JPH0893916A - Resin made piston for disk brake - Google Patents

Abstract

PURPOSE: To reuse the piston after a disk brake is disassembled without a possibility of breaking down the corner part of the piston by forming a metallic reinforcing member on the corner part of at least brake liquid pressure receiving surface side of the resin made piston used for the disk brake. CONSTITUTION: In a resin made piston 10 used for the disk brake, a metallic reinforcing member 12 is provided on the corner part of a brake liquid pressure receiving surface side of the synthetic resin made piston body 11 having a cap-like cavity. Thus, since a part of the piston 10 in contact with the inner peripheral surface of a cylinder in a maintenance operation including the replacement or the like of a piston boot 18 is reinforced with the metallic reinforcing member 12, the corner part of the piston 10 is prevented from being broken down by a pinch between the inner peripheral surface of the cylinder and the piston 10. Thus, the same piston 10 is allowed to be again used after the replacement of the piston boot 18. Also, in place of the reinforcing member 12 an elastic material like rubber may be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disc brake piston, and more particularly to a resin piston.

[0002]

2. Description of the Related Art Conventionally, as a piston used for a disc brake, there is a piston molded of resin for weight reduction. For example, FIG. 3 shows a disc brake piston disclosed in Japanese Utility Model Publication No. 62-24118. This piston is provided at the open end of the cup-shaped resin piston 30 in order to reinforce the portion in contact with the brake pad.
A metal reinforcing member 35 for covering the inner peripheral surface, the outer peripheral surface of the opening end portion and the opening end surface is provided. The reinforcing member 35 is formed into a substantially L-shaped cross section, and the inner peripheral surface 31 of the piston body 30 and the opening The reinforcing member contacting the end surface 34 has a plurality of gas vent holes 3
6, 37 are provided.

[0003]

However, the resin-made piston disclosed in the above publication secures the strength of the piston at the position where it abuts on the brake pad. For example, the disk is used when the piston seal is replaced. During maintenance that requires disassembling the brake, when the piston is pulled out of the cylinder vigorously with air pressure, the inner peripheral surface of the cylinder and the piston twist and the piston collides with the metal cylinder body, resulting in the brake fluid pressure of the piston. There is a risk that the corners on the pressure receiving surface side will be chipped, and in such a case, a new piston must be used after maintenance, making reuse of the piston impossible.

Therefore, the present invention provides a reusable resin piston in which the piston is not chipped even when the piston is removed from the cylinder by air pressure during maintenance requiring disassembly of the disc brake. It is an issue.

[0005]

In order to solve the above-mentioned problems, the invention of claim 1 forms a metal reinforcing member in at least a corner portion of a resin piston used for a disc brake on the pressure receiving surface side of the brake fluid pressure. .

Further, in order to solve the above-mentioned problems, a second aspect of the present invention is provided.
In the invention, the elastic member is formed at least at the corner portion on the pressure receiving surface side of the brake fluid pressure of the resin piston used for the disc brake.

[0007]

According to the invention of claim 1, even when a twist occurs between the inner peripheral surface of the cylinder and the piston when the piston is removed from the cylinder by air pressure during maintenance requiring disassembly of the disc brake, Since the portion of the piston that comes into contact with the inner peripheral surface of the cylinder is reinforced by the metal reinforcing member, the piston will not be chipped.

According to the second aspect of the present invention, during maintenance requiring disassembly of the disc brake, even when twisting occurs between the inner peripheral surface of the cylinder and the piston when the piston is removed from the cylinder by air pressure, Since the portion of the piston that comes into contact with the inner peripheral surface of the cylinder is an elastic member, it is possible to prevent the piston from chipping due to elastic deformation of the twisted portion.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a front sectional view when the resin piston 10 of the present invention is used in a general disc brake. FIG. 2 shows a resin piston 10 according to a first embodiment of the present invention, in which a metal reinforcing member 12 is provided at a corner portion of a piston body 11 made of a synthetic resin on the pressure receiving surface side of a brake fluid pressure. The piston body 11 has a cup-shaped inner space 13. Further, if the metal reinforcing member 12 is protruding from the piston main body 11 on the sliding surface of the resin piston 10 with respect to the cylinder inner peripheral surface, sliding of the piston 10 is affected. It is necessary to form it so that it does not protrude from the outer periphery of.

In this embodiment, the cylinder body 14 is made of cast iron, and the piston body 11 is made of synthetic resin. The reinforcing member 12 may be any metal as long as it has a hardness equal to or higher than that of the cylinder body 14.

Next, the operation will be described. When the brake fluid is introduced from the brake fluid introduction hole 15 of the cylinder body 14, the brake fluid pressure in the cylinder increases, whereby the piston 10 presses the brake pad 16,
As a result, the brake pad 16 becomes the disc rotor 17
Is pressed to generate braking force.

Here, when performing maintenance of the disc brake including replacement of the piston boot 18, etc.,
It is necessary to remove the disc brake from the vehicle and remove the piston 10 from the cylinder body 14 by introducing air pressure from a brake fluid introduction hole provided in the cylinder body 14. At this time, due to a minute clearance between the outer circumference of the piston 10 and the inner circumference of the cylinder, twisting occurs between the inner circumferential surface of the cylinder and the piston 10 before the piston 10 is removed. However, since the portion of the piston 10 that comes into contact with the cylinder inner peripheral surface due to the twist between the cylinder inner peripheral surface and the piston 10 is reinforced by the metal reinforcing member 12, the corner portion of the piston 10 is not chipped, The same piston 10 can be used again after the piston boot 18 has been replaced.

In this embodiment, the metal reinforcing member 12 is formed only on the corner portion of the piston body 11 on the pressure receiving surface side of the brake fluid pressure, but the entire pressure receiving surface of the brake fluid pressure is reinforced by the reinforcement member. You may. As a method of manufacturing such a piston, the piston body 11 and the metal reinforcing member 12 may be integrally molded, or the piston body 11 may be molded and then the metal reinforcing plate 12 may be fitted therein. Further, in order to secure the strength of the portion of the piston that comes into contact with the brake pad, a metal reinforcing member may be provided at the portion that comes into contact with the brake pad.

In the present embodiment, a metal reinforcing member is provided at the corner of the brake fluid pressure receiving surface of the piston body to prevent the piston from chipping. However, in addition to this, an elastic material such as rubber is used. It may be provided at least at the corner of the piston body 10 on the pressure receiving surface side of the brake fluid pressure. In this case, even if twisting occurs between the cylinder inner peripheral surface and the piston 10 when the piston 10 is pulled out of the cylinder by air pressure, the portion of the piston 10 that contacts the cylinder inner peripheral surface is an elastic member. It is possible to prevent the piston 10 from being chipped due to elastic deformation of the twisted portion.

[0016]

According to the invention of claim 1, since the piston is made of resin, the weight of the piston can be reduced and the cost can be reduced, and at the time of maintenance which requires disassembly of the disc brake, the force is exerted by the air pressure. When the piston often pulls out from the cylinder, if a twist occurs between the cylinder inner peripheral surface and the piston, a reinforcing member is formed at the portion of the piston that contacts the cylinder inner peripheral surface. There is no risk of chipping and the piston can be reused even if the disc brake is disassembled.

Further, according to the second aspect of the present invention, since an elastic member is formed in a portion of the piston that comes into contact with the cylinder inner peripheral surface when twisting occurs between the cylinder inner peripheral surface and the piston, Since the elastic member absorbs the twist, there is no fear that the corner portion of the piston is chipped, and the piston can be reused.

[Brief description of drawings]

FIG. 1 is a front sectional view when a resin piston of the present invention is used in a general disc brake.

FIG. 2 is a front sectional view of a resin piston of the first embodiment of the present invention.

FIG. 3 is a front sectional view of a conventional resin piston.

[Explanation of symbols]

 10 ... Resin piston 11 ... Piston body 12 ... Metal reinforcing plate 13 ... Inner space 14 ... Cylinder body 15 ... Brake fluid introduction hole 16 ... Brake pad 17 ... ..Disc rotors 18 ... Piston boots

Front Page Continuation (72) Inventor Akihiro Katagiri 2-1, Asahi-cho, Kariya City, Aichi Aisin Seiki Co., Ltd.

Claims (2)

[Claims] 1. A resin piston used for a disc brake, wherein a metal reinforcing member is formed at least at a corner portion of the resin piston on a pressure receiving surface side of a brake fluid pressure. 2. A resin piston used for a disc brake, wherein an elastic member is formed at least at a corner portion of the resin piston on the pressure receiving surface side of the brake fluid pressure.