Structure for fixing spindle motor to traverse chassis

A structure for fixing a spindle motor to a traverse chassis in an optical disk apparatus comprising:

• said traverse chassis being adapted to move up and down with respect to a recording surface of an optical disk;
• said spindle motor having a main shaft and a bottom surface adapted to be fixed onto said traverse chassis;
• a turntable fixed to a leading end portion of the main shaft of said spindle motor and adapted to hold an optical disk;
• and
• an optical pickup supported on said traverse chassis and adapted to move back and forth in the radial direction along the recording surface of the optical disk, and wherein:
• in the bottom surface of said spindle motor, there being formed:
• an elongated reference hole, the longest dimension of which extends in a radial direction centered on the main shaft;
• and three screw holes provided equiangularly centered on the main shaft;
• in said traverse chassis, there being formed:
• a protrusion adapted to engage with said reference hole oriented in a direction perpendicular to the direction of the movement of said optical pickup;
• and elongated through holes elongated in the direction perpendicular to the direction of the movement of said optical pickup at the positions corresponding to those of said respective screw holes;
• said spindle motor being adapted to be fixed to said traverse chassis by screwing screws into said respective screw holes through said respective through holes with said protrusion engaged within said reference hole;
• and
• said protrusion has an elliptical cross-sectional shape with a cross-sectional width in the direction of the movement of said optical pickup being approximately the same as the width of said reference hole, while the cross-sectional width of said protrusion in the direction perpendicular to the direction of the movement of said optical pickup being smaller than the cross-sectional width in the direction of the movement of said optical pickup.