Power transmission device for electric vehicle

Abstract

A power transmission device for a vehicle is comprised of a motor including a rotor shaft and a stator having an electromagnetic coil; an inverter configured to generate an alternating current, the inverter being connected with the coil to controllably rotate the rotor shaft relative to the stator; a gear set including an input shaft coupled with and rotated by the rotor shaft, an output shaft and gears so meshed as to transmit torque of the input shaft to the output shaft; and a grounding path electrically connecting a part of the gear set with a body of the vehicle, the part being so disposed as to have the input shaft electrically interposed between the part and the rotor shaft.

1 . A power transmission device for a vehicle comprising:
 a motor including a rotor shaft and a stator having an electromagnetic coil;   an inverter configured to generate an alternating current, the inverter being connected with the coil to controllably rotate the rotor shaft relative to the stator;   a gear set including an input shaft coupled with and rotated by the rotor shaft, an output shaft and gears so meshed as to transmit torque of the input shaft to the output shaft; and   a grounding path electrically connecting a part of the gear set with a body of the vehicle, the part being so disposed as to have the input shaft electrically interposed between the part and the rotor shaft.   
     
     
         2 . The power transmission device of  claim 1 , wherein the part is so disposed as to have the input shaft and one or more meshing pairs of the gears electrically interposed between the part and the rotor shaft. 
     
     
         3 . The power transmission device of  claim 1 , further comprising:
 a coupling drivingly interposed between the rotor shaft and the input shaft, the coupling being electrically interposed between the part and the rotor shaft.   
     
     
         4 . The power transmission device of  claim 1 , further comprising:
 one or more counter shafts intervening between the input shaft and the output shaft; and   a brush in slidable contact with one selected from the group consisting of the input shaft, the counter shafts and the output shaft and connected with the grounding path so as to electrically connect the part of the gear set with the body of the vehicle.   
     
     
         5 . The power transmission device of  claim 4 , further comprising:
 a casing carrying the gear set and being electrically connected with the grounding path; and   a lead line electrically connected with the brush and the casing.   
     
     
         6 . The power transmission device of  claim 4 , further comprising:
 an oil seal intervening between the gear set and the brush.   
     
     
         7 . The power transmission device of  claim 5 , further comprising:
 a brush chamber housing the brush; and   a breather communicating the brush chamber with an outside of the brush chamber.   
     
     
         8 . The power transmission device of  claim 1 , wherein the part is an end portion of any of the shafts. 
     
     
         9 . The power transmission device of  claim 1 , wherein the gear set includes a planetary gear set having a sun gear, pinions meshing with the sun gear, and a ring gear meshing with the pinions, and the part is the ring gear.