WORM REDUCTION GEAR FOR ELECTRIC POWER STEERING DEVICE, AND ELECTRIC POWER STEERING DEVICE WITH THE WORM REDUCTION GEAR BUILT THEREIN

摘要

PROBLEM TO BE SOLVED: To restrain occurrence of tooth hitting sounds harsh to the ear at an engagement section between a worm wheel 16 and a worm shaft 18 at low cost, to easily increase the inclination of the worm shaft 18 to a rotary shaft of an electric motor, and to effectively suppress an increase of the working torque of a worm reduction gear 7a.;SOLUTION: A fourth ball bearing 30 is directly externally fitted to and supported by a part close to a fore end of the worm shaft 18. A cylindrical space 67 is formed between an outer circumferential surface of an outer race 50 of the fourth ball bearing 30 and an inner circumferential surface of an elastic ring 66 internally fitted to a holder 36 fixed to a gear housing 14. In this condition, by imparting the elastic force of a torsional coil spring 21 in the worm shaft 18 via a pressurization pad 20, a section with the fourth ball bearing 30 being externally fitted partly in the axial direction of the worm shaft 18 is displaced in the approaching direction to a worm wheel 16 in a range of the sum of the thickness in the radial direction of the cylindrical space 67 and the compression in the radial direction of the elastic ring 66.;COPYRIGHT: (C)2007,JPO&INPIT