Circuit/System Description

The power steering control module (PSCM) uses the steering shaft torque as its main input for determining steering direction and the amount of steering assist needed. The steering column has an input shaft from the steering wheel to the torque sensor and an output shaft from the torque sensor to the intermediate shaft coupler. The input and output shafts are separated by a section of torsion bar at the base of the steering column where the torque sensor is located. The torque sensor consists of a detecting coil, compensation coil and 3 detecting rings. Detecting ring 1 is fixed to the output shaft while detecting ring 2 is fixed to the input shaft. Both detecting rings have toothed edges that face each other. The detecting coil is positioned around the toothed edges of detecting rings 1 and 2. As torsional twist is applied to the steering column shaft's torsion bar when the steering wheel is turned, these toothed edges change alignment with each other which effects the magnetic characteristics around the detecting coil, changing the coils impedance thus changing the sensor signal voltage input to the PSCM. The PSCM recognizes this change in detecting coil signal voltage as steering column shaft torque. The compensation coil is positioned around detecting rings 2 and 3, which do not change alignment with each other as the steering wheel is turned. This coil is used to compensate for the rotation of the steering shaft and also conditions that can effect circuit impedance, such as voltage, current and ambient temperature, for accurate torque detection.