Patent ID: 7092203

Claim:
A method of manufacturing a fluid dynamic bearing, the fluid dynamic bearing having: a shaft base having a flat surface on one side thereof; a shaft erected on one side of the shaft base and having a cylindrical outer peripheral surface; a sleeve member rotatably supported on and relatively to the shaft, the sleeve member including an inner peripheral surface in radially opposed relation to the outer peripheral surface of the shaft and an axial end surface in axially opposed relation to the flat surface, the sleeve member being fitted on the shaft; a cylindrical peripheral wall erected on one side of the shaft base in such a manner as to surround the radially outer part of the sleeve member; and an annular cover member having an inner peripheral edge smaller in diameter than the inner peripheral surface of the cylindrical peripheral wall, the cover member being mounted on the cylindrical peripheral wall; wherein at least a part of the gap between the outer peripheral surface of the shaft and the inner peripheral surface of the sleeve member which are in radially opposed relation to each other is secured as a minuscule radial bearing gap filled with the lubricating oil; the radial dynamic bearing is made up of the outer peripheral surface of the shaft, the inner peripheral surface of the sleeve and the radial bearing gap; and the flat surface of the shaft base plate member and the axial end surface of the sleeve member are in axially opposed relation to each other, and at least partially filled with the lubricating oil; the manufacturing method comprising: a first step to hold the lubricating oil in at least a part of said radial gap and said axial gap, in which the interface between the lubricating oil and the atmosphere is formed between the cylindrical peripheral wall and the outer peripheral surface of the sleeve member; and a second step to locate, after the first step, an axial end surface of the cover member being apart from the interface in axial direction, and to fixedly weld the cover member by radiating a directive energy beam on said cylindrical peripheral wall.