US3545415A - Valve lifter with thin plastic coating - Google Patents

Description

United States Patent Yoahio Mori inventor Tokyo, Japan Appl. No. 719,371 Filed April 8, 1968 Patented Dee. 8, 1970 Assignee Nippon Piston Ring Co., Ltd.

Tokyo, Japan Priority April 8, 1967 Japan VALVE LIFTER WITH THIN PLASTIC COATING 2 Claims, 1 Drawing Fig.

US. Cl.

Int. Cl. .4 F24c 3/00 Field 01' Search 74/569;

Primary Examiner-Benjamin W. Wyche, III AltomeySughrue, Rothwell, Mion, Zinn & MacPeak ABSTRACT: A valve lifter having mutually sliding surfaces requiring little or no lubrication, wherein at least one of said surfaces is coated with polytetrafluoroethylene.

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1 VALVE LIFTER WITH THIN PLASTIC COATING BACKGROUND OF THE INVENTION This invention relates to construction of an improved valve lifter, particularly to a valve lifter for easy use in combustion engines.

Lubricating oil is normally supplied on theface where the valve lifter makes contact with the cam face and on the sliding surfaces where the valve lifter slides against a guide. It is usually necessary to wet the sliding parts of the valve lifter with a lubricating oil spread over the contactsurfaces of metal at the start of the engine operation. Until the surfaces are adequately lubricated, scuffing, friction loss will occur. Engine performance is therefore substantially reduced at the start of its operation and considerable scuffing and abrasion by its sticking may result during these relatively brief periods. The

problem has now become magnified with the advent of hard. alloy-metal valve lifters for high speed rotation, since the harder the material is, the more abrasion and scuffing will occur at the beginning of the engines operation.

BRIEF DESCRIPTION OF THE DRAWING The FIG. is a sectional side elevationof a valve lifter wherein the sliding surfaces are coated with polytetrafiuoroethylene.

SUMMARY OF THE INVENTION DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The drawing illustrating the invention is a sectional side elevation of the valve lifter and the cam, numeral 1 is the valve lifter, numeral 2 is the cam, numeral 3 is the cylinder block. The valve lifter, the cam and the sliding contact surface between the valve lifter and the mating guide portion are coated with polytetrafluoroethylene. The coating may be put on either the valve lifter and the cam or the contact surface of the valve lifter and the mating guide portion, since the polytetrafluoroethylene coated on one surface will partly adhereto the surfaces contacted therewith forming a film of the resin on the latter during the sliding contact. In the embodiment shown, the resin is coated onto the surface 4 and 5, whereby these surfaces contact with surfaces 4' and 5' respectively and a film of the resin is formed on the surfaces 4' and The thickness of the film of polytetrafluoroethylene is not critical but it in general should be between about 5-300 (p. microns). The full effect however, will not be obtained if the thickness is under 5p. Over 300p. the film often is loosened and might be removed by the sliding contact. Preferably, the thickness of the resin for the valve lifter of the combustion engine for automobile,is about 10p.

The coating of polytetrafluoroethylene resin can be achieved by well known methods, i.e., flowing, spraying, enameling etc., but best results are obtainable by spraying. Spraying is accomplished as follows: The valve lifter, cam, and

mating guide portion are demated and their surfaces cleaned with water, liquid honed, and cleaned again with water to make it easier to adhere the resin. These are dried in the air. The aperture of the spray gun is suitably about 0.8-1.0 mm. The coating liquid is made by using water, thinner or other so]- vents. The coating liquid should be, agitated and passed through a filter of 100-200 mesh stainless wire. It is preferable to operate at the condition of 2-3 kg./cm. spray pressure and at 1520 cm. distance from the surface to be coated.

A suitable exhaust system IS arranged in the place where the spraying is done and where it is kept clean without suspended matter such as dust.

After spraying, the member isdried under 90 C. Infrared rays may be used for heating. Rapid drying should be avoided to protect the film from forming wrinkles and cracking.

The member is them put into a furnace and baked at a temperature of 350--400 C., and quenched whereby the film is made tenacious. The film of resin may be provided either on the surface 4 and 5 or on the surface 4' and 5, but it easier in operation to coat it on the surface 4 and 5 than 4' and 5'.

Polytetrafluorethylene applied to the invention has a very small coefficient of friction, and also is so lubricous that it fully functions as a lubricant even if lubricating oil is not supplied. Therefore, it does no happen that scuffing is caused at the contact surface of the valve lifter and the cam at the beginning of the running of the engine; also friction loss between the lifter and the guide is minimized.

In this way, a stable sliding between the surfaces is made possible providing a more fully effective engine even from the start of engine operation,

This invention can be adapted to the construction of any of various shapes and qualities of valve lifter i.e., it is applicable in the construction of valve lifter comprised as follows:

1. In an internal combustion engine having a rotating cam and a driven valve lifter having surfaces adapted for sliding contact with said rotating cam and with the block of said internal combustion engine, the improvement comprising a coating on at least one of said surfaces composed of a film of polytetrafiuoroethylene having a thickness of from 5 to 300p..

2. The improved valve lifter as in claim 1, wherein the thickness of said film is about 10 microns.

in air or heated in air.

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