Machine element or mechanism – Elements – Cams
Patent
1996-09-26
1998-09-22
Solis, Erick R.
Machine element or mechanism
Elements
Cams
123 9051, 123 9035, F16H 5306
Patent
active
058098429
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to sliding members used on valve train system components in an automotive engine, sliding members such as cam followers and rocker arms and sliding members installed in hydraulic circuits in the engine and between driving components, and more particularly to sliding members that exhibit their effectiveness when used on tappets having a metal base and a ceramic sliding member joined together and on pistons of hydraulic circuits using the driving system of the engine.
BACKGROUND ART
Mechanical sliding parts, such as represented by automotive engine parts, often have a convex crowning shape on one of the mating sliding parts to prevent uneven wear or uneven contact due to poor alignment. Japan Patent Laid-Open No. 63-225728, for example, discloses a technology, in which a wear resistant member with a smaller thermal expansion coefficient than the metal base is heated and joined to the base metal to form a sliding face which is formed into a crowning shape because of a thermal expansion coefficient difference. This cited patent shows a method of providing a low-cost sliding part that can prevent uneven contact due to poor alignment during sliding motion by providing a crowning shape without resorting to machining such as grinding. The cited patent also discloses that the wear resisting member uses ceramic materials such as silicon nitride, silicon carbide and sialon.
In recent years, global environmental situations make the enforcement of more stringent regulations on automotive emissions an urgent issue and, in diesel engine in particular, studies are under way to reduce nitrogen oxides (NOx) and particulate matters (P/M). One method to comply with this requirement currently being studied is to attach an EGR (exhaust gas recirculation) mechanism to the engine exhaust system to reduce NOx. This method, however, raises problems that recirculation of exhaust gas components chemically degrades the engine oil and that trapped particulate matters contaminate oil, leading to abnormal wear of the engine sliding parts.
To solve these problems, a provision of moderate crowning was proposed but it was not sufficient. In the case where a silicon nitride ceramic material with high wear resistance is used as a sliding face member, for example, if the crowning contour should deform with respect to the center line, the contact face and the contact face pressure during the sliding motion also change, causing uneven wear and fatigue wear such as pitting and fretting to the mated sliding part because the ceramic material has a higher hardness than the metal material of the mated sliding part.
The center line referred to here is a rotating axis about which the sliding part turns during operation.
The present invention is intended to provide a ceramic sliding component that has a crowning geometry or profile that will not cause uneven wear or fatigue wear.
DISCLOSURE OF THE INVENTION
The constitution of this invention that solves the above-mentioned problems is the sliding component as defined in the claims. In a sliding component in which a silicon nitride-based material as the sliding face member and a metal body with a greater thermal expansion coefficient than the sliding face member are joined together and in which the sliding face is formed into a shape of crown, the difference in the amount of crowning between two points that are axially symmetric with respect to the center line of the crowning contour is 10% or more and 50% or less with respect to an average value of the crowning at the two points. This will be explained taking an example case of a tappet in the diesel OHV engine shown in FIG. 1.
FIG. 1 shows a basic construction of a tappet, in which a sliding face member 1 made of silicon nitride-based material is rotated about the center line of the crowning contour of the sliding face member by a rotating force applied by a mating cam 2 that slides, offset by a specified amount, on the sliding face member thereby preventing uneven wear or uneven contact due to poor
REFERENCES:
patent: 3124869 (1964-03-01), Behnke et al.
patent: 3683876 (1972-08-01), Lesher
patent: 3875911 (1975-04-01), Joseph
patent: 4508067 (1985-04-01), Fuhrmann
patent: 4632074 (1986-12-01), Takahashi et al.
patent: 5035959 (1991-07-01), Ito et al.
patent: 5185923 (1993-02-01), Taniguchi et al.
Nishioka Takao
Takeuchi Hisao
Yamagiwa Masamichi
Yamakawa Akira
Solis Erick R.
Sumitomo Electric Industries Ltd.
LandOfFree
Ceramic sliding component does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ceramic sliding component, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ceramic sliding component will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1613128