JP4723620B2 - Spindle motor - Google Patents

Description

  The present invention relates to a spindle motor, and more particularly to a spindle motor suitable for a hard disk drive (hereinafter referred to as HDD).

Conventionally, in a HDD, a shaft is rotatably supported in order to prevent the electric charge charged to the signal recording / reproducing disk from being discharged to the magnetic head and destroying the head or the signal recorded on the signal recording / reproducing disk. 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 sides of the fitting while being connected to each other. As an example, there is a motor described in Patent Document 1.
Japanese Patent Laid-Open No. 11-167765

Incidentally, the sleeve of the spindle motor and the motor base need to be firmly fixed with high accuracy.
However, the conductive adhesive does not necessarily have sufficient strength and long-term reliability as compared with the non-conductive adhesive, and it is desirable that the sleeve and the motor base are fixed as firmly as possible with the non-conductive adhesive.

  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 both are fixed. Further, on both end surfaces of 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.

This motor will be described with reference to FIG.
FIG. 4 is a half sectional view of a spindle motor in which the shaft 102 fixed to the rotor hub 105 is rotatably supported with respect to the motor base 101 by a radial dynamic pressure bearing 110 and a thrust dynamic pressure bearing 111.
The sleeve 106 into which the shaft 102 is inserted and the motor base 101 are bonded and fixed with a non-conductive adhesive 116.
In addition, the sleeve 106 and the motor base 101 are electrically connected to each other on the bottom surface side (the lower side surface in the figure) of the motor base 101 by the conductive adhesive 18 applied so as to straddle both end surfaces.

  As a result, electric 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 conductive adhesive 18 via the rotor hub 105, the shaft 102, and the sleeve 106.

  By the way, the HDD is required to be miniaturized, and the motor needs to be reduced in size as much as possible. However, the portion where the applied conductive adhesive 18 is solidified and protrudes protrudes from the bottom of the motor, and the motor There is a problem in that the height dimension of the second dimension becomes larger (dimension t in FIG. 4).

  On the other hand, since the sleeve 106 and the motor base 101 are fixed with a non-conductive adhesive, a large amount of the conductive adhesive 18 must be applied in order to ensure the conduction between the sleeve 106 and the motor base 101. There was a problem of becoming even larger. There is also a problem that the conductive adhesive 18 applied to the motor base may flow to other portions.

  Accordingly, an object of the present invention is to provide a spindle motor in which the conductive adhesive applied to the motor base does not flow to other portions.

In order to solve the above problems, the present invention has the following configuration as means.
That is, in a spindle motor in which a shaft having one end fixed to a hub on which a disk is mounted is rotatably fitted in a sleeve fixedly bonded to a through hole of a motor base, the motor having a wiring pattern and having a wiring pattern A base plate attached to a bottom surface of the base opposite to the hub; a recess portion provided at one side of the through hole so as to open the through hole at a position facing the substrate across the shaft on the bottom surface; And a conductive adhesive applied to the recess.

  According to the present invention, since the concave portion is provided at a position substantially opposite to the substrate across the shaft, even if the conductive adhesive flows for some reason, it does not reach the substrate, and the wiring pattern of the substrate is not changed. The effect that there is no short circuit is obtained.

Embodiments of the present invention will be described with reference to FIGS.
The spindle motor includes a rotor portion 21 and a stator portion 20, and the rotor portion 21 is rotatably supported by the stator portion 20 by the radial dynamic pressure bearing 10 and the thrust dynamic pressure bearing 11. Yes.
First, the structure will be described in the order of the stator portion, the rotor portion, the bearing portion, and the application of the conductive adhesive.

(1) About Stator Unit The stator unit 20 is composed of a motor base 1, a sleeve 6, and a core 13 around which a coil 12 is wound.
The motor base 1 is made of aluminum or an aluminum alloy, and a cylindrical wall 1A is erected at a substantially central portion thereof.
A 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.

Herringbon (fishbone) -like first and second dynamic pressure grooves 10a and 10b are respectively provided at two locations on the inner peripheral surface of the shaft hole 6E over the entire circumference. FIG. 1 schematically shows the first and second dynamic pressure grooves 10a and 10b.
Further, the inner diameter of the 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 first and second dynamic pressure grooves 10a and 10b. Is formed.

Further, the first wall 6A and the second wall 6B are formed in annular shapes having different diameters at the lower end (the side where the motor base 1 is inserted) of the shaft hole 6E. The lower end of the first seating surface 6C and the second seating surface 6D connected to the second wall 6B are opened stepwise (see FIG. 2).
A circular thrust plate 7 is fixed to the first wall portion 6 </ b> A 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.

(2) About the rotor portion The rotor portion 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 of an aluminum or aluminum alloy material in a substantially cylindrical shape having a shaft hole 5A, 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 portion of the shaft 2 (the opposite side press-fitted into the hub) by press-fitting.

  A signal recording / reproducing disk 22 is attached to 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 adhesion or caulking, respectively.

(3) Bearings (a) Radial bearings There is a slight gap between the shaft 2 and the shaft hole 6E of the sleeve 6, in which lubricating oil 17 that is a viscous fluid is filled and held.
Then, 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 push the shaft 2 from the outside toward the central axis. The radial dynamic pressure bearing 10 is obtained by generating the above.

(B) Thrust direction bearings Herringbon-like (not shown) dynamic pressure grooves are formed on the entire surface of the upper and lower surfaces of the flange 8 press-fitted and fixed to the lower end of the shaft 2.
Further, the thickness of the flange 8 is 10 to 20 μm thinner than the depth (axial direction) of the second wall portion 6B, and one thrust plate 7 is in close contact with the first seat 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.

Since this gap is filled and held with lubricating oil 17 which is a viscous fluid, dynamic pressure is generated by the dynamic pressure grooves on the upper surface and the lower surface of the flange 8 when the shaft 2 and the flange 8 rotate together. .
This 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 pressure in these two directions is balanced to provide the thrust dynamic pressure bearing 11 that holds the rotor portion 21 rotatably and stably in the axial direction.

  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. However, the dynamic pressure groove may be formed on the other opposing surface or on both surfaces. . The viscous fluid may be another fluid such as air.

Next, an assembling procedure of the main part having the configuration described in (1) to (3) will be described.
1. A flange 8 is press-fitted into the lower end portion of the shaft 2.
2. The shaft 2 is inserted into the shaft hole 6E of the sleeve 6 from its lower end.
3. The thrust plate 7 is fixed to the wall surface of the first wall portion 6 </ b> A of the sleeve 6 by press-fitting or an adhesive 16 and sealed.
4). The hub 5 is press-fitted into the upper end portion 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.

(4) Application of conductive adhesive As a path for effectively discharging static electricity generated on the signal 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. There is a first path to base 1.
In this embodiment, in addition to the first path, a second path reaching 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 cross-sectional view taken along the line AA in FIG.

FIG. 3 is a view showing the bottom surface 3 of the spindle motor as viewed from the lower side of FIG.
As shown in the figure, on the bottom surface 3, the conductive adhesive 18 is applied across 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 electrical connection with the outside is attached to the bottom surface 3 of the motor base 1 with an adhesive or the like (not shown).

A 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. The conductive adhesive 18 is applied to 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 disposed at a position recessed by a depth t2 from the bottom surface 3 of the motor base 1, and the bottom surface 4A and the bottom surface 7A have substantially the same depths t1 and t2. Is set.

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.
Further, the concave portion 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.

In the present embodiment, as the conductive adhesive 18, TB3380B manufactured by Three Bond Co., Ltd. can be used as an example.
The amount to be applied is 0.002 cc to 0.005 cc, but this amount can be set to an optimum amount as appropriate.
Further, the depth and size of the concave portion 4 (the area of the bottom portion 4A) also protrudes from the bottom surface 3 of the motor base 1 with respect to the height t when the conductive adhesive 18 is solidified according to the amount of application. It can be set not to.

As a result, a conductive path between the motor base 1 and the thrust plate 7 is secured, so that the static electricity generated in the disk 22 is conducted from the shaft 2, the flange 8 and the thrust plate 7 to the motor base 1 through the conductive adhesive 18. A road can be secured.
Moreover, according to the structure mentioned above, since the solidified conductive adhesive 18 does not protrude from the bottom surface 3 of the motor base 1, the height of the motor body can be reduced.

Even if the sleeve 6 and the motor base 1 are bonded by the non-conductive adhesive 16 to increase the insulation resistance, electrical conduction can be obtained between the thrust plate 7 and the motor base 1.
Further, since the conductive adhesive 18 is also applied to the sleeve 6 sandwiched between them, electrical connection 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.
Therefore, static electricity is discharged from the signal recording / reproducing disk 22 to the motor base 1 and the magnetic head is not damaged, and an error is not caused in recording / reproducing of the HDD, and the recorded signal is not damaged.

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 be a bottom surface 7A in which only a portion to which the conductive adhesive 18 is applied is recessed. Of course, it is desirable that the bottom surface 7 </ b> A, which is the recess, has the same depth as the bottom surface 4 </ b> A of the recess 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, and may be a spindle motor mounted on another device.

It is a half sectional view showing an example of a spindle motor of the present invention. It is a half sectional view showing the important section in the example of the spindle motor of the present invention. It is a bottom view which shows the principal part in the Example of the spindle motor of this invention. It is a half sectional view explaining a conventional spindle motor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,101 Motor base 1A Cylindrical wall 1B Sleeve hole 2,102 Shaft 3 Bottom surface (of motor base) 4 Recess 4A Bottom surface (application surface)
5,105 (rotor) hub 5A 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 (coating surface)
8 Flange 9 Flexible printed circuit board (FPC)
DESCRIPTION OF SYMBOLS 10,110 Radial dynamic pressure bearing 10a, 10b Dynamic pressure groove 11, 111 Thrust dynamic pressure bearing 12 Coil 13 Core 14 Magnet 15 Rotor yoke 16, 116 Nonconductive adhesive 17 Lubricating oil 18 Conductive adhesive 19 Wiring pattern 20 Stator part 21 Rotor 22 Signal recording / reproducing disc t Height t1, t2 Depth t3 Thickness W Width

Claims (5)

In a spindle motor in which a shaft having one end fixed to a hub on which a disk is mounted is rotatably inserted into a sleeve fixedly bonded to a through hole of a motor base.
A board having a wiring pattern and attached to a bottom surface opposite to the hub in the motor base;
A groove-like recess that extends outward in the radial direction of the through hole and has one end opened to the through hole at a position facing the substrate across the shaft on the bottom surface;
A spindle motor comprising: a conductive adhesive applied to the recess. In a spindle motor in which a shaft having one end fixed to a hub on which a disk is mounted is rotatably inserted into a sleeve fixedly bonded to a through hole of a motor base.
A board having a wiring pattern and attached to a bottom surface opposite to the hub in the motor base;
A recess provided at one end of the through hole at a position facing the substrate across the shaft on the bottom surface;
A thrust plate fixed to the lower end of the sleeve, and a conductive adhesive applied to the recess,
The spindle motor according to claim 1, wherein the conductive adhesive is applied across the thrust plate and the motor base in a radial direction so as to sandwich the sleeve therebetween. The spindle motor according to claim 2, wherein the concave portion is provided in a groove shape extending outward in the radial direction of the through hole and having one end opened to the through hole. The recess has a bottom surface that is a plane,
4. The spindle motor according to claim 2, wherein a depth to the bottom surface of the recess and a depth to the bottom surface of the thrust plate are set to be the same with respect to the bottom surface of the motor base. 5. . The depth of the recess is set so as not to protrude from the bottom surface of the motor base with respect to the height of the adhesive when the conductive adhesive is solidified. Item 5. The spindle motor according to any one of Items 4 to 4.

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