JPH10297466A - Brake servo assist device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a car brake servo asist device being excellent in a brake feeling, capable of preventing such a fear that boost starting pressure becomes increased in time of the initial stage of braking operations. SOLUTION: In a car brake servo unit equipped with a control valve 3 being feedable to a wheel cylinder as controlling hydraulic pressure in a hydraulic pressure source after moving a spool piston 22 by dint of the hydraulic pressure produced by a master cylinder, a flow absorbing piston 23 is set up in opposition to the spool piston 22 set up in the said control valve 3, and this flow absorbing piston 23 is moved according to an amount of travel of the spool piston 22, and thereby the generation of any hydraulic pressure due to a movement of the spool piston 22 is checked.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle brake booster and, more particularly, to a vehicle brake booster having a good brake feeling which can prevent a boost start pressure from increasing at an early stage of a brake operation. It concerns the device.

[0002]

2. Description of the Related Art Conventionally, as a mechanism for increasing the pedal effort of a brake pedal, a vehicle brake booster as disclosed in Japanese Patent Publication No. 51788/1990 is well known. The vehicle brake booster described in the above publication will be described with reference to FIG. 5. The brake booster is composed of two systems, in which 101 is a brake pedal, 102 is a master cylinder, and 103 is a brake pedal. A hydraulic pressure absorbing device 104 for improving the feeling of stepping-in, a pressure adjusting valve 104,
5 is a switching valve, 106 is an accumulator as a hydraulic pressure source,
Reference numeral 107 denotes an antilock control device including a hold valve, a decay valve, and the like. When the brake pedal is depressed, a hydraulic pressure is generated in the master cylinder 102, and the hydraulic pressure is applied to the spool of the pressure adjusting valve 104. By moving the piston 108 to the left in the figure, the flow rate a and the flow path b are communicated, and the switching valve 1 is switched by the hydraulic pressure from the accumulator 106.
The brake operation can be performed via the switch 05. When the wheels tend to lock during the braking operation, a hold valve in the antilock control device 107
A decay valve opens and closes to control brake fluid pressure to avoid wheel locking tendency.

[0003]

However, in the above-described brake booster for a vehicle, when the brake pedal is depressed, the pressure adjusting valve 104 is actuated by the hydraulic pressure generated in the master cylinder.
When the spool piston 108 in the inside moves, the flow path b corresponds to the spool piston movement (volume of the spool piston).
(I.e., the hydraulic pressure on the wheel cylinder side) increases (i.e., with the movement of the spool piston, the volume on the side of the flow path b decreases correspondingly and the pressure increases). There is a problem that the hydraulic pressure at the time increases by this amount, and the brake feeling deteriorates.

In view of the above, the present invention provides a brake booster for a vehicle, which comprises a flow rate absorbing piston capable of absorbing a flow rate corresponding to a moving amount of the spool piston when the spool piston moves within the pressure regulating valve (hereinafter referred to as a control valve). A control valve is provided which prevents the boost start pressure from increasing at the initial stage of depressing the brake pedal by using the piston, thereby solving the above-mentioned problem.

According to the present invention, when the spool piston is moved by the hydraulic pressure generated in the master cylinder during the braking operation, the flow absorbing piston is moved by using the hydraulic pressure from the accumulator to reduce the amount of movement of the spool piston. A corresponding flow rate can be absorbed, so that the hydraulic pressure in the boost chamber can be kept at an extremely low pressure at the time of the initial operation of the spool piston, so that a quick boost operation can be started from a low hydraulic pressure state.

[0006]

For this reason, the technical solution adopted by the present invention is to supply a wheel cylinder while controlling the hydraulic pressure of a hydraulic pressure source by moving a spool piston by hydraulic pressure generated in a master cylinder. In a vehicle brake booster provided with a control valve capable of being provided, a flow absorbing piston is disposed opposite to a spool piston disposed in the control valve, and the flow absorbing piston moves according to a moving amount of the spool piston. A vehicle brake booster characterized in that generation of hydraulic pressure due to initial movement of a spool piston is suppressed.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of the brake booster, FIG. 2 is an enlarged sectional view of a control valve, and FIG. FIG. 4 is an enlarged sectional view of a pump used in the booster. Hereinafter, after describing the overall configuration of the brake booster, the components such as the control valve, the hydraulic pressure transmission device, and the pump will be described in detail.

In FIG. 1, 1 is a brake pedal, 2 is a tandem master cylinder, 3 is a control valve,
4 is a front wheel side hydraulic pressure transmitting device, 5 is a rear wheel side hydraulic pressure transmitting device, 6
Is a pump, 7 is a front wheel cylinder, 8 is a rear wheel cylinder, 9 is a hold valve, 10 is a decay valve, 11 is an anti-lock reservoir, 12 is a proportioning valve, 13 is an accumulator, and 14 is a normally closed first. A switching valve, 15 is a normally-closed second switching valve, 16 is a normally-opening third switching valve, 17 is a pressure sensor, 18 is a relief valve, and 19 is a reservoir. Have been.

In this brake booster, when the brake pedal 1 is operated and a fluid pressure (hydraulic pressure) is generated in the tandem master cylinder 2, the control valve 3 is actuated by this fluid pressure, and the hydraulic pressure of the master cylinder is reduced. The hydraulic pressure proportionally increased is transmitted from the output port 144 of the control valve 3 to the hydraulic pressure transmitting devices 4 and 5. The hydraulic pressure generated by the hydraulic pressure transmission devices 4 and 5 is supplied to the wheel cylinders 7 and 8 and a brake is applied. Further, if a possibility of locking of the wheel occurs during the braking operation, the hold valve 9 and the decay valve 10 are opened and closed by an output signal from an electronic control unit (not shown) according to a signal from a wheel speed sensor (not shown). The pressure fluid in the cylinders 7 and 8 is discharged to the anti-lock reservoir 11, and the pressure fluid in the wheel cylinders 7 and 8 is controlled by pumping the pressure fluid from the anti-lock reservoir 11 by the pump 6 that operates at the same time. Execute antilock control. When the pump 6 is operated, a booster pump (detailed configuration will be described later) incorporated in the pump is also operated, and the booster pump draws up a pressure fluid from the hydraulic pressure transmission devices 4 and 5 and accumulators 13.
To accumulate pressure.

That is, in the present brake booster, while the kickback occurs on the master cylinder side during the antilock control, the wheel cylinder is depressurized while consuming the hydraulic pressure of the accumulator. Since the accumulator can accumulate pressure while pumping the pressure fluid from the hydraulic pressure transmission device side, the pressure fluid in the wheel cylinder is once discharged to the atmospheric pressure reservoir and pumped again from the atmospheric pressure reservoir as in the past. As a result, the load on the pump can be reduced as compared with a configuration in which the pressurized fluid is pumped up and accumulated in the accumulator.

Hereinafter, main components constituting the brake booster will be described in detail. [Control Valve 3] In FIG. 2, the control valve 3 includes a balance piston 20, a diaphragm piston 21, a spool piston 22, and a flow absorption piston 23 in a main body 3A in an arrangement shown in the drawing, and each piston is provided in the main body. It is slidably disposed in the formed first cylinder 24, second cylinder 34, and third cylinder 40. The diameter of each cylinder is as follows: first cylinder> second cylinder> third cylinder.

The balance piston 20 includes a first cylinder 24
Is formed as a stepped piston having a large diameter portion 20a and a small diameter portion 20b. The first liquid chamber 25, the second liquid chamber 26, and the third liquid chamber are formed in the first cylinder 24. 27. The first hydraulic chamber 25 of the control valve 3 is connected to the first hydraulic pressure generating chamber 2a of the tandem master cylinder 2 via the first input port 28, and the rear wheel side hydraulic pressure transmitting device 5 via the first output port 29. The second liquid chamber 26 in the valve 3 is connected to a third input port 32.
The third liquid chamber 27 communicates with the third switching valve 16 and the second switching valve 15 through the second input port 3.
0 and the second hydraulic pressure generating chamber 2b of the tandem master cylinder 2 and the second output port 31 to the front wheel side hydraulic pressure transmitting device 4. The balance piston 20 is normally urged rightward in the figure by a spring 33 disposed in the third liquid chamber 27.

A diaphragm piston 21 disposed opposite to the balance piston 20 is slidably provided in a second cylinder 34 formed in the main body, and is formed as a stepped piston having a large diameter portion 21a and a small diameter portion 21b. The diaphragm 35 is provided on the end surface of the large diameter portion, and is partitioned from the third liquid chamber 27 by the diaphragm 35 in a liquid-tight manner. On the end face of the small diameter portion 21b of the diaphragm piston 21 is formed an engagement protrusion 36 which is in contact with the spool piston 22, and a groove 37 is formed around the small diameter portion of the diaphragm piston 21. The groove 37 and the liquid chamber 39 on the small-diameter end face side partitioned in the second cylinder by the diaphragm piston 21 are communicated with the reservoir 19 by a passage 38 in the cylinder body.

The engagement projection 36 of the diaphragm piston 21
The spool piston 22 which is in contact with the spool piston is slidably disposed in the third cylinder 40 in the main body, and a flow path 41 is formed in the center of the spool piston. Communicating. This groove 4
2 communicates with the reservoir 19 through a passage 38 in the main body when not in operation, and is connected to the accumulator 13 through a passage 44 in the main body when the spool piston 22 moves leftward from the state shown in the drawing (that is, when it is activated). Communicate. The width of the groove 42 is set slightly smaller than the distance L between the passage 38 and the passage 44 formed in the main body, so that the flow passage 41 at the center of the spool piston 22 is
When the spool piston moves from the state communicating with the main body and the flow path 41 switches to the state communicating with the passage 44 on the main body side, a slight time lag occurs. Also,
The second switching valve 15 communicates with a second liquid chamber 26 formed at the step of the balance piston 20 as shown in FIG.

The flow passage 41 at the center of the spool piston 22 has a middle portion slidably formed in a third cylinder 40 and a seal 1.
47 communicates with a flow passage 45 formed in the flow absorption piston 23 which is maintained in a liquid-tight manner.
The third flow path 45 communicates through a hole 46 with a boost chamber 142 formed at an intermediate portion in the third cylinder 40. The boost chamber 142 is connected to the first switching valve 14 via an output port 144 as shown in the figure, and is directly connected to the front-wheel-side hydraulic pressure transmitting device 4 and to the rear-wheel-side hydraulic pressure transmitting device 5, for example. 58-57333. The flow rate absorbing piston 23 is urged toward the spool piston 22 by a flow rate absorbing spring 43 disposed around the piston 23, and both are in contact in the boost chamber 142, and the spool piston 22 The positioning is performed by the main body 3A on the right end face in the figure by the urging force. The periphery of the flow rate absorbing spring 43 is communicated with the reservoir 19 and the front and rear wheel side hydraulic pressure transmitting devices 4 and 5 by a passage 146 in the main body.
The left end of the flow rate absorption piston 23 is arranged in the main body with a margin to move leftward in the figure.

Therefore, when the control valve 3 is not operated, the boost chamber 1 formed in the main body 3A is not operated.
Reference numeral 42 denotes a hole 46 of the flow absorption piston 23 → a flow path 45 of the flow absorption piston 23 → a central flow path 41 of the spool piston 22 → a groove 42 of the spool piston 22 → communicate with the reservoir 19 via a passage 38 on the main body side. And is isolated from the accumulator 13. When the brake is actuated, hydraulic pressure is generated in the tandem master cylinder 2 and the hydraulic pressure in the first hydraulic chamber 25 and the third hydraulic chamber 27 in the control valve 3 rises. The piston 20 does not move. The third liquid chamber 27
The diaphragm piston 21 moves to the left in the drawing by the hydraulic pressure, and the spool piston 22 moves to the left in the drawing. As a result, the groove 42 of the spool piston 22 is
, The pressure fluid from the accumulator 13 flows into the boost chamber 142 via the flow path 41, and further flows into the hydraulic pressure transmission device described later. The boost chamber 142 acting on the left end of the spool piston 22
When the spool piston 22 moves left and right so that the fluid pressure due to the fluid pressure in the inside and the fluid pressure due to the master cylinder fluid pressure acting on the right end of the diaphragm piston 21 are balanced, the fluid pressure in the boost chamber 142 becomes the master cylinder fluid. It is increased (boosted) in proportion to the pressure. The boost ratio is determined by the ratio of the area of the left end of the spool piston 22 to the area of the right end of the diaphragm piston 21.

During the operation of the brake, the spool piston 22 is moved by the pressing force from the diaphragm piston 21 and the pressure fluid from the accumulator 13 is released from the boost chamber 1.
Immediately after flowing into the spool 42, the flow absorbing piston 23 bends the flow absorbing spring 43 and moves to the left in the drawing, thereby absorbing the liquid amount corresponding to the moving amount of the spool piston 22. At the time of the initial operation of the spool piston 22, the boost chamber 142 is maintained at an extremely low pressure, so that a quick boost action can be started from a low hydraulic pressure state.

[Hydraulic pressure transmitting devices 4 and 5]
Since the front wheel side 5 and the rear wheel side 5 have the same structure and function, the rear wheel side hydraulic pressure transmitting device 5 will be described here with reference to FIG. In FIG. 3, the hydraulic pressure transmitting device
A piston 51, a second piston 52, and a third piston 53 are slidably provided in the main body 50 in the arrangement shown in FIG.
The pressure receiving area of the piston 51 is L, and the first area of the second piston 52 is
The pressure receiving area of the small diameter portion on the side of the piston 51 is J ′, the pressure receiving area of the large diameter portion of the second piston 52 is M, and the pressure receiving area of the second piston 52 is the third.
The pressure receiving area on the side of the piston 53 is formed as J, and among the pressure receiving areas, the pressure receiving areas J ′ and J of the second piston 52 and the respective pressure receiving areas M, L and J are set as J ′ = J M>L> J. .

At the lower central portion of the first piston 51 in the drawing,
The small diameter portion of the second piston 52 is slidably fitted,
The first piston 51 is urged downward by a first spring 54 disposed in the main body 50 so as to be in contact with a stopper 55 in the cylinder. First piston 51
A second spring 57 is interposed between the first piston 52 and the second piston 52 through a cylindrical spring seat 56.
Are urged downward in the figure by the urging force of the second spring 57. A gap S is formed between the first piston 51 and the second piston 52, and the gap S is formed by the cut valve 59 (described in detail later) when the brake is operated.
After the communication between the pressure chamber 61 and the pressure chamber 61 is interrupted, the gap S becomes zero.

The pressurizing chamber 61 partitioned by the first piston 51 is connected to the rear wheel-side wheel cylinder 8 via an output port 62 and a hold valve 9 formed in the main body, and via a cut valve 59. Body 50
Is connected to the flow path 60. The flow path 60 communicates with the first hydraulic pressure generation chamber 2 a of the tandem master cylinder 2 via the first output port 29 of the control valve 3 and an input liquid chamber 63 described later that is partitioned by a third piston 53. Is communicated to. The cut valve 59 is urged upward in the figure by a third spring 64 provided in the pressurizing chamber 61, and the lower shaft end of the cut valve 59 is connected to a cylindrical spring seat 56 provided on the second piston 52 side. It is slidably engaged, and communication between the flow path 60 and the pressurizing chamber 61 is maintained when not operating.

A liquid chamber 65 is defined in the main body 50 between the first piston 51 and the second piston 52, and this liquid chamber 65 is connected to the reservoir 19 via the control valve 3. The pressure introduction chamber 66 partitioned in the main body by the large diameter portion of the second piston 52 communicates with the boost chamber 142 of the control valve 3 via the proportioning valve 12. The pressure introduction chamber 66 of the front wheel side hydraulic pressure transmitting device 4 is directly connected to the control valve 3.
Is connected to the boost chamber 142. Third piston 53
Is slidably fitted to the center of the second piston,
In the illustrated state, the urging force of the second spring 57 urges the lower portion of the drawing through the second piston 52, and
The end face of the piston 53 abuts on a cylinder end face 58 formed on the main body 50, and defines an input liquid chamber 63 between the cylinder end face and the end face of the third piston 53. The input liquid chamber 63 communicates with the first hydraulic pressure generation chamber 2 a of the tandem master cylinder 2 and the flow path 60 via the first output port 29 of the control valve 3.

When the hydraulic pressure transmitting device 5 is not operated, the cut valve 59 maintains the illustrated state, and the flow path 60 is open. When the brake pedal is actuated and the diaphragm piston 21 of the control valve 3 moves due to the fluid pressure in the third fluid chamber 27 by the tandem master cylinder and the flow path is switched, the pressure fluid in the accumulator 13 is released by the main body 3A of the control valve 3. Passage 44 → spool piston 22
Flows into the pressure introduction chamber 66 via the flow path 41 → the boost chamber 142 → the output port 144 → the proportioning valve 12 to move the second piston 52 upward in the figure between the gaps S. The movement during the gap S causes the cut valve 59 to close the channel 60 first, and then the second piston 52 comes into contact with the first piston 51, and the first piston 51 moves upward. On the other hand, the third piston 53 moves upward while maintaining the contact state with the second piston 52 by the hydraulic pressure of the first hydraulic pressure generation chamber 2 a of the tandem master cylinder that has flowed into the input liquid chamber 63. As a result, the first piston 51 is acted upon by the control valve 3 to increase the hydraulic pressure of the master cylinder and the hydraulic pressure of the master cylinder, and the pressurized fluid in the pressurizing chamber 61 is released via the hold valve 9. The brake is supplied to the wheel cylinder 8 on the wheel side to operate the brake. Also, the pressure fluid in the pressurized chamber on the front wheel side hydraulic pressure transmission device 4 side is similarly supplied to the front wheel side wheel cylinder 7 to operate the brake. Supplying a large amount of brake fluid to the wheel cylinder by increasing the boost ratio of the control valve 3 and increasing the pressure receiving area of the first piston 51 to the wheel cylinder. Can be.

Since the pressure-receiving areas J 'and J of the small-diameter portion provided across the large-diameter portion of the second piston 52 are equal, the cut valve 59 is provided in the initial stage of the brake operation.
Until the valve closes the flow path 60, there is no change in the flow rate of the brake pipe diameter, and the uncomfortable feeling when the brake pedal is depressed can be eliminated. In the early stage of the braking operation, the hydraulic pressure generated by the tandem master cylinder is also transmitted to the flow path 60 of the hydraulic pressure transmitting device 5 through the first output port 29 of the control valve 3. Since the cut valve 59 is closed as described above, the communication between the tandem master cylinder and the wheel cylinder is cut off.

In the present hydraulic pressure transmitting device, when the pressurized fluid from the accumulator 13 is not supplied for some reason and the boosting function is not performed (during a failure), the second and third pistons 52 and 53 move. Therefore, the pressure fluid generated in the tandem master cylinder is not supplied to the first output port 29 of the control valve 3 → the main body passage 60 of the hydraulic pressure transmission device 5 →
It is directly transmitted to the open cut valve 59 → the pressurizing chamber 61 → the output port 62 → the wheel cylinder 8 to perform the braking action. Since the diameter of the hydraulic piston (not shown) of the tandem master cylinder 2 is set relatively small and the boost ratio is set large as described above,
During a failure, the hydraulic pressure generated by the hydraulic piston having a small diameter of the master cylinder can be increased, and a sufficient braking force can be ensured. Further, in the present hydraulic pressure transmitting device, the second piston 52 and the first piston 51 move upward in the drawing by the pressure fluid introduced into the pressure introduction chamber 66 during automatic braking (traction control or yaw moment control, etc.). And the brakes can work. If the second and third pistons 52 and 53 are formed integrally, the volume of the input liquid chamber 63 increases when the automatic brake is activated, and the pressure in the input liquid chamber 63 and the piping system connected to it temporarily. May become negative pressure and air may flow into the input liquid chamber 63 or the like. However, in this transmission, the second and third pistons 52 and 53 are formed separately so as to be relatively movable with each other. No more hydraulic pressure is acting,
The piston 53 does not move upward in the drawing, and no negative pressure is generated in the input liquid chamber 63 or the like as described above.

[Pump 6] This pump 6 is characterized in that a booster pump 73 for pumping a pressure fluid from the hydraulic pressure transmitting device side during antilock control is added to the conventional antilock control pumps 71 and 72. . In FIG. 4, the pump 6 includes two anti-lock control pumps 71,
72 and one booster pump 73 for pumping a pressure fluid from the hydraulic pressure transmitting device. The plungers 71a and 72a of the anti-lock control pump are symmetrically arranged with respect to a common cam 74, and The plunger 73a of the booster pump is in axial contact with the plungers 71a and 72a (FIG. 4).
) Is in contact with a cam 74a separate from the cam 74 of the anti-lock control pump. When the cams 74, 74a are rotated by motors (not shown), the respective plungers 71a, 72a, 73a reciprocate by the cams, and open and close ball valves to perform a pumping operation. The discharge port 73 b of the booster pump 73 is connected to the accumulator 13, and the first suction port 73 c is connected to the reservoir 19.
The second suction port 73d is connected to the first switching valve 14, respectively. Since the pump structure itself is well known in the art, detailed description will be omitted.

In this pump, the pressure receiving area D of the plunger 73a of the booster pump 73 is equal to the respective plungers 71a, 72a of the antilock control pumps 71, 72.
The pressure receiving areas E and E ′ are set to have the following relationship. D ≧ E + E ′ This is because the booster pump 7
This is to ensure a sufficient pump capacity so that the pressure fluid does not flow out of the boost chamber 142 to the reservoir when the pressure fluid is pumped from the pressure introduction chamber 66 of each of the hydraulic pressure transmission devices 4 and 5 by 3. That is, the discharge amount of the anti-lock control pumps 71 and 72 is
If the suction amount is larger than 3, the pressure fluid in the boost chamber 142 will push back the spool piston 22 and flow out to the reservoir, so that such a state must be avoided.

[Wheel Cylinder, Decay Valve and Hold Valve] The control valve device including the decay valve 9 and the hold valve 10 has the same configuration as the conventional recirculation type anti-lock control device. This is performed according to a command from an electronic control unit (not shown). The hold valve 9 and the decay valve 10 are opened and closed not only during the antilock control but also during the automatic braking such as the traction control and the yaw moment control by the command from the electronic control device as described in the operation section described later. And adjust the brake pressure.

The operation of the brake booster configured as described above will be described. [Non-operation] When the driver does not step on the brake pedal 1 and no hydraulic pressure is generated in the tandem master cylinder 2, the first and third fluid chambers 25, 2 in the control valve 3
Since no hydraulic pressure is generated in the control valve 7, the control valve 3 does not operate and the state of FIG. 2 is maintained. As a result, the pressure fluid from the accumulator 13 is shut off by the spool piston 22 in the control valve 3, and the input fluid chamber 63 and the pressure introduction chamber 66 of the fluid pressure transmission device are pressureless, so that the pressure fluid is supplied to the wheel cylinder. Does not generate hydraulic pressure.

[Operation] When the driver steps on the brake pedal 1 and generates hydraulic pressure in the tandem master cylinder 2, the hydraulic pressure in the second hydraulic pressure generation chamber 2 b passes through the second input port 30 of the control valve 3. And acts on the diaphragm 35 in the control valve 3, and through the second output port 31, the input fluid chamber 6 of the front wheel side hydraulic pressure transmitting device 4.
3 is transmitted. On the other hand, the fluid pressure in the first fluid pressure generation chamber 2 a of the tandem master cylinder 2 is transmitted to the first fluid chamber 25 of the control valve 3 and the input fluid chamber 63 of the fluid pressure transmission device 5. When hydraulic pressure acts on the diaphragm piston 21 in the control valve 3, the piston 21 moves to the left in FIG. 2, and the spool piston 22 also moves to the left in the figure. At this time, the spool piston 22 enters the boost chamber 142, and the pressure in the boost chamber 142 is increased by the stroke of the spool piston 22,
The control valve 3 is configured such that the flow absorption piston 23 bends the flow absorption spring 43 and moves to the left in the figure to absorb the liquid amount corresponding to the stroke of the spool piston 22. 22
During the initial operation, the boost chamber 142 is maintained at an extremely low pressure, so that a quick boost operation can be started from a low hydraulic pressure state. Further, the third liquid chamber 27 and the reservoir 19 are partitioned by the diaphragm 35, and the sliding resistance of the diaphragm 35 can be reduced as compared with a case where a seal is arranged around the piston, and a hydraulic pressure is generated in the wheel cylinder. When the brake pedal depressing force is reduced.

By further movement of the spool piston 22, the central flow passage 41 in the spool piston 22 communicates with the passage 44 in the main body, the boost chamber 142 in the control valve 3 communicates with the accumulator 13, and the pressure fluid is When introduced into the pressure introduction chambers 66 of the pressure transmitting devices 4 and 5 (introduced into the hydraulic pressure transmitting device 5 via the proportioning valve 12), the second piston 5 in the hydraulic pressure transmitting device
2 moves between the gaps S upward in the figure. By the movement between the gaps S, the cut valve 59 first closes the flow path 60, and then the second piston 52 comes into contact with the first piston 51, and the first piston 51 moves upward to move inside the pressurizing chamber 61. The pressure in the pressurizing chamber 61 is increased,
Is supplied to the front and rear wheel cylinders 8 via
Apply the brake. Then, in this state, in the boost chamber 142, a hydraulic pressure proportional to the hydraulic pressure of the tandem master cylinder acting on the diaphragm piston 21 is generated.

On the other hand, the first and second control valves 3
The master cylinder pressure transmitted from the output ports 29, 31 to the hydraulic pressure transmitting devices 4, 5 acts on the input liquid chamber 63 of the hydraulic pressure transmitting devices 4, 5, and the third piston 53 causes the second piston 52 To rise with. The fluid in the liquid chamber 65 of the hydraulic pressure transmitting devices 4 and 5 is controlled by the control valve 3.
Is discharged to the reservoir 19 via the When the brake is released, the spool piston 22 in the control valve 3 returns to the initial position, and the pressure introduction chamber 6 of the hydraulic pressure transmission device is released.
The pressure fluid of No. 6 is boost chamber 142 → spool piston 2
2 passage 41 → reservoir 19 via passage 38 in the main body
Then, the pressure fluid in the pressurizing chamber 61 is also released, and the brake is released. As described above, when the wheel cylinder is pressurized, the third piston 53 moves upward by the hydraulic pressure of the master cylinder, and the volume of the input liquid chamber 63 increases, so that the liquid discharged from the master cylinder is absorbed. Therefore, as the depression force of the brake pedal is increased, the depression amount of the brake pedal is increased, and a suitable operation feeling can be obtained.

[At the time of anti-lock control] When there is a fear that the wheels may be locked during the brake operation, a signal from a wheel speed sensor (not shown) is used to issue a command from the electronic control unit to the hold valve 9 and the decay as conventionally known. Valve 10,
And the pump 6 is driven to avoid the locked state of the wheels, and the first switching valve 14 is opened to connect the suction port of the booster pump 73 to the boost chamber 14 of the control valve 3.
2 and the pressure introduction chamber 66 of the hydraulic pressure transmission device.

More specifically, when there is a risk of locking the wheels, the hold valve 9 is closed to maintain the wheel cylinder pressure while the decay valve valve 10 is closed, and then the decay valve 10 is opened and the wheel cylinder 8 is opened. , 9 is absorbed by the reservoir 11 to reduce the wheel cylinder pressure. At the time of pressure reduction, the anti-lock control pumps 71 and 72 pump up the pressure fluid flowing from the wheel cylinder into the anti-lock control reservoir 11 and return it to the pressurizing chamber 61 of the hydraulic pressure transmission device. As a result, the first piston 51, the second piston 52, and the third piston 53 retreat, and the pressure introduction chamber 6
The pressure fluid of No. 6 is pumped up by the booster pump 73 and returned to the accumulator 13. When the volume of the input liquid chamber 63 is reduced by the retreat of the third piston 53, the driver can know that kickback has occurred in the master cylinder and the antilock control has been started. Further, during the antilock control, when it is necessary to pressurize, the decay valve closes, the halt valve opens, and the pressure introduction chamber 66 is opened.
And the hydraulic pressure of the input fluid chamber 63, the first piston 5
The first and second pistons 52 and the third piston 53 rise to pressurize the pressurizing chamber 61 to repressurize the wheel cylinder pressure.

The booster pump 73 driven at the same time as the start of the antilock control pumps up the pressure fluid in the pressure introduction chamber 66 of the hydraulic pressure transmitting device via the first switching valve 14 which is kept open during the antilock control. Reflux to the accumulator 13. At this time, the hydraulic pressure in the pressure introducing chamber 66 is always proportional to the hydraulic pressure generated in the master cylinder. In other words, the hydraulic pressure in the pressure introducing chamber 66 acts on the diaphragm piston 21 in the control valve 3. Since a hydraulic pressure proportional to the hydraulic pressure of the master cylinder is generated, the booster pump 73 pumps up the fluid that has increased to a predetermined pressure, and can reduce the load as compared with the case where the fluid in the reservoir is pumped up. In this way, in the brake booster, while the kickback occurs on the master cylinder side during the antilock control, the wheel cylinder is pressurized while the hydraulic pressure of the accumulator 13 is consumed, while the booster pump 73 is driven by the hydraulic pump. The pressure of the accumulator 13 can be increased by pumping the pressure fluid from the transmission device side, so that the load on the booster pump 73 can be reduced.

[Automatic Brake] When slippage occurs in the wheels when the vehicle starts, or when the brake is automatically applied due to the approach of the inter-vehicle distance, furthermore, in order to secure the stability of the vehicle body during turning, the yaw moment or the like is determined. When executing the automatic brake control, an appropriate braking force is applied to the wheels to execute control for avoiding such a situation. In the present brake fluid pressure control device, when any of these conditions occurs, the electronic control device opens the normally closed second switching valve 15 by a signal from a sensor (not shown) (wheel speed sensor, headway distance sensor, etc.). At the same time, the normally open third switching valve 16 is closed.

As a result, the pressure fluid in the accumulator 13 flows through the second switching valve 15 to the control valve 3.
Into the second liquid chamber 26 and moves the balance piston 20 to the left in the figure. Due to the movement of the balance piston 20, the diaphragm piston 21 also moves while being pushed by the balance piston 20, and moves the spool piston 22 to the left in the figure, and communicates the accumulator 13 and the boost chamber 142, similar to the above-described brake operation. The hydraulic pressure transmitting device can be operated to activate the brake. By closing the second switching valve 15, the wheel cylinder pressure is kept constant, and by opening the third switching valve 16, the second liquid chamber 26 communicates with the reservoir 19, the pressure decreases, and the wheel cylinder pressure also decreases. I do. Further, in the present hydraulic pressure transmission device, the second piston 52 is separated from the third piston 53, and the second piston 5
Since only the second piston 2 moves independently, the third piston 53 does not move at the time of the automatic braking operation, and as a result, the inside of the input liquid chamber 63 does not become a negative pressure as described above. .

[Fail] When the pressure fluid from the accumulator 13 is not supplied for some reason and the hydraulic pressure transmitting device does not perform the hydraulic pressure transmitting function, the pressure fluid generated in the master cylinder is supplied to the control valve 3. The first and second output ports 29, 30 are transmitted directly to the cut valves 59 of the hydraulic pressure transmitting devices 4, 5 → the pressurizing chamber 61 → the output ports 62 → the wheel cylinders 7, 8 to perform a braking action. be able to. In the present hydraulic pressure transmitting device, as described above, the diameter of the hydraulic piston of the tandem master cylinder can be made relatively small, so that a sufficient braking force can be secured even when the accumulator 13 fails. Further, when the system of the first hydraulic pressure generation chamber 2a of the tandem master cylinder 2 fails, the hydraulic pressure of the second hydraulic pressure generation chamber 2b of the tandem master cylinder 2 flowing into the third hydraulic chamber 27 of the control valve 3 is increased and decreased. Hydraulic pressure is generated in the wheel cylinders 7 and 8 of the wheels as in the normal state. On the other hand, the tandem master cylinder 2
When the system of the second hydraulic pressure generating chamber 2b fails, the balance piston 20 moves by the hydraulic pressure of the first hydraulic pressure generating chamber 2a and comes into contact with the diaphragm piston 20, and the diaphragm piston 20 moves to the left. By the movement, hydraulic pressure is generated in the front and rear wheel cylinders 7 and 8 as in the normal state.

[0038]

As described in detail above, according to the present invention,
During the initial operation of the brake, when the spool piston moves with the hydraulic pressure generated in the master cylinder and the accumulator pressure acts on the boost chamber, the hydraulic pressure also moves the flow absorption piston, increasing the boost chamber volume and moving the spool piston. In the initial operation of the spool piston, the boost chamber can be maintained at an extremely low pressure, thereby achieving an excellent effect that a quick boost action can be started from a low hydraulic pressure state. be able to.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a vehicle brake booster according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a control valve in the brake booster.

FIG. 3 is an enlarged sectional view of a hydraulic pressure transmission device in the brake booster.

FIG. 4 is an enlarged sectional view of a pump in the brake booster.

FIG. 5 is a configuration diagram of a conventional brake booster.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 brake pedal 2 master cylinder 3 control valve 4 front wheel side hydraulic pressure transmitting device 5 rear wheel side hydraulic pressure transmitting device 6 pump 7,8 wheel cylinder 9 hold valve 10 decay valve 11 antilock reservoir 12 proportioning valve 13 accumulator 14 First switching valve 15 Second switching valve 16 Third switching valve 17 Pressure sensor 18 Relief valve 20 Balance piston 21 Diaphragm piston 22 Spool piston 23 Flow absorption piston 51 First piston (booster piston) 52 Second piston 53 Third piston 59 Cut valve 61 Pressurizing chamber 66 Pressure introducing chamber 71, 72 Antilock control pump 73 Booster pump

Claims (2)

[Claims] 1. A vehicle brake booster having a control valve capable of supplying a wheel cylinder while controlling a hydraulic pressure of a hydraulic pressure source by moving a spool piston by a hydraulic pressure generated in a master cylinder. The flow-absorbing piston is arranged opposite to the spool piston arranged inside, and the flow-absorbing piston moves according to the amount of movement of the spool piston, thereby suppressing the generation of hydraulic pressure due to the initial movement of the spool piston. Vehicle brake booster. 2. The control valve according to claim 1, wherein the control valve includes a spool piston that moves by a hydraulic pressure generated in a master cylinder, a boost chamber that introduces hydraulic pressure of a hydraulic pressure source by moving the spool piston, and supplies the hydraulic pressure to a wheel cylinder. A brake booster for a vehicle, comprising: a flow absorption piston disposed to face a piston and retreating from the boost chamber due to an increase in hydraulic pressure in the boost chamber.