JP2819422B2 - Brake booster center valve - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a center valve of a brake booster used for truckers and the like.

[Prior Art] FIG. 2 is a side sectional view of a center valve portion of a conventional brake booster, and FIG. 3 is a sectional view of a portion of a piston 17 and an insert 2 in FIG.

In FIG. 2, a rod 1 is a piston rod of an air actuator (not shown) and an insert 2
A pin 1a is fitted between the piston 1 and the rod 1, the insert 2 is fitted to the piston 17 so as to be able to slide in the axial direction, and the notch 2a of the insert 2 and the notch 17c of the piston 17 are fitted. Is mounted with the lifter 3, the piston 17 is fitted to the cylinder 8a so as to be slidable in the axial direction, the cylinder body 8 is screwed to the body 9, and the chamber 9b is connected to a reservoir (not shown) through a bore 9c. Communicating.

The seat 6 fitted in the bore 17a of the piston 17 is fixed in its axial movement in the piston 17 by a C-ring 6b, and a spring 4a is interposed between the valve stem 14 and the seat 6. The valve 5 is fixed to the valve stem 14, and the valve 5 is a valve seat.
The configuration to selectively sit on 17b, the displacement chamber 8b,
It communicates with the wheel cylinder on the wheel of the car.

A well-known parking wedge brake is mounted on the wheel cylinder.

This wedge brake compresses an internal spring with compressed air in the driving and running state of the vehicle, leaves the wedge brake open, and when the vehicle is stopped and the parking brake is applied, the compression is applied. When the air is evacuated, the wedge brake operates the wheel cylinder to apply the brake to the wheel by the urging force of the spring that has been compressed.

The air actuator for operating the rod 1
It 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 rightward through the insert 2 according to the air pressure. To the piston 17.

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

To release the service brake, the depression of the brake pedal is released, whereby the pressing force of the rod 1 to the right, that is, the pressing force of the piston 17 to the right disappears and the hydraulic oil in the displacement chamber 8b is released. Is depressurized, and the biasing force of the return spring installed inside the wheel cylinder is
Hydraulic oil is pushed back into the displacement chamber 8b and, under continuous conditions, the piston 17 is returned to its initial position in FIG. 2 by the returned hydraulic oil.

At this time, when it is returned to its initial position, lifter 3
Abuts against the side wall 9a and the lifter 3 pushes up the bubble stem 14, whereby the displacement chamber 8b
a, between the pushed-up valve 5 and the valve seat 17b, communicating with the reservoir through the notches 2a and 17c, the chamber 9b and the perforation 9c.

In this case, normally, the amount of pressure oil that has displaced the operating oil in the displacement chamber 8b by depressing the brake pedal displaces the displacement chamber in the wheel cylinder, so in a state where the depression of the brake pedal is returned, The hydraulic fluid displaced from the wheel cylinder is displaced into the displacement chamber 8b. Therefore, ideally, the displacement does not cause an excess or deficiency of the hydraulic oil in the displacement chamber 8b.

However, when the amount of hydraulic oil in the displacement chamber 8b actually becomes excessive or insufficient, when the brake pedal is returned as described above and the piston 17 is returned to the left end in FIG. By floating from the seat 17b, the excess and deficiency of the hydraulic oil in the displacement chamber 8b is automatically corrected.

[Problem to be Solved by the Invention] As described above, when the brake is applied only by operating the brake pedal, no problem occurs.

However, when the parking brake is applied in the state where the brake pedal is depressed as described above, and when the brake pedal is depressed in the state where the parking brake is applied, the valve 5 is depressed after several uses. May be damaged.

The cause of the damage was found to be caused by the following phenomenon.

When the parking brake is applied while the brake pedal is depressed, on the one hand, the pressurized oil from the displacement chamber 8b is being pushed into the hole cylinder, and on the other hand, the wedge brake by the parking operation is used for the wedge brake. Constant spring biasing force acts, and the spring biasing force
In parallel with the oil pressure from 8b, it has been applied to the wheel cylinders.

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

For this reason, 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 urging force.

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

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

An object of the present invention is to provide a center valve of a brake booster in which the above-described breakage of the valve 5 is prevented.

[Features to solve the problem] A rod (1) that operates in the axial direction by operating a brake pedal, and a cylinder (8) that moves in conjunction with the movement of the rod.
A valve (5) is interposed between the axially operated piston (7) in a), and a displacement chamber is formed by the cylinder and the piston.

The valve closes the communication between the displacement chamber and the reservoir by the spring (4a) when the rod is pushing to the side of pressurizing the hydraulic oil in the displacement chamber, and at a position where the pushing of the rod is completely returned. , The valve is pushed up by the lifter (3) to establish the communication.

This means that when the rod is operated, the operating oil pressure is generated in the displacement chamber, the service brake is applied to the wheel cylinder, and when the load is returned,
The reservoir and the displacement chamber are communicated with each other to correct the excess or deficiency of the hydraulic oil in the displacement chamber, and these portions have the same configuration as that of the related art.

Further, the displacement chamber is connected to a wheel cylinder operated by a wedge brake for parking brake, and the configuration is the same as that of the related art.

In the above conventional configuration, when the lifter pushes up the valve between the displacement chamber and the reservoir, the degree of the communication between the displacement chamber and the reservoir is gradually increased in accordance with the pushing up. The variable throttle mechanism is interposed in series with the valve.

This means that when the parking brake is applied in a state where the brake pedal is depressed, and when the brake pedal is depressed in a state where the parking brake is applied, the following operation is performed.

When the brake pedal is depressed in a state where the brake pedal is depressed and the parking brake is applied, when the brake pedal is released, a high oil pressure is not generated in the displacement chamber as in the related art. However, when the lifter pushes up the valve, the degree of the communication between the displacement chamber and the reservoir gradually increases in accordance with the push up, that is, a part of the communication flow path is changed to a variable throttle flow path. Because it has a configuration, at the start of opening the valve,
The pressure difference of the pressure oil flowing from the displacement chamber side of the valve opening portion to the reservoir side is reduced.

[Examples] Hereinafter, the present invention will be described based on examples.

FIG. 1 is a side sectional view showing one embodiment of a center valve portion of a brake booster according to the present invention.
The illustration corresponds to the illustrated part of FIG. 2 in the related art.

1 is different from FIG. 2 in the portion of the valve stem 4 and the piston 7, and the other portions are the same.

The difference between the valve stem 4 and the piston 7 in FIG. 1 and the valve stem 14 and the piston 17 in FIG. 2 is that the large-diameter portion 4b of the valve stem 4 is seated on the valve seat 7b of the valve 5. , Small diameter part drilled in piston 7
When the valve stem 4 is pushed up by the lifter 3, the large diameter portion 4b fits into the large diameter portion 7c formed in the piston 7, and the large diameter portion 4b And large diameter part 7c
The point in the radial direction is that the hydraulic oil is large enough to freely flow.

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

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 rightward through the insert 2 according to the air pressure. To the piston 7.

When the piston 7 is pushed left and right in this manner, the lifter 3 enters a play state and the valve 5 is seated on the valve seat 7b by the urging force of the spring 4a, and the pressure of the hydraulic oil in the displacement chamber 8b increases. , The pressure acts on the wheel cylinder to apply a service brake to the wheel.

When releasing the service brake, the brake pedal is returned, whereby the pressing force of the rod 1 to the right, that is, the pressing force of the piston 7 to the right disappears and the pressure oil in the displacement chamber 8b is reduced. Then, the urging force of the return spring provided in the wheel cylinder pushes the hydraulic oil back to the displacement chamber 8b, and the piston 7 is returned to the initial position in FIG. It is.

At this time, when the piston 7 is returned to its initial position, the lifter 3 comes into contact with the side wall 9a to push up the valve stem 4 from the valve seat 7b as shown in the figure. By that,
The large diameter portion 4b shifts to the position of the large diameter portion 7c, and the displacement chamber 8b is
Perforation 6a, an annular gap between the large diameter portion 4b and the large diameter portion 7c in the radial direction,
Between the pushed-up valve 5 and the valve seat 7b, the notch 2a and
It communicates with the reservoir via 7c, chamber 9b and perforation 9c.

The operation up to this point is basically the same as the conventional operation. That is, in the above operation, the lifter 3 is
When the valve stem 4 is pushed up from the valve seat 7b by contacting the valve stem 9a, the displacement chamber 8b communicates with the reservoir in the same manner 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 7c by pushing up the valve stem 4, the step between the small-diameter portion 7d and the large-diameter portion 7c gradually increases. Since the diameter is increased to the large diameter portion 7c side, the chamber 7e communicates with the displacement chamber 8b through the perforation 6a, and the communication flow passage area gradually increases. Will be.

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

This means that the problem of returning the depressing of the brake pedal while the parking brake is applied, which has been a problem in the related art, is solved by the following operation.

When the brake pedal is released again while the parking brake is being applied, the high oil pressure is kept generated in the displacement chamber 8b as in the conventional case.

However, when the rod 1 is returned to the left end in FIG. 1 and the lifter 3 pushes up the valve stem 4, the large-diameter portion 4b shifts from the small-diameter portion 7d side to the large-diameter portion 7c side. The displacement chamber 8b gradually communicates with the chamber 7e.

This means that the valve 5 rises from the valve seat 7b and cuts out the chamber 7e.
When communicating with the 2a side, once the chamber 7e is pushed away
The hydraulic pressure at 8b is reduced at the variable throttle portion, and the reduced pressure oil is applied to the valve 5 that floats from the chamber 7e.
It flows to the notch 2a side through the portion.

Further, the pressure drop from the displacement chamber 8b to the chamber 7e is gradually performed due to the presence of the variable throttle, and finally, the valve 5
In the state where is pushed up to the maximum, the variable aperture amount becomes the maximum. Therefore, when there is an excess or deficiency of the hydraulic oil in the displacement chamber 8b, the exchange of the hydraulic oil between the displacement chamber 8b and the reservoir can be sufficiently performed in a state where the variable throttle amount reaches the maximum.

In the above embodiment, the variable throttle mechanism is provided between the displacement chamber 8b and the valve 5. However, the variable throttle mechanism may be provided between the valve 5 and the notch 2a, and the variable throttle may change the throttle amount by pushing up the valve stem 4 as described above. It is a valve 5 in which the pressure oil flows from the displacement chamber 8b to the notch 2a.
This is because, even if the flow is restricted on the downstream side, the pressure difference of the hydraulic oil before and after the valve 5 becomes small.

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

In series with the valve between the displacement chamber and the reservoir,
When the valve 5 is pushed up, the degree of communication between the displacement chamber 8b and the reservoir is gradually expanded in accordance with the pushing up, so that the brake pedal is depressed and the parking wedge brake is applied, Then, even if the parking pedal is returned, the valve 5 will not be damaged, which contributes to the improvement of the reliability of the brake booster as a security part.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a center valve portion of a brake booster as one embodiment of the present invention, and FIG. 2 is a side sectional view showing a center valve portion of a conventional brake booster. FIG.
FIG. 3 is a sectional view taken along a line II in FIG. 2. The main symbols used in the examples are as follows. 1: rod, 2: insert, 3: lifter, 4: valve stem,
4b: large diameter part, 5: valve, 7: piston, 7c: large diameter part, 7d: small diameter part, 7e: chamber.

Claims (1)

(57) [Claims] A rod (1) which operates in the axial direction by operation of a brake pedal, and a piston (7) which is operated in the axial direction in a cylinder (8a) in conjunction with the movement of the rod.
A valve (5) is interposed between the cylinder and the piston to form a displacement chamber, and the valve is configured such that when the rod pushes hydraulic oil in the displacement chamber to a side that pressurizes hydraulic oil, The communication between the displacement chamber and the reservoir is closed by the spring (4a), and the valve is pushed up by the lifter (3) at a position where the pushing of the rod is completely returned. In the above configuration, the displacement chamber is connected to a wheel cylinder operated by a wedge brake for parking brake. When the lifter pushes up the valve between the displacement chamber and the reservoir, the displacement is increased. A variable throttle mechanism that gradually expands the degree of communication between the displacement chamber and the reservoir in accordance with Brake booster sensor valve, characterized in that it is interposed in the column.