KR100198149B1 - Ring-shaped bonded magnet production method and its apparatus - Google Patents

Abstract

The present invention relates to a method for manufacturing a ring-shaped resin magnet and an apparatus used therein, wherein the step of heating above a temperature at which deformation is possible is carried out by using an elastic support device that applies a predetermined elastic force to an inner circumferential surface of a ring. Not only does it significantly improve, but the hardening dimension of the resin magnet is changed within the range that maintains the restoring force of the spring, it is not necessary to manufacture another device separately, and it is possible to improve the roundness of the resin magnet without any additional process.

Description

Manufacturing method of ring-shaped resin magnet and apparatus used therefor

1 is a process flow chart for explaining a method for producing a resin magnet.

2 is a schematic cross-sectional view for explaining powder press molding.

3 is a sectional view showing an elastic support device according to the present invention.

Figure 4 is a plan view showing an elastic support device according to the present invention.

5 is a diagram showing the roundness of the Examples and Comparative Examples of the present invention,

5A shows a comparative example.

5b shows an embodiment.

* Explanation of symbols for main parts of the drawings

10: die 12: lower mold

14: die cavity 16: powder

18: upper mold 20: center shaft

22: elastic means 24: support

100: ring-shaped resin magnet

The present invention relates to a ring-shaped resin magnet manufacturing method and an apparatus used therefor, in particular, ring-shaped Nd-based resin magnets used in various precision motors such as servo motors, spindle motors of hard disks, etc. The present invention relates to a manufacturing method for improving the roundness of a ring shape by calibrating and an apparatus used therefor.

In general, resin magnets have different magnetic strengths depending on the type of magnet powder, its orientation and manufacturing method. Ring-shaped magnets used for precision motors such as servo motors and spindle motors of hard disks have resins in rare earth magnet powders. After mixing, an appropriate additive is added in order to improve the filling property of the powder, press-molded into a predetermined shape by pressing, and the resin is cured at an appropriate temperature in an oven to obtain a resin magnet.

Hard disks, floppy disks, optical disks, and magneto-optical disks, which are currently used as external storage devices for computers, are used to read and write information by using a head or pickup by rotating a disk, which is a recording medium, at high speed by a motor. The rotor used in the spindle motor for rotating the disk, which is a recording medium, uses a thin ring-shaped magnet having a thickness of about 1 mm to minimize inertia for high speed rotation of the disk.

In addition, in the case of rotors used in various servo motors, a ring-shaped magnet having a thickness of about 1.5 mm is used to reduce inertia.

In order to manufacture such a ring magnet, conventionally, as shown in FIG. 1, a mixing step of mixing a magnet powder and a resin, a molding step of pressing and mixing the mixed powder by a press, and a molded product produced in the molding step Hardening process to melt the resin in the oven heated to a predetermined temperature to give strength to the crosslinked magnet powder, and in the case of Nd-based resin magnets by electrodeposition coating to the outside after the curing process to give antirust It consists of electrodeposition coating process which is baked for 15 minutes at 170 ℃.

If internal diameter deviation occurs in the inside of several ring-shaped resin magnets made by the above-described process, when the rotor is formed by combining an organic adhesive to the central axis of the metal material, irregularities are formed on the rotor surface. As a result, the magnetic field deviation due to the deviation of the rotor inertia and the gap between the stator and the rotor occurs.

Since the deviation of the rotor inertia and the magnetic field deviation cause ripple due to the rotation of the motor, the overall performance of the motor is deteriorated. Therefore, in order to maximize the performance of the motor, it is preferable to minimize the inner diameter of the resin magnet.

In addition, if a deviation occurs in the outer diameter of the resin magnet, the average gap between the inner surface of the magnetizing yoke and the outer surface of the resin magnet increases when the rotor is assembled and put into the magnetizing yoke of the pulse magnetizer to magnetize in the predetermined magnetization direction. If the magnetization is incomplete, the magnetic energy of the resin magnet is reduced, thereby degrading the performance of the motor.

Moreover, rotors magnetized in a predetermined direction are mounted in the stator to constitute a motor, wherein the rotor and the stator are spaced apart from each other by a predetermined gap, and only by minimizing these gaps as much as possible operates between the rotor and the stator. The magnetic force is increased to increase the rotational force of the motor, but if the size of the rotor and stator is not precise, the gap between the rotor and the stator occurs when the gap between the rotor and the stator is reduced In order to reduce the pressure, it is necessary to precisely control the dimensional accuracy of the rotor and stator.

Thus, the dimensional accuracy of the rotor and the stator is an important factor that determines the performance of the motor, and in particular, it is important to manage the ring-shaped resin magnets forming the rotor so that the inner diameter deviation and the outer diameter deviation occur less.

In general, however, when the powder is press-molded by a press, it is perpendicular from the upper mold 18 to the powder 16 filled in the die cavity 14 formed in the die 10 and the lower mold 12 as shown in FIG. When the force is applied, the mixed powder 16 generates tensile stress in the circumferential direction as well as the compressive stress in the vertical direction.

At this time, when powder is compressed, the powder flows and moves, and compression proceeds, but after the powder is compressed to some extent, the powder inside the mold is easily made as the resistance between the powder and the powder and the friction between the powder and the mold increases. As it does not flow, localized stress concentrations appear within the molded part.

Therefore, when the molded article is taken out from the mold, the compression in the circumferential direction is released, so that the so-called expansion of the molded article called spring-back occurs. Particularly, in the ring-shaped molded article, the local stress generated by internal friction is taken out. This loosening results in a difference in local expansion rate for each part of the molded article, and when such expansion difference occurs, the ring-shaped molded part may have a convex shape in which some parts are convex and another part is concave. there was.

In addition, the volume of the product expands as the ring-shaped molded product is hardened during the curing process, and the crushing becomes larger when taking out the molding process due to the difference in expansion ratio due to the local density difference generated during the molding process. There was a problem.

In order to solve the above problems, conventionally, a method of improving ring-shaped roundness by hardening by inserting a rigid rod into the ring-shaped resin magnet inner circumferential surface and heating the rod and ring-shaped resin magnet together in an oven is used. However, this method is inconvenient to re-fabricate the rigid rod according to the change in the dimensions of the product.

Furthermore, in the case of Nd-based resin magnets, rust resistance is required. After the curing process, the product is immersed in a paint flowing in a certain direction. The electrodeposition coating for forming the electrode is performed, wherein the support means for serving as a conductor for supplying electricity to the product as well as for supporting the product in the flowing paint is required. When using a rod to improve the roundness, there is a labor trouble in that the rigid rod must be removed and replaced with a separate support means.

Accordingly, an object of the present invention is to provide a method of manufacturing a ring-shaped resin magnet that can effectively improve the roundness of a ring-shaped resin magnet mounted on a rotor.

Another object of the present invention is to provide an elastic support device for applying a predetermined elastic force to the inside of the ring-shaped resin magnet to improve the roundness of the ring-shaped resin magnet.

Method for producing a ring-shaped resin magnet of the present invention for achieving the above object, the mixing step of mixing the magnetic powder and the resin, the molding step of pressing the molded powder by pressing the molding, produced in the molding step A ring consisting of a curing process of melting resin in an oven heated to a predetermined temperature to impart strength to a molded body and crosslinking the magnetic powder, and an electrodeposition coating process of electrodeposition coating on the surface after the curing process to impart rust resistance. A method of producing a shaped resin magnet, characterized in that it is carried out in a state in which a predetermined elastic force is applied to an inner circumferential surface of a ring in a step of heating above a temperature at which deformation is possible.

An elastic support device for achieving another object of the present invention, the central shaft and the lower end of the central shaft is connected to the predetermined support by a predetermined elastic means at equal intervals characterized in that it consists of a plurality of supports extending in the circumferential direction It is done.

According to the manufacturing method as described above, if the step is carried out with the elastic support device mounted on the inner peripheral surface of the resin magnet during the curing process or electrodeposition coating process of the ring-shaped resin magnet, the support is in contact with the inner peripheral surface of the resin magnet It is supported by one elastic force to improve the roundness of the product, and when it is carried out during the electrodeposition process, it acts as a hanger to keep the resin magnet soaked in the paint and to give the properties of the coating film. By correcting the distortion of the resin magnet by the elastic force of the support at the time to improve the roundness of the resin magnet effectively.

Hereinafter, with reference to the accompanying drawings, an embodiment of the present invention will be described in detail.

Figure 3 is a side cross-sectional view showing the elastic support device according to the present invention, Figure 4 is a plan view of the elastic support device, a predetermined elastic means 22 at intervals of 120 degrees to the lower periphery of the central shaft 20 Is provided, and a plurality of supports 24 extending in the circumferential direction are connected to the end of the elastic means 22, so that each support 24 has the same force to the outside of the inner circumferential surface of the ring-shaped resin magnet 100 to the outside. It was pushed.

At this time, the elastic means is for example using a spring.

An example in which the elastic support device is used during the electrodeposition coating process of the resin magnet will be described below.

EXAMPLE

A powder containing 3 wt% of an epoxy resin mixed with an Nd-based magnet powder was molded in a press at a molding pressure of 8 ton / cm ² to form a ring shaped body having an outer diameter of 49 mm, an inner diameter of 44 mm, and a height of 11 mm, and heating the molded body at 180 ° C. It was put in the oven, heated for 30 minutes, and cooled to cure.

Then, roundness was measured to compare the roundness shape of the cured resin magnet.

As shown in FIG. 3, the elastic support device according to the present invention was inserted into the resin magnet, followed by electrodeposition coating, followed by baking for 15 minutes at 170 ° C. or higher to measure roundness.

For comparison, the roundness of the resin magnet subjected to electrodeposition coating was also measured without using the elastic support device according to the present invention.

5 is a diagram showing the results of measuring the roundness of the Examples and Comparative Examples, respectively, Figure 5a shows a comparative example on a scale of 50㎛, Figure 5b shows a comparative example on a scale of 2㎛.

And the center of each circle (a) represents the imaginary circle in the resin magnet, the crushed circle (b) represents the original state of the resin magnet actually measured.

In each measured result, the roundness is 4.40 µm and the distribution range is ± 3 µm in the measured results, and the comparative example is rounded and distorted, while the comparative example has a roundness of 79.55 µm and the distribution range is ± 40 µm.

As can be seen from the above results, the embodiment according to the present invention can be seen that the roundness is greatly improved compared to the comparative example, and the roundness of the outer diameter is about 20 times improved, and the distribution range is much narrower.

As can be seen from the above, the resin magnets produced by the method of manufacturing the resin magnets according to the present invention not only greatly improve the roundness, but also change differently when the hardening dimension of the resin magnets is changed within the range of maintaining the spring restoring force. There is no need to manufacture a device, and also the roundness of the resin magnet can be improved without any additional process.

What has been described above is merely a mere example in all respects, and should not be construed as limited thereto, and all modifications existing within the true spirit and scope of the present invention shall fall within the claims of the present invention.

Claims (2)

A mixing step of mixing the magnet powder and the resin, a molding step of pressing the mixed powder with a press and molding, and melting the resin in an oven heated to a predetermined temperature to give strength to the molded product produced in the molding step. The ring-shaped resin magnet is composed of a hardening process for crosslinking the magnet powder and an electrodeposition coating process for electrodeposition coating on the surface after the hardening process to impart the hardening process and the rust prevention property on the surface after the hardening process to impart rust resistance. A method of manufacturing a ring-shaped resin magnet, wherein the hardening / or electrodeposition coating is performed in a state in which an elastic force is applied to the inner circumferential surface of the ring-shaped magnet member which has undergone the molding step. In the support device for hanging the ring-shaped magnet member in the manufacture of the ring-shaped resin magnet, the center shaft 20 and the elastic means 22 of the conductive material extending at intervals of 120 ° to the lower periphery of the center shaft 20 And a support (24) attached to the distal end of the elastic means (22) to apply an elastic force while being in contact with the inner circumferential surface of the ring-shaped member.