Calibration of an actuator for a variable geometry turbine

Abstract

A variable geometry turbine of the kind used in a turbocharger has a variable geometry element such as a nozzle ring or an annular array of swing vanes that is operated by an actuator. The actuator has an output shaft coupled to a transmission mechanism for moving the variable geometry element. A rotary sensor device coupled to the output shaft of the actuator has a sensor wheel with a stop, slip clutch mechanism and a rotary position sensor. The device converts movement of the actuator output shaft into rotation of the wheel and the sensor generates an output signal representative of the rotary position of the wheel to provide a value indicative of the position of the variable geometry element. The actuator is calibrated to the position of the variable geometry element by rotating the sensor wheel in a first rotational direction until the variable geometry element reaches the first limit position, then rotating the sensor wheel in a second direction until the variable geometry element reaches the second limit position. The value of the output signal is logged at one of these positions as a limit value. The sensor wheel is allowed to declutch in the event that it encounters the stop in either direction of rotation. The output signal is monitored and the limit value is deducted to determine the position of the variable geometry element.