Abstract: A friction engagement device has single-faced externally toothed disks interleaved with single-faced internally toothed disks which are engageable by an annular piston. The thickness of the externally toothed disks is less than the thickness of the internally toothed disks for improved heat dissipation performance.

Abstract: A spring plate for use in a multiple disk friction coupling device, wherein a spring plate is an elastic member formed generally in a dish-like shape; a driving face facing a mating member comprises a side face of an outer diameter end portion, a circular protruding face, and a slant face smoothly continuing to this protruding face. The axial section of the driving face is formed of straight lines and curves which continue. The spring plate, when pushed against the mating member by a piston, is elastically deformed, pressing the driving face against a wide range of the mating member. Therefore the friction coupling member of the friction coupling device will never be locally heated to a high temperature, thus preventing heat distortion and non-uniform seizure of these members and accordingly smooth operation of the friction coupling device for a prolonged period of time.

Abstract: A friction plate for a friction engagement device has a pattern of grooves in the surface thereof. In one embodiment, radial grooves are inclined from the inner edge of the plate to the outer edge which divide the plate into friction material segments. A pair of radially spaced connecting grooves traverse each segment to connect the radial grooves which define the segment, and are staggered radially from the pairs of connecting grooves of the adjacent segments, so that the grooves of adjacent pairs alternate in radial location across the radial groove which divides them. In another embodiment, tangential grooves form a regular polygon inscribing the outer edge of the friction plate. In both embodiments, oil traverses the surface of the plate from the inner diameter edge to the outer diameter edge by a serpentine route alternating between the radial grooves and the connecting or tangential grooves.

Abstract: A groove structure for a wet-type friction engaging element has an approximately U-shaped cross-sectional form in which both corners of a bottom surface are deeper than an intermediate section.