Abstract: A refrigerating machine oil composition for vapor compression type refrigerating machines is disclosed which can be used with either of HCFC refrigerants and HFC refrigerants. The inventive machine oil composition comprises a polyol ester (ester compound) as a base oil. Furthermore, the base oil contains from 1.0 to less than 5.0% by weight of a phosphate, from 0.1 to 2.0% by weight of an alkyl phosphorothionate and/or an aryl phosphorothionate, and from 0.05 to 2.0% by weight of an epoxy compound. The composition is free from sludge formation and insufficient lubricity, which are drawbacks of the polyol ester, due to the synergistic effect of these additives. On the other hand, the inventive composition provides the desirable properties of a polyol ester base oil, namely, good compatibility with refrigerants, high electrical insulating properties, and low hygroscopicity.

Abstract: A camshaft for an internal combustion engine comprising a metal cam, a shaft inserted into a through hole formed in the cam and resin poured between the cam and the shaft to join them. The cam is formed with plural grooves which are formed in the inner periphery of the hole in parallel with the shaft and into which the resin is poured. The groove is formed fanwise so that a sectional shape of the groove is wider as it approaches the outer periphery of the cam. Thus, when the resin which is filled into the grooves at high temperature is cooled naturally and contracts, since the resin bites the cam, gap and failure of contact are not produced between the cam receiving rotational force and the resin when the camshaft is operated for the internal combustion engine.