JPH11308801A - Spindle motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent separation of the bonding part of the hub and a holder welded to the hub which constitute a spindle motor made of different kinds of metals, the deterioration of sealing performance, the separation of a magnetic fluid sealing device, etc., when a temperature difference is produced between the hub and the holder by a difference in thermal expansion coefficient. SOLUTION: Material, whose thermal expansion coefficient is smaller than the thermal expansion coefficient of material of which a holder means 22 is made, is provided between the holder means 22 and a hub 21. With this constitution, when a temperature difference is produced between the holder means 22 and the hub 21, the deformation caused by a thermal stress applied to the welding part of the holder means 22 and the hub 21 is forcibly limited, so that the separation of the welding part of the holder means 22 and the hub 21 can be avoided, the sealing characteristics can be protected from deterioration and the separation of a magnetic fluid sealing device can be avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording disk drive for rotating a disk-shaped recording disk such as a hard disk by means of a spindle motor, and more particularly, lubricant or the like leaks from between a rotating portion and a stationary portion of the spindle motor. The present invention relates to a sealing device having a novel structure for preventing such a situation.

[0002]

2. Description of the Related Art Various types of spindle motors are currently known. For example, in a spindle motor 1 as shown in FIG. 4, a shaft 4 is fixedly held at a substantially central portion and a stator 3 is fixedly held at a peripheral position of the shaft 2. A pair of bearings 5 spaced apart in the axial direction of the shaft
And a substantially cylindrical rotor hub 8 having a disk receiving portion 7 which is fixedly held at a position opposed to the stator 3 and which supports a hard disk on an outer peripheral portion thereof. Also known is a spindle motor 1 of the type described in Japanese Patent Application Laid-Open No. 7-312.
No. 841).

In the spindle motor 1 having such a configuration, the disk held by the disk receiving portion 7 is
Bearings 5, 5, which are arranged in the disk accommodation space and rotatably support the rotor hub 8, are provided in the disk accommodation space.
Grease and contaminated air inside the motor may flow in. This implies a risk of causing disk contamination. Therefore, in many spindle motors, grease from the bearings 5 and 5 and contaminated air inside the motor do not flow into the disk storage space.
Generally, a sealing device 9 for closing the space between the rotor hub 8 and the shaft 2 is used.

[0004] As the sealing device 9, a magnetic fluid sealing device is widely used. This magnetic fluid sealing device 9
As shown in FIG. 5, is constituted by an annular holder 11 fixed to the inner peripheral surface of the rotor hub 8 with an adhesive 10 and an annular seal portion 12 fixed to the holder 11. . The seal portion 12 generally includes a spacer 13 made of a permanent magnet, a pair of magnetic plates 14 disposed on both surfaces of the spacer 13 to form a pole plate, and a gap between the magnetic plate 14 and the shaft 2. , And a ring-shaped protective cap 16 (FIG. 4).

Further, a magnetic fluid sealing device 9A having a configuration as shown in FIG. 6 is also known (Japanese Patent Laid-Open No. Hei 6-253).
488). The magnetic fluid sealing device 9A includes an annular holder 11A fixed to the inner peripheral surface of the rotor hub 8A with an adhesive 10A, and a seal portion 12A fixed to the holder 11A. This seal portion 12A is generally provided with a spacer 1 made of a permanent magnet.
3A, a pair of magnetic plates 14A arranged on both surfaces of the spacer 13A and constituting a magnetic pole plate, and a known magnetic fluid 15A arranged in a space between the magnetic plate 14A and the shaft 2A. , A ring-shaped protective cap 16A. The holder 11A has the lower end of the protruding wall 11c extending downward positioned on the step 8a of the rotor hub 8A, and is fixed by an adhesive 10A. In this state, a labyrinth gap 18 is formed between the upper surface of the outer ring of the bearing 5A and the lower surface of the annular holder 11A. In the spindle motor provided with the magnetic fluid sealing device 9A, when the motor rotates, the lubricant leaking through a slight gap in a portion where the shield plate 19 is fitted to the outer ring of the bearing 5A due to centrifugal force is generated. Succeeded in preventing intrusion into.

[0006]

However, in these magnetic fluid sealing devices 9 and 9A, the holders 11 and 11A of the sealing device are usually made of a non-magnetic material such as aluminum. this is,
Permanent magnets 13 and 13A as spacers constituting the seal portions 12 and 12A, and a pair of magnetic pole plates 14 and 14; 1
4A, 14A, shafts 2, 2A, magnetic fluid 15,
15A to secure a closed magnetic circuit.
On the other hand, the magnetic pole plates 14, 14; 14A, 14A and the rotor hubs 8, 8, forming the magnetic fluid sealing devices 9, 9A.
For A, magnetic stainless steel is widely used in view of rust prevention characteristics. However, when the magnetic fluid sealing devices 9 and 9A are fixed to the rotor hubs 8 and 8A made of a magnetic material with an adhesive as described above, the magnetic rotor hubs 8 and 8A and a non-adhesive and fixed to them are fixed. Since the metal characteristics are different between the magnetic material holders 11 and 11A, for example, when the fluid sealing devices 9 and 9A operate to cause a temperature change in these members, the rotor hubs 8 and 8A are turned on.
Due to the difference in the coefficient of thermal expansion between the stainless steel forming A and the aluminum material forming the holders 11 and 11A, the adhesive fixing portion easily peels off,
There is a problem that the sealing characteristics are easily deteriorated or, in the worst case, the magnetic fluid sealing devices 9 and 9A are detached.

[0007]

According to the present invention, there is provided a magnetic fluid sealing device fixed to a hub, wherein the magnetic fluid sealing device comprises a holder means and a sealing means. And holder means 22
Is fixed to the hub 21 and the sealing means 23 is
2 by interposing a material having a smaller coefficient of thermal expansion than the material constituting the holder means 22 in the holder means 22, the holder means 22 and the hub 21 When a temperature difference is generated between the holder 21 and the hub 21, deformation of the joint between the holder means 22 and the hub 21 due to thermal stress is limited.

More specifically, the holder means 22 comprises a first holder 25 holding the sealing means 23 and a second holder 26 holding the first holder 25,
The holder 26 is made of a material having a smaller coefficient of thermal expansion than that of the material forming the first holder 25, and at least the second holder 26 is arranged in a fixed relationship to the hub 21. is there.

Further, the holder means 52 embeds and mounts an embedded material (63 and / or 64) having a lower coefficient of thermal expansion than that of the material forming the holder 52. Further, the holder means 52 is provided with a first flat portion 54.
, A second flat portion 56, and a hanging portion 55 connecting the both.
And an embedded material (63) is provided on at least one of the upper surface of the first flat portion 54 and the lower surface of the second flat portion 56.
And / or 64).

[0010] Furthermore, an attachment (83 and / or 84) having a coefficient of thermal expansion smaller than the coefficient of thermal expansion of the material forming the holder 72 is attached to the holder means 72. .

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. In the following embodiment, a spindle motor in which the shaft does not rotate will be described as an example. However, as will be apparent to those skilled in the art, the present invention can be similarly used in a spindle motor in which the shaft rotates. . FIG. 1 shows a magnetic fluid sealing device 20 according to the present invention.
The magnetic fluid seal device 20 includes an annular holder 22 fixed to the inner peripheral surface of the rotor hub 21 and an annular seal 23 fixed to the holder 22. The holder means 22 is preferably an annular first holder 25 made of substantially the same form and material (for example, a non-magnetic material such as aluminum) as the holder 11 shown in FIG. And an annular second holder 26. The sealing means 23 includes the sealing portions 12 and 1 shown in FIG. 5 or FIG.
As in the case of 2A, generally, an annular spacer 30 made of a permanent magnet and a pair of annular magnetic plates 31 and 32 disposed on both surfaces of the spacer 30 and constituting a pole plate.
A known magnetic fluid 34, 35 disposed in a space between the magnetic plates 31, 32 and the shaft 33, and a ring-shaped protective cap similar to that shown in FIG. 4 or FIG.
It is composed of This magnetic fluid sealing means 23
A permanent magnet 30 as a spacer and a pole plate 31 (3
2), shaft 33, magnetic fluid 34 (35), shaft 33, magnetic fluid 35 (34), and magnetic pole plate 32 (31)
A grease from a bearing (not shown) that rotatably supports the rotor hub 21 and contaminated air inside the motor flow into the disk housing space holding the disk. The space between the rotor hub 21 and the shaft 33 is closed so as not to occur.

That is, the first holder 25 has a first flat portion 36 which spreads substantially annularly and flatly, a hanging portion 37 which extends slightly downward from the first flat portion 36, and a hanging portion 37 which extends again from the hanging portion 37. The second flat portion 38 is formed integrally with the second flat portion 38 which extends annularly and flatly. The central portion of the first flat portion 36 is a space, through which the shaft 33 passes. Further, a circular enlarged portion 40 is formed radially outward in a lower portion of the side surface 39 forming the central space of the first flat portion 36. The outer diameter portion of the sealing means 23 including the spacer 30 and the magnetic plates 31 and 32 is attached to the first fixing means 4 such as an adhesive.
It is fixed by 1. Further, the lower surface of the magnetic plate 32 and the first holder 25 are joined to each other by a second fixing means 42 such as another adhesive. Preferably, the outer peripheral side surface of the second flat portion 38 of the first holder 25 is similarly fixed to the inner peripheral surface of the rotor hub 21 by third fixing means 43 such as an adhesive.

The second holder 26 is made of a material similar to that of the first holder 25, for example, a non-magnetic material such as aluminum, or a material constituting the rotor hub 21, for example, stainless steel, or a material having a thermal expansion coefficient of those materials. A material having an intermediate coefficient of thermal expansion, such as copper or brass, or other copper alloys, more generally has a higher coefficient of thermal expansion than the material of the first holder 25 (eg, aluminum) than the material of the rotor hub 21 (eg, stainless steel). Any material that is close (or has a thermal expansion coefficient closer to the material of the rotor hub than the material of the first holder 25) may be used.

As shown in FIG. 1, the second holder 26 has an inner peripheral portion in contact with an outer peripheral portion of the hanging portion 37 of the first holder 25 and a first holder 2 so that the cross section is substantially L-shaped.
5, a flat extension 44 extending radially outwardly flat along the second flat portion 38, and a vertical extension extending upward from the flat extension 44 along the inner peripheral surface of the rotor hub 21. And a unit 45. Here, it is preferable that the vertical extension portion 45 of the second holder 26 is formed so that the dimension thereof is at least larger than the thickness dimension of the lower flat portion 38 of the first holder 25. The lower surface of the flat extension portion 44 and the second flat portion 38 of the first holder 25 are
They are joined together by fourth fixing means 46 such as an adhesive. The outer peripheral side surface of the vertical extension portion 45 is fixed to the inner peripheral surface of the rotor hub 21 by fifth fixing means 47 such as an adhesive.

It should be noted here that the second holder 26 is joined to both the first holder 25 and the rotor hub 21. When the holder means 22 is joined to the rotor hub 21, if necessary, the third fixing means 43 joining the first holder 25 and the rotor hub 21 can be omitted. Holder 2
Fixing means 46 and the second holder 2 joining
Fifth fixing means 47 for joining rotor 6 and rotor hub 21
Is essential. However, the first
Outer peripheral surface of second flat portion 38 of holder 25 and second holder 26
Can be formed substantially the same vertical surface as the outer peripheral surface of the vertical extension portion 45, and it is more preferable that both are fixed to the inner peripheral surface of the rotor hub 21 at the same time.

In the embodiment shown in FIG. 1 having such a configuration, the second holder 26 is used in addition to the first holder 25 so far.
To the second holder 26, and further, the first and second
The holder can be joined to the rotor hub 21 at the same time. As a result, it is possible to increase the bonding area between the holder means 22 and the rotor hub 21 and effectively achieve heat transfer, thereby minimizing thermal deformation due to a thermal expansion error between the holder means and the rotor hub. Further, when the holder means 22 of the magnetic fluid sealing device 20 and the rotor hub 21 are joined, the first holder 25 and the second holder 26 are joined, and then the second holder 26 and the rotor hub 21 are joined. The heat capacity of the holder means and the rotor hub can be minimized by increasing the heat capacity of the holder means.
Therefore, when a temperature change occurs in these members,
The difference in the thermal expansion coefficients of these members prevents the adhesive fixing portion from easily peeling off, and prevents the sealing characteristics from being easily impaired and the magnetic fluid seal device 20 from being detached. You can do it.

FIG. 2 illustrates a second embodiment of the present invention. The difference between the sealing device 50 shown in FIG. 2 and the sealing device 20 shown in FIG.
Instead of the second holder 26, the first holder is provided with an embedded material formed of substantially the same material as the material forming the second holder. That is, in the magnetic fluid sealing device 50 shown in FIG.
An annular holder 52 is fixed to the inner peripheral surface of the holder 52, and a seal 53 is fixed to the holder 52. The holder means 52 is preferably made of a non-magnetic material such as aluminum having the same material as that of the first holder 25 shown in FIG. The sealing means 53 has substantially the same configuration and operation as the sealing means 23 shown in FIG. The rotor hub 51 is made of, for example, stainless steel as in FIG.

In the sealing device 50 shown in FIG. 2, the holder means 52 includes a first flat portion 54 extending substantially annularly and flat, a hanging portion 55 extending slightly downward from the first flat portion 54, The second flat portion 56 is formed integrally with the second flat portion 56 which is again annularly and flatly spread from the hanging portion 55. The central part of the first flat part 54 is a space part, through which the shaft 57 penetrates. Further, the first flat portion 54
A circular enlarged portion 58 is formed radially outward in a lower portion of the inner side surface that forms the space. The sealing means 53 is fixed to the enlarged diameter portion 58 by first fixing means 59 such as an adhesive. Further FIG.
Similarly to the embodiment, the lower surface of the sealing means 53 and the holder means 52 are connected to each other by a second fixing means 60 such as another adhesive. Second flat portion 56 of holder means 52
Is fixed to the inner peripheral surface of the rotor hub 51 by third and fourth fixing means 61 and 62 such as an adhesive.

In the holder means 52 of the magnetic fluid sealing device 50 shown in FIG. 2, the upper surface of the first flat portion 54 and the lower surface of the second flat portion 56 are each provided with an annular filling 6.
3, 64 are embedded. Preferably, these embedded materials 63 and 64 are both made of the same material as the holder means 52, for example, a non-magnetic material such as aluminum or the material constituting the rotor hub 51, for example, stainless steel.
Or made of a material having a coefficient of thermal expansion intermediate between those of the materials, such as copper, brass, or other copper alloys, and more generally having a coefficient of thermal expansion greater than that of the material of the holder means 52 (eg, aluminum). Rotor hub 51
(For example, a material having a thermal expansion coefficient closer to that of the rotor hub than the material of the holder means 52).

The embedded members 63 and 64 are arranged so as to be located as far away from the sealing means 53 as possible so as not to affect the sealing means 53 even when they are made of a magnetic material. I have.

In the second embodiment (FIG. 2) having such a structure, the holders 52 made of aluminum having a relatively high coefficient of thermal expansion are embedded in the holders 52, 63 and 64 having a relatively low coefficient of thermal expansion. Is embedded. Therefore, even when a temperature change occurs between the rotor hub 51 and the holder means 52, expansion of the holder means 52 made of aluminum or the like due to thermal deformation is prevented by the embedded material 6.
3, 64 thwart and prevent the expansion. As a result, the amount of thermal deformation applied to the rotor hub 51 by the holder means 52 due to thermal expansion is significantly reduced. Thereby, due to the difference in the coefficient of thermal expansion of these members, it is possible to prevent the adhesive fixing portion of both members from easily peeling off due to the generated thermal deformation, and the sealing characteristics are easily impaired,
It is possible to reliably prevent the magnetic fluid seal device 20 from being detached.

FIG. 3 illustrates a third embodiment of the present invention. The difference between the sealing device 70 shown in FIG. 3 and the sealing device 50 shown in FIG. 2 is that the sealing device 50 shown in FIG.
Instead of embedding the embedded material in the holder means 52, an adhesive made of the same material as the embedded material is attached to the holder means. That is, the magnetic fluid sealing device 70 shown in FIG. 3 includes an annular holder 72 fixed to the inner peripheral surface of the rotor hub 71 and a seal 73 fixed to the holder 72.
The holder means 72 is preferably made of a non-magnetic material such as aluminum having the same material as that of the holder means 52 shown in FIG. 2, and has a first flat portion 74 similar to the holder means 52 shown in FIG. And the hanging part 75 and the second
It is formed integrally with the flat portion 76. The center of the first flat portion 74 is a space, through which the shaft 77 passes. Further, a circular enlarged portion 78 is formed radially outward in a lower portion of the inner side surface forming the space of the first flat portion 74.
The sealing means 73 is provided with a first fixing means 7 such as an adhesive.
9. Further, the lower surface of the sealing means 73 and the holder means 72 are separated from the second fixing means 80 such as an adhesive.
Are connected to each other. Similarly, the outer peripheral side surface of the second flat portion 76 and the outer peripheral portion of the upper surface of the second flat portion 76 of the holder means 72 are third and fourth fixing means 81, 82 such as an adhesive.
Thus, the rotor hub 71 is fixed to the inner peripheral surface.

In the holder means 72 of the magnetic fluid sealing device 70 shown in FIG. 3, the upper surface of the first flat portion 74 and the upper surface of the second flat portion 76 are respectively provided with annular attachments 83,
Reference numeral 84 is attached by fixing means such as an adhesive. Preferably, these patches 83, 84 both have substantially the same material as the implants 63, 64 described with respect to FIG. Even when these stickers 83 and 84 are made of a magnetic material, care is taken to arrange them as far as possible from the sealing means 73 so as not to affect the sealing means 73. In the apparatus shown in FIG. 3, the adhered object 8 is compared with the apparatus shown in FIG.
The mounting of the holders 3 and 84 is easy, and there is no need to machine the annular space for filling the embedded object in the holder means 72.

In the third embodiment (FIG. 3) having such a configuration, the attachments 83 and 84 having a relatively low coefficient of thermal expansion are attached to the holder means 72 made of aluminum having a relatively high coefficient of thermal expansion. doing. For this reason, the rotor hub 7
1 and the holder means 72, when the temperature changes, the holder means 7 made of aluminum or the like can be used.
The bonded articles 83 and 84 prevent the thermal deformation of No. 2 in advance. As a result, the holder means 72 is thermally expanded and the rotor hub 7
The amount of thermal deformation given to 1 is significantly reduced. As a result, it is possible to prevent the adhesive fixing portion of the members from easily peeling off due to the thermal deformation caused by the difference in the thermal expansion coefficients of these members, easily deteriorating the sealing characteristics, or easily reducing the magnetic fluid seal. It is possible to reliably prevent the device 70 from being detached.

In the present invention, in the embodiment shown in FIG. 1, the first flat portion 36 and / or the second flat portion 38 of the first holder 25 are embedded in the first holder 25 as shown in FIG. 2 or FIG. (63/64) or at least one attachment (83/84). Further, in the embodiment shown in FIG. 2, the number of the embedded objects (63/64) is reduced to one, or the adhesive object (83 or 84) shown in FIG. 3 is attached instead of one of the embedded objects (63 or 64). It is also possible. Further, in the embodiment shown in FIG. 3, the number of the attached objects (83 or 84) is one, or the embedded object (63 or 64) shown in FIG. 2 is attached instead of one of the attached objects (83 or 84). Is also possible. Furthermore, in FIG.
5 can be attached to the outer peripheral side surface. Further, those skilled in the art can easily think of using these in combination with each other.

[0025]

According to the present invention, in a spindle motor in which a hub and a holder bonded and fixed to the hub are made of dissimilar metals, when a temperature change occurs due to a difference in thermal expansion between both members, a bonding portion is formed. This completely solves the problems of peeling, loss of sealing performance, and detachment of the magnetic fluid sealing device.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a sealing device according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a sealing device according to a second embodiment of the present invention.

FIG. 3 is a sectional view showing a sealing device according to a third embodiment of the present invention.

FIG. 4 is a cross-sectional view showing the structure of a known spindle motor.

FIG. 5 is a cross-sectional view showing an example of a sealing device used for a known spindle motor.

FIG. 6 is a cross-sectional view showing another example of a sealing device used in a known spindle motor.

[Explanation of symbols]

20: Sealing device 21: Rotor hub 2
2: Holder means 23: Seal means 25: First holder 2
6: Second holder 30: Spacer 31: Magnetic plate 3
2: Magnetic plate 33: Shaft 34: Magnetic fluid 3
5: magnetic fluid 36: first flat portion 37: hanging portion 3
8: second flat portion 39: side surface 40: enlarged diameter portion 4
1: first fixing means 42: second fixing means 43: third fixing means 4
4: flat extension part 45: vertical extension part 46: fourth fixing means 4
7: Fifth fixing means 50: Sealing device 51: Rotor hub 5
2: Holder means 53: Seal means 54: First flat part 5
5: vertical portion 56: second flat portion 57: shaft 5
8: enlarged diameter portion 59: first fixing means 60: second fixing means 6
1: third fixing means 62: fourth fixing means 63: embedded object 6
4: embedded object 70: sealing device 71: rotor hub 7
2: Holder means 73: Seal means 74: First flat part 7
5: vertical portion 76: second flat portion 77: shaft 7
8: enlarged diameter portion 79: first fixing means 80: second fixing means 8
1: Third fixing means 82: Fourth fixing means 83: Sticking object 8
4: Adhesion

Claims (11)

[Claims] 1. A magnetic fluid sealing device (20) fixed to a hub (21), the magnetic fluid sealing device (20) having a holder (22) and a seal (23), and the holder (22) is fixed to the hub (21). In a spindle motor in which the sealing means 23 is fixed to the holder means 22, by interposing a material having a smaller coefficient of thermal expansion than the material constituting the holder means 22 in the holder means 22, When a temperature difference occurs between the holder means 22 and the hub 21,
A spindle motor characterized in that deformation due to thermal stress at a junction with the spindle motor is limited. 2. The method according to claim 1, wherein the holder means 22 comprises:
The first holder 25 holding the sealing means 23 and the first holder 25
A second holder 26 holding the holder 25,
The second holder 26 is made of a material having a lower coefficient of thermal expansion than the material forming the first holder 25, and at least the second holder 26 is in a fixed relationship to the hub 21. A spindle motor. 3. The spindle motor according to claim 2, wherein the first holder 25 is formed of an aluminum material and the hub 21 is formed of a stainless material. 4. The first holder 2 according to claim 2, wherein
A spindle motor, wherein both the fifth holder and the second holder are in a fixed relationship with respect to the hub. 5. The holder according to claim 1, wherein the holder means 52 embeds and mounts an embedded material (63 and / or 64) having a coefficient of thermal expansion smaller than that of a material forming the holder 52. A spindle motor. 6. The spindle motor according to claim 5, wherein the holder means 52 is formed of an aluminum material and the hub 51 is formed of a stainless material. 7. The method according to claim 6, wherein the holder means 52 comprises:
The first flat portion 54 includes a first flat portion 54, a second flat portion 56, and a hanging portion 55 connecting the two.
A spindle motor, wherein an embedded object (63 and / or 64) is embedded and mounted on at least one of the upper surface of the fourth member 4 and the lower surface of the second flat portion 56. 8. The apparatus according to claim 1, wherein the holder means 72 sticks and mounts an attachment (83 and / or 84) having a coefficient of thermal expansion smaller than that of a material forming the holder 72. A spindle motor. 9. The spindle motor according to claim 8, wherein the holder means 72 is formed of an aluminum material, and the hub 71 is formed of a stainless steel material. 10. The holding means 72 according to claim 8, wherein the holder means 72 comprises a first flat part 74, a second flat part 76, and a hanging part 75 connecting the two.
A spindle motor, wherein an adherend (83 and / or 84) is attached and placed on one of the upper surface of the flat portion 74 and the upper surface of the second flat portion 76. 11. The holding means 72 according to claim 8, wherein the holder means 72 comprises a first flat portion 74, a second flat portion 76, and a hanging portion 75 connecting the both. A spindle motor, wherein an object to be attached is attached and mounted on an outer peripheral side portion.