| 摘要 |
PURPOSE:To effectively remove a backlash near the neutral position by making the groove width of the tooth space at the center of the rack teeth formed at the side section of the ball nut of a reduction device smaller than the groove width of the tooth space at other portions. CONSTITUTION:A sector shaft 111 fitted on the periphery of a rod member 103 has a pinion 111b on the outer periphery, and the pinion 111b is engaged with a rack 130a formed on the outer periphery of a driving member 130. The driving member 130, a driving groove 131a and a ball 130b form a ball nut system. The pitch of the rack 130a is constant piM (module), the tooth thickness of two teeth T1 at the center section is (A+B), the tooth thickness of two teeth T2 on the outside is (B+B), and A>piM/4>B. A backlash between the pinion 111b and the rack 130a is small at the neutral position, the sector shaft 111 is not rotated idly, and the steering characteristic with little backlash and the rigid feeling is obtained. |
