JP7555232B2 - Magnetizing device - Google Patents

Description

The present invention relates to a magnetizing device and an object to be magnetized.

Conventionally, magnetic encoders are known for detecting the rotational position of equipment. This magnetic encoder is a magnetized object in which multiple magnetic poles (N pole, S pole) are magnetized in a predetermined magnetization pattern in the radial or axial direction relative to the direction of the rotation axis to form tracks. When magnetizing multiple magnetic poles (N pole, S pole) in such a predetermined magnetization pattern, a magnetization device using a coil current flow method is generally used. This coil current flow method magnetization device, for example, passes a pulse current through a field magnet section having a coil wound around a magnetization yoke, and magnetizes the object to be magnetized by the magnetic field generated by this (see, for example, Patent Document 1).

In response to the trend toward smaller magnetic encoders and higher resolution, when the permanent magnet to be magnetized is composed of a rare earth magnet with high magnetic properties (e.g., an Nd bonded magnet), the conventional coil current method using a pulse current requires a larger current to be passed, which can lead to problems such as larger size and higher cost of the magnetization device. In response to this, a magnetization device for a magnetized object is known in which the object is heated by a heating unit, and the temperature is lowered from a temperature above the Curie point of the magnetic powder that constitutes the object to be magnetized to a temperature below the Curie point, while a magnetic field is continuously generated by the permanent magnet in the field unit, thereby performing multi-pole magnetization (see, for example, Patent Document 2).

The magnetization device in Patent Document 2 is configured such that the heating unit 10 and the magnetization unit 12 are arranged in the axial direction as separate structures, the heating unit 10 and the magnetization unit 12 are supported so that they can be moved relatively close to or away from each other, and the holding member 22 for the object to be magnetized 20 is movable relatively to the heating unit 10 and the magnetization unit 12. The object to be magnetized 20 is heated in the radial direction by the heating unit 10 separated from the magnetization unit 12, the magnetization unit 12 and the heating unit 10 are brought close to each other while the object to be magnetized 20 remains heated, and then the object to be magnetized 20 is transferred to the magnetization unit 12 and magnetized in the radial direction, and the magnetization unit 12 and the heating unit 10 are separated from each other.

JP 2014-038939 A JP 2006-261460 A

Conventional magnetizing devices are useful for magnetizing small objects to be magnetized. This is because small objects to be magnetized heat up and cool down easily, so there is little risk of uneven temperature distribution in the object. On the other hand, when the object to be magnetized becomes large, its heat capacity increases, making it difficult to heat, and uneven heating of the object to be magnetized is likely to occur, which may result in a decrease in the uniformity of the magnetization characteristics of the object to be magnetized.

The present invention was made in consideration of the above circumstances, and aims to provide a magnetization device and a magnetized object that can suppress uneven heating of the magnetized object and achieve uniformity in the magnetization characteristics of the magnetized object.

In order to achieve the above object, the magnetization device of the present invention is characterized in that it comprises a field magnet section having a permanent magnet that generates a magnetic field for a ring-shaped object to be magnetized, and a plurality of the permanent magnets arranged at equal intervals in the circumferential direction, a heating section having a heating surface facing the object to be magnetized in the axial direction of the object to be magnetized and heating the object to a temperature equal to or higher than the Curie point of the magnetic powder constituting the object to be magnetized, a moving section that moves the object to be magnetized and the heating section relative to each other in the axial direction between a non-heating position and a heating position, and a control section that controls the field magnet section, the heating section, and the moving section, and the non-heating position is a position where the heating surface is separated from the object to be magnetized in the axial direction and the object to be magnetized is not heated by the heating section, and the heating position is a position where the heating surface is close to the object to be magnetized in the axial direction and the object to be magnetized is heated by the heating section.

In order to achieve the above object, the magnetized object of the present invention is a ring-shaped magnetized object that is magnetized while being heated by a magnetizing device, and is characterized in that, of both sides in the axial direction, one side has a thicker oxide coating than the outer peripheral surface in the radial direction.

The magnetization device and magnetized object of the present invention have the effect of suppressing non-uniform heating of the magnetized object and achieving uniformity in the magnetization characteristics of the magnetized object.

FIG. 1 is a diagram showing a schematic configuration example of a magnetizing device according to the first embodiment. FIG. 2 is a perspective view showing a field magnet portion of the magnetization device in the first embodiment. FIG. 3 is a cross-sectional view showing the object to be magnetized after it has been magnetized. FIG. 4 is an explanatory diagram of the operation of the magnetizing device in the first embodiment. FIG. 5 is an explanatory diagram of the operation of the magnetizing device in the first embodiment. FIG. 6 is an explanatory diagram of the operation of the magnetizing device in the first embodiment. FIG. 7 is a diagram illustrating an example of a schematic configuration of a magnetizing device according to the second embodiment. FIG. 8 is a diagram illustrating the operation of the magnetizing device in the second embodiment. FIG. 9 is an explanatory diagram of the operation of the magnetizing device in the second embodiment. FIG. 10 is a diagram illustrating the operation of the magnetizing device in the second embodiment. FIG. 11 is a diagram showing a schematic configuration example of a magnetizing device in a modified example. FIG. 12 is a perspective view showing a field magnet portion of a magnetizing device in a modified example. FIG. 13 shows the results of measuring the magnetic field (surface magnetic flux density) (mT) generated by the magnetized object 100 when four types of magnets were prepared as the magnetized object 100 and the thickness 11 of the spacer interposed between the magnetized object 100 and the field magnet portion 6 was changed.

Below, an embodiment of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to this embodiment. Furthermore, the components in the following embodiment include those that are easily replaceable by a person skilled in the art, or those that are substantially the same.

[Embodiment 1]
First, the magnetizing device and the object to be magnetized in the first embodiment will be described. FIG. 1 is a diagram showing an example of a schematic configuration of the magnetizing device in the first embodiment. FIG. 2 is a perspective view showing a field magnet part of the magnetizing device in the first embodiment. FIG. 3 is a cross-sectional view showing the object to be magnetized after magnetization. FIGS. 4 to 6 are explanatory diagrams for the operation of the magnetizing device in the first embodiment. FIG. 3 is a cross-sectional view in a plane including the axial direction of the object to be magnetized. Here, the X direction in each figure is the radial direction of the object to be magnetized in the first embodiment. The Z direction is the axial direction of the object to be magnetized, and is the up-down direction, with the Z1 direction being the upward direction and the Z2 direction being the downward direction.

As shown in Figs. 1 to 3, the magnetization device 1 in this embodiment 1 magnetizes the object to be magnetized 100 and produces the magnetized object 100'. The magnetization device 1 includes a stand unit 2, a moving unit 3, a heating unit 4, a preheating unit 5, a field magnet unit 6, a positioning pin 7, a cooling unit 8, and a control unit 10.

The stand 2 is the base of the magnetization device 1, and at least the moving part 3, the heating part 4, the preheating part 5, the field magnet part 6, the positioning pin 7, the cooling part 8, and the control part 10 are mounted on it.

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

The heating unit 4 applies magnetization heating to the magnetized object 100. The heating unit 4 is made of a non-magnetic metal material, such as non-magnetic stainless steel, and heats the magnetized object 100 to a temperature equal to or higher than the Curie point of the magnetic powder constituting the magnetized object 100. The heating unit 4 in this embodiment 1 is formed in a disk shape, and of the two sides in the vertical direction, the upper side is fixed to the heating unit mounting base 33 of the moving unit 3, and the lower side is the heating surface 4a. The heating surface 4a is formed with an outer diameter larger than the outer diameter of the magnetized object 100, and faces the later-described mounting surface 6a of the field magnet unit 6 in the axial direction. In other words, the heating surface 4a faces the magnetized object 100 placed on the mounting surface 6a in the axial direction. In addition, the heating surface 4a comes into contact with the magnetized object 100 at the heating position. The heating unit 4 has one or more heaters, is powered by an external power source (not shown), and the temperature is controlled by the control unit 10.

The preheating section 5 performs preliminary heating on the magnetized object 100. The preheating section 5 is made of a non-magnetic metal material, and heats the magnetized object 100 to a temperature lower than the Curie point (a temperature higher than room temperature) of the magnetic powder constituting the magnetized object 100 before it reaches the heating position. The preheating section 5 in this embodiment 1 is formed in a cylindrical shape, and the field magnet section 6 and the positioning pin 7 are fixed thereto. Here, the preheating section 5 heats the magnetized object 100 placed on the field magnet section 6 via the field magnet section 6 and the positioning pin 7. The preheating section 5 has two sides in the vertical direction, the lower side is fixed to the stand section 2, and the upper side is the mounting heating surface 5a. The mounting heating surface 5a is formed larger than the outer diameter of the field magnet section 6, and comes into contact with the field magnet section 6 and the positioning pin 7. The preheating unit 5 is supplied with power from an external power source (not shown), has one or more heaters, and the temperature is controlled by the control unit 10.

The field magnet portion 6 generates a magnetic field for the magnetized object 100. The field magnet portion 6 in this embodiment 1 magnetizes the magnetized object 100 in the axial direction and has a main body portion 61, a flange portion 62, and permanent magnets 63, 64. The main body portion 61 is made of a non-magnetic metal material and is formed in a cylindrical shape. Of the two sides in the vertical direction, the lower side is fixed to the mounting heating surface 5a of the preheating portion 5, and the upper side is the mounting surface 6a on which the magnetized object 100 is placed. The main body portion 61 is formed with an insertion hole 6b into which the positioning pin 7 is inserted. The flange portion 62 is formed to protrude radially outward from the lower end of the main body portion 61. With the field magnet portion 6 placed on the mounting and heating surface 5a of the preheating portion 5, a fastener, for example, a fastening screw is inserted into a through hole of the flange portion 62, and the fastener is fixed to the preheating portion 5, thereby fixing the field magnet portion 6 to the preheating portion 5. The permanent magnets 63, 64 are embedded in the upper end of the main body portion 61, and generate a magnetic field for the magnetized object 100, and are, for example, rectangular SmCo magnets. When viewed from the top and bottom direction, the permanent magnets 63, 64 are formed in concentric circles centered on the center of the main body portion 61, and a plurality of the permanent magnets 63 are arranged at equal intervals in the circumferential direction on the radially inner side, and a plurality of the permanent magnets 64 are arranged at equal intervals in the circumferential direction on the radially outer side, radially spaced from the permanent magnets 63. The permanent magnets 63, 64 have two magnetic poles (S pole, N pole) on the upper side and the lower side, and are embedded in the main body 61 so that the magnetic poles are alternately different in the circumferential direction. Here, the magnetic poles (e.g., S pole) on the upper side of the permanent magnets 63, 64 are different from the magnetic poles on the upper side of the adjacent permanent magnets 63, 64 in the circumferential direction (e.g., N pole), and the magnetic poles (e.g., N pole) on the lower side are different from the magnetic poles on the lower side of the adjacent permanent magnets 63, 64 in the circumferential direction (e.g., S pole). The permanent magnets 63, 64 in this embodiment 1 are different in the number of embedded magnets and the thickness in the circumferential direction, and the positions at which they are arranged in the circumferential direction, i.e., the arrangement pitch, are different. Note that the permanent magnets 63, 64 are embedded in the main body 61 in a state where they are exposed to the mounting surface 6a, but they may be embedded inside the main body 61 without being exposed to the mounting surface 6a.

The positioning pin 7 determines the position of the magnetized object 100 relative to the field magnet portion 6 in the radial direction, and is inserted into a through hole 100c (described later) of the magnetized object 100. The positioning pin 7 is fixed to the preheating portion 5 by being inserted into the insertion hole 6b of the field magnet portion 6 with the field magnet portion 6 fixed to the preheating portion 5.

The cooling unit 8 cools the magnetized object 100 heated by the heating unit 4. The cooling unit 8 in this embodiment 1 is fixed to the stand unit 2 by a fixing member (not shown), and outputs air toward the magnetized object 100 placed on the field magnet unit 6. The cooling unit 8 is, for example, an air-cooled fan or a compressor that supplies compressed air, and cools the magnetized object 100 after heating by forced air cooling, which has high cooling efficiency, rather than natural air cooling. The cooling unit 8 is supplied with power from an external power source (not shown), and the air supply is controlled by the control unit 10.

The control unit 10 controls the magnetization device 1 to magnetize the object 100 to be magnetized. The control unit 10 controls the moving unit 3, the heating unit 4, the preheating unit 5, and the cooling unit 8. The control unit 10 drives and controls the moving unit 3 to move the heating unit 4 between a non-heating position and a heating position relative to the object 100 to be magnetized placed on the field magnet unit 6. Here, the non-heating position is a position where the heating surface 4a is separated from the object 100 to be magnetized in the axial direction, where the heating surface 4a is not in contact with the object 100 to be magnetized in the first embodiment, and where the heating unit 4 does not heat the object 100 to be magnetized (see FIG. 4). On the other hand, the heating position is a position where the heating surface 4a is close to the object 100 to be magnetized in the axial direction, where the heating surface 4a is in contact with the object 100 to be magnetized in the first embodiment, and where the heating unit 4 heats the object 100 to be magnetized (see FIG. 5). The control unit 10 controls the temperature of the heating unit 4 so that the heating temperature is equal to or higher than the Curie point of the magnetic powder constituting the magnetized object 100, and in this embodiment 1, the heating unit 4 is heated to a temperature that is 30° C. higher than the Curie point and 350° C. lower than the Curie point before the heating position is reached. The heating temperature is a temperature that can suppress the occurrence of deterioration of the magnetic properties of the magnetic powder constituting the magnetized object 100 and deterioration of the thermosetting resin described later. Here, the control unit 10 controls the pressing force of the heating unit 4 against the magnetized object 100 when the heating surface 4a contacts the magnetized object 100. The control unit 10 drives and controls the moving unit 3 so that the pressing force is sufficient to suppress damage to the magnetized object 100 when the heating surface 4a contacts the magnetized object 100. This makes it possible to suppress damage to the magnetized object 100 and to uniform the contact state between the magnetized object 100 and the heating unit 4. The control unit 10 controls the temperature of the preheating unit 5, thereby heating the preheating unit 5 to a preheat temperature lower than the Curie point of the magnetic powder constituting the object to be magnetized 100, which in the present embodiment 1 is a temperature that is 30° C. lower than the Curie point and 150° C. or higher, before the object to be magnetized reaches the heating position. That is, a preferable range of the preheating temperature T is T<T _c , and a more preferable range of the preheating temperature T is T≦T _c -30. More specifically, 150° C.≦T<T _c , and even more specifically, 150° C.≦T≦T _c -30. The control unit 10 controls the temperature of the cooling unit 8, thereby cooling the heated object to be magnetized 100 after the object to be magnetized moves from the heating position to the non-heating position (see FIG. 6 ).

Here, the magnetized object 100 and the magnetized object 100' after magnetization are formed in a ring shape as shown in Figs. 1 and 3, and have a lower side surface 100a, an upper side surface 100b, a through hole 100c, and an outer peripheral surface 100d, which are both sides in the axial direction. The magnetized object 100 is a rare earth iron-based magnet before magnetization, and in this embodiment 1, for example, is formed by mixing magnetic powder containing neodymium (Nd-Fe-B), which is a magnetically isotropic rare earth iron-based magnet, and a thermosetting resin, for example, epoxy resin, in a predetermined ratio. The magnetized object 100 is not a small magnetized object, but a so-called large magnetized object, and is formed in a ring shape with an outer diameter of 10 mm or more, preferably an outer diameter of 15 mm to 50 mm.

The object to be magnetized 100 is preferably an anisotropic rare earth iron-based magnet with an average crystal grain size of 10 nm or more and 10,000 nm or less, and more preferably an anisotropic rare earth iron-based magnet with an average crystal grain size of 10 nm or more and 6,600 nm or less. When such an anisotropic rare earth iron-based magnet is used, it can be strongly magnetized by the magnetization device 1 described above.

Next, the magnetization method for the magnetized object 100 by the magnetization device 1 in this embodiment 1 will be described. The magnetization device 1 is in a non-heated position. The magnetized object 100 is formed into a ring shape in advance according to the number of pieces to be manufactured. First, the control unit 10 starts heating the heating unit 4 and the preheating unit 5 as shown in FIG. 1. 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 worker moves the magnetized object 100 downward in the axial direction with the through hole 100c of the magnetized object 100 facing the positioning pin 7 (arrow A in the same figure). As a result, the magnetized object 100 is placed on the placement surface 6a of the field magnet unit 6 as shown in FIG. 4. At this time, the worker positions the object 100 to be magnetized relative to the magnetization device 1 by inserting the upper end of the positioning pin protruding from the mounting surface 6a of the field magnet part 6 into the through hole 100c of the object 100 to be magnetized. Note that the upper side surface 100b of the object 100 to be magnetized faces the heating surface 4a of the heating part 4 in the axial direction.

Next, the control unit 10 moves the heating unit 4 from the non-heating position to the heating position relative to the magnetized object 100 by the moving unit 3 after the first predetermined time T1 has elapsed since the magnetized object 100 was placed on the placement surface 6a (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 magnetized object 100 placed on the placement surface 6a to receive heat from the preheating unit 5 via the field magnet unit 6 so that the magnetized object 100 can be heated to a temperature lower than the Curie point, which is higher than room temperature. In other words, the control unit 10 moves the heating unit 4 to the heating position relative to the magnetized object 100 after the heating unit 4 is at the heating temperature and the magnetized object 100 is preheated in the non-heating position, and starts heating the preheated magnetized object 100 with the heating surface 4a in contact with the magnetized object 100. When the heating unit 4 is moved from the non-heated position to the heated position relative to the magnetized object 100 by the moving unit 3, the control unit 10 ends the heating of the preheating unit 5, i.e., turns off the temperature control. Next, as shown in FIG. 5, the control unit 10 heats the magnetized object 100 until it reaches the Curie point or higher while the heating surface 4a is in contact with the magnetized object 100. Next, the control unit 10 moves the heating unit 4 from the heated position to the non-heated position relative to the magnetized object 100 by the moving unit 3 after a second predetermined time T2 has elapsed since the start of heating the magnetized object 100 at the heating position (arrow C in the figure). Here, the second predetermined time T2 refers to a sufficient time until the magnetized object 100 reaches the Curie point or higher.

Next, as shown in FIG. 6, the control unit 10 cools the magnetized object 100 by the cooling unit 8 in the non-heated position. Next, the control unit 10 ends the cooling by the cooling unit 8 after a third predetermined time T3 has elapsed since the start of cooling by the cooling unit 8 in the non-heated position. Here, the third predetermined time T3 refers to a sufficient time for the magnetized object 100 to go from above the Curie point to below the Curie point, preferably to the Curie point minus 50°C.

Next, the worker removes the magnetized object 100'. When the magnetizing device 1 is used to magnetize the object 100 again, the control unit 10 starts heating the preheating unit 5 since the heating unit 4 is already heated.

As described above, the magnetization device 1 in this embodiment 1 magnetizes the magnetized object 100 by raising the temperature of the magnetized object 100 from below the Curie point to above the Curie point, and then lowering the temperature from above the Curie point to below the Curie point while the magnetizing magnetic field is applied by the field magnetization section 6. As a result, the magnetization device 1 manufactures the magnetized object 100' after magnetization from the magnetized object 100, as shown in FIG. 3. The magnetized object 100' after magnetization is magnetized in the areas corresponding to the permanent magnets 63 and 64 of the field magnetization section 6. The magnetized object 100' after magnetization in this embodiment 1 is a permanent magnet in which the magnetization area 101 corresponding to each permanent magnet 63 and the magnetization area 102 corresponding to each permanent magnet 64 are formed, that is, at least on the lower side surface 100a, two rows of ring-shaped multi-pole magnetized permanent magnets are formed. Here, after magnetization, the magnetized object 100' is heated in the axial direction by the heating unit 4, i.e., the heating surface 4a is opposed to the upper side surface 100b of the magnetized object 100, so that the oxide film on one of the two surfaces in the axial direction, the upper side surface 100b, becomes thicker than the outer peripheral surface 100d in the radial direction. As a result, it was confirmed that the magnetized object 100' has a greater amount of Nd on the upper side surface 100b than on the outer peripheral surface 100d after magnetization, and there is a lot of Nd segregation.

In the magnetization device 1 in this embodiment 1, the heating surface 4a of the heating unit 4 is closer to the magnetized object 100 in the axial direction at the heating position than at the non-heating position, so that the heating unit 4 heats the magnetized object 100 in the axial direction. Therefore, compared to the case where the heating unit 4 heats the magnetized object 100 in the radial direction, that is, where the heating surface 4a faces the outer peripheral surface 100d of the magnetized object 100, the case where the magnetized object 100 is heated in the axial direction, that is, where the heating surface 4a faces the upper side surface 100b of the magnetized object 100, can suppress uneven heating of the magnetized object 100 and can suppress non-uniform heating of the magnetized object 100. In particular, a large magnetized object 100 has a larger heat capacity than a small magnetized object 100. Since a small object 100 to be magnetized heats up and cools down easily, the temperature distribution in the object 100 to be magnetized is unlikely to be biased, but when the object to be magnetized is large, for example, has a large diameter, the object 100 to be magnetized is likely to be heated non-uniformly. In the case of a large object 100 to be magnetized, it is possible to further increase the heating temperature or to lengthen the second predetermined time T2 in order to suppress the occurrence of non-uniform heating, but there is a risk of the magnetic properties of the magnetic powder constituting the object 100 to be magnetized and the thermosetting resin to be described later being deteriorated. However, the magnetizing device 1 in the first embodiment heats the object 100 to be magnetized in the axial direction, i.e., by facing the heating surface 4a and the upper side surface 100b of the object 100 to be magnetized, even if the object 100 to be magnetized is large, so that the non-uniform heating of the object 100 to be magnetized can be suppressed even if the heating temperature is not high and the second predetermined time T2 is not long. This makes it possible to suppress temperature unevenness in the object to be magnetized 100 when a magnetizing magnetic field is applied by the field magnet portion 6, thereby achieving uniformity in the magnetization characteristics of the object to be magnetized 100.

[Embodiment 2]
First, the magnetizing device and the object to be magnetized in the second embodiment will be described. Fig. 7 is a diagram showing a schematic configuration example of the magnetizing device in the second embodiment. Figs. 8 to 10 are diagrams explaining the operation of the magnetizing device in the second embodiment. Here, the X direction in each diagram is the radial direction of the object to be magnetized in the second embodiment. The Z direction is the axial direction of the object to be magnetized, that is, the up-down direction, with the Z1 direction being the up direction and the Z2 direction being the down direction.

The magnetization device 1 in embodiment 2 differs from the magnetization device 1 in embodiment 1 in that a spacer 11 made of a non-magnetic material is placed on the field magnet part 6, and the spacer 11 is interposed between the field magnet part 6 and the object to be magnetized 100. Another difference is that the object to be magnetized 100 is magnetized by the field magnet part 6 via the spacer 11. Note that the basic configuration of the magnetization device 1 in embodiment 2 is the same as the basic configuration of the magnetization device 1 in embodiment 1, so the configurations with the same reference numerals will be omitted or simplified in the description.

The spacer 11 is placed on the mounting surface 6a of the field magnet part 6 and is a member interposed between the field magnet part 6 and the magnetized object 100. The spacer 11 is formed, for example, in a ring shape from a non-magnetic metal material. Examples of non-magnetic metal materials that can be thinned include non-magnetic stainless steel, titanium alloy, brass, etc., and it is preferable that the spacer 11 is made of these. Note that since it will be heated, the material is not limited to non-magnetic metal materials as long as it has heat resistance of 350°C or more. For example, non-magnetic Secramix may be used.

The outer diameter of this spacer 11 is the same as the mounting surface 6a of the field magnet part 6. In addition, the axial thickness of the spacer 11 is preferably 0.7 mm or less, and more preferably 0.3 mm or less. If the spacer thickness is greater than 0.7 mm, it may be difficult to magnetize (magnetize) the magnetized object. By interposing this non-magnetic metal spacer 11 between the field magnet part 6 and the magnetized object 100, the attraction force between the magnetized object 100' and the field magnet part 6 can be reduced after magnetizing the magnetized object 100. As a result, the magnetized object 100' can be easily removed from the field magnet part 6. Furthermore, when removing the magnetized object 100' from the field magnet part 6, it is possible to prevent chipping of a part of the magnetized object 100' and damage to the SmCo magnet, which is a permanent magnet exposed on the mounting surface 6a of the field magnet part 6, by the edge of the magnetized object 100'.

Next, the magnetization method for the magnetized object 100 by the magnetization device 1 in the second embodiment will be described. The magnetization device 1 is in the non-heated position. First, the control unit 10 starts heating the heating unit 4 and the preheating unit 5 as shown in FIG. 8. Here, the control unit 10 heats the heating unit 4 to the heating temperature and the preheating unit 5 to the preheating temperature. Next, the worker moves the magnetized object 100 downward in the axial direction with the through hole 100c of the magnetized object 100 facing the positioning pin 7 (arrow A in the figure). As a result, the magnetized object 100 is inserted into the positioning pin 7 and placed on the spacer 11 placed on the mounting surface 6a of the field magnet unit 6 as shown in FIG. 8. At this time, the worker positions the object 100 to be magnetized relative to the magnetization device 1 by inserting the upper end of the positioning pin protruding from the mounting surface 6a of the field magnet part 6 and the spacer 11 into the through hole 100c of the object 100 to be magnetized.

Next, the control unit 10 moves the heating unit 4 from the non-heating position to the heating position relative to the magnetized object 100 by the moving unit 3 after the first predetermined time T1 has elapsed since the magnetized object 100 was placed on the spacer 11 on the placement surface 6a (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 magnetized object 100 placed on the spacer 11 to receive heat from the preheating unit 5 via the field magnet unit 6 and the spacer 11 so that the magnetized object 100 can be heated to a temperature lower than the Curie point, which is higher than room temperature. In other words, the control unit 10 moves the heating unit 4 to the heating position relative to the magnetized object 100 after the heating unit 4 is at the heating temperature and the magnetized object 100 is preheated in the non-heating position, and starts heating the preheated magnetized object 100 with the heating surface 4a in contact with the magnetized object 100. When the heating unit 4 is moved from the non-heated position to the heated position relative to the magnetized object 100 by the moving unit 3, the control unit 10 ends the heating of the preheating unit 5, i.e., turns off the temperature control. Next, as shown in FIG. 9, the control unit 10 heats the magnetized object 100 until it reaches the Curie point or higher while the heating surface 4a is in contact with the magnetized object 100. Next, the control unit 10 moves the heating unit 4 from the heated position to the non-heated position relative to the magnetized object 100 by the moving unit 3 after a second predetermined time T2 has elapsed since the start of heating the magnetized object 100 at the heating position (arrow C in the figure). Here, the second predetermined time T2 refers to a sufficient time until the magnetized object 100 reaches the Curie point or higher.

Next, as shown in FIG. 10, the control unit 10 cools the magnetized object 100 by the cooling unit 8 in the non-heated position. Next, the control unit 10 ends the cooling by the cooling unit 8 in the non-heated position after a third predetermined time T3 has elapsed since the cooling by the cooling unit 8 started. Here, the third predetermined time T3 refers to a sufficient time for the magnetized object 100 to go from above the Curie point to below the Curie point, preferably to the Curie point minus 50°C.

Next, the worker removes the magnetized object 100'. As described above, since the spacer 11 is interposed between the field magnet section 6 and the object 100' to be magnetized, the object 100' to be magnetized can be easily removed from the field magnet section 6. Furthermore, it is possible to prevent chipping of the object 100' to be magnetized and to prevent damage to the SmCo magnet, which is a permanent magnet exposed on the mounting surface 6a of the field magnet section 6.

[Modification]
In the magnetizing device 1 according to the first embodiment, the object 100 to be magnetized is magnetized in the axial direction. However, the present invention is not limited to this, and the object 100 may be magnetized in the radial direction.

Figure 11 is a diagram showing an example of the schematic configuration of a magnetizing device in a modified example. Figure 12 is a perspective view showing the field magnet part of the magnetizing device in the modified example. The magnetizing device 1 in the modified example differs from the magnetizing device 1 in embodiment 1 in that the field magnet part 9 is configured to magnetize the object 100 to be magnetized in the radial direction. Also, the preheating part 5 does not preheat the object 100 to be magnetized indirectly, i.e., via the field magnet part 9, but directly preheats it. Note that the basic configuration of the magnetizing device 1 in the modified example is the same as the basic configuration of the magnetizing device 1 in embodiment 1, so the configurations with the same reference numerals will be omitted or simplified in the description.

The heating unit 4 has a main body 41 and a protrusion 42. The main body 41 is formed in a disk shape, and of the two sides in the vertical direction, the upper side is fixed to the heating unit mounting base 33 of the moving unit 3, and the protrusion 42 is formed protruding downward from the lower side. The lower side of the protrusion 42 in the vertical direction is the heating surface 4a. The heating surface 4a is configured with a diameter smaller than the diameter of the insertion hole 9b of the field magnet unit 9.

The preheating section 5 has a two-stage structure with the upper side being the placement and heating surface 5a. On the first stage on the upper side of the placement and heating surface 5a, the object 100 to be magnetized is placed and heated, and on the second stage on the lower side, the field magnet section 9 is placed and heated.

The field magnet portion 9 generates a magnetic field for the magnetized object 100. The field magnet portion 9 in the modified example magnetizes the magnetized object 100 in the radial direction and has 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 and is formed in a cylindrical shape. Of the two sides in the vertical direction, the lower side is fixed to the second step of the mounting heating surface 5a of the preheating portion 5, and the upper side 9a faces the ceiling plate 31 in the axial direction. The main body portion 91 is formed with an insertion hole 9b into which the magnetized object 100 is inserted. The flange portion 92 is formed to protrude radially outward from the lower end of the main body portion 91. The flange portion 92 is configured to fix the field magnet portion 9 to the preheating portion 5 by inserting a fastener, such as a fastening screw, into a through hole (not shown) and fixing the fastener to the preheating portion 5 with the field magnet portion 9 placed on the second stage of the mounting heating surface 5a of the preheating portion 5. The permanent magnet 93 is embedded in the insertion hole 9b side of the main body portion 91 in the radial direction and generates a magnetic field for the magnetized object 100, and is, for example, a rectangular SmCo magnet. When viewed from the top and bottom, the permanent magnets 93 are formed in a concentric circle centered on the center of the main body portion 91, and are arranged at equal intervals in the circumferential direction. The permanent magnet 93 has two magnetic poles (S pole, N pole) on the radial inner side and the radial outer side, and is embedded in the main body portion 91 so that the magnetic poles are alternately different in the circumferential direction. Here, the magnetic pole (e.g., S pole) of the permanent magnet 93 on the radial inside is different from the magnetic pole (e.g., N pole) of the permanent magnet 93 adjacent in the circumferential direction on the radial inside, and the magnetic pole (e.g., N pole) of the permanent magnet 93 on the radial outside is different from the magnetic pole (e.g., S pole) of the permanent magnet 93 adjacent in the circumferential direction on the radial outside. Note that the permanent magnet 93 is embedded in the main body 91 in a state where it is exposed to the insertion hole 9b, but it may be embedded inside the main body 91 without being exposed to the insertion hole 9b.

Next, the magnetization method for the magnetized object 100 by the magnetization device 1 in the modified example will be described. Note that the same parts as those in the magnetization method by the magnetization device 1 in the first embodiment 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 worker moves the magnetized object 100 downward in the axial direction with the magnetized object 100 facing the insertion hole 9b of the field magnet unit 9, inserts the magnetized object 100 into the insertion hole 9b of the field magnet unit 9, and places it on the first stage of the heating placement surface 5a of the preheating unit 5. At this time, the worker positions the magnetized object 100 relative to the magnetization device 1 by inserting the magnetized object 100 into the insertion hole 9b. The outer peripheral surface 100d of the magnetized object 100 faces the field magnet portion 9 in the radial direction, and the upper side surface 100b faces the heating surface 4a of the heating portion 4 in the axial direction.

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

As described above, the magnetization device 1 in the modified example magnetizes the object 100 by raising the temperature of the object 100 to be magnetized from below the Curie point to above the Curie point, and then lowering the temperature from above the Curie point to below the Curie point while the magnetizing magnetic field is applied by the field magnetization section 9. In this way, the magnetization device 1 produces a magnetized object from the object 100 to be magnetized after magnetization. After magnetization, the object to be magnetized is magnetized in areas that correspond to the permanent magnets 93 of the field magnetization section 9. After magnetization, the object to be magnetized in the modified example is a permanent magnet in which magnetization areas corresponding to each permanent magnet 93 are formed, that is, at least on the outer circumferential surface 100d, a row of multi-pole magnetized magnetized magnets.

In addition, the magnetization device 1 in the modified example is provided with a permanent magnet magnetized with multiple poles in one row on the outer circumferential surface 100d of the object to be magnetized 100, but the permanent magnets 93 provided in the field magnet section 9 may be arranged coaxially and spaced apart in the axial direction in multiple rows (e.g., two rows). In this case, the outer circumferential surface 100d of the object to be magnetized 100 can be magnetized with multiple poles in multiple rows (e.g., two rows) in the axial direction.

In the above embodiment and modified example, the heating temperature is reached before the heating unit 4 reaches the heating position, but this is not limited to the above. The heating unit 4 may be heated to a standby temperature lower than the heating temperature in the non-heating position, and then heated from the standby temperature to the heating temperature in the heating position with the heating surface 4a in contact with the magnetized object 100.

[Example]
The magnetization device 1 according to the second embodiment was used to magnetize the object 100 to be magnetized. Specifically, the following spacer 11 and object 100 to be magnetized were used.
[Spacer 11]
・Material: SUS304
Shape: Ring shape (outer diameter φ30 mm, inner diameter φ15 mm, thickness (0.1 mm to 0.7 mm)
[Object to be magnetized 100]
Shape: Ring shape (outer diameter φ30 mm, inner diameter φ15 mm, thickness 1 mm)
-Magnetic pitch: 1.28 mm (64 poles), 0.95 mm (62 poles)
Two rows in the radial direction, magnetized in the circumferential direction
(64 poles on the outer row, 62 poles on the inner row)
Type (1) Anisotropic rare earth iron-based bulk magnet The magnet powder used was magnet powder for hot-processed anisotropic magnets (so-called MQ3 magnets) manufactured by Magnequench, which was made by crushing Nd-Fe-B isotropic magnet powder produced by the ultra-quenching method, hot-pressing the powder to increase density, and then hot-processing the powder to give it anisotropy. A spark plasma sintering (SPS) device was then used to hot-process the powder at a specified temperature to produce a magnet with anisotropy.
(2) Isotropic rare earth iron-based bulk magnet We used Nd-Fe-B isotropic magnet powder manufactured by Magnequench, Inc., produced by the ultra-rapid cooling method. Using a spark plasma sintering (SPS) device, we sintered this magnet powder at a specified temperature to produce an isotropic sintered magnet.
(3) Rare earth iron-based bonded magnet Nd-Fe-B isotropic magnet powder manufactured by Magnequench, Inc., was prepared by the ultra-rapid cooling method. The powder was mixed with epoxy resin, compressed, and then the epoxy resin was cured at a specified temperature to produce an isotropic rare earth iron-based bonded magnet.
(4) Sintered Neodymium Magnet A sintered neodymium magnet (Model N39UH, manufactured by Shin-Etsu Chemical Co., Ltd.) was machined to produce a ring-shaped magnet.
The above (1) and (4) are anisotropic magnets, while (2) and (3) are isotropic magnets.
The anisotropic rare earth iron-based bulk magnet had an average crystal grain size of 285 nm, and the neodymium sintered magnet had an average crystal grain size of 6700 nm.
Here, the average crystal grain size was determined as follows.
The main phase crystal grains of each magnet were observed using a scanning electron microscope (SEM).
Observation magnification: 1500 to 20000 times Observation conditions: Secondary electron image Observation direction: Easy magnetization direction Particle size confirmation method: Image processing (WinROOF, Mitani Shoji Co., Ltd.)
The SEM images measured under these conditions were loaded into particle analysis software, the particle area and perimeter were calculated, and the equivalent circle diameter was converted. Approximately 300 pieces of each magnet were measured, and the average equivalent circle diameter was taken as the average crystal grain size.

[Magnetic method]
The ring-shaped magnet produced in (1) above was set in a magnetizing device 1 and magnetized in the axial direction using a spacer 11 having a thickness of 0.1 mm.
The magnetization device 1 was in a non-heated position (FIG. 8). First, the control unit 10 started heating the heating unit 4 and the preheating unit 5 as shown in FIG. 8. Here, the control unit 10 heated the heating unit 4 to a heating temperature (350° C.) and the preheating unit 5 to a preheating temperature (200° C.). Next, the worker moved the object 100 to be magnetized downward in the axial direction with the through hole 100c of the object 100 facing the positioning pin 7 (arrow A in the figure). As a result, the object 100 to be magnetized was placed on the spacer 11 placed on the placement surface 6a of the field magnet unit 6 as shown in FIG. 8. At this time, the worker inserted the upper end of the positioning pin protruding from the placement surface 6a of the field magnet unit 6 and the spacer 11 into the through hole 100c of the object 100 to be magnetized, thereby positioning the object 100 to the magnetization device 1. The upper side surface 100b of the object 100 to be magnetized was opposed to the heating surface 4a of the heating unit 4 in the axial direction.
Next, the control unit 10 moved the heating unit 4 from the non-heating position to the heating position relative to the magnetized object 100 by the moving unit 3 after the magnetized object 100 was placed on the spacer 11 of the placement surface 6a and after the first predetermined time T1 (30 seconds) had elapsed (arrow B in the figure). The heating unit 4 was moved to the heating position relative to the magnetized object 100, and heating of the preheated magnetized object 100 was started with the heating surface 4a in contact with the magnetized object 100. When the heating unit 4 was moved from the non-heating position to the heating position relative to the magnetized object 100 by the moving unit 3, the control unit 10 ended heating of the preheating unit 5. Next, as shown in FIG. 9, the control unit 10 heated the magnetized object 100 to the Curie point or higher (330° C. (the Curie point is 315° C.)) with the heating surface 4a in contact with the magnetized object 100. Next, the control unit 10 moved the heating unit 4 from the heating position to the non-heating position relative to the magnetized object 100 by the moving unit 3 after a second predetermined time T2 (30 seconds) had elapsed since starting heating of the magnetized object 100 at the heating position (arrow C in the same figure).
Next, the control unit 10 caused the object to be magnetized 100 to be cooled by the cooling unit 8 at the non-heated position as shown in Fig. 10. Next, the control unit 10 stopped cooling by the cooling unit 8 at the non-heated position after a third predetermined time T3 (60 seconds) had elapsed since the start of cooling by the cooling unit 8. Here, the temperature of the object to be magnetized 100 had dropped from above the Curie point to 50°C below the Curie point.
Next, the worker removed the magnetized object 100'. Because the spacer 11 was interposed between the field magnet part 6 and the object 100', the object 100' could be easily removed from the field magnet part 6 without damaging the SmCo magnet, which is a permanent magnet exposed on the mounting surface 6a of the field magnet part 6.
The spacer thickness was changed (0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.7 mm) and magnetized in the same manner. The ring-shaped magnets (2) to (4) were also magnetized in the same manner.

[Surface magnetic flux density]
After magnetization, the surface magnetic flux density of the ring-shaped magnets (1) to (4) above was measured.
13 shows the results of measuring the magnetic field (surface magnetic flux density) (mT) generated by the magnetized object 100 when four types of magnets were prepared as the magnetized object 100 and the thickness of the spacer interposed between the magnetized object 100 and the field magnet portion 6 was changed. In FIG. 13, the graph for magnetization pitch: 0.95 mm shows the result of measuring the surface magnetic flux at a location corresponding to reference number 63 (0.95 mm) of the sample magnetized using the field magnet portion 6 in FIG. 2. In addition, the graph for magnetization pitch: 1.28 shows the result of measuring the surface magnetic flux at a location corresponding to reference number 64 (1.28 mm) of the sample magnetized using the field magnet portion 6 in FIG. 2. When the magnetization device 1 in the second embodiment was used, all of the ring-shaped magnets (1) to (4) were magnetized appropriately. 13, as the thickness of the spacer increases, the distance from the permanent magnet arranged in field portion 6 to the object 100 to be magnetized increases, and so the range over which the magnetic force from the permanent magnet arranged in field portion 6 affects the object 100 to be magnetized decreases, decreasing the generated magnetic field (surface magnetic flux density). When the spacer thickness is 0.1 mm, the value of the generated magnetic field (surface magnetic flux density) of the anisotropic rare earth iron-based bulk magnet is clearly large, while in comparison, the value of the generated magnetic field (surface magnetic flux density) of the neodymium sintered magnet is relatively small.
Furthermore, when the spacer thickness is 0.7 mm, the generated magnetic field (surface magnetic flux density) of the anisotropic rare earth iron bulk magnet, the isotropic rare earth iron bulk magnet, and the bonded magnet is approximately the same, at 100 mT to 110 mT. On the other hand, the generated magnetic field (surface magnetic flux density) of the neodymium sintered magnet is approximately 20 mT, a relatively low value.
As can be seen from Figure 13, when an anisotropic rare earth iron-based bulk magnet that has been given anisotropy by hot plastic working is magnetized in the axial direction, it is possible to obtain a strongly magnetized magnet even when multi-pole magnetization is performed with a narrow pitch. This is believed to be because the average crystal grain size of the anisotropic rare earth iron-based bulk magnet is between 10 nm and 6,600 nm.
Moreover, if the spacer thickness is greater than 0.7 mm, it may become difficult to magnetize (magnetize) the object to be magnetized. For this reason, the spacer thickness is preferably 0.7 mm or less, and more preferably 0.3 mm or less.

1 Magnetization device, 2 Stand section, 3 Moving section, 4 Heating section, 4a Heating surface, 5 Preheating section, 6 Field magnet section, 63, 64 Permanent magnet, 7 Positioning pin, 8 Cooling section, 9 Field magnet section, 10 Control section, 11 Spacer, 100 Object to be magnetized, 100' Object to be magnetized after magnetization, 100b Upper side surface (one side)

Claims (2)

a field magnet portion having a permanent magnet that generates a magnetic field toward a ring-shaped object to be magnetized, the permanent magnets being arranged at equal intervals in a circumferential direction;
a heating unit having a heating surface facing the object to be magnetized in the axial direction of the object to be magnetized and heating the object to a temperature equal to or higher than the Curie point of magnetic powder constituting the object to be magnetized;
a moving section that moves the object to be magnetized and the heating section relatively between a non-heating position and a heating position in an axial direction of the object to be magnetized;
A control unit that controls at least the heating unit and the moving unit;
Equipped with
the non-heating position is a position where the heating surface is separated from the object to be magnetized in the axial direction and the object to be magnetized is not heated by the heating unit,
the heating position is a position where the heating surface is close to the object to be magnetized in the axial direction and the object to be magnetized is heated by the heating unit,
a preheating section for heating the object to a temperature lower than the Curie point before the object reaches the heating position;
The control unit controls the preheating unit.
A magnetizing device characterized by: a spacer made of a non-magnetic material is placed on the field magnet portion, and the spacer is interposed between the field magnet portion and the object to be magnetized.
The magnetizing device according to claim 1 .

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