JPS5852094B2 - Disc Brake Piston - Google Patents

Abstract

PURPOSE:Proposed is a piston used for a disc brake whose total composition is made of synthetic resin material so as to minimize its weight.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piston for a hydraulic actuation device for disc brakes used primarily in vehicles.

Disc brakes have lower gain than drum brakes, so it is necessary to increase the mechanical gain from the brake pedal to the wheel cylinder.

For this reason, the hydraulically actuated device for a disc brake has a piston that has a larger pressure receiving area than that of a drum brake, but this increases the weight of the entire hydraulically actuated device including the piston.

The piston of the conventional hydraulic actuator for disc brakes is
In order to reduce the weight, it is formed into a hollow or cup shape by cutting or forging, as illustrated in FIG.

The piston 5 is fitted into the hydraulic cylinder 4 and presses its open end against the back plate 8 to push the friction pad 10 onto the brake disc 2.
While frictionally engaging the hydraulic cylinder 4, this reaction force causes the hydraulic cylinder 4 to
The caliper 3 that is integral with the brake disc 2 is moved relative to the fixed member 1, the reaction force piece 6 is pressed against the back plate 7, and the friction pad 9 is frictionally engaged with the brake disc 2, thereby applying a braking force to the brake disc 2. is now granted.

At the open end, the outer periphery of the piston 5 is removed to form a small diameter part 13, one end of a cylindrical flexible dustproof boot 12 is tightly fitted and supported in this small diameter part 13, and the other end is attached to the cylinder. It is designed to be locked in the annular groove 4.

However, in order to reduce the weight, it is desirable that the entire piston 5 has a wall thickness that is approximately the same as the small diameter portion 13 to which the dustproof boot is attached, but such processing complicates the process and is disadvantageous in terms of cost. be.

SUMMARY OF THE INVENTION An object of the present invention is to provide a piston for a hydraulically actuated disc brake that is easy to manufacture and can be significantly reduced in weight.

For this reason, the configuration of the present invention is such that a substantially rectangular abutting piece that expands radially outward is integrally provided at the opening end of a cup-shaped core made of a metal plate, and the abutting piece is made to collide with at least the bottom end wall of the core. A through hole is provided in each of the joint pieces, and a main body made of a synthetic resin material is integrally joined to the inside of the through hole, the outer peripheral side of the core body, and the outer side of the end wall, so that the outer peripheral surface that fits into the cylinder and the liquid and a hydraulic pressure transmitting surface that abuts against the friction pad on the abutment piece.

To explain the present invention based on a specific embodiment, as shown in Fig. 2.3, the piston 15 has a synthetic resin layer 18 around a cylindrical reinforcing core or core 19 made of iron or aluminum. It is then molded under pressure and heat in one piece.

The core body 19 is formed by deep drawing the central part of a rectangular thin metal plate using a press to form a cylindrical part 24, and a plurality of through holes 22, 23 are bored in the bottom end surface 26 and the cylindrical part 24. .

A hole 29 is also formed in the flange or abutting piece 21 having a rectangular outer shape.

The synthetic resin layer 18 is applied to the outer peripheral part of the cylindrical part 24 and to the inner and outer parts of the bottom end face 26, where the synthetic resin layer 18 is tightly connected to the core body 19 through the holes 22, 23.

The interior of the cylindrical portion 24 is hollow.

Further, in the abutting piece 21, the synthetic resin is filled even into the hole 29, so that the abutting piece 21 is tightly connected.

In this way, a hydraulic pressure acting surface 27 on which hydraulic pressure acts is formed in the synthetic resin layer 18 parallel to the bottom end surface 26 of the core body 19, and the outer end surface of the abutting piece 21 is brought into contact with the back plate of the friction pad. It is assumed that the hydraulic pressure transmission surface is mating.

The outer peripheral surface 17 of the synthetic resin layer 18 is fitted into a hydraulic cylinder and forms a sliding surface.

An annular groove 16 for engaging a dustproof boot is formed in a portion of the circumferential surface 17 adjacent to the abutment piece 21.

As the material constituting the synthetic resin layer 18, acetal homopolymer, acetal copolymer, noryl resin, polyimide resin, polyphenylene sulfide resin, etc. can be used.

These resins have an extremely hard surface that goes onto pressure and heat molding.
Since it is highly wear resistant, it can be used as it is as a sliding surface with the rear pressure cylinder.

However, if necessary, this portion can be plated with hard chrome, for example, to further increase the strength against sliding with the hydraulic cylinder.

In addition, these synthetic resins include glass fiber or steel,
The strength can be further increased by mixing aluminum, other metal fibers, or gold powder.

When steel is used as the metal fiber, if there is a problem with rust or the like, it should be surface-treated, for example, plated or coated, before being mixed into the synthetic resin material.

To actually manufacture the piston, glass fiber or metal powder is mixed as a reinforcing material into the synthetic resin material mentioned above.
This material is filled into a mold, the core body 19 is further embedded inside the material, and the material is heated and pressurized to form the mold.

Through this heating and pressurizing process, grooves 16 for attaching the dustproof boots are simultaneously formed.

By using a synthetic resin material, the piston of the hydraulic actuator according to the present invention can be significantly lighter than a conventional steel column piston, and has an annular groove for attaching a dustproof boot and a friction An abutment piece for transmitting hydraulic pressure to the pad can be integrally and easily formed at the open end.

In particular, the abutting piece 21 is not limited to a rectangular shape, but can be, for example, fan-shaped, in accordance with the shape of the back plate of the friction pad, and since this is integrally combined with the synthetic resin layer 19, transmission from the piston to the friction pad is achieved. This has the effect that the applied liquid pressure can be distributed more uniformly.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view illustrating a conventional disc brake equipped with a piston, FIG. 2 is a longitudinal sectional view of a piston of a hydraulically actuated device according to the present invention, and FIG. 3 is a left side view of the same piston. 15: Piston, 18 Two resin layers, 19: Core body, 21
: Abutting piece, 22, 23: Connector L 24: Cylindrical part, 26
: End face, 27: Hydraulic pressure acting surface, 29: Connector

Claims (1)

[Claims] 1 A substantially rectangular abutting piece that expands radially outward is integrally provided at the open end of a cup-shaped core made of a metal plate, and a through hole is provided in at least the bottom end wall of the core and in the abutting piece, respectively. A main body made of a synthetic resin material is integrally connected to the inside of the through hole, the outer circumferential side of the core body, and the outer side of the end wall, and each has an outer circumferential surface that fits into the cylinder and a hydraulic pressure acting surface. A piston for a hydraulically operated device for a disc brake, characterized in that the abutment piece is provided with a hydraulic pressure transmission surface that abuts against a friction pad.