Method for manufacturing a permanent magnet

Abstract

To provide a manufacturing method of a permanent magnet capable of obtaining high magnetization characteristics even when multipolar magnetization is performed on a rare earth iron magnet having magnetic anisotropy.SOLUTION: A manufacturing method of a permanent magnet includes a magnetization step of magnetizing an object to be magnetized by a magnetizing device 1 including a magnetic field unit 6 in which a plurality of magnetizing permanent magnets that generate a magnetic field for a magnetized object 100 are arranged at regular intervals, and a heating unit 4 that has a heating surface 4a facing the magnetized object in the axial direction of the magnetized object and heats the magnetized object. In the magnetization step, the magnetized object is placed on the magnetic field portion, and the heating unit heats the magnetized object to a temperature above the Curie point of the magnetized object and below the Curie point of the magnetizing permanent magnet, and then the magnetized object is heated so as to be cooled to a temperature below the Curie point, and a magnetizing magnetic field is applied to the magnetized object by a magnetizing permanent magnet.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a permanent magnet.

Background Art

[0002] Among rare earth iron-based magnets, especially Nd-Fe-B sintered magnets have high magnetic properties, so they are used in various devices, apparatuses, and motors. However, when an Nd-Fe-B sintered magnet is used in a high-temperature environment, the coercive force decreases due to demagnetization. Therefore, in order to cope with use in a high-temperature environment, heat resistance of the Nd-Fe-B sintered magnet is required. Generally, the coercive force of the magnet is increased to improve heat resistance, and it is known that the coercive force can be increased by refining the crystal grains of the magnet. As a method for improving the coercive force by refining the crystal grains of the magnet, a hot-worked magnet capable of refining the crystal grain size to be finer than that of a sintered magnet is known as an effective means (see, for example, Non-Patent Document 1). The crystal grain size of this hot-worked magnet is 1 / 10 to 1 / 100 of that of a sintered magnet, enabling refinement.

[0003] It is necessary to magnetize this hot-worked magnet, and a means of performing pulse magnetization on a magnet produced by hot working is known (see, for example, Patent Document 1). In the method for manufacturing a permanent magnet of Patent Document 1, a ribbon-like thin strip produced by a rapid cooling method is pulverized into a powder, and then a green compact is obtained by hot press working. The green compact is plastically deformed by backward extrusion at a temperature of 700°C to obtain a magnet material. And it is described that the magnet material is multi-pole magnetized with 8 poles at a temperature of 50°C or higher and below the Curie point using a magnetization device in which a coil having a magnetization yoke is connected to a pulse power source. The permanent magnet described in this Patent Document 1 is a hot-worked magnet described in Non-Patent Document 1 from its manufacturing method, and the magnetization device is a so-called pulse-type magnetization device. Patent Document 1 describes that when magnetized at room temperature and the magnetic properties of the permanent magnet were measured, the maximum energy product was 30 MG·Oe and the coercive force was 12100 (Oe).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Non-Patent Document

[0005]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, recently, the maximum energy product (MG·Oe) of hot-worked magnets has been increasing, and their coercivity has also become higher than 12100 (Oe). Therefore, with the magnetization method described in Patent Document 1, namely, the means of "magnetizing a magnet material at a temperature of 50°C or higher and below the Curie point using a magnetization device connected to a pulse power supply", there is a risk that high magnetization characteristics cannot be obtained for hot-worked magnets with high coercivity.

[0007] Also, recently, when used in a motor, multipolar magnetization is required to reduce the cogging torque of the motor, and when used as a sensor, to improve the resolution of the sensor. In the case of so-called pulse magnetization, where a coil is wound around a magnetization yoke and a pulse current is applied as in Patent Document 1, when the magnetization pitch becomes narrow, there are restrictions on the number of turns and coil diameter of the coil wound around the magnetization yoke, so there is a problem that the magnetization magnetic field cannot be increased and the magnetization pitch cannot be reduced.

[0008] In view of the above problems, an object of the present invention is to provide a method for manufacturing a permanent magnet that can obtain high magnetization characteristics even when performing multipolar magnetization on a rare earth iron-based magnet having magnetic anisotropy.

Means for Solving the Problems

[0009] In order to solve the above-described problems and achieve the object, a method for manufacturing a permanent magnet according to an aspect of the present invention includes a field magnet portion in which a plurality of magnetization permanent magnets that generate a magnetic field with respect to a magnetizable object are arranged at equal intervals, and a heating surface that faces the magnetizable object in the axial direction of the magnetizable object and heats the magnetizable object. A magnetization step of magnetizing the magnetizable object by a magnetization device having a heating unit, in the magnetization step, the magnetizable object is disposed on the field magnet portion, and the heating unit heats the magnetizable object to a temperature equal to or higher than the Curie point of the magnetizable object and lower than the Curie point of the magnetization permanent magnet, and then cools the magnetizable object to a temperature lower than the Curie point of the magnetizable object, and at the same time, applies a magnetization magnetic field to the magnetizable object by the magnetization permanent magnet. The magnetizable object is an anisotropic rare earth iron-based magnet having an average crystal grain size of 0.02 μm or more and 3.59 μm or less. In the field magnet portion, the permanent magnets are arranged such that the pole pitch in the magnetizable object that has undergone the magnetization step is 0.3 mm or more and 2.6 mm or less.

Effects of the Invention

[0010] According to an aspect of the present invention, even when multi-pole magnetization is performed on a rare earth iron-based magnet having magnetic anisotropy, a rare earth iron-based magnet having high magnetization characteristics can be provided.

Brief Description of the Drawings

[0011]

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DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to these examples.

[0013] <Manufacturing method of Embodiment 1> The manufacturing method of the permanent magnet of Embodiment 1 includes a magnetization step of magnetizing a magnetizable object by a magnetization device having a magnetic field generating portion in which a plurality of magnetization permanent magnets for generating a magnetic field with respect to the magnetizable object are arranged at equal intervals, and a heating portion having a heating surface facing the magnetizable object in the axial direction of the magnetizable object and heating the magnetizable object. In the magnetization step, the magnetizable object is placed on the magnetic field generating portion, and the magnetizable object is heated by the heating portion to a temperature equal to or higher than the Curie point of the magnetizable object and lower than the Curie point of the magnetization permanent magnet, and then cooled to a temperature lower than the Curie point of the magnetizable object, and at the same time, a magnetization magnetic field is applied to the magnetizable object by the magnetization permanent magnet. The magnetizable object is an anisotropic rare earth iron-based magnet having an average crystal grain size of 0.02 μm or more and 3.59 μm or less. In the magnetic field generating portion, the magnetization permanent magnets are arranged so that the pole pitch in the magnetizable object that has undergone the magnetization step is 0.3 mm or more and 2.6 mm or less.

[0014] In the magnetization step, magnetization is performed on the magnetizable object by a magnetization device. FIG. 1 is a diagram showing a schematic configuration example of the magnetization device used in Embodiment 1. FIG. 2 is a perspective view showing the magnetic field generating portion of the magnetization device used in Embodiment 1. FIG. 3 is a cross-sectional view showing the magnetizable object after magnetization. FIGS. 4 to 6 are operation explanatory views of the magnetization device used in Embodiment 1. Note that FIG. 3 is a cross-sectional view in a plane including the axial direction of the magnetizable object. Here, the X direction in each figure of this specification is the radial direction of the magnetizable object in Embodiment 1. The Z direction is the axial direction of the magnetizable object, which is the vertical direction, the Z1 direction is the upward direction, and the Z2 direction is the downward direction.

[0015] As shown in FIGS. 1 to 3, the magnetization device 1 used in Embodiment 1 magnetizes the object to be magnetized 100 and manufactures the object to be magnetized after magnetization (magnetized object after magnetization) 100'. The magnetization device 1 includes a gantry portion 2, a moving portion 3, a heating portion 4, a preheating portion 5, a magnetic field portion 6, a positioning pin 7, a cooling portion 8, and a control portion 10.

[0016] The gantry portion 2 is the base of the magnetization device 1, and at least the moving portion 3, the heating portion 4, the preheating portion 5, the magnetic field portion 6, the positioning pin 7, the cooling portion 8, and the control portion 10 are mounted thereon.

[0017] The moving portion 3 relatively moves the object to be magnetized 100 and the heating portion 4 between a non-heating position and a heating position in the axial direction. The moving portion 3 in Embodiment 1 includes a ceiling plate 31, an actuator 32, and a heating portion mounting base 33. The ceiling plate 31 is arranged spaced apart from the gantry portion 2 in the axial direction, and the actuator 32 and the heating portion mounting base 33 are fixed thereto. The actuator 32 relatively moves the ceiling plate 31 in the axial direction with respect to the gantry portion 2. The actuator 32 is a linear motion mechanism such as a hydraulic cylinder, for example, and is supplied with power by external power (not shown) and is driven and controlled by the control portion 10. A plurality of actuators 32 are arranged between the gantry portion 2 and the ceiling plate 31, for example, two or four are arranged. The heating portion mounting base 33 has the heating portion 4 fixed thereto and is fixed to the lower side surface of the ceiling plate 31.

[0018] The heating unit 4 performs magnetization heating on the adherend magnet 100. The heating unit 4 is made of a non-magnetic metal material, such as non-magnetic stainless steel, and heats the adherend magnet 100 to a temperature above the Curie point of the magnet that constitutes the adherend magnet 100. The heating unit 4 in Embodiment 1 is formed in a disc shape. Among the two surfaces in the vertical direction, the upper side surface is fixed to the heating unit mounting base 33 of the moving unit 3, and the lower side surface is the heating surface 4a. The heating surface 4a is formed with an outer diameter larger than the outer diameter of the adherend magnet 100 and faces the placement surface 6a (to be described later) of the field magnet portion 6 in the axial direction. That is, the heating surface 4a faces the adherend magnet 100 placed on the placement surface 6a in the axial direction. Also, the heating surface 4a contacts the adherend magnet 100 at the heating position. The heating unit 4 has one or more heaters, is supplied with power by external power (not shown), and is temperature-controlled by the control unit 10.

[0019] The preheating unit 5 performs preliminary heating on the adherend magnet 100. The preheating unit 5 is made of a non-magnetic metal material and heats the adherend magnet 100 to a temperature below the Curie point (a temperature higher than room temperature) of the magnet that constitutes the adherend magnet 100 before reaching the heating position. The preheating unit 5 in Embodiment 1 is formed in a columnar shape, and the field magnet portion 6 and the positioning pin 7 are fixed thereto. Here, the preheating unit 5 heats the adherend magnet 100 placed on the field magnet portion 6 via the field magnet portion 6 and the positioning pin 7. Among the two surfaces in the vertical direction of the preheating unit 5, the lower side surface is fixed to the gantry portion 2, and the upper side surface is the placement heating surface 5a. The placement heating surface 5a is formed larger than the outer diameter of the field magnet portion 6 and contacts the field magnet portion 6 and the positioning pin 7. The preheating unit 5 is supplied with power by external power (not shown), has one or more heaters, and is temperature-controlled by the control unit 10.

[0020] The field magnet part 6 generates a magnetic field with respect to the magnet-attached object 100. The field magnet part 6 in Embodiment 1 magnetizes the magnet-attached object 100 in the axial direction. The field magnet part 6 includes a main body part 61, a flange part 62, and permanent magnets 63 and 64. The main body part 61 is made of a non-magnetic metal material, formed in a cylindrical shape, and of the two surfaces in the vertical direction, the lower side surface is fixed to the mounting and heating surface 5a of the preheating part 5, and the upper side surface is a mounting surface 6a on which the magnet-attached object 100 is mounted. The main body part 61 is formed with an insertion hole 6b into which the positioning pin 7 is inserted. The flange part 62 is formed to protrude radially outward from the lower end part of the main body part 61. In a state where the field magnet part 6 is mounted on the mounting and heating surface 5a of the preheating part 5, a fixture, such as a fastening screw, is inserted into a through hole (not shown), and the fixture is fixed to the preheating part 5, thereby fixing the field magnet part 6 to the preheating part 5. The permanent magnets 63 and 64 are embedded in the upper end part of the main body part 61 and generate a magnetic field with respect to the magnet-attached object 100. The permanent magnets 63 and 64 are, for example, rectangular samarium cobalt magnets (Sm-Co magnets, Curie temperature is usually 750 °C or higher and 900 °C or lower). When viewed from the vertical direction, the permanent magnets 63 and 64 are formed concentrically around the center of the main body part 61. A plurality of the permanent magnets 63 are arranged at equal intervals in the circumferential direction on the inner side in the radial direction, and the permanent magnets 64 are arranged at equal intervals in the circumferential direction, radially spaced apart from the permanent magnets 63 on the outer side in the radial direction. The permanent magnets 63 and 64 have two magnetic poles (S pole, N pole) on the upper side and the lower side, and are embedded in the main body part 61 such that the magnetic poles are different alternately in the circumferential direction. Here, for the permanent magnets 63 and 64, the magnetic poles on the upper side (for example, S pole) are different from the magnetic poles on the upper side of the adjacent permanent magnets 63 and 64 in the circumferential direction (for example, N pole), and the magnetic poles on the lower side (for example, N pole) are different from the magnetic poles on the lower side of the adjacent permanent magnets 63 and 64 in the circumferential direction (for example, S pole). The number of the permanent magnets 63 and 64 to be embedded and the thickness in the circumferential direction are different in Embodiment 1, and the positions arranged in the circumferential direction, that is, the arrangement pitches are different. Note that the permanent magnets 63 and 64 are embedded in a state of being exposed on the mounting surface 6a with respect to the main body part 61, but may be embedded inside the main body part 61 without being exposed on the mounting surface 6a.More specifically, in the field magnet portion 6, the magnetization permanent magnets 63 and 64 are arranged such that the pole pitch in the magnetized object that has undergone the magnetization process is 0.3 mm or more and 2.6 mm or less, preferably 0.5 mm or more and 2.6 mm or less.

[0021] The positioning pin 7 is inserted into a through hole 100c (to be described later) of the magnetized object 100 in order to determine the position of the magnetized object 100 with respect to the field magnet portion 6 in the radial direction. The positioning pin 7 is inserted into the insertion hole 6b of the field magnet portion 6 in a state where the field magnet portion 6 is fixed to the preheating portion 5, and thus is fixed to the preheating portion 5.

[0022] The cooling unit 8 cools the magnetized object 100 heated by the heating unit 4. The cooling unit 8 in the first embodiment is fixed to the gantry portion 2 by a fixing member (not shown) and outputs air toward the magnetized object 100 placed on the field magnet portion 6. The cooling unit 8 is, for example, an air-cooling fan or a compressor that supplies compressed air, and cools the magnetized object 100 after heating by forced air cooling with high cooling efficiency instead of natural air cooling. The cooling unit 8 is supplied with power by external power (not shown) and is subjected to air supply control by the control unit 10.

[0023] The control unit 10 controls the magnetization device 1 in order to magnetize the magnet-attached object 100. The control unit 10 controls the moving unit 3, the heating unit 4, the preheating unit 5, and the cooling unit 8. By driving and controlling the moving unit 3, the control unit 10 relatively moves the heating unit 4 between the non-heating position and the heating position with respect to the magnet-attached object 100 placed on the field magnet unit 6. Here, the non-heating position is a position where the heating surface 4a is separated from the magnet-attached object 100 in the axial direction, and in the first embodiment, the heating surface 4a is non-contact with the magnet-attached object 100, and heating of the magnet-attached object 100 by the heating unit 4 is not performed (see FIG. 4). On the other hand, the heating position is a position where the heating surface 4a approaches the magnet-attached object 100 in the axial direction, and in the first embodiment, the heating surface 4a contacts the magnet-attached object 100, and heating of the magnet-attached object 100 by the heating unit 4 is performed (see FIG. 5). The control unit 10 heats the heating unit 4 so that the heating temperature becomes equal to or higher than the Curie point of the magnet constituting the magnet-attached object 100 by controlling the temperature of the heating unit 4. Specifically, in the first embodiment, before reaching the heating position, the heating unit 4 is heated so that the temperature is 30°C or higher and 350°C or lower with respect to the Curie point. The heating temperature is a temperature at which deterioration of the magnetic properties of the magnet constituting the magnet-attached object 100 can be suppressed. Here, the control unit 10 controls the pressing force applied to the magnet-attached object 100 by the heating unit 4 when the heating surface 4a contacts the magnet-attached object 100. When the heating surface 4a contacts the magnet-attached object 100, the control unit 10 drives and controls the moving unit 3 so that the pressing force can suppress damage to the magnet-attached object 100. Thereby, damage to the magnet-attached object 100 can be suppressed, and the contact state between the magnet-attached object 100 and the heating unit 4 can be made uniform. The control unit 10 heats the preheating unit 5 so that the preheating temperature becomes lower than the Curie point of the magnet constituting the magnet-attached object 100 before reaching the heating position by controlling the temperature of the preheating unit 5. Specifically, in the first embodiment, the preheating unit 5 is heated so that the temperature is 30°C or lower and 150°C or higher with respect to the Curie point. That is, the preferable range of the preliminary temperature T is T < T c , and the more preferable range of the preliminary temperature T is T ≤ T c -30. More specifically, 150°C ≤ T < T c , and even more specifically, 150°C ≤ T ≤ T c -30. Note that T cis the Curie point of the magnet that constitutes the adherend magnet 100. The control unit 10 cools the heated adherend magnet 100 after it changes from the heating position to the non-heating position by controlling the temperature of the cooling unit 8 (see Fig. 6).

[0024] Here, as shown in Figs. 1 and 3, the adherend magnet 100 and the adherend magnet 100' after magnetization are formed in a ring shape, and have a downward side surface 100a, an upward side surface 100b, a through hole 100c, and an outer peripheral surface 100d, which are both surfaces in the axial direction. The adherend magnet 100 is, for example, formed in a ring shape with an outer diameter of 10 mm or more, preferably an outer diameter of 15 mm or more and 50 mm or less.

[0025] The adherend magnet 100 contains an anisotropic rare earth iron-based magnet. As the anisotropic rare earth iron-based magnet, as the rare earth element (RE), it contains Nd and at least one selected from the group consisting of Sc, Y, La, Ce, Pr, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and an RE-Fe-B-based magnet containing 1 atomic % or more and 12 atomic % or less of B is preferable. Specifically, an Nd-Fe-B-based magnet using an Nd-Fe-B-based alloy having an Nd-Fe-B compound (for example, Nd2Fe 14 B) as the main phase is more preferable. According to such an Nd-Fe-B-based magnet, a permanent magnet with excellent magnetic properties can be obtained.

[0026] Further, in the Nd-Fe-B-based magnet, a part of iron (Fe) may be substituted with at least one element selected from, for example, Co, Ni, Ga, Cu, Al, Si, Ti, Mn, and Nb. Note that substituting a part of Fe with Co can improve the heat resistance. When a part of Fe is substituted with the above elements, from the viewpoint of preventing a decrease in magnetic properties, the substitution amount with respect to Fe is preferably less than 50 atomic %, and more preferably 35 atomic % or less. When such an anisotropic rare earth iron-based magnet is used, it can be strongly magnetized by the above-described magnetization device 1.

[0027] The anisotropic rare earth iron-based magnet has an average crystal grain size of 0.02 μm or more and 3.59 μm or less, and more preferably 0.29 μm or more and less than 3.59 μm.

[0028] The anisotropic rare earth iron-based magnet only needs to have magnetic anisotropy, and it may be a hot-worked magnet or a sintered magnet. The hot-worked magnet is manufactured, for example, by subjecting polycrystalline powder with a powder particle size of several tens of μm to hot working for orientation and high densification. The sintered magnet is manufactured, for example, by cold-forming and orienting single crystal powder with a powder particle size of several μm in a magnetic field and then undergoing high densification by sintering.

[0029] The Curie point of the magnetizable object 100 (the Curie point of the anisotropic rare earth iron-based magnet) is usually 250°C or higher and 400°C or lower.

[0030] In the magnetization process in Embodiment 1, the magnetizable object is disposed on the bias magnetic portion, and the heating unit heats the magnetizable object to a temperature equal to or higher than the Curie point of the magnetizable object and lower than the Curie point of the permanent magnet for magnetization, and then cools it to a temperature lower than the Curie point of the magnetizable object, while applying a magnetization magnetic field to the magnetizable object with the permanent magnet for magnetization. Hereinafter, this magnetization process will be described more specifically. Note that the magnetization device 1 is in a non-heated position. Also, the magnetizable object 100 is pre-formed into a ring shape according to the number of manufactured items. First, as shown in FIG. 1, the control unit 10 starts heating the heating unit 4 and the preheating unit 5. Here, the control unit 10 heats the heating unit 4 to the heating temperature and heats the preheating unit 5 to the preheating temperature. Next, the operator moves the magnetizable object 100 downward (arrow A in the figure) with the through hole 100c of the magnetizable object 100 facing the positioning pin 7 in the axial direction. Thereby, the magnetizable object 100 is placed on the placement surface 6a of the bias magnetic portion 6 as shown in FIG. 4. At this time, the operator positions the magnetizable object 100 with respect to the magnetization device 1 by inserting the upper end portion of the positioning pin protruding from the placement surface 6a of the bias magnetic portion 6 into the through hole 100c of the magnetizable object 100. Note that the upper side surface 100b of the magnetizable object 100 faces the heating surface 4a of the heating unit 4 in the axial direction.

[0031] Next, after the first predetermined time T1 has elapsed since the magnetizable object 100 was placed on the placement surface 6a, the control unit 10 moves the heating unit 4 with respect to the magnetizable object 100 from the non-heating position to the heating position by the moving unit 3 (arrow B in the figure). Here, the first predetermined time T1 refers to a sufficient time for the heating unit 4 to maintain the heating temperature and for the magnetizable object 100 placed on the placement surface 6a to receive heat from the preheating unit 5 via the magnetic field unit 6 until the magnetizable object 100 reaches a temperature higher than room temperature and lower than the Curie point. That is, the control unit 10 moves the heating unit 4 to the heating position with respect to the magnetizable object 100 after the heating unit 4 is at the heating temperature and the magnetizable object 100 is preheated at the non-heating position. Then, with the heating surface 4a in contact with the magnetizable object 100, heating of the preheated magnetizable object 100 is started. Note that when the heating unit 4 moves with respect to the magnetizable object 100 from the non-heating position to the heating position by the moving unit 3, the control unit 10 ends the heating of the preheating unit 5, that is, turns off the temperature control. Next, as shown in FIG. 5, the control unit 10 heats the magnetizable object 100 until it reaches a temperature equal to or higher than the Curie point with the heating surface 4a in contact with the magnetizable object 100. That is, the magnetizable object 100 is heated until it reaches a temperature equal to or higher than the Curie point and lower than the Curie point of the magnetization permanent magnet. Next, after the second predetermined time T2 has elapsed since the start of heating the magnetizable object 100 at the heating position, the control unit 10 moves the heating unit 4 with respect to the magnetizable object 100 from the heating position to the non-heating position by the moving unit 3 (arrow C in the figure). Here, the second predetermined time T2 refers to a sufficient time for the magnetizable object 100 to reach a temperature equal to or higher than the Curie point.

[0032] Next, as shown in FIG. 6, the control unit 10 cools the magnetizable object 100 by the cooling unit 8 at the non-heating position. Next, the control unit 10 ends the cooling by the cooling unit 8 after the third predetermined time T3 has elapsed since the start of cooling by the cooling unit 8 at the non-heating position. Here, the third predetermined time T3 refers to a sufficient time for the magnetizable object 100 to reach a temperature from equal to or higher than the Curie point to lower than the Curie point, preferably, 50°C below the Curie point, more preferably, 50°C or more lower than the Curie point.

[0033] Next, the operator takes out the magnetized object 100'. When the magnetizing device 1 newly magnetizes the object 100 to be magnetized, since the heating unit 4 is already heated, the control unit 10 starts the heating of the preheating unit 5.

[0034] As described above, in the manufacturing method of Embodiment 1, the object 100 to be magnetized is heated from below the Curie point to above the Curie point (and below the Curie point of the permanent magnet for magnetization), and while the magnetizing magnetic field is applied by the field magnet part 6, it is cooled from above the Curie point to below the Curie point. Thereby, the object 100 to be magnetized is magnetized, and the magnetized object 100' (permanent magnet) shown in FIG. 3 after magnetization is manufactured from the object 100 to be magnetized. Magnetization is performed on the magnetized object 100' after magnetization in regions corresponding to the permanent magnets 63 and 64 of the field magnet part 6, respectively. The magnetized object 100' after magnetization has magnetization regions 101 corresponding to each permanent magnet 63 and magnetization regions 102 corresponding to each permanent magnet 64 formed, that is, at least on the lower side surface 100a, it is a permanent magnet with two rows of multi-pole magnetization in a ring shape.

[0035] According to the manufacturing method of Embodiment 1, even when multi-pole magnetization is performed on a rare earth iron-based magnet having magnetic anisotropy, a permanent magnet having high magnetization characteristics can be obtained. Specifically, the magnetized object 100' after magnetization obtained by the manufacturing method of Embodiment 1 has a pole pitch of 0.3 mm or more and 2.6 mm or less, preferably 0.5 mm or more and 2.6 mm or less. Even in the case of a narrow pole pitch, high magnetization characteristics are shown. Here, the pole pitch in the ring-shaped magnetized object 100' after magnetization is the arc length between adjacent poles at the position actually used such as sensing. The position actually used such as sensing is usually 2.5 mm or more and 42.5 mm or less from the center of the ring represented by the magnetized object 100' after magnetization. On the other hand, when the magnetized object after magnetization having the above pitch is manufactured using the above object to be magnetized by conventional pulse magnetization, the magnetization characteristics are lower compared to the manufacturing method of Embodiment 1.

[0036] Note that after magnetization, the magnetizable object 100’ is heated by the heating unit 4 in the axial direction of the magnetizable object 100, that is, the heating surface 4a and the upper side surface 100b of the magnetizable object 100 are opposed to each other for heating. Therefore, among the two surfaces in the axial direction, the film thickness of the oxide film on the upper side surface 100b, which is one of the surfaces, becomes thicker than that on the outer peripheral surface 100d in the radial direction. As a result, it can be confirmed that in the magnetizable object 100’ after magnetization, the amount of Nd increases on the upper side surface 100b rather than on the outer peripheral surface 100d, and a large amount of segregation of Nd occurs.

[0037] In the manufacturing method of Embodiment 1, at the heating position, the heating surface 4a of the heating unit 4 is closer to the adherend magnet 100 in the axial direction than at the non-heating position, so that the adherend magnet 100 is heated by the heating unit 4 in the axial direction. Therefore, compared with the case where the adherend magnet 100 is heated in the radial direction by the heating unit 4, that is, with the heating surface 4a facing the outer peripheral surface 100d of the adherend magnet 100, when the adherend magnet 100 is heated in the axial direction, that is, with the heating surface 4a facing the upper side surface 100b of the adherend magnet 100, uneven heating of the adherend magnet 100 can be suppressed, and non-uniformity of heating of the adherend magnet 100 can be suppressed. In particular, a large adherend magnet 100 has a larger heat capacity than a small adherend magnet 100. A small adherend magnet 100 is easy to heat up and cool down, so it is difficult for a bias to occur in the temperature distribution in the adherend magnet 100. However, when the adherend magnet is large, for example, when the diameter is large, non-uniform heating is likely to occur in the adherend magnet 100. In the case of a large adherend magnet 100, in order to suppress the occurrence of non-uniform heating, it is possible to further increase the heating temperature or lengthen the second predetermined time T2, but there is a risk of deterioration of the magnetic characteristics of the magnet constituting the adherend magnet 100. However, in the manufacturing method of Embodiment 1, even for a large adherend magnet 100, since the adherend magnet 100 is heated in the axial direction, that is, with the heating surface 4a facing the upper side surface 100b of the adherend magnet 100, even if the heating temperature is not high and the second predetermined time T2 is not long, non-uniform heating of the adherend magnet 100 can be suppressed. Thereby, since the temperature non-uniformity of the adherend magnet 100 in the state where the magnetizing magnetic field is applied by the field magnet portion 6 can be suppressed, the uniformity of the magnetizing characteristics of the adherend magnet 100 can be achieved.

[0038] <Manufacturing Method of Embodiment 2> The method for manufacturing a permanent magnet according to Embodiment 2 includes a magnetization step of magnetizing a magnetizable object by using a magnetization device having a magnetic field generating unit in which a plurality of magnetization permanent magnets for generating a magnetic field with respect to the magnetizable object are arranged at equal intervals, and a heating unit having a heating surface facing the magnetizable object in the axial direction of the magnetizable object and heating the magnetizable object. In the magnetization step, the magnetizable object is placed on the magnetic field generating unit, and the heating unit heats the magnetizable object to a temperature equal to or higher than the Curie point of the magnetizable object and lower than the Curie point of the magnetization permanent magnet, and then cools it to a temperature lower than the Curie point of the magnetizable object, and at the same time, a magnetization magnetic field is applied to the magnetizable object by the magnetization permanent magnet. The magnetizable object is an anisotropic rare earth iron-based magnet obtained by hot working. In the magnetic field generating unit, the magnetization permanent magnets are arranged such that the pole pitch in the magnetizable object that has undergone the magnetization step is 0.3 mm or more and 3.1 mm or less.

[0039] Hereinafter, regarding the manufacturing method of Embodiment 2, the differences from the manufacturing method of Embodiment 1 will be described, and the same points will be omitted or simplified in the description. The magnetization device used in the manufacturing method of Embodiment 2 is different from the magnetization device 1 used in Embodiment 1 in the magnetic field generating unit. In the magnetic field generating unit used in Embodiment 2, the magnetization permanent magnets (specifically, permanent magnets 63 and 64) are arranged such that the pole pitch in the magnetizable object that has undergone the magnetization step is 0.3 mm or more and 3.1 mm or less, preferably 0.5 mm or more and 3.1 mm or less.

[0040] In Embodiment 2, the anisotropic rare earth iron-based magnet contained in the magnetizable object has magnetic anisotropy and is obtained by hot working. The hot-worked magnet is manufactured, for example, by subjecting polycrystalline powder with a powder particle size of several tens of μm to hot working to perform orientation and densification. The anisotropic rare earth iron-based magnet used in Embodiment 2 preferably has an average crystal grain size of 0.02 μm or more and 0.5 μm or less. The Curie point of the magnetizable object (the Curie point of the anisotropic rare earth iron-based magnet) is usually 250°C or higher and 400°C or lower.

[0041] Even by the manufacturing method of Embodiment 2, even when multi-pole magnetization is performed on a rare-earth iron-based magnet having magnetic anisotropy, a permanent magnet having high magnetization characteristics can be obtained. Specifically, the magnetized object obtained by the manufacturing method of Embodiment 2 has a pole pitch of 0.3 mm or more and 3.1 mm or less, preferably 0.5 mm or more and 3.1 mm or less. Even in the case of a narrow pole pitch, high magnetization characteristics are exhibited. Here, the pole pitch in the ring-shaped magnetized object is the arc length between adjacent poles at the position actually used such as sensing. On the other hand, when the magnetized object is used to produce a magnetized object having the above pitch by conventional pulse magnetization, the magnetization characteristics are lower compared to the manufacturing method of Embodiment 2.

[0042] <Modification Example 1> Regarding the manufacturing methods of Embodiments 1 and 2, the magnetization device may be changed to the following magnetization device. FIG. 7 is a diagram showing a schematic configuration example of the magnetization device used in Modification Example 1. FIGS. 8 to 10 are operation explanatory diagrams of the magnetization device used in Modification Example 1. Here, the X direction in each figure of this specification is the radial direction of the magnetized object in Modification Example 1. The Z direction is the axial direction of the magnetized object, which is the vertical direction, the Z1 direction is the upward direction, and the Z2 direction is the downward direction.

[0043] The difference between the magnetization device 1 used in Modification Example 1 and the magnetization device 1 used in Embodiments 1 and 2 is that a spacer 11 made of a non-magnetic material is placed on the magnetic field part 6, and the spacer 11 is interposed between the magnetic field part 6 and the magnetized object 100. Also, the magnetized object 100 is magnetized by the magnetic field part 6 via the spacer 11, which is different. Since the basic configuration of the magnetization device 1 used in Modification Example 1 is the same as the basic configuration of the magnetization device 1 used in Embodiments 1 and 2, the configurations with the same reference numerals will be omitted or simplified in the description.

[0044] The spacer 11 is a member that is placed on the placement surface 6a of the field magnet portion 6 and interposed between the field magnet portion 6 and the adherend magnet 100. The spacer 11 is formed in a ring shape from, for example, a non-magnetic metal material. Examples of materials that can be made thin from non-magnetic metal materials include non-magnetic stainless steel, titanium alloys, brass, etc., and the spacer 11 is preferably composed of these. Note that, since it is heated, it is not limited to non-magnetic metal materials as long as it has heat resistance of 350 °C or higher. For example, non-magnetic ceramics may also be used.

[0045] The outer diameter of this spacer 11 is the same as the placement surface 6a of the field magnet portion 6. Also, the axial thickness of the spacer 11 is preferably formed to be 0.7 mm or less, and more preferably formed to be 0.3 mm or less. If the spacer thickness becomes larger than 0.7 mm, it may become difficult to magnetize (magnetize) the adherend magnet. By interposing this non-magnetic metal material spacer 11 between the field magnet portion 6 and the adherend magnet 100, after the adherend magnet 100 is magnetized, the adsorption force between the magnetized adherend magnet 100' and the field magnet portion 6 can be reduced. As a result, the adherend magnet 100' can be easily removed from the field magnet portion 6. Furthermore, when removing the adherend magnet 100' from the field magnet portion 6, it is possible to prevent chipping from occurring in a part of the adherend magnet 100' and to prevent damage to the Sm-Co magnet, which is a permanent magnet exposed on the placement surface 6a of the field magnet portion 6, at the edge of the adherend magnet 100'.

[0046] Next, the magnetization process by the magnetization device 1 in Modification 1 will be described. Note that the magnetization device 1 is in the non-heating position. First, as shown in FIG. 8, the control unit 10 starts heating the heating unit 4 and the preheating unit 5. Here, the control unit 10 heats the heating unit 4 to the heating temperature and heats the preheating unit 5 to the preheating temperature. Next, the operator moves the magnetizable object 100 downward (arrow A in the figure) with the through hole 100c of the magnetizable object 100 and the positioning pin 7 facing each other in the axial direction. As a result, the magnetizable object 100 is placed on the spacer 11 placed on the mounting surface 6a of the field magnet portion 6 by being inserted into the positioning pin 7 as shown in FIG. 8. At this time, the operator positions the magnetizable object 100 with respect to the magnetization device 1 by inserting the upper end portion of the positioning pin protruding from the mounting surface 6a of the field magnet portion 6 and the spacer 11 into the through hole 100c of the magnetizable object 100.

[0047] Next, after the elapse of a first predetermined time T1 since the magnetizable object 100 is placed on the spacer 11 on the placement surface 6a, the control unit 10 moves the heating unit 4 with respect to the magnetizable object 100 from the non-heating position to the heating position by the moving unit 3 (arrow B in the figure). Here, the first predetermined time T1 means a time sufficient for the heating unit 4 to maintain the heating temperature and for the magnetizable object 100 placed on the spacer 11 to receive heat from the preheating unit 5 through the magnetic field unit 6 and the spacer 11 so that the magnetizable object 100 can reach a temperature below the Curie point higher than the normal temperature. That is, the control unit 10 moves the heating unit 4 to the heating position with respect to the magnetizable object 100 after the heating unit 4 is at the heating temperature and the magnetizable object 100 is preheated at the non-heating position. Then, with the heating surface 4a of the heating unit 4 in contact with the magnetizable object 100, the heating of the preheated magnetizable object 100 is started. Note that when the heating unit 4 moves with respect to the magnetizable object 100 from the non-heating position to the heating position by the moving unit 3, the control unit 10 ends the heating of the preheating unit 5, that is, turns off the temperature control. Next, as shown in FIG. 9, the control unit 10 heats the magnetizable object 100 until it reaches a temperature equal to or higher than the Curie point with the heating surface 4a of the heating unit 4 in contact with the magnetizable object 100. That is, the magnetizable object 100 is heated until it reaches a temperature equal to or higher than the Curie point and lower than the Curie point of the permanent magnet for magnetization. Next, after the elapse of a second predetermined time T2 since the start of heating the magnetizable object 100 at the heating position, the control unit 10 moves the heating unit 4 with respect to the magnetizable object 100 from the heating position to the non-heating position by the moving unit 3 (arrow C in the figure). Here, the second predetermined time T2 means a time sufficient for the magnetizable object 100 to reach a temperature equal to or higher than the Curie point.

[0048] Next, as shown in FIG. 10, the control unit 10 cools the magnetizable object 100 by the cooling unit 8 at the non-heating position. Next, after the elapse of a third predetermined time T3 since the start of cooling by the cooling unit 8 at the non-heating position, the control unit 10 ends the cooling by the cooling unit 8. Here, the third predetermined time T3 means a time sufficient for the magnetizable object 100 to reach a temperature from equal to or higher than the Curie point to lower than the Curie point, preferably, the Curie point minus 50°C.

[0049] Next, the operator takes out the magnetized object to be magnetized 100'. As described above, since the spacer 11 is interposed between the field magnet portion 6 and the object to be magnetized 100', the object to be magnetized 100' can be easily removed from the field magnet portion 6. Further, it is possible to prevent a part of the object to be magnetized 100' from chipping and to prevent damage to the Sm-Co magnet, which is a permanent magnet exposed on the mounting surface 6a of the field magnet portion 6.

[0050] According to the manufacturing method of Modification 1, as in Embodiments 1 and 2, even when multi-pole magnetization is performed on a rare-earth iron-based magnet having magnetic anisotropy, a permanent magnet having high magnetization characteristics can be obtained. Specifically, when using the same object to be magnetized as in Embodiment 1, the magnetized object to be magnetized obtained has a pole pitch of 0.3 mm or more and 2.6 mm or less, preferably 0.5 mm or more and 2.6 mm or less. In this case, in the field magnet portion, the permanent magnet for magnetization is arranged so that the pole pitch in the object to be magnetized that has undergone the magnetization process falls within the above range. Alternatively, when using the same object to be magnetized as in Embodiment 2, the magnetized object to be magnetized obtained has a pole pitch of 0.3 mm or more and 3.1 mm or less, preferably 0.5 mm or more and 3.1 mm or less. Also in this case, in the field magnet portion, the permanent magnet for magnetization is arranged so that the pole pitch in the object to be magnetized that has undergone the magnetization process falls within the above range.

[0051] <Modification 2> In the manufacturing methods of Embodiments 1 and 2, the case of performing magnetization in the axial direction on the object to be magnetized 100 has been described, but it is not limited thereto, and magnetization may be performed in the radial direction. FIG. 11 is a diagram showing a schematic configuration example of the magnetization device used in Modification 2. FIG. 12 is a perspective view showing the field magnet portion of the magnetization device used in Modification 2.

[0052] The difference between the magnetization device 1 used in Modification 2 and the magnetization devices 1 used in Embodiments 1 and 2 is that the field magnet portion 9 magnetizes the magnetizable object 100 in the radial direction. Also, the preheating portion 5 directly preheats the magnetizable object 100 instead of preheating it indirectly through the field magnet portion 9. Since the basic configuration of the magnetization device 1 used in Modification 2 is the same as the basic configuration of the magnetization devices 1 used in Embodiments 1 and 2, the components with the same reference numerals will be described with omissions or simplifications.

[0053] The heating portion 4 has a main body portion 41 and a protruding portion 42. The main body portion 41 is formed in a disc shape, and of the two surfaces in the vertical direction, the upper side surface is fixed to the heating portion mounting base 33 of the moving portion 3, and the protruding portion 42 protrudes downward from the lower side surface. The lower side surface of the protruding portion 42 in the vertical direction is the heating surface 4a. The heating surface 4a is configured to have a diameter smaller than the diameter of the insertion hole 9b of the field magnet portion 9.

[0054] The preheating portion 5 has an upper side surface that is the placement heating surface 5a and is formed in two stages. On the first stage on the upper side of the placement heating surface 5a, the magnetizable object 100 is placed and heated, and on the second stage on the lower side, the field magnet portion 9 is placed and heated.

[0055] The field magnet portion 9 generates a magnetic field with respect to the magnet-attached object 100. The field magnet portion 9 in the second modification magnetizes the magnet-attached object 100 in the radial direction and includes a main body portion 91, a flange portion 92, and a permanent magnet 93. The main body portion 91 is made of a non-magnetic metal material, formed in a cylindrical shape, and among the two surfaces in the vertical direction, the lower side surface is fixed to the second stage of the mounting and heating surface 5a of the preheating portion 5, and the upper side surface 9a faces the ceiling plate 31 in the axial direction. An insertion hole 9b into which the magnet-attached object 100 is inserted is formed in the main body portion 91. The flange portion 92 is formed to protrude radially outward from the lower end portion of the main body portion 91. In a state where the field magnet portion 9 is placed on the second stage of the mounting and heating surface 5a of the preheating portion 5, a fixture, such as a fastening screw, is inserted into a through hole (not shown), and the fixture is fixed to the preheating portion 5, thereby fixing the field magnet portion 9 to the preheating portion 5. The permanent magnet 93 is embedded on the side of the insertion hole 9b of the main body portion 91 in the radial direction, generates a magnetic field with respect to the magnet-attached object 100, and is, for example, a rectangular Sm-Co magnet. The permanent magnets 93 are formed concentrically around the center of the main body portion 91 when viewed from the vertical direction, and a plurality of them are arranged at equal intervals in the circumferential direction. The permanent magnet 93 has two magnetic poles (S pole, N pole) on the inner and outer sides in the radial direction, and is embedded in the main body portion 91 such that the magnetic poles are different alternately in the circumferential direction. Here, the magnetic pole (for example, S pole) on the inner side in the radial direction of the permanent magnet 93 is different from the magnetic pole on the inner side in the radial direction of the adjacent permanent magnet 93 in the circumferential direction (for example, N pole), and the magnetic pole (for example, N pole) on the outer side in the radial direction is different from the magnetic pole on the outer side in the radial direction of the adjacent permanent magnet 93 in the circumferential direction (for example, S pole). Note that the permanent magnet 93 is embedded in the main body portion 91 in a state of being exposed in the insertion hole 9b, but it may be embedded inside the main body portion 91 without being exposed in the insertion hole 9b.

[0056] Next, the magnetization process by the magnetizing device 1 in Modification 2 will be described. Parts that are the same as the magnetization process by the magnetizing device 1 in Embodiments 1 and 2 will be omitted or simplified in the description. First, the control unit 10 starts heating the heating unit 4 and the preheating unit 5. Next, the operator moves the magnetizable object 100 downward in the axial direction with the insertion hole 9b of the magnetizable object 100 and the field magnet part 9 facing each other, inserts the magnetizable object 100 into the insertion hole 9b of the field magnet part 9, and places it on the first stage of the placement heating surface 5a of the preheating unit 5. At this time, the operator positions the magnetizable object 100 with respect to the magnetizing device 1 by inserting the magnetizable object 100 into the insertion hole 9b. Note that the outer peripheral surface 100d of the magnetizable object 100 faces the field magnet part 9 in the radial direction, that is, the radial direction, and the upper side surface 100b faces the heating surface 4a of the heating unit 4 in the axial direction.

[0057] Next, after a first predetermined time T1 has elapsed since the magnetizable object 100 was placed on the placement heating surface 5a, the control unit 10 moves the heating unit 4 with respect to the magnetizable object 100 from the non-heating position to the heating position by the moving unit 3, starts heating the preheated magnetizable object 100, and after a second predetermined time T2 has elapsed since the heating of the magnetizable object 100 was started at the heating position, the control unit 10 moves the heating unit 4 with respect to the magnetizable object 100 from the heating position to the non-heating position by the moving unit 3. The control unit 10 cools the magnetizable object 100 by the cooling unit 8 at the non-heating position, and ends the cooling by the cooling unit 8 after a third predetermined time T3 has elapsed since the start of the cooling by the cooling unit 8 at the non-heating position. Next, the operator takes out the magnetized magnetizable object 100'.

[0058] As described above, in the manufacturing method of Modification 2, the magnetizable object 100 is heated from a temperature below the Curie point to a temperature equal to or higher than the Curie point (and lower than the Curie point of the magnetization permanent magnet), and while the magnetization magnetic field is applied by the field magnet part 9, it is cooled from a temperature equal to or higher than the Curie point to a temperature below the Curie point. Thereby, magnetization is performed on the magnetizable object 100, and the magnetizable object after magnetization (permanent magnet) is manufactured from the magnetizable object 100. Magnetization of the magnetizable object after magnetization is performed in regions corresponding to the permanent magnets 93 of the field magnet part 9 respectively. The magnetizable object after magnetization in Modification 2 is a permanent magnet magnetized with multiple poles in one row, that is, at least on the outer peripheral surface 100d, where magnetization regions corresponding to the respective permanent magnets 93 are formed.

[0059] According to the manufacturing method of Modification 2, similar to Embodiments 1 and 2, even when multi-pole magnetization is performed on a rare-earth iron-based magnet having magnetic anisotropy, a permanent magnet having high magnetization characteristics can be obtained. Specifically, when using a magnetizable object similar to that of Embodiment 1, the magnetizable object after magnetization obtained has a pole pitch of 0.3 mm or more and 2.6 mm or less, preferably 0.5 mm or more and 2.6 mm or less. In this case, in the field magnet part, the magnetization permanent magnets are arranged so that the pole pitch in the magnetizable object that has undergone the magnetization process falls within the above range. Alternatively, when using a magnetizable object similar to that of Embodiment 2, the magnetizable object after magnetization obtained is 0.3 mm or more and 3.1 mm or less, preferably 0.5 mm or more and 3.1 mm or less. Also in this case, in the field magnet part, the magnetization permanent magnets are arranged so that the pole pitch in the magnetizable object that has undergone the magnetization process falls within the above range. Here, the pole pitch in the ring-shaped magnetizable object after magnetization is the arc length between adjacent poles in the circumferential direction of the upper side surface 100b.

[0060] In addition, in the above-described embodiments and modifications, although the heating part 4 reaches the heating temperature before reaching the heating position, it is not limited thereto, and it may be heated to a standby temperature lower than the heating temperature at the non-heating position, and at the heating position, the temperature may be raised from the standby temperature to the heating temperature in a state where the heating surface 4a is in contact with the magnetizable object 100.

[0061] In the above-described embodiments and modified examples, the magnetizable object is in a ring shape, but it is not limited thereto and may be in a rod shape. In this case, by making the shape of the field part of the magnetization device also in a rod shape, a magnetizable object after magnetization in a rod shape can be obtained.

[0062] [Example] [Calculation model] As a calculation model, multi-pole magnetization from the outer periphery of a ring magnet with an outer diameter of Φ10 mm / inner diameter of Φ1.0 mm (wall thickness 4.5 mm) was assumed. As shown in Table 1, the number of magnetization poles (60 poles to 10 poles) was set to determine the pole pitch (0.5 mm to 3.1 mm).

[0063]

Table 1

[0064] For each of them, the magnetization index represented by the following formula was calculated. Magnetization index [-] = Maximum value of surface magnetic flux [mT] at each magnetization pitch / Remanent magnetic polarization Jr [T] of the magnetizable magnet It should be noted that the larger the value of the magnetization index calculated by the above formula, the better the magnetization characteristics. Also, correction was performed using the actually measured magnetization rate for each material of the magnetizable object.

[0065] [Experimental example 1-1] In Experimental example 1-1, the magnetization index was calculated for the case of the method for manufacturing a permanent magnet described in Embodiment 1. Specifically, the magnetization index was calculated for the following cases. Magnetization device: The magnetization device shown in Fig. 1. However, in the field part, it was assumed that the permanent magnet 63 in Fig. 2 was not arranged and only the permanent magnet 64 was arranged. Permanent magnet for magnetization: Samarium cobalt magnet (Sm-Co magnet). Magnetization conditions: It was assumed that the magnetization magnetic field was applied while heating up to 330 °C (temperature of Curie point + 15 °C) and cooling down to 150 °C (temperature lower than Curie point - 50 °C). Magnetized object: Assume a magnetized object containing anisotropic rare earth iron-based magnets (Nd-Fe-B-based magnets) with average crystal grain sizes of 0.29 μm, 1.50 μm, 2.50 μm, 3.59 μm, 5.37 μm, and 6.23 μm.

[0066] [Experimental Example 1-2] In Experimental Example 1-2, the magnetization index was calculated for the case of the conventional method for manufacturing permanent magnets by pulse magnetization. Magnetization fixture: For the dimensions of the magnetization fixture required for the calculation, empirically reasonable values were set. Magnetization conditions: As general production conditions (maximum values), the current density was set to 16 kA / mm 2 . Magnetized object: Assume a magnetized object containing anisotropic rare earth iron-based magnets (Nd-Fe-B-based magnets) with average crystal grain sizes of 0.29 μm, 1.50 μm, 2.50 μm, 3.59 μm, 5.37 μm, and 6.23 μm.

[0067] For Experimental Examples 1-1 and 1-2, for each pole pitch, the values of the calculated magnetization index with respect to the average crystal grain size were summarized. That is, FIGS. 13 to 19 are diagrams showing the calculated values of the magnetization index with respect to the average crystal grain size when the pole pitches are 0.5 mm, 0.8 mm, 1.0 mm, 1.6 mm, 2.0 mm, 2.6 mm, and 3.1 mm. From these figures, in the method for manufacturing a permanent magnet using the magnetization device shown in FIG. 1, it can be seen that when the following Conditions 1 and 2 are satisfied, particularly excellent magnetization characteristics are exhibited as compared with the conventional method for manufacturing a permanent magnet by pulse magnetization. Condition 1 "The permanent magnets for magnetization in the field magnet part are arranged such that the pole pitch in the magnetized object obtained in the magnetization process is 0.3 mm or more and 2.6 mm or less, preferably 0.5 mm or more and 2.6 mm or less." Condition 2 "The average crystal grain size of the magnetized object is an anisotropic rare earth iron-based magnet of 0.02 μm or more and 3.59 μm or less, preferably 0.29 μm or more and less than 3.59 μm."

[0068] [Experimental Example 2-1] In Experimental Example 2-1, the magnetization index was calculated for the case of the method for manufacturing a permanent magnet described in Embodiment 2. Specifically, the magnetization index was calculated for the following cases. Magnetizing device: The magnetizing device shown in FIG. 1. However, in the field magnet section, it was assumed that only the permanent magnet 64 was arranged and the permanent magnet 63 in FIG. 2 was not arranged. Permanent magnet for magnetization: Samarium cobalt magnet (Sm-Co magnet). Magnetization condition: It was assumed that the magnetization magnetic field was applied while heating up to 330 °C (temperature of Curie point + 15 °C) and cooling down to 150 °C (temperature lower than Curie point - 50 °C). Magnetized object: It was assumed that the magnetized object included an anisotropic rare earth iron-based magnet (Nd-Fe-B-based magnet) of a hot-worked magnet (average crystal grain size 0.29 μm).

[0069] [Experimental Example 2-2] In Experimental Example 2-2, the magnetization index was calculated for the case of the conventional method for manufacturing a permanent magnet by pulse magnetization. Magnetizing jig: For the dimensions of the magnetizing jig required for the calculation, empirically reasonable values were set. Magnetization condition: As general production conditions (maximum value), the current density was set to 16 kA / mm 2 to. Magnetized object: It was assumed that the magnetized object included an anisotropic rare earth iron-based magnet (Nd-Fe-B-based magnet) of a hot-worked magnet (average crystal grain size 0.29 μm).

[0070] For Experimental Examples 2-1 and 2-2, the calculated magnetization index values with respect to the pole pitch were summarized. That is, FIG. 20 is a diagram showing the calculated values of the magnetization index with respect to the pole pitch. From this figure, it can be seen that in the method for manufacturing a permanent magnet using the magnetizing device shown in FIG. 1, when the following Conditions 1 and 2 are satisfied, particularly excellent magnetization characteristics are exhibited as compared with the conventional method for manufacturing a permanent magnet by pulse magnetization. Condition 1 "The permanent magnet for magnetization in the field magnet section is arranged such that the pole pitch in the magnetized object obtained in the magnetization process is 0.3 mm or more and 3.1 mm or less, preferably 0.5 mm or more and 3.1 mm or less." Condition 2 "It is an anisotropic rare earth iron-based magnet obtained by hot working."

[0071] In addition, the measured values are also shown in FIG. 20. Specifically, for Experimental Example 2-1, the measured values when the pole pitch is 0.5 mm and 0.8 mm, and for Experimental Example 2-2, the measured values when the pole pitch is 1.6 mm and 2.0 mm are also shown. It can be seen that the calculated values obtained by the calculation model show a high correlation with the measured values.

Explanation of Signs

[0072] 1 Magnetizing device, 2 Mounting part, 3 Moving part, 4 Heating part, 4a Heating surface, 5 Preheating part, 6 Magnetic field part, 63, 64 Permanent magnets, 7 Positioning pin, 8 Cooling part, 9 Magnetic field part, 10 Control part, 11 Spacer, 100 Object to be magnetized, 100’ Magnetized object after magnetization, 100b Upper side surface (one surface)

Claims

1. A magnetization device includes a field magnet section in which a plurality of magnetization permanent magnets that generate a magnetic field for a magnetizable object are arranged at equal intervals, and a heating section that has a heating surface facing the magnetizable object in the axial direction of the magnetizable object and heats the magnetizable object. The magnetization process includes magnetizing the magnetizable object by the magnetization device. In the magnetization process, the magnetizable object is placed on the field magnet section, and the heating section heats the magnetizable object to a temperature equal to or higher than the Curie point of the magnetizable object and lower than the Curie point of the magnetization permanent magnet, and then cools it to a temperature lower than the Curie point of the magnetizable object while applying a magnetization magnetic field to the magnetizable object by the magnetization permanent magnet. The magnetizable object is an anisotropic rare earth iron-based magnet having an average crystal grain size of 0.02 μm or more and 3.59 μm or less. The anisotropic rare earth iron-based magnet is a hot-worked magnet manufactured by subjecting polycrystalline powder to hot working to perform orientation and densification, or a sintered magnet manufactured through densification by sintering. In the field magnet section, the magnetization permanent magnets are arranged such that the pole pitch in the magnetizable object obtained in the magnetization process is 0.3 mm or more and 2.6 mm or less. A method for manufacturing a permanent magnet.

2. A magnetization device includes a field magnet section in which a plurality of magnetization permanent magnets that generate a magnetic field for a magnetizable object are arranged at equal intervals, and a heating section that has a heating surface facing the magnetizable object in the axial direction of the magnetizable object and heats the magnetizable object. The magnetization process includes magnetizing the magnetizable object by the magnetization device. In the magnetization process, the magnetizable object is placed on the field magnet section, and the heating section heats the magnetizable object to a temperature equal to or higher than the Curie point of the magnetizable object and lower than the Curie point of the magnetization permanent magnet, and then cools it to a temperature lower than the Curie point of the magnetizable object while applying a magnetization magnetic field to the magnetizable object by the magnetization permanent magnet. The magnetizable object is an anisotropic rare earth iron-based magnet obtained by hot working. The anisotropic rare earth iron-based magnet is a hot-worked magnet manufactured by subjecting polycrystalline powder to hot working to perform orientation and densification. The average crystal grain size of the anisotropic rare earth iron-based magnet is 0.02 μm or more and 0.5 μm or less. In the field magnet section, the magnetization permanent magnets are arranged such that the pole pitch in the magnetizable object obtained in the magnetization process is 0.3 mm or more and 3.1 mm or less. Method for manufacturing a permanent magnet.

3. The number of magnetization poles in the magnetized object after magnetization is 12 or more and 60 or less. The method for manufacturing a permanent magnet according to claim 1.

4. The magnetized object after magnetization includes one surface in the axial direction and an outer peripheral surface facing the radial direction. and The thickness of the oxide film formed on the one surface is thicker than the thickness of the oxide film formed on the outer peripheral surface. The method for manufacturing a permanent magnet according to any one of claims 1 to 3.

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