MOTOR-DRIVEN POWER STEERING SYSTEM

摘要

PROBLEM TO BE SOLVED: To provide a motor-driven power steering system having a low-cost reduction gear that can smoothly transmit torque for generating steering assist force. SOLUTION: Steering assist torque generated by a motor-driven actuator is transmitted to a steering shaft through a reduction gear 10. The gear 10 is constituted by integrating a synthetic resin tooth part 10a on the outer peripheral side and a metal sleeve 10b on the inner peripheral side. The tooth part 10a is formed by machining synthetic resin tooth part material 10a' integrated with the sleeve 10b. The sleeve 10b is covered with a chemical conversion coat 11. Humidity conditioning treatment is applied to the synthetic resin tooth part material 10a' so as to absorb moisture in the state of being integrated with the sleeve 10b covered with the coat 11.