Magnetic body

Abstract

Provided is a magnetic body which comprises a plurality of magnetic particles, is cylindrical, and is provided with an end surface that extends radially and an outer circumferential surface that extends axially. The end surface has a plurality of magnetic poles in the axial direction. The end surface forms a reference surface. The residual magnetic flux density of the end surface in the axial direction is greater than the residual magnetic flux density of the outer circumferential surface in the radial direction. The relative density of the magnetic particles is more than 95%. Also provided is magnetic body which comprises a plurality of magnetic particles, is ring-shaped, and is provided with an end surface that extends radially and an outer circumferential surface and inner circumferential surface that extend axially. The end surface has a plurality of magnetic poles in the axial direction. The end surface forms a reference surface. The residual magnetic flux density of the end surface in the axial direction is greater than the residual magnetic flux density of the outer circumferential surface in the radial direction. The relative density of the magnetic particles is more than 95%.

Description

magnetic material

[0001] The present invention relates to a magnetic body.

[0002] Patent Document 1 describes a rare earth alloy binderless magnet and a method for manufacturing the same, which includes the steps of: (A) preparing a rare earth alloy rapidly solidified magnet powder; (B) cold compressing the rare earth alloy rapidly solidified magnet powder without a resin binder to form a compact in which the volume ratio of the rare earth alloy rapidly solidified magnet powder to the total is 70% to 95%; (C) heat treating the compact at a temperature of 350°C to 800°C to form a magnet; and (D) forming a vapor-phase metal plating film on the surface of the magnet.

[0003] JP 2007-129106 A

[0004] However, the rare earth alloy binderless magnet of Patent Document 1 has a problem in that the magnetic flux density is low when magnetized in multiple poles from the axial direction.

[0005] SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a magnetic body that is multi-pole magnetized in the axial direction and has excellent magnetic flux density.

[0006] In order to solve the above-mentioned problems and achieve the object, a magnetic body according to one aspect of the present invention includes a plurality of magnetic particles, is cylindrical, and has an end face extending in a radial direction and an outer peripheral surface extending in an axial direction, the end face having a plurality of magnetic poles in the axial direction, the end face forming a reference plane, the residual magnetic flux density of the end face in the axial direction being greater than the residual magnetic flux density of the outer peripheral surface in the radial direction, and the relative density of the magnetic particles being greater than 95%. The magnetic body according to one aspect of the present invention is a magnetic body magnetized in multiple poles from the axial direction, and has excellent magnetic flux density.

[0007] FIG. 1 is a diagram illustrating the magnetic body of embodiment 1. FIG. 2 is a diagram illustrating the magnetic body of embodiment 1. FIG. 3 is a diagram illustrating the magnetic body of embodiment 2. FIG. 4 shows the results of measuring the J-H curve for the hot-worked magnet obtained in step (b1) of Example 1. FIG. 5-1 is a diagram illustrating the evaluation magnetic body (A1) after magnetization. FIG. 5-2 is a diagram illustrating the evaluation magnetic body (A2) after magnetization. FIG. 6 shows the results of measuring the surface magnetic flux density for the evaluation magnetic bodies (A1) and (A2) obtained in Example 1. FIG. 7 shows the results of measuring the J-H curve for the hot-worked magnet obtained in step (b2) of Example 2. FIG. 8 shows the results of measuring the surface magnetic flux density for the evaluation magnetic bodies (A3) and (A4) obtained in Example 2.

[0008] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to these embodiments. Furthermore, the components in the following embodiments include those that are easily replaceable by those skilled in the art, or those that are substantially the same.

[0009] 1 and 2 are diagrams illustrating the magnetic body of the first embodiment. The magnetic body 1 includes a plurality of magnetic particles and is a magnet known as a binderless magnet or a bulk magnet. The magnetic body 1 is cylindrical. Specifically, the magnetic body 1 has an end face 11 extending in the radial direction X and an outer peripheral surface 12 extending in the axial direction Z. The end face 11 has a plurality of magnetic poles in the axial direction. For example, the end face 11 has four magnetic poles, and preferably has four or more magnetic poles. For this reason, the magnetic body 1 is suitable for use in an axial gap motor. The end face 11 also forms a reference surface. In this specification, the reference surface means a flat surface (plane). The residual magnetic flux density of the end face 11 in the axial direction Z is greater than the residual magnetic flux density of the outer peripheral surface 12 in the radial direction X. The magnetic body 1 has a relative density of magnetic particles exceeding 95%.

[0010] As described below, the magnetic body 1 is binderless and can be produced through a hot densification process, and the relative density of the magnetic particles exceeds 95%, and the residual magnetic flux density of the end surface 11 in the axial direction Z is greater than the residual magnetic flux density of the outer peripheral surface 12 in the radial direction X. Furthermore, the magnetic body 1 is a magnetic body magnetized in multiple poles from the axial direction, and has excellent magnetic flux density. In particular, the magnetic flux density is excellent even when the magnetizing current is low.

[0011] In magnetic body 1, the plurality of magnetic particles usually have portions oriented in a direction intersecting the axial direction Z. For this reason, magnetic body 1 is thought to have excellent magnetic flux density when multi-pole magnetized from the axial direction. Arrow A in FIG. 1 indicates the orientation direction of the above-mentioned portions of the plurality of magnetic particles. The fact that the plurality of magnetic particles have portions oriented in a direction intersecting the axial direction Z can be confirmed from the static magnetic properties. That is, when a J-H curve is measured for magnetic body 1, where the magnetic field is H and the magnetization of the magnet is J, this can be confirmed by the fact that the characteristics differ depending on the measurement direction.

[0012] Although Patent Document 1 describes a rare earth alloy binderless magnet, it does not disclose multi-pole magnetization.

[0013] Furthermore, the magnetic body 1 usually contains carbon, which is due to the polystyrene used in the compound preparation step (step (a)) in the manufacturing method of the magnetic body 1, as will be described later.

[0014] Here, we will explain the method for manufacturing the magnetic body 1. The method for manufacturing the magnetic body 1 includes, for example, steps (a) to (c).

[0015] In step (a), rare earth iron-based magnet powder (magnetic particles) and polystyrene are mixed to prepare a compound.

[0016] The rare earth iron-based magnet powder (magnetic particles) used is a rare earth iron-based magnet powder obtained by pulverizing a magnetically isotropic rare earth iron-based magnet ribbon produced by the rapid cooling method. The rare earth iron-based magnet powder produced by the rapid cooling method is usually flat in shape. The obtained rare earth iron-based magnet powder is also magnetically isotropic. The rare earth iron-based magnet powder preferably contains at least Nd as a rare earth element, and is, for example, an Nd—Fe—B-based magnet. The Nd—Fe—B-based magnet is a ternary tetragonal compound, Nd2Fe 14 The Nd—Fe—B magnet contains a B-type compound phase as the main phase. Furthermore, Nd—Fe—B magnets usually further contain a rare earth-rich phase (Nd-rich phase), etc. The Nd—Fe—B magnets may be used singly or in combination of two or more types.

[0017] The rare earth iron-based magnet powder (specifically, Nd—Fe—B-based magnet) may contain rare earth elements other than Nd. Examples of rare earth elements other than Nd include praseodymium (Pr), scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). The rare earth elements other than Nd may be used alone or in combination of two or more.

[0018] In Nd—Fe—B magnets, a portion of the Fe (usually less than 50 atomic %) may be substituted with Co. Furthermore, Nd—Fe—B magnets may contain other elements. Examples of such other elements include titanium (Ti), zirconium (Zr), niobium (Nb), molybdenum (Mo), hafnium (Hf), tantalum (Ta), tungsten (W), copper (Cu), and gallium (Ga). The other elements may be used alone or in combination of two or more.

[0019] The rare earth iron-based magnet powder is mixed with polystyrene to produce a compound. Since polystyrene does not contain oxygen atoms, it is unlikely to deteriorate the magnetic properties of the resulting magnetic body 1. In step (a), specifically, polystyrene is dissolved in an organic solvent to produce a resin solution. Here, any organic solvent can be used as long as it can dissolve polystyrene and evaporate during drying, as described below. Methyl ethyl ketone is preferably used as the organic solvent. The rare earth iron-based magnet powder and this resin solution are kneaded. Next, the kneaded mixture obtained by kneading is dried, the organic solvent is evaporated, and then the mixture is crushed. The crushed mixture obtained by crushing is classified to obtain a compound.

[0020] In step (a), the polystyrene is preferably mixed in an amount of 2 wt% or less, more preferably 1 wt% to 2 wt%, relative to 100 wt% of the rare earth-iron-based magnet powder. If the amount exceeds 2 wt%, carbide is generated in step (b1), resulting in a large amount of residual carbon in the sintered magnet body, which may result in excessive degradation of the magnetic properties. If the amount is less than 1 wt%, the improvement in packing efficiency in step (b1) may be insufficient.

[0021] In step (b1) (hot densification step), the compound obtained in step (a) is filled into a first mold and hot densified. Specifically, in step (b1), a first mold is prepared. The first mold is composed of a hollow cylindrical die and cylindrical upper and lower punches inserted inside the die. The die, upper and lower punches are made of a conductive material (e.g., graphite, cemented carbide, etc.).

[0022] Next, the compound is filled into the first mold, and the mold is set in a sintering apparatus (SPS apparatus: spark plasma sintering apparatus) for sintering, and the sintered magnet body (hot-pressed magnet body) is removed from the first mold.

[0023] The compound filled in the cavity of the first die is compressed by the upper and lower punches through pressure applied between the upper and lower electrodes. Current flows from the upper electrode to the upper punch, then through the die and compound, and then through the lower punch to the lower electrode, generating Joule heat and generating discharge plasma within the compound, which heats the compound. For example, the compound is heated to 600-700°C while being pressurized at 30-50 MPa (hot press). Sintering is preferably performed under reduced pressure in an inert atmosphere, specifically, an argon or nitrogen atmosphere.

[0024] After heating, the sintering machine is turned off and cooled. After cooling to a predetermined temperature, the first mold is removed from the sintering machine. Specifically, the cylindrical sintered magnet body formed by debinding and sintering is removed from the first mold. Although the sintered magnet body is debound, it usually contains carbon.

[0025] In step (b2) (hot plastic working step), the sintered magnet body obtained in step (b1) is packed into a second mold and subjected to hot plastic working. Specifically, in step (b2), a second mold is first prepared. The second mold may be prepared in parallel with the preparation of the first mold, or may be prepared before the first mold. Next, the sintered magnet body produced in the hot densification step is placed in the second mold, and the second mold is then placed in a sintering apparatus for hot plastic working.

[0026] In the sintering apparatus, an upper electrode is disposed on the upper end of the punch, and a lower electrode is disposed on the lower end of the die. The upper and lower electrodes are formed of a conductive material (e.g., graphite, cemented carbide, etc.). The sintering apparatus is equipped with a power supply device and a control device that apply a predetermined voltage between the upper and lower electrodes to supply a predetermined current. The sintering apparatus may also be used as the sintering apparatus in the hot densification process, or may be a separate device.

[0027] The sintered magnet body, placed between the die and punch of the second mold, is pressed by the die and punch. It is also heated by discharge plasma and Joule heat generated by current flowing through the upper electrode → punch → sintered magnet body → die → lower electrode. Hot plastic working begins with the application of a pressure of 30 to 100 MPa, followed by heating. The sintered magnet body is pressurized while being heated, for example, to 600°C or higher and 700°C or lower. During heating, an ON-OFF DC pulse current is applied to the sintered magnet body. During hot plastic working, the pressure is adjusted to prevent the working speed from increasing, preferably to maintain a constant working speed. Hot plastic working is preferably performed under reduced pressure or in an inert atmosphere, specifically, an argon or nitrogen atmosphere. Hot plastic working is preferably performed from the start of displacement to its completion while monitoring the displacement. Here, the displacement is typically monitored by monitoring the displacement of a servo motor controlling the pressure.

[0028] After heating, the current is cut off and the sintering machine is cooled. After cooling to a predetermined temperature, the second die is removed from the sintering machine, and the cylindrical hot-processed magnet obtained by hot plastic processing of the sintered magnet body is taken out from the second die.

[0029] In the hot-processed magnet obtained in step (b2), the relative density of the magnetic particles typically exceeds 95%. Therefore, the hot-processed magnet is then subjected to step (c). That is, in step (c), the hot-processed magnet obtained in step (b2) is magnetized (e.g., pulse magnetized) to provide multiple magnetic poles in the axial direction of the end face. This results in the magnetic body 1. By undergoing steps (b1) and (b2) of the above-described manufacturing method, the end face of the magnetic body 1 forms a reference plane. Furthermore, by undergoing steps (b1) and (b2) of the above-described manufacturing method, the residual magnetic flux density of the end face 11 in the axial direction Z is also greater in the magnetized magnetic body 1 than the residual magnetic flux density of the outer peripheral surface 12 in the radial direction X. Furthermore, the multiple magnetic particles have portions oriented in a direction intersecting the axial direction Z. Similar to the hot-processed magnet, the relative density of the magnetic particles in the magnetized magnetic body 1 typically exceeds 95%.

[0030] If the relative density of the magnetic particles in the sintered magnet body obtained in step (b1) exceeds 95%, step (b2) does not need to be performed. That is, the sintered magnet body obtained in step (b1) may be subjected to step (c). In this case, the same magnetic body 1 as that obtained by performing step (b2) can be obtained.

[0031] The hot densification and hot plastic working processes cause crystal grains to grow into flattened shapes, and the flat surfaces of the particles tend to mechanically align in the direction of pressure. In other words, the direction of pressure (the minor axis direction of the crystal grains) and the axis of easy magnetization tend to align. As a result, the axis of easy magnetization of the crystal grains within the magnet tends to align in the thickness direction of the sintered magnet body and hot plastic working magnet. Therefore, sintered magnet bodies and hot plastic working magnets have magnetic anisotropy.

[0032] However, in sintered magnet bodies and hot-processed magnets with a relative density of magnetic particles exceeding 95%, the magnetic particles also have portions oriented in a direction intersecting the axial direction Z. Therefore, these sintered magnet bodies and hot-processed magnets are believed to have excellent magnetization characteristics when magnetized axially into multiple poles. In particular, magnetic flux density can be improved even when the magnetizing current is low. The presence of portions oriented in a direction intersecting the axial direction can be confirmed by static magnetic properties. Specifically, J-H curves measured for the sintered magnet bodies and hot-processed magnets reveal differences in characteristics depending on the measurement direction.

[0033] Furthermore, even after magnetization, the magnetic body 1 has a plurality of magnetic particles that have portions oriented in a direction that intersects with the axial direction Z. The fact that the magnetic particles have portions oriented in a direction that intersects with the axial direction can be confirmed by measuring a J-H curve, which shows a difference in characteristics depending on the measurement direction. Therefore, it is considered that the magnetic body 1 is a magnetic body that has been magnetized in multiple poles from the axial direction, and that its magnetization characteristics have been greatly improved. In particular, the magnetic flux density can be improved even when the magnetizing current is low. The magnetization characteristics are more improved when steps (b1) and (b2) are performed than when only step (b1) is performed.

[0034] <Magnetic Body of Embodiment 2> Figure 3 is a diagram illustrating a magnetic body of embodiment 2. The magnetic body 2 is ring-shaped and includes an end face 21 extending in the radial direction X and an outer peripheral surface 22 and an inner peripheral surface 23 extending in the axial direction Z. The end face 21 has multiple magnetic poles in the axial direction. For example, the magnetic body 2 may have four magnetic poles, and preferably has four or more magnetic poles. Apart from these points, the magnetic body 2 is similar to the magnetic body 1 described in embodiment 1. Therefore, the magnetic body 2 is also binderless and can be produced through a hot densification process or a hot plastic working process. The relative density of the magnetic particles exceeds 95%, and the residual magnetic flux density of the end face 21 in the axial direction Z is greater than the residual magnetic flux density of the outer peripheral surface 22 in the radial direction X. The magnetic body 2 is a magnetic body magnetized in multiple poles from the axial direction and has excellent magnetic flux density. In particular, the magnetic flux density is excellent even when the magnetizing current is low.

[0035] The method for producing magnetic body 2 is the same as the method for producing magnetic body 1, except that the first mold used in step (b1) (hot densification step) is different. Here, step (b1) in the method for producing magnetic body 2 will be described.

[0036] In step (b1) (hot densification step), the compound obtained in step (a) is filled into a first mold and hot densified. Specifically, in step (b1), a first mold is prepared. The first mold is composed of a hollow cylindrical die, hollow cylindrical upper and lower punches inserted inside the die, and cylindrical cores placed inside the upper and lower punches. The die, upper and lower punches, and core are made of a conductive material (e.g., graphite, cemented carbide, etc.).

[0037] Next, the compound is filled into the first mold, and the mold is set in a sintering apparatus (SPS apparatus: spark plasma sintering apparatus) for sintering, and the sintered magnet body (hot-pressed magnet body) is removed from the first mold.

[0038] The compound filled in the cavity of the first mold is compressed by the upper and lower punches through pressure applied between the upper and lower electrodes. Furthermore, current flows from the upper electrode to the upper punch, then through the die, core, and compound, and then to the lower electrode via the lower punch. This generates Joule heat and generates discharge plasma within the compound, heating the compound. For example, the compound is heated to 600-700°C while being pressurized at 30-50 MPa (hot press). Furthermore, sintering is preferably performed under reduced pressure in an inert atmosphere, specifically, an argon or nitrogen atmosphere.

[0039] After heating, the sintering machine is turned off and cooled. After cooling to a predetermined temperature, the first mold is removed from the sintering machine. Specifically, the ring-shaped sintered magnet body formed by debinding and sintering is removed from the first mold. Although the sintered magnet body is debound, it usually contains carbon.

[0040] The present invention will be explained in more detail below based on examples, but the present invention is not limited to these examples.

[0041] [Examples] [Example 1] In Example 1, the magnetic body 1 described in Embodiment 1 was produced. Step (a): 200 g of Nd—Fe—B magnetic powder (magnetic particles, product name: MQU-M, manufactured by Magnequench) was mixed with 4 g of polystyrene dissolved in 20 g of methyl ethyl ketone (MEK). Next, the mixture was kneaded for 15 minutes in a laboratory mill while evacuating the air in a draft chamber to obtain a kneaded mixture. The kneaded mixture was placed in an oven heated to 80°C and dried for 30 minutes to volatilize the MEK. The powder from which the MEK had volatilized was crushed in a mortar to obtain a compound. Step (b1): The compound obtained in Step (a) was filled into a first mold and hot densified. The first mold consisted of a hollow cylindrical die and cylindrical upper and lower punches inserted inside the die. The die, upper and lower punches were made of conductive material. The compound was filled into the first mold and placed in a sintering apparatus (SPS apparatus: spark plasma sintering apparatus) for sintering. After heating, the sintering apparatus was turned off and cooled. After cooling to a predetermined temperature, the first mold was removed from the sintering apparatus. A cylindrical sintered magnet body (hot-pressed magnet body) formed by sintering the magnet powder was removed from the first mold. Its relative density was 98.4%. Its dimensions were 9 mm in diameter and 7 mm in height. Step (c): The sintered magnet body obtained in step (b1) was pulse-magnetized to provide multiple magnetic poles (four poles) in the axial direction of the end faces. This resulted in magnetic body 1. The end faces of magnetic body 1 formed reference planes. Magnetic body 1 contained carbon. Its relative density and size remained the same as those of the sintered magnet body. Here, the relative density was 98.4%. Carbon was also present, but the amount was 2000 ppm or less. The relative density was calculated from the ratio of the density of the sintered body to the true density of the alloy. The density of the sintered body was determined by the buoyancy method. Here, the true density of the alloy is, for example, 7.6 g / cm 3 The carbon content was measured by a combustion method using a CS analyzer.

[0042] <Static Magnetic Properties> Figure 4 shows the results of measuring the J-H curve for the hot-worked magnet obtained in step (b1) of Example 1. Measurements were performed on the outer peripheral surface in the radial direction X and the end surface in the axial direction Z. It was found that the residual magnetic flux density at the end surface in the axial direction Z was greater than the residual magnetic flux density at the outer peripheral surface in the radial direction X. This indicated a difference in characteristics depending on the measurement direction. Therefore, it was confirmed that multiple magnetic particles have portions oriented in a direction intersecting the axial direction Z. It is believed that similar results would be obtained if the J-H curve were measured for the magnetic body 1 obtained in step (c). In other words, it is believed that the residual magnetic flux density at the end surface in the axial direction Z is greater than the residual magnetic flux density at the outer peripheral surface in the radial direction X. It is believed that this indicates a difference in characteristics depending on the measurement direction. Therefore, it is believed that it is confirmed that multiple magnetic particles have portions oriented in a direction intersecting the axial direction Z. Here, the J-H curve was measured using a B-H curve tracer.

[0043] <Magnetic Properties> To evaluate the magnetic properties, cubic (7 mm per side) sintered magnet bodies for evaluation (A1) and (A2) were produced in the same manner as Magnetic Body 1 above, except that the first mold was changed. The four side faces of the cube can be considered the outer circumferential surfaces of Magnetic Body 1, and the top and bottom faces of the cube can be considered the end faces of Magnetic Body 2. One side face of the sintered magnet body for evaluation (A1) was subjected to pulse magnetization (four poles) with a pole pitch of 1.57 mm. In this manner, Magnetic Body for Evaluation (A1) was obtained. Furthermore, the top face of the sintered magnet body for evaluation (A2) was subjected to pulse magnetization (four poles) with a pole pitch of 1.57 mm. In this manner, Magnetic Body for Evaluation (A2) was obtained. Note that FIG. 5-1 shows the magnetic body for evaluation (A1) after magnetization, and FIG. 5-2 shows the magnetic body for evaluation (A2) after magnetization. FIG. 6 shows the results of measuring the surface magnetic flux density for the evaluation magnetic bodies (A1) and (A2) obtained in Example 1. Here, the surface magnetic flux density was measured for the magnetized surfaces of the evaluation magnetic bodies (A1) and (A2). FIG. 6 also shows calculated values ​​along with the measured values. As can be seen from FIG. 6, the magnetic properties of the evaluation magnetic body (A2), which was magnetized on the top surface, were improved compared to the calculated values. In particular, the magnetic flux density was improved when the magnetizing current was low. This is presumably due to the presence of a portion in which multiple magnetic particles are oriented in a direction intersecting the axial direction Z. It is believed that the magnetic properties of the magnetic body 1, which was magnetized on the end surface, were also significantly improved, similar to the evaluation magnetic body (A2). Specifically, it is believed that the magnetic properties were improved when the magnetizing current was low. Here, the surface magnetic flux density was measured using a magnet analyzer.

[0044] Example 2 In Example 2, the magnetic body 1 described in Embodiment 1 was produced. Steps (a) and (b1) were performed in the same manner as in Example 1. Step (b2): The sintered magnet body obtained in step (b1) was packed into a second mold and subjected to hot plastic processing. Specifically, the sintered magnet body produced in the hot densification step was placed in the second mold, and the second mold was then placed in a sintering apparatus for hot plastic processing. After heating, the sintering apparatus was turned off and cooled. After cooling to a predetermined temperature, the second mold was removed from the sintering apparatus. A cylindrical hot plastic processed magnet obtained by hot plastic processing from the sintered magnet body was removed from the second mold. The relative density was 98.4%. The hot plastic processed magnet had a diameter of 9 mm and a height of 7 mm. Step (c): The hot plastic processed magnet obtained in step (b2) was pulse-magnetized to provide multiple magnetic poles in the axial direction of the end faces. This produced magnetic body 1. The end faces of the magnetic body 1 formed reference surfaces. The magnetic body 1 contained carbon. The relative density and size remained the same as those of the hot plastic processing magnet.

[0045] <Static Magnetic Properties> Figure 7 shows the results of measuring the J-H curve for the hot-formed magnet obtained in step (b2) of Example 2. The measurements were performed on the outer peripheral surface in the radial direction X and the end surface in the axial direction Z. It was found that the residual magnetic flux density at the end surface in the axial direction Z was greater than the residual magnetic flux density at the outer peripheral surface in the radial direction X. The J-H curve also exhibited a gentle curve. This confirmed that multiple magnetic particles have portions oriented in a direction intersecting the axial direction Z. It is believed that similar results would be obtained if the J-H curve were measured for the magnetic body 1 obtained in step (c). In other words, it is believed that the residual magnetic flux density at the end surface in the axial direction Z is greater than the residual magnetic flux density at the outer peripheral surface in the radial direction X. The J-H curve also exhibits a gentle curve. This confirmed that multiple magnetic particles have portions oriented in a direction intersecting the axial direction Z.

[0046] <Magnetic Properties> To evaluate the magnetic properties, cubic (7 mm per side) sintered magnet bodies for evaluation (A3) and (A4) were produced in the same manner as magnetic body 1 above, except that the first mold was changed. The four side surfaces of the cube can be considered to be the outer peripheral surfaces of magnetic body 2, and the top and bottom surfaces of the cube can be considered to be the end faces of magnetic body 2. One side surface of sintered magnet body for evaluation (A3) was subjected to pulse magnetization (four poles) with a pole pitch of 1.57 mm. In this manner, magnetic body for evaluation (A3) was obtained. Furthermore, the top surface of sintered magnet body for evaluation (A4) was subjected to pulse magnetization (four poles) with a pole pitch of 1.57 mm. In this manner, magnetic body for evaluation (A4) was obtained. The magnetic poles of magnetic bodies for evaluation (A3) and (A4) after magnetization were formed in the same manner as magnetic bodies for evaluation (A1) and (A2) shown in FIGS. 5-1 and 5-2, respectively. FIG. 8 shows the results of measuring the surface magnetic flux density for the evaluation magnetic bodies (A3) and (A4) obtained in Example 2. Here, the surface magnetic flux density was measured for the magnetized surfaces of the evaluation magnetic bodies (A3) and (A4). FIG. 8 also shows calculated values ​​along with the measured values. As can be seen from FIG. 8, the magnetic properties of the evaluation magnetic body (A4) magnetized at the end face were improved compared to the calculated values. In particular, the magnetic flux density was improved when the magnetizing current was low. This is presumably due to the presence of a portion in which multiple magnetic particles are oriented in a direction intersecting the axial direction Z. It is believed that the magnetic properties of the magnetic body 1 magnetized at the end face were also significantly improved, similar to the evaluation magnetic body (A4). Specifically, it is believed that the magnetic properties were improved when the magnetizing current was low.

[0047] 1, 2 magnetic material, 11, 21 end surface, 12, 22 outer peripheral surface, 23 inner peripheral surface

Claims

1. A magnetic body comprising a plurality of magnetic particles, being cylindrical, having end faces extending in the radial direction and an outer peripheral surface extending in the axial direction, wherein the end faces have a plurality of magnetic poles in the axial direction, the end faces form a reference plane, the residual magnetic flux density of the end faces in the axial direction is greater than that of the outer peripheral surface in the radial direction, and the relative density of the magnetic particles exceeds 95%.

2. A magnetic body comprising a plurality of magnetic particles, being ring-shaped, having end faces extending in the radial direction and an outer peripheral surface and an inner peripheral surface extending in the axial direction, wherein the end faces have a plurality of magnetic poles in the axial direction, the end faces form a reference plane, the residual magnetic flux density of the end faces in the axial direction is greater than that of the outer peripheral surface in the radial direction, and the relative density of the magnetic particles exceeds 95%.

3. The magnetic body according to claim 1 or 2, wherein the plurality of magnetic particles have portions oriented in a direction intersecting the axial direction.

4. The magnetic body according to claim 1 or 2, wherein the reference plane is a flat surface.

5. The magnetic body according to claim 1 or 2, which contains carbon.

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