Electronic Steering: Description
The Servotronic system consists of an electronic speedometer, a power steering Electronic Control Unit (ECU) and a Servotronic valve. See Fig 1 . The Servotronic valve is mounted on the body of the variable ratio rack and pinion. The speedometer inputs vehicle speed signal to the ECU, which electrically controls hydraulic pressure via the Servotronic valve.
When the vehicle is stationary, no speed signal is sent to the ECU. The ECU provides maximum current to valve, causing valve to close. Pressure from pump is equal in the reaction chambers, allowing light steering control. As speed increases, the ECU provides less current to the valve. The valve opens, raising the pressure in the reaction chamber. This produces an opposite turning force, resulting in heavier steering effort as speed increases.