To shorten the axial length of a speed reduction unit which is coaxially arranged at a motor.
This speed reduction unit comprises: a first shaft 1 connected to the motor M; a first gear 2 arranged at the external periphery of the first shaft 1; a second gear 3 engaged with the first gear 2; a second shaft 4 which supports the second gear 3; a third gear 5 which is rotatably supported by the second shaft 4, and arranged at the motor M side with respect to the second gear 3; a clutch 6 which switches the transmission and the disconnection of rotation between the second shaft 4 and the third gear 5; and a differential device 7 which distributes the rotation of the third gear 5 to right and left wheels. The speed reduction gear also reduces the rotation of the motor M in speed in a connection with the clutch 6, and transmits the reduced rotation to the right and left wheels. An outer ring 30 of at least one bearing among bearings 37, 39 which rotatably support the end of the first shaft 1, and bearings 29, 40 which rotatably support the end of the second shaft 4 is constituted of a large-diameter part 31 and a small-diameter part 32 which is smaller than the large-diameter part 31 in outside diameter, and the outer ring 30 is fixed by pressing down the end face of the large-diameter part 31 by using a plate 35.
SAITO TAKAHIDE
YAMAGATA SATORU
HAMAI KYUGO
YAMAMOTO DAISUKE
OYAMA KAZUTO
MURAKAMI KAZUTOSHI
SHIMIZU AKIRA
HITACHI LTD
UNIVANCE CORP
Torii Kazuhisa
Takayoshi Tagawa
Yaichiro Nakatani