Hydraulic control devices of transmission mechanisms

Claim 1

A hydraulic device for controlling an automotive change-speed transmission, comprising a transmission shaft revolving in a hollow shaft extending through one wall of the transmission case and carrying a bell-shaped member forming an annular actuator chamber bounded in the axial direction by the inner face of said bell-shaped member and the inner face of an annular change-speed control piston slidably mounted in said bell-shaped member and urged towards said inner face of said bell-shaped member by a return spring, said chamber communicating through the medium of a rotary seal and a passage formed in said hollow shaft with a hydraulic fluid supply duct passing through said wall and, through a valve, with the inner space of the transmission case, said supply duct being connected through a control distributor to a pressure oil lubrication system communicating directly with said passage by means of an axial duct formed in said transmission shaft and of a substantially radial passage formed in said shaft, a piston-actuated shutter arranged in said chamber of said annular actuator upstream of said valve, whereby in the operative piston position said shutter will regulate the oil pressure in said chamber by acting somewhat like an overflow and maintain said chamber under a substantially constant pressure.