Abstract: A transmission includes a first shaft that is rotatable in a circumferential direction about a central axis extending in one direction, a second shaft that is rotatable in the circumferential direction and in series with the first shaft in an axial direction in which the central axis extends, a tubular housing, an internal gear including an internal tooth portion, and held by an inner surface of the housing, an annular external gear connected to the second shaft, and including an external tooth portion that partially meshes with the internal tooth portion, and a wave generator connected to the first shaft to deform the external gear such that meshing positions between the internal tooth portion and the external tooth portion shift in the circumferential direction. The internal gear and the housing are defined by separate members.

Abstract: A transmission includes a first shaft that is rotatable in a circumferential direction about a central axis extending in one direction, a second shaft that is rotatable in the circumferential direction and in series with the first shaft in an axial direction in which the central axis extends, a tubular housing, an internal gear including an internal tooth portion, and held by an inner surface of the housing, an annular external gear connected to the second shaft, and including an external tooth portion that partially meshes with the internal tooth portion, and a wave generator connected to the first shaft to deform the external gear such that meshing positions between the internal tooth portion and the external tooth portion shift in the circumferential direction. The internal gear and the housing are defined by separate members.

Abstract: A spindle motor includes a stationary portion and a rotating portion. The stationary portion includes a shaft and an upper annular member. The rotating portion includes a sleeve. The shaft includes an annular or substantially annular upper shaft recessed portion recessed radially inward from an outside surface of the shaft. The upper shaft recessed portion is arranged opposite to an inside surface of a hole of the upper annular member. An adhesive is arranged in a gap defined between the upper shaft recessed portion and the inside surface of the hole of the upper annular member.

Abstract: A spindle motor includes a stationary portion and a rotating portion. The stationary portion includes a shaft and an upper annular member. The rotating portion includes a sleeve. The shaft includes an annular or substantially annular upper shaft recessed portion recessed radially inward from an outside surface of the shaft. The upper shaft recessed portion is arranged opposite to an inside surface of a hole of the upper annular member. An adhesive is arranged in a gap defined between the upper shaft recessed portion and the inside surface of the hole of the upper annular member.

Abstract: A bearing mechanism includes a shaft, a sleeve portion, a thrust portion, and a cover portion. Lubricating oil is arranged in a communicating channel in the sleeve portion, a thrust gap between the sleeve portion and the thrust portion, and a tapered gap between an outside surface of the thrust portion and the cover portion. A lower end opening of the communicating channel is defined in an outer circumferential portion of a lower surface of the sleeve portion radially outward of the thrust gap. A radially outermost portion of the thrust portion is arranged either tangent to a wall surface of the communicating channel or closer to a central axis than the wall surface. The tapered gap is arranged closer to the central axis than a radially outermost point of the wall surface. The outer circumferential portion and the cover portion define a guide gap therebetween.

Abstract: A fluid dynamic bearing mechanism includes a stationary shaft, a sleeve portion arranged to rotate with respect to the shaft, and a thrust portion including an upper end surface arranged oppose to a lower end surface of the sleeve portion. An inside surface of the thrust portion includes an inside surface contact portion arranged in contact with an outside surface of the shaft, and an inside surface lower non-contact portion spaced away from the outside surface of the shaft, and arranged to extend downward from a lower end of the inside surface contact portion. An outside surface of the thrust portion includes an outside surface inclined portion arranged in contact with an interface of a lubricating oil. The lower end of the inside surface contact portion is arranged at a level axially higher than that of a lower end of the outside surface inclined portion.

Abstract: A rotor unit includes a substantially circular plate shaped cover portion, a rotor hub including a lower cylinder portion, and a magnetic field generating member attached on the lower cylinder portion. An annular salient portion is provided on the lower surface of the cover portion 31. The annular salient portion lies radial inwards of the lower opening of the through-hole of the cover portion and protrudes downwards in the shape of a ring whose center coincides with the central axis. The magnetic field generating member includes a rotor magnet and a back iron covering the outer surface and upper surface of the rotor magnet. When the magnetic field generating member is mounted to the rotor hub, the upper portion of the back iron comes in contact with the annular salient portion, which determines the axial position of the magnetic field generating member.

Abstract: A fluid dynamic bearing mechanism includes a stationary shaft, a sleeve portion arranged to rotate with respect to the shaft, and a thrust portion including an upper end surface arranged oppose to a lower end surface of the sleeve portion. An inside surface of the thrust portion includes an inside surface contact portion arranged in contact with an outside surface of the shaft, and an inside surface lower non-contact portion spaced away from the outside surface of the shaft, and arranged to extend downward from a lower end of the inside surface contact portion. An outside surface of the thrust portion includes an outside surface inclined portion arranged in contact with an interface of a lubricating oil. The lower end of the inside surface contact portion is arranged at a level axially higher than that of a lower end of the outside surface inclined portion.

Abstract: A rotor unit includes a substantially circular plate shaped cover portion, a rotor hub including a lower cylinder portion, and a magnetic field generating member attached on the lower cylinder portion. An annular salient portion is provided on the lower surface of the cover portion 31. The annular salient portion lies radial inwards of the lower opening of the through-hole of the cover portion and protrudes downwards in the shape of a ring whose center coincides with the central axis. The magnetic field generating member includes a rotor magnet and a back iron covering the outer surface and upper surface of the rotor magnet. When the magnetic field generating member is mounted to the rotor hub, the upper portion of the back iron comes in contact with the annular salient portion, which determines the axial position of the magnetic field generating member.

Abstract: A bearing mechanism includes a shaft, a sleeve portion, a thrust portion, and a cover portion. Lubricating oil is arranged in a communicating channel in the sleeve portion, a thrust gap between the sleeve portion and the thrust portion, and a tapered gap between an outside surface of the thrust portion and the cover portion. A lower end opening of the communicating channel is defined in an outer circumferential portion of a lower surface of the sleeve portion radially outward of the thrust gap. A radially outermost portion of the thrust portion is arranged either tangent to a wall surface of the communicating channel or closer to a central axis than the wall surface. The tapered gap is arranged closer to the central axis than a radially outermost point of the wall surface. The outer circumferential portion and the cover portion define a guide gap therebetween.