JP2592299Y2 - Brake actuator - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic brake actuator such as a disc brake or a drum brake, which has a piston having a combination of a small-diameter piston and a large-diameter piston, and has a so-called ineffective stroke by a small amount of hydraulic oil. A brake actuator that can be quickly eliminated and has a quick brake operation response can ensure the operation and improve the durability.

[0002]

2. Description of the Related Art As a brake actuator having a piston in which a small-diameter piston and a large-diameter piston are combined, a so-called ineffective stroke is quickly eliminated by a small amount of hydraulic oil, and the brake responsiveness is promptly increased.
There is one described in JP-A-5-5488. The outline of this is described below with reference to FIGS. 3 and 4. That is, a cylindrical bush 4 is slidably fitted in the center hole of the large-diameter piston 3 fitted in the cylinder body 1, and a small-diameter piston 5 ′ having a large-diameter head 5 slides in this bush 4. They are freely fitted. A conical lock ring 7 is loosely fitted to the small-diameter piston 5 ', and its outer periphery is in contact with the large-diameter piston. The conical return spring 10 pushes the radially intermediate portion of the lock ring 7,
The large-diameter piston 3 is urged rightward by a return spring 10 via the lock ring 7. When the brake hydraulic oil is supplied from the import 2, the small-diameter piston moves forward before the head 5 comes into contact with the brake disk 6 because of its small resistance. When the head 5 comes into contact with the brake disk and the resistance increases, the internal pressure of the oil chamber 9 increases.
The oil pressure in the oil chamber 9 rises and the large-diameter piston 3
When you start to move forward (move to the left)
When the lock ring 7 is raised and its inner periphery grips the outer periphery of the small-diameter piston 5 ′ to integrate the small-diameter piston and the large-diameter piston, the large-diameter piston 3 strongly pushes the small-diameter piston 5 ′ through the lock ring 7. Activate the brake (see FIG. 4). When the oil pressure in the oil chamber 9 decreases, the large-diameter piston 3 is returned by the return spring 10, the grip on the small-diameter piston by the lock ring 7 is released, and a predetermined gap (hereinafter referred to as “pad”) is provided between the brake disk and the head 5. The small-diameter piston retreats (moves to the right) with respect to the large-diameter piston until clearance is created. With the above operation, the head 5 quickly comes into contact with the brake disk 6 with a small amount of hydraulic oil, and the initial position of the head 5 with respect to the wear of the brake pad is adjusted (wear compensation). The above is the outline of the prior art. The wear compensation is performed by moving the return position of the small-diameter piston with respect to the lock ring 7, and the small-diameter piston and the large-diameter piston are gripped by the lock ring 7 (frictional connection). The pressing force of the large-diameter piston 3 is transmitted to the small-diameter piston 5 'by the frictional coupling force between the lock ring 7 and the small-diameter piston 5'. The outer periphery of the piston is significantly worn and damaged, and the abrasion and damage of the lock ring 7 on the small-diameter piston 5 'become unstable and uncertain, resulting in poor durability.

[0003]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems of the prior art, and for that purpose, the above-mentioned wear compensation and integration of the small-diameter piston and the large-diameter piston are realized by a hydraulic mechanism. That is the task.

[0004]

Means taken to solve the above problem are constituted by the following elements (a) to (c). (A) A small-diameter cylinder is provided on a large-diameter piston that is fitted to the cylinder body and pressed toward the bottom of the cylinder body by a spring, and the small-diameter piston is slidably fitted to the large-diameter piston. A check valve is provided in a communication hole communicating with the oil chamber of the main body; (b) a protrusion is provided on the bottom surface of the oil chamber of the cylinder main body, and the check is performed by the protrusion when the large-diameter piston is at the return position. (C) The sliding surface between the small-diameter piston and the small-diameter cylinder is sealed with an annular elastic ring interposed between the small-diameter piston and the small-diameter cylinder.

[0005]

[Operation] When the brake cylinder is in the non-operation state, the check valve provided in the communication hole for communicating the small-diameter cylinder with the oil chamber of the cylinder body is released by the above-mentioned projection. In communication with the room.
Therefore, when the operating oil is supplied to the oil chamber of the cylinder body, the operating oil flows into the small-diameter cylinder, and the small-diameter piston having a small resistance is pushed out of the small-diameter cylinder in advance until the clearance of the brake pad becomes zero. When the clearance of the brake pad becomes zero and the resistance to the small-diameter piston increases, the hydraulic pressure of the cylinder body increases. When the large-diameter piston starts to move against the return spring due to the increase in the hydraulic pressure of the cylinder body, the large-diameter piston immediately separates from the bottom of the oil chamber of the cylinder body. Away and the return spring closes the check valve. As a result, the working oil in the small-diameter cylinder is confined, and the small-diameter piston and the large-diameter piston are hydraulically integrated. Therefore, the small-diameter piston is strongly pushed by the large-diameter piston to operate the brake. The seal mechanism using an annular elastic ring having a rectangular cross section is to slightly crush the annular elastic ring in the radial direction, and press the annular elastic ring against the seal surface by the repulsive force. The same applies to the elastic ring. Therefore, in the brake operation state,
Since the small-diameter piston moves to the left with respect to the annular elastic ring, distortion in the forward direction of the small-diameter piston is generated in the annular elastic ring, and the small-diameter piston receives a biasing force in the return direction by the repulsive force of the distortion. ing. When the hydraulic pressure in the cylinder body decreases, the large diameter piston is returned together with the small diameter piston by the return spring. Immediately before the large diameter piston comes into contact with the bottom surface of the oil chamber of the cylinder body, the projection pushes the valve body of the check valve to release the check valve. After the non-return valve is released, the small-diameter cylinder communicates with the oil chamber of the cylinder body via the non-return valve. It is. The small clearance of the small-diameter piston with respect to the large-diameter piston ensures the pad clearance (see the clearance C between the rotor R and the brake pad 21 in FIG. 1). The forward stroke of the small-diameter piston with respect to the large-diameter piston increases as the wear of the brake pad progresses, but the return stroke of the small-diameter piston with respect to the large-diameter piston is constant (the above-described return stroke due to the repulsive force of the annular elastic ring). The return position of the small-diameter piston relative to the large-diameter piston moves in the forward direction. The movement of the return position of the small diameter piston in the forward direction compensates for wear of the brake pad. Therefore, the pad clearance is always kept constant regardless of the wear of the pad.

[0006]

[Embodiment] Next, an embodiment will be described with reference to FIGS. Slidably fitted to the cylinder body 11,
The small-diameter cylinder 14 is provided on the large-diameter piston 12 urged in the return direction by the return spring 13, and the small-diameter piston 15 is slidably fitted to the small-diameter cylinder 14. A communication hole 14a for communicating the small diameter cylinder 14 with the oil chamber 16 of the cylinder body 11 is provided at the bottom of the small diameter cylinder 14, and a conical valve seat is provided in the communication hole 14a.
The valve ball 17 contacting the valve seat is connected to the communication hole 14.
The valve ball 17 is urged in the valve closing direction by an urging spring 18 to constitute a check valve. A projection 19 projects from the bottom of the oil chamber 16 of the cylinder body 11, and when the large-diameter piston is at the return position, its tip abuts against the valve ball 17 to separate the valve ball from the valve seat and check. Release the valve. The lift amount δ of the valve ball at this time must be a lift amount sufficient to sufficiently reduce the inflow resistance of the hydraulic oil into the small-diameter cylinder 14, while the invalid stroke of the large-diameter piston is the lift amount of the valve ball. Since the lift amount δ is equal to δ, from the viewpoint of minimizing the invalid stroke, the smaller the lift amount δ is, the better. An annular elastic ring 20 is fitted into an annular groove provided on the inner peripheral surface of the small-diameter cylinder 14, and the annular elastic ring is crushed in the radial direction to strongly grip the outer periphery of the small-diameter piston 15 by its elasticity. The sliding surface of the small-diameter cylinder and the small-diameter piston is completely sealed by this annular elastic ring, and the small-diameter piston advances leftward (leftward with respect to the annular elastic ring 20) in the small-diameter cylinder to form an annular shape. Generates an elastic strain in the forward direction of the small-diameter piston, and urges the small-diameter piston in the return direction by the repulsive force of the elastic strain. When the brake hydraulic oil is press-fitted from the import P, the piston 15 having a smaller diameter than the resistance of the return spring 13 to the large-diameter piston 12.
, The small-diameter piston moves forward (moves to the left) in advance by the hydraulic oil flowing from the oil chamber 16 of the cylinder body 11 into the small-diameter cylinder 14 through the check valve and the communication hole 14a. The pad clearance C between the brake pad 21 and the rotor R is set to zero. In this state, elastic distortion is generated in the annular elastic ring 20 in the forward direction of the small-diameter piston, and the small-diameter piston receives a biasing force in the return direction (rightward) by the repulsive force of the elastic distortion. When pad clearance C becomes zero, small-diameter piston 1
The large-diameter piston 12 is pushed to the left against the return spring 13 because the resistance to the hydraulic fluid 5 rapidly increases and the pressure of the hydraulic oil rapidly increases. Large-diameter piston lift amount of check valve δ
The valve ball 17 is separated from the tip of the projection 19 when the valve ball 17 slides by a stroke equal to. As a result, the hydraulic oil in the small-diameter cylinder 14 is closed.
5 is hydraulically locked (see FIG. 2) and the large-diameter piston 1
2, the large-diameter piston strongly presses the brake pad 21 via the small-diameter piston to operate the brake. The forward stroke of the large-diameter piston after the small-diameter piston is hydraulically locked is an extremely small stroke corresponding to the compression strain of the brake pad. When the pressure of the brake oil decreases, the small-diameter piston returns together with the large-diameter piston.
7 and the check valve is opened again, the integration of the small-diameter piston and the large-diameter piston is released, so that the small-diameter piston 15 is Returned to The pad clearance C is formed by the return of the small diameter piston by the biasing force of the annular elastic ring 20. Since the pad clearance C is a return stroke of the small diameter piston due to the urging force of the annular elastic ring 20, it is constant regardless of the magnitude of the wear of the brake pad. Assuming that the wear of the brake pad is zero, the small diameter piston moves to the left by the amount corresponding to the pad clearance C and the compressive strain of the pad, and returns by the same stroke. However, when the brake pad wears, the forward stroke of the small-diameter piston increases by that amount, but the return stroke is constant, so the return position of the small-diameter piston shifts in the forward direction (leftward) as the brake pad wears. Will be.
The movement of the return position of the small diameter piston compensates for the wear of the brake pad.

[0007]

[Effect] The invention and invention which solved the above-mentioned problem of the invention are not known. Therefore, solving this new problem,
It is the greatest effect of the present invention that the above-mentioned problem of the prior art is solved for the first time. In other words, a piston that combines a small-diameter piston and a large-diameter piston quickly eliminates a so-called ineffective stroke with a small amount of hydraulic oil, and a small-diameter piston that operates earlier in a brake actuator that speeds up brake operation response. Since the lock mechanism integrated with the large-diameter piston does not wear out, its operation is stable and reliable for a long time, and its durability can be significantly improved. In the prior art, the assembly accuracy of the lock ring 7, the small-diameter piston 5 ', and the large-diameter piston 3 and the machining accuracy therefor are required to be high, but the present invention requires such high assembly accuracy and machining accuracy. Since it does not have the required mechanism, the manufacturing cost can be significantly reduced as compared with the prior art.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment.

FIG. 2 is a schematic sectional view for explaining an operation state of the embodiment of FIG. 1;

FIG. 3 is a sectional view of a conventional technique.

FIG. 4 is a sectional view showing an operation state of the prior art of FIG. 3;

[Explanation of symbols]

 1, 11 ... cylinder body 2, P ... import 3, 12 ... large diameter piston 4 ... bush 5 ... head 5 ', 15 ... small diameter piston 6 ... brake disc 7・ ・ ・ Lock ring 9, 16 ・ ・ ・ Oil chamber 10, 13 ・ ・ ・ Return spring 14 ・ ・ ・ Small diameter cylinder 14a ・ ・ ・ Communication hole 17 ・ ・ ・ Valve ball 18 ・ ・ ・ Biasing spring 19 ・ ・ ・Projection 20: annular elastic ring 21: brake pad C: pad clearance δ: lift amount of check valve R: rotor

Claims (1)

(57) [Scope of request for utility model registration] A small-diameter cylinder is provided on a large-diameter piston which is fitted to a cylinder body and is pressed toward the bottom of the cylinder body by a spring, and the small-diameter piston is slidably fitted to the small-diameter cylinder. A check valve is provided in a communication hole that communicates with the oil chamber of the cylinder body, a protrusion is provided on the bottom of the oil chamber of the cylinder body, and the check valve is opened by the protrusion when the large-diameter piston is at the return position. A brake actuator in which a valve is valved and an annular elastic ring is interposed on a sliding surface between the small-diameter piston and the small-diameter cylinder to seal the sliding surface.