JPH06165427A - Spindle motor for disc - Google Patents

Abstract

PURPOSE:To suppress the center runout and the face runout of a hub stage effectively with simple constitution by providing a cut hole at one part on the rotation truck of a yoke plate to which the end face of rotor magnet is opposed. CONSTITUTION:A rotor magnet 4 being magnetized in multipole in diametrical direction is held at the inside periphery of a rotor case 5 by adhesion or the like, and the inside periphery is opposed a specified interval part to the outside periphery of a stator core 2, and the lower end face is opposed a specified interval apart to a yoke plate 3. On the other hand, a slot-shaped cut hole 20 is provided at one part on the truck of the rotation of the yoke plate 3 to which the end face of the rotor magnet 4 is opposed, and since there is no magnetic substance at the section of the cut hole 20, the magnetic resistance becomes large there, so it follows that the magnetic attraction decreases. As a result, the rotation of the rotor case is inclined compulsorily, and a rotary shaft 12 inclines by the amount of a clearance to a bearing, and clearance between both ceases to exist, so runout can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk spindle motor for rotationally driving a disk, and more particularly to a suppressing means for suppressing vibration of a hub base for mounting a disk.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional disk spindle motor, in which an inner peripheral portion of a stator core 2 having a drive coil 1 wound around salient poles is fitted to an outer periphery of a central cylindrical portion of a holder 8. In addition, it is supported while being placed on the upper surface of the collar portion 8a. A yoke plate 3 made of a magnetic material such as an iron plate is arranged on the lower surface of the collar portion 8a of the housing 8.
The yoke plate 3 is screwed and fixed to the stator core 2 with a screw 9 through the through hole 8b of the flange 8a.

Further, an oil-impregnated metal bearing 10 is fitted in the center hole of the central cylindrical portion of the housing 8 in the lower part of the figure, and an outer ring of a ball bearing 11 is press-fitted in the upper part. These bearings are arranged side by side in the axial direction, and the rotary shaft 12 is rotatably supported by the cooperation of both. The rotating shaft 12
A hub base 13 for rotating and driving a floppy disk (not shown) is fitted to the upper end of the hub base 13, and a rotor case 5 formed in a substantially dish shape is attached to the hub base 13.
On the inner surface of the rotor case 5 on the outer peripheral side, a rotor magnet 4 which is magnetized in multiple radial directions is held by adhesion or the like.
The inner peripheral surface of the rotor magnet 4 faces the outer peripheral surface of the stator core 2 at a predetermined interval, and
The lower end surface of the rotor magnet 4 is opposed to the yoke plate 3.

However, in a normal state, as shown in FIG. 5, the inner diameter d1 of the metal bearing 10 and the inner diameter d2 of the inner ring of the ball bearing 11 are equal to the diameter d0 of the rotating shaft 1.
It is set to be slightly larger so that the insertion of 2 is allowed. Therefore, when the rotary shaft 12 is supported by both bearings, a radial clearance (play) occurs. Due to this clearance, when the spindle motor is driven to bring the rotor case 5 into a rotating state, the rotation shaft 12
Causes radial runout, and the hub base 13 attached to the rotor case 5 causes vertical runout.

When a floppy disk or the like (not shown) is rotationally driven in a state where such a shake phenomenon occurs, it becomes a cause of causing an error as a matter of course that high-density recording cannot be performed. Therefore, it is necessary to suppress the core runout and the surface runout, and therefore, both the bearings 10 and 11
Various means for regulating the radial clearance between the rotating shaft 12 and the rotary shaft 12 have been proposed and put into practical use.

The first means is to improve the accuracy of both the bearings 10 and 11 and the rotary shaft 12. In other words, the precision of the inner diameter d1 of the metal bearing 10 and the inner diameter d2 of the inner ring of the ball bearing 11 and the diameter d0 of the rotary shaft 12 are made to be as close as possible to each other. As a result, the clearance in the radial direction is reduced, and the shake is suppressed. However, in order to perform high-precision machining as described above, there is a limit in the part machining capacity, and in addition, there is a practical problem that cost is inevitably increased by performing high-precision machining on each part. Have.

Further, even if both of them have high precision, when the inner diameter d1 of the metal bearing 10 and the inner diameter d2 of the inner ring of the ball bearing 11 are too small with respect to the diameter d0 of the rotary shaft 12, or the appropriate clearance is too small, or As shown in FIG. 6, if the centers of both bearings do not coincide with each other and have a gap g, twisting may occur during the assembly process, which may prevent smooth assembly. In this way, if the rotary shaft 12 is inserted with the twisted state, an unreasonable force acts on the ball bearing 11 and damages the ball and the ball rolling surface. Become. Further, also in the case of the metal bearing 10, the bearing surface is similarly scratched, and a defective phenomenon such as bearing wear occurs.

The second means is to bond and fix the inner ring of the ball bearing 11 and the rotary shaft 12 to each other. That is,
Since the diameter d0 of the rotary shaft 12 and the inner diameter d2 of the inner ring of the ball bearing 11 are fixed by an adhesive, the clearance is eliminated. However, since there is a clearance between the inner diameter d1 of the metal bearing 10 and the diameter d0 of the rotary shaft 12, there is a problem that the shake is reduced but not suppressed.

Further, when the inner ring of the ball bearing 11 and the rotary shaft 12 are bonded together, the adhesive agent is used for the ball bearing 1.
In some cases, the adhesive may get inside and the adhesive should be managed very carefully. Further, if correction is required, it is necessary to remove the rotary shaft 12, but if the inner ring of the ball bearing 11 and the rotary shaft 12 are bonded, it is extremely difficult to remove, and even if removed, the surrounding parts A complicated process is required, such as the need to destroy the.

FIG. 7 shows a pair of upper and lower ball bearings 11,
Although the rotating shaft 12 is supported by 14, even in this case, the inner ring and the rotating shaft 12 are bonded to each other in order to eliminate the clearance.
The problem of entering the inside of the device and the problem that it becomes difficult to remove the rotary shaft 12 substantially are the same as in the case of the above-mentioned means. When the rotating shaft 12 is supported by one metal bearing 15 as a bearing as shown in FIG. 8, between the inner diameter d1 of the metal bearing 15 and the diameter d0 of the rotating shaft 12 as in the first example. Since there is a clearance at the end, the runout is not suppressed.

As a third means, as shown in FIG. 9, a part of the salient poles 2a of the stator core 2 is removed so that the stator core 2
That is, the rotating shaft 12 is biased in one direction by breaking the magnetic attraction balance of the rotor magnet 4 facing the outer peripheral surface of the rotor at a predetermined interval. That is, three of the salient poles 2 on the left side of the drawing are cut off with the center line O of the stator core 2 as a boundary. Therefore, the rotor magnet 4 facing the outer peripheral surface of the stator core 2 has a weaker magnetic attraction force to the left side in the drawing in which the salient poles 2 are omitted.
It will be biased in the direction of the arrow. Since the rotating shaft 12 is integrally formed with the rotor magnet 4, it is biased to the left side at the same time and is rotatably supported by one of the ball bearing 11 and the metal bearing 10 in a pressed state. Therefore, since the clearance at this portion is eliminated, the runout is relatively reduced.

However, when a part of the salient poles 2a of the stator core 2 is omitted, the magnetic attraction balance with the rotor magnet 4 is lost, so that cogging becomes large.
Since the vibration during rotation and the non-uniform speed rotation component become large, a problem arises in practical use.

As shown in FIG. 10, the fourth means is to dispose a magnet 16 for magnetic attraction between the salient poles 2a of a part of the stator core 2, and to attract the rotor case 5 by this magnet 16. Then, as shown in FIG. 11, the rotation of the rotor case 5 is forcibly inclined. That is, since the magnet 16 for attraction is disposed on the left end side of the stator core 2 and faces the rotor case 5,
The rotor case 5 is always attracted to the magnet 16. As a result, the rotary shaft 12 is exaggerated in FIG.
Since the inner diameter d1 of the metal bearing 10 and the inner diameter d2 of the inner ring of the ball bearing 11 are inclined by the clearance, the clearance between them is eliminated, so that the above-described runout can be suppressed.

However, in this means, it is necessary to dispose the magnet 16 for attraction separately, and there is a problem that the cost including the work for mounting the magnet 16 becomes high. Further, if the magnetic force of the magnet 16 is too strong, it may have a magnetic effect on the stator that urges the rotor magnet 4 to rotate, which may cause a hindrance to the rotation performance. Further, since a space for disposing the magnet 16 is required, it cannot be mounted on a small motor.

[0015]

The above-mentioned conventional disk spindle motor has the first structure in order to suppress the occurrence of runout due to the radial clearance between the bearing and the rotary shaft.
Through the measures, the fourth means is appropriately selected. However, in the first means, there is a problem that component processing capability is required and cost is increased in order to improve the accuracy of both the bearing and the rotary shaft. In the second means, since the bearing and the rotary shaft are adhesively fixed, there is a problem that the adhesive may have a bad influence and the subsequent disassembly becomes substantially impossible. In the third means, since a part of the salient poles of the stator core is omitted, there is a problem that vibration such as cogging and non-constant speed rotation component become large. Further, in the fourth means, there are various problems in any means, such as an increase in cost due to the arrangement of the magnet for magnetic attraction, and other magnetic influences.

The present invention has been made in order to solve such a problem, and requires no special processing, addition of parts, adhesion, etc., and the center runout and surface of the hub base can be effectively achieved by a simple structure. An object of the present invention is to provide a disk spindle motor capable of suppressing shake.

[0017]

According to the present invention, there is provided a bearing for rotatably supporting a rotary shaft, a yoke plate having a holder for holding the bearing, a stator core supported by the holder, and the rotary shaft. A rotor case fixedly mounted on a hub base for mounting a disk on the center side, and a rotor magnet held by the rotor case and having an inner peripheral surface facing the stator core and an end surface facing the yoke plate. And a cutout hole is provided in a part on the rotation locus of the yoke plate where the end faces of the rotor magnet face each other.

[0018]

When a cutout hole is provided in a part of the rotation locus of the yoke plate where the end faces of the rotor magnet face each other, the attraction force of the rotor magnet magnetically attracted to the yoke plate becomes asymmetric, which results in The rotary shaft is inclined by the clearance with the bearing, and the clearance between the two is lost. For this reason, the rotary shaft rotates in a state with no play, so that it is possible to suppress the runout in the radial direction. In addition, the simple structure of forming a notch hole in a part of the rotation path of the yoke plate does not require special machining, addition of parts, bonding, etc. as in the conventional case, and the cost can be reduced and the motor can be It is possible to reduce the size.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a disk spindle motor according to the present invention will be described below with reference to the drawings.
The same reference numerals as those in FIG. 4 indicate the same components, and detailed description thereof will be omitted.

FIGS. 1 to 3 show an embodiment of the present invention. In the present invention, a cutout hole 20 is provided in a part on the rotation locus of the yoke plate 3 where the end faces of the rotor magnet 4 face each other. It is characterized by that. That is, the rotor magnet 4 magnetized in the radial direction in multiple poles is held on the inner peripheral surface of the rotor case 5 by adhesion or the like, and the inner peripheral surface of the rotor magnet 4 is arranged at a predetermined interval on the outer peripheral surface of the stator core 2. And the lower end surface of the rotor magnet 4 faces the yoke plate 3 at a predetermined interval. The rotor magnet 4 is magnetically attracted to the stator core 2 and also has a magnetic attraction action on the yoke plate 3.

On the other hand, in a part of the rotation locus of the yoke plate 3 where the end surfaces of the rotor magnet 4 face each other, a slotted hole 20 is provided as shown in FIG. Since the magnetic resistance is increased in the portion of the cutout hole 20 because no magnetic substance is present, the magnetic attraction force is reduced. As a result, as shown in FIG. 3, the magnetic attraction force is stronger on the right side in the drawing, which faces the yoke plate 3, than on the left side in the drawing, in which the cutout hole 20 is provided.

As a result, the rotation of the rotor case 5 is forcibly inclined, so that the rotary shaft 12 is fixed to the above-mentioned FIG.
As shown in FIG. 5, the metal bearing 10 is inclined by the clearance between the inner diameter d1 and the inner diameter d2 of the inner ring of the ball bearing 11. Therefore, the clearance between the two is lost, and the above-described shake can be suppressed.

Since the above-mentioned cutout holes 20 can be formed at the same time when the yoke plate 3 is punched, the manufacturing process need not be changed. Further, the notch hole 20 does not need to have a particular dimensional accuracy, and the manufacturing cost is not much different from the conventional one. Further, the magnetic attraction force can be appropriately set by changing the circumferential size of the cutout hole 20. Further, it is possible to cope with the thinning of the motor only by providing the cutout hole 20. On the contrary, when there is some margin in the axial dimension and it is not desired to leak the magnetic flux of the rotor magnet 4 from the notch hole 20 from the yoke plate 3, the notch hole 20
May be formed in a concave shape with a bottom instead of the through-hole type as in the above-mentioned embodiment. Even in this case, the magnetic attraction increases so that the left and right magnetic attraction forces are asymmetrical. The same effect as the above example can be obtained.

The above-mentioned embodiment shows an example. As the bearing, in addition to the combination of the metal bearing and the ball bearing, the rotating shaft 12 is supported by a pair of upper and lower ball bearings as shown in FIG. Good, also, FIG.
As shown in FIG.
2 may be supported, and various modifications can be made without departing from the present invention.

[0025]

As is apparent from the above description, in the disk spindle motor of the present invention, the yoke plate is provided with the notch hole in a part on the rotation locus of the yoke plate facing the end faces of the rotor magnet. Since the attraction force of the rotor magnet that is magnetically attracted is asymmetrical, as a result, the rotary shaft inclines by the amount of the clearance with the bearing, and the clearance between the two can be eliminated. Therefore, since the rotary shaft is rotated without play, it is possible to suppress the shake in the radial direction. In addition, the simple structure of forming a notch hole in a part of the rotation path of the yoke plate eliminates the need for special processing, addition of parts, and adhesion, which are required in the past, and the cost can be reduced. It is possible to reduce the size.

[0026]

[Brief description of drawings]

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

FIG. 2 is a plan view showing a part of the spindle motor.

FIG. 3 is a cross-sectional view showing the entire spindle motor.

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

FIG. 5 is a sectional view showing a bearing portion of the spindle motor.

FIG. 6 is a cross-sectional view showing an abnormal state of the bearing portion.

FIG. 7 is a sectional view showing another example of a bearing portion of the spindle motor.

FIG. 8 is a sectional view showing still another example of a bearing portion of the spindle motor.

FIG. 9 is a cross-sectional view showing an example of a stator core of the spindle motor.

FIG. 10 is a cross-sectional view showing another example of the stator core of the spindle motor.

FIG. 11 is a cross-sectional view showing a state in which the play of the bearing portion of the spindle motor is suppressed.

[Explanation of symbols]

 1 Drive Coil 2 Stator Core 3 Yoke Plate 4 Rotor Magnet 5 Rotor Case 8 Holder 10 Metal Bearing 11 Ball Bearing 12 Rotating Shaft 13 Hub Stand 20 Notch

Claims (1)

[Claims] 1. A bearing for rotatably supporting a rotating shaft, a yoke plate provided with a holder for holding the bearing, a stator core supported by the holder, and a disk fixed to the rotating shaft on the center side. A rotor case having a hub mount for mounting the rotor magnet, and a rotor magnet held by the rotor case and having an inner peripheral surface facing the stator core and an end surface facing the yoke plate. A spindle motor for a disk, characterized in that a cutout hole is provided in a part on a rotation locus of the yoke plate whose end faces face each other.