Steering: Description and Operation

EPS (ELECTRONIC POWER STEERING) SYSTEM

GENERAL
The Electronic Power Steering (EPS) system uses the same components at that of conventional power steering system. In addition, it has a solenoid valve on power steering gear box, and a control unit underneath the audio of the center facia. To control the oil flow of steering gear box, a solenoid is provided and it functions by the current from control module which receives signal from Vehicle Speed Sensor (VSS).

EPS performs the conventional power steering function in case a fail has occurred in the system.

EPS electronically controls the current to the solenoid of by-pass valve by input sensor's signal to control the hydraulic amount in cylinder chamber thereby varying the steering effort versus the hydraulic pressure according to vehicle speed.

ELECTRONIC POWER STEERING UNIT





The EPS unit is installed underneath the audio inside the center facia.

EPS SOLENOID

SOLENOID VALVE
A solenoid valve is provided in the gear box to control the flow of power steering oil. The solenoid valve is composed of a releasing spring, a piston and plunger.

The input current is varying from 0A to 1A according to the vehicle speed and is controlled by EPS unit.

When the ignition switch is turned on, current is sent to the solenoid valve to push up the plunger and accordingly the piston contacting the plunger is pushed up while overcoming the spring force. As the vehicle speed increasing the current flow to the solenoid decreased pulling down the piston bottom by the releasing spring force.

When the piston is pushed up, it closes the oil passing hole, therefore the power steering oil pressure is delivered into the cylinder without any interruption. But when the hole is opened as the piston is pulling down, some of the oil coming from the rotary valve is drained into reservoir via the hole inside the rotary valve.





NOTE: When it is necessary to remove the EPS gear box, be sure to disconnect the connector to avoid damage.