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 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: 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: 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: 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: The invention provides a motor that is provided with a fluid dynamic bearing for rotatably supporting a shaft body, by the dynamic pressure of fluid filling a clearance between itself and a shaft body support part. The motor is provided with: a stator having cores and coils; a rotor having permanent magnets arranged in a ring shape on the radial inner side of the stator, facing the cores and coils; and a fluid dynamic bearing which rotatably supports the rotor with respect to the stator.

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 invention provides a motor that is provided with a fluid dynamic bearing for rotatably supporting a shaft body, by the dynamic pressure of fluid filling a clearance between itself and a shaft body support part. The motor is provided with: a stator having cores and coils; a rotor having permanent magnets arranged in a ring shape on the radial inner side of the stator, facing the cores and coils; and a fluid dynamic bearing which rotatably supports the rotor with respect to the stator.

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 motor armature which allows assembly works to be facilitated and which can be miniaturized and thinned is provided. An inner cylinder 1 and an outer cylinder 2 are disposed coaxially and a plurality of pole pieces 3 are provided radially at equal intervals between the inner cylinder 1 and the outer cylinder 2. The inner cylinder 1 is formed into a cylindrical shape by curling up in the longitudinal direction a hoop member (band steel) made of a magnetic material and having a predetermined thickness and length. The outer cylinder 2 is made of the hoop member similarly to the inner cylinder 1. The pole piece 3 is what a coil 4 is wound around a wire piece 5 obtained by cutting a wire (wire rod) made of a magnetic material and having a predetermined thickness into a predetermined length. One end of the wire piece 5 is fixed to the outer peripheral face of the inner cylinder 1 by means of welding or the like and the other end of the wire piece is fixed to the inner peripheral face of the outer cylinder 2.

Abstract: A method for lubricating a part without leaving air bubbles includes the steps of assembling components so that an open end is formed for application of lubricating fluid and a fluid path is provided through which the lubricating fluid is to be circulated, introducing the lubricating fluid into the open end and applying a centrifugal force to the component by moving the component about a circular path so that the centrifugal force causes the lubricating fluid to be urged throughout the fluid path. The method is used in an embodiment to lubricate a dynamic pressure bearing having a gap between relatively moving parts. The gap has an open end into which the lubrication fluid is dripped and a closed end. During movement of the bearing about a circular path, the fluid is urged from the open end to the closed end.

Abstract: A double sleeve type dynamic bearing comprises a fixed shaft having at least one end fixedly mountable to an apparatus in which the bearing is utilized, a rotary sleeve arranged coaxially with the fixed shaft so that a first fine gap is formed therebetween, a fixed sleeve arranged coaxially with the rotary sleeve so that a second fine gap is formed therebetween, and a lubrication oil filled in the fine gaps. The first fine gap and the second fine gap each have an open end exposed to air outside the bearing and an opposite end that is not exposed to the air, the opposite ends being in communication with each other. A holding member holds the fixed shaft and the fixed sleeve and is disposed adjacent to a lower end surface of the rotary sleeve to form a third fine gap between the holding member and the lower end surface of the rotary sleeve. The third fine gap is formed with a thrust dynamic pressure producing groove, and opposite ends of the first and second fine gaps meet each other through the third fine gap.

Abstract: In order to alleviate mutual interference between axial dynamic pressure portions and a radial dynamic pressure portion in a ring-like hydraulic dynamic pressure bearing, in the case of a ring-like hydraulic dynamic pressure bearing 1 constituted by supporting a shaft portion 4 constituted by fixing a ring 3 to an end portion 2A of a shaft main body 2 by a bearing portion 5, ring-like spaces 8 and 9 for storing lubricant for generating dynamic pressure are provided along contiguous portions of the radial dynamic pressure bearing portion and the axial dynamic pressure bearing portions formed between the ring 3 and the bearing portion 5, and the ring-like spaces 8 and 9 are maintained at atmospheric pressure via paths formed at the bearing portion 5 to thereby prevent negative pressure from generating at boundary regions of the two dynamic pressure bearing portions.

Abstract: The present invention is a double sleeve type fluid dynamic pressure bearing, comprising a fixed shaft having respective ends to be fixed to a utilized apparatus; a rotary sleeve arranged to provide a first fine gap between an inner peripheral surface thereof and an outer peripheral surface of the fixed shaft, a fixed sleeve arranged to provide a second fine gap between an inner peripheral surface thereof and an outer peripheral surface of the rotary sleeve, a holder member arranged to cooperate with a lower end surface of the rotary sleeve to provide a third gap, and wherein the first fine gap and the second fine gap are formed with radial dynamic pressure producing grooves while the third fine gap is formed with a thrust dynamic pressure producing groove, the first, second and third fine gaps being filled with lubrication oil, the first fine gap and the second fine gap having one ends made as opening ends contacting with the air and the other ends made as closed ends communicated with each other through the

Abstract: A hydraulic dynamic bearing has a rotational assembly and a bearing member for rotationally supporting the rotational assembly. The bearing member has a main body having a recess portion and a cover for covering an open end of the recess portion. The rotational assembly has a shaft main body having an end portion extending into the recess of the bearing main body for undergoing rotation relative thereto and a ring member disposed in the recess of the bearing main body. The ring member is connected to the end portion of the shaft main body for rotation therewith. Axial dynamic pressure generating grooves are formed in upper and lower surface portions of the ring member for generating axial dynamic pressure during rotation of the rotational assembly. Radial dynamic pressure generating grooves are formed in an outer peripheral surface portion of the ring member for generating radial dynamic pressure during rotation of the rotational assembly.

Abstract: A spindle motor has a rotor, a stator and a dynamic pressure bearing for supporting the rotor for rotation relative to the stator. The dynamic pressure bearing comprises a rotational shaft mounted for undergoing rotation and having a thrust bearing portion and a radial bearing portion. A bearing member rotatably supports the rotational shaft and has a closed end forming a small diameter cylinder portion for receiving the radial bearing portion of the rotational shaft and an open end forming a large diameter cylinder portion for receiving the thrust bearing portion of the rotational shaft such that first gaps for receiving a lubricating oil are formed between the rotational shaft and the bearing member. A thrust pressure member is connected to the bearing member to form a capillary seal between the rotational shaft and the open end of the bearing member and to form second gaps between the thrust pressure member and the rotational shaft for receiving a lubricating oil.

Abstract: A motor armature having a simplified assembly comprises an inner cylinder and an outer cylinder arranged coaxially, and a plurality of pole pieces provided radially at equal intervals between the inner and outer cylinders. The inner cylinder is formed into a cylindrical shape by curling up in the longitudinal direction a first hoop member (band steel) formed of a magnetic material and having a predetermined thickness and length. The outer cylinder is formed of a second hoop member similar to the first hoop member. The pole pieces each comprise a wire piece cut from a wire formed of a magnetic material and having a coil would thereon. One end of each pole piece is welded to one of the hoop members and the other end of the pole pieces is welded to the other hoop member.

Abstract: A spindle motor having a simplified construction with reduced axial and radial deflection while avoiding the half whirl phenomenon includes a motor frame, a rotating shaft supporting a rotor, a stator and stator coil, a permanent magnet opposing the stator, and a liquid dynamic pressure bearing. Magnetic centers of the permanent magnet and stator coil, in the axial direction of the rotating shaft, are substantially matched. The liquid dynamic pressure bearing comprises opposing surfaces of the rotating shaft and the housing. The rotating shaft has a disk-shaped thrust bearing portion disposed in a first portion of a cylindrical hole of the housing, and a radial bearing portion disposed in a second portion of the cylindrical hole. Lubricating oil fills a space between the cylindrical hole and the thrust bearing portion and radial bearing portion, and a presser ring is pressed and fixed into a third portion of the cylindrical hole to seal the bearing.

Abstract: A dynamic pressure bearing device comprises a rotary member mounted for rotation, and a dynamic pressure bearing rotatably supporting the rotary member. The dynamic pressure bearing has a stationary portion and a disk integrally connected to the stationary portion. The disk has surface portions defining thrust dynamic pressure bearing portions for supporting the rotary member in an axial direction and a radial dynamic pressure bearing portion for supporting the rotary member in a radial direction. A gap is disposed between the dynamic pressure bearing and the rotary member for receiving oil. A space is provided in fluid communication with the gap. The space has a central portion slanted downwardly in the radial direction for preventing leakage of the oil and has a diameter increasing gradually from the central portion in the radial direction.