Bearing for Rocker Arm

Abstract

A bearing for a rocker arm includes a shaft corresponding to an inner race fixed to a rocker arm interposed between an engine valve and a cam to adjust intake and exhaust, an outer race 4 in contact with the cam, located outer to the inner race, and a plurality of needle rollers located between the outer race and the inner race. The outer race includes a nitrogen-enriched layer. The grain size number of austenite crystal grains in the nitrogen-enriched layer is in a range exceeding No. 10. The outer race outside cylindrical surface has random small concave pits.

Description

TECHNICAL FIELD [0001] The present invention relates to a bearing used in a rocker arm employed for opening / closing an intake valve or exhaust valve of a motor engine. More specifically, the present invention relates to a rocker arm bearing having a long lifetime with respect to peeling. BACKGROUND ART [0002] The approach of improving mileage is known by incorporating a rolling bearing in a rocker arm and forming contact between the outside cylindrical perimeter of the outer race and the cam of the engine to reduce the friction generated at the valve gear system. The full complement type roller bearing is used for recent rocker arm bearings when it is employed for opening / closing the engine intake valve and exhaust valve. The full complement type roller bearing is now often used in high speed and high load applications. Particularly, in such full complement type roller bearings absent of cages, interference occurs between rollers, and / or positioning of the rollers cannot be controll...

AI Technical Summary

Benefits of technology

The present invention relates to a rocker arm bearing used in engines that can open and close valves. The invention provides a solution to the problem of peeling damage on the outer race of the bearing, which occurs quickly and can cause the bearing to fail. The invention includes a nitrogen-enriched layer on the outer race of the bearing, small concave pits formed randomly at the surface of the outer race, and a ratio of axial surface roughness to circumferential surface roughness of at most 1.0. The invention also includes a method of improving the lubrication condition of the bearing by shot peening and retaining austenite. Overall, the invention provides a rocker arm bearing that can have a longer lifetime and better performance under severe conditions of usage.

Problems solved by technology

Particularly, in such full complement type roller bearings absent of cages, interference occurs between rollers, and / or positioning of the rollers cannot be controlled smoothly, resulting in the generation of roller skew.

Furthermore, the lubricant may not be supplied smoothly into the bearing, causing an event of poor lubrication.

This will induce sliding heat generation, local rise in contact pressure, insufficient lubrication, and the like.

Although the bearing has a great load capacity as well as sufficient lifetime with respect to the required lifetime from the numerical calculation perspective, surface damage (peeling, smearing, surface origin type flaking) and / or internal origin type flaking occurs in a short period of time of usage, whereby the bearing cannot function appropriately any longer.

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