Control arrangement for a variable pulley transmission

Claim 1

A control arrangement (22) for a continuously variable transmission with a gearshift selector (14), in which a primary pulley (30) receives drive from an engine (12) with a throttle, a secondary pulley (36) is coupled over a belt (42) to the primary pulley (30), a driven means (40) receives drive from the secondary pulley (36) with each of the pulleys having a sheave (68, 152) axially movable by fluid pressure to effect ratio change of the transmission and to maintain belt tension, which control arrangement (22) comprises an electromechanical valve assembly (414) connected to provide a first fluid signal to the movable sheave (152) of the secondary pulley (36) to regulate the belt tension level, another electromechanical valve assembly (408) connected to provide a second fluid signal to the movable sheave (68) of the primary pulley (30) to regulate the transmission ratio, a controller (406) having a computer (701), which controller is connected to provide electrical control signals to both valve assemblies (414, 408) as a function of received input signals including engine speed, belt output speed, throttle position, and gearshift selector position, to govern the transmission (14) to operate at an optimum condition for the conditions signified by the received input signals, and characterized by a fluid-cooled clutch (16) arranged to transfer drive from the secondary pulley (36) to the driven means (40), said belt output speed being derived from the fluid-cooled clutch, a transducer (432) connected to provide a feedback signal, related to a mechanical position in the other electromechanical valve assembly (408), to the controller (406) for use with a set engine speed signal provided by the computer (701) to produce a ratio control signal.