerative coordinated pressure reduction by the front wheel control actuator unit 7 and the four-wheel integrated control actuator unit 5 can be appropriately switched according to the change in the electric braking force accompanying the change in the vehicle speed, and the electric power by the regenerative operation can be more effective. Can be collected.

The vehicle speed threshold value V _A is obtained by previously obtaining the change in the electric braking force with respect to the change in the vehicle speed by an experiment or the like to obtain the electric braking force characteristic of the motor generator MG, and is set accordingly. Good. Further, as the vehicle speed threshold value V _A , for example, a vehicle speed that can ensure traveling stability of the vehicle when the four-wheel integrated control actuator unit 5 performs regenerative cooperative decompression for the four wheels is set. You may

Further, in the above-mentioned embodiment, the case where the antilock brake control actuator unit is provided is described, but this may be set as necessary. Further, in the above embodiment, the motor generator M
In the case where the power generation amount of G is set by the motor generator control unit 38 and the pressure reduction amount by the regenerative coordinated pressure reduction corresponding to the electric braking force by the motor generator MG is set by the regenerative braking controller 9b and set independently of each other. As described above, for example, the amount of power generation corresponding to the amount of pressure reduction set by the regenerative braking controller 9b may be notified to the motor generator control unit 38, and the motor generator MG may be regeneratively operated in accordance with this, or conversely, The power generation amount of the motor generator MG may be notified to the regenerative braking controller 9b, and the pressure reduction amount may be set accordingly.

In the above embodiment, the case where the vehicle speed V _SP is equal to or lower than the vehicle speed threshold value V _{A and the} cooperative regenerative pressure reduction is performed only by the four-wheel integrated control actuator unit 5 has been described. Regenerative coordinated pressure reduction may be performed by the overall control actuator unit 5 and the front wheel control actuator unit 7.

Here, in the above embodiment, the motor generator MG and the motor generator control unit 38 correspond to the electric braking means, the wheel cylinders 1FL to 1RR correspond to the fluid pressure braking means, and the four-wheel integrated control actuator. The unit 5 and the front wheel control actuator unit 7 correspond to the working fluid pressure control means,
The front wheel control actuator unit 7 corresponds to the predetermined wheel working fluid pressure control means, the four-wheel integrated control actuator unit 5 corresponds to the four-wheel working fluid pressure control means, and the processing of step S4a in FIG. 5 serves as the vehicle speed detection means. It corresponds.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a hybrid vehicle to which a braking force control device of the present invention is applied.

FIG. 2 is a fluid pressure circuit diagram showing an example of a brake actuator unit shown in FIG.

FIG. 3 is a characteristic explanatory view of the proportion valve of FIG.

FIG. 4 is an explanatory diagram of the booster of FIG.

FIG. 5 is a flowchart showing an example of a processing procedure of regenerative cooperative pressure reduction processing in the regenerative braking controller.

FIG. 6 is a control map showing an electric braking force characteristic of motor generator MG.

[Explanation of symbols]

EG engine CL clutch MG motor generator T / M transmission W _{FL to} W _RR wheel 1 _{FL to 1 RR} wheel cylinder 3 brake pedal 4 booster 5 four-wheel integrated control actuator unit 6 anti-lock brake control actuator unit 7 front wheel control actuator Unit 9 Brake control unit 9a ABS controller 9b Regenerative braking controller 10 Brake actuator unit 30 Four wheel integrated control pressure increase control valve 31 Four wheel integrated control pressure reduction control valve 37 Engine control unit 38 Motor generator control unit 39 Transmission control unit 41FL , 41FR switching valve for front left and right wheel decompression control

Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B60K 6/02-6/06 B60T ⁷ /12-7/22 B60T 8/00 B60T 8/32-8/96 B60L 1 / 00-3/12 B60L 7/00-13/00 B60L 15/00-15/42

Claims (3)

(57) [Claims] 1. An electric braking means for applying an electric braking force to one of the front and rear left and right wheels, and a fluid for applying a braking force to the wheel by a working fluid pressure applied to a braking cylinder of each wheel. Pressure braking means, and working fluid pressure control means for reducing the working fluid pressure to the braking cylinder corresponding to the electric braking force when the electric braking force of the electric braking means is applied. In the braking force control device, the working fluid pressure control means is a predetermined wheel working fluid pressure control means for reducing only the working fluid pressure to the braking cylinder of the wheel to which the electric braking force of the electric braking means is applied. A vehicle speed detecting means for detecting a vehicle speed, and when the vehicle speed detected by the vehicle speed detecting means exceeds a preset vehicle speed threshold value, the working fluid pressure is reduced only by the predetermined wheel working fluid pressure control means. like Braking force control device, characterized in that it Tsu. 2. The working fluid pressure control means includes four-wheel working fluid pressure control means for simultaneously reducing working fluid pressure to the braking cylinders of the four wheels, and the vehicle speed detected by the vehicle speed detecting means is the vehicle speed. 2. The braking force control device according to claim 1, wherein at least the four-wheel working fluid pressure control means reduces the working fluid pressure when the threshold value is not more than the threshold value. 3. The braking force control device according to claim 1, wherein the vehicle speed threshold value is set based on an electric braking force characteristic of the electric braking means.