JP3063560B2 - Demagnetization method and demagnetization device for anisotropic magnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for manufacturing a bonded magnet having magnetic anisotropy formed by bonding magnetic powder with a resin, which is suitable for preventing foreign particles such as magnetic powder from adhering due to residual magnetism. The present invention relates to a method and a device for demagnetizing an anisotropic magnet.

[0002]

2. Description of the Related Art Generally, a magnet used for a small motor, an auto iris mechanism, or the like is a bonded magnet formed by mixing a magnetic powder and a resin, and is particularly strong when the direction of the axis of easy magnetization is oriented in one direction. Magnetically anisotropic bonded magnets having magnetism (for example, SmCo or Nd using rare earth elements)
FeB magnet) is preferred. In this method of manufacturing a bonded magnet having magnetic anisotropy, a magnetic powder and a resin are mixed, then molded in a magnetic field, and further cured at a temperature of 150 to 200 ° C. Thereafter, a process such as a coating for corrosion prevention is performed, and the film is magnetized again in a DC magnetic field to manufacture the device.

In the above-described manufacturing method, it is necessary to perform demagnetization in order to prevent foreign matter such as magnetic powder from adhering before processing the formed bonded magnet. In particular, since NdFeB magnets and the like are easily corroded, there is a step of applying a coating for improving the corrosion resistance after molding. Before this step, it is necessary to demagnetize the molded article to remove foreign substances adhering to the surface. However, in the case of a bonded magnet, the heat resistance temperature (20
(0 ° C. to 300 ° C.) is relatively low, and cannot be degaussed by heating to a temperature equal to or higher than the Curie point (300 ° C. to 400 ° C.) like a normal sintered magnet. For this reason, conventionally, the following method is used as the demagnetizing means.

First, after the magnetic field is oriented at the time of molding, demagnetization is performed as much as possible by applying a reversal magnetic field in a mold. Thereafter, before being removed from the mold, the bond magnet is previously marked (for example, stamped with a punch or the like) or the like, and after being removed from the mold, the remaining magnetic field orientation directions are slightly aligned and arranged. Complete demagnetization is performed by applying an alternating magnetic field that gradually decreases in parallel to this direction.

[0005]

However, the above-described demagnetizing means has the following problems to be solved. It is difficult to completely demagnetize only by demagnetization in the mold by the reversal magnetic field, especially when molding many pieces at once because the magnetic field applied to each compact varies. It is impossible to do. In addition, in order to align the magnetic field orientation method, a process such as marking the bond magnet is required as described above, resulting in a great increase in cost. The present invention has been made in view of the above-described problems, and has as its object to completely demagnetize a bonded magnet, reduce the number of demagnetization steps, and achieve cost reduction.

[0006]

In a method of demagnetizing a magnet having magnetic anisotropy, two or more magnetized magnets are arranged in a line and are attracted to each other to align their respective magnetic field orientations with the magnet arrangement direction. A technique including a magnetic field orientation direction alignment step and a magnetic field application step of applying a magnetic field to the magnets in a direction parallel to the alignment direction to demagnetize these magnets is adopted.
Also, a magnet alignment step of arranging two or more magnets in a line, and applying a DC magnetic field to the magnets in parallel to the alignment direction to magnetize the magnets and attract them to each other so that the respective magnetic field alignment directions are aligned with the magnet alignment direction. A technique is employed that includes a temporary magnetizing step of aligning and a magnetic field applying step of applying a magnetic field to these magnets in a direction parallel to the arrangement direction to demagnetize the magnets. Further, in the method of demagnetizing these anisotropic magnets, the step of applying a magnetic field includes the step of applying an alternating magnetic field that gradually attenuates the magnets in parallel in the direction in which the magnets are arranged, thereby demagnetizing the magnets. Technology is added. In the demagnetizing device for magnets having magnetic anisotropy, an alignment means for arranging two or more magnets in a line, a magnet transport path for transporting the aligned magnets, and a magnet provided in the middle of the magnet transport path. On the other hand, a temporary magnetizing coil for applying a DC magnetic field in parallel to the arrangement direction, and an AC magnetic field provided downstream of the temporary magnetizing coil in the magnet conveyance path and gradually attenuating in parallel with the arrangement direction for the magnet is applied to the magnet. A technology including a demagnetizing coil is employed.

[0007]

[Function] When a plurality of magnets magnetized in advance are arranged in a line,
Since the magnets are magnetized, the different poles of the magnets attract each other and rotate and attract each other. At this time, the respective magnetic field orientation directions are aligned in the arrangement direction. When a magnetic field is applied to the magnets arranged in this manner in parallel to the direction in which the magnets are arranged (for example, a reversal magnetic field or the like in the direction of the magnetic field is applied), the strength of magnetization of the magnets is reduced, and Can be magnetized. In the case of a plurality of magnets having different magnetization intensities, including unmagnetized magnets and magnets that are only slightly magnetized, after arranging these magnets in a row, the DC magnetic field is parallel to the magnet arrangement direction. Is applied, the respective magnets are temporarily magnetized, and the different poles are attracted to each other by rotating. At this time, the respective magnetic field orientation directions are aligned in the arrangement direction. Thereafter, these magnets are demagnetized by applying a magnetic field parallel to the arrangement direction as described above. When the above magnetic field is applied to demagnetize the magnet, if an alternating magnetic field that gradually attenuates in parallel to the direction in which the magnets are arranged is applied, the intensity of the magnet magnetization of the magnet also gradually decreases with the attenuation of the alternating magnetic field, and the final Typically, the magnet is completely demagnetized by attenuating the strength of the alternating magnetic field to zero. In the anisotropic magnet demagnetizing apparatus of the present invention, two or more magnets are arranged in a line by an aligning means, and the aligned magnets are transported by a magnet transport path. The magnet conveyed in this way is temporarily magnetized by applying a DC magnetic field parallel to the direction of arrangement by a coil for temporary magnetization in the middle of the magnet transport path, and attracts and rotates by attracting mutually different polarities. . At this time, the respective magnetic field orientation directions are aligned in the arrangement direction. Thereafter, the temporarily magnetized magnet is conveyed, and an alternating magnetic field that gradually attenuates in the direction in which the magnets are arranged is applied by a demagnetizing coil provided downstream of the temporarily magnetized coil. This completely demagnetizes the magnet.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. In these figures, reference numeral 1 denotes a bond magnet, 2 denotes a bond magnet demagnetizer, 3 denotes a parts feeder, 4 denotes a guide plate, 5 denotes a magnet transport path, 6 denotes a temporary magnetizing coil, and 7 denotes a demagnetizing coil. is there.

As shown in FIG. 1, a demagnetizing device 2 includes a parts feeder 3 for supplying a plurality of bond magnets 1, a pair of guide plates 4 connected to a supply path 3A of the parts feeder 3, and A magnet conveying path 5 on which the plate 4 is disposed,
Temporary magnetizing coil 6 provided in the middle of magnet conveyance path 5
And a demagnetizing coil 7 provided downstream of the temporarily magnetized coil 6 in the magnet transport path 5.

Inside the parts feeder 3, a plurality of bonded magnets 1 having different magnetization states and unmagnetized states are housed. These bonded magnets 1 are made of SmCo or NdF
These are magnetic anisotropic bonded magnets such as eB magnets, each of which is formed in the same cylindrical shape. Parts feeder 3
Is to align the bond magnets 1 by applying vibration to the internal bond magnets 1 and send them out to the supply path 3A, and a pair of guide plates 4 provided in a connected state on both side walls 3B of the supply path 3A. Together, they constitute an alignment means for arranging the bond magnets in a line. The interval between the side walls 3B is set so as to gradually decrease toward the guide plate 4,
The connecting portions of the side walls 3B with the guide plate 4 and the distance between the pair of guide plates 4 are set slightly wider than the diameter of the bond magnet 1. A belt conveyor 5A is provided along the guide plate 4 at the lower end of the supply path 3A. The belt conveyor 5 </ b> A conveys the bond magnet 1 fed from the supply path 3 </ b> A in the length direction of the guide plate 4 while being positioned between the pair of guide plates 4.

In the middle of the belt conveyor 5A, a temporary magnetizing coil 6 formed in a cylindrical shape is provided so that the belt conveyor 5A is located on the center axis. The temporary magnetizing coil 6 applies a direct-current magnetic field parallel to the length direction of the guide plate 4 to the bond magnet 1 conveyed on the belt conveyor 5A.
And magnetized. Belt conveyor 5A
A belt conveyor 5B is provided close to the end of the belt conveyor 5A, and is arranged in a direction orthogonal to the length direction of the belt conveyor 5A. This belt conveyor 5B
Is set so that a plurality of magnet trays 8 opened to the belt conveyor 5A side are conveyed, and the bonded magnets 1 conveyed by the belt conveyor 5A are transferred inside the magnet tray 8. The end of the belt conveyor 5B is disposed close to the side of the belt conveyor 5C arranged in parallel with the belt conveyor 5A, and the magnet tray 8 in which the bonded magnets 1 are stored is placed on the upper surface of the belt conveyor 5C. It is set to transfer to.

In the middle of the belt conveyor 5C, a demagnetizing coil 7 formed in a cylindrical shape is provided so that the belt conveyor 5C is located on the center axis. The demagnetizing coil 7 attenuates the magnetic field in an alternating current state parallel to the conveying direction of the belt conveyor 5C and applies the same to the bond magnet 1 conveyed on the belt conveyor 5C to demagnetize.
The above-mentioned belt conveyors 5A, 5B, and 5C constitute the magnet conveyance path 5 of the bond magnet 1, respectively. Above the belt conveyors 5A and 5C, upper belt conveyors 5D and 5E are arranged at predetermined intervals so as to penetrate the temporary magnetizing coil 6 and the demagnetizing coil 7, respectively, and in parallel with the belt conveyors 5A and 5C. Have been. The upper belt conveyors 5D and 5E transport the bond magnet 1 together with the belt conveyors 5A and 5C so that the bond magnet 1 is rotatable to such an extent that the bond magnet 1 is rotatable. To prevent them from being attracted and adsorbed when passing through.

Next, an example of one step of the method for demagnetizing an anisotropic magnet according to the present invention when the above-described demagnetizing apparatus 2 is used will be described.

[Alignment of Magnets] First, the parts feeder 3
Is operated, the internal bond magnet 1 is sent out to the supply path 3A, and in the process of reaching the guide plate 4, the supply path 3
A is guided by the side wall 3B of A and is aligned in a line. The aligned bonded magnets 1 are fed from the supply path 3A to the belt conveyor 5A.
After being sent out to the upper surface of the sheet, by operating the belt conveyor 5A, the sheet is conveyed while being kept in a line by the pair of guide plates 4. At the time of the transport, as shown in FIG. 2A, the bond magnets 1 have different magnetization strengths, and include those slightly magnetized and those having zero magnetization strength. Therefore, the orientation direction of the magnetic field and the direction of the axis of easy magnetization are randomly oriented. Note that FIG.
In the figure, the length of the arrow is proportional to the strength of the magnetization of the bond magnet 1, and the direction of the arrow and the direction of the broken line indicate the direction of the magnetic field orientation and the direction of the easy axis of magnetization. The bond magnet 1 without an arrow has a magnetization strength of zero.

[Temporary magnetization of magnet (alignment of magnetic field orientation direction)]
The bond magnet 1 is transported by the belt conveyor 5A, and passes through the inside of the temporary magnetizing coil 6. At this time, the temporary magnetizing coil 6 is operated, and a DC magnetic field parallel to the direction in which the bond magnets 1 are arranged is applied to the passing bond magnets 1.
As a result, the bonded magnets 1 are temporarily magnetized to the strength of magnetization that attracts and rotates by attracting different poles to each other. Each bonded magnet 1 that has passed through the inside of the temporary magnetizing coil 6
As shown in FIG. 2 (b), since the magnetic field is magnetized, the magnetic field orientation direction and the direction of the easy axis of magnetization are aligned in a direction parallel to the alignment direction, and are conveyed while maintaining this state.

The bonded magnets 1 having the aligned magnetic field orientations are conveyed to the end of the belt conveyor 5A and sent out to the upper surface of the belt conveyor 5B. At this time, the belt conveyor 5B is placed on the upper surface of the belt conveyor 5B.
The magnet tray 8 with the A side opened is placed, and the belt conveyor 5B is operated so as to be positioned on the extension of the bond magnet 1 in the alignment direction. As a result, a fixed number of bonded magnets 1 sent from the belt conveyor 5A are transferred and stored inside the magnet tray 8 of the belt conveyor 5B while maintaining the aligned state. The transfer of the bond magnets 1 is sequentially performed for every fixed number into a plurality of magnet trays 8 placed on the upper surface of the belt conveyor 5B.

The bonded magnet 1 transferred to the magnet tray 8
Is transported to the end by the belt conveyor 5B,
It is sent to the upper surface of the adjacent belt conveyor 5C.

[Application of AC Decaying Magnetic Field to Magnet] The magnet tray 8 is conveyed by the belt conveyor 5C and passes through the inside of the demagnetizing coil 7. At this time, the demagnetizing coil 7
Is operated, and an alternating magnetic field parallel to the direction in which the bond magnets 1 pass is gradually attenuated and applied to the passing bond magnet 1. With the decay of the AC magnetic field, the strength of the magnetization of each bond magnet 1 also gradually decreases, and finally, the strength of the AC magnetic field is attenuated to zero to completely bond each bond magnet 1 inside the magnet tray 8. To demagnetize. Since the bond magnet 1 made of a ferromagnetic material causes a hysteresis phenomenon in the relationship between the strength of the applied magnetic field and the strength of the magnetization, when the magnetic field in the DC state is simply applied and gradually attenuated, the strength of the magnetic field is reduced. Becomes zero, the magnetization intensity does not become zero and shows a finite value. However, since the magnetic field is attenuated in the AC state as described above, the residual magnetism due to the hysteresis phenomenon gradually decreases, and the bond magnet 1 is completely demagnetized in a state where the strength of the AC magnetic field reaches zero. As shown in FIG. 2C, the bond magnets 1 that have passed through the demagnetizing coil 7 have the same easy axis direction and the magnetization intensity is zero. Thereafter, these completely demagnetized bond magnets 1 are transported to the next step.

Although the present embodiment is applied to the bonded magnet 1, other magnets having magnetic anisotropy can obtain the same effect. For example, it may be applied to a sintered magnet. Further, although the shape of the bond magnet 1 is cylindrical, other shapes may be used. For example, a rectangular parallelepiped magnet may be used. When only a plurality of magnets that have already been magnetized and attract and attract different poles are demagnetized, at the time of alignment by the parts feeder 3 and the guide plate 4, the respective magnets are attracted to each other and aligned with the direction of the magnetic field and Since the direction of the axis of easy magnetization can be aligned in a direction parallel to the alignment direction, it is not necessary to operate the above-described coil for temporary magnetization 6.

[0020]

According to the present invention, the following effects can be obtained. (1) After magnetized magnets are arranged side by side and attracted to each other to align the magnetic field orientation direction in the arrangement direction, an AC damping magnetic field is applied in the arrangement direction to perform demagnetization. Can be easily prepared, high-cost steps such as marking can be reduced, and these magnets can be demagnetized. (2) After arranging the magnets, a DC magnetic field is applied in parallel to the arrangement direction to temporarily magnetize the magnets, and the magnets are attracted to each other. Then, a magnetic field is applied in the arrangement direction to perform demagnetization. Even when applied to magnets having a small state and a small intensity of magnetization, the orientation of the magnetic field can be reliably and easily aligned, and these magnets can be demagnetized. (3) When demagnetizing the magnet by applying the above-described magnetic field, the intensity of the magnetization of the magnet is reduced to zero by applying an alternating magnetic field that is gradually attenuated in parallel with the direction in which the magnets are arranged. Can be magnetized. (4) According to the anisotropic magnet demagnetizing apparatus of the present invention, the magnet alignment means, the magnet conveyance path of the aligned magnets, the temporary magnetizing coil for applying a DC magnetic field, and the AC attenuation magnetic field are used. Since a demagnetizing coil to be applied is provided, a large amount of magnets can be continuously and reliably demagnetized, the mass productivity of the demagnetizing step is improved, and the production cost can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an anisotropic magnet demagnetizing apparatus according to the present invention.

FIG. 2 is an explanatory view showing a magnetic field orientation direction and a magnetization easy axis direction in each step of demagnetization by an embodiment of the anisotropic magnet demagnetization apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bond magnet (magnet) 2 Demagnetization device 3 Parts feeder 3A supply path 4 Guide plate 5 Magnet conveyance path 5A, 5B, 5C Belt conveyor 6 Temporary magnetizing coil 7 Demagnetizing coil

Claims (4)

(57) [Claims] 1. A method for demagnetizing a magnet having magnetic anisotropy, comprising: arranging two or more magnetized magnets in a line and adsorbing each other to align the respective magnetic field alignment directions with the arrangement direction of the magnets. And a magnetic field applying step of applying a magnetic field to the magnets in a direction parallel to the arrangement direction to demagnetize the magnets. 2. A method for demagnetizing a magnet having magnetic anisotropy, comprising: a magnet alignment step of arranging two or more magnets in a line; A temporary magnetization step of magnetizing and adsorbing each other to align the respective magnetic field orientations in the direction in which the magnets are arranged, and a magnetic field applying step of applying a magnetic field to these magnets in parallel to the arrangement direction to demagnetize the magnets. A method for demagnetizing an anisotropic magnet, comprising: 3. The method of demagnetizing a magnet having magnetic anisotropy according to claim 1, wherein the step of applying a magnetic field includes applying an alternating magnetic field that gradually attenuates the magnets in parallel to a direction in which the magnets are arranged. A demagnetizing method for an anisotropic magnet, which is an AC attenuating magnetic field applying step for demagnetizing these magnets. 4. An apparatus for demagnetizing a magnet having magnetic anisotropy, comprising: an aligning means for arranging two or more magnets in a line; a magnet transport path for transporting the aligned magnets; A temporary magnetizing coil for applying a DC magnetic field in parallel to the magnets in the direction in which the magnets are arranged, and an AC magnetic field provided downstream of the temporary magnetizing coils in the magnet conveyance path and gradually attenuating in parallel to the magnets in the direction in which the magnets are arranged. And a demagnetizing coil for applying a voltage.