This paper discusses the size reduction and performance enhancement for worm gears of a pinion assist type EPS system.
In conjunction with recent trends in vehicles getting larger and tires gaining larger footprints, the EPS motor assist torque has increased considerably. This leads to the issue involving enlargement of the external diameter of the worm gear and the worm wheel gear, which are reduction gears that boost motor torque.
In order to address this issue, the authors examined single-threaded worm gears, and fundamental factors that cause the enlargement of the worm gear external diameter from the standpoint of the working of the gear. After the details are explained, a new worm gear that addressed this issue is proposed.
This paper describes this worm gear, tooth form shape, and its construction.
Moreover, this worm gear was built, installed into an EPS system, and tested.
As a result, it was determined that in addition to increasing allowable torque and reversing efficiency, it was also possible to reduce the size of the worm wheel.