Accelerator Actuator

Accelerator Actuator:

The accelerator actuator consists of a reversible DC motor with a multistage reduction gear. The output shaft for the throttle valve control linkage is attached to the output lever. The moving contact (wiper) of the potentiometer as well as the double-contact safety switch are both attached to the output shaft. If the ignition switch is in the on position or if the engine is running, the electronic accelerator control unit supplies a constant voltage to the potentiometer. The moving contact (wiper) returns a voltage to the control unit which is directly proportional to the output shaft and therefore throttle valve position. This position signal is processed by the system control portion of the control unit, which energizes the motor to change the position of the throttle valve if necessary. The accelerator actuator output shaft can move through an angle of 88 - 92°, allowing a full range of throttle valve openings from idle to wide open. The DC motor has a high adjustment speed, covering the entire adjustment angle in approx. 120 m sec. At the same time, the positioning is very accurate.

Accelerator Actuator:

The rotation of the actuator is different for different engines (see SYSTEM ID). On engines 116 and 117 the adjustment between idle and wide open throttle turns clockwise. With engines 103, 104 and 119 it turns counterclockwise.

Safety Switch:

At maximum adjustment speed the current draw approaches 8 amps. With the accelerator pedal in the idle position, the safety switch is closed. The safety switch gets voltage when the ignition switch is in the on position or when the engine is running, and circuit 15 at the fuel pump relay (or engine systems control unit) is thus energized. When the accelerator is depressed, the safety switch opens at approx. 8 - 12° above the idle position. The safety switch for the accelerator pedal position sensor then takes over the voltage supply for the fuel pump relay or the engine systems control unit. So that there is no switch gap when the accelerator pedal is moved quickly, a switching transistor takes over the voltage supply for the fuel pump relay (or engine systems control unit) for a short period of time. The maximum current flow may not exceed 1 amp. The switching transistor is not protected from short circuits to ground. This switching transistor is also used during cruise control operation.