load is made smaller than that during no load running and that changing over between running under a load and no load running is automatically effected in response to a detection signal from the rotational angle detector and controls rotation of said agitating wheel to an angle equal to or less than 360 degrees including rotation by energization of the motor and rotation by inertia whether during running under a load or no load application_number US 58115584 A description an embodiment of the present invention will now be described with reference to the accompanying drawings referring to fig1 and 2 a washing tank 2 is secured within the outer housing 1 of a washing machine and articles are washed in the washing tank 2 a main shaft 3 is mounted water tight at the center of a bottom of the washing tank 2 and is supported for rotation by means of a main shaft bearing 4 an agitating wheel 5 is mounted on the main shaft 3 within the washing tank 2 and a pulley 6 is mounted at a bottom end of the main shaft 3 and has a plurality of detection holes 7 for detection of a rotational angle of the agitating wheel 5 perforated in a predetermined spaced relationship along a circular line therein fig2 a rotational angle detector 8 includes a light emitter 9 and a light receiver 10 light receiver 10 receives at a position of a detection hole 7 of the.