GB2077882A

GB2077882A - Cup sealing rings for master cylinder pistons

Info

Publication number: GB2077882A
Application number: GB8117613A
Authority: GB
Original assignee: Aisin Seiki Co Ltd
Current assignee: Aisin Corp
Priority date: 1980-06-12
Filing date: 1981-06-09
Publication date: 1981-12-23
Also published as: GB2077882B; JPS574447A; JPS629468B2

Abstract

Piston 6 of a brake or clutch master cylinder is provided with a cup seal 21 or 22, which has a halogenated outer surface. This reduces noise due to vibration caused by friction of the cup seal sliding within the cylinder. <IMAGE>

Description

SPECIFICATION Sealing cups for master cylinders The present invention relates to sealing cups for vehicle master cylinders which may be used in hydraulic braking systems or hydraulic clutch release systems, and more particularly to sealing cups in such master cylinders made of synthetic resin material.

It is important in such master cylinders to decrease the sliding friction or resistance of the cup seal that is provided between the piston and cylinder wall, thereby reducing vibration and noise due to friction, without any loss of the sealing effect. To this end, the prior art has in general attemped to improve the configuration of the cup seal, so that several types of cup seal have been developed. The problem of noise still however remains.

The invention provides a sealing cup for providing a seal between a piston and a master cylinder in which it is slidable, which sealing cup has a halogenated layer on the outer surface thereof. The invention also provides a master cylinder having one or more such sealing cups between a piston and cylinder thereof, the cylinder wall being preferably made of a synthetic resin material. The surface halogenation of the sealing cups reduces noise by surface hardening the sealing cup and reducing its coefficient of friction.

Drawing The sole figure of the drawing is an axial section through a master cylinder according to the invention. The master cylinder 1 of the drawings is made of synthetic resin material and comprises a cylinder body 2 and a reservoir 3 for working fluid.

From the drawing, the operative parts of the master cylinder 1 will be immediately familiar to those skilled in the art, and need not be described in this Specification.

A piston 6 is axially slidable in an internal bore 5 in the cylinder body 2, and between the piston 6 and the bore 5 a seal is created by two sealing cups 21 and 22. The sealing cups 21 and 22 may be made of styrene-butadiene rubber (SBR) or ethylene-propylene copolymer (EPDM), and at least one of them has been subjected to a surface halogenation treatment as later described. This increases the surface hardness of the cup seal and decreases its coefficient of friction.

The surface halogenation may be achieved by a free radical or ionic reaction mechanism, and the halogen may be any halogen but is advantageously fluorine, chlorine or bromine. The preferred halogen is chlorine or bromine because the halogenation reaction tends to proceed at a greater reaction velocity. The halogenation may be a substitution reaction with hydrogen atoms or reactive groups such as sulphonic acid groups of the material from which the sealing cup is formed, but is preferably an addition reaction with carboncarbon double bonds.

The halogenation should be sufficient to provide a halogen content of from 5% to 20% to a depth of from 5 sl to 1 5 S. A suitable halogenation procedure is as follows: chlorine or bromine is dissolved in water to a concentration of from 0.3 to 1.0 g/1 00 mole of water, and the sealing cup is totally immersed therein at room temperature for from 5 to 20 minutes. The resulting sealing cup has a halogenated surface with a halogen distribution of about 5% to 20%, preferably about 8%. The sealing cup is increased in surface hardness and has a reduced coefficient of friction.

The noise level of the sealing cup in use was measured, and was 35 dB as compared with 57 dB when tested under identical conditions before the surface halogenation treatment. It is noted that the hardened surface of the sealing cup provides a smooth sliding action over the bore 5 of the cylinder body 3 even when the resilient deformation of the seal takes place due to the pressure of the working fluid. This smooth sliding of the sealing cup is assisted by its lowered coefficient of friction, so that noise due to frictional vibration is reduced.

1. A sealing cup for providing a seal between-a piston and a master cylinder in which it is slidable, which sealing cup has a halogenated layer on the outer surface thereof.

2. A sealing cup according to claim 1, in which the halogenated layer on said cup seal is from 5 ,tx to 12 y in thickness and has a halogen content of from 5% to 20%.

3. A sealing cup according to claim 1 or claim 2, made from moulded styrene-butadiene rubber (SBR) or ethylene, propylene co-polymer (EPDM).

4. A sealing cup according to any preceding c!aim, wherein the halogenated surface layer has been obtained by dipping the sealing cup in a solution of from 0.3 g to 1.0 g of chlorine or bromine in 100 mole of water for from 5 to 20 minutes at ambient temperature.

5. A master cylinder having one or more sealing cups according to any preceding claim between a piston and cylinder thereof.

6. A master cylinder according to claim 5, wherein the cylinder wall is made of a synthetic resin material.

7. A master cylinder substantially as described herein with reference to the drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Sealing cups for master cylinders The present invention relates to sealing cups for vehicle master cylinders which may be used in hydraulic braking systems or hydraulic clutch release systems, and more particularly to sealing cups in such master cylinders made of synthetic resin material. It is important in such master cylinders to decrease the sliding friction or resistance of the cup seal that is provided between the piston and cylinder wall, thereby reducing vibration and noise due to friction, without any loss of the sealing effect. To this end, the prior art has in general attemped to improve the configuration of the cup seal, so that several types of cup seal have been developed. The problem of noise still however remains. The invention provides a sealing cup for providing a seal between a piston and a master cylinder in which it is slidable, which sealing cup has a halogenated layer on the outer surface thereof. The invention also provides a master cylinder having one or more such sealing cups between a piston and cylinder thereof, the cylinder wall being preferably made of a synthetic resin material. The surface halogenation of the sealing cups reduces noise by surface hardening the sealing cup and reducing its coefficient of friction. Drawing The sole figure of the drawing is an axial section through a master cylinder according to the invention. The master cylinder 1 of the drawings is made of synthetic resin material and comprises a cylinder body 2 and a reservoir 3 for working fluid. From the drawing, the operative parts of the master cylinder 1 will be immediately familiar to those skilled in the art, and need not be described in this Specification. A piston 6 is axially slidable in an internal bore 5 in the cylinder body 2, and between the piston 6 and the bore 5 a seal is created by two sealing cups 21 and 22. The sealing cups 21 and 22 may be made of styrene-butadiene rubber (SBR) or ethylene-propylene copolymer (EPDM), and at least one of them has been subjected to a surface halogenation treatment as later described. This increases the surface hardness of the cup seal and decreases its coefficient of friction. The surface halogenation may be achieved by a free radical or ionic reaction mechanism, and the halogen may be any halogen but is advantageously fluorine, chlorine or bromine. The preferred halogen is chlorine or bromine because the halogenation reaction tends to proceed at a greater reaction velocity. The halogenation may be a substitution reaction with hydrogen atoms or reactive groups such as sulphonic acid groups of the material from which the sealing cup is formed, but is preferably an addition reaction with carboncarbon double bonds. The halogenation should be sufficient to provide a halogen content of from 5% to 20% to a depth of from 5 sl to 1 5 S. A suitable halogenation procedure is as follows: chlorine or bromine is dissolved in water to a concentration of from 0.3 to 1.0 g/1 00 mole of water, and the sealing cup is totally immersed therein at room temperature for from 5 to 20 minutes. The resulting sealing cup has a halogenated surface with a halogen distribution of about 5% to 20%, preferably about 8%. The sealing cup is increased in surface hardness and has a reduced coefficient of friction. The noise level of the sealing cup in use was measured, and was 35 dB as compared with 57 dB when tested under identical conditions before the surface halogenation treatment. It is noted that the hardened surface of the sealing cup provides a smooth sliding action over the bore 5 of the cylinder body 3 even when the resilient deformation of the seal takes place due to the pressure of the working fluid. This smooth sliding of the sealing cup is assisted by its lowered coefficient of friction, so that noise due to frictional vibration is reduced. CLAIMS