WORM REDUCTION GEAR AND ELECTRIC POWER STEERING DEVICE USING THE SAME

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WORM REDUCTION GEAR AND ELECTRIC POWER STEERING DEVICE USING THE SAME

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YAMAUCHI MAI

PROBLEM TO BE SOLVED: To provide a worm reduction gear which can enlarge a pressing load of a worm shaft with respect to a worm wheel without enlarging a set load of an energization member and performing a dimensional change, and an electric power steering device using the worm reduction gear.SOLUTION: A worm reduction gear 17 includes a worm wheel 19 having an external peripheral face 43 at which a tooth part 19c is formed, a worm shaft 18, and an energization member 60. The worm shaft 18 has an engagement part 18d engaged with the tooth part 19c between a first end part 18a at an electric motor 16 side, and a second end part 18b opposite to the first end part 18a. A distance L2 between an engagement center B of the engagement part 18d and the second end part 18b is longer than a distance L1 between the engagement center B and the first end part 18a. The energization member 60 energizes the second end part 18b with the first end part 18a as a fulcrum so that an inter-core distance D1 between the worm wheel 19 and the worm shaft 18 becomes short.SELECTED DRAWING: Figure 2

【課題】付勢部材のセット荷重を大きくしたり寸法変更を行ったりすることなく、ウォームホイールに対するウォームシャフトの押付荷重を大きくすることができるウォーム減速機およびそれを備えた電動パワーステアリング装置を提供すること。【解決手段】ウォーム減速機１７は、歯部１９ｃが形成された外周面４３を有するウォームホイール１９と、ウォームシャフト１８と、付勢部材６０とを含む。ウォームシャフト１８は、電動モータ１６側の第１端部１８ａと第１端部１８ａとは反対側の第２端部１８ｂとの間で歯部１９ｃと噛み合う噛合部１８ｄを有する。噛合部１８ｄの噛合中心Ｂと第２端部１８ｂとの間の距離Ｌ２は、噛合中心Ｂと第１端部１８ａとの間の距離Ｌ１よりも大きい。付勢部材６０は、ウォームホイール１９とウォームシャフト１８との芯間距離Ｄ１が小さくなるように、第１端部１８ａを支点として第２端部１８ｂを付勢する。【選択図】図２