JPH0729293A - Spindle motor - Google Patents

Abstract

PURPOSE:To provide the spindle motor which prevents the disadvantage that hubs holding a recording disk are thermally deformed by a difference in the coefft. of thermal expansion between the hubs and rotor yokes to cause a change in the spacing between the disk and a head acting on the disk and which does not destroy the adhesive joint between previously adhered and joined bearings and a bearing holding surface at the time of fitting sealing means. CONSTITUTION:Rotor yokes 28, 72 of spindle motors 20, 70 integrally have parts holding the bearings 52, 74, parts held by the hubs 26, 76 and parts 48, 72 holding rotor magnets 56, 80. Yoke parts 48, 72 holding the rotor magnets 56, 80 of the rotor yokes 28, 72 have a prescribed spacing d between the hubs 26 and 76 arranged on the outer side thereof and members 26, 72 supported by the bearings 40, 74 parted further upward from a fixing member 22 have a hollow circumferential groove 42 slightly above the bearing supporting surface 38.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor for mounting and rotating a plurality of recording disks such as optical and magnetic disks.

[0002]

2. Description of the Related Art In a conventionally known spindle motor 1 of the type shown in FIG. 3, for example, a fixed shaft 3 fixed to a fixed member 2 composed of a base or a bracket, and the fixed shaft 3 are provided. And a hub 7 rotatably supported via a first bearing 4, a second bearing 5, and a bush 6 which are fixed to the hub 7. Here, the bush 6 is usually made of an iron material for strengthening the magnetic field, while the hub 7 is generally made of a material mainly made of aluminum for ease of processing. Further, the hub 7 is integrally provided at its lower portion with a flange portion 8 extending outward in the radial direction. The flange portion 8 has a function of receiving a recording disk (not shown). Further, the bearings 4 and 5 are usually fixed to the fixed shaft 3, the hub 7 and the bush 6 by an adhesive. Similarly, the bush 6 is fixed to the inner peripheral surface of the hub 7 in a liquid-tight state by a known means such as an adhesive. A stator 9 is fixed to the shaft 3 at a predetermined position between the first bearing 4 and the second bearing 5. Furthermore, a cylindrical rotor yoke 10 is similarly fixed to the inner peripheral surface of the hub 7 by means known per se, and a rotor magnet 11 known per se is also known inside the rotor yoke 10. It is fixed by means. Here, like the bush 6, the rotor yoke 10 is generally made of an iron material in order to strengthen the magnetic field and prevent the emission of magnetic force lines. Further, sealing means 12 and 13 for preventing dust (bearing grease or the like) in the motor from leaking out of the motor are axially outward of the both bearings 4 and 5, respectively.
And between the fixed shaft 3 and the bush 6.

[0003]

In this way, the bush 6 is attached to the inner peripheral surface of the hub 7, and the inner surface of the bush 6 receives the outer ring portion of the second bearing 5 and also the outer ring of the ring-shaped magnetic fluid seal 13. The conventional spindle motor 1 that receives the other portion has the following problems.

One of them is that when the motor 1 is continuously rotated for a long time and the temperature of the motor 1 rises, the hub 7 made of an aluminum material or the like is replaced by an iron material or the like due to the difference in coefficient of thermal expansion. Is subject to more thermal deformation than the rotor yoke 10 made of. Therefore, the hub 7 is thermally deformed so as to project around the mounting portion of the rotor yoke 10, and as a result, the upper portion of the hub 7 approaches the fixed shaft 3. Therefore, the position of the recording disk stacked on the flange portion 8 of the hub 7 varies, and there is a problem that the distance between the recording disk and the head acting on the recording disk cannot be kept constant.

Another problem is that when mounting the motor,
When the first bearing 4 is fixed to the fixed shaft 3 and the hub 7 with an adhesive and then the sealing means 12 is pressed and fitted into the inner peripheral surface of the upper portion of the hub 7 at a position above the first bearing 4. In addition, the sealing means 12 temporarily expands the gap between the fixed shaft 3 and the hub 7. As a result, there is a problem that the adhesive agent that fixes the first bearing 4 between the fixed shaft 3 and the hub 7 is forcibly peeled off. The present invention aims to solve these problems.

[0006]

The present invention has the following means in order to solve the above problems. In order to solve the first problem, a new rotor yoke in which a bush and a rotor yoke are integrally formed is configured, and the hub is contacted and held only at a portion corresponding to the bush portion so far. The portion corresponding to the rotor yoke portion of the above was arranged at a constant distance from the inner surface of the hub over substantially the entire length thereof. Also, in order to solve the second problem,
An annular groove was formed between the portion of the hub supporting the first bearing and the portion receiving the sealing means.

[0007]

In the new rotor yoke in which the bush and the rotor yoke are integrally formed, only the portion corresponding to the bush portion comes into contact with and holds the hub and supports the second bearing, while the rotor yoke portion so far. Since the portion corresponding to (1) is arranged at a constant distance from the inner surface of the hub, the portion corresponding to the rotor yoke portion is not in contact with the hub, and therefore the hub due to the difference in the coefficient of thermal expansion depending on the material is used. In the thermal deformation, the curved deformation in the fixed shaft direction does not substantially occur, and only the linear deformation in the direction parallel to the axial direction of the fixed shaft occurs. Therefore, even if thermal deformation occurs in the hub and rotor yoke, the upper portion of the hub does not approach in the direction of the fixed shaft, and therefore the position of the recording disk laminated on the flange portion of the hub always acts on it. It is possible to maintain a constant space between the head and the head.

Further, since the annular groove is formed between the portion of the hub supporting the first bearing and the portion of the hub in which the sealing means is to be received, the sealing means should be press-fitted to the inner peripheral surface of the hub. In this case, the radial expansion deformation of the sealing means with respect to the hub is substantially absorbed by the annular groove provided in the hub. For this reason, no change occurs in the positional relationship between the hub and the first bearing due to the radial expansion deformation of the sealing means with respect to the hub, and therefore the first bearing is fixed between the fixed shaft and the hub. The forced removal of the adhesive is completely eliminated.

[0009]

1 shows an embodiment of the present invention, a spindle motor 20 of the present invention comprises a fixing member 22 composed of a base or a bracket, a fixing shaft 24 fixed to the fixing member 22, A hub 26 is rotatably attached to the fixed shaft 24, and a rotor yoke 28 is rotatably attached to the fixed shaft 24 so as to rotate with the hub.

The hub 26 is generally made of a material whose main material is aluminum for ease of processing, and has a thick annular portion 30 in an upper portion and a recording disk (not shown) in a lower portion. It has integrally a thick annular portion 32 having a receiving function and a cylindrical portion 34 connecting both annular portions. Further, the upper annular portion 30 is integrally provided with a rising portion 36 extending upward therefrom. Further, the inner surface in the radial direction of the upper annular portion 30 forms a substantially vertical surface 38, and the outer surface of the first bearing 40 in which the inner ring is fixed to the fixed shaft 24 by an adhesive agent is the same as the vertical surface 38. It is fixed by adhesive or the like. Further, an annular groove 42 is formed on the vertical surface 38 above the portion where the first bearing 40 is fixed. The groove 42 has a predetermined depth, and acts so that when the rising portion 36 is pressed radially outward, the groove substantially absorbs the outward deformation of the rising portion 36. ing.

On the other hand, the rotor yoke 28 is formed of a material which is usually made of iron as a main raw material for strengthening the magnetic field and preventing the emission of magnetic force lines, and has an outer edge portion 44 which abuts the lower thick portion 32 of the hub 26. , An inner edge portion 46 extending in the axial direction substantially parallel to the outer edge portion 44, a holder portion 45 including the inner edge portion 46 and the inner edge portion 46 along the inner surface of the cylindrical portion 34 of the hub 26. A yoke portion 48 extending from the holder portion 45 to the upper side of the rotor yoke so as to have a space d, and a flange portion 50 protruding downward and radially inward from the inner edge portion 46 are integrally provided. The inner ring portion 46 has an inner ring fixed to the fixed shaft 24 with an adhesive or the like, and the outer ring of the second bearing 52 is similarly fixed with an adhesive or the like, and the flange portion 50 has the bearing 5
2 is held from the lower side. The free end of the flange 50 cooperates with the fixing member 22 to form a labyrinth seal.

In the embodiment, a small diameter portion 47 is provided at the open end of the cylindrical portion 34 of the hub 26, and the inner diameter of the small diameter portion 47 is somewhat smaller than the inner diameters of the other portions.
With this structure, the rotor yoke 28 is attached to the hub 26.
When mounted on the rotor yoke 28, the yoke portion 48 of the rotor yoke 28 is guided by the small diameter portion 47.
8 are mounted substantially parallel to the axial direction of the hub 26 (vertical direction in FIG. 1). The small diameter portion 47 mainly acts as a guide for the yoke portion 48, and the rotor yoke 28 and the hub 26 are firmly coupled by the outer peripheral surface of the outer edge portion 44 and the inner peripheral surface of the annular portion 32. When the rotor yoke 28 can be mounted as required, the small diameter portion 4
7 can be omitted.

A stator 54 is fixed to the fixed shaft 24 at a predetermined position between the first bearing 40 and the second bearing 52. Furthermore, the yoke portion 4 of the rotor yoke 28 is
A cylindrical rotor magnet 56 is similarly fixed to the inner peripheral surface of the rotor 8 by known means. Further, the first bearing 40
The impurities in the motor (bearings 40, 52
Sealing means 58 is provided to prevent fine particles (such as grease used in the above) from leaking out of the motor. The sealing means 58 has a magnetic fluid holding means 59 composed of a ring-shaped permanent magnet 55 and a pair of pole pieces 57 arranged on both sides of the magnet 55, and the magnetic fluid holding means 59 serves as the rising portion 36 of the hub 26. It is mounted so as to be pushed into the inner peripheral surface of the groove, and is located slightly above the groove 42 in the mounted state. Then, a magnetic fluid (not shown) is injected between the free end portion of the magnetic fluid holding means 59 and the fixed shaft 24. A scattering prevention cover 61 is arranged outside the magnetic fluid holding means 59, and this cover 61 is also attached to the inner peripheral surface of the rising portion 36. Meanwhile, the second
Outside the axial direction of the bearing 52, the flange portion 50 of the rotor yoke 28 and the fixing member 22 provide a labyrinth seal to prevent impurities in the motor from leaking out of the motor through the labyrinth seal.

In the present invention, the outer edge portion 44 of the rotor yoke 28 may be arranged to be substantially flush with the outer surface of the yoke portion 48. In this case hub 2
6 to lower the inner surface of the cylindrical portion 34 to the fixing member 22 linearly, and to provide the outer edge portion 44 of the rotor yoke 28 and the inner surface of the cylindrical portion 34 of the hub 26 with a positioning portion such as a flange for positioning. Is preferred. This is because they can be easily positioned.

According to the present invention, the rotor yoke 28 integrally has the bushing portion of the prior art device shown in FIG. 3, and the cylindrical portion 34 of the hub 26 is the rotor yoke 2.
The yoke 26 and the rotor yoke 28 are arranged at a predetermined distance so as not to substantially contact the yoke portion 48 and the hub 26 and the rotor yoke 28 are fixedly held only at one portion thereof, so that thermal deformation due to a difference in thermal expansion coefficient between the two is caused. Can be completely absorbed. Further, since the yoke portion 48 is not coupled to the inner peripheral surface of the cylindrical portion 34 of the hub 26, the coupling region between the outer edge portion 44 of the rotor yoke 28 and the hub 26 can be made relatively large, and accordingly, the holder portion can be formed. The meat pressure of 45 can also be thickened. Further, even when the hub 26 is pressed outward in the radial direction when the sealing means 58 is fitted to the inner peripheral surface of the hub 26, the groove 42 is slightly biased outward in the radial direction only in the rising portion 36, and the pressing force is applied. Absorbs substantially all of the
There is no change in the positional relationship between and.

FIG. 2 shows another embodiment of the present invention. The spindle motor 70 of this embodiment is different from the spindle motor 20 of FIG. 1 in that a rotor yoke 72 made of an iron material as a main material is held by a first bearing 74, and a hub 76 made of an aluminum material as a main material is a second bearing. 7
It is configured to be held by eight. Note that the rotor magnet 8 is formed on the inner surface of the rotor yoke 72.
0 is fixed, and the outer surface of the rotor yoke 72 and the hub 7 are fixed.
A predetermined gap d is provided between the inner surface of 6 and the inner surface of 6. It is obvious to those skilled in the art that even with such a configuration, it is possible to obtain the same effect as in the case of FIG.

Although the specific examples of the spindle motor according to the present invention have been described above, the present invention is not limited to these specific examples, and various modifications and corrections can be made without departing from the scope of the present invention. .

For example, in the illustrated embodiment, the groove 42
Although a seal mechanism using magnetic fluid is adopted as the seal means 58 related to the above, a labyrinth seal mechanism may be adopted instead. In such a case, the groove 42 substantially absorbs the deformation that occurs when the labyrinth member forming the labyrinth seal is mounted, and the same effect as described above is achieved.

[0019]

As the spindle motor is continuously rotated for a long period of time, when the temperature of the motor rises, the hub made of aluminum material or the like is more likely than the rotor yoke made of iron material or the like because of the difference in thermal expansion coefficient. Although it undergoes a lot of thermal deformation, according to the configuration of the present invention, since the axially extending portions of the hub and the rotor yoke are arranged with a predetermined gap therebetween, both are free to undergo thermal deformation, and as in the past. In addition, the hub does not cause thermal deformation such that the hub projects around the mounting portion of the rotor yoke. as a result,
Also, the upper part of the hub does not approach in the direction of the fixed shaft. Therefore, the position of the recording disk stacked on the thick portion of the hub does not fluctuate, and the recording disk and the head acting on the recording disk always maintain the best contact state.

Further, at the time of assembling the motor, after fixing the first bearing to the fixed shaft and the hub with an adhesive,
At the upper position of the first bearing, when the sealing means is pushed and fitted into the upper portion of the hub, the sealing means temporarily expands the inner peripheral surface of the hub radially outward. The expansion deformation is absorbed almost completely by the groove,
As a result, the adhesive that fixes the first bearing 4 between the fixed shaft and the hub is prevented from being peeled off.

[Brief description of drawings]

FIG. 1 is a sectional view of a spindle motor showing a first embodiment of the present invention.

FIG. 2 is a sectional view of a spindle motor showing a second embodiment of the present invention.

FIG. 3 is a diagram showing a cross-sectional view of a known spindle motor.

[Explanation of symbols]

 20 spindle motor 22 fixed member 24 fixed shaft 26 hub 28 rotor yoke 30, 32 thick portion 34 cylindrical portion 36 rising portion 38 vertical surface 40 first bearing 42 groove 44 outer edge portion 46 inner edge portion 48 yoke portion 50 flange portion 52 second portion Bearing 54 Stator 56 Rotor magnet 58 Sealing means 60 Seal receiving groove 70 Spindle motor 72 Rotor yoke 74 First bearing 76 Hub 78 Second bearing 80 Rotor magnet

Claims (2)

[Claims] 1. A fixed member 22, a fixed shaft 24 fixed to the fixed member 22, and a hub rotatably attached to the fixed shaft 24 via a bearing for supporting a recording disk. Hub 2 having 32
6, 76, rotor yokes 28, 72 rotatably attached to the fixed shaft 24 via another bearing and arranged radially inside the hub, and the hub 2.
The bearing holding 6, 76 and the bearing holding the rotor yoke have a constant space in the axial direction of the fixed shaft, and the shaft 2 is located within the space.
4, a stator 54 fixed to the rotor 4, and rotor magnets 56 and 80 fixed to the inner surface of the rotor yoke 28 at a position opposed to the stator 54.
In a spindle motor 20, 70, wherein a member supported by a bearing far away from the fixed member 22 has a sealing means 58 for sealing between the member and the fixed shaft, the rotor yoke 28 , 72 integrally have a portion holding the bearing, a portion held by the hubs 26, 76, and a portion holding the rotor magnet,
Also, a yoke portion 48 for holding the rotor magnet of the rotor yoke is arranged outside the hubs 26, 76.
A spindle motor having a predetermined distance d over substantially the entire length between and. 2. The spindle according to claim 1, wherein the member supported by the bearing far away from the fixed member 22 has a concave circumferential groove 42 slightly above the bearing support surface. motor.