JPH0331649Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a hydraulic brake booster used in a brake device of a vehicle or the like.

[Conventional technology]

Conventionally, in the above-mentioned liquid brake booster, a power piston that provides driving force to a master cylinder piston is slidably housed in a booster housing, and a switching valve that is linked to a brake pedal is installed inside the power piston. is provided to form a pressure chamber that accommodates pressure fluid guided from an external pressure accumulator via the switching valve to provide fluid pressure to the power piston, and the pressure fluid in the pressure chamber is routed via the switching valve. A structure equipped with a low-pressure chamber into which water can flow is used.

In this conventional booster, when the brake pedal is depressed, the pedal force is transmitted to the master cylinder piston via the power piston, and pressure fluid is transferred from the pressure accumulator into the pressure chamber via the switching valve linked to the brake pedal. As the hydraulic pressure acts on the power piston, the force applied to the master cylinder piston increases by the amount of the hydraulic pressure acting on the power piston. In the return stroke when the brake pedal is released, the pressure fluid in the pressure chamber escapes to the low pressure chamber via the switching valve, and since the conventional low pressure chamber simply communicates with the reservoir, the fluid in the pressure chamber The pressure is released and the force acting on the master cylinder piston is completely released.

[Problem that the invention attempts to solve]

In the conventional structure, the low pressure chamber simply releases the pressure fluid stored in the pressure chamber and releases the fluid pressure acting on the power piston, so the fluid pressure is maintained in this low pressure chamber. Therefore, it is not possible to generate braking force unless you apply pressure to the brake pedal.Therefore, it is important to apply the brakes when stopping on a slope and leaving the driver's seat. I can't. The present invention aims to solve this problem and make it possible to generate braking force without relying on the force applied to the brake pedal.

[Means to solve the problem]

In order to solve the above problems, the present invention forms a low pressure chamber between the power piston and the master cylinder piston, and connects the pressure chamber to the low pressure chamber in the pressure fluid communication path between the pressure chamber and the low pressure chamber. A check valve that only allows flow to the pressure chamber is provided, and the low pressure chamber is communicated with the reservoir and the pressure accumulator via a directional switching valve that selectively communicates one of the passage to the reservoir and the passage to the pressure accumulator. It is something that

[Effect]

In the above configuration, if the directional switching valve is set so that the low pressure chamber communicates with the reservoir during normal brake operation using the brake pedal, when the pressure on the brake pedal is released, the pressure fluid in the pressure chamber will flow through the switching valve. The fluid passes through the communication path and opens the check valve to flow into the low pressure chamber, and since this low pressure chamber is in communication with the reservoir, the fluid pressure in the pressure chamber is released, and therefore the fluid acting on the power piston flows into the low pressure chamber. The pressure is released and the force acting on the master cylinder piston is released.

When you want to apply the brakes without using the brake pedal, switch the directional switching valve.
When the low pressure chamber is communicated with the pressure accumulator, the pressure liquid in the pressure accumulator flows into the low pressure chamber, and the communication path from the pressure chamber to the low pressure chamber is closed by the check valve, so that the pressure liquid in the pressure accumulator flows into the low pressure chamber. The hydraulic pressure is maintained. Therefore, this hydraulic pressure acts on the master cylinder piston, making it possible to generate braking force without stepping on the brake pedal.

[Embodiment] In FIG. 1, reference numeral 1 indicates a hydraulic brake booster used in a vehicle brake system, and a power piston 3 is slidably housed in a booster housing 2. A switching valve 4 is slidably provided inside the switching valve 4, and an input shaft 5 that is connected to a brake pedal (not shown) is in contact with the outer part of the switching valve 4. 7 is a plug that prevents the power piston 3 from coming off. The power piston 3 is formed with an annular protrusion 3a, and a pressure chamber 8 is formed on the side of the input shaft 5 side end surface 3b of the power piston 3. Note that 9 is a stopper plate fixed to the switching valve 4.

10 is a pressure accumulator, 11 is a pump that supplies pressure fluid (pressure oil), 12 is a motor, the housing 2 is provided with an opening 2a that communicates with the pressure accumulator 10, and the power piston 3 has a circumference that communicates with the opening 2a. Groove-shaped recess 3
c, an inlet passage 3d leading to the inside, and a communication passage 3f opening from the inside to the other end surface 3e of the power piston 3.

A reaction force chamber 13 is formed in the inner part of the switching valve 4, and a return spring 1 is installed in this reaction force chamber 13.
4 are provided.

The switching valve 4 has the reaction force chamber 1 passing through the center.
3, a passage 4b that communicates the central passage 4a with the pressure chamber 8, and a switching valve 4.
When moving forward, the center passage 4a and the power piston 3
A passage 4c that communicates with the inlet passage 3d of the power piston 3, and a passage 4d that communicates the central passage 4a with the communication passage 3f of the power piston 3 when the switching valve 4 is retracted are provided.

The front part of the housing 2 is a brake master cylinder A, and a master cylinder piston 15 is slidably accommodated therein, and a protruding rod 17 fixed to the power piston 3 abuts one end of the master cylinder piston 15. A low pressure chamber 18 is formed between the power piston 3 and the master cylinder piston 15, and a spring 19 is provided to bias the master cylinder piston 15 toward the power piston 3.

An opening 2b is formed in the low pressure chamber 18 portion of the housing 2, and the directional switching valve 2 is provided in this opening 2b.
1 is connected, and this direction switching valve 21 selectively communicates one of the passage 23 to the reservoir 22 and the passage 24 to the pressure accumulator 10, and the low pressure chamber 18
is in communication with the reservoir 22 and the pressure accumulator 10 via the directional switching valve 21. Note that 25 is a pressure reducing valve.

Further, on the end surface 3e of the power piston 3 on the side of the low pressure chamber 18, an elastic plate 26 such as a rubber plate that contacts the outlet portion of the communication passage 3f in an elastically deformable manner, that is, a check valve is provided. The system allows only the flow of

Note that 2c is an opening of the master cylinder A that communicates with a wheel cylinder (not shown), and 27 is an opening that connects the reservoir of the master cylinder A (not shown).

Next, the operation will be explained.

When the brake pedal is depressed, the switching valve 4 is pushed through the input shaft 5, moves forward from the state shown in FIG. 3 entrance passage 3d
The passage 4c of the switching valve 4 communicates with the pressure accumulator 10.
Pressurized fluid is introduced into the pressure chamber 8 from above, and the fluid pressure acts on the power piston 3. Therefore, the master cylinder piston 15 receives the brake pedal force from the input shaft 5 and the force of the hydraulic pressure in the pressure chamber 8 acting on the power piston 3, and generates a large hydraulic pressure to operate a wheel cylinder (not shown). to generate braking force. At this time, only the hydraulic pressure within the reaction force chamber 13 is transmitted to the input shaft 5 as a reaction force.

When the brake pedal is released, the power piston 3, which was moving forward, is moved to the master cylinder piston 1 by the hydraulic pressure of the master cylinder A and the force of the spring 19.
5, the switching valve 4 is pushed back by the return spring 14 and retreats inside the power piston 3, the passage 4d communicates with the communication passage 3f of the power piston 3, and the pressure fluid in the pressure chamber 8 flows through the communication passage 3f. , opens the elastic plate (check valve) 26 and escapes to the low pressure chamber 18 , and from the low pressure chamber 18 passes through the direction switching valve 21 and escapes to the reservoir 24 . Therefore, the hydraulic pressure acting on the power cylinder 8 is released, and the force acting on the master cylinder piston 15 is released.

When applying the brakes without using the brake pedal, when the direction switching valve 21 is switched to the passage 24 on the pressure accumulator 10 side, the low pressure chamber 18 is communicated with the pressure accumulator 10, and the check valve 26 is connected to the power cylinder 3.
Since the communication passage 3f is closed, the hydraulic pressure of the pressure accumulator 10 is maintained in the low pressure chamber 18, and therefore, the master cylinder piston 15 is actuated by the hydraulic pressure to generate hydraulic pressure in the master cylinder A. , generates braking force.

FIG. 2 shows another embodiment of the check valve, in which a metal plate 31 is provided in place of the elastic plate 26 of the previous embodiment, and the metal plate 31 is connected to the power piston by a spring 32. It is pressed against the end face of the

FIG. 3 shows yet another embodiment of the check valve. This check valve 33 houses a check ball 34 and is provided with a weak spring 35 for applying a slight opening pressure.

Since the check valve 33 of this embodiment has a slight opening pressure, in the return stroke of the switching valve 4, the pressure inside the pressure chamber 8 and the reaction force chamber 13 is not completely released, but the slight pressure is increased. Therefore, the switching valve 4 is pushed by the residual pressure and returns to its original position. Therefore, as shown in the figure, it is possible to omit providing a return spring in the reaction force chamber 13 for returning the switching valve 4.

[Effect of idea]

According to the present invention, the low pressure chamber is connected to the reservoir and the pressure accumulator via the directional switching valve so that either one can be selected, and a check valve is provided in the communication path leading from the pressure chamber to the low pressure chamber. By switching the direction switching valve to the pressure accumulator side, braking force can be generated without stepping on the brake pedal.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a hydraulic brake booster showing an embodiment of the present invention, with a hydraulic circuit diagram added;
FIG. 2 is a sectional view of a main part of a hydraulic brake booster showing another embodiment of the check valve, and FIG. 3 is a sectional view of the same main part showing still another embodiment of the check valve. 2... Booster housing, 3... Power piston, 3f... Communication passage, 4... Switching valve, 5...
...Input shaft, 8...Pressure chamber, 10...Pressure accumulator, 13
...Reaction force chamber, 14...Return spring, A...
... Brake master cylinder, 15 ... Master cylinder piston, 18 ... Low pressure chamber, 21 ... Direction switching valve, 22 ... Reservoir, 23, 24 ... Passage,
26...Elastic plate (check valve), 30, 33...
Check valve, 34...Check ball, 35...
spring.

Claims (1)

[Claims for Utility Model Registration] (1) A power piston that provides driving force to the master cylinder piston is slidably accommodated in the booster housing, and inside the power piston,
A switching valve is provided that works with the brake pedal.
A pressure chamber is formed that accommodates pressure fluid led from an external pressure accumulator through the switching valve to apply fluid pressure to the power piston, and the pressure fluid in the pressure chamber can flow through the switching valve. In a liquid brake booster equipped with a low-pressure chamber, the low-pressure chamber is formed between a power piston and a master cylinder piston, and a low-pressure a check valve that allows flow only into the chamber, and a directional control valve that selectively communicates the low pressure chamber with one of the passage to the reservoir and the passage to the pressure accumulator;
A hydraulic brake booster characterized by communicating with a reservoir and a pressure accumulator. (2) The liquid according to claim 1, wherein the check valve is constituted by an elastic plate that is in contact with the outlet portion of the communication passage on the end face of the power piston on the side of the low pressure chamber so as to be able to be elastically deformed. Type brake booster. (3) Registration of a utility model characterized in that the check valve has a slight opening pressure so as not to completely release the pressure in the pressure chamber and the reaction force chamber at the back of the switching valve that communicates with the pressure chamber. A hydraulic brake booster according to claim 1.