JPS63257429A - Spindle motor for disk drive - Google Patents

Abstract

PURPOSE:To materialize highly precise rotation, by interposing non-solidifying adhesive into the clearance of an engaged section where the thermal expansional difference is produced. CONSTITUTION:Non-solidifying adhesive Q is interposed to the clearance of engaged section 12 of an outer ring 4c of a lower bearing 4 with an inside circumferential surface of a cylinder boss section 2. This non-solidifying adhesive Q is the rubber or plastic, etc., adhesive having elasticity after it is hardened. In the engaged section 12 of the outside circumferential surface of a shield 9 with an inside circumferential surface of a hub 7, the non-solidifying adhesive Q is interposed at the upper end edge and lower end edge. The intermediate region other than this upper and lower end edges has a small cavity.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a disk spindle motor.

C. Prior art and its problems] Conventional spindle motors have had the following problems due to differences in the materials of their constituent parts. That is,
The materials of the bearings, shafts, plackets, hubs, and magnetic shields that make up the spindle motor have different coefficients of thermal expansion, resulting in dimensional differences between the components during use. In conventional structures where each fitting part is simply coated with a hardening adhesive and bonded, or by fitting methods such as press-fitting and shrink-fitting, the bimetal effect causes large distortions in shape and dimensions. occurred. More specifically, the gap between the hole of the bracket, which is generally made of aluminum die-casting, and the fitting part of the steel bearing changes due to the temperature change. If an adhesive that completely solidifies after curing is used, the bimetallic action may distort the bearing, change the preload, or cause the theoretical center of rotation to shift, resulting in the so-called ``shaft tilting''. ” occurred. Such a phenomenon also occurs between two bearings, and in extreme cases, the preload becomes inadequate, damaging the bearing or causing rotational vibration.

In addition, distortion due to such bimetallic action also occurs between the aluminum die-cast hub and the magnetic shield adhered (completely solidified) to its inner peripheral surface, causing a shift in the theoretical center position of the disk. There was an inclination.

The tilting of the shaft and the misalignment of the center of the disk cause what is called an off-track phenomenon of the magnetic disk. An object of the present invention is to provide a disk spindle motor that solves the above problems.

[Means for solving problems]

In the present invention, a non-hardening adhesive is interposed in the gap between the fitting parts where a difference in thermal expansion occurs.

[Effect]

Even if the two members in the mating part are dissimilar metals with a difference in thermal expansion, they are elastically connected by the non-hardening adhesive between the two members, so the distortion caused by the thermal expansion is absorbed. As a result, internal stress due to heat is also reduced.

〔Example〕

In Fig. 1, reference numeral 1 denotes an aluminum die-cast bracket, and a pair of bearings 3 are attached to the inner peripheral surface of the cylindrical boss portion 2.
．． 4 are fitted and held, and a rotating shaft 5 is rotatably supported at the center via both bearings 3.4. Note that 6 is a stator, which is fixed to the outer circumferential surface of the cylindrical boss portion 2.

7 is an aluminum die-cast hub fixed to one end of the rotating shaft 5, and a magnetic recording disk 8 is attached to this hub 7.
Equipped with The hub 7 is approximately in the shape of an inverted spatula, and has a magnetic shielding material 9 fitted therein and a permanent magnet 10 fitted inside it.

1, 2, and 3, the outer ring 4a of the lower bearing 4 and the inner circumferential surface 1 of the cylindrical boss portion 2.
A non-hardening adhesive Q is interposed in the gap between the fitting part 12 and the fitting part 12. This non-hardening adhesive Q is Sony's "Sony Bond 5CI08 J" and Three Bond's r30X.
220J etc. can be used. In other words, it is a rubber-based or plastic-based adhesive that remains elastic even after curing. In FIG. 3, a recess 13 of minute depth is formed at a predetermined position and with a predetermined center angle θ on the inner circumferential surface 11 of the cylindrical boss portion 2 during die-casting or by subsequent machining. A minute gap is particularly formed in the range of the central angle θ by this recess 13, and the non-hardening adhesive Q is interposed therein (by coating).

In FIG. 2, the thickness of the adhesive Q and the depth of the recess 13 are shown as follows.
In particular, it is extremely large.

The above-mentioned center angle θ is set to 45° to 180′. Particularly desirable is between 80'' and 100°.

The inner ring and outer ring of the upper bearing 3 are fixed to the shaft 5 and the inner circumferential surface 11, respectively, but in the lower bearing 4, only the inner ring 4b is fixed to the shaft 5, and the outer ring 4a is in a movable state (loose) at the boss portion. 2, and the elasticity of the non-hardening adhesive Q over the predetermined center angle θ acts effectively.

Therefore, the angle β formed between the center position of the non-hardening adhesive Q, that is, the (1/2xθ) position, and the position A in the moving direction of the magnetic head 14 is set to about 90°. That is, a phase difference of approximately 90° is provided between the internal stress absorption direction B in which internal stress due to thermal expansion is absorbed by the non-hardening adhesive Q and the forward/backward direction A of the magnetic head 14.

The reason for this is that if relative thermal strain and internal stress are not generated between the steel bearing 4 and the boss portion 2 of the aluminum die-cast bracket 1 due to temperature changes, the non-hardening adhesive Q Strain and stress are concentrated in a certain internal stress absorption direction B.
The stress is absorbed, and the axis of the rotating shaft 5 is slightly tilted in the direction of arrow B.

However, even if such a shaft inclination occurs, the amount of off-track due to the relative positional deviation in the radial direction between the track drawn on the disk 8 and the magnetic head 14 that reads it is the smallest at βζ90. This is the case.

Furthermore, as shown in FIG. 1, a non-hardening adhesive Q is also applied to the upper and lower edges of the fitting portion 12 between the outer circumferential surface of the shield material 9 and the inner circumferential surface of the hub 7. . An intermediate portion other than the upper edge and the lower edge has a slight gap.

Next, FIG. 4 shows another embodiment, in which a fixed shaft 15 is erected on the bracket 1, and bearings 16 are fixed on both the inner and outer rings.
The hub 7 is rotatably supported by a bearing 17 in which only the inner ring 17a is movable (loose) in the axial direction and the outer ring 17b is fixed to the inner peripheral surface of the hub 7.

18 is a preload elastic member such as a disc spring, and the inner ring 17a is
The force is applied downward in the figure. Stator 6 is fixed shaft 1
The permanent magnet 10 is fixed to the hub 7 at a vertically intermediate position corresponding to the rotor magnet IO.

Then, the non-hardening adhesive Q is applied to the gap of the fitting portion 12 between the loose inner ring 17a and the shaft 15 at a predetermined center angle θ and a relative center angle β with respect to the predetermined magnetic head 14, as described above. (See Figure 3 along with Figure 4).
(see figure). The reason why the off-track phenomenon is effectively prevented is the same as in the previous embodiment.

Above, in any case, 2f[Ii1 or higher bearing 3
゜4: A non-hardening adhesive Q having elasticity even after hardening is interposed between the outer ring and the inner peripheral surface of the hole or the inner ring and the shaft of at least one of the hair rings of 16 and 17. And, 360
``The adhesive Q is interposed only in a specific range of a predetermined angle θ instead of covering the entire circumference. And magnetic herad 1
4 is set at a substantially right angle to prevent off-track. Note that Fig. 5 shows an in-hub spindle motor that is almost the same as Fig. 4, but with non-hardening adhesive Q.
The case is shown in which the intervening location is between the aluminum die-cast hub 7 and the magnetic shielding material 9 made of steel or the like.

More specifically, the inner circumferential surface of the hub 7 and the substantially cylindrical magnetic shielding material 9 are in a non-contact state with a gap 20 in the middle, and only the upper and lower ends are connected over the entire 360° circumference.
They are fitted together via a non-hardening adhesive Q.

FIG. 6 schematically shows a cross section of this fitting portion 12, and it can be seen that the non-hardening adhesive Q is interposed over the entire circumference.

In the embodiments shown in FIGS. 5 and 6, it is assumed that relative thermal strain is not generated in the axial direction and the radial direction between the hub 7 and the magnetic shielding material 9, which have different coefficients of thermal expansion. However, non-setting adhesive Q all around the circumference.

Q absorbs this thermal distortion, effectively preventing problems such as the external shape of the hub 7 changing like a bimetal, making it impossible to remove the magnetic disk.

It is also desirable to use this embodiment together with the embodiment shown in FIG.

Further, as shown in FIG. 7, it is preferable that the recess 13 of the cylindrical boss portion 2 is formed in an arc shape with θ≦180°, and the distance between the recess and the bearing is gradually increased or decreased.

Furthermore, as shown in FIG. 8, the recesses 13...
It is also free to provide it in one or more locations.

In the present invention, the term "non-hardening adhesive J" refers to an adhesive that retains elasticity even after the chemical reaction is completed after application.

〔Effect of the invention〕

The present invention achieves the following remarkable effects with the above-described configuration.

■ Prevents off-track phenomenon and achieves high-precision rotation.

(2) In particular, thermal distortion caused by temperature changes can be effectively absorbed by the non-hardening adhesive Q.

■ Prevents bearing damage and extends life.

(2) In the fitting part 12, mechanical distortion during assembly of parts can be absorbed, or the mechanical distortion can be suppressed only in a harmless direction, thereby improving the rotation accuracy of the motor.

■ Non-hardening adhesive Q suppresses minute vibrations generated from the motor.
It is absorbed by the interposed fitting part I2, and quiet rotation is obtained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, FIG. 2 is an enlarged perspective view of the main part thereof, FIG. 3 is a simplified plan view, and FIG. FIG. 5 is a sectional view of another specific example, FIG. 6 is a simplified cross-sectional view of the main part thereof, and FIGS. 7 and 8 are simplified sectional views showing modified examples. Q: Non-hardening adhesive, 12: Fitting portion.

Claims (1)

[Claims] 1. A disk spindle motor characterized in that a non-hardening adhesive Q is interposed in the gap between the fitting portions 12 where a difference in thermal expansion occurs.