JPH09149614A - Spindle motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the unbalance value and improve the efficiency of the assembly work when a magnetic disc is clamped. SOLUTION: A motor has a housing 1, a rotor hub part 2 which can rotate freely relatively to the housing 1 and to which a magnetic disc 9 is attached, a shaft 4 which is mated with a sleeve part 3 fixed to the housing 1 and a sleeve part 3 fixed to the rotor hub part 2 so as to rotate freely, a magnet 6 attached to the rotor hub part 2 and a stator core 7 which is so fixed to the housing 1 as to face the magnet 6. The shaft 4 is so supported as to rotate freely by the sleeve parts 3 with fluid material therebetween. A screw hole 13 for a clamping screw 12 by which a clamping member 11 which clamps the magnetic disc 9 is fixed is provided in the end surface of the shaft 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to fixing a shaft of a disk drive spindle motor having a small diameter of 3.5 inches or less, which is mainly used for optical and magnetic disk devices.

[0002]

2. Description of the Related Art In recent years, optical and magnetic disk devices tend to be smaller and lighter and have higher capacity. With the spread of notebook-sized personal computers, there is a demand for smaller and thinner spindle motors, as well as demand for improved shock resistance. Further, recently, with respect to the rotational accuracy of ball bearings, it has become very difficult to cope with high capacity. As a solution to the above, a hydrodynamic bearing spindle motor is being developed. However, in order to reduce the variation in the fluid dynamic pressure, it is necessary to reduce the tolerance of the shaft diameter of the fluid bearing. Therefore, highly accurate polishing is required to manufacture the shaft. Therefore, the shaft and the rotor hub must be formed as separate parts, and depending on the disc clamping structure, sufficient attention must be paid to the fixing of the shaft and the rotor hub.

A disk clamp system of a conventional magnetic disk drive (hereinafter abbreviated as HDD) will be described below with reference to the drawings from the structure of a spindle motor.

FIG. 4 is a sectional view of a conventional HDD spindle motor with ball bearing specifications in which a magnetic disk is clamped. In FIG. 4, 31 is a housing, 32 is a rotor hub portion, 33 is a ball bearing, 34 is a shaft, 3
5 is a magnet, 36 is a stator core, 37 is a coil,
38 is a magnetic disk, 39 is a spacer, 40 is a clamp member, and 41 is a clamp screw.

The motor housing 31 is provided with a cylindrical portion 31a on the inner peripheral portion and a flange portion 31b on the outer peripheral portion, and a pair of ball bearings 33 are fixed on the inner peripheral portion of the cylindrical portion 31b.
The shaft 34 is rotatably supported via the ball bearing 33, and the rotor hub portion 32 is fixed to one end of the shaft 34. The coil 3 is provided on the outer peripheral portion of the cylindrical portion 31a.
The stator core 36 around which 7 is wound is fixed. The rotor hub portion 32 has a cup shape in which a disc receiving surface 32a and a disc inner diameter regulating cylindrical portion 32b are formed. At the position facing the stator core 36 on the inner peripheral portion of the tubular portion of the cup-shaped rotor hub portion 32, N is circumferentially provided.
A cylindrical magnet 35 in which the poles and the S poles are alternately magnetized is fixed. A magnetic disk 38 is mounted on the disk receiving surface 32a of the rotor hub portion 32, the magnetic disks 38 are mounted with a spacer 39 at a predetermined distance, and a clamp member 40 is arranged at the top. Attach the clamp member 40 to the rotor hub 32 with a clamp screw 41.
The magnetic disk 38 is clamped between the disk receiving surface 32 a and the clamp member 40 by tightening with.

Here, in the spindle motor as described above, a small ball bearing has to be used in accordance with the reduction in outer diameter. Since small ball bearings do not provide sufficient rotation accuracy, it is difficult to achieve high capacity. Further, since the impact resistance is extremely reduced, there is a problem that the ball bearing is deteriorated by the impact and a noise problem occurs. Therefore, recently, a spindle motor using a fluid dynamic bearing filled with lubricating oil has also been developed.

[0007]

The clamp member 40 such as the spindle motor shown in FIG.
On the other hand, in the clamp method in which the screw is tightened, readjustment is often required, resulting in poor work efficiency, which has been a serious problem in streamlining the assembly.

When tightening the magnetic disk 38, if the tightening force of each clamp screw 41 varies, the magnetic disk 38 is distorted and warped. Therefore, it is necessary to temporarily tighten all the screws in advance and then tighten with the set tightening torque. If the adjustment is improper, the tightening of the screws must be readjusted. This is the first reason why readjustment is necessary.

Further, there is a screw portion near the outer peripheral portion of the rotor hub portion 32, and when the screw is tightened by the clamp screw 41, the inner diameter regulating cylindrical portion 32b of the rotor hub portion 32 is deformed by the screw tightening, and the diameter is increased. 38
There is a problem that an unnecessary force acts on the inner peripheral end surface of the device, and a defect easily occurs in the process of changing the environmental temperature by the heat run of the HDD inspection. On the other hand, if the fitting gap between the rotor hub portion 32 and the magnetic disk 38 is increased, it cannot be increased because imbalance is likely to occur, and a defective product in the process is reset by re-setting the magnetic disk 38. I have to do it. This is the second reason why readjustment is necessary.

Since the clamp screw 41 is located at a position close to the distance between the center of rotation and the inner diameter of the magnetic disk 38, imbalance is likely to occur. It must be adjusted and re-clamped so that there is less eccentricity from. This is the third reason why readjustment is necessary.

As described above, since two steps are required for tightening, such as temporarily tightening all the clamp screws 41 in advance and then tightening with the set tightening torque, the work efficiency is poor and the assembly cannot be rationalized. is there. In addition, there is a problem that the magnetic disk is warped, the amount of unbalance is increased, the influence of the clamp on the heat run process failure, and the work efficiency is further deteriorated due to the large number of clamp screws.

Further, in a spindle motor using a fluid dynamic pressure bearing, since the bearing rigidity is smaller than that of a ball bearing, it is necessary to further reduce the amount of unbalance, which further deteriorates work efficiency.

Further, in the case of a small HDD, there is a problem that the screw portion provided on the rotor hub portion 32 becomes large in space, so that the magnet cannot be made large and the motor characteristic is sacrificed.

In view of the above-mentioned conventional problems, the present invention provides a spindle motor which has a small amount of unbalance when a magnetic disk is clamped by a clamp member, has a good work efficiency in assembling, and can rationalize an assembling process. It is an object.

[0015]

A spindle motor according to the present invention includes a housing, a rotor hub portion which is rotatable with respect to the housing and on which a magnetic disk is mounted, a sleeve portion fixed to the housing, and a rotor hub portion. A shaft that is rotatably fitted to the sleeve portion, a magnet that is mounted on the rotor hub portion, and a stator core that is fixed to the housing facing the magnet. In a spindle motor rotatably supported by a screw, a screw hole for screwing a clamp member for clamping a magnetic disk is provided on an end surface of a shaft.

Preferably, the stopper is fixed to the shaft, and the stopper is brought into contact with the rotor hub portion. At this time, more preferably, the shaft is provided with a groove, and the stopper is inserted and fixed in the groove. . Alternatively, the small diameter portion of the stepped shaft is inserted and fixed in the shaft fixing portion of the rotor hub portion, and the stepped portion contacts the rotor hub portion.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) A first embodiment in which the present invention is applied to a spindle motor for an HDD using a fluid dynamic bearing will be described with reference to FIG. FIG.
In (a), 1 is a housing, 2 is a rotor hub portion,
3 is a sleeve part, 4 is a shaft, 5 is a thrust plate, 6 is a magnet, 7 is a stator core, 8 is a coil, 9 is a magnetic disk, 10 is a spacer, 11 is a clamp member, 12
Is a clamp screw, and 22 is a stopper.

The housing 1 of the motor is provided with a cylindrical portion 1a on the inner peripheral portion and a flange portion 1b on the outer peripheral portion.
The sleeve portion 3 is attached to the inner circumference of a, and the flange portion 1b
Is attached to the HDD chassis. Cylindrical part 1
A stator core 7 around which a coil 8 is wound is fixed to the outer periphery of a. The rotor hub portion 2 is formed in a cup shape having a disc receiving surface 2a and an inner diameter regulating cylindrical portion 2b of the disc, and rotates about a shaft 4 fixed at the center thereof. A cylindrical magnet 6 having N-poles and S-poles alternately magnetized in the circumferential direction is fixed to the inner circumference of the tubular portion of the cup-shaped rotor hub 2.

When a current is applied to the coil 8, a magnetic field is generated in the salient poles of the stator core 7, torque is generated between the stator core 7 and the field magnet 6 facing the stator core 7, and the rotor hub portion 2 is rotated. Therefore, the magnetic disk 9 clamped on the rotor hub portion 2 rotates.

The thrust plate 5 is fixed by caulking to the lower end of the sleeve portion 3 fixed to the cylindrical portion 1a on the inner peripheral portion of the housing 1, and the inside thereof is filled with lubricating oil as a fluid substance. . A spiral dynamic pressure bearing groove is formed in the thrust plate 5, and is supported rotatably in the thrust direction by the dynamic pressure generated at the end face of the thrust plate 5 and the shaft 4 as the shaft 4 rotates. Also,
A herringbone groove is formed on the inner circumference of the sleeve portion 3 or the outer circumference of the shaft 4, and the inside thereof is filled with lubricating oil. The shaft 4 is rotatably supported by the dynamic pressure generated in the lubricating oil in the radial direction as the shaft 4 rotates, without contacting the sleeve 3.

FIG. 1A shows a state in which two magnetic disks 9 are mounted. The magnetic disks 9 are mounted on the disk receiving surface 2a while being separated by a spacer 10 at a constant distance, and a clamp member 11 is arranged on the uppermost magnetic disk 9. The clamp member 11 is tightened by a clamp screw 12 screwed into a screw hole 13 provided on the end surface of the shaft 4, and the central portion of the clamp member 11 is bent by the tightening force, and the bending reaction force causes a magnetic disk to dissipate. The inner peripheral portion of 9 is clamped.

As described above, the magnetic disk 11 can be clamped through the clamp member 11 by screwing and tightening the single clamp screw 12 into the screw hole 13 provided in the end surface of the shaft 4, thus making the clamping work efficient. You can do it well. Further, since the single clamp screw 12 is used for clamping, the amount of unbalance can be reduced.

Further, in FIG. 1B, the shaft 4 and the rotor hub member 2 are fixed by a light interference fit.
Further, a groove 4a is provided on the shaft, a stopper 22 is fastened to the groove 4a, and the stopper 22 abuts on the rotor hub portion 2,
The amount of movement of the shaft in the axial direction is regulated.

In this way, the movement amount of the shaft 4 is stopped by the stopper 2
Since it is regulated by 2, the shaft 4 does not move relative to the rotor hub portion 2 in the thrust direction even if the clamping force of the magnetic disk 9 acts on the shaft 4 through the clamp screw 12, and the rotor hub portion does not move. Since the clamping force can be sufficiently supported even if the size of the fixed portion of 2 and the shaft 4 is reduced, the bearing span of the fluid dynamic bearing can be lengthened correspondingly and the bearing performance can be improved in a small size.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to FIG. In the description of the second embodiment, the same components as those of the first embodiment shown in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted. Only the differences will be described.

In FIG. 2, the shaft 4 and the rotor hub portion 2 are press-fitted and fixed. Further, without providing a groove on the shaft 4, the stopper 22 is fixed to the shaft 4 by press fitting, adhesion, or welding, and abuts on the rotor hub portion 2 to regulate the axial movement amount of the shaft. . Since the movement amount of the shaft 4 is regulated by the stopper 22, even if the clamping force of the magnetic disk acts on the shaft 4 via the clamp screw, the shaft 4 moves relative to the rotor hub portion 2 in the thrust direction. There is no fear of doing

(Third Embodiment) Hereinafter, a third embodiment of the present invention will be described with reference to FIG. In the description of the third embodiment, the same components as those of the first embodiment shown in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted. Only the differences will be described.

In FIG. 3, in the present embodiment, the shaft 4 is a stepped shaft having a small diameter portion and a large diameter portion. The rotor hub portion 2 is fixed to the small diameter portion 4b of the shaft 4 by a light interference fit, and the step portion 4c with the large diameter portion of the shaft 4 contacts the rotor hub portion 2 from below.

By contacting the step portion 4c of the shaft 4 from below, the amount of movement of the shaft 4 in the thrust direction can be regulated, so that the shaft 4 can be moved by the clamping force for clamping the magnetic disk 9. Without, the tightening force can be increased.

Thus, even if the size of the fixed portion of the rotor hub 2 and the shaft 4 is reduced, the clamping force of the clamp member 11 can be sufficiently supported, and the shaft 4 does not come off due to the clamp tightening by the clamp screw. The magnetic disk 9 can be clamped stably.

[0032]

According to the spindle motor of the present invention, as is apparent from the above description, one clamp screw is screwed into the screw hole provided on the end face of the shaft and tightened, and the magnetic disk is inserted through the clamp member. Since the work is clamped, the work efficiency of the clamp work can be improved, the clamp work can be rationalized, the imbalance caused by the clamp screw is unlikely to occur, and the amount of unbalance can be reduced. Even with the pressure bearing, high rotation accuracy and long life can be secured.

Further, by fixing the stopper to the shaft and bringing the stopper into contact with the rotor hub, even if the size of the fixed portion of the rotor hub and the shaft is reduced, the shaft will not come off due to the tightening of the clamp screw. The stable shaft can be fixed. By reducing the size of the fixed part of the rotor hub and shaft in this way,
The bearing span of the fluid bearing can be lengthened accordingly, and the bearing performance can be improved with a small size.

Further, the shaft is a stepped shaft having a small diameter portion and a large diameter portion, the small diameter portion of the shaft is press-fitted into the rotor hub portion, and the step portion with the large diameter portion is brought into contact with the rotor hub portion to clamp the clamp. The shaft can be prevented from coming off due to the tightening of screws, and stable shaft fixing can be achieved.

[Brief description of the drawings]

FIG. 1A is a sectional view of a spindle motor according to a first embodiment of the present invention. FIG. 1B is a partially enlarged sectional view of a rotor hub portion and a shaft fixing portion of a spindle motor according to a first embodiment of the present invention.

FIG. 2 is a partially enlarged sectional view of a rotor hub portion and a shaft fixing portion of a spindle motor according to a second embodiment of the present invention.

3A is a sectional view of a spindle motor according to a third embodiment of the present invention. FIG. 3B is a partially enlarged sectional view of a rotor hub portion and a shaft fixing portion of a spindle motor according to a third embodiment of the present invention.

FIG. 4 is a sectional view of a conventional spindle motor.

[Explanation of symbols]

 1, 31 Housing 1a, 31a Cylindrical part 1b, 31b Flange part 2,32 Rotor hub part 2a, 32a Disc receiving surface 2b, 32b Disc inner diameter regulating cylindrical part 3 Sleeve part 4,34 Shaft 4a Groove 4b Small diameter part 4c Step part 5 Thrust plate 6,35 Magnet 7,36 Stator core 8,37 Coil 9,38 Magnetic disk 10,39 Spacer 11,40 Clamp member 12,41 Clamp screw 13 Screw hole 22 Stopper 33 Ball bearing

Claims (3)

[Claims] 1. A housing body, a sleeve portion fixed to the housing, a rotor hub portion that is rotatable relative to the housing body, a shaft fixed to the rotor hub portion, and a rotor hub portion. A spindle motor comprising a rotor magnet directly or indirectly mounted and a stator core arranged to face the rotor magnet, wherein the shaft rotates with respect to the sleeve portion via a fluid substance, A screw portion for screwing a clamp member for clamping a disc is formed on the end surface of the shaft on the rotor hub side, and a groove is formed on the circumference of the shaft, and a fastener is tightened in the groove. A spindle motor, wherein the spindle motor is in contact with the rotor hub portion to regulate an axial movement amount of the rotor hub portion. 2. The spindle motor according to claim 1, wherein the stopper is fixed to the shaft by press fitting, bonding or welding without forming a groove on the circumference of the shaft. 3. A housing body, a sleeve portion fixed to the housing, a rotor hub portion rotatable relative to the housing body, a shaft fixed to the rotor hub portion, and a rotor hub portion. A spindle motor comprising a rotor magnet directly or indirectly mounted and a stator core arranged to face the rotor magnet, wherein the shaft rotates with respect to the sleeve portion via a fluid substance, On the end surface of the shaft on the rotor hub side, a screw portion for screwing a clamp member for clamping a disc is formed, the shaft has a small diameter portion and a large diameter portion, and the rotor hub is fastened to the small diameter portion, The stepped portions of the small diameter portion and the large diameter portion are in contact with the rotor hub portion to regulate the amount of axial movement of the rotor hub portion. The spindle motor according to claim.