JPH0752432Y2 - Resin piston for vehicle disc brake - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin piston for a vehicle disc brake, and more particularly to a resin piston having improved braking feeling and durability.

[0002]

2. Description of the Related Art A resin piston is lighter than a metal piston, but has a low rigidity. Therefore, for example, as shown in JP-A-58-21783, a cylindrical peripheral wall has a thick wall. Also, a bottom wall defining a hydraulic chamber with the bottom wall of the cylinder hole of the caliper is integrally formed closer to the disc rotor than the end of the hydraulic chamber, and the bottom wall bulges toward the hydraulic chamber. It is formed into a spherical shape to reduce the deformation of the bottom wall due to hydraulic pressure.

[0003]

However, in the above-mentioned structure, the spherical bottom wall is formed by an arc whose center is at a position closer to the hydraulic chamber than the friction pad contact portion of the resin piston. Therefore, the deformation of the bottom wall is small at the time of hydraulic operation, but the peripheral wall on the friction pad abutment side is deformed due to compression, the amount of liquid loss in the hydraulic chamber is increased, and the braking feeling becomes rigid. There will be nothing.

Further, when the piston moves to the disc rotor side due to the abrasion of the friction pad and the bottom wall of the piston is located closer to the disc rotor side than the piston seal, hydraulic stress is applied to the continuous portion of the bottom wall and the peripheral wall. Concentrate and reduce the durability of the piston.

In view of this, the present invention reduces deformation during hydraulic operation to reduce the amount of liquid loss in the hydraulic chamber so that a braking feeling with a sense of rigidity can be obtained.
An object of the present invention is to provide a resin piston for a vehicle disc brake, in which stress applied to a continuous portion of a piston bottom wall and a peripheral wall is dispersed to improve durability.

[0006]

In order to achieve the above object, the present invention is to integrally form a bottom wall in a cylindrical peripheral wall closer to the disk rotor than to the end portion on the hydraulic chamber side, and to form the bottom wall by hydraulic pressure. In a resin piston for a vehicle disc brake that is formed in a spherical shape that bulges toward the chamber side, the hydraulic chamber side surface of the bottom wall has a spherical shape whose radius is from the center point of the friction pad contact portion to the outer circumference of the peripheral wall. It is characterized in that the continuous portion from the side surface of the hydraulic chamber to the peripheral wall is formed thicker than the peripheral wall.

[0007]

[Operation] With this configuration, since the center point of the spherical bottom wall is the center point of the friction pad contact portion, deformation of the bottom wall during hydraulic operation and deformation of the peripheral wall on the friction pad contact portion side are reduced. As a result, the rigidity is increased and the braking feeling is improved. Further, since the continuous portion of the piston bottom wall and the peripheral wall is formed thick, the stress applied there is dispersed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In the caliper 2 of the disc brake 1, the action portion 2a and the reaction portion 2b are connected by a bridge portion 2c straddling the outer periphery of the disc rotor 3, and the resin piston 4 is inserted into a cylinder hole 2d formed in the action portion 2a. Is movably fitted and held liquid-tightly by a piston seal 5, and friction pads 6, 6 facing each other on both sides of the disk rotor 3 are hung by a hanger pin 7, and a slide provided on a bracket 8 is mounted. It is supported by the moving pin 9 so as to be movable in the axial direction of the disc rotor 3.

The resin piston 4 is integrally formed with a bottom wall 4b defining a hydraulic chamber 10 between the bottom wall 2e of the cylinder hole 2d and a cylindrical peripheral wall 4a.

In the bottom wall 4b, the hydraulic chamber side surface 4c is formed into a spherical shape having a radius from the center point of the contact portion of the friction pad 6 of the resin piston 4 to the outer circumference of the peripheral wall 4a, and the friction pad side surface 4d.
Are formed in a spherical shape having a radius from the center point of the contact portion of the friction pad 6 of the resin piston 4 to the inner circumference of the peripheral wall 4a.

In the bottom wall 4b, the continuous portion 4e of the hydraulic chamber side surface 4c and the peripheral wall 4a is made thicker than the peripheral wall 4a, and in this embodiment, the radius is about 12 to 20% of the outer diameter of the piston. It is formed on a curved surface.

With this structure, the bottom wall 4b
Is formed to have the same thickness in a hemispherical shape centered on the center point of the friction pad 6 contact portion, so that the deformation of the bottom wall 4b at the time of hydraulic operation is reduced, and the peripheral wall on the friction pad 6 contact portion side is reduced. 4a
Deformation due to compression is also reduced.

Therefore, the amount of hydraulic fluid loss in the hydraulic chamber 10 is reduced, and a braking feeling with a sense of rigidity can be obtained.

Further, the side surface 4c of the hydraulic chamber of the bottom wall 4b and the peripheral wall 4
By forming the continuous portion 4e with a thicker, the resin piston 4 moves to the disk rotor 3 side as the friction pads 6 and 6 wear, and the hydraulic chamber side surface 4c of the bottom wall 4b of the resin piston 4 moves. Even if is located closer to the disk rotor 3 side than the end of the piston seal 5 on the hydraulic chamber side, the stress applied to the continuous portion 4e can be dispersed, so the durability of the resin piston 4 can be improved.

[0016]

As described above, in the present invention, in the resin piston in which the bottom wall is formed in a spherical shape that bulges toward the hydraulic chamber side, the side surface of the bottom wall hydraulic chamber from the center of the friction pad contact portion Formed into a spherical shape having a radius to the outer circumference of the peripheral wall, and the continuous portion from the hydraulic chamber side surface to the peripheral wall is formed to be thicker than the peripheral wall, so that deformation of the bottom wall during hydraulic operation, Deformation of the peripheral wall on the friction pad abutment side is reduced, the amount of hydraulic loss in the hydraulic chamber is reduced, and a braking feeling with a sense of rigidity is obtained, and the continuous portion of the piston bottom wall and peripheral wall is Since it is formed thick, the stress applied here is dispersed,
The durability of the resin piston can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view of a disc brake showing an embodiment of the present invention.

FIG. 2 is a sectional view of the same resin piston.

[Explanation of symbols]

1 ... Disc brake, 2 ... Caliper, 2d ... Cylinder hole, 4 ... Resin piston, 4a ... Peripheral wall, 4b ... Bottom wall, 4c
... hydraulic chamber side surface, 4d ... friction pad side surface, 4e ... continuous portion,
6 ... Friction pad

Claims (1)

[Scope of utility model registration request] 1. A vehicle disc brake in which a bottom wall is integrally formed in a cylindrical peripheral wall closer to the disc rotor than to the hydraulic chamber side, and the bottom wall is formed into a spherical shape that bulges toward the hydraulic chamber side. In the resin piston, the side surface of the hydraulic chamber of the bottom wall is formed into a spherical surface having a radius from the center point of the friction pad contact portion to the outer circumference of the peripheral wall, and the side surface of the hydraulic chamber is continuous to the peripheral wall. A resin piston for a vehicle disc brake, wherein the portion is formed to be thicker than the peripheral wall.