JP2004289982A - Spindle motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the breakage of a magnetic head by surely discharging static electricity that is generated on a disc, without extending the height of a motor in the axial direction. <P>SOLUTION: A shaft 2 whose one tip end is fixed to a hub 5 is rotatably inserted in a sleeve 6 provided upright in a through hole 1B of a motor base 1, while being supported in the thrust direction by a thrust bearing 11 provided on the other tip end side. A part of the bottom surface 3 of the motor base 1 is formed with a recess 4 whose one side is opened to the through hole 1B. A conductive adhesive 18 is applied to bridge the recess 4 and a thrust plate 7, so that the motor base 1 is electrically connected to the thrust plate 7. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a spindle motor, and more particularly to a spindle motor suitable for a hard disk drive (hereinafter, HDD).
[0002]
[Prior art]
Conventionally, in an HDD, a shaft is rotatably supported in order to prevent electric charges charged on a signal recording / reproducing disk from discharging to a magnetic head and destroying the head, or a signal recorded on the signal recording / reproducing disk from being destroyed. 2. Description of the Related Art There is known a motor in which a sleeve to be fitted is fitted into a shaft hole provided in a motor base, and a conductive adhesive is filled and fixed between both faces to be fitted, so that conduction between the two is established. As an example, there is a motor described in Patent Document 1.
[0003]
[Patent Document 1]
JP-A-11-167765
[Problems to be solved by the invention]
By the way, the sleeve of the spindle motor and the motor base need to be firmly fixed with high accuracy.
However, the strength and long-term reliability of the conductive adhesive are not always sufficient as compared with the non-conductive adhesive, and it is desirable that the sleeve and the motor base be fixed as strongly as possible with the non-conductive adhesive.
[0005]
Therefore, a non-conductive adhesive is filled between the outer peripheral surface of the sleeve and the inner surface of the shaft hole of the motor base into which the sleeve is inserted, and the two are fixed.Furthermore, at both end surfaces on the bottom surface of the motor base, There has been proposed a motor in which conduction is obtained by applying a conductive adhesive so as to straddle both.
[0006]
This motor will be described with reference to FIG.
FIG. 4 is a half sectional view of a spindle motor in which a shaft 102 fixed to a rotor hub 105 is rotatably supported on a motor base 101 by a radial dynamic pressure bearing 110 and a thrust dynamic pressure bearing 111.
The sleeve 106 on which the shaft 102 is inserted and the motor base 101 are bonded and fixed with a non-conductive adhesive 116.
The sleeve 106 and the motor base 101 are electrically connected to each other on the bottom side (the lower side in the figure) of the motor base 101 by the conductive adhesive 18 applied so as to straddle both end faces.
[0007]
As a result, charges generated on the signal recording / reproducing disk 22 attached to the rotor hub 105 can be released to the motor base 101 via the rotor hub 105, the shaft 102, and the sleeve 106, and via the conductive adhesive 18.
[0008]
By the way, the HDD is required to be miniaturized, and the overall size of the motor needs to be as small as possible. However, the raised portion of the applied conductive adhesive 18 which has solidified and protrudes from the bottom of the motor, However, there is a problem that the height dimension (dimension t in FIG. 4) is increased accordingly.
[0009]
On the other hand, since the fixing between the sleeve 106 and the motor base 101 is performed using a non-conductive adhesive, a large amount of the conductive adhesive 18 must be applied in order to ensure conduction between the two. There was a problem that it became even larger.
[0010]
Therefore, the problem to be solved by the present invention is to reliably discharge static electricity generated on a signal recording / reproducing disk to a motor base without increasing the axial height of a motor and to reduce a signal recorded on a magnetic head or a signal recording / reproducing disk. It is an object of the present invention to provide a spindle motor for preventing breakage of a spindle motor.
[0011]
[Means for Solving the Problems]
In order to solve the above problems, the present invention has the following configuration as means.
That is, in the first aspect, the shaft 2 having one end fixed to the hub 5 on which the disk 22 is mounted is rotatably fitted into the sleeve 6 erected in the through hole 1B of the motor base 1 and the other is freely rotatable. The thrust bearing 11 is supported in a thrust direction by a thrust bearing 11 provided on a tip end side, and the thrust bearing 11 is provided with the sleeve 6, the flange 8 provided on the other tip side of the shaft 2, and the flange 8. A thrust plate 7 fixed to the sleeve 6 so as to face the spindle motor.
A recess 4 is formed in a part of the surface 3 of the motor base 1 on the side opposite to the hub 5, the recess 4 having one opening in the through hole 1 </ b> B, and is electrically conductive so as to straddle the recess 4 and the thrust plate 7. The motor according to claim 1, wherein the motor base (1) and the thrust plate (7) are electrically connected to each other by applying a conductive adhesive (18).
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to FIGS.
The spindle motor includes a rotor section 21 and a stator section 20, and has a structure in which the rotor section 21 is rotatably supported on the stator section 20 by the radial dynamic pressure bearing 10 and the thrust dynamic pressure bearing 11. I have.
First, the structure will be described in the order of the stator section, the rotor section, the bearing section, and the application of the conductive adhesive.
[0013]
(1) Stator section The stator section 20 is composed of the motor base 1, the sleeve 6, and the core 13 around which the coil 12 is wound.
The motor base 1 is formed of aluminum or an aluminum alloy, and a cylindrical wall 1A is provided upright at a substantially central portion thereof.
The sleeve 6 is fixed to the sleeve hole 1B formed on the inner surface of the cylindrical wall 1A by adhesion.
The sleeve 6 is made of a stainless or copper material and is formed in a substantially cylindrical shape having a shaft hole 6E.
At two places on the inner peripheral surface of the shaft hole 6E, first and second dynamic pressure grooves 10a and 10b each having a herringbone (fish bone) shape are provided over the entire circumference. FIG. 1 schematically shows the first and second dynamic pressure grooves 10a and 10b.
The inner diameter of a portion of the shaft hole 6E sandwiched between the first dynamic pressure groove 10a and the second dynamic pressure groove 10b is larger than the inner diameter of the portion of the first and second dynamic pressure grooves 10a and 10b. Is formed.
[0015]
Further, a first wall 6A and a second wall 6B are formed at the lower end of the shaft hole 6E (on the side where the motor base 1 is inserted), and each of the first wall 6A and the second wall 6B has a different diameter. The lower end is opened stepwise by the connected first seating surface 6C and the second seating surface 6D connected to the second wall 6B (see FIG. 2).
A circular thrust plate 7 is fixed to the first wall 6A by press-fitting, and the press-fitted portion is sealed with a non-conductive adhesive 16.
In this embodiment, the thickness t3 of the thrust plate 7 is about 0.5 mm.
[0016]
(2) About the rotor part The rotor part 21 is composed of the hub 5, the shaft 2, the flange 8, the magnet 14, and the rotor yoke 15.
The hub 5 is formed in a substantially cylindrical shape having a shaft hole 5A of aluminum or an aluminum alloy material, and a shaft 2 formed of a stainless steel material is fixed to the shaft hole 5A by press fitting.
An annular flange 8 is fixed to the lower end of the shaft 2 (the side opposite to the press-fitted hub) by press-fitting.
[0017]
A signal recording / reproducing disk 22 is mounted on the outer peripheral surface of the hub 5, and a magnet 14 and a rotor yoke 15 are fixed to the lower portion of the hub 5 by bonding or caulking.
[0018]
(3) Bearing (a) There is a slight gap between the radial bearing shaft 2 and the shaft hole 6E of the sleeve 6, and a lubricating oil 17, which is a viscous fluid, is filled and held therein.
When the shaft 2 rotates during operation of the spindle motor, the first and second dynamic pressure grooves 10a and 10b formed on the inner surface of the shaft hole 6E cause the dynamic pressure to push the shaft 2 from the outside in the direction of the central axis. , The radial dynamic pressure bearing 10 is obtained.
[0019]
(B) On the upper and lower surfaces of the flange 8 press-fitted and fixed to the lower end of the thrust bearing shaft 2, a herringbone-shaped (not shown) dynamic pressure groove is formed on the entire surface.
The thickness of the flange 8 is formed to be smaller by 10 to 20 μm than the depth (axial direction) of the second wall portion 6B, and one thrust plate 7 is in close contact with the first seating surface 6C. Since they are fixed, the flange 8 and the thrust plate 7 and the flange 8 and the second seating surface 6D are arranged to face each other with a gap of 10 to 20 μm.
[0020]
Since the lubricating oil 17, which is a viscous fluid, is filled and held in the gap, a dynamic pressure is generated by the dynamic pressure grooves on the upper and lower surfaces of the flange 8 when the shaft 2 and the flange 8 rotate integrally. .
The dynamic pressure is generated in a direction in which the rotor portion 21 is pushed down by the dynamic pressure groove on the upper surface of the flange 8 and in a direction in which the rotor portion 21 is pushed up by the dynamic pressure groove on the lower surface of the flange 8.
Then, the dynamic pressures in these two directions are balanced to provide the thrust dynamic pressure bearing 11 which stably holds the rotor portion 21 in a freely rotatable axial direction.
[0021]
In (a) and (b) described above, the example in which the dynamic pressure groove is formed on one of the two opposing surfaces has been described, but it may be formed on the other opposing surface or on both surfaces. . Further, another fluid such as air may be used as the viscous fluid.
[0022]
Next, an assembling procedure of the main part of the configuration described in (1) to (3) will be described.
(1) Press the flange 8 into the lower end of the shaft 2.
(2) The shaft 2 is inserted into the shaft hole 6E of the sleeve 6 from its lower end.
{Circle around (3)} The thrust plate 7 is fixed to the wall surface of the first wall portion 6A of the sleeve 6 by press-fitting or the adhesive 16 to perform sealing.
(4) Press the hub 5 into the upper end of the shaft 2.
(5) The lower end of the sleeve 6 is inserted into the motor base 1 and fixed with a non-conductive adhesive 16.
[0023]
(4) Application of Conductive Adhesive Signal As a path for effectively discharging static electricity generated on the recording / reproducing disk 22, the motor passes through the disk 22, the hub 5, the shaft 2, the radial dynamic pressure bearing 10, and the sleeve 6 respectively. There is a first route to base 1.
In the present embodiment, in addition to the first path, a second path to the motor base 1 via the disk 22, the hub 5, the shaft 2, the thrust dynamic pressure bearing 11, and the thrust plate 7 is provided. There will be described in detail below with reference to FIGS. FIG. 2 is a sectional view taken along line AA in FIG.
[0024]
FIG. 3 is a diagram showing the bottom surface 3 of the spindle motor when the embodiment is viewed from the lower side of FIG.
As shown in the figure, on the bottom surface 3, the conductive adhesive 18 is applied so as to straddle the thrust plate 7 and the motor base 1 so as to sandwich the sleeve 6 therebetween.
A flexible printed circuit board 9 (hereinafter referred to as FPC 9) having a wiring pattern 19 for making an electrical connection to the outside is attached to the bottom surface 3 of the motor base 1 with an adhesive (not shown).
[0025]
The portion of the bottom surface 3 of the motor base 1 to which the conductive adhesive 18 is applied is a recess 4 having a width W of 3 mm and a depth t1 of 0.5 mm, and the conductive adhesive 18 is provided on the bottom surface 4A of the recess 4. It is applied (see FIG. 2).
On the other hand, the bottom surface 7A of the thrust plate 7 is arranged at a position recessed by the depth t2 from the bottom surface 3 of the motor base 1, and the bottom surface 4A and the bottom surface 7A are so set that the depths t1 and t2 are substantially the same. Is set.
[0026]
Therefore, since the adhesive 18 applied so as to straddle the thrust plate 7 and the motor base 1 does not flow to other portions, both can be securely bonded.
The recess 4 is provided at a position generally facing the FPC 9 with the shaft 2 interposed therebetween.
Therefore, even if the adhesive 18 flows for some reason, it does not reach the FPC 9 and the wiring pattern 19 of the FPC 9 is not short-circuited.
[0027]
In the present embodiment, as the conductive adhesive 18, for example, TB3380B manufactured by Three Bond Co., Ltd. can be used.
The amount to be applied is 0.002 cc to 0.005 cc, but this amount can be set to an optimal amount as appropriate.
In addition, the depth and size of the recess 4 (the area of the bottom 4A) also protrude from the bottom surface 3 of the motor base 1 with respect to the height t when the conductive adhesive 18 is solidified in accordance with the applied amount. Can be set to not.
[0028]
As a result, a conductive path between the motor base 1 and the thrust plate 7 is secured, so that static electricity generated on the disk 22 is guided from the shaft 2, the flange 8 and the thrust plate 7 to the motor base 1 via the conductive adhesive 18. Road can be secured.
Further, according to the above-described configuration, the solidified conductive adhesive 18 does not protrude from the bottom surface 3 of the motor base 1, so that the height of the motor body can be reduced.
[0029]
Further, even when the sleeve 6 and the motor base 1 are bonded to each other with the non-conductive adhesive 16 to increase the insulation resistance, electrical conduction between the thrust plate 7 and the motor base 1 can be obtained.
In addition, since the conductive adhesive 18 is also applied to the sleeve 6 sandwiched between them, electrical conduction between the sleeve 6, the thrust plate 7, and the motor base 1 is obtained, and the discharge is performed more reliably. be able to.
Accordingly, static electricity is discharged from the signal recording / reproducing disk 22 to the motor base 1 and the magnetic head is not damaged, so that no error occurs in recording / reproducing of the HDD or the recorded signal is not damaged.
[0030]
The embodiments of the present invention are not limited to the above-described configuration, and can be modified without departing from the gist of the present invention.
For example, the thrust plate 7 may have a bottom surface 7A in which only the portion to which the conductive adhesive 18 is applied is recessed. Of course, the bottom surface 7A, which is the concave portion, is desirably the same depth as the bottom surface 4A of the concave portion 4 where the conductive adhesive is applied to the motor base 1.
Further, the present invention is not limited to the spindle motor mounted on the HDD device, but may be a spindle motor mounted on another device.
[0031]
【The invention's effect】
As described in detail above, according to the present invention, static electricity generated in the signal recording / reproducing disk is reliably discharged to the motor base without increasing the axial height of the motor to record the static electricity on the magnetic head or the signal recording / reproducing disk. This has the effect of preventing the destruction of the signal.
[Brief description of the drawings]
FIG. 1 is a half sectional view showing an embodiment of a spindle motor of the present invention.
FIG. 2 is a half sectional view showing a main part in an embodiment of the spindle motor of the present invention.
FIG. 3 is a bottom view showing a main part in the embodiment of the spindle motor of the present invention.
FIG. 4 is a half sectional view illustrating a conventional spindle motor.
[Explanation of symbols]
1, 101 Motor base 1A Cylindrical wall 1B Sleeve hole 2, 102 Shaft 3 Bottom (of motor base) 4 Recess 4A Bottom (coated surface)
5, 105 (rotor) hub 5A, 6E shaft hole 6, 106 sleeve 6A, 6B first and second wall portions 6C, 6D first and second seating surfaces 6E shaft hole 7 thrust plate 7A bottom surface (coated surface)
8 Flange 9 Flexible printed circuit board (FPC)
10, 110 Radial dynamic pressure bearings 10a, 10b Dynamic pressure grooves 11, 111 Thrust dynamic pressure bearings 12 Coil 13 Core 14 Magnet 15 Rotor yoke 16, 116 Non-conductive adhesive 17 Lubricant 18 Conductive adhesive 19 Wiring pattern 20 Stator part 21 rotor section 22 signal recording / reproducing disc t height t1, t2 depth t3 thickness W width

Claims (1)

A shaft, one end of which is fixed to the hub on which the disc is mounted, is rotatably inserted into a sleeve provided upright in the through hole of the motor base, and a thrust bearing provided on the other end side in the thrust direction. While being supported,
The spindle motor, wherein the thrust bearing includes the sleeve, a flange provided at the other end of the shaft, and a thrust plate fixed to the sleeve so as to face the flange.
A recess is formed on a part of the surface of the motor base opposite to the hub, the recess being formed with one opening in the through hole, and a conductive adhesive is applied so as to straddle the recess and the thrust plate. A spindle motor configured to electrically connect the motor base and the thrust plate.

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