SUPPORT STRUCTURE OF PINION SHAFT IN ELECTRICALLY-DRIVEN POWER STEERING SYSTEM

摘要

PROBLEM TO BE SOLVED: To prevent elasticity caused by temperature change and vibration caused by bearing looseness from giving an adverse effect on sensitivity of torque sensor and gear engagement of the worm gear reduction mechanism of a pinion shaft support structure for power driven steering system. SOLUTION: A steering input shaft 3 is connected to a pinion shaft 4 via a torsion bar 5 and a pinion 4a is engaged with a rack of a rack shaft 6 such that steering force and steering auxiliary force are transmitted to the wheel side. A sensor core 7b for the torsion bar 5 is fitted across the input shaft and the pinion shaft, which moves up and down in accordance with the difference of the rotation amount between the input shaft and the pinion shaft. The steering auxiliary force that acts upon output signals of the torque sensor is transmitted via engagement between worm 12 and the worm wheel 11. The pinion shaft is supported in the radial and thrust directions by the bearing portion within the gearbox 2 at the axial position between the sensor core and the worm wheel.