ELECTRIC POWER STEERING (EPS) CONSTRUCTION AND OPERATION

id061300246300

Construction

• The EPS system consists of the following mechanisms.

- Electric assist and manual steering mechanisms: Consists of the steering wheel, steering shaft, steering gear and linkage, and the deceleration system and EPS motor built into the steering gear and linkage.

- Control system

Consists of a torque sensor, and vehicle speed and engine speed signals input from the EPS CM and PCM.

Operation

• The EPS assists the manual steering mechanism operation using the EPS motor to provide supplemental manual power during vehicle steering, reducing the load on the driver.

Manual steering mechanism operation

• The steering input force, formed when the driver operates the steering wheel, is transmitted to the rack and pinion mechanism of the steering gear and linkage.

Control system operation

• According to the steering operation of the driver, the torque sensor detects the steering force for the road surface resistance and converts it to an electronic signal, and then inputs a steering force signal to the EPS CM.

• The EPS CM determines the proper assist force based on this steering force signal for each vehicle speed signal and outputs it as a target current to operate the EPS motor.

Power assist mechanism operation

• The EPS motor is operated according to the target current from the EPS CM and its operating force is transmitted to the pinion of the steering gear and linkage via the deceleration system to assist the shaft in turning axially.

Component parts and function


Item		Specification
Steering Gear and Linkage	Torque sensor	• Detects the steering force and inputs it to the EPS CM as an electric signal.
Steering Gear and Linkage	EPS motor	• Generates the operating force based on the target current from the EPS CM.
EPS CM		• Controls the target current for the EPS motor based on the steering force signal from the torque sensor and vehicle speed signal from the PCM. • Controls the on-board diagnostic system and fail-safe function when a malfunction is detected in the EPS system.
PCM	Vehicle speed signal	• Inputs the vehicle speed signal to the EPS CM via CAN lines.
PCM	Engine speed signal	• Inputs the engine speed signal to the EPS CM via CAN lines.
Instrument cluster	EPS warning light	• The light illuminates to inform the driver when a system malfunction is detected.