Compound bearing apparatus, and spindle motor and swing arm for hard disk drive means including such bearing apparatus

A spindle motor including a rotating member rotor hub journalled on a base by means of a compound bearing apparatus, said compound bearing apparatus comprising:

• a stepped shaft having an enlarged diameter shaft portion and reduced diameter shaft portion, a sleeve outer race surrounding the stepped shaft, and two rows of rotating bodies interposed therebetween, wherein:
• the rotating bodies of the first row are disposed between an outer peripheral rolling recess formed directly on an outer peripheral surface of the enlarged diameter shaft portion and a first inner peripheral rolling recess formed directly on the inner peripheral surface of the sleeve outer race,
• the rotating bodies of the second row are disposed between an outer peripheral rolling recess formed on an outer periphery of an inner race fitted over the reduced diameter shaft portion of said stepped shaft and a second inner peripheral rolling recess formed directly on the inner peripheral surface of the sleeve outer race,
• an outer peripheral labyrinth recess formed on the outer peripheral surface of the enlarged diameter shaft portion at the longitudinal inner side of the rotating bodies of the first row,
• a space defined between a shoulder, formed at a point of transition from the enlarged diameter shaft portion to the reduced diameter shaft portion, and an inner end of the inner race,
• at the longitudinal outer side of the rotating bodies of the first row, a first outer sealing plate of ring shape having a central aperture is fixedly fitted at its outer periphery into an inner peripheral groove formed on the inner peripheral surface of the sleeve outer race,
• the inner diameter of the central aperture of said first outer sealing plate is slightly larger than the enlarged diameter shaft portion to prevent the first outer sealing plate from contact with the stepped shaft and to provide a labyrinth seal function,
• at the longitudinal outer side of the rotating bodies of the second row, a second outer sealing plate of ring shape having a central aperture is fixedly fitted at its outer periphery into an inner peripheral groove formed on the inner peripheral surface of the sleeve outer race,
• the inner diameter of the central aperture of said second outer sealing plate is substantially equal to or smaller than the outer diameter of the inner race and larger than the outer diameter of the reduced diameter shaft portion to provide a labyrinth seal function,
• at the longitudinal inner side of the rotating bodies of the first row, a first inner sealing plate of ring shape having a central aperture is fixedly fitted at its outer periphery into an inner peripheral groove formed on the inner peripheral surface of the sleeve outer race,
• the inner diameter of the central aperture of said first inner sealing plate is substantially equal to or smaller than the outer diameter of the enlarged diameter shaft portion and larger than the outer diameter of the labyrinth recess to prevent the first inner sealing plate from contact with the stepped shaft to provide a labyrinth seal function,
• at the longitudinal inner side of the rotating bodies of the second row, a second inner sealing plate of ring shape having a central aperture is fixedly fitted at its outer periphery into an inner peripheral groove formed on the inner peripheral surface of the sleeve outer race,
• the inner diameter of the central aperture of said second inner sealing plate is substantially equal to or smaller than the outer diameter of the inner ring and larger than the outer diameter of the reduced diameter shaft portion of the stepped shaft to prevent the second inner sealing plate from contact with the stepped shaft or the inner race to provide a labyrinth seal function.

A swing arm assembly journalled rotatably on a base of a bard disk drive device through a compound bearing apparatus provided within a base cylindrical portion of a swing arm, said compound bearing apparatus comprising:

• a stepped shaft having an enlarged diameter shaft portion and a reduced diameter shaft portion, a sleeve outer race surrounding the stepped shaft, and two rows of rotating bodies interposed therebetween, wherein:
• the rotating bodies of the first row are disposed between an outer peripheral rolling recess formed directly on an outer peripheral surface of the enlarged diameter shaft portion and a first inner peripheral rolling recess formed directly on the inner peripheral surface of the sleeve outer race,
• the rotating bodies of the second row are disposed between an outer peripheral rolling recess formed on an outer periphery of an inner race fitted over the reduced diameter shaft portion of said stepped shaft and a second inner peripheral rolling recess formed directly on the inner peripheral surface of the sleeve outer race,
• an outer peripheral labyrinth recess formed on the outer peripheral surface of the enlarged diameter shaft portion at the longitudinal inner side of the rotating bodies of the first row,
• a space defined between a shoulder, formed at a point of transition from the enlarged diameter shaft portion to the reduced diameter shaft portion, and an inner end of the inner race,
• at the longitudinal outer side of the rotating bodies of the first row, a first outer sealing plate of ring shape having a central aperture is fixedly fitted at its outer periphery into an inner peripheral groove formed on the inner peripheral surface of the sleeve outer race,
• the inner diameter of the central aperture of said first outer sealing plate is slightly larger than the enlarged diameter shaft portion to prevent the first outer sealing plate from contact with the stepped shaft and to provide a labyrinth seal function,
• at the longitudinal outer side of the rotating bodies of the second row, a second outer sealing plate of ring shape having a central aperture is fixedly fitted at its outer periphery into an inner peripheral groove formed on the inner peripheral surface of the sleeve outer race,
• the inner diameter of the central aperture of said second outer sealing plate is substantially equal to or smaller than the outer diameter of the inner race and larger than the outer diameter of the reduced diameter shaft portion to provide a labyrinth seal function,
• at the longitudinal inner side of the rotating bodies of the first row, a first inner sealing plate of ring shape having a central aperture is fixedly fitted at its outer periphery into an inner peripheral groove formed on the inner peripheral surface of the sleeve outer race,
• the inner diameter of the central aperture of said first inner sealing plate is substantially equal to or smaller than the outer diameter of the enlarged diameter shaft portion and larger than the outer diameter of the labyrinth recess to prevent the first inner sealing plate from contact with the stepped shaft to provide a labyrinth seal function,
• at the longitudinal inner side of the rotating bodies of the second row, a second inner sealing plate of ring shape having a central aperture is fixedly fitted at its outer periphery into an inner peripheral groove formed on the inner peripheral surface of the sleeve outer race,
• the inner diameter of the central aperture of said second inner sealing plate is substantially equal to or smaller than the outer diameter of the inner ring and larger than the outer diameter of the reduced diameter shaft portion of the stepped shaft to prevent the second inner sealing plate from contact with the stepped shaft or the inner race to provide a labyrinth seal function.