EPS System Description - Components
Components
The EPS system mainly consists of the following parts:
- EPS control unit
- EPS motor
- Torque sensor
- Steering gearbox
- System indicator
For functions of indicator, refer to How to Troubleshoot the EPS System .
Steering Gearbox
The EPS system is rack-assist type, and the steering gearbox is a dual pinion type, which includes two pinions that are engaged with steering rack.
The assist pinion shaft transmits the EPS motor power to the steering rack. The EPS motor power is transmitted to the worm wheel by the worm gear. The assist pinion shaft moves the steering rack with the EPS motor power that is increased and transmitted by the worm wheel.
The manual pinion shaft transmits the steering torque from the steering wheel to the steering rack. The steering torque is transmitted from the steering column shaft to the input shaft, and the manual pinion shaft connecting with the input shaft by the torsion bar moves the steering rack.
VGR (Variable Gear Ratio)
The VGR is applied to the manual pinion shaft side of the steering rack. The normal gear ratio is applied to the near the straight ahead position of the steering rack for smooth start of steering operation. The quick gear ratio is applied for a large steering angle, which reduces lock-to-lock steering.
Torque Sensor
Overview
The torque sensor is built into the steering gearbox, using a Hall IC sensor to detect steering wheel torque forces. The torque sensor consists of the input shaft, the torsion bar, the manual pinion shaft, and the torque sensor unit.