JP4674799B2 - Multipolar ring permanent magnet magnetizer - Google Patents

Description

  The present invention relates to an apparatus for magnetizing a permanent magnet. More specifically, the present invention lowers the temperature of an object to be magnetized from a temperature above its Curie point to a temperature below its Curie point while applying a magnetizing magnetic field. The present invention relates to a magnetizing device used in a permanent magnet magnetizing method. Although this technique is not particularly limited, it is effective for, for example, multipolar magnetization of a ring-shaped permanent magnet used for a rotor of a very small diameter stepping motor.

  In order to multi-polarize a ring-shaped permanent magnet rotor incorporated in a radial gap type permanent magnet stepping motor or the like, a coil energization type magnetizing apparatus is generally used. This type of magnetizing device is provided with a magnetized object accommodation hole into which a ring-shaped permanent magnet, which is a magnetized object, can be inserted / extracted in a magnetic yoke, for example, and an inner wall surface of the magnetized object accommodation hole In this structure, a plurality of grooves extending in the axial direction are formed, and insulation-coated conductors are embedded in the grooves, and adjacent insulation-coated conductors are continuously folded to form a coil. The magnetized object is inserted into the magnetized object receiving hole, and the electric charge stored in the capacitor is instantaneously released, so that a pulse current is passed through the coil and magnetized by the magnetic field generated thereby.

  As is well known, in response to the recent remarkable downsizing of electronic devices, stepping motors and the like used therefor have also been downsized and reduced in diameter. When a ring-shaped permanent magnet used as a rotor is magnetized in multiple poles, a large pulsed current is passed using the coil energization type magnetizing device as described above. Since the pitch (distance between magnetized magnetic poles) is narrowed, the diameter of a conducting wire is reduced, and the current value that can be passed through the conducting wire is limited. Therefore, there has been a problem that sufficient magnetization characteristics cannot be obtained.

  As one method that can solve such a problem, a plurality of inverted magnetic poles are formed in the central portion by arranging a plurality of permanent magnets radially, and four or more poles are provided by arranging an adherend in the central portion. Has been proposed (see Patent Document 1). Certainly, by using such a permanent magnet type magnetizing apparatus, the insufficient magnetization which becomes a problem when the magnetic pole pitch of the object to be magnetized is reduced can be improved to some extent.

  However, there is a great demand for downsizing (smaller diameter) and higher performance of recent stepping motors. For example, in an autofocus mechanism of a portable video device, a stepping motor magnetized with a narrow pitch multipolar magnet capable of controlling a lens actuator with high accuracy in order to obtain a high-definition image is an important electronic component. Here, as a ring-shaped permanent magnet constituting the rotor, for example, there is a demand for a magnetization characteristic of a saturation magnetization level for a narrow pitch structure having a diameter of 3 mm or less and a number of magnetic poles of 10 or more. For such a magnetized structure, in the conventional magnetizing method as described above, there is a problem that magnetization is insufficient even if the permanent magnet method is used, and the variation of the surface magnetic flux density peak value is large.

  As a technique for improving the lack of magnetization, a method of magnetizing an object to be magnetized using a decrease in saturation magnetization magnetic field in a high-temperature atmosphere or liquid has been proposed (see Patent Document 2). For example, in a Pr—Fe—B magnet, which is a kind of rare earth permanent magnet, the magnetization magnetic field at 100 ° C. has a lower value than the magnetization magnetic field at 25 ° C., and thus magnetization is performed in this temperature region. Thus, it is disclosed that it is possible to perform saturation magnetization in a stable low magnetic field.

However, when actually magnetizing, in the ring-shaped permanent magnet with a narrow magnetization pitch such as the above-mentioned minimum diameter and multipole, the average value of all the poles of the surface magnetic flux density peak value is somewhat magnetized. However, the variation in the surface magnetic flux density peak value is still large, and high quality magnetization is extremely difficult.
JP 2001-268860 A JP-A-6-140248

  The problem to be solved by the present invention is that even with a ring-shaped permanent magnet with a narrow magnetization pitch, such as extremely small diameters and multiple poles, there is no shortage of magnetization, the magnetization quality can be improved, and strong magnetization at low cost. It is to provide a device that can perform work efficiently and quickly.

  As a technique that does not cause insufficient magnetization and can improve the magnetization quality, the present inventors have first made a permanent magnet, which is an object to be magnetized, from a temperature above its Curie point to a temperature below its Curie point. A method of magnetizing a permanent magnet that continues to apply a magnetizing magnetic field to an object to be magnetized while lowering the temperature was proposed (Japanese Patent Application No. 2004-374918). According to this method, it is possible to obtain a ring-shaped permanent magnet having high magnetization characteristics (magnetic force characteristics) and good magnetization quality even with a very small diameter / multipole magnetization structure.

The present invention is an apparatus effective for implementing such a magnetization method. In the present invention, basically, the heating part and the magnetized part are arranged in the axial direction as separate structures, and the heating part and the magnetized part are supported so as to be relatively close to and away from each other. The holding member for the magnetic material can be moved relative to the heating unit and the magnetizing unit, the magnetized material is heated by the heating unit separated from the magnetized unit, and the magnetized material is heated. The magnetized part and the heating part are brought close to each other as they are, and then the magnetized material is moved to the magnetized part and magnetized, so that the magnetized part and the heating part are separated from each other. It is a magnetic device. In the present invention, the magnetized part may be fixed and the heating part may be movable, or conversely, the heating part may be fixed and the magnetized part may be movable. Further, the holding member for the magnetized object may be moved with respect to the magnetized part and the heating part, or conversely, the holding member for the magnetized object is fixed and the heating part and the magnetized part are moved relative thereto. You may comprise.

Specifically, the present invention includes a heating unit you heat the ring-shaped deposition磁物What circumferential plane forms a tubular structure Do the heating surface, the peripheral surface in a tubular structure is magnetized surface the magnetization and the magnetized portion for performing multiple poles the the outer circumferential surface by applying a magnetizing magnetic field to the deposition磁物I Do, while axially disposed separately structure, and the heating unit a Department relatively toward and away rotatably supported, and the ring-shaped rod-like holding member for holding the deposition磁物can relatively move in the axial direction through said heating unit and said magnetized portion is installed in said magnetized portion and said by the heating unit in a state of separated deposition磁物is heated, the said magnetized portion in a state where該被adhesive磁物is heated the heating unit is brought close, then deposition磁物in the heating unit is transferred into the magnetized portion, the magnetized portion and the heating portion is separated, and so as to magnetized in the magnetized portion DOO is a magnetizing apparatus for multipolar ring-shaped permanent magnet according to claim.

  The magnetized portion may be a coil energization system that applies a magnetic field generated by energizing the coil, but in particular when a very small permanent magnet is magnetized in multiple poles, a permanent magnet that applies a magnetic field by the permanent magnet is used. A magnet system is preferred. As an example of such a magnetized portion, a circular magnetized object receiving hole into which a magnetized object can be inserted / extracted is provided at the center of the nonmagnetic block, and the inner wall surface of the magnetized object receiving hole is provided. There is a structure in which a plurality of grooves extending radially from the same angle are provided at equal angles, and permanent magnets for magnetization having higher Curie points than the magnetized objects are embedded in the grooves.

  The present invention may be a saddle arrangement type in which magnetized portions and heating portions are arranged vertically and the axis direction is vertical, or the heating portions and magnetized portions are arranged side by side, and the axis direction is horizontal. It may be a horizontal arrangement form. A heat insulating member may be interposed between the magnetized part and the heating part.

  In the magnetizing apparatus of the present invention, the heating part and the magnetizing part are separated from each other so that they can be approached and separated, and the holding member of the magnetized object moves relative to the heating part and the magnetizing part. Since it is configured to be possible, the object to be magnetized is heated to a temperature above the Curie point in the heating part, then quickly moved to the magnetized part and lowered to a temperature below the Curie point, while magnetizing The operation of continuously applying the magnetic field can be easily performed by a series of operations, and the workability of magnetization is improved. As a result, even in a ring-shaped permanent magnet with a narrow magnetization pitch, such as a very small diameter and multiple poles, insufficient magnetization does not occur, the magnetization quality can be improved, and powerful magnetization can be efficiently performed at low cost.

  In particular, if a permanent magnet having a high Curie point is used as the magnetized portion, it is easy to cope with a narrowing of the magnetization pitch, so that a ring-shaped permanent magnet having a minimum diameter of 3 mm or less and a multipolar ring magnet having 10 or more poles can be attached. It is effective for magnetism, can simplify the device and extend its life, and has the advantage of reducing the operating cost due to the fact that energization is unnecessary.

  FIG. 1 is an explanatory view showing an embodiment of a magnetizing apparatus according to the present invention. This magnetizing apparatus includes a heating unit 10 having a cylindrical structure and an inner peripheral surface serving as a heating surface, and a magnetizing unit 12 having a cylindrical structure and an inner peripheral surface serving as a magnetized surface, which are separate from each other. And, it is arranged in the axial direction (in the direction along the axis). This example is a saddle arrangement format in which the heating unit 10 is positioned below and the magnetized unit 12 is positioned vertically so that the axis direction is vertical. The heating unit 10 and the magnetized unit 12 are supported so as to be relatively close to and away from each other. In the separated state, a sufficient space is provided between the heating unit 10 and the magnetized unit 12 in order to prevent excessive heating of the magnetized unit 12. A thin heat insulating member 14 is preferably provided on the upper surface of the heating unit 10. A cooling unit 16 is provided on the outer peripheral side of the magnetized unit 12. On the other hand, a rod-shaped holding member 22 that holds the magnetic object (permanent magnet) 20 is installed so as to be movable in the axial direction through the heating unit 10 and the magnetized unit 12. Here, the magnetized part 12 is fixed, and the heating part 10 is driven in the vertical direction by the vertical drive mechanism 24 so as to be able to approach and separate from the magnetized part 12. The holding member 22 for the magnetized object 20 is driven in the vertical direction by the vertical drive mechanism 26 so that the magnetized object 20 moves relative to the heating unit 10 and the magnetized unit 12. This is because the holding member is lighter, and therefore it is possible to speed up the movement of the holding member. Of course, the holding member may be fixed, and the heating unit and the magnetizing unit may be moved by a driving mechanism. The control unit 28 controls the temperature of the heating unit 10 and the operations of the vertical drive mechanisms 24 and 26 (position, stop time, etc.).

  An example of the internal structure of the magnetized portion is shown in FIG. This example is a permanent magnet system in which a magnetic field generated by a permanent magnet is applied to an object to be magnetized as a magnetizing magnetic field. FIG. 2 shows a horizontal cross section at the position xx in FIG. The object to be magnetized 20 is a ring-shaped permanent magnet, and is an example of magnetizing it. The magnetized portion 12 is provided with a circular magnetized object accommodation hole 32 into which a magnetized object 20 can be inserted and extracted at the center of a nonmagnetic block (for example, a stainless steel block) 30 and the magnetized part. Ten grooves 34 having a rectangular cross section extending radially from the inner wall surface of the object accommodation hole 32 are provided at equal angles, and each groove 34 has a quadrangular rod-shaped permanent magnet 36 having a Curie point higher than that of the magnetized object. It is the structure which buried each. Therefore, the inner peripheral surface of the magnetized portion 12 becomes a magnetized surface.

  Here, the heating unit 10 includes a heating unit main body 40 on the outer peripheral side and a heat transfer unit 42 located on the inner peripheral side thereof, and a plurality of sheath heaters (resistance heaters) extending in the axial direction are provided on the heating unit main body 40. It is a structure arranged in a circle. The heat generated in the heating unit main body 40 is transmitted to the inside by the heat transfer unit 42 made of brass having good thermal conductivity. Therefore, the inner peripheral surface of the heat transfer section 42 becomes a heating surface. The heating unit 10 has the capability of heating the magnetic object positioned in the magnetic object receiving hole 44 to a temperature above its Curie point and maintaining it at a predetermined constant temperature.

  The rod-shaped holding member 22 that holds the ring-shaped magnetic object 20 is a combination of a lower support 46 and an upper presser 48 and has a structure that holds the magnetic object 20 from above and below. Of course, the holding can be performed only by the support. The heating unit 10 also heats the surrounding air, and the heated air rises and tries to heat the magnetized unit 12. The heat insulating member 14 prevents the magnetized portion 12 positioned at the top of the heating unit 10 from being heated by natural convection or the like, and may be any material as long as it has heat resistance performance and heat insulation performance. Good. The cooling unit 16 serves to cool the magnetized unit 12 and maintain the temperature of the magnetized unit 12 substantially constant. By controlling the heating unit 10 at a constant temperature, the magnetized unit 10 is kept substantially constant by natural cooling of the cooling unit 16. Of course, the cooling unit 16 may also perform temperature control.

  In the present invention, the Curie point of the magnetizing permanent magnet is set so that the magnetizing permanent magnet 36 can generate a magnetic field that can magnetize the magnetized object 20 at a high temperature. Set higher than the Curie point. In order to minimize the magnetic field required for magnetization of the magnetized object, the heating temperature is set higher than the Curie point of the permanent magnet that is the magnetized object, and the magnetizing permanent magnet is The heating temperature is set to be lower than the Curie point of the permanent magnet for magnetization in order to leave a magnetic field that can be magnetized on the object to be magnetized and to have a magnetizing ability.

  Taking the case where the object to be magnetized 20 is an NdFeB isotropic magnet (Curie point: about 350 to 390 ° C. depending on the material) as an example, the permanent magnet 36 for magnetization is an SmCo sintered magnet (Curie point: about 850). ° C) is preferred. The heating unit 10 needs to be capable of being heated to a Curie point Tc or higher of the adherend (it is desirable that it can be heated to about Tc + 30 ° C. or higher according to experimental results).

FIG. 3 is an explanatory view showing the operation of this magnetizing apparatus.
A: Mounting of magnetic object A indicates a state in which the magnetic object 20 is mounted on the holding member 22. The adherend magnet 20 is held between the lower support 46 and the upper presser 48.
B: Heating of the magnetic object to be magnetized The holding member 22 is lowered to place the magnetic material to be magnetized 20 in the heating unit 10 and heated at a predetermined temperature above the Curie point of the magnetic object to be magnetized. For example, when the adherend is an NdFeB isotropic magnet (Curie point: about 350 ° C.), the adherend 20 is heated to about 380 ° C. by the heating unit 10.
C: Heating unit movement The holding member 22 is not moved as it is (the position of the magnetized object 20 is not changed), the heating unit 10 is raised, and the upper surface of the heating unit 10 (not shown, but the upper surface is omitted). 1 is closely attached to the lower surface of the magnetized portion 12.
D: Magnetization The holding member 22 is raised to feed the object to be magnetized 20 into the magnetized portion 12, and a predetermined magnetizing magnetic field is applied by the magnetizing permanent magnet.
E: Cooling If the magnetized object 20 is sent into the magnetized part 12, the heating part 10 is immediately lowered. Thereby, the magnetized portion 12 is cooled by the cooling portion 16. Meanwhile, the magnetized magnetic field is continuously applied to the magnetized object 20 in the magnetized portion 12. In this way, the magnetized object 20 is cooled to a temperature below the Curie point while being installed in the magnetized portion 12 (according to the experimental results, it is preferable to cool to Tc-50 ° C. or lower. ). As a result, the maximum magnetization can be applied to the object to be magnetized, and the object to be magnetized is magnetized. Therefore, when the object is cooled to a temperature below the Curie point of the object to be magnetized, sufficient Magnetic force is generated.
F: Taking out the object to be magnetized After the completion of magnetization, the holding member 22 is further raised, and the object to be magnetized 20 is taken out of the magnetized portion 12 and taken out. This completes one magnetization cycle. Although depending on the size of the object to be magnetized 20, when the heat capacity is small with a very small diameter, magnetization can be performed in a cycle of about several seconds.

  In general, when moving the magnetized object from the heating unit to the magnetized part, the object to be magnetized cools down rapidly. In the present invention, the heating part and the magnetized part can be moved relative to each other, and the heating part and the magnetized part can be in close contact with each other. And a to-be-magnetized object is transferred to a magnetizing part from a heating part at the time of contact | adherence. The close contact between the heating part and the magnetized part can suppress the excessive temperature drop of the magnetized object during transfer, and the moving distance of the magnetized object is shortened, so the moving time is shortened and high speed operation is possible. As a result, productivity is improved. Further, in the normal state, since the heating part and the magnetized part are separated from each other, the magnetized part is not excessively heated.

  Through the series of operations described above, a magnetic pole corresponding to the magnetized magnetic pole appears on the outer peripheral surface of the ring-shaped permanent magnet, which is an object to be magnetized, and a permanent magnet that is sufficiently magnetized at room temperature can be obtained. FIG. 4 shows the situation of multipolar magnetization applied to the ring-shaped permanent magnet that is the product 50.

  FIG. 5 is a longitudinal sectional view showing another embodiment of the magnetizing apparatus according to the present invention. This magnetizing apparatus also includes a heating unit 10 having a cylindrical structure and an inner peripheral surface serving as a heating surface, and a magnetizing unit 12 having a cylindrical structure and an inner peripheral surface serving as a magnetized surface, which are separately provided. And, it is arranged in the axial direction. In this example, the heating unit 10 and the magnetized unit 12 are arranged side by side, and the direction of the axis is horizontal. The heating unit 10 and the magnetized unit 12 are supported so as to be relatively close to and away from each other. A cooling unit 16 is provided on the outer peripheral side of the magnetized unit 12. On the other hand, a rod-shaped holding member 22 that holds the magnetized object 20 is installed so as to be movable in the axial direction through the heating unit 10 and the magnetized unit 12. In this configuration, since the magnetized portion 12 and the heating portion 10 are arranged side by side, the magnetized portion is not heated by natural convection or the like without providing a large separation distance. The object to be magnetized 20 is heated by the heating unit 10, and then the heating unit 10 and the magnetized part 12 are in close contact with each other, and the heated object to be magnetized 20 moves in the horizontal left hand direction and is magnetized by the magnetized part 12. Is done. In addition, illustration of the horizontal drive mechanism and control unit of the object to be magnetized is omitted.

FIG. 6 is a longitudinal sectional view showing still another embodiment of the magnetizing apparatus according to the present invention. This magnetizing apparatus also includes a heating unit 10 having a cylindrical structure and an inner peripheral surface serving as a heating surface, and a magnetizing unit 12 having a cylindrical structure and an inner peripheral surface serving as a magnetized surface, which are separately provided. And arranged in the axial direction. This example is a saddle arrangement type in which the magnetized portion 12 is positioned below and the heating portion 10 is positioned vertically so that the axis direction is vertical. The heating unit 10 and the magnetized unit 12 are supported so as to be relatively close to and away from each other. A cooling unit 16 is provided on the outer peripheral side of the magnetized unit 12. On the other hand, a rod-like holding member 22 that holds the magnetized object 20 is installed so as to be movable in the axial direction through the heating part and the magnetized part. In this configuration, since the magnetized part is located below the heating part, the magnetized part is not heated by natural convection or the like. Therefore, even in this configuration, it is not necessary to provide a large separation distance, and the magnetized portion and the heating portion can be arranged close to each other, so that the apparatus can be downsized.
The object to be magnetized 20 is heated by the heating unit 10, and then the heating unit 10 and the magnetized part 12 are in close contact with each other, and the heated object to be magnetized 20 is lowered and magnetized by the magnetized part 12.

  In addition to resistance heating as shown in the embodiments, any means such as high-frequency heating, laser heating, high-temperature gas flow heating, or high-temperature liquid heating may be used for heating. The cooling may be natural cooling or forced cooling such as water cooling or air cooling. If work in an inert atmosphere is required, an inert gas flow can also be performed. Further, the magnetizing method and the specific structure in the magnetized portion may be appropriately changed according to the diameter and material of the permanent magnet that is the magnetized object, the number of magnetized poles, and the like.

Explanatory drawing which shows one Example of the magnetizing apparatus which concerns on this invention. The horizontal sectional view which shows an example of the internal structure of a magnetization part. Operation | movement explanatory drawing of this magnetization apparatus. Explanatory drawing which shows the multipolar magnetization state to a ring-shaped permanent magnet. The longitudinal cross-sectional view which shows the other Example of the magnetizing apparatus which concerns on this invention. The longitudinal cross-sectional view which shows further another Example of the magnetizing apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Heating part 12 Magnetization part 14 Heat insulation member 16 Cooling part 20 Magnetized object 22 Holding member 24,26 Vertical drive mechanism 28 Control part

Claims (4)

The inner peripheral surface a tubular structure and a heating unit you heat the ring-shaped deposition磁物I Do and the heating surface, I Do a magnetized surface without the peripheral surface wears tubular structure to be magnetized and a magnetized portion for performing multiple poles on the outer peripheral surface to apply a magnetizing magnetic field to the object, as well as axially disposed separately structure, relatively close-and the magnetized portion and the heating portion spaced freely supported, it is installed axially moveable relative to and is rod-shaped holding member for holding the ring-shaped deposition磁物through said heating unit and the magnetized portion, the adhesive wherein within said heating portion in a state that is separated from the magnet portion deposited磁物is heated to approximate the magnetized portion and the heating portion in a state where該被adhesive磁物is heated, then the deposition磁物in the heating unit is transferred into the magnetized portion, the magnetized portion and the heating portion is separated, characterized in that so as to magnetized in the magnetized portion multipolar Magnetizing apparatus of the ring-shaped permanent magnet. The means for generating the magnetizing magnetic field is a permanent magnet, and the magnetized portion is provided with a circular magnetized object receiving hole in which a magnetized object can be inserted / extracted at the center of the non-magnetic block, A structure in which a plurality of grooves extending radially from the inner wall surface of the magnetized object receiving hole are provided at equal angles, and a permanent magnet for magnetization having a Curie point higher than that of the object to be magnetized is embedded in each groove. Item 2. A magnetizing device for a multipolar ring-shaped permanent magnet according to Item 1 . It said magnetized portion and the heating portion is arranged vertically, magnetizing apparatus of the multipolar ring-shaped permanent magnet according to claim 1 or 2, wherein the direction of the axis is vertical arrangement format is vertical. Wherein the heating portion magnetized are side by side, the magnetizing apparatus of the multipolar ring-shaped permanent magnet according to claim 1 or 2, wherein the direction of the axis is transverse arrangement form a horizontal.

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