JP5870567B2 - Bow magnets and magnetic field molds - Google Patents

Description

  The present invention relates to an arcuate arc-shaped magnet and a magnetic field molding die.

  The arcuate magnet has an arc shape and is used for a rotor or a stator of an electric motor. For example, in Patent Document 1, when manufacturing a ferritic magnet having an arc shape and anisotropy in the radial direction, by using a dry molding apparatus provided with an orientation ferromagnetic material, the anisotropy direction is in the radial direction. Is obtained. Patent Document 1 also describes that the cogging torque and torque ripple of the motor are reduced by defining the surface magnetic flux density of the anisotropic ferrite magnet.

JP 2007-281437 A

  When an arcuate magnet is used for an electric motor, for example, arcuate magnets magnetized to one pole are alternately arranged with N and S poles in the circumferential direction of the rotor or stator. In recent years, there has been a demand to reduce the number of arcuate magnets used in electric motors. In this case, for example, an arcuate magnet whose dimension in the circumferential direction is larger than an arcuate magnet magnetized to one pole may be used by magnetizing to two poles. In this way, the number of arcuate magnets used in one electric motor can be reduced. In this case, if the anisotropic direction is aligned in the radial direction and only two poles are magnetized, one arcuate magnet is attached. Compared with the case of using a magnetized arcuate magnet, there is a problem that the magnetic flux density that can be effectively used is reduced. Patent Document 1 does not disclose or suggest this point, and there is room for improvement. An object of the present invention is to suppress a decrease in magnetic flux density that can be effectively used in an arcuate magnet magnetized on a plurality of poles.

  In order to solve the above-described problem, a sintered magnet according to the present invention is a magnet including a plurality of magnetic powder particles, and in the cross section cut by a plane orthogonal to the length direction of the magnet, the plurality of magnetic powder particles are The orientation direction of the easy axis of magnetization is oriented so as to focus on at least two points.

  The arcuate magnet has a circular cross section cut by a plane orthogonal to the length direction, and the orientation direction of the easy axis of the plurality of magnetic particle particles is converged to at least two points in the cross section. And is magnetized to the same number of poles as the number of converging points. By doing in this way, magnetic flux can be concentrated from this arcuate magnet toward the teeth of the electric motor facing this. As a result, this arcuate magnet can suppress a decrease in magnetic flux density that can be effectively used in an arcuate magnet magnetized on a plurality of poles, and an arcuate magnet magnetized on one pole alternately with N and S poles. Compared with the case where it arranges, the magnetic flux density which a tooth can utilize can be made equivalent or more.

  As a desirable mode of the present invention, when the arcuate magnet is magnetized with one pole, the arcuate magnet is arranged so that the cross-sectional shape of the arcuate magnet is an arc-shaped first curved surface and the outside of the first curved surface. In addition, it is preferable that the waveform of the magnetic flux density on at least one of the second curved surface having a circular arc shape in the cross section has a peak as many as the number of points where the orientation directions converge. By doing so, the orientation directions of the easy magnetization axes of the plurality of magnetic powder particles are focused on at least two points, so that the magnetic flux density that can be effectively used is reduced in the arcuate magnets magnetized on the plurality of poles. Can be suppressed.

  As a desirable mode of the present invention, the absolute value of the difference between the peak and the minimum value of the waveform is preferably 5% or more of the absolute value of the minimum value. By doing so, the orientation directions of the easy magnetization axes of the plurality of magnetic powder particles are focused on at least two points. Therefore, the magnetic flux density that can be effectively used in the arcuate magnet magnetized on the plurality of poles. Can be suppressed.

  In order to solve the above-described problem, a magnetic field molding die according to the present invention includes a mold frame, a first punch, and a second punch, and includes the mold frame, the first punch, and the second punch. A magnetic field molding die for pressurizing magnetic powder particles in an enclosed molding space to form an arc shape, wherein at least one of the first punch and the second punch is in contact with the magnetic powder particles A non-magnetic body having a convex portion projecting toward the non-magnetic body at a portion that is in contact with the non-magnetic body on the side opposite to the molding surface of the non-magnetic body and is in contact with the non-magnetic body. And having two ferromagnets.

  For example, when both the first punch and the second punch have the nonmagnetic material, at least one of the ferromagnetic materials protrudes toward the nonmagnetic material at a portion in contact with the nonmagnetic material. It has at least two convex parts. Further, when either the first punch or the second punch has the nonmagnetic material, the ferromagnetic material in contact with the nonmagnetic material is directed to the nonmagnetic material at a portion in contact with the nonmagnetic material. And at least two convex portions projecting. By magnetically forming the magnetic powder particles using this molding die, the orientation directions of the easy magnetization axes of the magnetic powder particles are converged to at least two points in a cross section cut by a plane orthogonal to the length direction. An arcuate magnet can be obtained.

  The present invention can suppress a decrease in magnetic flux density that can be effectively used in an arcuate magnet magnetized on a plurality of poles.

FIG. 1 is a perspective view showing an example of an arcuate magnet according to the present embodiment. FIG. 2 is a cross-sectional view showing a state in which the bow-shaped magnet according to this embodiment is cut by a plane orthogonal to the length direction. FIG. 3 is a cross-sectional view showing the orientation direction of the easy axis of magnetic powder particles in the cross section of the bow magnet according to the present embodiment. FIG. 4 is a diagram for explaining magnetization. FIG. 5 is a schematic diagram showing a state in which the bow magnet according to the present embodiment is magnetized. FIG. 6 is a diagram showing the relationship between the arcuate magnet magnetized one pole at a time and the teeth of the electric motor. FIG. 7 is a diagram showing a relationship between a bow magnet magnetized with two poles and teeth of an electric motor. FIG. 8 is an explanatory diagram of a method for measuring the surface magnetic flux density of an arcuate magnet. FIG. 9 is an explanatory diagram of a method for measuring the surface magnetic flux density of an arcuate magnet. FIG. 10 is a diagram showing a waveform of the surface magnetic flux density when the arcuate magnet according to the present embodiment is magnetized with one pole. FIG. 11 is a diagram showing a waveform of the surface magnetic flux density when an arcuate magnet having the same size and shape as the arcuate magnet according to the present embodiment is radially oriented and magnetized with one pole. FIG. 12 is a diagram showing a waveform of the surface magnetic flux density in another example when the arcuate magnet according to the present embodiment is magnetized with one pole. FIG. 13 is an explanatory diagram of a magnetic field shaping apparatus for shaping a bow magnet according to the present embodiment. FIG. 14 is an explanatory view showing a molding die included in the magnetic field molding apparatus according to the present embodiment. FIG. 15 is an explanatory view showing a modification of the molding die required for the magnetic field molding apparatus according to the present embodiment. FIG. 16 is an explanatory view showing another method for manufacturing the bow magnet according to the present embodiment. FIG. 17 is an explanatory view showing another method for manufacturing the bow magnet according to the present embodiment.

  Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following description. The constituent elements in the following description include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those in a so-called equivalent range. The configurations disclosed below can be combined as appropriate.

  FIG. 1 is a perspective view showing an example of an arcuate magnet according to the present embodiment. FIG. 2 is a cross-sectional view showing a state in which the bow-shaped magnet according to this embodiment is cut by a plane orthogonal to the length direction. The arcuate magnet 10 has an arch shape as a whole. The arcuate magnet 10 is divided into a first curved surface 11, a second curved surface 12 disposed on the outer side 11 o of the first curved surface 11, opposite to the first curved surface 11, and the first curved surface 11 and the second curved surface 12. And a side surface 13 to be connected. In the present embodiment, the arcuate magnet 10 has a plurality of, more specifically, four side surfaces 13A, 13B, 13C, and 13D. Each of the side surfaces 13A, 13B, 13C, and 13D is a plane and is orthogonal to each other. In the present embodiment, there are four side surfaces 13, but the number of side surfaces is not limited to this. For example, the boundary between the side surfaces 13B and 13D and the first curved surface 11 may be chamfered to provide six side surfaces 13, or the boundary between the side surfaces 13B and 13D and the second curved surface 12 may be chamfered to provide six side surfaces 13. It may be.

  The first curved surface 11 or the second curved surface 12 is a part of a cylinder centered on predetermined axes Za and Zb. The shape of the first curved surface 11 and the second curved surface is an arc shape, that is, a shape of a part of a circle when cut by a plane orthogonal to the axes Za and Zb. In the present embodiment, the axes Za and Zb are the same, and the curvature radius ra of the first curved surface 11 and the curvature radius rb of the second curved surface 12 are different (ra <rb). The axes Za and Zb may be different. Further, the first curved surface 11 and the second curved surface 12 may have the same or different curvature radii.

  The length direction of the arcuate magnet 10 is a direction parallel to the axis Za or the axis Zb that is the center of the first curved surface 11 or the second curved surface 12. This is orthogonal to the curved surface of the first curved surface 11 or the curved surface of the second curved surface 12, that is, the direction along R (the direction indicated by the arrow C in FIG. 1), and the curved surface of the first curved surface 11 or the second curved surface 12. The direction is parallel to the curved surface. In the present embodiment, the length direction can be said to be a direction parallel to a boundary line BL between the side surfaces 13B and 13D having a rectangular planar shape and the first curved surface 11 or the second curved surface 12. A cross section obtained by cutting the arcuate magnet 10 along a plane perpendicular to the length direction is referred to as a transverse cross section of the arcuate magnet 10. The shape in the cross section of the 1st curved surface 11 and the 2nd curved surface 12 is circular arc shape. A direction perpendicular to the length direction is referred to as a width direction, and a circumferential direction of a circle centering on the axis Za or the axis Zb shown in FIG. 2 and passing through the arcuate magnet 10 is referred to as a circumferential direction of the arcuate magnet 10. The dimension of the arcuate magnet 10 in the length direction is referred to as the length of the arcuate magnet 10 (reference numeral L), and the maximum dimension of the arcuate magnet 10 in the width direction is referred to as the width of the arcuate magnet 10 (reference numeral W).

  The arcuate magnet 10 has an arch shape as a whole, and a cross-sectional shape is an arc shape, a C shape, or a fan shape. The arcuate magnet 10 is also called a segment-type magnet (segment magnet), and is used, for example, for a stator (stator) or a rotor (rotor) of an electric motor. The application target of the bow magnet 10 is not limited to the electric motor. For example, the bow magnet 10 can be widely applied to permanent magnets used in speakers, microphones, magnetron tubes, magnetic field generators for MRI, ABS sensors, fuel / oil level sensors, distributor sensors, magnet clutches, and the like.

  In the present embodiment, the bow magnet 10 is a ferrite sintered magnet. The sintered ferrite magnet is obtained by sintering a plurality of ferrite magnetic particles. Ferrite sintered magnets are widely used because they have relatively high magnetic properties and are inexpensive. The kind of sintered ferrite magnet is not particularly limited, and may be any of barium-based, strontium-based, calcium-based and the like. When the arcuate magnet 10 is a ferrite sintered magnet, the manufacturing method of the arcuate magnet 10 may be either a wet manufacturing method or a dry manufacturing method, and the manufacturing method is not limited.

  In the present embodiment, the type of the arcuate magnet 10 is not limited to a ferrite sintered magnet, and may be a sintered metal magnet such as a rare earth sintered magnet or a samarium / cobalt sintered magnet. The arcuate magnet 10 may be a bonded magnet in which magnetic powder particles are hardened with resin or rubber. In other words, the arcuate magnet 10 according to the present embodiment is intended for all magnets including a plurality of magnetic powder particles obtained by molding a plurality of magnetic powder particles.

  FIG. 3 is a cross-sectional view showing the orientation direction of the easy axis of magnetic powder particles in the cross section of the bow magnet according to the present embodiment. 3 indicates the orientation direction of the magnetic powder particles CPm, and CL indicates the center of the arcuate magnet 10 in the width direction (the same applies hereinafter). FIG. 4 is a diagram for explaining magnetization. FIG. 5 is a schematic diagram showing a state in which the bow magnet according to the present embodiment is magnetized. In the present embodiment, the arcuate magnet 10 is oriented so that the easy axes of the plurality of magnetic powder particles CPm converge toward at least two axes Zca and Zcb. That is, as shown in FIG. 3, the arcuate magnet 10 has a plurality of magnetic powder particles CPm in which the orientation direction of the easy magnetization axis is at least two points (two axes Zca and Zcb and the cross section) as shown in FIG. Is oriented to converge at the intersection of When the magnetic powder particles are hardened into the shape of the arched magnet 10, the magnetic powder particles are oriented so that the easy axis of magnetization is focused toward at least two axes Zca and Zcb by forming the magnetic powder particles while being molded in a magnetic field (magnetic field shaping). Orient the CPm. This magnetic field shaping method will be described later. In the present embodiment, the portion where the orientation direction of the easy magnetization axis of the magnetic powder particles converges is not limited to two.

  The easy magnetization axis of the magnetic powder particles CPm corresponds to the easy magnetization axis of the crystal of the magnetic material constituting the magnetic powder particles CPm. When the arcuate magnet 10 is a ferrite magnet, the magnetic powder particles CPm have a hexagonal crystal structure. In such a crystal structure, the easy axis of magnetization of the crystal CRm is the Z axis (see FIG. 3). When the bow magnet 10 is heated and exceeds a certain temperature, the crystal of the bow magnet 10 grows abnormally. When such a cross section of the arcuate magnet 10 is polished, the abnormally grown crystal reflects light and appears to shine more than the surrounding tissue. Therefore, by observing the crystal appearing in the cross section by abnormally growing the crystal of the arcuate magnet 10, it is observed whether or not the easy magnetization axes of the magnetic powder particles CPm are focused toward at least two axes Zca and Zcb. can do. When the arcuate magnet 10 is a ferrite sintered magnet, for example, as shown in FIG. 3, the direction in which the easy axis (Z axis) of the crystal CRm that appears in the cross section faces is obtained, and the easy axis is at least It can be known whether or not the two axes Zca and Zcb are focused.

  By orienting the magnetic powder particles CPm as described above, the arcuate magnet 10 has a portion in which the orientation direction of the magnetic powder particles CPm converges toward the axis Zca and a portion that converges toward the axis Zcb with respect to the center CL in the width direction. And divided. In the present embodiment, for example, as shown in FIG. 4, one arcuate magnet 10 is incorporated in a magnetic case 1, and two poles are provided by an inner surface magnetized yoke 2 that is supplied with power from a power source 3 to generate a magnetic field. (N pole, S pole)

  For example, as shown in FIG. 5, one of the arcuate magnets 10 defined by the width direction center CL is a first portion 10n, and the other is a second portion 10s. In the example shown in FIG. 5, the first portion 10n is magnetized to the N pole and the second portion 10s is magnetized to the S pole. For this reason, the N pole and the S pole are interchanged in the circumferential direction of one arcuate magnet 10. As described above, the direction in which the magnetization easy axes of the plurality of magnetic particle CPm of the arcuate magnet 10 are oriented is toward the axes Zca and Zcb, so the magnetization direction of the arcuate magnet 10 is the axis in the first portion 10n. It goes to Zca and goes to the axis Zcb in the second portion 10s. Thus, since the direction of magnetization of the arcuate magnet 10 is different between the first part 10n and the second part 10s, when the arcuate magnet 10 is used in an electric motor, the magnetic flux of the arcuate magnet 10 is the teeth TS of each electric motor. It becomes easy to concentrate on. As a result, the bow magnet 10 can increase the magnetic flux density that can be used by the teeth TS. This point will be described later.

  FIG. 6 is a diagram showing the relationship between the arcuate magnet magnetized one pole at a time and the teeth of the electric motor. FIG. 7 is a diagram showing a relationship between a bow magnet magnetized with two poles and teeth of an electric motor. In the example shown in FIG. 6, the respective arcuate magnets 110 n and 110 s are oriented by radial orientation so that the easy axis of magnetization of the magnetic powder particles faces the axes Zca and Zcb, respectively. The arcuate magnet 110n is magnetized to the N pole, and the arcuate magnet 110s is magnetized to the S pole. When such arcuate magnets 110n and 110s are assembled to the rotor of the electric motor, the magnetic fluxes from the arcuate magnets 110n and 110s are directed to the axes Zca and Zcb, respectively. As a result, the magnetic flux easily concentrates on each tooth TS of the electric motor, and the amount of magnetic flux passing through each tooth TS increases.

  The arcuate magnet 210 in the example shown in FIG. 7 has a circumferential dimension comparable to the dimension in which the arcuate magnets 110n and 110s shown in FIG. 6 are coupled in the circumferential direction. The arcuate magnet 210 is oriented by radial orientation so that the easy axis of magnetization of the magnetic powder particles faces the axis Zc. The arcuate magnet 210 is subjected to radial orientation, and then the first portion 210n, which is one of the arcuate magnets 210 defined by the center CL in the width direction, is magnetized to the N pole, and the second portion 210s, which is the other. The S pole is magnetized. When such an arcuate magnet 210 is assembled to a rotor of an electric motor, for example, the magnetic flux from the first portion 210n and the second portion 210s is directed to the axis Zc, so that the amount of magnetic flux passing through each tooth TS of the electric motor Less. As a result, the magnetic flux density that can be used by the teeth TS is lower than that of the arcuate magnets 110n and 110s shown in FIG.

  As described above, in the present embodiment, the direction in which the easy magnetization axes of the magnetic powder particles of the arcuate magnet 10 are oriented is focused toward the axes Zca and Zcb. For this reason, when the arcuate magnet 10 is magnetized, the magnetic flux from the arcuate magnet 10 goes to the axis Zca in the first portion 10n and to the axis Zcb in the second portion 10s. When such an arcuate magnet 10 is assembled to a rotor of an electric motor, for example, the magnetic flux from the first portion 10n and the magnetic flux from the second portion 10s are directed to the respective teeth TS of the electric motor. The amount of magnetic flux to be generated is larger than that of the arcuate magnet 210. As a result, the magnetic flux density that can be used by the teeth TS is larger than that of the arcuate magnet 210 shown in FIG.

  In addition, when the arcuate magnets 110n and 110s shown in FIG. 6 are incorporated in a rotor of an electric motor, a constant interval I is generated between them in the circumferential direction. In other words, the arcuate magnets 110n and 110s have a constant interval I between the poles in the combination of a pair of N poles and S poles. As shown in FIG. 5, the arcuate magnet 10 of this embodiment magnetizes one magnet to two poles (N pole, S pole), so that the N pole and S pole are continuous in the circumferential direction. ing. As can be seen from FIGS. 5 and 6, the arcuate magnet 10 is different from the case where the N-pole and S-pole arcuate magnets 110 n and 110 s arranged in one pole are arranged in the circumferential direction. There is no fixed interval I between them. For this reason, when the arcuate magnet 10 is used, the teeth TS can also use the magnetic flux of the arcuate magnet 10 from the region (center region) C near the center CL in the width direction. As a result, the magnetic flux density that can be used by the teeth TS is larger than that of the arcuate magnets 110n and 110s shown in FIG. Next, the magnetic flux density (surface magnetic flux density) Bd on the surface of the bow magnet 10 will be described.

  8 and 9 are explanatory diagrams of a method for measuring the surface magnetic flux density of an arcuate magnet. When measuring the surface magnetic flux density Bd, as shown in FIG. 8, the Hall element 6 is arranged in the vicinity of the first curved surface 11 of the magnetized bow-shaped magnet 10. The Hall element 6 at this time is positioned at the center of the first curved surface 11 in the length direction, and is placed in contact with the first curved surface 11 or as close as possible. The distribution of the surface magnetic flux density Bd from one end PA to the other end PB in the circumferential direction of the first curved surface 11 is measured by rotating the arcuate magnet 10 in the circumferential direction (the direction indicated by the arrow CR in FIG. 8). . When the arcuate magnet 10 is rotated, the distance between the Hall element 6 and the first curved surface 11 is not changed.

  When measuring the surface magnetic flux density Bd of the second curved surface 12 of the arcuate magnet 10, the Hall element 6 is disposed in the vicinity of the second curved surface 12 of the magnetized arcuate magnet 10, as shown in FIG. The Hall element 6 at this time is positioned at the center of the second curved surface 12 in the length direction, and is placed in contact with the second curved surface 12 or as close as possible. Then, by rotating the arcuate magnet 10 in the circumferential direction (the direction indicated by the arrow CR in FIG. 9), the distribution of the surface magnetic flux density Bd from the one end PC to the other end PD in the circumferential direction of the second curved surface 12 is measured. . When the arcuate magnet 10 is rotated, the distance between the Hall element 6 and the second curved surface 12 is prevented from changing. When the surface magnetic flux density Bd measured as described above is plotted against the circumferential position of the arcuate magnet 10, a distribution curve (waveform) of the surface magnetic flux density Bd is obtained.

  FIG. 10 is a diagram showing a waveform of the surface magnetic flux density when the arcuate magnet according to the present embodiment is magnetized with one pole. FIG. 11 is a diagram showing a waveform of the surface magnetic flux density when an arcuate magnet having the same size and shape as the arcuate magnet according to the present embodiment is radially oriented and magnetized with one pole. FIG. 12 is a diagram showing a waveform of the surface magnetic flux density in another example when the arcuate magnet according to the present embodiment is magnetized with one pole. The arcuate magnets used in the measurements of FIGS. 10 to 12 are all the same in material, size, and shape, and have different magnetic field orientation methods.

  10 to 12, the horizontal axis represents the circumferential position θ (degrees) of the arcuate magnet, and the vertical axis represents the surface magnetic flux density Bd. The circumferential position is a range in the circumferential direction of the first curved surface 11 or the second curved surface 12 of the arcuate magnet 10 in the range where θ is about ± 45 degrees centering on 90 degrees and 270 degrees. The vertical axis in FIG. 10 to FIG. 12 is a relative value obtained by normalizing the measured value with the reference surface magnetic flux density. However, since the reference surface magnetic flux density is the same value, the respective results can be compared.

  As shown in FIG. 10, when the arcuate magnet 10 is magnetized with one pole, the magnetic flux density (surface magnetic flux density) on the surface of the arcuate magnet 10, that is, at least one of the first curved surface 11 and the second curved surface 12. The waveform of Bd has peaks as many as the number of axes (points in the cross section) where the orientation directions (magnet powder particle orientation directions) of the easy magnetization axes of the plurality of magnetic powder particles constituting the arcuate magnet 10 converge. When both the first curved surface 11 and the second curved surface 12 have the peaks, the number of the peaks of the arcuate magnet 10 is twice the number of axes on which the orientation direction converges. For example, when the number of axes on which the orientation direction converges is two, the number of the peaks of the arcuate magnet 10 is four. Moreover, when it has the said peak in either the 1st curved surface 11 or the 2nd curved surface 12, the number of the said peaks which the arcuate magnet 10 has becomes equal to the number of the axis | shafts which the said orientation direction converges. For example, when the number of axes on which the orientation direction converges is two, the number of the peaks of the arcuate magnet 10 is two.

  In the present embodiment, there are two axes on which the orientation direction converges as shown in FIG. As shown in FIG. 10, the waveform of the surface magnetic flux density Bd of the arcuate magnet 10 has two peaks Pi on the first curved surface 11 and two peaks Po on the second curved surface 12. On the other hand, as shown in FIG. 11, when the arcuate magnet having the same size and shape as the arcuate magnet 10 shown in FIG. 3 is radially oriented and magnetized with one pole, the waveform of the surface magnetic flux density Bd has only one peak. This is because, as a result of the magnetic particle orientation direction of the arcuate magnet 10 being focused on two different axes, the surface magnetic flux density Bd after magnetization also increases at two different locations in the circumferential direction of the arcuate magnet 10 to form a peak. It is thought that it is to do.

  In the example shown in FIG. 12, the magnetic field orientation conditions, more specifically, the magnetic field in magnetic field shaping is weaker than in the example shown in FIG. In this example, the waveform of the surface magnetic flux density Bd of the arcuate magnet 10 has two peaks Po on the second curved surface 12. In addition, the waveform of the surface magnetic flux density Bd on the first curved surface 11 of the arcuate magnet 10 is minimal when the circumferential position θ of the arcuate magnet 10 decreases near 90 degrees, that is, toward the center in the width direction, and near θ = 90 degrees. Takes a value. In the process, the waveform of the surface magnetic flux density Bd changes the bending direction of the waveform so that the waveform becomes convex upward at the position indicated by Pvi except for the position where the minimum value is obtained. Since the arcuate magnet 10 has two axes on which the magnetic particle orientation direction of the arcuate magnet 10 converges, the waveform of the surface magnetic flux density Bd is obtained as a result of being concentrated at two different magnetic flux densities in the circumferential direction of the first curved surface 11. Is considered to have changed the direction of bending at the position indicated by Pvi.

  Thus, the waveform of the surface magnetic flux density Bd may differ between the arcuate magnets 10 due to different magnetic field orientation conditions. However, the waveform of the surface magnetic flux density Bd on at least one of the first curved surface 11 and the second curved surface 12 has a peak as many as the number of axes in which the magnetic particle orientation directions converge. As described above, the arcuate magnet 10 has a peak in the waveform (distribution) of the surface magnetic flux density Bd in the circumferential direction of at least one of the first curved surface 11 and the second curved surface 12 by the number of axes on which the magnetic particle orientation direction converges. There is a feature in having.

  As shown in FIG. 11, when an arcuate magnet having the same size and shape as the arcuate magnet 10 shown in FIG. 3 is radially oriented and magnetized with one pole, the maximum value of the surface magnetic flux density Bd is 6 on the first curved surface 11. Degree. On the other hand, in the bow magnet 10, the maximum value of the surface magnetic flux density Bd is the value of the peak Pi on the first curved surface 11, which is about 6.8. Further, the minimum value of the surface magnetic flux density Bd of the arcuate magnet 10 is about 6.0 on the first curved surface 11, which is the same as that of the arcuate magnet of FIG.

  The total flux was compared between the example shown in FIG. 10 and the example shown in FIG. The total flux of the arcuate magnet shown in FIG. 11 that is radially oriented and magnetized with one pole was 172 μWb. On the other hand, the total flux of the example shown in FIG. 10, that is, the arcuate magnet 10 in which the magnetic particle orientation directions are focused on two different axes was 177.6 μWb. In this way, the total flux of the arcuate magnet 10 is improved by about 3% compared to the arcuate magnet that is radially oriented and magnetized with one pole. From this result, the arcuate magnet 10 is higher than the case where the arcuate magnet 10 having the same size and shape is radially oriented by adjusting the magnetic field orientation conditions and adjusting the position of the axis where the magnetic particle orientation direction converges. It can be said that the surface magnetic flux density can be obtained.

  In the example shown in FIG. 10, the surface magnetic flux density Bd on the first curved surface 11 of the arcuate magnet 10 has an absolute value of the peak Pi of 6.7 and 6.9, and an absolute value of the minimum value of 6.0. In the first curved surface 11, the absolute values of the difference between the peak Pi and the minimum value of the waveform of the surface magnetic flux density Bd are 0.7 and 0.9, respectively, and 11.7% and 15% of the absolute value of the minimum value, respectively. It is. Further, regarding the surface magnetic flux density Bd on the second curved surface 12 of the arcuate magnet 10, the absolute value of the peak Po value is 3.1 in all cases, and the absolute value of the minimum value is 3.5. In the second curved surface 12, the absolute value of the difference between the peak Po of the waveform of the surface magnetic flux density Bd and the minimum value is 0.4, which is 11.4% of the absolute value of the minimum value. In the example shown in FIG. 12, the surface magnetic flux density Bd on the second curved surface 12 of the arcuate magnet 10 has an absolute value of the peak Po value of 4.2 and 4.1 and an absolute value of the minimum value of 4.45, respectively. . In the second curved surface 12, the absolute value of the difference between the peak Po and the minimum value of the waveform of the surface magnetic flux density Bd is 0.25 and 0.35, 5.6% and 7.8% of the absolute value of the minimum value. It is. From these results, in this embodiment, the arcuate magnet 10 has an absolute value of the difference between the peak of the surface magnetic flux density Bd waveform and the minimum value of 5% or more, preferably 10% or more of the absolute value of the minimum value. For example, the magnetic particle orientation direction can be focused on two different axes, and a decrease in magnetic flux density that can be effectively used can be suppressed.

  In the electric motor including the arcuate magnet 10, the first curved surface 11 of the arcuate magnet 10 faces the teeth 23 included in the stator 26 of the electric motor. However, as can be seen from the results of FIGS. 10 and 12, the arcuate magnet 10 also has the peak of the waveform of the surface magnetic flux density Bd at two different locations in the circumferential direction even on the second curved surface 12. Therefore, it is preferable to apply the arcuate magnet 10 to an electric motor in which the teeth of the stator and the outer peripheral surface of the arcuate magnet face each other because the teeth can effectively use the magnetic flux density. Next, a magnetic field shaping apparatus for shaping the arcuate magnet 10 will be described.

  FIG. 13 is an explanatory diagram of a magnetic field shaping apparatus for shaping a bow magnet according to the present embodiment. FIG. 14 is an explanatory view showing a molding die included in the magnetic field molding apparatus according to the present embodiment. The arcuate magnet 10 shown in FIGS. 1, 3 and the like is manufactured by being molded (magnetic field molding) in a magnetic field by a magnetic field molding device 50 and sintering this molded body. The magnetic field forming device 50 includes a mold 51, a first punch 52, a second punch 53, and a magnetic field generating coil 55. The magnetic field forming device 50 pressurizes the magnetic powder particles CPm (see FIG. 14) in the forming space 54 surrounded by the mold 51, the first punch 52, and the second punch 53 to form an arc shape. The mold 51, the first punch 52, and the second punch 53 serve as a molding die 50M when the arcuate magnet 10 is magnetically molded.

  The mold 51 is a ferromagnetic body and has a cylinder part 51C. The cylinder part 51 </ b> C is a through hole having a rectangular cross section, that is, a shape of the arcuate magnet 10 in a plan view. In the present embodiment, the first punch 52 is disposed in one opening of the cylinder portion 51C. The second punch 53 enters the cylinder portion 51C from the other opening of the cylinder portion 51C. In the present embodiment, the first punch 52 is disposed on the opposite side (upward) from the vertical direction, and the second punch 53 is disposed on the vertical direction side (lower). The molding space 54 is a space surrounded by the mold 51, that is, the cylinder portion 51 </ b> C of the mold 51, the first punch 52, and the second punch 53.

  At the time of magnetic field shaping, magnetic powder particles CPm are introduced into the cylinder portion 51C, and the first punch 52 is disposed in one opening of the cylinder portion 51C. Then, while applying a magnetic field to the magnetic powder particles CPm in the molding space 54 by the magnetic field generating coil 55, the second punch 53 enters the first punch 52 side (in the direction indicated by the arrow P in FIG. 13) to form the molding space. The magnetic powder particles CPm in 54 are pressurized. By such treatment, the magnetic powder particles CPm are pressurized in a magnetic field, so that the easy axis of magnetization of the magnetic powder particles CPm is oriented in the direction of the magnetic field, and the cross section is formed into an arc shape. By sintering the magnetic powder particle compact thus obtained, the bow-shaped magnet 10 can be obtained.

  The first punch 52 includes a non-magnetic body 52N having a molding surface 52a in contact with the magnetic powder particles CPm, and a ferromagnetic body in contact with the non-magnetic body 52N on the side opposite to the molding surface 52a of the non-magnetic body 52N (molding space 54 side). 52M. That is, the nonmagnetic material 52N is in contact with the ferromagnetic material 52M on the side opposite to the molding surface 52a. The second punch 53 is in contact with the nonmagnetic body 53N having a molding surface 53a in contact with the magnetic powder particles CPm, and on the side opposite to the molding surface 53a of the nonmagnetic body 53N (molding space 54 side). A portion in contact with the magnetic body 53N includes a ferromagnetic body 53M having at least two protrusions 56 protruding toward the nonmagnetic body 53N. That is, the nonmagnetic material 53N is in contact with the ferromagnetic material 53M on the side opposite to the molding surface 53a. With such a structure, the nonmagnetic body 52N included in the first punch 52 of the magnetic field forming apparatus 50 and the nonmagnetic body 53N included in the second punch 53 face each other in the cylinder portion 51C of the mold 51. The number of the convex portions 56 corresponds to the number of axes on which the magnetic particle orientation directions of the arcuate magnet 10 shown in FIGS. 1 and 3 are focused, and is not limited to two. The shape of the convex portion 56 is a curved surface shape.

  In the present embodiment, the molding surface 52 a of the nonmagnetic material 52 </ b> N included in the first punch 52 forms the second curved surface 12 of the arcuate magnet 10. Further, the molding surface 53 a of the nonmagnetic material 53 </ b> N included in the second punch 53 forms the first curved surface 11 of the arcuate magnet 10. Therefore, the molding surface 52a is a shape obtained by transferring the second curved surface 12 of the arcuate magnet 10, that is, a concave curved surface shape, and the molding surface 53a is a shape obtained by transferring the first curved surface 11 of the arcuate magnet 10, ie, a convex shape. The curved shape of the shape.

  The ferromagnetic material 53 </ b> M included in the second punch 53 has two curved convex portions 56, so that the magnetic flux in the molding die 50 </ b> M can be directed to the convex portions 56 and 56. As a result, the easy magnetization axes of the plurality of magnetic particle particles constituting the arcuate magnet 10 are focused toward two different axes Zca and Zcb shown in FIG. By such an action, the magnetic field shaping device 50 obtains an arcuate magnet 10 in which the magnetic particle orientation directions converge toward two different axes Zca and Zcb existing inside the first curved surface 11 as shown in FIG. be able to. Further, the non-magnetic body 52N of the first punch 52 and the non-magnetic body 53N of the second punch 53 are arranged to face each other in the molding space 54 so as to be in contact with the magnetic powder particles CPm during the magnetic field molding. The orientation of the arcuate magnet 10 can be prevented from converging on the first curved surface 11 or the second curved surface 12. The radius of curvature of the curved surface of the convex portion 56, the position of the apex, and the like are appropriately adjusted according to the position of the axis on which the magnetic particle orientation direction converges (the same applies hereinafter).

  The material of the mold 51 and the ferromagnets 52M and 53M made of a ferromagnet is not particularly limited as long as it is generally used. For example, carbon steel, carbon tool steel, alloy tool steel, die steel or the like is used as the material of the mold 51 and the ferromagnetic bodies 52M and 53M. The material of the nonmagnetic materials 52N and 53N is not particularly limited, and Stellite (registered trademark), stainless steel, copper beryllium alloy, high manganese steel, bronze, brass, nonmagnetic super steel, or the like can be used.

  Further, either one of the first punch 52 and the second punch 53 may have only a ferromagnetic material, and the ferromagnetic material may be in contact with the magnetic powder particles CPm during magnetic field forming. That is, in the present embodiment, at least one of the first punch 52 and the second punch 53 only needs to have a nonmagnetic material. In this way, the magnetic field orientation conditions can be changed without changing the strength of the magnetic field generated by the magnetic field generating coil 55 shown in FIG. For this reason, when at least one of the first punch 52 and the second punch 53 has a non-magnetic material, the degree of freedom in changing the magnetic field orientation condition is increased. As a result, the magnetic field orientation conditions can be easily changed according to the characteristics of the arcuate magnet 10 to be manufactured. For example, the arcuate magnet of the example shown in FIG. 12 is obtained by forming a magnetic field using only the first punch 52 as the ferromagnetic body 52M. When at least one of the first punch 52 and the second punch 53 has a nonmagnetic material, the ferromagnetic material in contact with the nonmagnetic material protrudes toward the nonmagnetic material at the portion in contact with the nonmagnetic material. Have at least two parts. When at least one of the first punch 52 and the second punch 53 has a nonmagnetic material, the ferromagnetic material in contact with the nonmagnetic material has at least two convex portions that protrude toward the nonmagnetic material.

  FIG. 15 is an explanatory view showing a modification of the molding die required for the magnetic field molding apparatus according to the present embodiment. The molding die 50Ma is for obtaining an arcuate magnet 10 in which the magnetic particle orientation directions are converged toward two different axes existing outside the second curved surface 12 (see FIG. 2). In the molding die 50Ma, the ferromagnetic body 52Ma included in the first punch 52a disposed in one opening of the cylinder portion 51C included in the mold 51 has two protrusions 57 projecting toward the nonmagnetic body 52Na. Have one. The second punch 53a includes a nonmagnetic material 53Na and a ferromagnetic material 53Ma in contact with the nonmagnetic material 53N on the molding space 54 side of the nonmagnetic material 53N. Then, the second punch 53a enters the cylinder portion 51C from the other opening.

  With such a structure, the first punch 52a can direct the magnetic flux in the molding die 50Ma toward the convex portions 57 and 57, respectively. As a result, the easy magnetization axes of the plurality of magnetic particle particles constituting the arcuate magnet 10 are focused toward two different axes existing outside the second curved surface 12 (see FIG. 2). The molding die 50Ma can mold the arcuate magnet 10 in which the magnetic particle orientation directions are focused toward two different axes existing outside the second curved surface 12 (see FIG. 2).

  Further, in the molding die 50Ma, the second punch 53a may be the second punch 53 shown in FIG. That is, the molding die 50Ma includes at least two nonmagnetic bodies 53N having a molding surface 53a and convex portions 56 that are in contact with the non-molding surface side of the nonmagnetic body 53N and project toward the nonmagnetic body 53N. You may provide the 2nd punch 53 containing the ferromagnetic material 52M which has one. In this way, the easy magnetization axes of the plurality of magnetic powder particles constituting the arcuate magnet 10 are two different axes existing inside the first curved surface 11 and two different axes existing outside the second curved surface 12. It becomes focused toward. As a result, the molding die 50Ma having the first punch 52a and the second punch 53 has two different axes existing inside the first curved surface 11 and two different shafts existing outside the second curved surface 12. The arcuate magnet 10 in which the magnetic particle orientation direction is focused toward the axis can be formed. As described above, in this embodiment, the ferromagnetic material included in at least one of the first punch and the second punch has at least two convex portions protruding toward the nonmagnetic material at the portion in contact with the nonmagnetic material. It only has to have.

  16 and 17 are explanatory views showing another method for manufacturing the arcuate magnet according to the present embodiment. In this method (manufacturing method), the arcuate magnet 10 is obtained by joining the partial arcuate magnets 10S and 10S whose dimensions in the circumferential direction of the arcuate magnet 10 shown in FIGS. First, the partial arcuate magnets 10S and 10S are manufactured. The partial arcuate magnets 10S and 10S are each radially oriented in the magnetic field forming. At this time, the magnetic particle orientation directions of the partial arcuate magnets 10S and 10S are focused on the axes Zca and Zcb.

  The partially arcuate magnets 10S and 10S that have been subjected to the magnetic field shaping are joined to each other at the side surfaces 10SP and 10SP. For this bonding, for example, an epoxy adhesive is used. When the partial arcuate magnets 10S and 10S are bonded together, the arcuate magnet 10a is completed. The arcuate magnet 10 converges in the magnetic particle orientation direction toward two different axes Zca and Zcb existing inside the first curved surface 11a. Thus, the arcuate magnet 10 can also be manufactured by joining a plurality of radially oriented partial arcuate magnets 10S, 10S. Therefore, according to this method, the arc-shaped magnet 10 can be manufactured without using the molding dies 50M and 50Ma described above.

  As described above, in the arcuate magnet according to the present embodiment, in the cross section cut by the plane orthogonal to the length direction, the plurality of magnetic particle particles included in the arcuate magnet are focused on at least two points in the orientation direction of the easy magnetization axis. In addition, the number of poles is the same as the number of points to be focused (2 in this embodiment). By doing in this way, magnetic flux can be concentrated from the bow-shaped magnet which concerns on this embodiment toward the teeth of the electric motor which opposes this. As a result, the arcuate magnet according to the present embodiment can make the magnetic flux density available to the teeth equal to or greater than that in the case where the arcuate magnets magnetized to one pole are alternately arranged with the N pole and the S pole. it can.

  The arcuate magnet according to the present embodiment is an arcuate magnet having a size in which two arcuate magnets are connected in the circumferential direction when arcuate magnets magnetized to one pole are alternately arranged with N and S poles. One bow magnet is used with two poles. For this reason, when the arcuate magnet according to the present embodiment is used for an electric motor, the arcuate magnet is assembled to the electric motor as compared with the case where the arcuate magnets magnetized to one pole are alternately arranged with N and S poles. Since the work can be reduced, the productivity of the electric motor can be improved and the manufacturing cost can be reduced.

  Further, when the bow magnet according to the present embodiment is used in an electric motor, the number of bow magnets to be used is smaller than that in the case where arc magnets magnetized on one pole are alternately arranged with N poles and S poles. Can be halved. When an arcuate magnet is manufactured by magnetic field shaping, the time required for magnetic field shaping is almost the same even if the dimensions of the arcuate magnet change. For this reason, the fact that the number of arcuate magnets used in one electric motor can be halved means that the time for manufacturing all the arcuate magnets used in one electric motor can be halved.

  Further, when the arcuate magnet is a sintered ferrite magnet, polishing is necessary after sintering in order to obtain a necessary shape and size. In this polishing, the arcuate magnet is usually sent to the polishing apparatus along its length. That is, in polishing, the total length of the arcuate magnet that passes through the polishing apparatus is proportional to the time required for polishing. The fact that the number of arcuate magnets used in an electric motor can be halved means that the number of all arcuate magnets used in a single electric motor can be halved. Therefore, the arcuate magnet according to the present embodiment halves the total length of the arcuate magnet passing through the polishing apparatus as compared with the case where the arcuate magnets magnetized to one pole are alternately arranged with N poles and S poles. As a result, the time required for polishing can be halved.

  Further, the completed arcuate magnet is inspected, and what has passed the inspection is packed and shipped as a product. The fact that the number of arcuate magnets used in a single electric motor can be halved means that the number of arcuate magnets to be inspected can be halved. For this reason, since the time required for the inspection is reduced by half, the productivity of the bow magnet is improved and the burden on the inspector is reduced. In addition, since the number of arcuate magnets used in one electric motor can be halved, one electric motor can be used as compared with the case where arcuate magnets magnetized in one pole are alternately arranged in N and S poles. It is also possible to reduce the amount of packing material for packing the minute bow-shaped magnet. For this reason, the arcuate magnet according to the present embodiment can reduce the environmental load. As described above, the bow magnet according to the present embodiment improves the productivity and reduces the manufacturing cost as compared with the case where the arc magnet magnetized to one pole is alternately arranged with the N pole and the S pole. There is an advantage that the burden on the inspector and the environmental load can be reduced.

10, 10a, 110, 110n, 110s, 210 Arcuate magnet 10n, 210n First part 10s, 210s Second part 10S Partial arcuate magnet 11, 11a First curved surface 12 Second curved surface 13, 13A, 13B, 13, C, 13D Sides 21, 27, 32, 32a, 121 Rotor 22, 122 Stator core 22a Yoke 23, 123, TS teeth 24, 124 Conductor 26, 31, 36a Stator 27S, 32S Shaft 27C, 32C, 33 Rotor core 30, 30a Electric motor 35 Magnet insertion Slot 36, 36T Teeth 36Y Yoke 37 Coil 37a Excitation coil 50 Magnetic field forming device 50M, 50Ma Mold 51C Cylinder part 51 Mold 52, 52a First punch 52M, 52Ma Ferromagnetic material 52N, 52Ma Non-magnetic material 52a Form surface 53,53a second punch 53M, 53 mA ferromagnetic 53N, 53Na nonmagnetic 53a forming surface 54 forming space 55 a magnetic field generating coil 56, 57 protrusion

Claims (2)

A magnet including a plurality of magnetic powder particles,
In a cross section cut by a plane perpendicular to the length direction of the magnet, the orientation direction of the easy magnetization axes of the plurality of magnetic powder particles is oriented so as to converge on two different axes with the center in the width direction of the magnet as a boundary. And
One of the magnets divided at the center in the width direction is magnetized as an N pole, and the other is magnetized as an S pole. The magnetic powder particles in the molding space including the mold frame, the first punch, and the second punch, and surrounded by the mold frame, the first punch, and the second punch are pressed into a circular arc shape. A magnetic field molding die
At least one of the first punch and the second punch is:
A non-magnetic material having a molding surface in contact with the magnetic powder particles;
A convex portion projecting toward the non-magnetic body is formed at the center in the width direction of the molding surface at a portion in contact with the non-magnetic body on the side opposite to the molding surface of the non-magnetic body and in contact with the non-magnetic body. A ferromagnet having one each at the boundary,
A magnetic field molding die characterized by comprising:

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