JPH03204366A - Center valve of brake booster - Google Patents

Abstract

PURPOSE:To prevent the breakage of a valve by interposing a variable throttle mechanism for gradually extending the degree of communication according to the push up of a lifter between a displacement chamber and a reservoir. CONSTITUTION:When the operation of a brake pedal is returned in the state where the brake pedal is operated and a parking brake remains operated, a high oil pressure is generated in a displacement chamber 8b, and when a lifter 3 pushes up a valve 5, the degree of communication between the displacement chamber 8b and a reservoir chamber is gradually extended according to the pushing. Namely, the constitution is such that, when the large diameter part 4b of a valve stem 4 is moved from a small diameter part 7d to a large diameter part 7b by the pushing of the valve stem 4, a stepped part between the small diameter part 7d and the large diameter part 7c is gradually extended in diameter to the large diameter part 7c, so that the area of the passage for communication is gradually extended. Namely, as the passage forms a variable throttle, the difference in pressure of the oil in the opening part is reduced when the opening of the valve 5 is started.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a center valve of a brake booster used in a truck or the like.

[Prior Art] Fig. 2 shows a side sectional view of the center/help part of a conventional brake booster, and Fig. 3 shows a close sectional view of the piston 17 and insert 2 part in Fig. 2. .

In FIG. 2, rod 1 is a piston rod of an air actuator (not shown), a pin 1a is fitted between insert 2 and rod 1, and insert 2 is slid into piston 17 in the axial direction. The flap 3 is attached to the notch 2a of the insert 2 and the notch 17c of the piston 17, and the piston 17 is attached to the cylinder 8a.
The cylinder body 8 is screwed onto the body 9 so as to be slidable in the axial direction, and the chamber 9b communicates with a reservoir (not shown) through a hole 9C.

The seat 6 fitted into the hole 17a of the piston 17 is a C-ring 6.
A spring 4a is interposed between the valve stem 14 and the seat 6, and a valve 5 is fixed to the valve stem 14. 5 is configured to selectively sit on a valve seat 17b, and the displacement chamber 8b communicates with a wheel cylinder in a wheel of an automobile.

Further, the wheel cylinder is equipped with a well-known wedge brake for parking.

This wedge brake uses compressed air to compress an internal spring when the car is running.
If the wedge brake is left open and the car is stopped and the parking φ brake is applied, when the compressed air is released, the wedge brake will move to the wheel cylinder due to the force of the previously compressed spring. The brakes are applied to the wheels by operating the

Furthermore, the air actuator that operates the rod 1 is configured to be operated by air pressure from a well-known brake valve operated by a brake pedal.

The center valve of the conventional brake booster operates as follows.

When a brake pedal (not shown) is depressed and air pressure corresponding to the depression is sent from the brake valve to the air actuator, the rod 1 is moved to the right via the insert 2 in accordance with the air pressure. force is applied to the piston 17.

As the piston 17 is pushed to the right in this manner, the lifter 3 becomes idle in its axial movement, and the valve 5 is seated on the valve seat 17b due to the force of the spring 4a, and the displacement chamber 8b The pressure of the hydraulic oil inside increases, and this pressure oil acts on the wheel cylinder, applying the service brake to the wheel.

To release the service brake, the brake pedal is depressed back, thereby eliminating the rightward pressing force of the rod 1, that is, the rightward pressing force of the piston 17, and causing the pressure oil in the displacement chamber 8b to disappear. is depressurized, and the biasing force of the return spring installed inside the wheel cylinder pushes the hydraulic oil back into the displacement chamber 8b, and from the continuous condition,
The piston 17 is returned to its initial position in FIG. 2 by the returned hydraulic fluid.

At this time, when the lifter 3 is returned to its initial position, it comes into contact with the side wall 9a, and the lifter 3 touches the valve stem 14.
is pushed up, whereby the displacement chamber 8b communicates with the reservoir via the borehole 6a, between the pushed-up *5 and the valve seat 17b, the cutouts 2a and 17c, the chamber 9b and the borehole 9c.

In this case, normally, the amount of pressure oil that displaces the hydraulic fluid in the displacement chamber 8b when the brake pedal is depressed displaces the displacement chamber in the wheel cylinder, so when the brake pedal is released, The hydraulic fluid displaced from the wheel cylinder is again displaced into the displacement chamber 8b.

Therefore, ideally, the displacement does not cause excess or deficiency of hydraulic fluid in the displacement chamber 8b.

However, if an excess or deficiency of hydraulic fluid actually occurs in the displacement chamber 8b, when the brake pedal is returned and the piston 17 is returned to the left end in FIG. It floats up from the valve seat 17b and displaces the displacement chamber 8b.
Automatically corrects excess or deficiency of hydraulic fluid.

[Problems to be Solved by the Invention] As described above, if the brakes are applied only by operating the brake pedal, no particular problem arises.

However, as mentioned above, when the parking brake is applied with the brake pedal depressed, and the parking brake is still applied, when the brake pedal is released, after several uses, the valve 5 closes. Damage may occur.

It was found that this damage was caused by the following phenomenon.

When the parking brake is applied while the brake pedal is depressed, on the one hand, the pressure oil from the displacement chamber 8b is displaced into the hole cylinder, and on the other hand, the wedge brake due to the parking operation is filled with the pressure oil for the wedge brake. A certain spring force acts, and the spring force acts on the displacement chamber 8.
It is in a state where it is applied to the wheel cylinder in parallel with the hydraulic pressure from b.

In this state, when the brake pedal is released, even if the hydraulic pressure in the displacement chamber 8b is about to disappear, the spring biasing force acting on the wedge brake remains acting on the wheel cylinder.

Therefore, even when the piston 17 returns to the left end in FIG. 2, the hydraulic pressure remains in the displacement chamber 8b due to the action of the spring biasing force.

From this, when the piston 17 returns to the left end and the lifter 3 pushes up the valve 5 from the valve seat 17b, the narrow gap between the pushed up valve and the valve seat 17b is released from the displacement chamber 8b where the hydraulic pressure is generated. Pressure oil flows toward the cutout portion 2a side with a large pressure difference through the cutout portion 2a.

At this time, the synthetic rubber acid valve 5 is drawn inward due to the flow of the pressure oil and the pressure difference, and the valve 5 becomes easily damaged.

An object of the present invention is to provide a center pulp for a brake booster that prevents damage to the valve 5 as shown in letter L.

[Special feature 1 for solving the problem] A rod (1) that operates in the axial direction by the operation of the brake pedal, and a cylinder (8a) that operates in conjunction with the movement of the rod.
) A valve (5) is interposed between the cylinder and the piston (7) operated in the axial direction, and a displacement chamber is formed by the cylinder and the piston.

The valve closes communication between the displacement chamber and the reservoir by a spring (4a) when the rod is pushing the hydraulic oil in the displacement chamber toward the pressurizing side, and when the rod is fully pushed back, the valve closes the communication between the displacement chamber and the reservoir. , the valve is pushed up by the lifter (3) to establish communication.

This means that when the rod is operated, hydraulic pressure is generated in the displacement chamber to apply the service brake to the wheel cylinder, and when the rod is returned, the reservoir is communicated with the displacement chamber to operate the hydraulic pressure in the displacement chamber. It is designed to correct excess or deficiency of oil, and these parts have the same structure as conventional ones.

Furthermore, the displacement chamber is connected to a wheel cylinder operated by a parking wedge brake, and its configuration is the same as that of the conventional vehicle.

In the above-described conventional configuration, there is a new gap between the displacement chamber and the reservoir, and when the lifter pushes the valve up, the degree of communication between the displacement chamber and the reservoir is gradually adjusted according to the displacement. It is characterized by having a variable throttle mechanism that expands in series with the valve.

This means that when the brake pedal is depressed,
This means that when the parking brake is applied and the brake pedal is released while the parking brake is still applied, the following actions occur.

When the brake pedal is depressed and the parking brake is still applied, when the brake pedal is released, a high hydraulic pressure is generated in the displacement chamber as in the conventional case. However, when the lifter pushes up the valve, the degree of communication between the displacement chamber and the reservoir is gradually expanded, that is, a part of the communication channel is changed to a variable throttle channel. Because of this structure, when the valve starts opening, the pressure difference in the pressure oil flowing from the displacement chamber side to the reservoir side of the valve opening portion becomes small.

[Example] Hereinafter, the present invention will be explained based on Examples.

FIG. 1 shows a side sectional view of an embodiment of the center valve portion of a brake booster according to the present invention, and the illustration corresponds to the portion shown in FIG. 2 in the conventional art.

The difference between Fig. 1 and Fig. 2 is the valve stem 4.
and the piston 7, and the other parts are the same.

Valve stem 4 and piston 7 in FIG.
The difference between the valve stem 14 and the piston 17 in the figure is that when the valve stem 14 and the piston 17 are seated on the valve seat 7b of the valve 5,
The large diameter portion 4b of the valve stem 4 is slidably fitted into the small diameter portion 7d drilled into the piston 7, and when the valve stem 4 is pushed up by the lifter 3, the large diameter portion 4b is fitted into the small diameter portion 7d drilled into the piston 7. The radial gap between the large diameter portion 4b and the large diameter portion 7c is large enough to allow hydraulic oil to flow freely.

The operation of the configuration of the embodiment of the present invention described above will be explained below.

When the brake pedal (not shown) is depressed, air pressure corresponding to the pedal depression is sent from the brake valve to the air actuator.
exerts a rightward force on the piston 7 via the insert 2 in accordance with the air pressure.

As the piston 7 is pushed to the right in this way, the lifter 3 becomes idle and the valve 5 is seated on the valve seat 7b due to the urging force of the spring 4a, and the pressure of the hydraulic oil in the displacement chamber 8b is reduced. The increased pressure acts on the wheel cylinder, applying the service brake to the wheel.

To release the service brake, the brake pedal is returned to its original position, thereby eliminating the rightward pressing force of the rod 1, that is, the rightward pressing force of the piston 7, and reducing the pressure of the pressurized oil in the displacement chamber 8b. However, the biasing force of the return spring installed inside the wheel cylinder pushes the hydraulic oil back into the displacement chamber 8b, and from the continuous condition, the piston 7
is returned to its initial position in FIG. 1 by the returned hydraulic fluid.

At this time, when the piston 7 is returned to its initial position, the lifter 3 comes into contact with the side wall 9a and pushes the valve stem 4 away from the valve seat 7b, as shown in the figure. As a result, the large diameter portion 4b moves to the position of the large diameter portion 7C, and the displacement chamber 8b includes the perforation 6a, the annular gap between the large diameter portion 4b and the large diameter portion 7C in the radial direction, and the pushed-up valve. 5 and the valve seat 7b, it communicates with the reservoir via the notch 2a and the 7C1 chamber 9b and the perforation 9C.

2 The operation up to this point is basically the same as the conventional operation. That is, in the above action, the lifter 3
When the valve stem 4 is pushed up from the valve seat 7b by coming into contact with it, the displacement chamber 8b communicates with the reservoir, which is basically the same as in FIG.

However, when the large diameter portion 4b of the valve stem 4 moves from the small diameter portion 7d to the large diameter portion 70 due to the pushing up of the valve stem 4, the stepped portion between the small diameter portion 7d and the large diameter portion 7c gradually increases. Since the diameter is expanded toward the large diameter portion 7c, the area of the passage where the chamber 7e communicates with the displacement chamber 8b through the perforation 6a gradually increases. become.

That is, the communicating flow path forms a variable throttle.

This means that the conventional problem of releasing the brake pedal while the parking brake is still applied is resolved by the following action.

When the brake pedal is released while the parking brake is still applied, high hydraulic pressure continues to be generated in the displacement chamber 8b, as in the conventional case.

However, when the sled rod l is returned to the left end in FIG. 1 and the lifter 3 pushes the valve stem 4 up, the large diameter section 4b shifts from the small diameter section 7d side to the large diameter section 7C side. , at that time, the displacement chamber 8b gradually communicates with the chamber 7e.

This means that when the valve 5 floats up from the valve seat 7b and communicates the chamber 7e with the notch 2a side, the hydraulic pressure in the displacement chamber 8b is lowered in the variable throttle portion to the chamber 7e. The pressure oil whose pressure has been lowered flows from the chamber 7e to the notch 2a side via the floating portion of the valve 5.

Further, the pressure drop from the displacement chamber 8b to the chamber 7e occurs gradually due to the existence of the variable throttle, and finally, when the valve 5 is pushed up to the maximum, the variable throttle amount becomes maximum.

Therefore, if there is an excess or deficiency of hydraulic oil in the displacement chamber 8b, sufficient exchange of hydraulic oil can be carried out between the displacement chamber 8b and the reservoir when the variable throttling amount reaches its maximum.

Further, in the above embodiment, the variable throttle mechanism is provided between the displacement chamber 8b and the valve 5. However, this variable throttle mechanism is provided between the valve 5 and the notch 2a, and as described above, the variable throttle mechanism is provided between the valve 5 and the notch 2a. The variable throttle may change its throttle amount by pushing up the valve stem 4. Even if the flow of pressure oil is restricted on the downstream side of the valve 5 from the side of the displacement chamber 8b to the side of the notch 2a, 1. *This is because the pressure difference of the hydraulic oil around 5 becomes small.

[Effects of the Invention] As is clear from the above description, the effects of the present invention are as follows.

5. When the lifter 3 pushes up the valve 5 in series with the valve between the displacement chamber and the reservoir, the degree of communication between the displacement chamber 8b and the reservoir is gradually expanded in accordance with the push. By providing this, the valve 5 will not be damaged even if the brake pedal is depressed, the parking wedge brake is applied, and the brake pedal is then released, the brake booster is used as a safety component. This will contribute to improving reliability.

[Brief explanation of drawings]

FIG. 1 shows a side sectional view of a center valve portion of a brake booster according to an embodiment of the present invention, and FIG. 2 shows a side sectional view of a center valve portion of a conventional brake booster. Figure 3 shows
This is a cross-sectional view of FIG. 2. The main symbols used in the examples are as follows. 1: Rod, 2: Insert, 3: Riff 6 4: Valve stem 5: Valve, 7: Piston, 7d: Small diameter part, 7e: Chamber. 4b two large diameter parts, 7c: large diameter part,

Claims (1)

[Claims] 1. A rod (1) that operates in the axial direction by the operation of the brake pedal, and a cylinder (1) that operates in conjunction with the movement of the rod.
A valve (5) is interposed between the axially operated piston (7) in 8a), and a displacement chamber is formed by the cylinder and the piston; When the hydraulic oil in the displacement chamber is being pushed to the side to be pressurized, the spring (4a) closes the communication between the displacement chamber and the reservoir, and when the rod is fully pushed back, the lifter (3) closes the valve. In the above structure, the communication is performed by being pushed up, and the displacement chamber is connected to a wheel cylinder operated by a parking wedge brake. When the lifter pushes up the valve, a variable throttle mechanism is provided in series with the valve, which gradually expands the degree of communication between the displacement chamber and the reservoir in accordance with the pushing up. The center valve of the brake booster is characterized by: