Abstract: A projection welding method which comprises providing in either one of a first member and a second member to be welded a plurality of projections projecting toward the other member, supplying a current between the first and second members to melt the plurality of projections, and welding the first and second members. The plurality of projections are composed of projections having a plurality of kinds with different heights. Furthermore, with reference to the plurality of projections, concave grooves in which a molten product flows are provided.

Abstract: A spindle motor having a housing, a hub member rotatable relative to the housing, a bearing means disposed between the housing and the hub member, a rotor magnet mounted on the hub member, and a stator disposed in a facing relationship with the rotor magnet. The hub member includes a supporting wall portion, which cooperates with the stator to constitute an air seal structure. A magnetic fluid seal means is provided at a position outward of the bearing means, and includes a conductive plate for grounding static electricity. The bearing means is comprised of a radial ball bearing, which includes certain improvement.

Abstract: A spindle motor having a housing, a hub member rotatable relative to the housing, a bearing disposed between the housing and the hub member, a rotor magnet mounted on the hub member, and a stator disposed in a facing relationship with the rotor magnet. The hub member includes a supporting wall portion, which cooperates with the stator to constitute an air seal structure. A magnetic fluid seal is provided at a position outward of the bearing, and includes a conductive plate for grounding static electricity. The bearing is comprised of a radial ball bearing, which includes certain improvement.

Abstract: A spindle motor having a shaft member secured to a fitting member, a rotary member which is rotatable relatively to the shaft member, a rotor magnet fitted to the rotary member in such a manner that the rotor magnet confronts the rotor magnet and a stator, wherein a pair of inner annular grooves are formed in the shaft member, a pair of outer annular grooves are formed in the rotary member and a plurality of ball members are accommodated in ball-accommodating space defined by these annular grooves.

Abstract: A spindle motor comprising a fixed shaft member, a hub member rotatably supported by the fixed shaft member through bearings, and a magnetic-fluid type sealing mechanism arranged between the fixed shaft member and the hub member. The magnetic-fluid type sealing mechanism has a rotary member mounted on the hub member, a stationary member mounted on the fixed shaft member, and a magnetic fluid holding device for holding a magnetic fluid. The magnetic fluid holding is secured to the annular mounting portion of the stationary member. The magnetic fluid holding device and the annular portion of the rotary member cooperate with each other in holding the magnetic fluid therebetween.

Abstract: A spindle motor having a shaft member secured to a fitting member, a rotary member which is rotatable relatively to the shaft member, a rotor magnet fitted to the rotary member in such a manner that the rotor magnet confronts the rotor magnet and a stator, wherein a pair of inner annular grooves are formed in the shaft member, a pair of outer annular grooves are formed in the rotary member and a plurality of ball members are accommodated in ball-accommodating space defined by these annular grooves.

Abstract: A spindle motor having a shaft member secured to a fitting member, a rotary member which is rotatable relatively to the shaft member, a rotor magnet fitted to the rotary member in such a manner that the rotor magnet confronts the rotor magnet and a stator, wherein a pair of inner annular grooves are formed in the shaft member, a pair of outer annular grooves are formed in the rotary member and a plurality of ball members are accommodated in ball-accommodating space defined by these annular grooves.