Structure to prevent deformation of magnetic disk device housing

A magnetic disk unit having:

• a magnetic disk;
• a head drive mechanism in which there has been mounted a head accessing the magnetic disk;
• a base accommodating the magnetic disk and the head drive mechanism, and possessing a flat part, in which a threaded hole is formed, in a circumference of an opening edge;
• and
• a top cover which is formed by a material whose thermal expansion coefficient differs from a thermal expansion coefficient of a material of the base, in which there is provided an escape hole, for a screw, position-aligned to the threaded hole of the flat part, and which is attached to the base by the screw penetrating through the threaded hole and the escape hole for the screw, wherein a first contact portion is provided between the flat part and the top cover, and a second contact portion is provided between a head part of the screw and the top cover,
• wherein a first oil receiving groove is formed in the top cover proximate the first contact portion, and a second oil receiving groove is formed in the top cover proximate the second contact portion, a lubricant being applied to the first and second contact portions,
• wherein, in the first and second contact portions, a friction coefficient in a tightening part of the screw becomes lower than a friction coefficient of another portion of the screw.

A connection structure of a base and a top cover in a storage device, comprising:

• a base accommodating constitutional elements of the storage device and possessing a flat part, in which a threaded hole is formed, in a circumference of an opening edge;
• and
• a top cover which is formed by a material whose thermal expansion coefficient differs from a thermal expansion coefficient of a material of the base, in which there is provided an escape hole, for a screw, position-aligned to the threaded hole of the flat part, and which is attached to the base by the screw penetrating through the threaded hole and the escape hole for the screw, wherein a first contact portion is provided between the flat part and the top cover, and a second contact portion is provided between a head part of the screw and the top cover,
• wherein a first oil receiving groove is formed in the top cover proximate the first contact portion, and a second oil receiving groove is formed in the top cover proximate the second contact portion, a lubricant being applied to the first and second contact portions,
• wherein, in the first and second contact portions, a friction coefficient in a tightening part of the screw becomes lower than a friction coefficient of another portion of the screw.