JP3804685B2 - motor - Google Patents

Description

 The present invention is used for rotationally driving a recording disk such as a magnetic disk or an optical disk, and a shaft is rotatably inserted into a sleeve, and a herringbone groove for generating radial dynamic pressure is formed on the inner diameter of the sleeve. In addition, the present invention relates to a method for regulating the amount of movement of the rotating body and the shaft in the axial direction and a backlash in a motor having a thrust plate that is disposed on the axial end face side of the sleeve and supports an axial load.

  In recent years, disk drives using motors have become smaller and have higher capacities, and this type of disk drive is particularly required to have impact resistance and low dust generation. Among them, there is a demand for further shock resistance and low dust generation for a spindle motor that is incorporated in a disk drive device and rotationally drives a recording disk.

   Conventionally, an HDD motor described in Japanese Patent Laid-Open No. 6-269142 (see Patent Document 1) is known. FIG. 9 shows the structure of a conventional motor. In FIG. 9, reference numeral 111 denotes a hub on which the disk 20 is mounted, and the hub 111 is made of an aluminum-based material.

  A shaft 112 made of martensitic stainless steel is attached to the center of the hub 111. The hub 111 rotates with the attached disk 20 to make its center of rotation. The shaft 112 is supported in the radial direction by a sleeve 121 made of a copper alloy, and is supported in the thrust direction by a thrust plate 122 made of martensitic stainless steel.

  A lubricating fluid such as oil or grease is filled between the shaft 112 and the sleeve 121 and between the shaft 112 and the thrust plate 122, respectively. (The number is not given because it is difficult to illustrate.) Also, the shaft 112 has a plurality of herringbone grooves 113 spaced apart in the axial direction, and lubricates by the herringbone grooves 113 when the shaft 112 rotates. Pressure is generated in the fluid, so that it can rotate in the radial direction without contact.

  The effect is the same even if the herringbone groove 113 is formed in the sleeve 121 in a plurality of positions spaced apart in the axial direction. The shaft end 114 has a pivot shape, and the axial position is determined by the thrust plate 122.

Thus, the shaft 112 can rotate in a non-contact manner between the shaft 112 and the sleeve 121 during rotation, and the shaft 112 and the thrust plate 122 can rotate in a low friction state.
A winding 125 is wound around the stator core 124 and then fixed to the bracket 123. The rotational driving force of the motor is generated by the rotating magnetic field generated by the stator core 124 and the multi-pole magnetized magnet 144 surrounding the rotating magnetic field.

  The magnet 144 is fixed to the inner periphery of the rotor frame 127 and constitutes the rotating body 110 as a whole and can rotate.

A retaining plate 129 made of aluminum, stainless steel, or copper is fixed to the bracket 123 to prevent the rotating body 110 from coming off.
A communication hole 128 is provided on the outer peripheral side 126 of the sleeve 121 so that air inside the sleeve 121 can escape when the shaft 112 is inserted into the sleeve 121.

    On the other hand, if external vibration is applied while the motor is rotating, the rotating body 110 on which the disk is mounted is displaced in the axial direction, and an error occurs during data writing or reproduction. Therefore, the magnet 144 is used to restrict displacement in the axial direction. The center of the stator and the center of the stator core 124 are shifted in the axial direction, thereby generating a magnetic attractive force acting between the magnet 144 and the stator core 124 to cope with the movement in the axial direction.

Further, since the motor does not function when the shaft 112 is detached from the sleeve 121 due to impact drop, posture difference or vibration, the motor is dealt with by a retaining plate 129.
JP-A-6-269142

 Recently, however, devices using this motor have been required to reduce noise. In addition, the capacity has been increased, and for this purpose, it is necessary to increase the number of disks.

  In the conventional example, the attractive force for restricting the movement of the rotating body in the axial direction is magnetically generated by the axial displacement between the center of the magnet and the center of the stator core. Due to the axial displacement, axial vibration is generated, which causes electromagnetic noise, which increases the noise of the motor.

  In addition, even if the attractive force is generated due to the axial displacement between the center of the magnet and the center of the stator core, the disk load weight increases due to the increase in the number of disks as the capacity increases, so that the rotating body is more effective than the magnetic attractive force As the disk load weight including the weight of the disk becomes heavier, the magnetic attractive force in the axial direction of the rotating body becomes smaller than the disk load weight and the rotating body moves when the motor is in the reverse posture state. And the rotary body moved and the contact between the retaining plate and the shaft end surface occurred. The contact causes generation of metal powder and generation of wear powder due to sliding wear during rotation, and there is a problem of entering into a narrow gap between the shaft and the sleeve.

  Recently, with the use of devices that use this motor as removable media and the spread of portable and portable notebook computers, it has become easier for the motor to be subject to shocks and drops. The number of cases in which the shaft moves in the axial direction is increasing. Even in such a state, wear powder and metal powder are not generated, and it is required to maintain the reliability of the apparatus.

  For this reason, when an impact or a drop is applied, the rotating body moves in the axial direction, and when this amount of movement increases, the disk directly attached to the hub of the rotating body moved in the axial direction and the head that accesses the disk surface ( In some cases, the apparatus becomes defective due to contact with a head arm that supports (not shown).

  Further, when the rotating body moves and comes into contact, metal powder due to contact between the retaining plate and the retaining end surface and wear powder due to sliding wear during rotation are generated.

  These wear powders and metal powders enter into a narrow gap between the sleeve and the shaft, causing seizure between the shaft and the sleeve, thereby shortening the bearing life. And the reliability of the apparatus has been remarkably impaired.

  Also, if the motor posture is reversed with the load disk attached, the magnetic attraction generated by the axial displacement between the center of the magnet and the center of the stator core will cause the disk load weight and the motor rotor to Inability to withstand its own weight, the rotating body moves in the axial direction, causing contact between the retaining plate and the retaining end surface, and the load increases and the motor load current increases, exceeding the product specifications. However, it has a drawback that it cannot be used for low consumption devices such as portable notebook computers that can be carried.

  In addition, when it is continuously rotated in the reverse posture, sliding wear occurs due to the contact between the retaining plate and the retaining end surface, and the life is shortened.

  The present invention prevents the occurrence of metal powder generated by contact between the retaining plate and the retaining end face and sliding wear during rotation even when an impact or drop is applied or the motor is in a reverse posture. An object is to provide a highly reliable motor.

 In order to solve the above-described problems, the present invention constitutes a suction plate made of a magnetic material attached on the surface of the bracket so as to face the end surface of the magnet. By providing the suction plate, the movement of the rotating body in the axial direction can be restricted by the action of a magnetic attractive force generated between the magnet end surface and the suction plate.

  In addition, in a motor provided with a retaining plate facing the retaining end face, the surface of the retaining plate is coated with a low friction resin. By coating the retaining plate with the low-friction resin, metal powder generated during contact between the retaining plate and the retaining end surface and sliding wear powder during rotation are suppressed.

  As described above, according to the present invention, there is a suction plate made of a magnetic material attached to the bracket so as to face the magnet end surface, and the suction plate has the same number of poles as the stator core. Since the magnet end face is magnetized in the same number as the inner circumference of the magnet, disturbances such as reverse rotation of the motor, vibration and dropping during rotation, etc. In addition, it is possible to suppress the axial movement of the rotating body on which the disk is mounted by the magnetic attraction force acting between the magnet end face and the attraction plate.

  In addition, it is possible to provide a highly reliable device with respect to the posture, impact, and dropping of the device without deteriorating the noise characteristics of the device.

  Also, by providing notches on the circumference of the suction plate that are equally spaced, the cogging that occurs between the stator core and the magnet and the cogging that occurs between the notch of the suction plate and the magnet cancel each other out. Therefore, the vibration component due to cogging can be reduced.

  The mechanism for restricting the amount of movement in the axial direction of a rotating body having a magnet, a rotor frame, and a hub is composed of a retaining end face of the sleeve and a retaining plate facing the retaining end face. Since the surface is coated with the low friction resin, the friction coefficient at the time of contact between the retaining plate and the retaining end surface can be reduced.

  Therefore, even if the retaining plate moves in the axial direction during a drop, impact, or reverse posture, even if the retaining plate contacts the retaining end surface of the sleeve, generation of sliding wear powder can be prevented. Therefore, an advantageous effect that the cleanliness of the apparatus can be maintained is obtained.

  In order to solve the above-described problems, the present invention has a suction plate made of a magnetic material attached to a bracket so as to face a magnet end face. The suction plate is provided with notches at equal intervals on a circumference having the same number as the number of poles of the stator core.

  The magnet end face is magnetized in the same number as the inner circumference of the magnet.

  By having the suction plate made of a magnetic material in this way, a magnetic attraction force is obtained between the magnet end surface and the suction plate, and the movement of the rotating body in the axial direction can be restricted.

  The present invention also provides a shaft, a sleeve in which the shaft is inserted and a herringbone groove for generating radial dynamic pressure is formed on the inner diameter, a bracket for fixing the sleeve, and an axial load disposed on the end face side of the sleeve. Thrust plate to be supported, hub fixed to the end face of the shaft, rotor frame attached to the hub, magnet attached to the rotor frame, armature facing the magnet and attached to the bracket, magnet, rotor In order to restrict the amount of movement of the rotating body having the frame and the hub in the axial direction, in a motor having a retaining end face of the sleeve and a retaining plate facing the retaining end face, the surface of the retaining plate is low. The friction resin is coated or the retaining plate itself is made of a low friction material.

  The low friction resin coated on the surface of the retaining plate is made of a fluorine material, and a binder material of 50 ± 15% by weight is mixed in the low friction resin.

  And it is good for the binder material itself to consist of polyimide resin which is excellent in sliding performance.

  And it is preferable when the coating thickness of low friction resin consists of 0.005-0.030 mm.

  Thus, the friction coefficient of the contact portion can be reduced by coating the retaining plate with the low friction resin.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 shows a cross-sectional view of a motor according to an embodiment of the present invention, and FIG. 2 shows a cross-sectional view of an assembly according to an embodiment of the present invention.

  1 and 2, a shaft 1 made of martensitic stainless steel is attached to the center of the hub 5. Then, the hub 5 rotates together with the attached disk 20 to form the center of rotation.

  The shaft 1 is supported in the radial direction by a sleeve 2 made of a copper alloy, and is supported in the thrust direction by a thrust plate 4 made of a ceramic material, martensitic stainless steel, or tool steel.

  The rotor frame 6 is fixed to the hub 5 by caulking or the like, and a magnet 7 is fixed to the inner peripheral side of the rotor frame 6. A plurality of magnetizations are made on the inner periphery of the magnet 7. The rotating body 14 includes a shaft 1, a hub 5, a rotor frame 6 and a magnet 7.

  Since the shaft 1, the sleeve 2 and the thrust plate 4 are made of a metal material and a ceramic material, the shaft 1 and the sleeve 2 have a mechanical rigidity sufficient to withstand the load of the disk 20 rotating at high speed. Moreover, the process which raises the outer diameter of the axis | shaft 1 and the inner diameter precision of the sleeve 4 is attained.

  The sleeve 2 is formed with a plurality of herringbone grooves 21 spaced apart in the axial direction, and the thrust plate 4 is fixed to the lower end side of the sleeve 2 via a reinforcing plate 23. Then, a lubricating fluid such as oil or grease is applied to the inner diameter portion of the sleeve 2 or the shaft 1, and the shaft 1 constituting the rotating body 14 is inserted into the sleeve.

By doing so, the clearance between the shaft 1 and the sleeve 2 and the clearance between the shaft 1 and the thrust plate 4 are filled with a lubricating fluid such as oil or grease, respectively. (Lubricating fluid is not given a number because it is difficult to show)
Therefore, even if the shaft 1 rotates, pressure is generated in the lubricating fluid by the herringbone groove 21 and the shaft 1 rotates in a non-contact manner in the radial direction. The effect is the same even if the herringbone groove 21 is formed on the shaft 1 in a plurality of distances in the axial direction.

  Since the shaft end 22 of the shaft 1 is a pivot bearing, the shape of the shaft end 22 is formed in a spherical shape, and the thrust plate 4 supports an axial load composed of a rotating body and a disk load. The thrust plate 4 is overlapped with the reinforcing plate 23 on the lower end side of the sleeve 2 and joined by a mechanical method such as caulking.

The outer diameter portion of the sleeve 2 has a retaining end face 9 whose diameter changes stepwise. The retaining plate 10 is firmly attached to the hub 5 so as to face the retaining end surface 9, thereby preventing the rotating body 14 from coming off in the axial direction.
By constructing and assembling in this way, the spindle assembly 25 supported by the sleeve 2 and the thrust plate 4 so as to be rotatable in a radial or thrust manner is completed.

  The armature 8 is fixed to the bracket 3 so as to face the magnet 7. The suction plate 11 made of a magnetic material is attached to the surface of the bracket 3 so as to face the end surface of the magnet 7. Thereafter, the motor is completed by fixing the inner peripheral portion of the bracket 3 of the bracket assembly 24 to which the armature 8 and the suction plate 11 are attached and the outer portion of the sleeve 2 of the spindle assembly 25. The rotational driving force of the motor is generated by the rotating magnetic field generated by the armature 8 wound around the stator core 17 and the multi-pole magnetized magnet 7 surrounding the periphery.

  Here, as shown in FIG. 3, a clearance L <b> 1 is provided between the retaining end surface 9 formed on the outer diameter portion of the sleeve 2 and the retaining plate 10 attached to face the retaining end surface 9. ing. The gap L1 is a moving amount in which the rotating body 14 moves in the axial direction due to an excessive impact or the like, and as a result, contact between the retaining plate 10 and the retaining end surface 9 occurs.

  However, since the retaining plate 10 is coated with a low-friction resin material or a low-friction resin, the friction coefficient between the retaining plate 10 and the retaining end surface 9 is low, and resin powder, metal powder and sliding generated at the time of contact are reduced. Generation of dynamic wear can be kept low. Note that the same effect can be obtained by coating the retaining end face 9 with a low friction material or a low friction resin.

(Embodiment 2)
FIG. 4 shows the shape of the suction plate, and FIGS. 5 and 6 show examples of the layout of the armature and the suction plate. 4, 5, and 6, notches 12 are provided on the inner circumference side of the suction plate 11 at equal intervals on the circumference. In FIG. 4, twelve notches 12 having the same number as the number of poles of the stator core 17 are configured at equal intervals. The suction plate 11 has a mechanical angle of 7.5 degrees at the notch 12 of the suction plate 11 with respect to the center of the slit 26 of the stator core 17 of the armature 8 (corresponding to 30 degrees because the electrical angle is an 8-pole magnet). The phase is shifted as much as possible.

  For this reason, as shown in FIG. 7, the cogging generated by the stator core 17 and the magnet 7 and the cogging generated by the notch 12 of the suction plate 11 and the magnet 7 are offset each other, so that the combined cogging is reduced. Of course, the effect can be expected even if the notch 12 is provided outside the suction plate 11.

  Further, since the cogging synthesized in the configuration as shown in FIG. 5 is reduced, the accuracy of the mounting angle of the suction plate 11 with respect to the slit 26 of the starter core 17 is not required.

  Further, if magnetizing the same magnetic pole as the magnetic pole magnetized on the inner diameter of the magnet 7 is applied to the end surface facing the attraction plate 11, the magnetic attraction force generated between the magnet end surface and the attraction plate 11 increases. The movement of the rotating body in the axial direction can be further restricted.

The present invention relates to a hydrodynamic bearing device used in a hard disk device and other rotating devices, in which a shaft is relatively rotatably inserted into a bearing hole of a sleeve, and a dynamic pressure generating groove is formed on at least one of the outer peripheral surface of the shaft and the inner peripheral surface of the sleeve At least one radial bearing surface is provided, and the sleeve is formed on a porous surface of a compacted metal sintered body material having a volume density of 85% or more on a porous surface of iron trioxide (Fe ₃ O) having a thickness of 2 to 10 micrometers. ₄ ) By forming a film, it is possible to obtain a hydrodynamic bearing device that is inexpensive, has no pressure leakage, and has a high performance and long life.

1 is a longitudinal sectional view of a motor according to Embodiment 1 of the present invention. The longitudinal cross-sectional view which shows the assembly of the motor by Example 1 of this invention Sectional drawing of the principal part of the motor by Example 1 of this invention Top view of suction plate according to embodiment 2 of the present invention Top view of suction plate and armature according to embodiment 2 of the present invention Top view of suction plate and armature according to embodiment 2 of the present invention The figure which shows the cogging characteristic by Example 2 of this invention The perspective view of the magnet by Example 2 of this invention Vertical section of a conventional motor

Explanation of symbols

1,112 shaft 2,121 sleeve 3,123 bracket 4,122 thrust plate 5,111 hub 6,127 rotor frame 7,144 magnet 8 armature 9 retaining end face 10,129 retaining plate 11 suction plate 12 notch 13 Clearance 14, 110 Rotating body 15 Magnet end surface 16 Rotor frame end surface 17, 124 Stator core 20 Disk 21 Herringbone groove 22 Shaft end 23 Reinforcement plate 24 Bracket assembly 25 Spindle assembly 26 Slit

Claims (4)

A shaft, a sleeve in which the shaft is inserted and a herringbone groove for generating radial dynamic pressure is formed on the inner diameter, a bracket for fixing the sleeve, and a thrust plate for supporting an axial load disposed on the end face side of the sleeve A hub fixed to the end surface of the shaft, a rotor frame attached to the hub, a magnet attached to the rotor frame, an armature facing the magnet and attached to the bracket, and the magnet In order to restrict the amount of movement of the rotating body having the rotor frame and the hub in the axial direction, the motor has a retaining end face of the sleeve and a retaining plate facing the retaining end face.
The retaining plate is made of a metal material, and the surface is coated with a low-friction resin made of a fluorine-based material, and the low-friction resin contains a binder material of 50 ± 15% by weight. Motor.   The motor according to claim 1, wherein the binder material is made of polyimide resin.   2. The motor according to claim 1, wherein the coating thickness of the low friction resin is 0.005 to 0.030 mm. The motor according to claim 1, wherein the low friction material comprises a polyimide resin and a low friction resin.

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