Actuator Operation

Diagram:

The transaxle control actuators are electrohydraulic solenoid valves consisting of a housing, valvebody, sliding armature and electromagnetic coil. They are a three port design with a pressure supply port, a pressure outlet or control pressure port, and an exhaust port.

The actuators have normally open valves. When "0" voltage is applied to the terminals, a return spring holds the valve open and the actuator will allow oil to flow from the supply port to the outlet pressure port. When current flows through the coil, the magnetic field is energized pulling the sliding armature against the return spring. When the armature is in this position, the valve is closed, the pressure supply port is blocked, and the control port is connected to the exhaust port.

The actuators are located in the transaxle valvebody. An actuator may be completely energized (closely), de-energized (open), or pulse width modulated (PWM). When it is being modulated, the valve opens and closes up to 70 times per second. This allows a percentage of the oil pressure available at the supply port to pass to the control port. The actual percentage is determined by an electrically controlled duty cycle from the PCM. This is the ratio of the length of time the valve remains open (pulse width) to the total length of time of each cycle (one On and Off cycle.