JPH0330025B2 - - Google Patents

Abstract

PURPOSE:To prevent damage of a square seal to roll back the piston or the internal walls of the cylinder by forming a hardened film of thermoplastics of no less than 1mum thick and thereby avoiding exposure of inorganic substance at the surfaces. CONSTITUTION:At the surface of a plastic piston 7 is formed a hardened layer 8 of no less than 1mum thick made of a thermoplastic resin as the matrix. Thereby the surface of piston is protected against corrosion by the brake liquid as well as the sealing material is prevented from damage, which assures well a much improved durability.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a resin piston for disc brakes, which includes a thermosetting resin containing an inorganic material such as glass fiber.

Recently, pistons made by adding inorganic materials such as glass fiber, mica, carbon fiber, and copper to thermosetting resins such as phenol resin have been used for disc brakes. Since polishing is performed, inorganic material 4 such as glass fiber from thermosetting resin 3 is exposed on the surface 2 of piston 1, and when the piston slides inside the cylinder, this exposed inorganic material 4 causes the piston to roll back. This caused damage to the corner seal and the inner wall of the cylinder.

Therefore, the present invention is to prevent the above-mentioned drawbacks by forming a cured film of thermosetting resin of 1 μm or more on the surface of the resin piston so that the inorganic material is not exposed from the surface.

An embodiment shown in FIGS. 2 and 3 will be described below. A resin piston 7 is slidably provided in a cylinder 6 formed in a carrier body 5.
A thermosetting resin 3 is used as a matrix, and an inorganic substance 4 is mixed therein.

Phenol resin is generally used as the thermosetting resin, but polyamide resin and other appropriate resins can also be used. In addition, as the inorganic material, suitable materials such as glass fiber, mica, carbon fiber, copper, etc. can be used, but 35% of glass fiber
When the content is ~50%, expansion of the piston can be suppressed.

This resin piston 7 has a hardened layer 8 of thermosetting resin used as a matrix of 1 μm or more formed on its surface.

Furthermore, an asbestos-based heat insulating plate 10 is fitted into the open end of the resin piston 7 on the pad 9 pressing side, and is brought into contact with the pad back plate 9a.

This heat insulating board 10 is made of asbestos with a weight ratio of 25% to 45%.
% and a molded body composed of 55% to 75% cement.

Note that 11 is a corner seal.

As described above, the present invention forms a hardened layer of thermosetting resin on the surface of the resin piston, so the piston surface is not damaged by brake fluid and the sealing material is not damaged, improving durability. can do.

Moreover, since the resin layers made of the same material are formed on the surface of the resin piston, they fit together and there is no fear of peeling off due to thermal expansion.

[Brief explanation of drawings]

Fig. 1 is a partially enlarged sectional view of a conventional resin piston, Figs. 2 and 3 show an embodiment of the present invention, and Fig. 2 is a sectional front view of a caliper body;
FIG. 3 is a partially enlarged sectional view of the resin piston. 3 is a thermosetting resin, 4 is an inorganic material, 7 is a resin piston, 8 is a hardened layer, and 10 is a heat insulating plate.

Claims (1)

[Claims] 1. In a resin piston containing an inorganic material such as glass fiber, mica, carbon fiber, copper, etc. in a thermosetting resin, a hardened layer of the thermosetting resin is applied to the surface of the piston.
A resin piston for disc brakes characterized by a thickness of 1μ or more.