Driving apparatus for vehicle

#The present invention relates to a driving apparatus for vehicle, having an electric motor as a prime driving source (mover) for driving drive wheels.

#An electric vehicle employs the electric motor, namely, a motor as a prime mover, and a hybrid vehicle is one employing the electric motor and an internal combustion engine as a prime mover. In such a vehicle equipped with the electric motor as the prime mover, there are employed a driving apparatus, which is provided with: an electric motor; a speed reduction mechanism for reducing speeds of its rotor shaft; and a differential gear unit, namely, a differential mechanism, for absorbing the difference in rotation between left and right drive wheels in turning the vehicle. The electric motor, the speed reduction mechanism and the differential gear unit are incorporated in a case, so that power of the electric motor is transmitted to the drive wheels through a drive shaft coupling the differential gear unit and the left and right drive wheels.

#Examples of the driving apparatus used in the electric vehicle are disclosed in Japanese Patent Laid-open Nos. 10-278603 and 11-98616. The driving apparatus comprises: a rotor shaft concentric with a rotor of an electric motor; a reduction shaft provided with a first speed reduction gear train between this rotor shaft and another rotor shaft disposed in parallel thereto; and a differential gear unit provided with a final reduction driven gear, which is engaged with a final reduction drive gear fixed to the reduction shaft. The driving apparatus is therefore formed into a parallel three-shaft structure in which an axle shaft, the rotor shaft, and the reduction shaft are parallel to one another, the axle shaft being fixed to a bevel gear of the differential gear unit and coupled to a drive shaft.

#FIG. 1 is a cross-sectional view showing a driving apparatus for vehicle according to one embodiment of the present invention.

#FIG. 2A is a schematic view of the driving apparatus shown in FIG. 1.

#FIG. 2B is a cross-sectional view taken along the A-A line in FIG. 2A.

#A driving apparatus is mounted in an electric vehicle driving drive wheels only by electric power from a battery, or in a hybrid vehicle driving drive wheels by an internal combustion engine and an electric motor. For example, in the electric vehicle employing front wheels and rear wheels as drive wheels, two driving apparatus for front and rear wheels are respectively mounted on its vehicle. Meanwhile, in such a type of hybrid vehicle that its front wheels are driven by the internal combustion engine and its rear wheels are driven by the electric motor, the driving apparatus is mounted on its vehicle to drive the rear wheels.

#As shown in FIGS. 1, 2A and 2B, this driving apparatus has a unit case 11 comprising: a motor case 11a; a gear case 11b fixed to one side thereof; and a cover 11c fixed to the other side thereof, and this unit case 11 is mounted in the vehicle. A differential gear unit 12 is rotatably incorporated in the gear case 11b and has a differential case 14 provided with a reduction driven gear 13. The differential case 14 can be rotated by a ball bearing 15 incorporated in the gear case 11b and a ball bearing 16 incorporated in the motor case 11a.

#In the differential case 14, there are rotatably incorporated: a bevel gear, that is, a side gear 18a fixed to an axle shaft 17a coupled to one of the left and right drive wheels through a not-shown drive shaft; and a side gear 18b fixed to an axle shaft 17b coupled to the other of the drive wheels through a not-shown drive shaft. These side gears 18a and 18b are located opposite to each other. In the differential case 14, a pinion shaft 19 is fixed in a direction perpendicular to each rotational center axis of the axle shafts 17a and 17b. On the pinion shaft 19, bevel pinions, that is, pinion gears 20a and 20b facing each other and respectively engaged with the side gears 18a and 18b are rotatably mounted.