Frictional engagement apparatus

摘要

A frictional engagement apparatus is provided. The frictional engagement apparatus includes a first frictional engagement unit, a second frictional engagement unit disposed axially spaced from the first frictional engagement unit, and one case that supports the first and the second frictional engagement units non-rotatably circumferentially but shiftably axially relative thereto. One retaining ring is fitted to the case so as to be located between the first and second frictional engagement units. The retaining ring is abutted to the nearest first friction plate and/or the second friction plate to stop an approaching shift of the first frictional engagement unit and/or the second frictional engagement units. The retaining ring includes a u-shaped cross section defined by an annular recess that extends in a circumferential direction of the retaining ring at a radially interior portion of the retaining ring.