ELECTRIC POWER STEERING DEVICE

摘要

PROBLEM TO BE SOLVED: To transmit power of a reduction gear of an electric power steering device with high efficiency. SOLUTION: The electric power steering device transmits an auxiliary output by an electric motor to a steering mechanism of a vehicle via a reduction gear mechanism comprising a worm 8 and a worm wheel 7. The worm wheel comprises a metallic core pipe and a resin section integrated with this. Gear teeth 202 are formed on the outer periphery of the resin section. An engaging section of the worm with the worm wheel is lubricated with grease composition. The relation of shearing rate X(s-1) to apparent viscosity Y(Pas) at 25°C of the grease composition is within a region sandwiched by two curves expressed by Y=492.01×X-0.9713and Y=421.19×X-0.5063. COPYRIGHT: (C)2006,JPO&NCIPI