ELECTRIC POWER STEERING (EPS) MOTOR CONSTRUCTION/OPERATION


BHE061332960T02

Construction

• The EPS motor is a direct current motor with a magnet fixed to the inner surface of the motor housing.

• The main structural parts are the armature coil (inserted through the steering rack), brush (where energization occurs), magnet and the ball screw.

• The armature coil moves together with the ball screw so that when the coil rotates so does the ball screw.

1
Yoke
2
Armature coil
3
Ball nut
4
Commutator
5
Brush
6
Magnet
7
Motor housing

Operation

• The ball screw, positioned with the steering rack inserted through it, encloses balls that move in the threaded grooves between the rack and the ball screw. A deflector is attached to circulate the balls.

• When the EPS motor operates according to a control current from the EPS control module, the armature is rotated and the ball screw is rotated together with the armature. This causes the balls to roll and move along the threaded groove between the ball screw and the steering rack. The balls are continuously circulated by the ball screw deflector. Due to this, the rotational force of the EPS motor is converted via the balls into the axial direction movement of the steering rack and a highly effective means of transmission is achieved.

1
Ball screw
2
Ball
3
Steering rack
4
Deflector