To provide a power assist device by which vehicles are made smaller and lighter.
The outer end of a spring 55 is fixed to a spring case 103 attached to the swing arm 102, 102 and the inner end thereof is fixed to a spring boss 104 placed at the center of a driving wheel 12. One end of the spring boss 104 is inserted into a hub 13 and the spring boss 104 is tied to the hub 13 by means of a one-way clutch 70. A follower bevel gear 56 engaging with a bevel gear 53 is formed integrally with the spring boss 104, and the spring boss 104 is rotatably supported by the spring case 103 through a bearing 105. The spring is disposed on a side of the driving wheel and the input shaft of the spring is combined with the axle of the driving wheel. The power assist device is therefore disposed integrally around the driving wheel, so that vehicles as well as the power assist device are made smaller and lighter.
HIGASHIKAITO ISAO
SATO KATSUMI
KOWADA MITSURU
Norimasa Shimoda
Katsuhiko Sumiyoshi
Tadanori Masanori
Toshitake Nozaki