JP3529971B2 - Spindle motor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor, and more particularly to a separate bearing type spindle motor. More specifically, the present invention relates to a spindle motor that does not generate noise during operation and can be assembled in a short time and at low cost.

[0002]

2. Description of the Related Art Various separate bearing type spindle motors have been announced so far. For example, in FIG.
There is JP-A-7-286619. In this spindle motor 1, a rotor hub 6 is rotatably supported via a pair of bearings 4 and 5 that are vertically separated from each other on a shaft 3 whose lower end is fixedly held at a central portion of a bracket 2. Further, a stator 7 is fixed to the shaft 3 between both bearings 4 and 5, and a rotor magnet 8 is provided on the inner peripheral surface of the rotor hub 6 so as to face the stator with a minute gap on the outer periphery of the stator 7. Is stuck.

In this spindle motor 1, a stepped portion 3a is formed in the lower portion of the shaft 3, and the rear bearing 5 and the stator 7 are positioned on the lower surface and the upper surface of the stepped portion 3a, respectively. In the assembly process of the stator 7, the stator 7 is inserted into the shaft 3 from above and the adhesive is interposed between the outer peripheral surface of the shaft 3 and the inner peripheral surface of the stator 7 so that the stator 7 is attached to the shaft 3. After fixing, the front bearing 4 is fixed to the outer peripheral surface of the upper portion of the shaft 3 with an adhesive.

A spindle motor as shown in FIG. 5 is also known as another separate bearing type spindle motor (Japanese Patent Laid-Open No. 7-336977).
In this spindle motor 10, a shaft 11 having a lower end fixedly held by a base such as a hard disk device
The rotor hub 15 is rotatably supported by the front bearing 12, the rear bearing 13, and the annular bush 14 fixed to the rear bearing 13, and both bearings 12,
The stator 17 is fixed via the core holder 16 fixed to the shaft 11 between the stators 13, and the stator 17 is provided with a minute interval on the outer periphery thereof.
A rotor magnet 18 is fixed to the inner peripheral surface of the rotor hub 15 so as to face the above. Here, the core holder 16 has a circular flat plate portion 16a extending radially outward from the shaft 11 to the vicinity of the outer peripheral portion of the stator 17, and a shaft 11 from the inner peripheral portion of the flat plate portion 16a. And a cylindrical portion 16b extending to an intermediate position of the stator 17 along the outer peripheral surface thereof. The inner diameter of the cylindrical portion 16b is such that it fits tightly on the shaft 11, while the outer diameter of the cylindrical portion 16b is such that it fits tightly on the inner peripheral portion of the stator 17. ing.

In this spindle motor 10, a stepped portion 1 that supports a core holder 16 on a lower portion of a shaft 11 is provided.
1a and a stepped portion 11b that supports the rear bearing 13
Are formed to position the core holder 16 and the rear bearing 13. In the assembling process , first, the rear bearing 13 is adhesively held on the stepped portion 11b on the lower outer peripheral surface of the shaft 11, and then,
The core holder 16 is inserted into the stepped portion 11a of the intermediate outer peripheral surface of the shaft 11 or the core holder 16 having the stator 17 adhered and held in advance from above the shaft 11, and the outer peripheral surface of the shaft 11 and the cylindrical portion 16 of the core holder 16 are inserted.
The core holder 16 is fixed to the shaft 11 with an adhesive interposed between the core holder 16 and the inner peripheral surface of b, and then the front bearing 12 and the rotor magnet 18 are fixed to the inner peripheral surface in advance on the outer peripheral surface of the upper portion of the shaft 11. Rotor hub 15
Are fixed with an adhesive.

[0006]

However, in the first spindle motor 1 shown in FIG. 4, when the stator 7 is mounted on the shaft 3, the stator 7 is inserted into the shaft 3 and then the stator 7 is stepped. It is necessary to slide along the outer peripheral surface of the shaft 3 up to the attachment portion 3a. However, during the sliding movement, the stator 7 may be scratched on the outer peripheral surface of the shaft 3. If this scratch occurs on the mounting surface of the front bearing 4 of the shaft 3, the mounting state of the front bearing 4 tends to fluctuate, stable rotation of the rotor hub 6 is difficult to obtain, and noise is generated. There was a problem that it could be the cause. In order to prevent the occurrence of such scratches, it is necessary to improve the accuracy of the stator 7 itself and the accuracy of the assembly device of the spindle motor 1, which is a significant cost issue. Furthermore, in the spindle motor 1 having such a configuration, during the assembly process,
After fixing the stator 7 to the shaft 3 with an adhesive, the front bearing 4 is fixed to the shaft 3. However, in order to prevent displacement of the stator 7, an adhesive for fixing the stator 7 to the shaft 3 is used. It is necessary to wait for the resin to be completely cured before proceeding to the next step. Therefore, there is also a problem that the assembly time is extended by the curing time of the adhesive. Further, in forming the shaft 3, since it is necessary to form the stepped portion 3a at a lower position thereof, there is a problem that the whole is more difficult to process than a shaft having the same diameter.

Further, also in the second spindle motor 10 shown in FIG. 5, when the core holder 16 is attached to the shaft 11, the core holder 16 is scratched on the outer peripheral surface of the shaft 11 instead of the stator 7 of FIG. The same is true for scratches. As a result, the same problem as in the case of the spindle motor of FIG. 4 remains. Also,
In the spindle motor 10, similar to the spindle motor 1 shown in FIG. 4, in the assembly process, the core holder 16 is fixed to the shaft 11 with an adhesive, and then the front bearing 12 is fixed to the shaft 11. ,
It is necessary to wait for the adhesive for fixing the core holder 16 to the shaft 11 to be completely cured before proceeding to the next step, which increases the assembly time by the curing time of the adhesive, and also the shaft 11 In the molding process of
It is necessary to form the two stepped portions 11a and 11b in the lower position, and it is difficult to process the shaft as a whole as compared with the case of the shaft having the same diameter, as in the case of the embodiment shown in FIG. is there.

An object of the present invention is to completely solve the problems of these known spindle motors by extremely simple means.

[0009]

In order to solve the above problems, the present invention provides a housing 22 and a shaft 24 having a lower end fixedly held near the center of the housing 22,
A rotor hub 30 rotatably mounted on the shaft 24 via a front bearing 26 and a rear bearing 28, and the shaft between the rotor hub 30 and the shaft 24 and between the pair of bearings 26, 28. Stator 32 fixed to 24
And a rotor magnet 36 attached to the inner peripheral surface side of the rotor hub 30 and fixed to the outside of the stator 32 in the radial direction at a slight interval. The inner ring of the rear bearing 28 is inserted through the hollow hole 48d having the diameter d4 which is initially larger than the diameter d1 of the shaft 24.
Mounted in abutting state, the fitted into the core holder 48 of the stator 32, the core holder 48 is a shaft 24
The stator 32 is fixed in an interference fit state , and the stator 32 is fixed to the shaft 24 via the core holder 48.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIG. 1 which discloses a preferred embodiment of the present invention. A spindle motor 20 of the separate bearing type shown in FIG. 1 includes a bracket or housing 22, a shaft 24 having a lower end fixedly held near the center of the housing 22, and the shaft 24.
On the other hand, between the rotor hub 30 made of a non-magnetic material such as aluminum and rotatably mounted via the front bearing 26 in the upper position in the drawing and the rear bearing 28 in the lower position in the drawing, and the pair of bearings 26, 28. 3 fixed to the shaft 24 at
2, a yoke 34 attached to the inner peripheral surface side of the rotor hub 30, and a yoke 34 fixed between the yoke 34 and the stator 32 at a slight distance outward in the radial direction of the stator 32. And a rotor magnet 36 that is formed. When the rotor hub is made of a magnetic material, the rotor hub functions as a yoke, and the rotor magnet is directly attached to the inner peripheral surface of the rotor hub.

In the housing 22 of the present invention, an opening 22a for receiving the lower end of the shaft 24 is provided in the vicinity of the central portion of the housing 22, and a rising portion 2 which rises upward in the outer peripheral portion.
It has 2b integrally.

The shaft 24 used in the present invention has a columnar shape having the same diameter d1 over the entire length. At the center of the shaft 24, there is provided a hole 24a extending upward from the lower end of the shaft 24 to the vicinity of the intermediate portion along the axial direction. One end of the hole 24a is in contact with the stator 32 and the other end of the hole 24a is attached to the housing 22.
The lead wire 40 leading to 38 is inserted. The middle portion of the lead wire 40 is covered with the sealing member 42 as needed to prevent the hole 2
It is sealed and held in 4a.

The lower end of the shaft 24 is fixed to the housing 22 by using an adhesive known per se. Further, an inner ring of the rear bearing 28 is fitted and held, preferably using an adhesive, just above the lower end fixed to the housing 22. The rear bearing 28 is positioned with respect to the upper surface of the housing.

A bearing holder 44 is preferably fixed to the outer ring of the rear bearing 28. The bearing holder 44 has a vertical rising portion 44a rising from the outer ring of the rear bearing 28 toward the front bearing 26, and an expanding portion extending radially outward integrally with the upper portion of the vertical rising portion 44a. Diameter part 44
and b. The inner peripheral portion of the expanded diameter portion 44b presses and holds the rear bearing 28 toward the housing 22 and thus holds the rear bearing 28 at a predetermined position. Further, the outer peripheral portion of the expanded diameter portion 44b has a rotor hub 30.
Is closely supported. Here, the inner peripheral surface of the vertical rising portion 44a is fixed to the outer ring of the rear bearing 28 by using an adhesive as required. On the other hand, the vertical rising portion 44a
The outer peripheral surface of is disposed opposite to the inner peripheral surface of the rising portion 22b of the housing 22, and a labyrinth seal is formed by a minute gap formed on the opposed surface. This prevents the oil mist component that may be generated from the rear bearing 28 from scattering to the outside of the spindle motor 20.

The inner ring of the front bearing 26 is fixed to the upper portion of the shaft 24 by substantially the same means as the rear bearing 28. A rotor hub 30 is attached to the outer ring of the front bearing 26.

The rotor hub 30 has an upper wall portion 30a extending radially outward from the front bearing 26,
A hanging portion 30b hanging from the outer peripheral portion of the upper wall portion 30a.
And a lower wall portion 30c connected to the lower end portion of the hanging portion 30b and closely supported by the enlarged diameter portion 44b of the bearing holder 44.

On the inner peripheral portion of the upper wall portion 30a, a projection portion that supports the front bearing 26 from below and holds the front bearing 26 at a predetermined position, and an outer ring of the front bearing, if necessary. It has a vertical wall portion fixed by an adhesive or the like, and an extension portion further extending upward along the axial direction from the vertical wall portion. A labyrinth cap 46 is provided on the radially inner surface of the extension and outside the front bearing 26, that is, on the upper surface in the drawing.
Are fixed by, for example, press fitting. A hole through which the shaft 24 passes is formed in the center of the labyrinth cap 46. The holes and the outer surface of the shaft 24 forms a minute gap, the minute gap forms a rabbi <br/> rinsing seal. This prevents the oil mist component that may be generated from the front bearing 26 from scattering to the outside of the spindle motor 20.

A yoke 34 is fixed to the inner surface of the hanging portion 30b by a known means. Further, an enlarged diameter portion 44b of the bearing holder 44 is fixed to the inner surface of the lower wall portion 30c by using an adhesive or the like, if necessary, and the outer surface of the lower wall portion 30c is radially outward. A projecting step is formed. The step portion has a function of holding a disk (not shown).

The shaft 24 has the shaft 24
The stator 32 is fixed in a space between the front bearing 26 and the rear bearing 28, which is a space between the front bearing 26 and the inner surface of the hanging portion 30b forming the rotor hub 30. In order to fix the stator 32 to the shaft 24, the core holder 48 is used in the present invention.

As shown in FIG. 2, the core holder 48 is composed of an upper portion 48a and a lower portion 48b. The outer diameter dimension d2 of the upper portion 48a is smaller than the outer diameter dimension d3 of the lower portion 48b, and both portions are connected by a step portion 48c, and are preferably integrally formed of, for example, an aluminum material. Furthermore, this core holder 48
Has a hollow hole 48d having a constant inner diameter dimension d4 that penetrates vertically from the upper portion 48a to the lower portion 48b. The hollow hole 48d has an inner diameter slightly larger than the outer diameter d1 of the shaft 24, for example, about several μm. Therefore, when the core holder 48 is inserted into the shaft 24, there is no risk that the core holder 48 will scratch the surface of the shaft 24. Here, as shown by a chain double-dashed line in FIG. 2, a groove 48e extending in the vertical direction may be formed in the upper portion 48a in order to absorb the deformation of the upper portion inward in the radial direction. . This groove 48
The number of e is not limited to one, and a plurality of e can be provided, but preferably three, and they are arranged at intervals of 120 °. When providing a plurality of grooves, it is desirable that they be arranged at equal angles to each other.
This is to ensure that the entire upper portion 48a is deformed uniformly. Such a groove 48e is less necessary when the core holder 48 is made of a soft material such as aluminum, but is preferably provided when the core holder 48 is made of a hard material other than this. Of course, it can be provided in the case of aluminum or the like. Furthermore, the upper end corner portion 48f of the upper portion 48a is chamfered sufficiently smoothly. This means that the stator 32 can smoothly and surely during assembly, as will be described later.
This is so that it can enter the upper portion 48a of the.

The lower end 48h of the lower portion 48b of the core holder 48 is arranged in contact with the rear bearing 28.
As described above, the dimension d4 of the hollow hole 48d of the core holder 48
Is slightly larger than the dimension d1 of the shaft 24, it is easy to insert the core holder 48 into the shaft 24. At this time, the core holder 48 does not scratch the shaft 24.

The stator 32 is mounted on the upper portion 48a of the core holder 48 from above. Where the stator 32
The inner diameter dimension d6 of the core holder 48 is larger than the outer diameter dimension d1 of the shaft 24 (d6> d1).
It is set to be slightly smaller than the outer diameter dimension d2 of 8a by, for example, several tens of μm (d2> d6). That is, each dimension is
The relationship is d3>d2>d6>d4> d1.

Thus, the upper portion 48a of the core holder 48 which is inserted in the shaft 24 in a slightly loose state.
When the stator 32 is forcibly pushed in from above to dispose the stator 32, the stator 32 is inserted into the upper portion 48a of the core holder 48 through the chamfered portion of the upper end corner portion 48f of the core holder 48, Further, the stator 32 reaches the stepped portion 48c of the core holder while pushing the upper portion 48a of the core holder 48 inward in the radial direction by forcing the stator 32 downward. At this time, the upper portion 48a is forcibly pressed to the shaft 24 side due to the above-mentioned dimension, and the shaft 24 is tightened. As a result, the stator 32 is immovably fixed to the shaft 24 via the core holder 48. That is, the stator 32 is press-fitted and fixed to the core holder 48, and the upper portion 48a of the core holder 48 contracts radially inward and is tightly fitted to the outer peripheral surface of the shaft 24. The lower surface of the inner peripheral edge of the stator 32 is brought into contact with the stepped portion 48c of the core holder 48 and is appropriately positioned.
An adhesive is applied in advance to the portion of the shaft 24 where the core holder 48 is to be positioned, the outer surface of the upper portion 48a of the core holder 48 and the step portion 48c, and the core holder 48 is attached to the shaft 24 and the core holder 48 to the core holder 48. It is preferable that the stators 32 are adhesively fixed to each other.

FIG. 3 shows another core holder embodiment. In the core holder 48 shown in FIGS. 1 and 2, the upper portion 48a is configured to have a constant wall thickness from the step portion 48c to the upper end portion 48g, but the core holder 48A shown in this embodiment has the same structure as that described above. On shaft 24
Has a hollow hole 48d of a constant size d4 that vertically penetrates in order to receive the outer diameter of the upper portion 48a so that the wall thickness becomes thinner as the upper portion 48a approaches the upper end portion 48g from the step portion 48c. Are different in that they are becoming smaller. That is, the outer peripheral edge diameter of the step portion 48c is the same as the outer diameter dimension d3 of the lower portion 48b, and the step portion 4c
The inner peripheral diameter of 8c is the same as the outer diameter dimension d2 of the upper portion 48a shown in FIG. 2, but the outer diameter dimension of the upper end portion 48g of the core holder 48A shown in FIG. 3 is the same as the outer diameter dimension 48g of the core holder 48 shown in FIG. Has a diameter d5 smaller than the outer diameter dimension d2. Here, the dimension d of the core holder
2, d3, d4, d5 and the inner diameter dimension d6 of the stator 32
And the outer diameter dimension d1 of the shaft 24 are d3>d2> d
6>d5>d4> d1. Also in this case, it is preferable that the upper end corner portion 48f be chamfered and that a predetermined number of grooves 48e be provided as necessary as in the previous embodiment.

In this embodiment, since the respective dimensions are in the relationship described above, the work of mounting the stator 32 on the core holder 48 can be accomplished more easily.

A rotor magnet 36 is arranged outside the stator 32 in the radial direction at a slight interval. The rotor magnet 36 is fixed to the inner surface of the yoke 34 with an adhesive or the like.

The spindle motor 20 of the present invention will be described below.
The procedure for assembling is described below. First, the lower end of the shaft 24 is fixed to the housing 22 by using an adhesive as needed. After that, the inner ring of the rear bearing 28 having the bearing holder 44 attached to the outer ring is adhesively fixed to the shaft 24. When mounting the rear bearing 28 on the shaft 24, the rear bearing 28
The 28 position of the rear bearing with respect to the housing 22 is surely specified by abutting the lower end surface of the inner ring of the above with the upper surface of the housing 22. It is also possible to mount the rear bearing 28 and / or the bearing holder 44 on the shaft 24 in advance before fixing the shaft 24 to the housing 22, and then fix the shaft 24 to the housing 28. In this case, since the rear bearing 28 can be inserted from the lower portion of the shaft 24, the work is easy.

Next, the core holder 48 is fitted into the shaft 24. The inner diameter d4 of the core holder 48 is slightly larger than the outer diameter d1 of the shaft 24.
There is no concern that 8 damages the surface of the shaft 24. It is preferable that an adhesive agent is applied in advance to the portion of the shaft 24 to which the core holder 48 is fixed, and if the core holder 48 is arranged at a predetermined position, the core holder 48 is surely fixed by the adhesive agent at that position.

After that, the lead wire 40 of the stator 32, which is formed by winding a winding around the core in advance, is inserted into the hole 24a of the shaft 24, and the lead wire 40 is inserted into the hole 24a.
After being fixed by sealing with a sealing member 42, the stator 32
Is press-fitted onto the outer peripheral surface of the upper portion 48a of the core holder 48. At this time, it is preferable to apply an adhesive in advance to the outer peripheral surface of the upper portion 48a of the core holder 48. This is to ensure that if the stator 32 is arranged at a predetermined position on the core holder 48, it will be securely fixed by the adhesive at that position. Diameter d of the inner peripheral surface of the stator 32
Since 6 is slightly smaller than the diameter d2 on the outer peripheral surface of the upper portion 48a of the core holder 48, the inner peripheral surface of the stator 32 is difficult to fit into the outer peripheral surface of the upper portion 48a of the core holder 48, but is larger than the upper portion 48a of the core holder 48. By sufficiently chamfering the upper corner portion 48f of the, the chamfered portion provides a means for introducing the stator 32. Therefore, the chamfering operation is preferably performed until the diameter of the chamfered upper end portion 48g is substantially equal to or slightly smaller than the dimension d6. Further, as shown in FIG. 3, the outer diameter dimension of the upper portion 48a is gradually reduced as it goes upward, and the outer diameter dimension d5 of the upper end outer peripheral surface of the upper portion 48a is made smaller than the diameter d6 of the inner peripheral surface of the stator 32. By making it small, the stator 32 can be fitted and inserted more easily.

Next, the outer ring of the front bearing 26 is fixed to the rotor hub 30 in which the yoke 34 and the rotor magnet 36 have been assembled in the hanging portion 30b of the rotor hub 30 in advance. Then, the inner ring of the front bearing 26 is inserted into the shaft 24, and the front bearing 26 is adhesively fixed to the shaft 24. At the same time, the outer peripheral portion of the expanded diameter portion 44b of the bearing holder 44 is fitted to the lower end portion 30c of the rotor hub 30. At this time, it is preferable to apply an adhesive to the outer ring positioning portion of the shaft 24 and the lower end portion 30c of the rotor hub 30. This is because when each member is positioned at a predetermined position, it is securely fixed by the adhesive at that position.

Finally, the tip of the lead wire 40 is soldered to the FPC 38 attached to the housing 22, and the labyrinth cap 46 is adhesively fixed to the upper portion of the rotor hub 30.

[0032]

The spindle motor 20 according to the present invention
In, the stator 32 is fixed to the shaft 24 via the core holder 48. Therefore, the inner diameter of the stator 32 can be made sufficiently larger than the outer diameter of the shaft 24, and the bearing holding surface of the shaft 24 is not damaged when the stator 32 is inserted into the shaft 24.
Displacement of the front bearing 26 can be prevented, and problems such as noise and heat generation can be completely solved. Also,
Since the core holder 48 can be placed in the shaft 24 in a loosely fitted state when it is inserted, the core holder 48 does not damage the surface of the shaft 24.

The core holder 48 is bonded and fixed to the shaft 24, and the stator 32 is bonded and fixed to the core holder 48. The stator 32 is firmly fixed to the shaft 24 through the core holder 48 by an interference fit, so that the adhesive is hardened. You can immediately move to the next process without waiting, and the assembly time can be greatly reduced.

When the adhesive between the shaft 24, the core holder 48, and the stator 32 hardens, they are firmly fixed to each other more than the interference fit, the fixing strength is increased, and noise prevention can be achieved more reliably.

[Brief description of drawings]

FIG. 1 is a diagram showing a sectional view of a spindle motor according to the present invention.

FIG. 2 is a perspective view showing an example of a core holder used in the spindle motor according to the present invention.

FIG. 3 is a cross-sectional view showing another example of the core holder used in the spindle motor according to the present invention.

FIG. 4 is a sectional view showing an example of a known spindle motor.

FIG. 5 is a sectional view showing an example of another known spindle motor.

[Explanation of symbols]

20 spindle motor 22 Hansing 24 shaft 26 Front bearing 28 Rear bearing 30 rotor hub 32 stator 36 rotor magnet 48 core holder 48a upper part 48b lower part 48c step 48d hollow hole 48e groove

Claims (3)

(57) [Claims] 1. A housing 22 and a shaft 24 having a lower end fixedly held near the center of the housing 22.
A rotor hub 30 rotatably mounted on the shaft 24 via a front bearing 26 and a rear bearing 28, and between the rotor hub 30 and the shaft 24 between the pair of bearings 26, 28. A rotor mounted between the stator 32 fixed to the shaft 24 and the inner circumferential surface of the rotor hub 30 and having a small gap radially outward of the stator 32. In a spindle motor including a magnet 36, core holders 48 and 48A are used to fix the stator 32 to the shaft 24.
8A has a rear bearing through a hollow hole 48d having a diameter d4 which is initially larger than the diameter d1 of the shaft 24.
Mounted on the inner ring 28 in contact with the state, the fitted to <br/> core holder 48,48A of the stator 32, the core holder 48,48A are fixed <br/> in a state close fit to the shaft 24, A spindle motor in which the stator 32 is fixed to the shaft 24 via core holders 48, 48A. 2. The spindle motor according to claim 1, wherein the shaft 24 has an outer diameter of a constant dimension over the entire length. 3. A core holder 48 is composed of an upper portion 48a and a lower portion 48b, which are connected by a step portion 48c, and a hollow hole having an inner diameter d4 which vertically penetrates to receive the shaft 24. 48d, the outer diameter d2 of the upper portion 48a is smaller than the outer diameter d3 of the lower portion 48b, and the inner diameter d6 of the stator 32 attached to the core holder 48 before the assembly is smaller than the outer diameter of the upper portion 48a. The spindle motor according to claim 1, wherein the spindle motor has a diameter smaller than the diameter d2.