JPH1148930A - Braking device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide such a differential pressure control valve and a brake control device with excellent response as being capable of precisely controlling differential pressure by mechanically controlling the operation of the differential pressure control valve. SOLUTION: A braking device for a vehicle has a differential pressure control valve 4 disposed in a pipe passage 3 connecting a master cylinder 1 to a wheel cylinder 2. The first communication hole 6 in the differential pressure control valve 4 is communicated with the master cylinder 1 and the second communication hole 7 is connected to the wheel cylinder 2. In a pipe passage 8 bypassing the differential pressure control valve 4, a pump 9 is disposed with the inlet side as the side of the master cylinder 1 and the outlet side as the side of the wheel cylinder 2. A pipe passage 11 branching from between the master cylinder 1 in the pipe passage 3 and the differential pressure control valve 4 is connected to the third communication hole 12 in the differential pressure control valve 4, where a control valve (a shutoff valve) 13 as a solenoid valve is disposed to control the pipe passage 11 at two positions of opening/closing. The shutoff valve 13 is a normally open valve (an N/O valve) which is closed in electrification.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle brake device which can adjust a differential pressure of a brake fluid pressure, for example.

[0002]

2. Description of the Related Art Conventionally, in a vehicle brake system including a brake fluid pipe and a control valve for opening and closing the pipe, when a brake pedal is depressed, a predetermined value is determined in accordance with the amount of depression and the depressing force. The braking force is set so as to be obtained.

In this type of vehicle brake device,
A brake booster, such as a vacuum booster, is used to increase the depressing force when the brake pedal is depressed and to improve the braking force by increasing the master cylinder pressure and, consequently, the wheel cylinder pressure.

However, since a vacuum booster or the like has a large physique and is sometimes difficult to be mounted on a vehicle, a technique for replacing the same has been proposed. For example, JP-A-8-230634 discloses that when performing anti-skid control or traction control, control of a return pump, a switching valve, and a suction valve is performed depending on a signal indicating operation of a brake pedal.
Techniques have been proposed to take over the function of the vacuum booster.

[0005]

However, when a differential pressure control valve which is an on-off type solenoid valve is used as the switching valve in order to directly control the pressure on the wheel cylinder side, the differential pressure control is performed. Since the current value of the applied current for driving the valve and the duty ratio thereof are determined by the computer that controls the driving, the operation may be affected by calculation delay and calculation accuracy.

Therefore, the responsiveness and accuracy of the differential pressure control valve are deteriorated. For example, even if the driver steps on the brake pedal to increase the master cylinder pressure (M / C pressure), an appropriate amount of the master cylinder pressure (M / C pressure) can be obtained. Only wheel cylinder pressure (W / C pressure)
However, there is a problem that does not rise, or conversely, rises too much.

As a countermeasure against this, there has been proposed a configuration in which (ΔW / C pressure / ΔM / C pressure) is mechanically determined by a difference in pressure receiving area of a valve element arranged in the differential pressure control valve. If this differential pressure control valve is to be used for control of, for example, a pressure amplification assist brake, precise control by an electronic control unit is required, which is not always sufficient.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has an excellent responsiveness by mechanically controlling the operation of a differential pressure control valve, and is capable of accurately controlling the differential pressure. It is an object to provide a control valve and a brake control device.

[0009]

According to a first aspect of the present invention, there is provided a brake fluid pressure generating means (for example, a master cylinder) for generating a brake fluid pressure during braking of a vehicle, and receiving brake fluid pressure from the brake fluid pressure generating means. Wheel brake force generating means (wheel cylinder) for generating wheel braking force, brake fluid pressure on the brake fluid pressure generating means side and brake fluid pressure on the wheel braking force generating means side are introduced to In a vehicle brake system including a differential pressure control valve that generates a differential pressure between the differential pressure control valve and the wheel braking force generating means, an introduction path for introducing pilot pressure to the differential pressure control valve, and communication and interruption of the introduction path. And a control valve for performing a differential pressure characteristic of the differential pressure control valve by a pilot pressure when an introduction path is blocked by the control valve.

Therefore, by applying this vehicle brake device to, for example, the structure shown in FIG. 16, it is possible to make different brake fluid pressures applied to, for example, front wheels and rear wheels without using a pump. That is, the pilot pressure is sealed by blocking the introduction path by the control valve, and the sealed pilot pressure is caused to act on the differential pressure control valve, so that the differential pressure characteristic can be changed, for example, as shown in FIG.

Specifically, the differential pressure characteristic is changed by setting the break point pressure of the differential pressure control valve, for example, by substantially changing the set load of a spring for urging the valve element by the pilot pressure. Can be. A second aspect of the present invention provides a brake fluid pressure generating means for generating a brake fluid pressure during vehicle braking, a wheel braking force generating means for receiving a brake fluid pressure from the brake fluid pressure generating means and generating a wheel braking force, A pump that sucks the brake fluid from the fluid pressure generating means side and discharges it to the wheel braking force generating means side, and introduces the brake fluid pressure on the brake fluid pressure generating means side and the brake fluid pressure on the wheel braking force generating means side, A differential pressure control valve that generates a differential pressure between the brake fluid pressure generating means side and the wheel braking force generating means side when the pump moves the brake fluid, A differential pressure control valve is provided with an introduction path for introducing pilot pressure to the differential pressure control valve, and a control valve for communicating and shutting off the introduction path. Characteristics A brake system being characterized in that a variable.

In the present invention, when the pump is operated, the brake fluid pressure (for example, the master cylinder pressure) on the brake fluid pressure generating means side and the brake fluid pressure (for example, the master cylinder pressure) on the wheel braking force generating means side are controlled by the differential pressure control valve. Wheel cylinder pressure)
And a differential pressure can be generated. In particular,
For example, the wheel cylinder pressure can be increased from the master cylinder pressure.

The generated differential pressure is usually determined by a set load of a spring that biases a valve disposed inside the differential pressure control valve. That is, as the set load increases, for example, the break point pressure of the differential pressure characteristic shown in FIG. 6 increases. Therefore, if the pilot pressure is introduced into the differential pressure control valve and sealed by the control valve, and this pilot pressure is reflected in the set load, the differential pressure characteristics can be changed arbitrarily.

Further, once the pilot pressure is confined by the control valve, the degree of pressure increase (ie, △ W / C pressure / △ M / C pressure) among the differential pressure characteristics of the differential pressure control valve is mechanically determined. Since it is determined, there is no need to control the current value or applied current to the solenoid according to the set differential pressure as in the related art. Therefore, for example, a remarkable effect that the wheel cylinder pressure can be set quickly and precisely with respect to the master cylinder pressure is exhibited.

According to a third aspect of the present invention, in the vehicle brake device, the pilot pressure is a brake fluid pressure of a brake fluid pressure generating means. That is, for example, a master cylinder pressure can be adopted as the pilot pressure. In this case, the master cylinder pressure is directly detected or
Alternatively, since the master cylinder pressure is increased or decreased by the pedaling force or the like, the differential pressure characteristics can be set as desired by detecting the pedaling force or the like and driving the control valve when the pedaling force or the like has a predetermined value to confine the pilot pressure. .

According to a fourth aspect of the present invention, in the vehicle brake device, the differential pressure control valve has a valve mechanism having a first valve body having a pressure receiving area difference. The present invention specifically shows the structure of the differential pressure control valve. Since the first valve body has a pressure receiving area difference, the first valve body moves in a predetermined sliding direction by the received pressure, for example, a spring or the like. Balance by receiving bias. Therefore, in this balanced state, the differential pressure between the respective pressure receiving sides can be maintained.

According to a fifth aspect of the present invention, the valve mechanism comprises a first valve body and a second valve body biased in a separating direction by a spring,
The distal end side of the first valve body communicates with the brake hydraulic pressure generating means side and is set so that brake hydraulic pressure is applied in the direction of compressing the spring, and the side surface side of the first valve body is connected to the pump side. It is set so that the brake fluid pressure is applied in the direction in which the springs are separated from each other, and the rear end side of the second valve body in the direction opposite to the first valve body is
A brake device for a vehicle, characterized in that the brake device is communicated with a brake fluid pressure generating means side through an introduction path in which a control valve is arranged so that brake fluid pressure is applied in a direction to compress a spring. .

The present invention specifies the structure of the differential pressure control valve more specifically. In the present invention, the first valve body and the second valve body are separated by a spring located between the two valve bodies. It is set so as to be urged in the separating direction and to apply pilot pressure to the second valve body. With this, when the first valve element attempts to move against the urging force of the spring due to the operation of the pump, the pilot pressure is transmitted to the first valve element via the urging force of the spring. As shown in FIG. 6, the break point pressure increases. That is, the differential pressure characteristic can be changed by introducing the pilot pressure.

According to a sixth aspect of the present invention, there is provided a vehicle brake having a structure in which a small-diameter portion protruding in the axial direction is provided from a distal end side of the first valve body, and the small-diameter portion is sealed. Device. In the present invention, by having a small diameter portion,
At the tip end side of the first valve body, the pressure receiving area to which the brake fluid pressure is applied substantially decreases. Therefore, for example, the urging force of the spring set against the pressure applied from the distal end side of the first valve body can be set small. As a result, the spring can be downsized, so that the differential pressure control valve itself can be downsized.

According to a seventh aspect of the present invention, there is provided a vehicle brake device provided with an auxiliary spring for urging the first valve body toward the distal end. The spring constant of the spring that biases the first valve body is
For example, in the case of performing high G assist, it is necessary to increase the value in order to ensure the controllability, but in this case, the break point pressure increases to some extent. Therefore, in the present invention, FIG.
As exemplified in FIG. 1, by using the auxiliary spring, the spring constant of the spring can be reduced, and as a result, the minimum breaking point pressure can be set low. Thereby, the change range of the differential pressure characteristics can be expanded.

According to an eighth aspect of the present invention, there is provided a brake for a vehicle, wherein a brake fluid pressure applied to a wheel braking force generating means is adjusted by driving a pump and a control valve in accordance with a depression state of a brake pedal. Device. The present invention relates to a device for controlling a so-called pressure amplification assist brake. Therefore, in a state where the pilot pressure is contained by driving the control valve, for example, by driving the pump in accordance with the depressed state of the brake pedal such as depressing force or depressing speed, based on a predetermined differential pressure characteristic,
For example, a braking pressure can be improved by generating a differential pressure so as to be a wheel cylinder pressure higher than the master cylinder pressure.

According to a ninth aspect of the present invention, when it is determined that a failure has occurred in the brake booster based on the negative pressure introduced into the brake booster, the pump and the control valve are driven to provide the wheel braking force. A brake device for a vehicle, wherein a brake fluid pressure applied to a generating means is adjusted.

The present invention relates to an apparatus for performing control when a brake booster fails. Therefore, when the brake booster fails, the pump is driven in a state in which the control valve is driven to confine the pilot pressure, so that the wheel cylinder becomes higher than the master cylinder pressure, for example, based on the predetermined differential pressure characteristic. , The braking force can be improved instead of the boosting function that does not function due to the failure of the brake booster.

According to a tenth aspect of the present invention, when it is determined that the upper limit of the boosting action of the brake booster has been reached based on the state of the brake fluid pressure of the brake fluid pressure generating means or the negative pressure introduced to the brake booster. Is a vehicle brake device characterized in that a pump and a control valve are driven to adjust a brake fluid pressure applied to a wheel braking force generating means.

The present invention relates to an apparatus for controlling so-called high G assist. Therefore, when the upper limit of the boosting action of the brake booster is reached, the pump is driven in a state in which the control valve is driven and the pilot pressure is confined. By generating a differential pressure so as to obtain a higher wheel cylinder, the braking force can be further improved.

The invention according to claim 11 is such that the pump and the control valve are driven in accordance with the load applied to the vehicle and the brake fluid pressure of the brake fluid pressure generating means, so that the influence of the load is reduced. A vehicle brake device for adjusting a brake fluid pressure applied to a power generating means.

The present invention relates to a device for controlling so-called braking force distribution. Therefore, by driving the pump in a state where the pilot pressure is contained by driving the control valve, for example, the wheel cylinder pressure on the front wheel side is made higher than the wheel cylinder pressure on the rear wheel side based on a predetermined differential pressure characteristic. Can be.

Further, since the distribution of the wheel cylinder pressure can be set to a desired value by the pilot pressure, for example, by setting the pressure distribution according to the load,
The braking force distribution can also be set. Therefore, for example, even when the loads are different, the same braking force (vehicle deceleration G) can be realized as a whole vehicle with the same pedaling force.

According to a twelfth aspect of the present invention, when the vehicle turns, the brake fluid pressure applied to the wheel braking force generating means is adjusted by driving the pump and the control valve according to the steering angle and the yaw rate. Vehicle brake device. The present invention relates to a device for performing so-called turning trace control. Therefore, by driving the pump in a state where the pilot pressure is contained by driving the control valve, based on a predetermined differential pressure characteristic, for example, a differential pressure is generated so as to be a wheel cylinder higher than the master cylinder pressure. Alternatively, for example, the turning performance at the time of turning can be improved by increasing the wheel cylinder pressure on the turning inner wheel side than the wheel cylinder pressure on the turning outer wheel side.

According to a thirteenth aspect of the present invention, there is provided a brake fluid pressure generating means for generating a first brake fluid pressure at the time of vehicle braking, and a wheel braking force generated by receiving the first brake fluid pressure from the brake fluid pressure generating means. A brake fluid generating means, a pump for sucking the brake fluid as the first brake fluid pressure from the brake fluid pressure generating means side, and discharging the brake fluid to the wheel braking force generating means side; When done,
A differential pressure control valve capable of generating a differential pressure of the brake fluid between the brake fluid pressure generating means and the wheel braking force generating means when the first brake fluid pressure is equal to or higher than a predetermined pressure; An introduction path that is provided in the valve and connects the pressure accumulation chamber that introduces the brake fluid of the first brake fluid pressure with the brake fluid generation means;
A control valve that communicates and shuts off the introduction path, and the differential pressure control valve brakes from the wheel braking force generation means to the brake fluid pressure generation means in accordance with the state of introduction of the brake fluid into the accumulation chamber. A vehicle brake device characterized by changing a predetermined pressure that is a threshold value for performing pressure attenuation when a liquid flows.

In the present invention, too, the first
The brake fluid pressure of the differential pressure control valve is confined by the control valve, and the threshold value (ie, the break point pressure) is changed by the first brake fluid pressure. Can be changed.

Similarly, once the introduction path is cut off by the control valve, the differential pressure is determined mechanically, so that the responsiveness and accuracy are superior to those in the case of using the conventional current control differential pressure control valve. ing.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a vehicle brake system according to the present invention will be described below in detail with reference to the drawings by way of examples (embodiments). (Example 1) a) First, the configuration of the vehicle brake device will be described. FIG. 1 shows an example of an apparatus configuration related to one of the four wheels.

As shown in FIG. 1, in the vehicle brake system of the present embodiment, a differential pressure control valve 4 is disposed in a pipe 3 connecting the master cylinder 1 and the wheel cylinder 2. The first communication hole 6 communicates with the master cylinder 1 side, and the second communication hole 7 is connected with the wheel cylinder 2 side.

A pump 9 is arranged in the pipeline 8 bypassing the differential pressure control valve 4 so that the suction side is on the master cylinder 1 side and the discharge side is on the wheel cylinder 2 side. Further, a pipeline 11 branched from the master cylinder 1 of the pipeline 3 and the differential pressure control valve 4 is connected to a third communication hole (introduction channel) 12 of the differential pressure control valve 4. A control valve (hereinafter, referred to as a shut-off valve) 13 that is an electromagnetic valve that controls the pipe line 11 to the open / close two position is disposed at 11. The shut-off valve 13 is a normally open valve (N /
O valve).

A brake booster 16 is connected to the master cylinder 1 to boost the depressing force by introducing a negative pressure into the brake pedal 14 when the brake pedal 14 is depressed. As shown in FIG. 2, the vehicle brake device includes a well-known CPU 17a, a ROM 17b, a RAM 17
c and an electronic control unit (EC
U) 17.

The input / output unit 17d of the ECU 17 includes, for example, a stop switch 21 for detecting depression of the brake pedal 14, a stroke sensor 22 for detecting the stroke of the brake pedal 14, a pedal force sensor 23 for detecting the depression force of the brake pedal 14, Master cylinder pressure (M / C pressure)
, A cylinder pressure sensor 26 for detecting a wheel cylinder pressure (W / C pressure), a negative pressure sensor 27 for detecting a negative pressure introduced into the brake booster 16, and a load Various sensors such as a load sensor 28 for detecting a load and a wheel speed sensor 29 for detecting a wheel speed are connected, and the detection signals are input. Note that a master cylinder pressure sensor 24 may be used instead of the pedaling force sensor 23.

The input / output unit 17d of the ECU 17 includes:
For example, a pump motor 31 for driving the pump 9 and a shutoff valve 1
Various actuators such as 3 are connected, and control signals are output to them. b) Next, the structure of the differential pressure control valve 4 used in the present embodiment will be described.

As shown in FIG. 3, the differential pressure control valve 4 has a first valve body (first control piston) 42 and a second valve body (second control piston) 43 that can move left and right in the figure. Valve mechanism 41
have. The first and second control pistons 42, 43
The first and second dish-shaped members 46 and 4 are respectively
7 is urged in the separating direction.

The first and second dish-like members 46 and 47 are formed with a hollow portion 45 sealed by first and second wall portions 4a and 4b.
Are located in The first and second dish-shaped members 46, 4
Reference numeral 7 is separate from the first and second control pistons 42 and 43, and is not joined to each other.

A rubber seat member 48 is externally fitted to the first control piston 42. The distal end portion (cross-sectional area S1) 42a of the first control piston 42 located on the left side of the drawing with respect to the sheet member 48 slides left and right in the distal end hollow portion 51, and the distal end hollow portion 51 Through the master cylinder 1 side. Therefore, this first communication hole 6
, A master cylinder pressure is applied to the distal end side of the first control piston 42.

The central portion (cross-sectional area S2) 42 of the first control piston 42 located on the right side of the drawing with respect to the sheet member 48.
b moves left and right in the outer peripheral hollow portion 52, and the outer peripheral hollow portion 52 communicates with the wheel cylinder 2 side and the discharge side of the pump 9 via the second communication hole 7. Therefore, this second
Through the communication hole 7, the central portion 42 of the first control piston 42
Wheel cylinder pressure is applied to b.

The seat portion 4 is formed by the left end surface 48a of the seat member 48 and the step portion 42c of the first control piston 42.
9, the communication between the first communication hole 6 and the second communication hole 7 is interrupted by the step 42c sitting on the left end surface 48a. On the other hand, a rear end hollow portion 53 on the right side in the figure in which the second control piston 43 is fitted is in communication with the master cylinder 1 via the third communication hole 12 and the conduit 11. Therefore, when the shut-off valve 13 is OFF (OFF) and is in the open state, the second control piston 43 is connected through the third communication hole 12.
The master cylinder pressure as pilot pressure is applied to the rear end (cross-sectional area S3) 43a of the
N), the shut-off valve 1 is provided in the third communication hole 12.
The pilot pressure (containment pressure) at the time when 3 is turned off is held, and the confinement pressure is applied to the rear end 43a of the second control piston 43.

In this embodiment, the sectional area S2 = the sectional area S
3, which is set so as to satisfy the relationship of the sectional area S1> the sectional area S2 and the sectional area S3. The set load, which is the urging force of the main spring 44, sets a break point pressure that determines the differential pressure characteristic of the differential pressure control valve 4, as shown in FIG. Pressure increases. In this embodiment, the break point pressure when the shut-off valve 13 is not driven is set to P0, corresponding to the reference set load F1 (when no other external force is applied).

C) Next, the operation of the differential pressure control valve 4 will be described in more detail. i) First, the case where the shut-off valve 13 is turned off at the time of low pressure cut, that is, when the master cylinder pressure is low will be described with reference to FIG. When the brake pedal 14 is not depressed while the pump motor 31 and the shutoff valve 13 are off, neither the master cylinder pressure nor the wheel cylinder pressure is generated.

Therefore, in this case, as shown in FIG. 4A, the first and second plate-like members 46 and 47 are pressed in the separating direction by the urging force of the main spring 44, and the first and second plate-like members 46 and 47 are respectively pressed. ,
It is seated on the second walls 4a, 4b. In this case, the first and second control pistons 42 and 43 can move freely in the left and right directions in the figure.

Next, the pump motor 31 and the shutoff valve 13
When the brake pedal 14 is depressed shallowly in the state where is turned off, low pressure is generated in both the master cylinder pressure and the wheel cylinder pressure. Therefore, in this case, FIG.
As shown in (b), since the low master cylinder pressure is introduced through the third communication hole 12, the second control piston 43
Is pressed to the left of the figure. Then, the second dish-shaped member 47 slightly opposes the urging force of the main spring 44 (x
1) Move. As a result, the main spring 44 is in a compressed state, so that the set load of the main spring 44 is substantially increased. For example, the set load is from F1 to F2
(However, F2> F1).

As described above, the break load of the differential pressure control valve 4 is determined by the set load of the main spring 44, and the set load of the main spring 44 is reduced by the master cylinder pressure introduced into the third communication hole 12. By substantially increasing, the break point pressure increases, for example, from P0 in FIG. 6 to P1.

At this time, since the flow path is not completely shut off by the seat portion 49, the first control piston 42 is not urged to the right in the drawing, so that the first plate-like member 4 is not urged.
6 remains seated on the first wall 4a. Therefore, in this state, when the shut-off valve 13 is turned on and the pipeline 11 is shut off, the brake fluid pressure in the third communication hole 12 is sealed, and the moving state of the second plate-like member 47 is maintained. Therefore, the set load of the main spring 44 is fixed to a value F2 higher than the reference value F1.

Here, the pressure balance in the present differential pressure control valve 4 will be considered. However, each symbol is set as follows. S1: cross-sectional area of the rear end of the first control piston S2: cross-sectional area of the center of the first control piston S3: cross-sectional area of the second control piston PM: pressure on the first communication hole side PW: second communication hole side PP: pressure on the third communication hole side In other words, when the master cylinder pressure starts to increase, the main spring 44
In this case, the force that pushes the second control valve 43 to the left in the drawing, and thus the force that pushes the first control piston 42 to the left, is PP × S3. On the other hand, the first control piston 42
To the right is (PM × S1) −PW × (S1-S
2).

When the shut-off valve 13 is off, the point at which the pressure is balanced can be expressed by the following equation (1):
By substituting and arranging PP, S2 = S3, (PM × S1) −PW × (S1−S2) = PP × S3 (1) PP = PW, and therefore PP = PW = PM.

Here, if the shut-off valve 13 is simply turned on (other states are unchanged), PP = PW =
The state of PM is maintained as it is. Next, in a state where the shut-off valve 13 is turned on and the pump motor 31 is turned on to drive the pump 9 in a state where the low-pressure brake fluid is sealed in the third communication hole 12, that is, the differential pressure control valve 4 is turned on. The case of driving will be described.

First, when the shut-off valve 13 is turned on, the low-pressure brake fluid is confined in the third communication hole 12, thereby substantially increasing the set load of the main spring 44 as described above. The break point pressure is, for example, P1 shown in FIG. Here, when the pump 9 is driven to increase the wheel cylinder pressure (PW), as shown in FIG. 4C, the first control piston 42 is moved to the seat 49 by the pressure balance of the first control piston 42. And moves to the right side of the figure so as to substantially block the flow path. Accordingly, the first dish-shaped member 46 moves rightward in the drawing.
Actually, in order to adjust the differential pressure, a minute opening / closing operation of the seat portion 49 is performed.

In this state, the master cylinder pressure (PM) and the wheel cylinder pressure (PW) change according to a differential pressure characteristic having a break point pressure P1, as shown in FIG. That is, when the master cylinder pressure increases below the breakpoint pressure P1, the wheel cylinder pressure does not increase so much. However, when the master cylinder pressure exceeds the breakpoint pressure P1, the degree of pressure increase rapidly increases.

Considering the pressure balance in the first control piston 42 in this case, the following equation (2) is obtained. PM × S1 = PW × (S1−S2) + F2 (2) By substituting only S2 = S3 into the above equation (1) and rearranging, the following equation (3) is obtained.

PW = {S1 / (S1−S2)} × PM− (PP × S2) / (S1−S2) (3) That is, S1 / (S1−
S2) PW increases by a factor of two.

Ii) Next, referring to FIG. 5, a description will be given of a case where the shut-off valve 13 is turned off at the time of high pressure cut, that is, when the master cylinder pressure is high. The basic operation is the same as at the time of low pressure cut. Therefore, a brief description will be given. When the brake pedal 14 is not depressed while the pump motor 31 and the shutoff valve 13 are off, neither the master cylinder pressure nor the wheel cylinder pressure is generated.

Therefore, in this case, as shown in FIG. 5A, the first and second plate-like members 46 and 47 are pressed in the separating direction by the urging force of the main spring 44, and the first and second plate-like members 46 and 47 are respectively moved to the first position. ,
It is seated on the second walls 4a, 4b. Next, when the brake pedal 14 is depressed deeply while the pump motor 31 and the shutoff valve 13 are off, both the master cylinder pressure and the wheel cylinder pressure become high.

Therefore, in this case, as shown in FIG. 5 (b), the high master cylinder pressure is introduced through the third communication hole 12, so that the second control piston 43 has a higher pressure than the low pressure. Is strongly pressed to the left side of the drawing, and the second plate-like member 47 is pressed.
Moves greatly (x2; x2> x1). This allows
Since the main spring 44 is largely compressed, the set load of the main spring 44 substantially changes to a value F3 larger than F2 at the time of the low pressure. Thereby, the break point pressure increases, for example, to P2 in FIG.

Next, the case where the pump 9 is driven in a state where the shut-off valve 13 is turned on and the high-pressure brake fluid is sealed in the third communication hole 12 will be described. First, when the shut-off valve 13 is turned on, the high-pressure brake fluid is sealed in the third communication hole 12, and as described above,
The break point pressure is, for example, P2 shown in FIG.

Here, when the pump 9 is driven to increase the wheel cylinder pressure (PW), the first control piston 42 is moved by the pressure balance of the first control piston 42 as shown in FIG. Move to the right of In this state, the master cylinder pressure (PM) and the wheel cylinder pressure (PW) are, as shown in FIG.
In accordance with the differential pressure characteristic having

Therefore, when the contained pressure PP is higher than the low pressure, the break point pressure becomes larger.
By adjusting the contained pressure PP:
By selecting the operation timing of the shut-off valve 13, the differential pressure characteristics of the differential pressure control valve 4 can be adjusted.

D) Next, a control process performed by the vehicle brake device having the above-described differential pressure control valve 4 will be described with reference to FIG.
This will be described based on the flowcharts of FIG. Here, the pressure amplification assist brake control (PAB) for increasing the braking force by increasing the wheel cylinder pressure from the master cylinder pressure will be described.

First, at step 100 in FIG. 7, it is determined whether the brake pedal 14 is depressed and the stop switch 21 is turned on. Here, if the determination is affirmative, the process proceeds to step 110, while if the determination is negative, the process is temporarily terminated. In step 110, it is determined whether a condition for performing the pressure amplification assist brake control is satisfied. If the determination is affirmative, the process proceeds to step 120, whereas if the determination is negative, the process ends once. As this determination condition, for example, the pedal stroke speed is set to a predetermined value (XAm
m / sec) or more, or based on a detection value of the pedaling force sensor 23 or the like, the pedaling force change speed is set to a predetermined value (XBkgf /
sec) A condition for determining whether or not it is equal to or longer than sec.

In step 120, the pump motor 31 is turned on to operate the pump 9. Subsequent step 130
Then, the shut-off valve 13 is turned on, and this process is once ended.
Therefore, by the control described above, the wheel cylinder pressure can be made higher than the master cylinder pressure to improve the braking force.

Next, control when the brake booster 16 fails will be described. First, the brake booster 16 is driven by a difference between an atmospheric chamber for introducing the atmosphere and a negative pressure chamber for introducing the negative pressure. In step 200, the pressure (internal pressure) of the negative pressure chamber is set to a predetermined value (−). XCmmHg). Here, if a positive determination is made, it is determined that the necessary internal pressure has not been obtained, that is, the brake booster 16 has failed, and the process proceeds to step 210. On the other hand, if a negative determination is made, it is determined that the brake booster 166 is normal, and this process is once ended.

In step 210, the brake pedal 14
Is determined to determine whether the stop switch 21 is turned on. Here, if a positive determination is made, step 22
Then, if the determination is negative, the process is temporarily terminated. In step 220, the pump 9 is operated by turning on the pump motor 31.

In the following step 230, the shut-off valve 13 is turned on, and this processing is once ended. Therefore, by the above-described control, when the brake booster 16 fails, the braking force is improved instead of the boosting operation using the differential pressure of the brake booster 16 by increasing the wheel cylinder pressure above the master cylinder pressure. Can be.

Next, control of high G assist, that is, control for assisting the boosting action of the brake booster 16 is performed in a region where the pedaling force is as high as a predetermined break point or more and the function of the brake booster 16 cannot be exhibited. it can. The control of the high G assist is almost the same as the control shown in FIG.
Although detailed description is omitted, the control execution conditions in step 110 of FIG. 7 are different.

That is, as the control execution condition, whether the master cylinder pressure exceeds a predetermined value (XDbar) or the differential pressure in the brake booster 16 becomes a predetermined value (XEmmH)
g) or not. Next, a description will be given of a constant treading force brake control, that is, a control for exerting the same braking force with the same treading force even when the load amount or the like is different.

At step 300 in FIG.
The optimum break point pressure is calculated on the basis of the signal from Step 8.
For example, a break point pressure is obtained from a map as shown in FIG. In other words, the higher the weight, the higher the braking force is required. In this case, the break point pressure is reduced so that a large wheel cylinder pressure is generated even with a small pedaling force (master cylinder pressure).

In the following step 310, the master cylinder pressure is set to the containment pressure PPF for setting the optimal break point pressure.
Is determined. If the determination is affirmative, the process proceeds to step 320, whereas if the determination is negative, the process is temporarily terminated. In step 320, in step 220, the pump motor 31 is turned on to operate the pump 9.

In the following step 330, the shut-off valve 13 is turned on, and this processing is once ended. Thereby, when the master cylinder pressure exceeds the containment pressure PPF for setting the optimal break point pressure, the shut-off valve 13 is turned on. Liquid is contained. Therefore, when the pump 9 is operated, the differential pressure characteristic of the optimum break point pressure is obtained.

As described above, in this embodiment, by turning on the shut-off valve 13, a low-pressure containment pressure is generated in the third communication hole 12, thereby effectively increasing the set load of the main spring 44. By doing so, the break point pressure is increased. As a result, a high wheel cylinder pressure can be generated even with the same master cylinder pressure by changing the differential pressure characteristic, so that a high braking force can be exerted even when the pedaling force is the same. That is, a large vehicle deceleration can be realized.

Further, the present embodiment does not calculate the current value to be applied to the differential pressure control valve in accordance with the required differential pressure and performs duty control as in the prior art, After the setting, the wheel cylinder pressure is mechanically increased with respect to the master cylinder pressure, so that control responsiveness is good, and there is no influence of electric noise and the like, so that the accuracy is excellent.

Further, unlike the conventional case, the current value of the applied current and the duty ratio thereof are not determined by the computer which controls the driving, and therefore, there is no influence from the operation delay and the operation accuracy. (Embodiment 2) Next, Embodiment 2 will be described, but the description of the same parts as in Embodiment 1 will be omitted or simplified.

In this embodiment, the minimum break point pressure can be reduced as compared with the first embodiment. Therefore, the structure of the differential pressure control valve is different. As shown in FIG. 11, a differential pressure control valve 51 used in the vehicle brake device according to the present embodiment includes an outer peripheral hollow portion 54 in addition to a main spring 53 disposed in a hollow portion 52.
An auxiliary spring 57 (with a small spring constant) for urging the first control piston 56 to the left in the drawing is provided therein. In addition, the stroke A is set to be larger than the stroke B.

Hereinafter, the operation of this embodiment will be described with reference to specific examples. For example, consider the case where this vehicle brake device is applied to high-G assistance. Maximum break pressure is, for example, 10M
It is necessary to set about Pa. At that time, the main spring 53
Is full stroke (maximum compression), the inside of the third communication hole 58 becomes a dead volume during control.
The movement of the control piston 56 becomes difficult, and the pressure cannot be adjusted. So, now, about 10MPa, this main spring 53
Need to bend freely, and it is necessary to use the main spring 53 having a very high spring constant.

On the other hand, the stroke A to the seal on the first control piston 56 side needs to have a certain size (for example, 0.5 mm) so that the effect of the normal brake is not delayed. Here, when the lowest break point pressure is generated, the pressure is introduced into the third communication hole 58 at 0 MPa, but even at this time, as described above, the main spring 53 having a very high spring constant is set to 0.5 mm. The pressure at the time of bending becomes the minimum breaking point pressure. In other words, since the spring constant is very high, 0.5 m
Since a certain amount of pressure is required just to bend the m, it is difficult to greatly reduce the minimum breaking point pressure.

Therefore, in this embodiment, the auxiliary spring 57 is arranged, and the stroke A is set to, for example, 0.5 mm, and the stroke B is set to, for example, 0.4 mm.
3 was reduced to 0.1 mm, and the initial 0.3 mm.
By using the auxiliary spring 57 with a small spring constant,
It has become possible to reduce the minimum breaking point pressure by reducing the load increase to the stroke.

FIG. 12 shows this state. In this embodiment, it can be seen that the load (that is, the break point pressure) can be set extremely low with respect to the stroke of the first control piston 56. (Embodiment 3) Next, Embodiment 3 will be described, but the description of the same parts as in Embodiment 1 will be omitted or simplified.

In this embodiment, the differential pressure control valve can be made smaller than in the first embodiment, and therefore, the structure of the differential pressure control valve is different. As shown in FIG. 13, a differential pressure control valve 61 used in the vehicle brake device of the present embodiment is provided with a small-diameter rod portion 64 protruding to the left side in the drawing on a distal end surface of a distal end portion 63 of a first control piston 62. It has.

The rod portion 64 slides in a sliding hole 66 formed in the main body of the differential pressure control valve 61 while being sealed by a seal portion 67. Thereby, the first
The force for pressing the control piston 62 to the right in the figure is smaller than that of the first embodiment, PM × (S1−S4), and the force for pressing the first control piston 62 to the left in the figure is:
PW (S1-S2).

Here, S1 to S4 are the sectional areas of the illustrated portions,
PM, PW, and PP in the figure are first to third communication holes 65, respectively.
a, 65b, 65c brake fluid pressure. That is, the relationship between the forces acting on the first control piston 62 at the break point is PM ×
(S1−S4) −PW × (S1−S2) = spring force, and if PM = PW, (PM × S2) − (PM × S
4) = Spring force.

That is, when the same break point pressure is set as in the first embodiment, in the third embodiment, the spring force is set to (PM
−S4). Therefore, the main spring 68 can be reduced in size, whereby the differential pressure control valve 61 can also be reduced in size.

(Embodiment 4) Next, Embodiment 4 will be described, but the description of the same parts as in Embodiment 1 will be omitted or simplified. This embodiment is different from the first embodiment in the structure of the differential pressure control valve.

As shown in FIG. 14, the differential pressure control valve 71 used in the vehicle brake device of this embodiment is
The first control piston 73 and the second control piston 74 are in direct contact with each other on the left side of the first dish-shaped member 72 in the drawing. In addition, a third communication hole 76 that communicates with a not-shown shut-off valve communicates between the first control piston 73 and the second control piston 74.

Next, the operation of the differential pressure control valve 71 will be described with reference to FIG.
5 will be described. With the pump motor (not shown) and the shut-off valve turned off,
When the brake pedal is not depressed, neither the master cylinder pressure nor the wheel cylinder pressure is generated.

Therefore, in this case, as shown in FIG. 15A, the urging force of the main spring 77 causes the first plate-shaped member 7
2 is pressed and seated on the first wall 78. Next, when the brake pedal is depressed while the pump motor and the shut-off valve are off, both the master cylinder pressure and the wheel cylinder pressure increase.

Therefore, in this case, as shown in FIG. 15 (b), the master cylinder pressure which has risen through the third communication hole 76 is introduced, so that the second control piston 74 moves to the right side of the drawing. Being urged, the first dish-shaped member 72 moves in the same direction. As a result, the main spring 77 is in a compressed state, and the set load of the main spring 77 is substantially increased. As a result, the break point pressure increases.

Next, a case where the pump is driven in a state where the shut-off valve is turned on and high-pressure brake fluid is sealed in the third communication hole 76 will be described. First, when the shutoff valve is turned on, high pressure (PP) brake fluid is sealed in the third communication hole 76, and the break point pressure is high.

Here, when the pump is driven to increase the wheel cylinder pressure, the first control piston 73 moves rightward in the figure due to the pressure balance of the first control piston 73, as shown in FIG. I do. In this state, as shown in FIG. 6, the master cylinder pressure (PM) and the wheel cylinder pressure (PW) change according to the differential pressure characteristic at which the break point pressure increases.

In this way, in this embodiment as well, as in the first embodiment, the breaking point pressure can be freely changed. Particularly, in the present embodiment, by adopting such a structure, there is an advantage that the number of parts is reduced as compared with the first embodiment.

(Embodiment 5) Next, Embodiment 5 will be described, but the description of the same parts as in Embodiment 1 will be omitted or simplified. In this embodiment, a differential pressure control valve similar to that of the first embodiment is applied to a vehicle brake device different from that of the first embodiment to reduce the wheel cylinder pressure on the rear wheel side from the wheel cylinder pressure on the front wheel side. It is made possible.

As shown in FIG. 16, in the vehicle brake device of this embodiment, the pipe 8 branched from the pipe 83 extending from the master cylinder 81 to the wheel cylinder 82 on the front wheel side.
4 communicates with the second communication passage 87 of the differential pressure control valve 86 having the same structure as in the first embodiment, and also communicates with the third communication passage 89 via the shutoff valve 88 as in the first embodiment. I have.
Further, the first communication passage 91 is provided with the wheel cylinder 9 on the rear wheel side.
It communicates with 2.

Next, the operation of the vehicle brake device will be described. For example, when the rear wheels tend to lock before the front wheels,
By adjusting the timing of driving the shutoff valve 88, it is possible to approach the optimal braking force distribution regardless of the loaded state.

That is, while the master cylinder pressure is transmitted to the front wheel side as it is, the relationship between the wheel cylinder pressure on the rear wheel side and the master cylinder pressure is determined by the drive timing of the shut-off valve 88 so as to be sealed in the third communication hole 89. It can be determined by pressure. For example, as shown in FIG. 17, when the load amount is large, the containment pressure is reduced to set the wheel cylinder pressure on the rear wheel to a lower value. Conversely, when the load amount is small, the containment pressure is increased to increase the rear wheel pressure. Set the side wheel cylinder pressure higher. As a result, the tendency of locking on the rear wheel side can be reduced, and optimal braking force distribution can be realized.

Further, a break point pressure for optimal braking force distribution is calculated based on information from a load sensor and the like (see FIG. 10), and when the master cylinder pressure reaches the break point pressure,
By closing the shutoff valve 88, an optimal braking force distribution can be realized. It is needless to say that the present invention is not limited to the above-described embodiments, and can be implemented in various modes without departing from the technical scope of the present invention.

In the drawings used for the description of the above-described embodiment, hatching of a cross section is partially omitted for clarity of the description.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a vehicle brake device according to a first embodiment.

FIG. 2 is a block diagram illustrating an electrical configuration of the first embodiment.

FIG. 3 is an explanatory diagram illustrating a differential pressure control valve used in the first embodiment.

FIG. 4 is an explanatory diagram showing an operation of the differential pressure control valve according to the first embodiment at the time of low pressure cut.

FIG. 5 is an explanatory diagram illustrating an operation of the differential pressure control valve according to the first embodiment at the time of high pressure cut.

FIG. 6 is a graph showing the relationship between the M / C pressure and the W / C pressure according to the first embodiment.

FIG. 7 is a flowchart illustrating pressure amplification assist brake control according to the first embodiment.

FIG. 8 is a flowchart illustrating control when the brake booster of the first embodiment fails.

FIG. 9 is a flowchart illustrating control of braking force distribution according to the first embodiment.

FIG. 10 is a graph showing the relationship between weight and break point pressure in controlling braking force distribution according to the first embodiment.

FIG. 11 is an explanatory view showing a differential pressure control valve used in a second embodiment.

FIG. 12 is a graph showing characteristics of the differential pressure control valve according to the second embodiment.

FIG. 13 is an explanatory diagram illustrating a differential pressure control valve used in a third embodiment.

FIG. 14 is an explanatory diagram illustrating a differential pressure control valve used in a fourth embodiment.

FIG. 15 is an explanatory diagram illustrating the operation of the differential pressure control valve according to the fourth embodiment.

FIG. 16 is a schematic configuration diagram illustrating a vehicle brake device according to a fifth embodiment.

FIG. 17 is a graph showing the relationship between M / M by the vehicle brake device of the fifth embodiment.
It is a graph which shows the relationship between C pressure and W / C pressure.

[Explanation of symbols]

 1,81 master cylinder 2,82,92 wheel cylinder 4,51,61,71,86 differential pressure control valve 6,65a, 91 first communication hole 7,65b, 87 second communication hole 9 Pump 12, 58, 65c, 76, 89 Third communication hole 13, 88 Control valve (shutoff valve) 16 Brake booster 42, 56, 62, 73 First control piston 43, 74 Second control piston 44 , 53, 68, 77 ... main spring 57 ... auxiliary spring

Claims (13)

[Claims] A brake fluid pressure generating means for generating a brake fluid pressure during vehicle braking; a wheel braking force generating means for receiving a brake fluid pressure from the brake fluid pressure generating device to generate a wheel braking force; A differential pressure is generated between the brake fluid pressure generating means and the wheel braking force generating means by introducing the brake fluid pressure on the fluid pressure generating means side and the brake fluid pressure on the wheel braking force generating means side. A differential pressure control valve, comprising: an introduction path for introducing pilot pressure to the differential pressure control valve; and a control valve for communicating and shutting off the introduction path. The differential pressure characteristic of the differential pressure control valve is made variable by the pilot pressure when the introduction path is interrupted. 2. A brake fluid pressure generating means for generating a brake fluid pressure during vehicle braking, a wheel braking force generating means for receiving a brake fluid pressure from the brake fluid pressure generating device and generating a wheel braking force, and the brake Suction the brake fluid from the hydraulic pressure generation means side,
A pump that discharges to the wheel braking force generating means side, and a brake fluid pressure on the brake fluid pressure generating means side and a brake fluid pressure on the wheel braking force generating means side are introduced,
A differential pressure control valve for generating a differential pressure between the brake fluid pressure generating means and the wheel braking force generating means when the brake fluid is moved by the pump. The brake device, comprising: an introduction path for introducing a pilot pressure to the differential pressure control valve; and a control valve for communicating / cutting off the introduction path. The pilot pressure when the introduction path is shut off by the control valve. Wherein the differential pressure characteristic of the differential pressure control valve is made variable. 3. The vehicle brake device according to claim 1, wherein the pilot pressure is a brake fluid pressure of the brake fluid pressure generating means. 4. The vehicle brake device according to claim 1, wherein the differential pressure control valve has a valve mechanism including a first valve body having a pressure receiving area difference. 5. The valve mechanism includes the first valve body and the second valve body urged in a separating direction by a spring, and a tip side of the first valve body is on a side of the brake fluid pressure generating means. And the side of the first valve body is connected to the pump side and brakes in a direction to separate the spring. A hydraulic pressure is set, and a rear end side of the second valve body in a direction opposite to the first valve body communicates with the brake hydraulic pressure generation means side via an introduction path in which the control valve is disposed. The vehicle brake device according to claim 4, wherein the brake fluid pressure is set so as to be applied in a direction to compress the spring. 6. The first valve body according to claim 4, wherein a narrow portion protruding in the axial direction is provided from a distal end side of the first valve body, and the first valve body is sealed by the narrow portion. The vehicle brake device according to any one of the preceding claims. 7. The vehicle brake device according to claim 4, further comprising an auxiliary spring for urging the first valve body toward the distal end. 8. By driving the pump and the control valve according to a depression state of a brake pedal,
The vehicle brake device according to any one of claims 2 to 7, wherein a brake fluid pressure applied to the wheel braking force generating means is adjusted. 9. When it is determined based on the negative pressure introduced into the brake booster that the brake booster has failed, the pump and the control valve are driven to generate the wheel braking force. The vehicle brake device according to any one of claims 2 to 7, wherein a brake fluid pressure applied to the means is adjusted. 10. When it is determined that the upper limit of the boosting action of the brake booster has been reached based on the state of the brake fluid pressure of the brake fluid pressure generating means or the state of the negative pressure introduced into the brake booster, 3. The brake fluid pressure applied to the wheel braking force generating means is adjusted by driving the pump and the control valve.
The vehicle brake device according to any one of claims 1 to 7. 11. The wheel according to claim 11, wherein the wheel is driven by driving the pump and the control valve in accordance with a load applied to the vehicle and a brake fluid pressure of the brake fluid pressure generating means. The vehicle brake device according to any one of claims 2 to 7, wherein a brake fluid pressure applied to the braking force generating means is adjusted. 12. A brake fluid pressure applied to the wheel braking force generating means is adjusted by driving the pump and the control valve according to a steering angle and a yaw rate when the vehicle turns. The vehicle brake device according to any one of claims 2 to 7. 13. A brake fluid pressure generating means for generating a first brake fluid pressure during vehicle braking, and a wheel braking force for generating a wheel braking force in response to the first brake fluid pressure from the brake fluid pressure generating means. Generating means; a pump for sucking the brake fluid as the first brake fluid pressure from the brake fluid pressure generating means side and discharging the brake fluid to the wheel braking force generating means side; Is performed, a differential pressure of the brake fluid between the brake fluid pressure generating means side and the wheel braking force generating means side can be generated when the first brake fluid pressure is equal to or higher than a predetermined pressure. A differential pressure control valve, an introduction path provided in the differential pressure control valve and connecting the pressure accumulating chamber for introducing the brake fluid of the first brake fluid pressure with the brake fluid generating means, And a control valve for communicating and shutting off The differential pressure control valve reduces a pressure decay when the brake fluid flows from the wheel braking force generating means to the brake fluid pressure generating means in accordance with a state of introduction of the brake fluid into the pressure accumulating chamber. A brake device for a vehicle, wherein the predetermined pressure as a threshold value to be performed is changed.