JPH06191385A - Brake fluid pressure control device - Google Patents

Abstract

(57) [Abstract] [Purpose] A hydraulic control valve that generates a brake operating pressure by using a pressure corresponding to the brake operating force as a pilot pressure and reduces the brake operating pressure by increasing the control force that acts in a direction opposing the pilot pressure. Eliminates the discomfort that the brake operating pressure is generated in the case of a failure in which the control force is lost even when the brake is not operated in the provided device. [Structure] The circuit 24 is operated when the brake is operated by the pedal 23 or when the traction control in which the valve 55 is turned on is performed.
The valve 56 is opened by the pressure inside or the chamber 40, and the original pressure is supplied to the valve port 35 of the valve 26. The valve 26 uses this as a pressure source to generate the pressure Pc according to the pressure inside the circuit 24 or the chamber 40. This is reduced by increasing the electromagnetic force Fso.
The valve 56 is closed to keep the pressure Pc at 0 during the brake non-operation when the pressure in the circuit 24 or the chamber 40 is less than the minute set value. Therefore, even when the electromagnetic force Fso disappears, the pressure Pc can be maintained at 0 when the brake is not operated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brake fluid pressure control device which is used for controlling a brake fluid pressure for rotationally braking a wheel of a vehicle so as not to cause a brake lock of the wheel.

[0002]

2. Description of the Related Art As a conventional brake fluid pressure control device, there is a brake fluid pressure control device as shown diagrammatically in FIG. 5 disclosed in Japanese Patent Laid-Open No. 4-87867.

That is, the master cylinder hydraulic pressure Pm from the master cylinder 2 corresponding to the pedaling force of the brake pedal 1 is received as a pilot pressure in one direction (pressure increasing direction), and the spring force Fspi of the spring 3 is further received in the same direction. The electromagnetic force Fso of the solenoid 4 and the spring force Fspd of the spring 5 are received in the other direction (pressure reduction direction), and the balance of these forces causes the hydraulic pressure from the pump 6 to be the original pressure to brake the wheel 7 to the wheel cylinder 8. It has a stepped spool type hydraulic control valve 9 for determining the hydraulic pressure Pw.

From the balance formula of the forces acting on the hydraulic pressure control valve 9, the brake hydraulic pressure Pw is expressed as follows: where the master cylinder hydraulic pressure receiving area is Am and the brake hydraulic pressure receiving area is Aw.
It is expressed by the following equation.

## EQU00001 ## Pw = (Am / Aw) Pm + (Fspi-Fspd-Fso) / Aw (1)

As is clear from this equation, in this type of brake fluid pressure control device, the brake fluid pressure Pw is controlled with respect to the master cylinder fluid pressure Pm as shown in FIG. Then, normally, the current I to the solenoid 4 is set to a reference current Ib at which Fso = Fspi-Fspd is achieved so that the second term on the right side of the equation (1) becomes 0, and thereby the a characteristic is generated. In this case, the brake hydraulic pressure Pw becomes a value obtained by multiplying the master cylinder hydraulic pressure Pm by (Am / Aw), and the boost ratio A
m / Aw can be arbitrarily determined.

When the solenoid current I is made larger than the reference current Ib, the electromagnetic force Fso corresponding to the increase amount ΔI is obtained.
The brake fluid pressure Pw is controlled according to the b characteristic that is decreased from the a characteristic by a corresponding value due to the increase of the, and conversely, when the solenoid current I is made smaller than the reference current Ib, the electromagnetic force Fso corresponding to the reduction amount is reduced. Due to the decrease, the brake fluid pressure P
w is controlled along the c characteristic which is increased by a corresponding value from the a characteristic.

The solenoid current I is determined by the controller 10. For this purpose, a signal from a wheel speed sensor 11 for detecting the peripheral speed of the wheels 7 is input to the controller 10. The controller 10 calculates the vehicle speed based on the input wheel speed, and obtains the wheel slip ratio from this vehicle speed and the wheel speed. When this slip ratio exceeds the set value near the ideal slip ratio that provides the maximum road surface friction coefficient,
A brake fluid pressure reduction amount ΔP1 (see, eg, FIG. 6) necessary for slip prevention is calculated, and in order to achieve this pressure reduction, the solenoid current I is increased by ΔI, and the brake fluid pressure Pw is reduced to zero. As a result, the slip of the wheels can be avoided.

Although not shown, the controller 10
Can perform yaw rate feedback control of the vehicle as follows. That is, the controller 10 first calculates the yaw rate target value that the vehicle should originally generate from the steering wheel steering angle detected by the steering angle sensor and the vehicle speed detected by the vehicle speed sensor, and the actual yaw rate of the vehicle detected by the yaw rate sensor is calculated as the target. Find the difference between the left and right wheel braking forces to match the value. Then, in order to cause this difference in braking force, one of the left and right wheels has a brake fluid pressure P.
The w can be reduced by increasing the solenoid current I, or the other brake fluid pressure Pw can be increased by decreasing the solenoid current I, so that the yaw rate of the vehicle during braking can be made equal to the target value.

[0009]

However, while the conventional brake fluid pressure control device has such an excellent control function, normally the electromagnetic force Fso of the solenoid 4 causes the fluid pressure control valve 9 to reduce the brake fluid pressure. Brake fluid pressure P
Since the electromagnetic force Fso is reduced when it is desired to increase w, the following problems occur when the control system of the solenoid 4 fails to generate the electromagnetic force Fso due to a failure such as disconnection.

That is, the solenoid electromagnetic force Fso is caused by the failure.
The brake fluid pressure control characteristic when the brake pressure is not generated is as shown by c in FIG. 6, and the brake fluid pressure ΔPw is generated even when the brake pedal 1 is not depressed and the master cylinder fluid pressure Pm is 0. . In addition, at the time of the above failure, the brake fluid pressure Pw is generated against the intention of the driver, and the wheels are braked.

The present invention improves the brake fluid pressure control device of the above-mentioned type so that the brake is never actuated if the driver does not operate the brake at the time of such a failure, and thus the above-mentioned problem is solved. The purpose is to eliminate it.

[0012]

For this purpose, the first aspect of the present invention uses the pressure corresponding to the brake operating force corresponding to the brake operating force as the pilot pressure, and the pressure from the pressure source as the source pressure to create the brake operating pressure. In a brake fluid pressure control device having a fluid pressure control valve capable of reducing the brake working pressure by increasing a control force acting in a direction opposite to the pilot pressure, a source pressure input circuit of the fluid pressure control valve or a brake operation. A shutoff valve that is closed when the pressure corresponding to the brake operating force is less than a set value is inserted in the pressure output circuit.

For the same purpose, the second aspect of the present invention uses the pressure from the pressure source as the source pressure to actuate the brake operating pressure by the stroke of the spool that receives the brake operating force-corresponding pressure in one direction as the pilot pressure in accordance with the brake operating force. In the brake fluid pressure control device having a fluid pressure control valve capable of reducing the brake working pressure by receiving a control force in a direction opposite to the pilot pressure and making the stroke of the spool, When the corresponding pressure is less than the set value, resistance means for preventing the stroke of the spool due to the disappearance of the control force is provided.

[0014]

In the first aspect of the present invention, the pressure corresponding to the brake operation force generated by the brake operation via the brake pedal or the automatic brake operation for traction control is used as the pilot pressure, and the pressure from the pressure source is used as the base pressure. A hydraulic control valve creates a brake operating pressure, and the hydraulic control valve further controls the brake operating pressure to decrease by increasing a control force acting in a direction opposite to the pilot pressure.

By the way, the shutoff valve inserted in the source pressure input circuit or the brake operating pressure output circuit of the hydraulic pressure control valve is closed when the brake operating force corresponding pressure is less than the set value.
Therefore, even if the control force disappears due to a failure, the shutoff valve should prevent the hydraulic control valve from outputting the brake operating pressure as long as the brake operating force corresponding pressure is less than the set value and the brake is not operated. Therefore, it is possible to solve the problem that the brake operating pressure is suddenly generated due to the failure even though the brake is not being operated.

According to the second aspect of the present invention, the hydraulic control valve is adapted to receive the brake operation force corresponding pressure generated by the brake operation via the brake pedal or the like or the automatic brake operation for traction control as the pilot pressure in one direction and make a stroke. The spool creates a brake operating pressure based on the pressure from the pressure source. Further, the spool strokes by receiving a control force acting in a direction opposite to the pilot pressure, so that the brake operating pressure is controlled to be reduced by increasing the control force.

By the way, the resistance means prevents the stroke of the spool due to the disappearance of the control force during non-operation of the brake when the pressure corresponding to the brake operation force is less than the set value. Therefore,
Even if the control force disappears due to a failure while the brake operating pressure corresponding pressure is below the set value and the brake is not operating, as long as the brake operating force corresponding pressure is below the set value and the brake is not operating, the resistance means Since the spool of the control valve is held at the stroke position when the brake is not operated, the problem that the brake working pressure is suddenly generated due to the failure can be solved even when the brake is not operated.

[0018]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows an embodiment of the brake fluid pressure control device of the present invention. In this figure, only the brake fluid pressure control system relating to one wheel is shown, but the same brake fluid pressure control is applied to the other three wheels of the vehicle. Of course, the system exists.

Reference numeral 21 is a master cylinder, 22 is a wheel cylinder, and the master cylinder 21 is a brake pedal 2
The master cylinder hydraulic pressure Pm, which is the brake operating force corresponding pressure corresponding to the operating force (brake pedal depressing force), is output to the circuit 24 in association with the brake operation by depressing No. 3, and the wheel cylinder 22 uses the brake hydraulic pressure Pw. It is actuated to generate a braking force corresponding to the hydraulic pressure on the corresponding wheel.

The brake fluid pressure Pw is determined by the fail-safe valve 2
5 is normally opened and closed to open the circuit 27 from the hydraulic pressure control valve 26.
Output pressure Pc to the master cylinder hydraulic pressure P of the circuit 24 at the time of failure in which the output pressure Pc is substantially the same as the output pressure Pc.
It shall be the same as m. Here, a hydraulic synthesizer 28 is inserted in the circuit 27, and this hydraulic synthesizer is operated by the hydraulic control valve 2
In response to the output pressure Pc of No. 6, the brake fluid pressure Pw, which is almost the same as this, is supplied to the wheel cylinder 22.

The hydraulic pressure control valve 26 includes a spool 32 slidably fitted in a valve housing 31, and both end faces of the spool are exposed to the drain chambers 33 and 34, respectively. Spool 32
In the figure, the land 32a on the left side in the drawing is a stepped spool having a smaller diameter than the land 32b on the right side, and the pressure receiving area difference Aw is set between both lands. The left land 32a and the housing groove 31a define the input valve opening 35, and the right land 32b and the housing groove 31b define the drain valve opening 3
Define 6.

A spring 37 in the chamber 33 is made to act on the small-diameter end surface of the spool 32, and a plunger 38a of a solenoid 38 is made to abut. The solenoid 38 has a supply current I
The electromagnetic force (control force) Fso proportional to is generated and is applied to the spool 32 via the plunger 38a.

On the other hand, the pin 3 is provided on the large-diameter end surface of the spool 32.
9 is slidably fitted to define a pilot chamber 40, and a cap 41 for receiving the protruding end of the pin 39 is attached to the spool 32.
Abutting the large diameter end face of. A spring 42 is further applied to the large-diameter end surface of the spool 32, and one end of the push rod 43 is brought into contact with the end surface of the cap 41 that is far from the large-diameter end surface of the spool 32. The other end of the push rod 43 faces the pilot chamber 45 via the bellows 44.

As shown in the drawing, the housing grooves 31a and 31b respectively have drain valve ports 36 when the input valve port 35 is closed.
Are already open, and these groove grooves 31a,
31b is arranged between the valve housing 31 and the output port 31
form c. The valve housing 31 further includes a spool 3
A communication port 31d that is always in communication with the second chamber 40 is formed.

In the hydraulic pressure control valve 26 having the above-mentioned structure, the groove 31a is connected to a pressure source circuit 54 including a pump 51, a check valve 52 for preventing backflow and an accumulator 53, that is, a source pressure input circuit. , The output port 31c is connected to the circuit 27,
In other words, connect to the brake operating pressure output circuit, connect port 3
1d is connected to the traction control valve 55, and the pilot chamber 45 is connected to the master cylinder hydraulic circuit 24 for practical use. Here, when the traction control valve 55 is OFF, the communication port 31d is drained from the communication port 31d, that is, the chamber 40 is in a non-pressure state, and when the traction control valve 55 is ON, the pressure of the pressure source in the circuit 54 is supplied to the chamber 40. To do.

In this embodiment, in particular, a shutoff valve 56 is inserted in the source pressure input circuit 54 of the hydraulic pressure control valve 26, and this shutoff valve is closed in the state, and the master cylinder hydraulic pressure Pm in the circuit 24 is When operating the brake to exceed the minimum setting value Pms,
Alternatively, it is assumed that the circuit 54 is opened when the traction control valve 55 supplies the pressure of the pressure source to the chamber 40 so that the pressure in the chamber becomes the fine set value Pms or more and the automatic brake operation for traction control is performed. Note that the shutoff valve 56 is a poppet valve, which is advantageous in preventing leakage of the pressure source pressure when the shutoff valve 56 is closed. And the shutoff valve 56
And the hydraulic pressure control valve 26, the pressure in the circuit 54 is supplied to the fail-safe valve 25 as a pilot pressure.

The controller 61 determines the amount of electricity I supplied to the solenoid 38 and the ON / OFF state of the traction control valve 54. For this control, the controller 61 has a brake switch which is closed in response to depression of the brake pedal 23. A signal from 62, a signal from a longitudinal G sensor 63 that detects the longitudinal acceleration of the vehicle body, and a signal from a wheel speed sensor 64 that detects the rotational peripheral speed of the corresponding wheel are input.

The operation of the above embodiment will be described below. The controller 61 executes a control program (not shown) based on the above-mentioned input information to perform the brake hydraulic pressure control which will be described below. Since neither control is related to the present invention, detailed description will be omitted here.

That is, the controller 61 first checks whether the brake switch 62 is ON for braking or OFF for non-braking. Furthermore, the wheel speed detected by the sensor 64,
The wheel slip ratio is calculated based on the vehicle speed that can be obtained from the vehicle longitudinal acceleration detected by the sensor 63, and whether or not this is equal to or greater than a set value near the ideal slip ratio that provides the maximum road surface friction coefficient prevents the wheel from locking. Check whether it is in the anti-skid control area where the brake fluid pressure should be controlled for. If the vehicle is not braking or is not in the anti-skid control range even during braking, the solenoid current I is set to the reference current Ib.
(See FIG. 6) During braking and in the anti-skid control range, a predetermined anti-skid control is performed by adjusting the solenoid current I as described later.

(1) Non-operating state In the state where the brake pedal 23 is not depressed and the master cylinder hydraulic pressure Pm is not generated, the hydraulic pressure control valve 26 is, of course, in the pilot chamber 45, the master cylinder hydraulic pressure as the pilot pressure. Without inputting Pm, the spring force Fspi of the spring 42 acts on the spool 32 leftward in the figure, and the spring force Fspd of the spring 37 and the solenoid 3 rightward in the figure.
The electromagnetic force (control force) Fso proportional to the supply current I of 8 acts only, and the spool 32 stops at the position where the forces due to these act in balance. Since the solenoid current I is set to the reference current Ib as described above and exhibits the fluid pressure control characteristic a of FIG. 6 because the vehicle is not braking now, the electromagnetic force Fso generated by the reference current Ib causes the spool 32. At the stroke position shown in FIG. 1, the input valve port 35 is closed and the drain valve port 36 is opened. Therefore, the output pressure Pc of the hydraulic control valve 26 is entirely drained.

(2) Braking state (anti-skid non-control range) When the master cylinder hydraulic pressure Pm is generated by depressing the brake pedal 23 in this state, this acts as a pilot pressure in the shutoff valve 56 and the chamber 45 of the hydraulic control valve 26. Is applied. The shut-off valve 56 opens when the master cylinder hydraulic pressure Pm as the pilot pressure becomes equal to or higher than the minute set value Pms, supplies the pressure source pressure of the circuit 54 to the hydraulic pressure control valve 26, and causes the hydraulic pressure control valve 26 to operate as follows. Function as
The fail-safe valve 25 is shut off so that the output pressure Pc of the hydraulic pressure control valve 26 can be made substantially equal to the brake hydraulic pressure Pw via the hydraulic pressure synthesizer 28.

The master cylinder hydraulic pressure Pm as the pilot pressure supplied to the chamber 45 causes the bellows 44 to contract,
The spring force Fspi of the spring 42 acts on the spool 32 via the push rod 43 and the cap 41. The force due to pilot pressure is
If the pressure receiving area of is Am, then Pm · Am.

As a result, the spool 32 is moved leftward in the drawing to open the input valve port 35 and reduce the opening degree of the drain valve port 36, so that an output pressure Pc is generated.
The spool 3 acts on the pressure receiving area difference Aw between 2a and 32b.
Push back 2. When the output pressure Pc rises to a value corresponding to the pilot pressure force Pm · Am, the spool 32
Returns to the position shown and maintains the output pressure Pc at this value. Here, the output pressure Pc is calculated from the balance formula of the force acting on the spool 32.

## EQU00002 ## Pc = (Am / Aw) Pm + (Fspi-Fspd-Fso) / Aw ... (2) By the way, since the solenoid current I that determines the electromagnetic force Fso is the reference current Ib as described above, the output pressure Pc is

[Formula 3] Pc = (Am / Aw) Pm (3), which is almost the same as the output pressure Pc.
After all, the master cylinder hydraulic pressure Pm is controlled in a predetermined manner along the characteristic a in FIG.

However, in this example, the shutoff valve 56 is operated while the master cylinder hydraulic pressure Pm is less than the minute set value Pms.
Is kept closed, and the hydraulic pressure control valve 26 is released from the pressure source circuit 54.
Since the source pressure is not input to, the hydraulic pressure control valve output pressure Pc, that is, the brake hydraulic pressure Pw is maintained at 0 in this region as shown in FIG. Therefore, normally, when the control system of the solenoid 38 fails and the current I becomes 0, the master cylinder hydraulic pressure Pm
Output pressure P even when the brake is less than the set value Pms
While c (brake hydraulic pressure Pw) becomes a value indicated by ΔPw in FIG. 6 obtained by substituting Fso = 0 in the above equation (2), the brake hydraulic pressure Pw is set to 0 in response to the non-operation of the brake. It is possible to keep it, and at the time of the failure, it is possible to eliminate the uncomfortable feeling that the wheels are braked despite the non-operation of the brake.

The hydraulic pressure control characteristic of FIG. 2 is also very advantageous in that a jump-in function in which the brake hydraulic pressure Pw rises sharply at the beginning of braking operation can be generated.
Further, it goes without saying that the shut-off valve 56 can have the same operational effect even if it is inserted into the brake operating pressure output circuit 27 instead of being inserted into the source pressure input circuit 54 of the hydraulic pressure control valve 26 as shown in FIG. .

(3) Anti-skid control state In the anti-skid control range in which the wheels largely slip during the above-mentioned braking, and the slip ratio exceeds the set value, the controller 61 reduces the brake fluid pressure reduction amount required for slip prevention. Calculate ΔP1 (see, for example, FIG. 6), and in order to achieve this pressure reduction, the solenoid current I is calculated from the reference current Ib by ΔI.
Only increase. As a result, the hydraulic pressure control valve 26 increases the electromagnetic force Fso in accordance with the current change amount ΔI in the above equation (2), and as a result, the output pressure P
c, and therefore the brake fluid pressure Pw is reduced from to in FIG. This brake fluid pressure decrease amount is the above-mentioned predetermined value ΔP1.
The slip of the wheels can be avoided.

(4) Yaw rate feedback control Although not shown, the controller 61 calculates the yaw rate target value that the vehicle should originally generate from the steering wheel steering angle detected by the steering angle sensor and the vehicle speed calculated as described above. The yaw rate feedback control for matching the actual yaw rate of the vehicle detected by the yaw rate sensor with the target value can be performed as follows. That is,
The controller 61 obtains a braking force difference between the left and right wheels for realizing the above yaw rate matching, and in order to cause this braking force difference, one of the left and right wheels reduces the brake fluid pressure Pw by increasing the solenoid current I. Or, the other brake fluid pressure Pw is increased by decreasing the solenoid current I,
The yaw rate of the vehicle can be made to match the target value.

(5) Traction control state Traction control for preventing acceleration slip of the wheels by automatic braking of the wheels will be described below. When the controller 61 determines the acceleration slip of the wheel based on the information from the sensors 63 and 64, it turns on the traction control valve 55 and supplies the pressure source pressure of the circuit 54 to the chamber 40 as a pilot pressure. This pressure is on the other hand the shutoff valve 5
6 is opened, and on the other hand, the pin 39 and the cap 41 act as a reaction force to act on the spool 32 and urge it to the left in the figure. Of course, since the master cylinder hydraulic pressure Pm is not generated, there is no pilot pressure in the chamber 45.

The pressure of the pressure source in the chamber 40 causes the spool 32 to move leftward in the drawing, opens the input valve port 35, and reduces the opening degree of the drain valve port 36, so that an output pressure Pc is generated, and this output pressure is the land 32a. , 32b, and the spool 32 is pushed back by acting on the pressure receiving area difference. When the output pressure Pc rises to a value corresponding to the force due to the pressure in the chamber 40, the spool 32 returns to the position shown in the figure and maintains the output pressure Pc at this value. Here, the controller 61 controls the electromagnetic force Fso by adjusting the current I to the solenoid 38, and thereby the output pressure Pc, and thus the brake fluid pressure Pw, is a minimum value necessary to suppress acceleration slip of the wheels. Can be arbitrarily determined. This brake fluid pressure Pw can brake the wheels with a corresponding force to prevent acceleration slip of the wheels.

(6) At the time of failure Even though the shutoff valve 56 is opened, the hydraulic pressure control valve 2
When a failure occurs such that the source pressure from the circuit 54 is not supplied to the circuit 6, the fail-safe valve 25 opens the circuit 24 in response to the failure. As a result, the master cylinder hydraulic pressure P
The m is supplied as it is to the wheel cylinders 22 as the brake fluid pressure Pw, and the braking is not disabled even in the case of a failure such that the original pressure disappears.

FIG. 3 shows another example of the present invention. In the above example, while the brake is not operated, the shut-off valve 56 is closed so that the source pressure is not supplied to the hydraulic pressure control valve 26, and the solenoid control system is prevented from malfunctioning. Even when the solenoid electromagnetic force Fso disappears during non-operation, resistance means is provided to prevent the hydraulic pressure control valve spool 32 from performing a stroke that generates brake hydraulic pressure, and the same failure countermeasure is taken. . In this example, the resistance means is composed of a piston 71. This piston 71 is spring 7
The solenoid plunger 38a is brought into contact with the left end surface of the solenoid plunger 38a in FIG. 2 by this, so that the spring force Fk of the spring 72 acts on the plunger 38a in the direction of cooperating with the solenoid electromagnetic force Fso.

The chamber 73 faces the end face of the piston 71 far from the spring 72, and the master cylinder hydraulic pressure Pm of the circuit 24 is supplied to this chamber. Then, the spring force of the spring 72 and the chamber 7
The relationship with the pressure receiving area of the piston 71 facing 3 is that, while the master cylinder hydraulic pressure Pm is less than the same minute set value Pms as in the above embodiment, the spring force Fk is applied to the plunger 38a, but the master cylinder hydraulic pressure Pm is While the set value Pms or more, the piston 71 is stroked to a position away from the plunger 38a, and the spring force Fk is changed to the plunger 38a.
The relationship does not act on.

In this embodiment, the spring force Fk acts on the spool 32 in the same direction in addition to the solenoid electromagnetic force Fso while the master cylinder hydraulic pressure Pm is less than the minute set value Pms. Therefore, the hydraulic control valve output pressure Pc is controlled by the following equation.

## EQU00004 ## Pc = (Am / Aw) Pm + (Fspi-Fspd-Fso-Fk) / Aw (4) Here, the electromagnetic force Fso is caused by a failure of the solenoid control system.
When is 0,

[Formula 5] Fspi-Fspd-Fso-Fk ≦ 0 (5) If the spring force Fk is determined to be (5), the master cylinder hydraulic pressure Pm is less than the minute set value Pms, and the brake is not operated. Nevertheless, the inconvenience that the output pressure Pc, that is, the brake fluid pressure Pw is generated due to the failure,
It can be avoided in the same manner as in the example described above.

During the brake operation in which the master cylinder hydraulic pressure Pm is equal to or higher than the set value Pms, the piston 71 is stroked against the spring 72 by the master cylinder hydraulic pressure and is separated from the plunger 38a. Fk is not input to the spool 32, and the fluid pressure control can be executed in a predetermined manner according to the equation (2).

FIG. 4 shows still another example of the present invention. In this example, the resistance means is constituted by a friction resistance type instead of the spring loaded piston 71. That is, the cap 81 that receives the protruding end of the pin 39 protruding from the spool 32, and the spool 3
The spring 82 is contracted between the two corresponding end faces to urge the cap 81 in the direction away from the spool 32, and the cap 81 is prevented from coming off by the inner peripheral flange 81 of the cap 81.
This is done by the engagement of a with the outer flange 32c of the spool 32. The outer periphery of the cap 81 is slidably fitted in the housing 31, and the friction ring 83 is attached to the cap fitting surface in the housing. The friction ring 83 applies the frictional force Ff to the cap 81 only while the spool 32 moves leftward from the illustrated neutral position by a distance α.

The cap 81 far from the spool 32
A spring 84 acts on the push rod 43 that comes into contact with the end surface of the push rod 43, thereby pushing the push rod 43 into the cap 81.
Press on. The spring force of the spring 84 is the same as the spring force Fspi of the spring 42 in each of the above-described embodiments, and the spring force Fspi is used as the push rod 43, the cap 81, and the spring 8.
Similarly to the above-described respective embodiments, the spool 32 is applied in the same direction via 2 to cause a similar hydraulic pressure control action.

By the way, the above distance α and the ring 8
In relation to the master cylinder hydraulic pressure receiving area Am of the bellows 44 in the chamber 45 and the spring force of the spring 82, the frictional force Ff by 3 is a minute set value Pms in which the master cylinder hydraulic pressure Pm is the same as that in each of the embodiments. When it becomes the above, it is determined that the cap 81 strokes beyond α and comes off the ring 83, and the above-mentioned frictional force is not applied.

In the structure of this example, while the master cylinder hydraulic pressure Pm is less than the minute set value Pms, the cap 81 maintains the relative position shown in the drawing with respect to the spool 32 and strokes together with the spool 32 to cause friction by the ring 83. Force F
f is added to the stroke of the spool 32. Therefore,
The hydraulic pressure control valve output pressure Pc is controlled by the following equation.

## EQU6 ## Pc = (Am / Aw) Pm + (Fspi-Fspd-Fso-Ff) / Aw (6) Here, due to a failure of the solenoid control system, the electromagnetic force Fso is generated.
When is 0,

## EQU00007 ## If the frictional force Ff is determined so that Fspi-Fspd-Fso-Ff≤0 (7), the master cylinder hydraulic pressure Pm is less than the minute set value Pms and the brake is not operated. Nevertheless, the inconvenience that the output pressure Pc, that is, the brake fluid pressure Pw is generated due to the failure,
It can be avoided in the same manner as in the example described above.

During the brake operation in which the master cylinder hydraulic pressure Pm becomes equal to or greater than the set value Pms, the master cylinder hydraulic pressure causes the cap 81 to be relatively displaced with respect to the spool 32 by α or more, so that the friction force Ff by the ring 83 is generated. The stroke of the spool 32 is no longer involved. Therefore,
The hydraulic pressure control valve can control the output pressure Pc, that is, the brake hydraulic pressure Pw, in a predetermined manner in accordance with the equation (2).

[0050]

As described above, according to the brake fluid pressure control device of the present invention, the source pressure input circuit of the fluid pressure control valve or the brake operating pressure output circuit is provided with a pressure corresponding to the brake operating force (example of FIG. 1). Since a master cylinder hydraulic pressure Pm or traction control operating pressure) is less than a set value and a shut-off valve that is closed during brake non-operation is inserted, even if the control force (electromagnetic force Fso in the illustrated example) disappears due to a failure, the brake is applied. As long as the operating force corresponding pressure is less than the set value and the brake is not operated, closing the shutoff valve will prevent the hydraulic control valve from outputting the brake operating pressure. Nevertheless, it is possible to solve the problem that the brake operating pressure is generated due to the failure.

Further, as described in claim 2, the brake fluid pressure control device of the present invention prevents the stroke of the fluid pressure control valve spool due to the disappearance of the control force while the pressure corresponding to the brake operation force is less than the minute set value. Since the resistance means (the spring loaded piston 71 in the example of FIG. 3 and the friction ring 83 in the example of FIG. 4) is provided, the control force disappears while the brake is not operated when the pressure corresponding to the brake operating force is less than the minute set value. The stroke of the hydraulic pressure control valve spool caused by is blocked by the resistance means. Therefore, even if the control force is lost due to a failure while the brake operating force-corresponding pressure is less than the set value and the brake is not being operated, the hydraulic pressure control valve spool will be held at the stroke position when the brake is not operating, and the brake will not operate. It is possible to solve the problem that brake operating pressure is generated due to the failure even during operation.

[Brief description of drawings]

FIG. 1 is a system diagram of a hydraulic brake system relating to only one wheel, showing an embodiment of a brake hydraulic pressure control device of the present invention.

FIG. 2 is a hydraulic pressure control characteristic diagram of a hydraulic pressure control valve in the same example.

FIG. 3 shows another example of the brake fluid pressure control device of the present invention,
It is a system diagram of a hydraulic brake system related to only one wheel.

FIG. 4 is a system diagram of a hydraulic brake system relating to only one wheel, showing still another example of the brake hydraulic pressure control device of the present invention.

FIG. 5 is a system diagram of a hydraulic brake system illustrating a conventional brake hydraulic pressure control device.

FIG. 6 is a diagram showing a hydraulic pressure control characteristic of a conventional brake hydraulic pressure control device and a problem when the electromagnetic force control system in the hydraulic pressure control valve of the device fails.

[Explanation of symbols]

 21 Brake master cylinder 22 Wheel cylinder 23 Brake pedal 25 Fail-safe valve 26 Hydraulic control valve 27 Brake operating pressure output circuit 32 Stepped spool 35 Input valve port 36 Drain valve port 38 Solenoid 40 Pilot chamber 41 Cap 43 Push rod 44 Bellows 45 Pilot room 51 Pump 53 Accumulator 54 Source pressure input circuit 55 Traction control 56 Shut-off valve 61 Controller 62 Brake switch 63 Front-rear G sensor 64 Wheel speed sensor 71 Spring-loaded piston (resistive means) 81 Cap 83 Friction ring (resistive means)

Claims (2)

[Claims] 1. A brake operating force-corresponding pressure corresponding to a brake operating force is used as a pilot pressure, and a brake operating pressure is created by using a pressure from a pressure source as a source pressure. The brake operating pressure is directed in a direction opposite to the pilot pressure. In a brake fluid pressure control device equipped with a fluid pressure control valve that can be reduced by increasing the acting control force, a pressure corresponding to the brake operating force is set in a source pressure input circuit or a brake operating pressure output circuit of the fluid pressure control valve. A brake fluid pressure control device, characterized in that a shut-off valve that is closed when the value is less than the value is inserted. 2. A brake operating pressure is generated by using a pressure from a pressure source as a source pressure by a stroke of a spool which receives a brake operating force corresponding pressure corresponding to a brake operating force as a pilot pressure in one direction, and opposes the pilot pressure. In a brake fluid pressure control device comprising a fluid pressure control valve capable of reducing the brake working pressure by receiving a control force in a direction, the spool strokes when the brake operating force corresponding pressure is less than a set value. A brake fluid pressure control device comprising: resistance means for preventing a stroke of the spool due to the disappearance of the control force.