| abstract |
An electric power steering device having a resin gear used in a speed reduction gear mechanism and the resin gear used for the device, the speed reduction gear mechanism further comprising a drive gear (31) which is the resin gear integrally formed by fitting a resin part (43) having gear teeth (44) formed on the outer peripheral surface thereof to the outside of a metal core (43) and a drive gear (32) meshed with the driven gear. The resin part (43) of the resin gear is formed of a resin composition using, as a base resin, a polyamide resin containing 10 to 50 wt.% glass fibers of 5 to 9 μm in diameter, and has excellent wear resistance, durability, and dimensional stability. Grease on the meshed surfaces of the gears has such a composition that includes a thickener and a 3 to 10 wt.% wax of 70 to 130˚C n melting point or softening point in a base oil formed mainly of at least one type of oils selected from mineral oil, poly α-olefin oil, alkylpolyphenylether. |