# US 10,480,546 B2 · Hydraulic cylinder

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- Number: US 10,480,546 B2
- Document ID: US10480546B2
- Status: Granted
- Kind: B2
- Application number: 15/509,651
- Filed: 2015-08-24
- Published: 2017-10-05
- Granted: 2019-11-19
- Earliest claimed: 2014-09-12
- Assignees: SMC Corporation
- Applicants: Smc Corporation
- Inventors: Hiroyuki Okuhira; Kenji Imai; Tatsunori Yanase
- Web page: https://patentgrep.com/patent/US10480546B2

## CPC

- F15B 15/1433: {End caps (F15B15/1438 takes precedence)}
- C25D 11/04: of aluminium or alloys based thereon
- F15B 15/1457: {Piston rods (F15B15/1447 takes precedence)}
- F16J 7/00: Piston-rods
- F15B 15/1461: {Piston rod sealings}
- F15B 2215/305: characterised by the use of special materials
- F15B: SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- C25D: PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- F16J: PISTONS {(specially adapted for dampers F16F9/32)}; CYLINDERS; SEALINGS

## Abstract

A piston rod and a rod cover which constitute this hydraulic cylinder are configured from aluminum or an aluminum alloy. An alumite coating film is formed on at least a part of the inner wall surface of the rod cover that constitutes a rod insertion hole, and a diamond-like carbon coating film is formed on the outer wall surface of the piston rod, said diamond-like carbon coating film being in sliding contact with the alumite coating film.

## Claims

### Claim 1

A fluid pressure cylinder comprising:
a cylinder main body in which a cylinder hole is formed;
a piston disposed in the cylinder hole and which is displaced along an axial direction under an action of a working fluid;
a piston rod connected to the piston; and
a rod cover in which a rod insertion hole is formed through which the piston rod is inserted;
wherein the piston rod and the rod cover are constituted from aluminum or an aluminum alloy;
an alumite film or a diamond-like carbon film is formed on at least a portion of an inner wall surface of the rod cover constituting the rod insertion hole;
in the case that the alumite film is formed on the inner wall surface of the rod cover, a diamond-like carbon film that slides in contact with the alumite film is formed on an outer wall surface of the piston rod, whereas in the case that the diamond-like carbon film is formed on the inner wall surface of the rod cover, an alumite film that slides in contact with the diamond-like carbon film is formed on the outer wall surface of the piston rod;
an annular groove provided in the inner wall surface of the rod cover;
a rod packing provided in a portion of the annular groove; and
a lubricant provided in another portion of the annular groove, said another portion of the groove not having the rod packing, whereby said another portion of the groove comprises a lubricant accommodating groove wherein a length of the lubricant accommodating groove in the axial direction is between ⅕ and ⅘ of a length of the alumite film that slides in contact with the diamond-like carbon film,
wherein said another portion of the annular groove is located at a side of the rod packing which is opposite the piston along the axial direction.

### Claim 2 (depends on 1)

The fluid pressure cylinder according to claim 1, wherein:
the alumite film is formed on the inner wall surface of the rod cover; and
the diamond-like carbon film that slides in contact with the alumite film is formed on an outer wall surface of the piston rod.