JP4414047B2 - motor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a motor including a rotor main body facing in the axial direction (axial direction) with respect to a stator main body fixed to a frame.
[0002]
[Prior art]
Of this type of motor, a so-called flat motor with a small diameter and a small thickness, suitable for use in rotating a disk in a portable mini disk drive or the like, conventionally, the bearing has been formed of an oil-impregnated sintered metal or the like. In order to avoid leakage of oil from the bearing, the bearing housing is formed of a bottomed tubular body as a whole, and at least the bearing housing portion that supports the peripheral surface of the bearing is made of metal.
[0003]
[Problems to be solved by the invention]
However, when the bearing is press-fitted into the bearing housing made of a bottomed cylindrical body and the rotor rotation shaft is further inserted into the bearing, there is no air escape space, so the shaft insertion is not easy. Or the bearing may be returned. If an air escape groove is formed on the peripheral surface of the bearing sintered body, the sintered body bearing may be weakened excessively. In addition, attempting to form the axial groove on the small-diameter inner peripheral surface of the metal cylindrical portion of the bearing housing requires special processing and may increase the cost. On the other hand, in a flat motor in which the rotor faces the stator in the axial direction (axial direction), a permanent magnet that exerts a magnetostatic attractive force on a yoke member that forms part of the rotor in order to regulate the displacement of the rotor. Is preferably arranged.
[0004]
The present invention has been made in view of the above-mentioned points, and an object thereof is to reinforce the bearing housing while minimizing the positional deviation of the rotor with a permanent magnet in a state where the occupied space is minimized. The object is to provide a motor that can be obtained.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the motor of the present invention is a motor having a rotor body portion facing in the axial direction with respect to a stator body portion fixed to the frame, and is a thick wall fixed to the bottom wall of the frame. A plastic bearing housing having a cylindrical portion and a thin cylindrical portion substantially concentric with the thick cylindrical portion, and an integral body of the rotor body that is fitted into the thin and thick cylindrical portions of the bearing housing Journal bearing that rotatably supports a typical rotating shaft, and an annular ring that is fitted to the outer periphery of the thin cylindrical portion at a position close to the yoke portion integral with the rotor main body portion in order to suppress displacement of the rotor main body portion. Permanent magnet. Each cylindrical portion typically has a circular cylindrical cross section (however, the outer peripheral surface may be slightly decentered with respect to the inner peripheral surface or the diameter may vary depending on the axial position if desired). Consists of.
[0006]
In the motor of the present invention, since the permanent magnet for restricting the positional deviation of the rotor main body portion is provided, the axial direction (also referred to as “axial direction” in this specification) relative to the stator main body portion fixed to the frame is provided. Since the positional deviation of the facing rotor main body with respect to the stator main body can be suppressed, the stability of the rotational drive with respect to the rotor main body can be ensured. The positional shift includes an axial position shift and a radial position shift, and the permanent magnet has one of two position shift positions (that is, an axial position shift or a radial position shift). ) Or both (axial misalignment and radial misalignment). Axial misalignment is typically suppressed by providing a cylindrical member that faces the outer peripheral surface of the annular permanent magnet in a radial direction on a yoke member integral with the rotor body. The annular permanent magnet is disposed at a position shifted downward from the center of the cylindrical portion in the axial direction, and exerts a downward magnetostatic force on the cylindrical portion. The annular permanent magnet may be located below the lower end of the cylindrical part, even if the lower end part is in a position facing the cylindrical part of the yoke member in the radial direction. In some cases, the upper end portion of the annular permanent magnet may be positioned below the lower end of the cylindrical portion of the yoke member. However, the magnitude of the downward force on the cylindrical portion of the yoke member is determined by the yoke member. The upper end portion of the annular permanent magnet is positioned above the lower end portion of the cylindrical portion of the yoke member so that the upper end portion of the annular permanent magnet is shifted upward (so that at least a part of the outer peripheral surface including the upper end of the annular permanent magnet Facing the cylindrical part of the yoke member in the radial direction).
[0007]
Throughout this specification, “below” refers to the side of the bottom wall of the frame, unless otherwise specified. However, although it is a preferable example that the bottom wall of the frame is disposed below the rotating shaft of the motor (the rotating shaft of the rotor structure) on the ground, it is not intended to be limited thereto. In another preferred example of the present invention, for example, the bottom wall of the frame is positioned above the ground, and the projecting end of the motor rotating shaft opposite to the insertion end inserted into the bearing is viewed on the ground. A turntable is attached to the protruding end at the lower end, and the media such as optical disks (including magneto-optical disks) and magnetic disks are located below (when viewed from the ground). Place the motor so that it can be mounted on the turntable.
[0008]
Further, in the motor of the present invention, since the cylindrical portion of the bearing housing fitted with the annular permanent magnet that suppresses the displacement of the rotor main body portion is formed thin, the inner diameter of the permanent magnet can be minimized. Therefore, the outer diameter of the permanent magnet can be minimized, and the restrictions imposed on the shape and occupied space of the yoke portion of the rotor by the annular permanent magnet can be minimized. Furthermore, in the motor of the present invention, the weakening of the cylindrical portion due to the thinning of a part of the cylindrical portion of the bearing housing can be reinforced by the annular permanent magnet fitted to the thin cylindrical portion. Can be formed of a plastic material such as engineering plastic. Examples of the annular permanent magnet include a so-called plastic magnet (hard magnetic material powder (or particles) hardened with resin and magnetized) or sintered magnet (hard magnetic material powder (or particles) sintered and magnetized. Can be used. However, it may be made of other materials.
[0009]
[Means for Solving the Problems]
  In order to achieve the above object, the motor of the present invention is a motor having a rotor body portion facing in an axial direction with respect to a stator body portion fixed to a frame,The inner peripheral surface is a common cylindrical shapeThick cylindrical part andThinPlastic bearing housing with a meat tubeThe thick cylindrical portion is fixed to the bottom wall of the frame, and the thin cylindrical portion has an outer peripheral surface that is eccentric with respect to the inner peripheral surface, and the thick cylindrical portion and the thin cylindrical portion are A groove continuously extending in parallel with the axis over substantially the entire area in the axial direction of the inner peripheral surface;A journal bearing that is inserted into the thin and thick cylindrical portions of the bearing housing and rotatably supports a rotating shaft that is integral with the rotor main body, and integral with the rotor main body to suppress displacement of the rotor main body. Fitted to the outer periphery of the thin cylindrical portion at a position close to the yoke portion.Reinforce the thin cylindrical partAnnular permanent magnetThe outer peripheral surface and the inner peripheral surface are concentric and the outer peripheral surface is decentered with respect to the axis of rotation of the rotorAnd have.
  Each cylindrical portion typically has a circular cylindrical cross section (however, the outer peripheral surface may be slightly decentered with respect to the inner peripheral surface or the diameter may vary depending on the axial position if desired). Consists of.
  In this specification, a method of manufacturing a winding coil of a flat conductor that does not satisfy the conditions described in this paragraph is out of the scope of the claims.
[0010]
Thus, when the cylindrical portion of the bearing housing is actually liquid-tightly sealed at the bottom thereof, the higher the degree of sealing, the more the journal bearing and the rotating shaft of the motor in the cylindrical portion of the bearing housing. When inserting, the air escape path in a bottomed cylindrical part which should be excluded with this insertion is required. In the motor of the present invention, since the bearing housing is formed of a plastic material by using an annular permanent magnet that restricts the axial movement of the rotor body, the cylindrical shape of the bearing housing is also formed. Mold molding using a mold, typically outsert molding using the bottom wall of the frame as an injection hole or injection hole for the plastic material to be molded, and so on. An air escape groove can be easily and reliably formed on the inner peripheral surface of the cylindrical portion. Here, for example, the inner diameter of the cylindrical portion of the bearing housing (the inner diameter of the hole in the housing) is typically about 1 to 5 mm, and it is particularly difficult to form a groove by cutting or the like. It is beneficial. However, the inner diameter of the cylindrical portion may be smaller or larger. Note that the axial length of the cylindrical portion of the bearing housing is typically about 1 to 10 mm. However, it may be longer or shorter.
[0011]
Therefore, the motor of the present invention typically has an air escape extending continuously over substantially the entire area in the axial direction of both cylindrical portions on the inner peripheral surfaces of the thin and thick cylindrical portions. Has a groove for use. As a result, when the journal bearing and the rotating shaft of the motor are inserted into the cylindrical portion of the bearing housing, the air in the bottomed cylindrical portion that should be removed along with the insertion is transferred to the inner peripheral surface of the cylindrical portion of the bearing housing. Since it can be discharged to the outside through the formed groove (that is, the passage formed between the inner peripheral surface of the cylindrical portion of the bearing housing and the outer peripheral surface of the journal bearing), it can be discharged to the outside. In a typical case where the rotation axis is inserted later, the rotation axis) can be easily and reliably inserted to a predetermined depth. In this case, there is no possibility that the strength of the bearing will be reduced as compared with the case where grooves are formed on the outer peripheral surface of the relatively fragile bearing.
[0012]
The grooves may extend in parallel to the axial direction, for example, may be bent, or may intersect each other when there are a plurality of grooves. When the grooves are provided in parallel with the axis, typically, a plurality of grooves are formed at equal intervals in the circumferential direction. As a result, it can be avoided that the bearing is pressed toward one groove or a specific groove and is eccentric. However, when it is intentionally desired to be decentered to some extent in a specific direction, grooves may be provided only in the specific direction or the occupied area (or distribution density) of the grooves in the direction may be increased.
[0013]
In the motor of the present invention, typically, an outer diameter that is smaller than the outer diameter of the annular permanent magnet and intermediate between the outer diameters of the two cylindrical portions is provided between the thin cylindrical portion and the thick cylindrical portion. The provided annular step portion is formed, and the end face of the annular permanent magnet is in contact with the annular step portion in the vicinity of the radially inner peripheral edge. In this case, it corresponds to the axial length (height) of the annular step portion between the lower end surface of the annular permanent magnet and the upper end surface of the thick cylindrical portion, except in the vicinity of the radially inner periphery of the annular permanent magnet. An axial gap of a size is formed. In this case, even if an impact load is applied to the frame due to the dropping of the device including the motor, the impact is absorbed by the bending deformation within the elastic limit of the annular stepped portion (note that the annular stepped portion has a thin cylindrical shape on the one hand) Since it is thicker and larger in diameter than the part, there is little possibility of bending due to the impact). Therefore, since it is possible to minimize the excessive impact on the thin cylindrical portion and the annular permanent magnet fitted to the thin cylindrical portion, there is little possibility of cracking even when the annular permanent magnet is relatively fragile. . Furthermore, even when the legs of the bearing housing are fixed to a plurality of holes (openings) provided in the bottom wall of the frame by molding, the bending between the holes due to bending deformation within the elastic limit of the annular stepped portion Since the stress applied to the bridge portion can be minimized, there is little possibility that the bottom wall portion of the frame is bent.
[0014]
In the motor according to the present invention, typically, the outer circumferential surface and the inner circumferential surface of the thin cylindrical body are circular in cross section, and the outer circumferential surface of the annular permanent magnet is eccentric with respect to the axis of the rotation shaft of the rotor. . This makes it possible to move the rotating shaft of the motor to one side of the bearing hole, so that the rotating shaft is practically constant even when the difference between the outer diameter of the rotating shaft and the inner diameter of the bearing is relatively large. Can be rotated around the axis. For this purpose, even if the permanent magnet is an annular body having an outer peripheral surface eccentric to the inner peripheral surface (slightly eccentric), the thin cylindrical portion of the bearing housing is A cylindrical body having an outer peripheral surface that is eccentric (and slightly eccentric), and in some cases, a cylinder in which the bearing has an outer peripheral surface that is eccentric with respect to its inner peripheral surface (slightly eccentric) It may be a body. Typically, the thin cylindrical portion of the bearing housing that is relatively easy to mold is eccentric.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Next, a preferred embodiment of the present invention will be described based on a preferred example shown in the accompanying drawings. In the description of the embodiments, the size is described as a typical example, but the invention is not intended to be limited to a size of the same size as the described size.
[0016]
【Example】
A motor 1 according to a preferred embodiment of the present invention shown in FIGS. 1 to 4 is used as a part of a mini-disk drive for a mechanical deck for mini-disk rotation driving, and has a frame structure as a frame or a frame. A body structure 10, a stator structure 40 fixed to the frame structure 10, and a rotor structure 50.
[0017]
The frame structure 10 is made of a metal frame bottom wall or a flat-plate chassis 11 as a bottom frame portion, and is made of plastic, and is a substantially cylindrical portion that forms a side wall portion as a side portion or an outer peripheral frame portion fixed to the chassis 11. And an annular side wall member 12. For example, the chassis 11 made of steel such as stainless steel having a thickness of about 0.5 mm includes a shaft support portion 13 serving as a thrust bearing, and a plurality of members formed around the shaft support portion 13 at intervals in the circumferential direction. And a hole 14. Therefore, in the chassis 11, the chassis main body 15 and the shaft support portion 13 that have spread outside the group of engaging holes 14 arranged in the circumferential direction are between the engaging holes 14, 14 adjacent in the circumferential direction. They are connected by a bridge or bridge 16. The engagement hole 14 has a diameter of about 1 to 1.5 mm, for example, and the centers of the engagement holes 14 are distributed at equal intervals in the circumferential direction along a circle of about 4 mm in diameter, for example. In this example, the lower edge 17 of the inner peripheral surface of each engagement hole 14 is chamfered. As shown in FIGS. 1 and 3, the side wall 12 has a horizontal mounting surface 12a and an information reading / writing pickup portion of a mini-disc made of a magneto-optical disc that are closely spaced in the A direction. A positioning wall portion 18 having a partially cylindrical positioning surface 18a rising vertically is provided except for a peripheral region and a peripheral region where a terminal portion of a stator substrate described later should protrude. In FIG. 2, a hole 14a in the chassis 11 is for fixing the side wall 12 to the chassis 11, and a hole 14b is for fixing the chassis 11 and other members.
[0018]
A bearing housing 20 made of engineering plastic such as PBT (polybutylene terephthalate) resin or PC (polycarbonate) resin that can be molded by injection molding or the like is placed and fixed on the shaft support portion 13 of the chassis 11. The bearing housing 20 includes a thin cylindrical portion 21 as a thin cylindrical portion, and a thick cylindrical portion as a thick cylindrical portion that extends integrally and substantially concentrically downward from the lower end of the thin cylindrical portion 21. And a plurality of leg portions 23 as a plurality of engaging projections extending downward from the outer peripheral portion of the lower end of the thick cylindrical portion 22. Between the thin cylindrical portion 21 and the thick cylindrical portion 22, an annular step portion 39 having a slightly larger diameter and a lower height in the axial direction than the thin cylindrical portion 21 is formed. The thin cylindrical portion 21 has an outer diameter of, for example, about 3 mm, an inner diameter of about 2 mm, and a height of, for example, about 2 mm. The thick-walled cylindrical portion 22 has an outer diameter of, for example, about 4.5 to 5 mm, and has a height of about 2 mm. For example, it is about 1 mm. The stepped portion 39 has a height of, for example, about 0.1 mm and a diameter that is larger than the outer diameter of the thin cylindrical portion 21 by, for example, about 0.3 to 0.5 mm.
[0019]
The inner peripheral surface 24 of the thick-walled cylindrical portion 22 and the thin-walled cylindrical portion 21 includes an air vent groove 25 and a thick-walled cylindrical portion that extend substantially parallel to the central axis C along the longitudinal direction of the inner peripheral surface 24. Except for the inward annular protrusion 27 at the lower end of 22, a substantially columnar or cylindrical hole or chamber 26 is formed as a whole. The groove 25 is, for example, substantially semicircular when viewed in a cross section perpendicular to the axis C. However, the shape may be any other shape as long as the cross-sectional area is relatively large so that air can escape (there is a depth equivalent to the width). In FIG. 1, only one groove portion 25 is shown (visible), but three groove portions 25 are formed at intervals of 120 degrees in the circumferential direction. The groove portions 25 formed at equal intervals in the circumferential direction are such that when the bearing and the rotating shaft are inserted into the holes of the bearing housing 20, the bearing housing 20 is distorted unevenly, and the central axis of the bearing and the rotating shaft is on one side. Helps minimize slippage. In addition, when the groove part 25 extends in parallel with the axis C, the groove part 25 may be two (180 degree intervals) or four or more as long as it is formed at equal intervals in the circumferential direction. As long as the groove 25 is continuously connected over the entire region in the axial direction C from the lower end to the upper end of the inner peripheral surface 24, the groove 25 may extend in an oblique direction such as a spiral instead of being parallel to the axis C. , May cross. However, in order to support the bearing firmly and stably, it is preferable that the area that the groove portion 25 occupies the inner peripheral surface 24 is a minimum.
[0020]
In the example shown in FIG. 1, the outer peripheral surface 21 a of the thin-walled cylindrical portion 21 is slightly eccentric with respect to the inner peripheral surface 24. That is, in the case of FIG. 1, the remaining two groove portions 25, in other words, so that the thickness is maximized in the left portion 21 c that overlaps one of the three groove portions 25 in the radial direction. 25 (both not shown) is eccentric so that the thickness in the radial direction between the inner peripheral surface 24 and the outer peripheral surface 21a is minimized at the right wall portion 21d located in the middle. The position where the maximum eccentric portion overlaps the groove portion 25 in the radial direction may be shifted in the circumferential direction. In this example, the thick cylindrical portion 22 is not eccentric with respect to the inner peripheral surface 24, but the thick cylindrical portion 22 may also be eccentric in the same manner as the thin cylindrical portion 21, for example. However, when a permanent magnet, which will be described later, fitted to the thin cylindrical portion 21 has an outer peripheral surface that is eccentric with respect to the inner peripheral surface, the outer peripheral surface 21a of the thin cylindrical portion 21 is: It does not have to be eccentric with respect to the inner peripheral surface 24.
[0021]
The thick cylindrical portion 22 is in liquid-tight contact with the upper surface 13a of the shaft support portion 13 of the chassis 11 at the lower surface 22a, and actually seals the lower end of the chamber 26. The shape is practically complementary to the corresponding engagement hole 14. The bearing housing 20 is engaged with the chamfered portion 17 at the lower end of the engagement hole portion 14 at the leg portion 23, and the leg portion 23 has a frustoconical engagement edge portion extending downward at the lower end. 23a. Each engagement hole 14 and leg 23 have the same shape so as to overlap each other by virtual rotation around the axis C. The bearing housing 20 is preferably formed by outsert molding by injecting a thermoplastic engineering plastic material into the mold from the hole 14 in a state where the chassis 11 is arranged in the molding die so as to form a part of the mold. Is done.
[0022]
As long as the bearing housing 20 can be fixed by fixing the leg portion 23 by the engagement hole 14 so that the engagement protrusion 14 and the corresponding engagement protrusion 23 are complementary, the plurality of engagement holes 14 are provided. Each of the engagement protrusions 23 may have a different shape. In the illustrated example, the outer peripheral surface 22b of the thick cylindrical portion 22 and the upper surface 23b of the leg portion 23 intersect at right angles between the thick cylindrical portion 22 and the leg portion 23. As long as the rotation of the thick cylindrical portion 22 is not hindered, the thick cylindrical portion 22 is, for example, a truncated cone shape that can avoid stress concentration, as shown by an imaginary line 29, and a shape that is continuously connected to the leg portion 23. Good.
[0023]
In the substantially annular space formed by the upper end surface 22 c of the thick cylindrical portion 22, the annular step portion 39, and the outer peripheral surface 21 a of the thin cylindrical portion 21, an annular shape fitted to the thin cylindrical portion 21 is provided. A permanent magnet 30 is provided. The permanent magnet 30 is made of, for example, a plastic magnet or a sintered magnet. The permanent magnet 30 has an inner diameter that is substantially the same as the outer diameter of the thin cylindrical portion 21, and the lower end surface 31 of the permanent magnet 30 abuts on the upper surface of the annular step portion 39 in the vicinity of the inner peripheral edge. A small axial gap G corresponding to the height of the stepped portion 39 is formed between the upper end surface 22c of the thick cylindrical portion 22 and the upper end surface 22c of the thick-walled cylindrical portion 22 over the most radial region of the lower end surface 31. ing. The length of the gap G in the axial direction corresponds to the height of the stepped portion 39 described above, and is about 0.1 mm, for example. The annular or annular permanent magnet 30 has an outer diameter of, for example, about 5 mm and a height of about 1.5 mm.
[0024]
Note that the upper end 32 of the permanent magnet 30 is typically located at the same height as the upper end 21 b of the thin cylindrical portion 21 so that the thin cylindrical portion 21 can be reinforced. However, depending on the case, it may be slightly lower or higher than the upper end 21b of the thin cylindrical portion 21.
[0025]
Further, the permanent magnet 30 has an annular shape in which the inner peripheral surface 30a and the outer peripheral surface 30b are concentric, and the outer peripheral surface 21a of the thin cylindrical portion 21 is eccentric to the part 21c side. In the wall section cross section 30c located on the left side of the wall section section 30d located on the right side, the outer peripheral surface 30b is located at a position further away from the axis C (radially outward). The annular or ring-shaped permanent magnet 30 may also be eccentric like the thin cylindrical portion 21 of the bearing housing 20. When the thin cylindrical portion 21 of the bearing housing 20 is not eccentric, the annular permanent magnet 30 is formed in a shape in which the outer peripheral surface 30b is eccentric with respect to the inner peripheral surface 30a.
[0026]
The permanent magnet 30 is magnetized in the radial direction, for example. However, it may be magnetized in one direction or in a direction parallel to the axis C in a horizontal plane perpendicular to the axis C.
[0027]
On the other hand, a cylindrical bearing member 35 made of an oil-impregnated sintered body is fitted in the chamber 26 of the bearing housing 20. The lower end surface of the bearing member 35 abuts on the inward annular protrusion 27 at the lower end of the thick cylindrical portion 22 of the bearing housing 20, and is slightly separated from the upper surface 13 a of the shaft support portion 13. The cylindrical outer peripheral surface 36 of the bearing member 35 and the inner peripheral surface 24 of the thin and thick cylindrical portions 21 and 22 of the bearing housing 20 are practically in close contact except for the groove portion 25.
[0028]
On the side wall or the peripheral wall 12 of the frame 10, the stator substrate 41 of the stator structure 40 is disposed and fixed in contact with and positioned on the positioning surface 18 a at a part of the peripheral surface. The stator structure 40 has a substantially trapezoidal stator coil arranged in the circumferential direction so as to be energized by a stator substrate 41 and a printed wiring 42 on the stator substrate 41 as shown in FIG. 43. In the illustrated example, among the six coils 43 serving as the stator body, coil pairs 43A, 43A; 43B, 43B; 43C, 43C facing in the diameter direction are connected in series. However, the number of the coils 43 may be larger or smaller. Reference numerals 42A, 42B, 42C, and 42G denote terminals or pad portions of the wiring 42. The total thickness of the stator structure 40 is, for example, about 0.5 mm.
[0029]
The rotor 50 includes a motor shaft or a rotor rotation shaft 51 that is rotatably fitted to the bearing 35, an upper rotor structure 52 that is fitted to the rotor rotation shaft 51, and a lower portion that is fixed to the upper rotor structure 52. Side rotor structure 53.
[0030]
The upper rotor structure 52 includes an upper yoke made of a soft magnetic material having a central cylindrical portion 54 into which the rotating shaft 51 is press-fitted and fitted, and a disc-like portion 55 extending horizontally from the lower end of the cylindrical portion 54. A member 56 and a side wall 59 engaged with the engagement hole 57 of the upper yoke member 56 by the engagement leg 58 and extending downward so as to embrace the outer peripheral edge of the upper yoke member 56; An engineering plastic turntable portion having an annular plate 63 (FIG. 1) provided with disk engaging claws 60, 61, 62 (FIGS. 1 and 3) in the form of springs spaced in the direction. 64 and an annular multi-piece as a rotor main body portion fitted in the annular side wall portion 59 of the turntable portion 64 so as to be in close contact with the lower surface 65 of the upper yoke member 56 at the upper surface 66 and face the stator coil 43 in the axial direction. very A rotor magnet 67 made of a permanent magnet structure (in FIG. 4 (b)) and. The upper yoke member 56 has a thickness of about 0.5 mm, for example, and the rotor magnet 67 has an outer diameter of about 14 mm, an inner diameter of about 7 mm, a thickness of about 1 mm, and a gap of about 0.2 mm, for example. The stator structure 40 is faced in a direction parallel to the axial direction. An annular permanent magnet 69 magnetically attracts the magnetic material portion on the lower surface of the disk to engage and align the disk with the spring claws 60 to 62 through its central opening (hole) and to fix the disk to the turntable 64. To do.
[0031]
The lower rotor structure 53 is formed of a lower yoke member 70 made of a soft magnetic material. The lower yoke member 70 includes an inner annular plate portion 71 that is magnetostatically attracted and fixed to the lower surface of the inner peripheral portion of the disk-like portion 56 of the upper yoke member 54 of the upper rotor structure 52, and the inner annular plate. A cylindrical part 73 extending downward from the outer peripheral edge 72 of the part 71 and a radially outwardly extending upper end 75 from the lower end or lower edge 74 of the cylindrical part 73 face the stator coil 43 of the stator substrate 40 in the axial direction. And an outer annular plate portion 76. The lower yoke member 70 also has a thickness of about 0.5 mm, for example, and faces the stator structure 40 in a direction parallel to the axial direction through a gap of about 0.2 mm, for example. The lower surface 77 of the inner annular plate portion 71 is positioned above the top surface 32 of the permanent magnet 30 by, for example, about 0.2 mm, and the lower surface 78 of the outer annular plate portion 76 is more than the bottom surface 31 of the permanent magnet 30. For example, it is positioned about 0.05 to 0.1 mm below the upper end of the curved lower edge 74 by about 0.1 to 0.2 mm. Therefore, when the outer peripheral surface 30 b of the permanent magnet 30 is shifted below the central portion in the vertical direction Z of the inner peripheral surface 79 of the cylindrical portion 73 of the lower yoke member 70, the radius is set to the cylindrical portion 73. Facing each other. As a result, the annular permanent magnet 30 exerts a downward Z1 force on the lower yoke member 70 in the entire vertical direction Z. However, as long as the inner annular plate portion 71 of the lower yoke member 70 is relatively separated from the permanent magnet 30, the force in the Z1 direction increases as the lower yoke member 70 shifts upward from the predetermined position to Z2. Note that the lower surface 78 of the outer annular plate portion 76 may be located above the lower surface of the annular permanent magnet 30.
[0032]
In the motor 1 according to a preferred embodiment of the present invention configured as described above, when assembling, the material of the leg portion 23 is filled in the hole 14 of the chassis 11, and the leg portion 23 and the thick cylindrical portion. 22 in the hole 26 of the bearing housing part 20 formed outsert integrally with the chassis 11 so as to embrace the shaft support part 13 of the chassis 11. A bearing member 35 made of an oil-impregnated sintered body is press-fitted until it comes into contact with the upper surface of the steel. By this press-fitting, between the outer peripheral surface 36 of the bearing member 35 and the inner peripheral surface (that is, the peripheral surface or peripheral wall of the hole 26) 24 of the bearing housing 20, a portion of the groove 25 (and the bearing member 35 as shown in FIG. 1). In the case where the outer peripheral edge of the lower end is chamfered, it is in close contact with the entire area except for the chamfered portion). In the motor 1, the axial grooves 25 of the bearing housing 20 are formed at equal intervals in the circumferential direction, so that there is little possibility that the bearing member 35 is eccentric to the side where the one groove 25 is present during press-fitting. A small axial gap is formed between the lower end surface of the bearing member 35 and the upper surface 13 a of the shaft support portion 13 of the chassis 11. This axial gap is connected to the outside via an axial insertion hole defined by the inner peripheral surface 37 of the bearing member 35 on the inner peripheral side, and connected to the outside via a groove 25 on the outer peripheral side. The size of the axial gap is about 0.2 mm in this example, but may be a little larger or smaller.
[0033]
Next, the thin cylindrical portion 21 of the bearing housing 20 is press-fitted into the annular plastic magnet 30 until the lower end surface of the annular plastic magnet 30 comes into contact with the upper surface of the annular step portion 39 of the bearing housing 20. 30 is fitted into the thin cylindrical portion 21. Since the outer peripheral surface 21a of the thin-walled cylindrical portion 21 is slightly eccentric with respect to the axis C, the outer peripheral surface 30b of the cylindrical magnet 30 is the right cross-sectional portion shown in FIG. It is located slightly away from the axis C rather than 30d.
[0034]
Next, after the lower yoke member 70 is disposed and the stator structure 40 is placed and fixed on the side wall 12 of the frame 10, the rotating shaft 51 of the motor 1 is inserted into the bearing member 35. When the rotary shaft 51 is inserted, the air in the region surrounded by the rotary shaft 51, the bearing member 35, and the shaft support portion 13 of the chassis 11 is separated from the gap at the inward annular protrusion 27 of the thick cylindrical portion 22 and Since it can be discharged to the outside through the groove 25, the bearing member 35 is pushed out of the hole of the bearing housing 20 even if the bearing member 35 and the rotary shaft 51 are formed in such a size that they are in close contact with each other without any gap. The rotating shaft 51 can be inserted into the bearing member 35 without any problem. When the rotary shaft 51 is inserted, the lower yoke member 70 is attracted to the upper yoke member 56 integral with the rotor magnet 67 and the rotary shaft 51 by magnetostatic attraction. At this time, the lower yoke member 70 is a lower end of three spring claws 68a, 68b, 68c (68b, 68c are not shown) formed on the inner peripheral portion of the annular plate 63 at intervals in the circumferential direction. The protruding portion is pushed inward in the radial direction by the tapered portion 70a of the inner peripheral upper edge of the inner annular plate portion 71 so as to cross the lower end protruding portion such as the spring pawl 68a in the Z2 direction, and is adsorbed to the lower surface of the upper yoke member 56, It is aligned and locked by a spring claw 68a or the like that has returned to its original position radially outward.
[0035]
In the motor 1 in the state of FIG. 1 in which the entire assembly has been completed, the thin cylindrical portion 21 of the bearing housing 20 is reinforced by the annular permanent magnet 30, so that the bearing member 35 can be firmly supported by the bearing housing 20. The movement of the bearing member 35 such that the central axis C of the bearing member 35 swings can be minimized under a non-uniform radial load within a range where the bearing member 35 may normally be applied. .
[0036]
Further, in the motor 1, since the axial gap G is formed between the annular permanent magnet 30 and the thick cylindrical portion 22, for example, due to an unexpected drop of the mini disk drive including the motor 1, for example, the chassis 11. Even when an impact load is applied to the chassis 11 in a direction crossing the extending plane, the load or stress generated between the rotor structure 50 and the chassis 11 is mainly the annular stepped portion 39 having the gap G. Therefore, the impact load can be actually absorbed by the deflection within the elastic limit of the annular step 39. As a result, the permanent magnet ring 30 is broken by the load applied to the annular permanent magnet 30 through the thin cylindrical portion 21 or directly, or the bridge is applied by the load applied to the bridging portion 16 of the shaft support portion 13 of the chassis 11. There is little possibility that the tangled portion 16 is deformed such that it is bent at the end or the like. If there is a possibility that excessive stress is concentrated on the connecting portion between the thick cylindrical portion 22 and the leg portion 23 of the bearing housing 20, as described above, the outer periphery of the thick cylindrical portion 22 is For example, a shape that can avoid stress concentration as indicated by an imaginary line 29 may be used.
[0037]
Further, in this motor 1, the outer peripheral surface 30b of the annular permanent magnet 30 is farthest from the axis C on the left side (at the cross section 30c) and closest to the axis C on the right side (at the cross section 30d). Thus, the outer peripheral surface 30b is close to the axis C, so that it is closest to the cylindrical portion 73 of the lower yoke member 70 of the rotor structure 50 on the outer periphery of the cross-sectional portion 30c (the size of the gap in the radial direction). For example, about 0.1 mm), and the outermost part of the cross-sectional portion 30d is farthest away (the radial size of the gap is about 0.2 mm, for example). Exerts a biasing force. As a result, in FIG. 1, the rotor structure 50 is maintained in a state in which the right edge of the outer peripheral surface of the rotating shaft 51 is in contact with the facing portion of the inner peripheral surface 24 of the bearing member 35. Therefore, even with a slight gap remaining between the outer peripheral surface of the rotating shaft 51 and the inner peripheral surface of the bearing member 35, the rotating shaft is less likely to rotate while being irregularly shaken, and the rotating axis C is practically constant. Easy to keep in position and orientation. Even if the rotation axis C of the rotating shaft 51 receives a force in a direction to tilt, the direction in which the upper portion of the shaft 51 tilts to the left is practically prioritized. The direction of the axis C is limited and is easy to stabilize. In the motor 1, since a gap is formed between the lower end surface of the bearing member 35 and the upper surface 13 a of the shaft support portion 13, the bearing member 35 is supported by the lower end of the shaft 51 even when the shaft 51 tilts. There is no risk of damaging the lower end.
[0038]
Furthermore, in the motor 1, the annular permanent magnet 30 has a lower end 31 positioned in the vicinity of the lower end portion of the cylindrical portion 73 of the lower yoke member 70 and sufficiently below the upper end portion of the cylindrical portion 73. Therefore, the rotary shaft 51 comes out of the bearing member 35 without exerting an excessive downward force on the lower yoke member 70 that presses the lower end of the rotary shaft 51 against the shaft support portion 13 with an excessive thrust force (load). Can be suppressed.
[0039]
In the motor 1 having the ease of assembly and the rotation characteristics during the rotation operation as described above, when the mini disc cartridge is placed near a predetermined position on the turntable 64, the iron plate portion of the mini disc of the mini disc cartridge is caused by the magnet 69. The peripheral wall of the central opening of the mini disk is attracted to bias the spring claws 60 to 62 and fitted around the spring claws 60 to 62. After the mini disk cartridge is completely mounted, the multipolar permanent magnet structure is removed. The rotor structure 50 having a closed magnetic path composed of the rotor magnet 67 and the upper and lower yoke members 56, 70 has a three-phase configuration to the stator coils 43A, 43B, 43C via the terminal portions 42A, 42B, 42C, 42G. With the energization of the drive current at, it is rotated according to the energization current. Further, the pickup section can be scanned in the radial direction in the A direction in a region where the rising side wall portion 18 is not (notched), and can perform desired reading (reproduction), writing (recording, etc.), erasing, and the like.
[0040]
In the above, an example in which the motor 1 is applied to a mini disk drive has been described. However, the motor 1 may be used for any other application as long as it is suitable for use with a flat motor. In addition, the motor of this invention may be formed as motors other than a flat motor.
[Brief description of the drawings]
FIG. 1 is a cross-sectional explanatory view taken along the line II of FIG. 3A of a motor according to a preferred embodiment of the present invention.
2 is an explanatory plan view of a chassis of the motor shown in FIG. 1; FIG.
FIGS. 3A and 3B are external views of the motor of FIG. 1, in which FIG. 3A is an explanatory plan view, and FIG.
4A and 4B show a stator and a rotor magnet of the motor of FIG. 1, in which FIG. 4A is a plan view of a stator structure, and FIG. 4B is a plan view of a multipolar rotor magnet.
[Explanation of symbols]
1 Motor
10 Frame structure
11 Chassis
13 Shaft support
14 engagement hole
15 Chassis body
16 Bridge part (bridge part)
17 Lower edge (chamfered part)
20 Bearing housing
21 Thin cylindrical part (thin cylindrical part)
21a (Eccentric) outer peripheral surface
22 Thick cylindrical part (thick cylindrical part)
22a bottom
22c upper surface
23 legs
23a Engagement edge
24 inner circumference
25 Groove
26 rooms (holes)
27 Inward annular projection
30 toroidal permanent magnet
30a Inner peripheral surface
30b Outer peripheral surface
31 Lower end surface
35 Bearing members
36 outer peripheral surface
37 Inner peripheral surface
39 Annular steps
40 Stator structure
41 Stator substrate
43, 43A, 43B, 43C Stator coil
50 Rotor structure
51 Rotating shaft
52 Upper rotor structure
53 Lower rotor structure
56 Upper yoke member
60, 61, 62 engaging claw
64 turntable
67 Rotor magnet (multi-pole permanent magnet structure)
70 Lower yoke member
71 Inner annular plate
73 Cylindrical part
76 Outer annular plate
79 Inner surface
C Center axis
G gap
Z1 downward
Z2 upward
Z Vertical direction

Claims (5)

A motor having a rotor body facing in the axial direction with respect to a stator body fixed to a frame,
The inner circumferential surface a plastic bearing Haujin grayed having a common thick cylindrical portion及beauty thin walled tubular portion is cylindrical, fixed to the bottom wall of the frame in thick cylindrical portion, thin The cylindrical portion has an outer peripheral surface that is eccentric with respect to the inner peripheral surface, and is continuous in parallel with the axis over substantially the entire axial direction of the inner peripheral surface of the thick cylindrical portion and the thin cylindrical portion. With a groove extending to
A journal bearing which is inserted into the thin and thick cylindrical portion of the bearing housing and rotatably supports a rotating shaft integral with the rotor body portion;
An annular permanent magnet which is fitted on the outer periphery of the thin cylindrical portion and is reinforced on the outer periphery of the thin cylindrical portion at a position close to the yoke portion integral with the rotor main body portion in order to suppress displacement of the rotor main body portion. A motor having a surface and an inner peripheral surface that are concentric and the outer peripheral surface is eccentric with respect to an axis of a rotation shaft of the rotor . The motor according to claim 1, wherein the groove is formed at a position away from a portion having a minimum radial thickness in the circumferential direction in the thin cylindrical portion . The plurality of grooves are formed at equal intervals in the circumferential direction, and when there are three grooves, one of the grooves is formed at a portion of the thin cylindrical portion where the thickness is maximum. Motor.   Between the thin cylindrical portion and the thick cylindrical portion, an annular step portion having an outer diameter that is smaller than the outer diameter of the annular permanent magnet and intermediate between the outer diameters of the two cylindrical portions is formed. The motor according to any one of claims 1 to 3, wherein an end surface of the annular permanent magnet is in contact with the annular step portion in the vicinity of the radially inner peripheral edge. Thick tubular portion of any one of claims 1, which is fixed to the bottom wall of the frame by a plurality of legs engaged with the plurality of engaging holes formed in the bottom wall of the frame to the 4 The motor according to item.

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