Master cylinder

Patent metadata

Field	Value
Publication number	US-10183657-B2
Application number	US-201414763883-A
Country	US
Kind code	B2
Filing date	Jan 29, 2014
Priority date	Jan 31, 2013
Publication date	Jan 22, 2019
Grant date	Jan 22, 2019

Abstract

A master cylinder includes a piston seal installed in a circumferential groove. The piston seal includes an annular base section, an inner circumferential lip section protruding from an inner circumferential side of the base section to come in sliding contact with an outer circumferential surface of a piston, an outer circumferential lip section protruding from an outer circumferential side of the base section to abut the circumferential groove, and an intermediate protrusion section protruding from between the inner circumferential lip section and the outer circumferential lip section of the base section to a forward side of the outer circumferential lip section. A step difference section is formed at the outer circumferential side. The circumferential groove has a step section that always abuts an outer circumferential surface of the step difference section. A communication path configured to bring a supply path that is in communication with a reservoir and the bottom section side of the circumferential groove in communication with each other is formed between the step difference section and the step section.

First claim

The invention claimed is:

1. A master cylinder comprising:
a cylinder main body having a bottomed cylindrical shape including an ejection path of a brake fluid and a supply path in communication with a reservoir;
a piston movably disposed in the cylinder main body and configured to form a pressure chamber formed to supply a fluid pressure to the ejection path between the piston and the cylinder main body; and
a piston seal installed in a circumferential groove formed in the cylinder main body such that an inner circumference thereof comes in sliding contact with the piston to seal between the supply path and the pressure chamber,
wherein the piston seal comprises:
an annular base section,
an inner circumferential lip section projecting from the annular base section and being in slidable contact with an outer circumferential surface of the piston,
an outer circumferential lip section projecting from the annular base section and abutting the circumferential groove of the cylinder main body,
wherein a step difference section that is long in a cylinder axial direction at an inner circumferential side of the annular base section is formed at an outer circumferential side of the annular base section,
wherein the circumferential groove has a step section at a circumferential wall of an opening section side of the cylinder main body, wherein the step section has a large diameter wall surface that is provided at a side closer to a groove bottom section in a cylinder radial direction and is configured of a surface parallel to a plane orthogonal to a cylinder axis, an inner circumferential wall surface that is provided inside of the large diameter wall surface in the cylinder radial direction and extends in the cylinder axial direction closer to the opening section side of the cylinder main body than the large diameter wall surface, and a small diameter wall surface that is provided inside of the inner circumferential wall surface in the cylinder radial direction and is configured of a surface parallel to a plane orthogonal to the cylinder axis, and
wherein a length of an overlapping region in the cylinder axial direction between an outer circumferential surface of the step difference section of the annular base section and the inner circumferential wall surface of the step section of the circumferential wall is larger than a movable distance of the piston seal in the cylinder axial direction in the circumferential groove of the cylinder main body.

2. The master cylinder according to claim 1 , wherein the piston seal further comprises an intermediate protrusion section projecting from between the inner circumferential lip section and the outer circumferential lip section of the annular base section to a forward side of the outer circumferential lip section, and
the inner circumferential lip section is bent in a direction approaching the intermediate protrusion section in response to a pressure state between the pressure chamber and the supply path to bring the supply path and the pressure chamber in communication with each other.

3. The master cylinder according to claim 1 , wherein the piston seal is configured such that the inner circumferential wall surface of the annular base section becomes spaced apart from the outer circumferential surface of the piston at a time of a basic state serving as a non-braking state before a brake pedal configured to move the piston is manipulated.

4. The master cylinder according to claim 1 , wherein the piston seal further comprises an intermediate protrusion section projecting from between the inner circumferential lip section and the outer circumferential lip section of the annular base section to a forward side of the outer circumferential lip section,
wherein another step section in which an outer circumferential surface of the intermediate protrusion section abuts is formed at the circumferential wall of a bottom section side of the circumferential groove of the cylinder main body, and
wherein a plurality of communication sections configured to bring the bottom section side of the circumferential groove in communication with the pressure chamber are formed at a front end side of the intermediate protrusion section to be spaced apart from each other in the circumferential direction.

5. The master cylinder according to claim 1 , wherein a cutout section that is longer in the cylinder axial direction at the outer circumferential side than at an inner circumferential side is formed at the inner circumferential side surface of the annular base section.

6. A master cylinder comprising:
a cylinder main body having a bottomed cylindrical shape including an ejection path of a brake fluid and a supply path in communication with a reservoir, the cylinder main body into which a piston is movably disposed; and
a piston seal installed in a circumferential groove formed in the cylinder main body such that an inner circumference thereof comes in sliding contact with the piston,
wherein the piston seal comprises:
an annular base section,
an inner circumferential lip section projecting from the annular base section and being in slidable contact with an outer circumferential surface of the piston,
an outer circumferential lip section projecting from the annular base section and abutting the circumferential groove of the cylinder main body,
an intermediate protrusion section projecting from between the inner circumferential lip section and the outer circumferential lip section of the annular base section to a forward side of the outer circumferential lip section, and
a step difference section that is long in a cylinder axial direction at an inner circumferential side of the annular base section is formed at an outer circumferential side of the annular base section,
wherein the circumferential groove has a step section at a circumferential wall of an opening section side of the cylinder main body, wherein the step section has a large diameter wall surface that is provided at a side closer to a groove bottom section in a cylinder radial direction and is configured of a surface parallel to a plane orthogonal to a cylinder axis, an inner circumferential wall surface that is provided inside of the large diameter wall surface in the cylinder radial direction and in the cylinder axial direction closer to the opening section side of the cylinder main body than the large diameter wall surface, and a small diameter wall surface that is provided inside of the inner circumferential wall surface in the cylinder radial direction and is configured of a surface parallel to a plane orthogonal to the cylinder axis, and
wherein a length of an overlapping region in the cylinder axial direction between an outer circumferential surface of the step difference section of the annular base section and the inner circumferential wall surface of the step section of the circumferential wall is larger than a movable distance of the piston seal in the cylinder axial direction in the circumferential groove of the cylinder main body.

7. The master cylinder according to claim 6 , wherein a pressure chamber is formed between the cylinder main body, the piston seal, and the piston, and
the inner circumferential lip section is bent in a direction approaching the intermediate protrusion section in response to a pressure state between the pressure chamber and the supply path to bring the supply path and the pressure chamber in communication with each other.

8. The master cylinder according to claim 6 , wherein the piston seal is formed such that the inner circumferential wall surface of the annular base section becomes spaced apart from the outer circumferential surface of the piston at a time of a basic state serving as a non-braking state before a brake pedal config

Assignees

• Hitachi Automotive Systems Ltd

Inventors

• Matsumura Sadatomo
• Kumemura Yoichi

Classifications

• B60T11/232 Primary

  Recuperation valves · CPC title

• B60T11/236 Primary

  Piston sealing arrangements · CPC title

• B60T11/20

  Tandem, side-by-side, or other multiple master cylinder units · CPC title

• F16J1/001

  One-piece pistons · CPC title

• F16J15/32

  with elastic sealings, e.g. O-rings · CPC title