Hydraulic speed control arrangement for an infinitely variable transmission

Claim 1

A constant output speed control arrangement for an infinitely variable transmission whose transmission ratio is controllable by controlling the supply of hydraulic control fluid thereto, and which is adapted to be connected to a variable speed power source, said control arrangement comprising a displacement pump associated with the output shaft of said transmission so as to supply a control fluid flow proportional to the speed of the transmission output shaft, a transmission control valve structure including a cylinder having a piston movably disposed therein, said piston being biased in one direction by a spring arranged at one side thereof, means for supplying said control fluid from said displacement pump to said cylinder at the other side of said piston, a passage means providing communication between said one and said other side of said piston and having a flow control orifice disposed therein for permitting passage of a desired amount of control fluid, said cylinder having a control opening arranged at said one side of said portion and in communication with said transmission for controlling its transmission ratio, said control opening being adapted to be closed by the piston when said piston is moved by a larger than desired amount of control fluid against the force of said spring for changing the transmission ratio so as to reduce transmission output shaft speed and said control opening, when being opened by said piston upon supply of less than said desired amount of control fluid, providing for the supply of control fluid to said transmission for a change of the transmission ratio so as to increase transmission output shaft speed, and a relief valve structure associated with said valve for maintaining within said valve a predetermined fluid pressure sufficient to operate the speed change control mechanism of said infinitely variable transmission.