Abstract: A motor includes a rotor having a permanent magnet; a sleeve rotatably supporting the rotor; fluid provided in a gap between the rotor and the sleeve; a stator having a electromagnet disposed opposite to the permanent magnet to rotate the rotor relative to the stator; and a boss interposed between the sleeve and the stator. In the motor, the sleeve, the stator, and the boss are provided as separate members.

Abstract: A motor includes a rotor having a permanent magnet; a sleeve rotatably supporting the rotor; fluid provided in a gap between the rotor and the sleeve; a stator having a electromagnet disposed opposite to the permanent magnet to rotate the rotor relative to the stator; and a boss interposed between the sleeve and the stator. In the motor, the sleeve, the stator, and the boss are provided as separate members.

Abstract: A thinner fluid dynamic bearing capable of stable shaft rotation, a motor including the bearing, and a recording-medium driving apparatus including the bearing are provided. Pressure-generating grooves are provided in thrust surfaces of a thrust bearing portion 39 opposite a circular plate 35 and a stopper 33 to attract a working fluid from inner and outer edges of the thrust bearing portion 39 to a radially midway portion thereof as a shaft member 16 rotates relative to a support 22. One or more through-holes 48 are provided between inner edges of annular regions of the thrust surfaces in which the pressure-generating grooves are provided and the midway portion in the radial direction. The through-holes extend through the thrust bearing portion 39 in a central-axis direction of the shaft member.

Abstract: In a method for magnetizing a permanent magnet for a motor, the permanent magnet has a thickness t in a radial direction of the permanent magnet satisfying the relation of t??D/(NM??), where D represents an inner diameter of the permanent magnet having a value of 20 mm or less, N represents the number of the magnetic domains of the permanent magnet, and M represents the number of alternating current phases for driving the motor. In a first magnetizing step, the permanent magnet is magnetized in one direction corresponding to the radial direction. In a second magnetizing step, the permanent magnet magnetized in the first magnetizing step is magnetized to form inverse magnetic domains that are arranged at regular intervals in the radial direction and that reverse the magnetizing direction of the permanent magnet.

Abstract: A fluid dynamic bearing includes a shaft member engaged with a circular plate extending radially outward therefrom; a support including a cylinder rotatably accommodating the shaft member, an outer surface of the support having a tapered portion toward an axial upper surface thereof opposing the circular plate; a stopper, an inner surface of the stopper having a constant diameter in an axial direction in a portion opposite to the tapered portion of the support so as to form a tapered gap with respect to an outer surface of the support located under the axial upper surface of the support; and a working fluid placed between the inner surface of the stopper and the outer surface of the support.

Abstract: A method of magnetizing a magnetic member for a rotor of a motor device. The magnetic member has a thickness t in the radial direction of the magnetic member satisfying the relation ?D/(0.75MP??)<t??D/(0.5MP??), where D represents an inner diameter of the magnetic member having a value of 20 mm or less, P represents the number of magnetic poles, and M represents the number of alternating current phases for driving the motor device. The magnetic member is magnetized unidirectionally in the radial direction of the magnetic member. Thereafter, the unidirectionally magnetized magnetic member is magnetized in partitions at regular intervals in the radial direction so that a magnetization direction of the magnetic member is reversed and the magnetic poles are arranged at regular intervals in a circumferential direction.

Abstract: A thinner fluid dynamic bearing capable of stable shaft rotation, a motor including the bearing, and a recording-medium driving apparatus including the bearing are provided. Pressure-generating grooves are provided in thrust surfaces of a thrust bearing portion 39 opposite a circular plate 35 and a stopper 33 to attract a working fluid from inner and outer edges of the thrust bearing portion 39 to a radially midway portion thereof as a shaft member 16 rotates relative to a support 22. One or more through-holes 48 are provided between inner edges of annular regions of the thrust surfaces in which the pressure-generating grooves are provided and the midway portion in the radial direction. The through-holes extend through the thrust bearing portion 39 in a central-axis direction of the shaft member.

Abstract: An object is to provide an information recording and playback apparatus that is capable of reducing, as much as possible, reading and writing errors caused by magnetic leakage flux on the inner peripheral side of a magnetic disk.

Abstract: A fluid dynamic bearing has pressure-generating grooves provided in opposed thrust surfaces of a thrust bearing portion opposite a circular plate and a stopper to direct a working fluid from inner and outer peripheral edges of the thrust bearing portion toward a radially intermediate portion thereof as a shaft member rotates relative to a support. One or more through-holes are provided between inner edges of annular regions of the thrust surfaces in which the pressure-generating grooves are provided and the intermediate portion in the radial direction. The through-holes extend through the thrust bearing portion and interconnect pressure-generating grooves in the opposed thrust surfaces so that bubbles in the working fluid can be sucked smoothly into the through-holes through the pressure-generating grooves.

Abstract: A fluid dynamic pressure bearing has an annular dynamic pressure generating face having a dynamic pressure generating groove, which draws a working fluid toward a midway position in the radial direction from the inside and outside of a thrust bearing plate in the radial direction when a shaft and a housing are rotated relative to each other. The dynamic pressure generating groove is provided on thickness direction end faces of the thrust bearing plate or on an inner surface of the housing, and an inner groove section is located on an inner peripheral side of the dynamic pressure generating face on the end faces and is recessed more than the dynamic pressure generating face in the thickness direction. A through-hole extends through the thrust bearing plate in the thickness direction so as to open to the dynamic pressure generating face, and a communicating cavity connects the opening portion of the through-hole and the inner groove section.

Abstract: A hydraulic dynamic bearing has a rotor comprised of a flanged shaft having a thrust ring portion and a cylinder portion, a hub attached to the flanged shaft, and a rotor magnet attached to an inner peripheral face of a skirt portion of the hub. A stator rotatably supports the rotor and comprises a bearing sleeve to which are attached stator coils, and a stator base plate that supports the sleeve. A gap exists between confronting surfaces of the flanged shaft and the bearing sleeve, and lubricating oil is sealed in the gap. Thrust dynamic pressure generating grooves are formed in one or both faces of the thrust ring, and the grooves are in the form of a herringbone pattern having radial inner groove sections and outer groove sections. The depth of the inner groove sections is shallower than that of the outer groove sections, and the depths of both groove sections are constant. The optimum inner-to-outer groove depth ratio is 0.6 to 0.7.

Abstract: The present invention relates to a cylindrical permanent magnet which is used in a micro DC brushless motor used in a compact hard disc etc. An Sm—Co based magnetic material is used as a magnetic material and the permanent magnet has domains magnetized in a radial direction and arranged at regular intervals in a circumferential direction. Provided that P represents a pitch corresponding to an average of an inner circumferential length and outer circumferential length in one of the domains, D denotes an inner diameter of the permanent magnet, t represents a thickness in the radial direction, N represents the number of domains, and M represents the number of AC phases for driving the motor, D is set to 20 (mm) or smaller and t is set to satisfy the relation of t??D/(NM??).

Abstract: A thinner fluid dynamic bearing capable of stable shaft rotation, a motor including the bearing, and a recording-medium driving apparatus including the bearing are provided. Pressure-generating grooves are provided in thrust surfaces of a thrust bearing portion 39 opposite a circular plate 35 and a stopper 33 to attract a working fluid from inner and outer edges of the thrust bearing portion 39 to a radially midway portion thereof as a shaft member 16 rotates relative to a support 22. One or more through-holes 48 are provided between inner edges of annular regions of the thrust surfaces in which the pressure-generating grooves are provided and the midway portion in the radial direction. The through-holes extend through the thrust bearing portion 39 in a central-axis direction of the shaft member.

Abstract: The present invention relates to a cylindrical permanent magnet which is used in a micro DC brushless motor used in a compact hard disc etc. An Sm—Co based magnetic material is used as a magnetic material and the permanent magnet has domains magnetized in a radial direction and arranged at regular intervals in a circumferential direction. Provided that P represents a pitch corresponding to an average of an inner circumferential length and outer circumferential length in one of the domains, D denotes an inner diameter of the permanent magnet, t represents a thickness in the radial direction, N represents the number of domains, and M represents the number of AC phases for driving the motor, D is set to 20 (mm) or smaller and t is set to satisfy the relation of t??D/(NM??).

Abstract: An object is to provide an information recording and playback apparatus that is capable of reducing, as much as possible, reading and writing errors caused by magnetic leakage flux on the inner peripheral side of a magnetic disk.

Abstract: [Problem] In a hydraulic dynamic bearing comprising a flanged shaft having a thrust ring portion and a cylinder portion, a single bag-like stepped sleeve, a presser ring and a lubricating oil sealed in a fine gap including a thrust gap formed between these bearing constituting members, the lubricating oil in a thrust dynamic pressure generating groove is prevented from being subjected a negative pressure in the vicinity of an inlet. [Means for Resolution] In case of a spiral pattern, the thrust dynamic pressure generating groove G2 is formed such that its depth becomes gradually deep from a side at which a flow velocity of the lubricating oil flowing through the thrust gap is low toward a side at which it is high. Further, in case of a herringbone pattern, the thrust dynamic pressure generating groove G2 is formed such that its depth becomes shallow in an inner peripheral face side than a return point R of the pattern and deep in an outer peripheral face side. An optimum groove depth ratio is 0.6 to 0.7.

Abstract: The generation of bubbles can be suppressed by enabling a stable supply of working fluid to a dynamic pressure generating groove, and oscillation at the time of rotation and leakage of working fluid can be prevented effectively by efficiently releasing any bubbles generated. There is provided a fluid dynamic pressure bearing 1 provided with an annular dynamic pressure generating face 17 made by forming a dynamic pressure generating groove, which draws a working fluid 14 toward a midway position in the radial direction from the inside and outside of a thrust bearing plate 13 in the radial direction, when a shaft 10 and a housing 11 are rotated relative to each other about the axis, on thickness direction end faces 13a, 13b of the thrust bearing plate 13, or on an inner surface of the housing 11, and an inner groove section 16, which is located on an inner peripheral side thereof and that is depressed more than the dynamic pressure generating face 17 in the thickness direction, on the end faces 13a, 13b.

Abstract: The opening of an oil container 11 for storing oil 12 is sealed airtight with a cover member 32. A one-sided-bag-shaped fluid dynamic pressure bearing 10 is seated on an O-ring 25 and fixed airtight onto the upper surface of a bearing seating 30. Inanexhaust position with the distal end portion of an injection tube 36 positioned away from an oil level, the inside of the oil container 11 is evacuated by a vacuum pump 22 through a suction/exhaust passage including a suction/exhaust through-hole 17, thus turning the inside of the one-sided-bag-shaped fluid dynamic pressure bearing (10) into a vacuum. In this state, a control device drives a moving device to raise the oil container 11 to an injection position and releases the suction/exhaust passage to the atmosphere. This causes the oil 12 to be injected into the one-sided-bag-shaped fluid dynamic pressure bearing 10 through an oil injection passage including the injection tube 36.

Abstract: Reducing cogging of a small permanent magnet, while maintaining its magnetization characteristics favorable. Denoting the inner diameter of the permanent magnet by D, the pitch per one magnetic pole by P, and the phase number of an alternating current by M, and when D is 20 mm or less and the thickness of the permanent magnet t is set to fulfill the formula (4), then a good permanent magnet with low cogging is obtained. ?D/(0.75PM??)<t??D/(0.5PM??) . . . (4). In the present embodiment, a permanent magnet for an outer rotor type is explained, but the formula (4) is applicable also to a permanent magnet for an inner rotor type. Moreover, in the present embodiment, it can be applied desirably to the small permanent magnet with an outer diameter of 20 mm or less. Further, in the present embodiment, the Sm—Co (samarium cobalt) based magnetic material was adopted as the magnetic material.

Abstract: The present invention relates to a cylindrical permanent magnet which is used in a micro DC brushless motor used in a compact hard disc etc. An Sm—Co based magnetic material is used as a magnetic material and the permanent magnet has domains magnetized in a radial direction and arranged at regular intervals in a circumferential direction. Provided that P represents a pitch corresponding to an average of an inner circumferential length and outer circumferential length in one of the domains, D denotes an inner diameter of the permanent magnet, t represents a thickness in the radial direction, N represents the number of domains, and M represents the number of AC phases for driving the motor, D is set to 20 (mm) or smaller and t is set to satisfy the relation of t??D/(NM??).