JP2000117502A - Hub machining method for spindle motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a machining method to high-precisely machine a part, such as a hub used in a motor, having a small size and a weak machine rigidity. SOLUTION: This method comprises a step wherein a reference groove forming part caused to hold a strength high enough to prevent an influence from being exercised on machining through chucking is formed in a part of a hub 1; a step wherein after the reference groove forming part is chucked by a chuck 12, a hub nipping reference groove 9 is formed in the part, having no disturbance on a cutting work, of the reference groove forming part; and a step wherein the hub reference groove 9 is chucked, and a hub inside diameter part 8, a disc holding wall 2, and a disc mounting surface 15, being parts needed for cutting, which are cut based on the nipping reference groove 9 serving as a reference part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor hub machining method for realizing high precision machining.

[0002]

2. Description of the Related Art The transition to a smaller and higher density hard disk drive (HDD) as a magnetic storage device has been remarkable. This shift to miniaturization inevitably requires a spindle motor incorporated in an HDD to be similarly miniaturized, thinner and lighter. These requirements for miniaturization mean miniaturization of component parts, which leads to small size dimensions and low mechanical rigidity of component parts, and also to difficulty in maintaining processing accuracy. .

Next, a conventional spindle motor will be described with reference to the drawings, and the problem of hub machining of the motor will be specifically described. FIG. 6 is a sectional view showing a conventional typical thin spindle motor. In FIG. 6, reference numeral 50 denotes a flange having a thin circular dish-shaped motor housing portion 51.
A boss 52 is provided at the center of the motor housing 51, and a shaft 53 is fixed and erected at the center of the boss 52. Ball bearings 55 and 56 are attached to the shaft 53 via spacers 54.

A stator mounting frame 57 projects upward from the upper edge of the boss 52, and a stator 59 around which a stator coil 58 is wound is fixed to the outer periphery of the stator mounting frame 57. . Reference numeral 60 denotes a terminal plate to which a lead from the stator coil 58 is connected.

A hub 61 is fixed to the outer rings of the ball bearings 55 and 56. The outer shape of the hub 61 has a convex shape in which two cylinders having different diameters are overlapped, and a disk holding wall 62 is formed at an upper end of the hub 61 so as to pass through a center hole of a hard disk laminated with a spacer interposed therebetween. A hub outer diameter portion 65 that forms a ring-shaped permanent magnet 63 and a yoke 64 inside is formed. A bearing holding cylinder 66 provided on the lower inner side of the hub 61 and holding the ball bearing 56 is loosely fitted inside the stator mounting frame 57. In the motor shown in FIG. 6, a minute gap is formed in a portion indicated by c.
Therefore, when an AC voltage is applied to the stator coil 58 from the terminal plate 60 and a rotating magnetic field is generated in the stator 59, the boss 61 starts rotating.

[0006]

In the machining of parts and hubs that require the highest machining accuracy in a spindle motor, as described above, the mechanical rigidity is reduced due to the reduction in the size of the parts accompanying the miniaturization. Easily distorted by external force during machining,
It has become difficult to ensure the accuracy of the flatness, squareness, roundness, or dimensions of the machined surface. In particular, when mounting (chucking) a workpiece on a spindle mounting jig (chuck) of a machine tool, a problem that the workpiece (work) is distorted and deformed by chuck pressure is likely to occur. It will directly affect accuracy.

[0007] For example, as shown in FIG.
When the chuck 5 is chucked or the bearing holding cylinder 66 is chucked and machined as shown in FIG. 8, the thickness of the chucked portion is small. The deformation as shown in FIGS. 9 and 10 is caused, and the roundness is deteriorated. Further, as shown in FIG. 11, when the stepped portion 67 of the hub 61 made of a forged blank is chucked, deformation of the hub outer diameter portion 65 is unlikely to occur, but when the stepped portion 67 is a forged surface, FIG. As shown in FIG. 11, even if there is a tapered portion 67 at the time of forging, or as shown in FIG. 11, even if the taper is not formed, the roundness accuracy for the cast surface is not obtained, so that The flatness accuracy is affected, and stable accuracy cannot be obtained as shown in FIG.
Here, the flatness refers to the size of the unevenness of the disk mounting surface 69.

[0008] In order to improve the workability by suppressing this distortion and deformation, heat treatment such as tempering is performed to increase the hardness and mechanical rigidity of the processed parts and hubs made of aluminum alloy. There is also a problem that the heat treatment of (1) induces distortion deformation as a part (blank) before processing due to internal stress generated by forging or the like, thereby affecting processing accuracy. For this reason, in order to achieve high-precision machining of the hub, the effects of the blank distortion and deformation caused by the heat treatment are suppressed, and the work deformation due to the chuck pressure is minimized.
Achieving high-precision machining is a major issue.

In order to solve the above problems, the yoke 64 is fixed to the inner peripheral surface of the hub outer peripheral portion 65 and then the inner peripheral surface of the yoke 64 or the outer peripheral surface of the hub outer peripheral portion 65 to which the yoke 64 is mounted. Is disclosed in Japanese Patent No. 2724388 in which the disk mounting surface 69 is cut to obtain flatness by chucking. With this processing method, a considerably good flatness can be obtained up to a diameter of the hub outer peripheral portion 65 of about 1 inch. However, when the diameter is smaller than 1 inch, the thickness of the hub outer peripheral portion 65 becomes thinner. Even if the yoke 64 is fitted inside, the strength of the outer peripheral portion 65 of the hub is not endurable to the cutting process, and it is impossible to perform a good cutting process on the hub.

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned various disadvantages, and an object of the present invention is to propose a processing method for processing these small-sized parts and parts having low mechanical rigidity with high precision. Things.

[0011]

According to the first aspect of the present invention, a hub machining of a spindle motor having a rotor magnetic pole rotating to face a fixed magnetic pole and a hub holding the rotor magnetic pole is provided. In the method, a part of the hub is provided with a reference groove forming part having a strength that does not affect processing by chucking, and after the reference groove forming part is chucked, the reference groove forming part is formed. Among them, a step of providing a hub holding reference groove formed of a groove in a portion that does not interfere with cutting, and a step of chucking the hub holding reference groove and cutting a required cutting portion using the hub holding reference groove as a reference portion, A method for machining a hub of a spindle motor is provided. In the invention according to claim 2 of the present application, in the invention according to claim 1, the portion to be cut using the hub holding reference groove as a reference portion is at least a hub inner diameter portion, a disk holding wall, and a disk mounting surface. A method for machining a hub of a spindle motor is provided. The invention according to claim 3 of the present application provides the hub machining method for a spindle motor according to claim 1, wherein the hub blank is made of a non-magnetic light alloy.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described in detail with reference to the drawings. 1 to 5 are sectional views showing a processing method according to the present invention in accordance with steps. FIG.
In the above, 1 is a hub blank taken out of the mold. The disk holding wall 2 of the hub blank 1 is held by a chuck 3 of a cutting device (not shown). The work (hub blank 1) held by the chuck 3 is rotationally cut. First, hub outer diameter part 4,
The tip portion 5, the yoke insertion surface 6, which is the back side of the hub outer diameter portion 4, the recessed surface 7 of the hub inner wall, the hub inner diameter portion 8 for holding the ball bearing, and the hub holding reference groove 9, which will be a reference for the future processing, are formed in one cutting process. Cut out with.

The hub holding reference groove 9 is a place where the hub blank 1 which is a work is held when the next cutting step is executed. Therefore, the hub holding reference groove 9 must not be a place where the work is deformed by the chucking. Further, when the cutting process is performed on the side opposite to the recessed surface 7 of the inner wall of the hub where the cutting process is currently performed, that is, when the disc holding wall 2 is cut, the chuck 3 holding the hub holding reference groove 9 interferes with the processing. It must be a place that must not be. For such a reason, the hub holding reference groove 9 is provided in the recessed surface 7 of the inner wall of the hub, which is provided in the portion of the work which is the most mechanically strong and suitable inside the disk holding wall 2. The location is defined as a reference groove forming section 10.

Next, the hub blank 1, which is a work, is removed from the chuck 3, and a yoke 11 is pressed into and bonded to the yoke insertion surface 6, as shown in FIG. In the above-mentioned cutting process, the workpiece is machined by clamping the disk holding wall 2 which is the outer ring of the mechanically durable reference groove forming portion 10, so that the roundness accuracy is good and The diameter portion 4, the tip portion 5, and the yoke insertion surface 6 also have a feature that deformation is unlikely to occur.

Next, as shown in FIG. 3, the hub holding reference groove 9 formed in the hub blank 1 is inserted into another chuck 12.
The hub blank 1 is fixed to the cutting device by the chuck 12. In this state, the hub blank 1 is rotated to cut the hub outer diameter portion 4 again.
The disk mounting surface 15, the disk holding wall 2, and the upper surface of the disk inserted and laminated on the disk holding wall, and a pressing plate for fixing them are fitted thereinto, the upper edge portion 17, the hub inner diameter portion 8 ( Re-cutting) in one processing step.

In this cutting process, the hub blank 1 is pinched and fixed to the cutting device with high accuracy by the pinching claws 14 of the chuck 12, and a plurality of portions are cut in one cutting step. There is no deviation in deviation accuracy of degree / roundness. Next, as shown in FIG. 4, a hole is formed for screwing a holding plate for fastening the disk. In this case, since the jig standard for drilling is the hub inner diameter portion 8 where the accuracy is high, the accuracy of the pitch concentricity of each hole 18 can be high. As shown in FIG. 5, the hub holding reference groove 9 is chucked again, and the hub inner diameter portion 8, the disc mounting surface 15, the disc holding wall 2, the fitting surface 16, the upper edge portion 17, and the hub inner diameter portion 8 (re-recutting) are performed. ) In one machining step to finish the hub at once.

Although the present invention has been described with reference to the above embodiment, various modifications and applications are possible within the scope of the present invention, and these modifications and applications are excluded from the scope of the present invention. is not.

[0018]

As described in detail above, according to the first and second aspects of the present invention, in the stage of blanking the hub, the reference groove forming portion is formed at a position on the inner wall surface of the hub where the deformation due to the chuck pressure does not occur. The hub holding reference groove provided here is processed and formed, and the hub holding reference groove for the chuck is chucked consistently, and processing accuracy such as the inner diameter portion of the hub, the disk holding wall, and the disk mounting surface is required. Since the machining of the parts to be machined at the same time, the machining accuracy (roundness / squareness / flatness) and dimensional accuracy of each machined surface can be secured higher than ever before without deformation of the work. In the hub processing of a design structure in which the thickness of the hub is small and there is no appropriate portion for chucking in the center direction of the hub, the hub according to claims 1 and 2 effectively processes the hub. Can be. According to the third aspect of the present invention, since the processing as in the first aspect of the present invention is performed, a high-precision hub can be obtained even with a relatively soft material such as an aluminum light alloy other than iron.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a first stage of a processing method according to the present invention.

FIG. 2 is a cross-sectional view illustrating a second stage of the processing method of the present invention.

FIG. 3 is a cross-sectional view illustrating a third stage of the processing method of the present invention.

FIG. 4 is a sectional view illustrating a fourth step of the processing method of the present invention.

FIG. 5 is a sectional view illustrating a fifth stage of the processing method of the present invention.

FIG. 6 is a sectional view of a conventional spindle motor.

FIG. 7 is a cross-sectional view illustrating a conventional first processing method.

FIG. 8 is a cross-sectional view illustrating a second conventional processing method.

FIG. 9 is a deformation distribution diagram showing a deformed state of a portion chucked by the conventional first processing method.

FIG. 10 is a deformation distribution diagram showing a deformation state of a portion chucked by the second conventional processing method.

FIG. 11 is a cross-sectional view illustrating a third conventional processing method.

FIG. 12 is a deformation distribution diagram showing a deformation state of a portion chucked by the third conventional processing method.

[Description of Signs] 1... Hub blank 2... Disk holding wall 3... Chuck 4... Hub outer diameter part 5. ··························································································· · Yoke 12 ···································································· Fitting part 17 ··············· Hole 50 ... Flange 51 ... Motor storage part 52 ... Boss 53 ... Shaft column 54 ... Spacer 55 ... Ball bearing 56 ... ··· Ball bearings 57 ···· Boss 58 ··· Stator coil 59 ··· Stator 60 ···· Terminal plate 61 ··· Hub 62 Disk holding wall 63 Permanent magnet 64 Yoke 65 Hub outer diameter 66 Bearing holding cylinder 67 Stepped portion 68 ························ Disc mounting surface

Continued on front page F-term (reference)

Claims (3)

[Claims] 1. A hub machining method for a spindle motor having a rotor magnetic pole rotating to face a fixed magnetic pole and having a hub holding the rotor magnetic pole, wherein a part of the hub is machined by chucking. Providing a reference groove forming portion having a strength that does not cause an influence; and, after chucking the reference groove forming portion, clamping a hub formed of a groove in a portion of the reference groove forming portion that does not interfere with cutting. Providing a reference groove; and chucking the hub clamping reference groove, and cutting a required cutting portion using the hub clamping reference groove as a reference portion. 2. A part to be cut using the hub holding reference groove as a reference part is at least a hub inner diameter part, a disk holding wall, and a disk mounting surface.
5. The hub machining method for a spindle motor according to item 1. 3. The method according to claim 1, wherein the hub blank is made of a non-magnetic light alloy.