Control arrangement for a variable pulley transmission

A control arrangement for a continuously variable transmission including a primary pulley for receiving drive from an engine, a secondary pulley, a belt coupling the secondary pulley to the primary pulley, and a fluid-cooled clutch connected to transfer dirve from the secondary pulley to a driven means, with the primary pulley having an axially movable sheave to effect ratio change of the transmission and the secondary pulley having an axially movable sheave to regulate belt tension in the system, a fluid supply line connected to receive fluid under pressure, and also coupled to the movable sheave of the secondary pulley, which control arrangement comprises

• a first electromechanical valve assembly, coupled to the supply line, connected to regulate the supply line pressure passed to the movable sheave of the secondary pulley and thus regulate the belt tension level,
• a second electromechanical valve assembly, coupled to the supply line, connected to regulate fluid flow to the movable sheave of the primary pulley and thus regulate the transmission ratio, and
• a controller including a computer connected to received input signals including signals representing engine speed, belt output speed, throttle position, and gearshift position, and to provide a set engine speed signal and a set pressure signal, and a control system connected to receive said set signals, to provide a line pressure control signal to the first electromechanical valve assembly as a function of the set pressure signal, and to provide a ratio control signal to the second electromechanical valve assembly as a function of the set engine speed signal.