PROBLEM TO BE SOLVED: To effectively prevent heat from generating from teeth of a worm wheel.;SOLUTION: In the worm wheel 1 having a plurality of teeth 2 engaged with a worm on an outer periphery, portions getting non-engaged contact with the worm are formed on an approximately central part 2a and both ends 2b and 2c of the teeth 2 at a tooth-width direction so that crowning is applied on the teeth 2 from an approximately central part 2a to both ends 2b and 2c at a tooth-width direction. Lubricant for reducing frictional resistance while engaging each other is filled in portions getting non-engaged contact with the worm formed on the approximately central part 2a at a tooth-width direction and its vicinity of the worm wheel 1.;COPYRIGHT: (C)2005,JPO&NCIPI
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