Patent ID: 8534437

Claim:
A centrifugally balanced, radially stacked hydraulic clutch assembly comprising: an inner hydraulic chamber and an outer hydraulic chamber, each hydraulic chamber being respectively configured to rotate about an axis of rotation, the inner hydraulic chamber being radially disposed between the outer hydraulic chamber and the axis of rotation; an inner clutch piston partially situated within the inner hydraulic chamber and defining both an inner apply volume and an inner release volume within the inner hydraulic chamber; wherein the inner clutch piston includes an inner surface and an outer surface, wherein a portion of the outer surface of the inner clutch piston faces the inner apply volume and defines an inner apply area, and wherein a portion of the inner surface of the inner clutch piston faces the inner release volume and defines a inner release area; wherein each portion of the inner apply area is provided at a respective distance from the axis of rotation, and, for each portion of the inner apply area, there is a corresponding portion of the inner release area provided at the same radial distance; an outer clutch piston partially situated within the outer hydraulic chamber and defining an outer apply volume and an outer release volume within the outer hydraulic chamber; wherein the outer clutch piston includes an inner surface and an outer surface, wherein a portion of the outer surface of the outer clutch piston faces the outer apply volume and defines an outer apply area, and wherein a portion of the inner surface of the outer clutch piston faces the outer release volume and defines a outer release area; wherein each portion of the outer apply area is provided at a respective distance from the axis of rotation, and, for each portion of the outer apply area, there is a corresponding portion of the outer release area provided at the same radial distance; and a piston dam; wherein the inner release volume is in fluid communication with the outer release volume through a first port provided in the inner clutch piston; wherein each of the inner clutch piston and outer clutch piston are movable relative to the piston dam; wherein the piston dam separates the inner hydraulic chamber from the outer hydraulic chamber; wherein the inner clutch piston and the piston dam cooperate to partially define the inner apply volume; and wherein the outer clutch piston and the piston dam cooperate to partially define both the outer apply volume and outer release volume wherein the inner clutch piston includes a seal adjacent the outer surface, the seal configured to slidably contact a surface of the piston dam and define a boundary of the apply volume; and wherein the piston dam and the inner clutch piston partially define an isolated volume adjacent the outer surface of the inner clutch piston, wherein the isolated volume is isolated from the inner apply volume by the seal; and wherein the isolated volume is vented through the inner clutch piston by a second port provided in the inner clutch piston.