JPH04265647A - Spindle motor - Google Patents

Abstract

PURPOSE:To pressurize specified pressure to the rotary shaft of a hub and maintain stable pressure by plastically deforming one part of a bracket, and applying inward force to the bearing member. CONSTITUTION:Screws 7 are screwed in the two places of the circular projections 71 provided all around the inside periphery of the bracket 2 of a spindle motor. Guide grooves with specified depths are bored in advance in the circular projections 71 in which the screws 7 are screwed, and as the screws 7 are screwed in to the specified depth, the margins of the guide grooves widen, and they cause plastic deformation. If one sets the direction of resultant, which works in the direction of the shaft center of the shaft member 11 by the plastic deformation of the screwing of the screw 7, in the direction of having no harm in the direction of the fall of a record disk, the accuracy in the rotation of a spindle motor such as whirling, etc. can be maintained high.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor installed in, for example, an optical/magnetic disk device and used to rotate a recording disk.

0002

[Prior Art] Conventionally, temperature changes in the surrounding environment of a motor,
The temperature rise due to the heat generated by the motor itself causes distortion due to expansion and contraction of each component. Especially in spindle motors,
The shaft part provided on the hub is rotatably supported by the bracket via the bearing member. Therefore, when distortion occurs due to the difference in thermal expansion between the bracket and the bearing member, a minute gap is created between them. This creates play and causes the hub to fall. As a result, when this spindle motor is used as a motor for driving a magnetic disk, there is a problem in that a so-called off-track phenomenon occurs, which causes malfunctions in writing and reading information by the magnetic head to and from tracks on the magnetic disk.

As a countermeasure for this, in conventional spindle motors, in order to tilt the rotating shaft of the hub in advance in one direction that does not affect the use, a pressing means such as a coil spring, a leaf spring, or an O-ring is used to tilt the rotating shaft of the hub in advance. The outer peripheral surface of one of the bearing members is pressed. Specifically, the pressing means is pressed into contact with the outer circumferential surface of the bearing member such that a certain point on the outer circumferential surface of the bearing member always comes into contact with the inner circumferential surface of the bracket, that is, the inner circumferential surface of the cylindrical portion of the bracket. It is interposed between the inner peripheral surface of the cylindrical part.

0004

[Problems to be Solved by the Invention] However, when assembling a spindle motor using this pressing means, it is necessary to press the outer periphery of the bearing member while mounting it, and at that time, it is difficult to press the outer periphery of the bearing member excessively. Then, the bearing member is likely to be damaged. Furthermore, it is necessary to constantly manage appropriate pressing force against variations in elasticity of springs, O-rings, and the like. In addition, deterioration of the pressing means over time may lead to a decrease in elastic force, resulting in vibrations due to co-rotation and backlash of the outer periphery of the bearing member.
This causes a decrease in rotation accuracy. These factors not only increase manufacturing and management costs, but also cause a decrease in reliability.

The present invention has been made in view of the above facts, and its main purpose is to apply a predetermined pressing force to the rotating shaft of the hub and to maintain a stable pressing force. An object of the present invention is to provide a spindle motor that is economical and reliable.

[0006]

[Means for Solving the Problems] According to the present invention, there is provided a bracket having a cylindrical portion, a hub rotatable relative to the bracket, and a shaft provided on the cylindrical portion of the bracket and the hub. a pair of bearing members interposed between the hub, a rotor magnet attached to the hub, and a stator disposed opposite the rotor magnet,
In a spindle motor that is rotationally driven by relative rotation between the rotor magnet and the stator, an axial end portion of the cylindrical portion is partially plastically deformed, and the plastic deformation causes the outer peripheral surface of at least one of the bearing members to have a radius. A spindle motor is provided, characterized in that the spindle motor is configured to press inward in a direction.

[0007]

[Operation] Plastic deformation occurs in a portion of the axial end of the cylindrical portion of the bracket, thereby distorting the inner circumferential wall of the cylindrical portion so as to protrude radially inward. Since the bearing member is attached to the inner circumferential surface of the cylindrical portion, the outer circumferential portion of the bearing member is pressed due to the distortion of the inner circumferential wall. The amount of plastic deformation can be adjusted depending on the degree of threading of the screw, and therefore the bearing member can be pressed in a predetermined direction. Furthermore, since an elastic member or the like is not used as a pressing member, a predetermined pressing force is maintained and the elastic force does not deteriorate due to aging.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of a spindle motor according to the present invention. FIG. 1 is a sectional view of a spindle motor equipped with, for example, three 5-inch disks. In FIG. 1, 1 is a hub, 2 is a bracket, 3 is a stator, 4 is a rotor magnet, 5 and 6 are bearing members, 7 is a screw, and 8 is a magnetic fluid sealing device.

The hub 1 is made of aluminum, stainless steel, or the like, and the shaft portion 11 is press-fitted into a hole drilled in the axial center of the main body of the hub 1, so that they rotate together. has been done. A rotor yoke 41 made of a magnetic material is disposed inside the hub 1 over the entire circumference, and a rotor magnet 4 is further provided on the inner peripheral surface of the rotor yoke 41 . The stator 3 is fitted and fixed to the outer peripheral surface of a cylindrical portion 23 provided on the inner peripheral portion of the bracket 2, and is disposed opposite to the rotor magnet 4. In addition, the cylindrical portion 23
Bearing members 5 and 6 are mounted on the inner circumferential surface of the rotor magnet 4, and the shaft portion 11 is rotatably supported via these bearing members 5 and 6. Therefore, relative rotation between the rotor magnet 4 and the stator 3 is prevented. As a result, the hub 1 is rotationally driven.

The lead wire 32 drawn out from the armature coil 31 of the stator is electrically connected to the circuit board 91 by soldering or the like. The circuit board 91 is led out of the spindle motor by a flexible board or the like (not shown). 9 is a magnetic sensor for rotation detection;
It is arranged to face the lower end surface of the rotor magnet and is connected to the circuit board 91.

A magnetic fluid sealing device 8 is provided at the top of the cylindrical portion 23. The magnetic fluid sealing device 8 includes a magnetic unit in which a pole piece is sandwiched between an annular magnet;
A magnetic fluid is filled in the gap between the outer circumferential portion of the shaft portion 11 and the opposing shaft portion 11 . Thereby, the external space 20 of the spindle motor and the disk space 30 are sealed, and in particular, it is possible to effectively prevent contamination of the magnetic disk by grease mist components scattered from the bearing members 5 and 6.

[0015] The member 45 is a magnetically shielding sheet, which is adhered to the entire upper circumference of the inside of the hub, and is made of a magnetic material like the rotor yoke 41. Then, the magnetic flux leaking from the rotor magnet 4 through the hub 1 can be effectively shielded, and errors in reading and writing to the recording disk can be prevented.

FIG. 2 is an enlarged sectional view showing the lower part of the cylindrical portion 23 of the bracket 2 of the spindle motor in FIG. In FIGS. 1 and 2, one (upper) bearing member 5
, whose inner and outer rings are respectively the shaft part 11 and the inner circumferential surface 2 of the cylindrical part.
2, and the other (lower) bearing member 6
are also installed in the same way. In order to maintain rotational accuracy of the spindle motor, one of the bearing members 5 has its inner and outer rings fixed to the shaft portion 11 and the cylindrical portion 22 with adhesive or the like, and the other bearing member 6 is fixed to the shaft portion 11. C attached to
Spring washer 6 disposed on ring 66 and bracket 2
5, a preload is applied to each other in the axial direction of the inner ring and the outer ring as shown in FIG.

That is, the outer ring 61 of the bearing member 6 is elastically pressed outward in the axial direction by the spring washer 65, downward in FIG. 2, while the inner ring is pushed inward by the C ring 66.
In FIG. 2, it is relatively pressed upward. Note that the shaft portion 11
Due to the stress applied to the bearing member 5, since the inner and outer rings are fixed to the shaft portion 11 and the cylindrical portion 22, respectively, a preload is similarly applied to each other in the axial direction.

Cylindrical portion 2 that comes into contact with outer ring 61 of bearing member 6
At the base of the bracket 2 (lower end in FIGS. 1 and 2), an annular protrusion 71 is provided all around the inner peripheral edge of the bracket 2. FIG. 3 is a bottom view showing the spindle motor viewed from below. In FIGS. 2 and 3, this annular protrusion 71
Two screws 7 are screwed onto the top. A guide hole of a predetermined depth is pre-drilled in the annular protrusion 71 to which the screw 7 is screwed, and as the screw 7 is screwed to a predetermined depth, the guide hole periphery 77 expands, causing plasticity. cause deformation. Normal bracket 2
is made of a metal material, and aluminum is used in this embodiment, so that plastic deformation can be easily obtained.

Due to the plastic deformation caused by the threading of the screw 7, the inner edge 72 and outer edge 74 of the annular protrusion 71 are deformed as shown by the two-dot chain line in FIG. 2, and the inner edge 72 protrudes somewhat inward. At the same time, the outer edge portion 74 protrudes outward somewhat. The inner edge portion 72 of the annular projection presses a predetermined portion of the outer ring 61 of the bearing member 6 inward. Since the screw 7 is screwed onto the annular protrusion 71 at two places, the resultant force of the pressing force due to the plastic deformation of the annular protrusion 71 is applied to the shaft member 11 as shown by the two-dot chain arrow in FIG.
It acts in a predetermined direction of the axis (to the left in FIG. 3). That is,
The guide holes may be provided at substantially equal angular positions in both directions (for example, the angle is α) with respect to the pressing direction. As a result, if the direction of the resultant force is set in advance in a direction that does not interfere with the direction in which the recording disk falls, it is possible to maintain high rotation accuracy of the spindle motor, such as whirling. In particular, it is possible to effectively prevent read/write errors on the recording disk even when temperature conditions change. The annular groove 75 is provided to facilitate plastic deformation of the annular protrusion 71 and to prevent overall deformation or distortion of the bracket 2 due to the plastic deformation.

In the spindle motor of the embodiment, in order to apply this preload in the axial direction, it is only necessary to attach the bearing members 5 and 6 to the cylindrical portion 22 and then screw the screw 7 onto the annular protrusion 71. Not only is assembly simple, but no excessive force is applied to the bearing members 5 and 6, and no damage is caused. Further, the amount of plastic deformation of the bracket 2 changes depending on the degree of screwing of the screw 7, so that a desired pressing force can be applied. Further, since the location where the screw 7 is screwed onto the annular protrusion 71 can be freely set by changing the position of the guide hole, the pressing direction can be adjusted freely.

Although one embodiment of the spindle motor according to the present invention has been described above, the present invention is not limited to this embodiment, and various modifications and modifications can be made without departing from the scope of the present invention. be.

For example, in the embodiment, an example of a shaft rotation type in which the shaft portion 11 rotates relative to the bracket 2 has been described, but the shaft portion 11 is fixed and the hub 1 rotates via the bearing members 5 and 6. A fixed shaft type may also be used. Furthermore, in this embodiment, a radial gap type outer rotor type spindle motor is shown in which the rotor magnet 4 and the stator face each other with a gap in the radial direction from the axis. An axial gap type system may also be adopted in which the two electrodes face each other.

The material used for the bracket 2 can be freely selected, whether it is a metal material or a resin material. Further, the size of the screws 7, the screw pitch, the number of screws, etc. can be set freely. In addition, in the preloading method, the bearing member 5 may also be preloaded at the same time, and any method other than the above may be freely selected within the scope of the present invention. It goes without saying that the annular protrusion 71, annular groove 75, etc. shown in this embodiment may be omitted and the screw 7 may be directly screwed onto the bracket.

Further, for example, in the embodiment, a part of the bracket 2 is plastically deformed by screwing together the screw 7, but it may also be plastically deformed by press-fitting a pin or the like instead of the screw 7. Alternatively, plastic deformation may be simply applied by applying an external force.

[0025]

Advantages of the Invention Since the present invention has the above-described configuration, it has the following effects. That is, since an inward force is applied to the bearing member by plastically deforming a part of the bracket 2, a force in a predetermined direction can be applied relatively easily and simply. Moreover, this allows a stable pressing force to be maintained and high rotational accuracy to be maintained over a long period of time.

[Brief explanation of the drawing]

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

FIG. 2 is a partially enlarged sectional view showing a part of the spindle motor in FIG. 1;

FIG. 3 is a bottom view of the spindle motor in FIG. 1, viewed from below.

[Explanation of symbols]

1 Hub 11 Shaft part 2 Bracket 23 Cylindrical part 3 Stator 31 Amateur coil 4 Rotor magnet 41 Rotor yoke 5 Bearing member 6 Bearing member 7 Screw 77 Screwed periphery 8 Magnetic fluid seal device 9 Magnetic sensor 91 Circuit board

Claims (1)

[Claims] Claim 1: A bracket having a cylindrical portion, a hub rotatable relative to the bracket, and a pair of hubs interposed between the cylindrical portion of the bracket and a shaft provided on the hub. A spindle motor comprising a bearing member, a rotor magnet attached to the hub, and a stator disposed opposite to the rotor magnet, and is rotationally driven by relative rotation between the rotor magnet and the stator, A spindle motor characterized in that an axial end portion of the cylindrical portion is partially plastically deformed, and the plastic deformation presses an outer peripheral surface of at least one of the bearing members radially inward.