| 摘要 |
PROBLEM TO BE SOLVED: To provide a worm gear speed reducer capable of reducing torque fluctuation while allowing an assembly error or machining error, and a steering device including the worm gear speed reducer.SOLUTION: In a worm gear speed reducer 19, the relation between an outer diameter D1 of a worm 20 and an outer diameter D2 of a hob for cutting a worm wheel 21 and forming a tooth groove 42 satisfies the following formula (1): 3≥D2/D1≥1.7; and the relation between a pressure angle α of the worm wheel 21 and a pressure angle β of the worm 20 on an engagement pitch circle P of the worm 20 and worm wheel 21 satisfies the following formula (2): 0.1 degrees≤α-β≤0.5 degrees.SELECTED DRAWING: Figure 4 |
