JPH0736251B2 - Spindle motor for disk - Google Patents

Description

The present invention relates to a disk spindle motor for rotating a magnetic disk.

[Conventional technology and its problems]

In the conventional motor of this type, parts to be attached to the bracket having the bearing support boss portion and the flange portion, and
Depending on the positional relationship with other members corresponding to the vicinity of the bracket, a cutout portion or a thick portion may be provided in the flange portion. In this case, at the time of thermal expansion of the bracket, partial distortion occurs in a predetermined portion of the bracket, that is, uneven distortion with respect to the center of the shaft portion, which causes tilting of the rotating shaft, which causes information on the track on the magnetic disk by the magnetic head There was a malfunction in writing / reading (misalignment, off-track, etc.). As a countermeasure against this, a "leaf spring side pressure system" is used in which a leaf spring presses one outer peripheral surface of the rotary shaft in order to push the rotary shaft in the direction opposite to the above-mentioned tilt, or an eccentric groove is formed. The "O-ring side pressure system" in which an O-ring was fitted into this was adopted. However, these methods are not sufficient to correct the tilt of the rotating shaft caused by the distortion of the bracket due to the above reasons.

An object of the present invention is to solve the above-mentioned problems and to provide a disk spindle motor capable of stable writing / reading with respect to temperature changes.

[Means for solving problems]

The present invention provides a bracket including a bearing support boss portion and a flange portion, a rotary shaft that is rotatably supported by the bearing support boss portion, and a hub that is fixed to an end portion of the rotary shaft and is used to mount a disc. The bracket is provided with any one of a cutout portion, a concave portion and a thick portion for a component mounted on the bracket or fixed to another member, and the cutout portion, the concave portion and the thick portion. One of the meat parts is
In a spindle motor for a disk, wherein a corresponding portion of each of the brackets forms a strain generating portion when the bracket thermally expands, and the hub is tilted in a predetermined direction due to the partial strain; A distortion compensating portion is provided which substantially cancels out partial distortion of the generating portion and eliminates tilting of the hub. It is preferable that the distortion compensating portion is formed of one of a rib, a groove, a cutout portion, an uneven thickness portion, or a combination thereof. Further, as the distortion compensating portion, a dissimilar metal member having a coefficient of thermal expansion different from that of the material of the bracket may be fixed to a predetermined position of the flange portion.

[Action]

When the bracket thermally expands, due to the presence of strain
The bracket is partially distorted. This partial distortion is
Stress is generated in the bracket, which tends to tilt the rotary shaft, which is rotatably supported by the bearing support, and thus the hub. However, the strain compensating portion provided on the bracket is provided so as not to generate the stress of the strain generating portion, that is, to substantially cancel the partial strain of the strain generating portion. Therefore, the hub does not tilt, so that a disk spindle motor capable of stable writing / reading with respect to temperature changes can be obtained. The distortion compensating section may employ one or a combination of ribs, grooves, notches, and uneven thickness sections corresponding to the distortion generating section, which facilitates construction. You can Also,
The strain compensating portion can be easily constructed by fixing a dissimilar metal member having a coefficient of thermal expansion different from that of the bracket material to the flange portion.

〔Example〕

 Embodiments of the present invention will be described in detail with reference to the drawings.

In FIGS. 1, 2 and 3, reference numeral 1 denotes a disk spindle motor according to the present invention, which integrally includes a bearing support boss portion 2 and a flange portion 3 and which is made of aluminum or the like. A bracket 4 made of a magnetic material, a rotary shaft 7 rotatably supported by the boss portion 2 of the bracket 4 via bearings 5 and 6, and a rotor holder 8 fixed to one end of the rotary shaft 7.
And a stator 10 fixed to the bearing support boss portion 2 of the bracket 4 and having a coil 9 wound around it.
A magnetic disk mounting hub 12 for mounting the magnetic disks 11 is fixed to the upper end of the rotary shaft 7. Reference numeral 13 denotes an access arm, and 14 denotes a magnetic head attached to the tip of the access arm 13 for writing / reading information to / from the magnetic disk 11. The access arms 13 ... Can be moved back and forth in the directions of arrows A and B. A rotor magnet 15 is fixed to the rotor holder 8 so as to correspond to the outer peripheral side of the stator 10. The rotational position of the rotor magnet 15 is detected by a rotor position detector 16 including a Hall element, a Hall IC and the like. , The coil 9 of the stator 10 based on the rotational position detection signal from the detector 16.
The energization of the spindle motor is switched and controlled, and the spindle motor rotates. Reference numeral 17 denotes a magnetic fluid seal attached to the upper end of the bearing support boss portion 2. When the rotating shaft 7 rotates, fine dust or dirt in the air enters the mounting side of the magnetic disk 11, or the bearing 5,
Prevents grease, etc. from entering the magnetic disk mounting side in a mist form. A magnetic shield thin plate 19 is attached to the surface 3a of the flange portion 3 of the bracket 4 to effectively block the influence of the magnetic field in the vicinity of the magnetic head 14. Back side of flange 3
A printed circuit board 23 having various electronic components is attached to 3b, and 24 ... Lead lines from the circuit board 23. Reference numeral 20 indicated by an imaginary line is a device body, and the entire spindle motor 1 is attached via the flange portion 3 of the bracket 4.

Reference numeral 34 is an annular projecting portion attached to the back surface 3b of the flange portion 3, and 35 is a projecting small piece portion for mounting the detector.

The portion 21 shown in FIG. 2 is one of the strain generating portions in the flange portion 3.

In this case, the strain generating portion 21 corresponds to the cutout portion 22 provided in the flange portion 3.

The distortion generating part 21 is, like the cutout part 22, the bracket 4
Is provided for the following reasons. That is, the components 25 such as the printed circuit board 23 and the lead wires 24 attached to the bracket 4 are mounted on the bracket 4. Again, for convenience of mounting the component 25, the notch 22 and the like are provided on the bracket 4.
Further, since the bracket 4 is attached to the other member 26 such as the device body 20, the notch 22 and the like are provided in the bracket 4 for the convenience of the attachment.

The cutout portion 22 is restricted by the shape of the related portion of the device body 20 which is the other member 26, and a part of a circular shape which constitutes the planar shape of the flange portion 3 as shown by an imaginary line is a chord of a predetermined length. Shown is the case of a roughly crescent-shaped slice.

Reference numeral 27 denotes a strain compensating portion such as a rib, a groove portion, a notch portion, an uneven thickness portion, etc., which is provided at a position approximately symmetrical to the shaft center C of the strain generating portion 21 of the flange portion 3. In the illustrated example, the distortion compensation unit
The case of the groove 28 is shown as 27.

When the motor 1 is heated during operation due to the presence of the strain generating portion 21, a change in internal stress occurs due to thermal expansion of the flange portion 3 in one direction with respect to the shaft center C in the flange portion 3 of the bracket 4, and the flange Partial distortion is generated in the part 3. Due to this, as shown in FIG. 7, the bearing support boss portion 2 and the rotary shaft 7 fall in a certain direction. Due to the tilting of the rotary shaft 7 at this time, the magnetic disks 11 mounted on the magnetic disk mounting hub 12 are inclined at a predetermined minute angle, and the distance from the magnetic heads 14 to the shaft center C changes. A malfunction such as an error or off-track occurs. By forming the groove portion 28 as the strain compensating portion 27, the partial strain is substantially canceled by the influence of the strain generating portion 21. That is, the presence of the strain generating portion 21 causes a change in the internal stress in the constant direction with respect to the shaft center C in the flange portion 3 and a partial strain associated therewith, but by providing the strain compensating portion 27, At the time of thermal expansion, the flange portion 3 is in the opposite direction to the center C of the shaft portion, and at the same time, the same amount of change in internal stress and partial strain are simultaneously generated. The amount of synthetic distortion becomes zero. In the case of the embodiment shown in FIGS. 1 and 2, the strain compensating portion 27 has the same shape as the strain generating portion 21 consisting of the above-mentioned cutout portion 22 and is arranged at a completely symmetrical position with respect to the shaft center C. The notch 33 (see FIG. 4) is ideal, but it is often difficult to have a completely symmetrical position and the same shape due to various restrictions such as design.
With respect to the area of the groove 28, the arrangement is set as described above, a suitable number of brackets 4 having the same shape are prototyped, and the groove 28 having a different area is formed in each of them, and a strain experiment is performed for each. . Based on such experimental results, the optimum area is selected when the combined strain amount at the shaft center C is substantially zero or the minimum. In this case, the groove 28 is rectangular, but may have another shape. Further, although the optimum shape can be obtained by experiments, the number of times of the above experiments will be considerably increased.

The inclination of the magnetic disks 11 ...
As shown in FIG. 8, the forward / backward direction A of the magnetic head 14 ...
If it occurs in the direction perpendicular to B, the magnetic head 1
There is almost no support for the reading operation of 4 ... Therefore,
As shown in FIG. 2 and FIG. 5, the strain generator 21 is used to take out the lead wires 24 ...
In the case of the notch formed for attaching the component 25 to the bracket 4, the distortion compensating portion 27 can be omitted because it is a direction perpendicular to the advancing / retreating directions A and B, but of course, it is a virtual line. It is also preferable to form a notch 30 having a symmetrical position and the same shape with respect to the shaft center C as shown in FIG. Incidentally, reference numeral 36 is a holding metal fitting attached to the substrate 23.

FIG. 6 shows the strain generating portion 21 including the thick portion 31 on the flange portion 3.
And the rib 32a or the uneven thickness portion 32b is provided as the strain compensating portion 27 at a position substantially symmetrical to the center C of the shaft portion of the strain generating portion 21. Then, in FIG. 9 or FIG. 10, the flange portion 3 of the bracket 4 has a strain generating portion 21 formed of a concave portion,
The distortion compensator 27 that substantially cancels this is provided by the bracket 4
It is constituted by fixing a dissimilar metal member 45 having a different thermal expansion coefficient to that of the above-mentioned material at a predetermined position of the flange portion 3. Desirably,
The dissimilar metal member 45 is also used as a lead wire clamp metal fitting or another component fixing metal fitting.

Then, which side of the thermal expansion coefficients of the dissimilar metal member 45 and the flange portion 3 is set to be larger is determined by the shape and size of the strain generating portion 21 formed of the concave portion.
In FIG. 9, when the strain generating portion 21 formed of a concave portion shrinks at the time of temperature rise or the expansion is smaller than other portions of the flange portion 3, the coefficient of thermal expansion of the dissimilar metal member 45 is increased. Set it, and in the opposite case, set it to small. Then, in FIG. 10, the setting may be performed in the opposite manner to that in FIG.

Further, in the illustrated embodiment, the strain generating portion 21 is shown to be caused by the geometrical shape and dimensions of the notch, the recess, the thick portion, etc. The strain compensating unit 27 having the same configuration as described above substantially cancels the strain, including the case where it is generated by each influence of the internal stress caused by heating and the internal stress caused by a mechanical cause.

Although not shown, the same can be applied to the case where the distortion generating portion 21 exists in the boss portion 2. Furthermore, the distortion compensation unit 27 ...
It is also free to provide a plurality of.

In the present invention, offsetting the strain includes both absorbing the strain and offsetting the generation.

Therefore, in the present invention, as means for preventing the rotating shaft 7 and the magnetic disk 11 from falling, (i) a structure that absorbs strain, and (ii) cancellation of intentionally generating strain on the opposite side. It includes two major embodiments of the structure.

〔The invention's effect〕

As described above, in the present invention, the strain compensating portion 27 is provided at a position approximately symmetrical to the shaft center C of the strain generating portion 21 of the flange portion 3 of the bracket 4, so that the internal stress due to the influence of both of them during thermal expansion can be reduced. The change, that is, the partial strain can be made to have the same amount in the opposite direction with respect to the shaft center C, and the combined strain amount of the strain compensating unit 27 and the strain generating unit 21 at the shaft center C can be changed. It can be approximately zero. Therefore,
It is possible to effectively prevent an erroneous operation such as off-track from writing / reading information to / from a track on the magnetic disk 11 ... Without causing a problem such as tilting of the magnetic disk 11. it can.

Conventionally, the rotation shaft 7 collapses due to the thermal expansion of the bracket 4,
In order to prevent the magnetic disks 11 from tilting, the leaf spring side pressure method and the O-ring side pressure method that have been employed were not sufficient to correct the tilt, but the present invention sufficiently compensates for this. .

[Brief description of drawings]

FIG. 1 is an enlarged sectional view showing an embodiment of the present invention with a magnetic disk attached, FIG. 2 is an enlarged sectional view taken along line II-II of FIG. 1, and FIG. 3 is taken along line III-III of FIG. Sectional view, FIG. 4 is a plan view showing another specific example of the distortion compensating section, FIG. 5 is a sectional view taken along line VV of FIG. 2, and FIG. 6 is a sectional view showing still another specific example of the distortion compensating section. FIG. 8 is a side view, FIG. 7 is an explanatory view of a phenomenon in which a bracket having a distortion generating portion causes uneven strain during thermal expansion, which causes malfunction of the magnetic head.
FIG. 9 is an explanatory view showing that a reading error does not occur even if the magnetic disk tilts, if it occurs in a direction orthogonal to the advancing / retreating direction of the magnetic head, and FIGS. 9 and 10 show other embodiments. FIG. 2 ... Bearing support boss part, 3 ... Flange part, 4 ... Bracket, 7 ... Rotating shaft, 21 ... Essential strain generating part, 25 ...
… Parts, 26 …… Other members, 27 …… Strain compensation part, 45 …… Dissimilar metal members.

Claims (6)

[Claims] 1. A bracket 4 comprising a bearing support boss portion 2 and a flange portion 3, a rotary shaft 7 rotatably supported by the bearing support boss portion 2, and a disk fixed to an end portion of the rotary shaft 7. And a hub 12 for mounting 11. The bracket 4 is provided with a notch, a recess and a thick portion for a component 25 mounted on the bracket 4 or for being fixed to another member 26. Any one of the cutout portion, the concave portion, and the thick portion constitutes a strain generating portion 21 in which a corresponding portion at the time of thermal expansion of the bracket 4 generates a partial strain. In a spindle motor for a disk, in which the hub 12 is tilted in a predetermined direction, the bracket 4 has a distortion compensating portion 27 that substantially cancels out partial distortion of the distortion generating portion 21 and eliminates the tilting of the hub 12. Is provided And a disk spindle motor, characterized in that. 2. The spindle motor for a disk according to claim 1, wherein the distortion compensator 27 comprises one of a rib, a groove, a notch, an uneven thickness portion or a combination thereof. 3. The strain compensating portion 27 is composed of a dissimilar metal member 45 fixed to a predetermined position of the flange portion 3 and having a coefficient of thermal expansion different from that of the material of the bracket 4, according to claim 1. Disk spindle motor. 4. A bracket 4 comprising a bearing support boss portion 2 and a flange portion 3, a rotary shaft 7 rotatably supported by the bearing support boss portion 2, and a disk fixed to an end portion of the rotary shaft 7. The bracket 4 has a hub 12 to which the hub 11 is attached, and the bracket 4 has a strain generating portion 21 that generates an internal stress at the time of thermal expansion. In the spindle motor for a disk tilted in a direction, the bracket 4 is provided with a distortion compensator 27 that substantially cancels the internal stress of the distortion generator 21 and eliminates the tilt of the hub 12. Spindle motor for disk characterized by. 5. The spindle motor for a disk according to claim 4, wherein the distortion compensator 27 comprises one of a rib, a groove, a notch, an uneven thickness portion or a combination thereof. 6. The distortion compensating portion 27 is composed of a dissimilar metal member 45 fixed to a predetermined position of the flange portion 3 and having a coefficient of thermal expansion different from that of the material of the bracket 4, according to claim 4. Disk spindle motor.