PINION SHAFT STRUCTURE AND ELECTRIC POWER STEERING DEVICE EQUIPPED WITH PINION SHAFT STRUCTURE

摘要

PROBLEM TO BE SOLVED: To provide a pinion shaft eliminating the restriction on a tooth cutting machine tool for fabricating a pinion to allow use of bearings having a large load capacity and provide an electric power steering device using the pinion shaft.;SOLUTION: A sleeve 12 with the peripheral surface subjected previously to a processing to suit a bearing raceway surface is fitted by pressure to the tip 11a of the pinion shaft as a bearing supporting part, and thereby bearing supporting part is formed. The outside diameter Da of the sleeve 12 is made greater than the diameter of the pitch circle without being restricted by the diameter D2 of the tooth bottom circle of the pinion to allow use of a bearing having a large load capacity, and further the end face of the sleeve 12 is contacted with the end face of the pinion 11 to allow the force in the bending direction generated in the pinion 11 to be transmitted to the sleeve 12, which allows avoiding stress concentration in a stepped part of the pinion 11. Use of this pinion shaft in an electric power steering device allows achieving one equipped with a longer bearing lifetime than in the conventional arrangement.;COPYRIGHT: (C)2006,JPO&NCIPI