Electric power steering apparatus

1. An electric power steering apparatus, comprising an electric motor for producing a steering assist force, further comprising:

a speed reducing mechanism for decelerating a rotation of a rotatable shaft in the electric motor;

a converting mechanism for converting an output rotation of the speed reducing mechanism into an axial movement of a steering shaft extending toward right and left sides of a vehicle;

a first housing; and

a second housing that holds the steering shaft;

the speed reducing mechanism, comprising:

an input pulley driven by the electric motor and held within the first housing,

an output pulley arranged with the steering shaft enclosed thereby,

a belt for connecting the input pulley and the output pulley, and

means for adjusting a tension of the belt; wherein the means for adjusting the tension includes means for changing a center-to-center distance between the input pulley and the output pulley; and

wherein the means for changing the center-to-center distance includes:

a guiding mechanism for relatively guiding the first housing and the second housing in a predetermined guiding direction in which the center-to-center distance can be changed; and

a compression coil spring which can relatively drive the first and second housings in the predetermined guiding direction.

2. The electric power steering apparatus recited in claim 1 , wherein the compression coil spring is disposed between the first and second housings, and urges the first and second housings in opposite directions.