Patent ID: 8393424

Claim:
An in-wheel motor drive unit comprising: a motor portion to rotate and drive a motor side rotation member having an eccentric portion; a speed reduction portion to reduce rotation speed of said motor side rotation member and transmit the rotation of said motor side rotation member to a wheel side rotation member; a casing to hold said motor portion and said speed reduction portion; and a wheel hub fixedly connected to said wheel side rotation member, wherein said speed reduction portion includes: a revolution member having a through hole for the insertion of said eccentric portion to make a revolution movement around a rotation axis of said motor side rotation member in conjunction with a rotation thereof, a circumference engagement member to engage with a circumference of said revolution member to generate a rotation movement of said revolution member; a circumference engagement member holding portion fixedly fitted in an inner diameter surface of said casing holding the speed reduction portion, to hold said circumference engagement member parallel to the rotation axis of said motor side rotation member; and a motion conversion mechanism to convert the rotation movement of said revolution member to the rotation movement moving around the rotation axis of said motor side rotation member and transmit the rotation movement to said wheel side rotation member, and said circumference engagement member holding portion includes: a cylindrical portion; a pair of ring portions extending from axial both ends of said cylindrical portion to the radial inner side; and a pair of circumference engagement member holding holes provided at opposed positions of the pair of ring portions, and extending parallel to the rotation axis of said motor side rotation member to hold axial ends of said circumference engagement member; wherein said cylindrical portion has a revolution member insertion hole penetrating in a radial direction such that said revolution member can be inserted in the radial direction.