Rotating electric machine and manufacturing method thereof

Abstract

Provided is a method for manufacturing rotary electric machines (10, 110) comprising: field magnetons (20, 120) having magnets (23, 123-125) forming a plurality of magnetic poles having alternating polarities in the circumferential direction; and armatures (30, 130) having multi-phase armature windings (33, 133), wherein either the field magnetons or the armatures are configured as a rotor, and the magnets are configured as laminated bodies of divided magnets (24) divided into a plurality of pieces in the axial direction of the rotor. The manufacturing method comprises: a sintering step for sintering a compact of compression-molded magnet powder to obtain a sintered body (50) having a pair of facing flat surfaces (50a); a diffusion treatment step for applying, to the sintered body, a grain boundary diffusion treatment for diffusing heavy rare earth elements into the sintered body by heating the sintered body after attaching deposits containing heavy rare earth elements to the flat surfaces of the sintered body; and a step for producing the laminated bodies of the divided magnets by bringing the flat surfaces of the sintered body, subjected to the grain boundary diffusion treatment, into contact with each other.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Application No. 2021-023752 filed on February 17, 2021, the contents of which are incorporated herein by reference. [Technical field]

[0002] The present disclosure relates to a rotating electric machine and a manufacturing method thereof. [Background technology]

[0003] Conventionally, as described in, for example, Patent Document 1, a rotating electric machine is known that includes a field element and an armature disposed radially opposite the field element, with either the field element or the armature serving as a rotor. The field element has magnets that form multiple magnetic poles with alternating polarities in the circumferential direction. The armature has a multi-phase armature winding. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-24296 A Summary of the Invention

[0005] When a magnetic field is generated by passing a current through the armature winding, and this magnetic field interlinks with the magnets, eddy currents flow through the magnets, which can cause problems due to eddy currents, such as demagnetization due to eddy currents and eddy current loss.

[0006] A primary object of the present disclosure is to provide a rotating electric machine and a manufacturing method thereof that can address problems caused by eddy currents flowing in magnets.

[0007] Means 1 includes a field element having a magnet that forms a plurality of magnetic poles whose polarities alternate in the circumferential direction; an armature having a multi-phase armature winding and disposed at a position facing the field element in the radial direction; In a method for manufacturing a rotating electric machine, in which either the field element or the armature is a rotor, The magnet is composed of a laminate of divided magnets divided into a plurality of pieces in the axial direction of the rotor, a sintering step of sintering the compact of the compressed magnet powder to obtain a sintered body having a pair of opposing flat surfaces; a diffusion treatment step of subjecting the sintered body to a grain boundary diffusion treatment in which a heavy rare earth element is diffused into the sintered body by attaching a deposit containing a heavy rare earth element to the flat surface of the sintered body and then heating the sintered body; and a step of producing a laminate of the divided magnets by bringing the flat surfaces of the sintered bodies that have been subjected to the grain boundary diffusion treatment into contact with each other.

[0008] When eddy currents flow through a magnet, demagnetization due to the eddy currents can occur. Here, in Method 1, a sintered body having a pair of opposing flat surfaces is obtained by sintering a compact of compressed magnet powder. Then, a material containing a heavy rare earth element is attached to the flat surface of the sintered body, and the sintered body is heated, so that a grain boundary diffusion process is performed on the sintered body to diffuse the heavy rare earth element into the interior of the sintered body. The sintered body that has been subjected to this process has an increased coercive force while maintaining the residual magnetic flux density. This makes it possible to suppress the occurrence of demagnetization of the magnet due to eddy currents.

[0009] Here, the diffusion of the heavy rare earth element is limited to a range from the magnet surface to a certain depth. In this regard, in Means 1, the magnet is composed of a stack of divided magnets, so the length dimension in the axial direction of each divided magnet that composes the stack is small. Since each divided magnet is made of a sintered body that has been subjected to grain boundary diffusion treatment, the length dimension in the axial direction of this sintered body is also small. For this reason, when the grain boundary diffusion treatment is performed on the sintered body, the heavy rare earth element can be diffused favorably inside the sintered body, and the coercive force can be favorably increased.

[0010] Means 2 is the same as Means 1, in which the diffusion treatment step is a step of attaching the deposit only to the flat surface of the surface of the sintered body and then heating the sintered body.

[0011] In the method 2, the deposit containing a heavy rare earth element is attached only to the flat surfaces of the surface of the sintered body, which makes it possible to simplify the diffusion treatment process.

[0012] Means 3 is the same as Means 2, in which the diffusion treatment step is a step of attaching the attachment only to each of the pair of flat surfaces of the surface of the sintered body, and then heating the sintered body.

[0013] According to the third aspect, the diffusion process can be simplified and the heavy rare earth element can be suitably diffused into the sintered body from each of the pair of flat surfaces.

[0014] Means 4 is the same as Means 3, wherein the sintered body to which the grain boundary diffusion treatment is applied has a thickness of 16 mm or less.

[0015] When a material was attached to one flat surface of the surface of a sintered body and grain boundary diffusion treatment was performed on the sintered body, the distribution of coercive force in the direction from the surface to the inside of the sintered body was investigated. As a result, the effect of improving the coercive force was observed in the range of about 8 mm from the surface. Therefore, in the fourth method, the thickness of the sintered body is set to 16 mm or less. This allows the heavy rare earth element to be diffused more effectively into the sintered body.

[0016] Here, the thickness of the sintered body is preferably 8 mm or less, as in Means 5. This thickness is set based on the fact that the coercive force is greatly improved in the range from the surface to about 4 mm.

[0017] Means 6 is the method according to Means 2, in which the diffusion treatment step is a step of attaching the attachment only to one of the pair of flat surfaces of the surface of the sintered body, and then heating the sintered body; The thickness of the sintered body to which the grain boundary diffusion treatment is applied is 8 mm or less.

[0018] In the sixth method, when the grain boundary diffusion treatment is performed only on one flat surface, the heavy rare earth element can be more suitably diffused into the interior of the sintered body.

[0019] Here, the thickness of the sintered body is preferably 4 mm or less, as in Means 7.

[0020] Means 8 is any one of Means 1 to 7, comprising a step of filling a molding space of a molding die formed corresponding to the shape of the divided magnet with magnet powder, and compression-molding the filled magnet powder in a magnetic field to obtain the molded body in which the direction of the magnetization easy axis on the d-axis side, which is the magnetic pole center, is closer to the direction of the d-axis than the direction of the magnetization easy axis on the q-axis side, which is the magnetic pole boundary; The sintering step is a step of sintering the obtained compact to obtain a sintered body of the near net shape of the divided magnet.

[0021] It is also possible to obtain a net-shape split magnet having a pair of flat surfaces by subjecting a sintered body of magnet powder to grinding using a grindstone, cutting blade, wire saw, etc. However, in this case, depending on the grinding mode of the sintered body, the orientation of the axis of easy magnetization of the split magnet obtained by the grinding process may deviate from the intended orientation of the axis of easy magnetization, making it impossible to realize the expected magnetic flux.

[0022] In this regard, in Method 8, a sintered body can be obtained by near-net shape processing, thereby ensuring an orientation that suitably suppresses deviation between the direction of the easy magnetization axis of the divided magnets and the intended direction of the easy magnetization axis.

[0023] The means 9 includes a field element having a magnet that forms a plurality of magnetic poles whose polarities alternate in the circumferential direction; an armature having a multi-phase armature winding and disposed at a position facing the field element in the radial direction; In a rotating electric machine in which either the field element or the armature is a rotor, The magnet is composed of a laminate of divided magnets divided into a plurality of pieces in the axial direction of the rotor, Of the surfaces of the divided magnets adjacent to each other in the axial direction, only the contact surfaces where the divided magnets come into contact are subjected to a grain boundary diffusion treatment for diffusing a heavy rare earth element into the interior of each divided magnet.

[0024] According to the ninth aspect, the heavy rare earth element can be suitably diffused inside each of the divided magnets, and the coercive force can be suitably increased. This makes it possible to suppress demagnetization of the magnet caused by eddy currents.

[0025] In the means 10 or 11, the field element has a field element core to which the magnet is attached, The magnets are oriented so that the direction of the easy axis of magnetization on the d-axis side, which is the magnetic pole center, is closer to the direction of the d-axis than the direction of the easy axis of magnetization on the q-axis side, which is the magnetic pole boundary; At least a portion of the q-axis core portion that constitutes the field element core is placed in a magnetically saturated state by the magnetic flux of the magnet.

[0026] In the case of the means 10 or 11, at least a part of the q-axis core portion is in a magnetically saturated state, so that the magnetic permeability of the magnetically saturated portion of the q-axis core portion is reduced, and the inductance is reduced. This makes it possible to reduce the amount of magnetic flux that is generated when the armature winding is energized and that interlinks with the magnet. As a result, it is possible to suppress the generation of eddy current loss in the magnet.

[0027] Here, as the magnet, for example, a magnet embedded in the field core as in means 12 can be used.

[0028] As the magnet, for example, as in means 13, a magnet provided on the peripheral surface of the field core on the armature side in the radial direction can be used.

[0029] Since the magnets are oriented so that the direction of the easy axis of magnetization on the d-axis side is closer to the direction of the d-axis than the direction of the easy axis of magnetization on the q-axis side, the circumferential magnetic flux component near the q-axis in the magnet is large. As a result, the q-axis core portion constituting the field core of means 13 is in a magnetically saturated state. This reduces the amount of magnetic flux from the armature side that interlinks with the magnet, suppressing the generation of eddy current loss in the magnet.

[0030] Means 14 is any one of means 8 to 14, wherein the armature winding is configured as a fractional pitch winding.

[0031] When the armature winding is configured as a fractional pitch winding, the fluctuation of the magnetic flux linking the magnet from the armature side is large compared to when the armature winding is configured as a full pitch winding, and eddy current loss occurring in the magnet is likely to be large. For this reason, there is a great merit in applying measures 8 to 14 to a rotating electric machine in which eddy current loss is likely to be large. [Brief description of the drawings]

[0032] The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: [Figure 1] FIG. 1 is a vertical cross-sectional view of a rotating electric machine according to a first embodiment. [Diagram 2] FIG. 2 is a cross-sectional view of a rotating electric machine; [Diagram 3] FIG. 3 is a cross-sectional view of a rotor and a stator; [Figure 4] FIG. 4 is a diagram showing a configuration of magnets; [Diagram 5] FIG. 5 is a diagram showing a magnet orientation method; [Figure 6] FIG. 6 is a flow chart showing a manufacturing process of a magnet; [Figure 7] FIG. 7 is a perspective view showing a sintered body of magnet powder; [Figure 8] FIG. 8 is a diagram showing the effect of grain boundary diffusion treatment; [Figure 9] FIG. 9 is a cross-sectional view of a rotating electric machine according to a second embodiment; [Figure 10] FIG. 10 is a cross-sectional view of a rotor; [Figure 11] FIG. 11 is a cross-sectional view of a rotor according to a modified example; [Figure 12] FIG. 12 is a cross-sectional view of a rotor according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] The rotating electric machine according to the present disclosure is used, for example, as a vehicle power source, but the rotating electric machine can also be used in a wide range of applications, such as industrial applications, vehicles, aircraft applications, home appliances, office automation equipment, and gaming machines.

[0034] First Embodiment A rotating electric machine 10 according to this embodiment is an inner rotor type interior permanent magnet type rotating electric machine (IPM motor) used as a vehicle motor, and an overview thereof will be described with reference to Figs. 1 and 2. Fig. 1 is a longitudinal sectional view along the rotating shaft 11 of the rotating electric machine 10, and Fig. 2 is a transverse sectional view of the rotor 20 and the stator 30 in a direction perpendicular to the rotating shaft 11. In the following description, the direction in which the rotating shaft 11 extends is defined as the axial direction, the direction extending radially from the rotating shaft 11 as the center is defined as the radial direction, and the direction extending circumferentially from the rotating shaft 11 as the circumferential direction. In this embodiment, the rotor 20 corresponds to a "field element," and the stator 30 corresponds to an "armature."

[0035] The rotating electric machine 10 includes a rotor 20 fixed to a rotating shaft 11, an annular stator 30 provided at a position surrounding the rotor 20, and a housing 12 that accommodates the rotor 20 and the stator 30. The rotor 20 and the stator 30 are arranged coaxially. The rotor 20 is arranged facing the inside of the stator 30 in the radial direction, and a predetermined air gap is formed between the inner peripheral surface of the stator 30 and the outer peripheral surface of the rotor 20. The housing 12 has a pair of bottomed cylindrical housing members 12a, 12b, and the housing members 12a, 12b are joined at their openings and integrated by fastening bolts 13. Bearings 14, 15 are provided in the housing 12, and the rotating shaft 11 and the rotor 20 are rotatably supported by the bearings 14, 15.

[0036] 2, the rotor 20 has a hollow cylindrical rotor core 21 whose inner circumferential surface is fixed to the rotating shaft 11. The rotor core 21 is made of a soft magnetic material, for example, formed by laminating a number of electromagnetic steel sheets. A plurality of magnet accommodating holes 22 are formed in the rotor core 21 and arranged in the circumferential direction, and a magnet 23 (permanent magnet) is embedded in each magnet accommodating hole 22.

[0037] The stator 30 has a stator core 31 as an "armature core" having a substantially cylindrical shape. The stator core 31 is made of a soft magnetic material, and is formed by, for example, laminating a large number of electromagnetic steel sheets. The stator core 31 is provided with a plurality of slots 32 that penetrate in the axial direction and are arranged at equal intervals in the circumferential direction. In the slots 32, for example, a stator winding 33 as a three-phase "armature winding" is wound. In this embodiment, 48 slots 32 are arranged at equal intervals in the circumferential direction so that the three-phase stator windings 33 corresponding to the number of magnetic poles of the rotor 20 can be accommodated.

[0038] Next, the magnet accommodating holes 22 of the rotor core 21 as a "field core" and the magnets 23 will be described in detail with reference to Fig. 3. Note that Fig. 3 shows one pole out of a plurality of magnetic poles (for example, a total of eight poles) of the rotating electric machine 10.

[0039] Rotor core 21 is formed into a generally cylindrical shape by laminating a large number of electromagnetic steel sheets, and has a through hole formed in the center thereof. Rotor core 21 is fixed to rotating shaft 11 by fitting into the through hole. Rotor core 21 has a d-axis and a q-axis.

[0040] In the rotor core 21, a plurality of (16 in this embodiment) magnet accommodating holes 22 are provided at a predetermined distance apart in the circumferential direction, penetrating in the axial direction, near the outer peripheral surface facing the inner peripheral surface of the stator 30. Each magnet accommodating hole 22 is paired, and the pair of magnet accommodating holes 22 forms a substantially V-shape in which the opposing distance between the magnet accommodating holes 22 increases toward the radially outward direction. The pair of magnet accommodating holes 22 are line-symmetrical with the d-axis, which is the magnetic pole center, as the axis of symmetry. In this embodiment, the rotor core 21 is formed with a pair of magnet accommodating holes 22 that are arc-shaped (bow-shaped).

[0041] Magnet accommodating hole 22 is surrounded by arc-shaped curved surfaces 22a and 22b that are equidistant from each other, and flat connecting surfaces 22c and 22d that connect both ends of curved surfaces 22a and 22b. Of connecting surfaces 22c and 22d, connecting surface 22c closer to the q axis is provided so as to be parallel to the q axis. Also, connecting surface 22d closer to the d axis is provided so as to be perpendicular to the d axis.

[0042] A magnet 23 having the same shape as the magnet accommodating hole 22 is inserted and arranged in the magnet accommodating hole 22. In this case, one magnetic pole is formed by a pair of magnets 23 accommodated in a pair of magnet accommodating holes 22. The magnet 23 has ends 23a and 23b facing each other in the longitudinal direction, and the magnetization easy axis of the magnet 23 (i.e., the direction of the internal magnetic field lines, which are the magnet magnetic flux path) is indicated by an arrow. The magnet 23 is arranged so that the magnetization easy axis switches from a direction close to a direction perpendicular to the q axis to a direction close to a direction parallel to the d axis in a non-linear manner that is convex toward the opposite stator side from the end 23b close to the q axis at both ends 23a, 23b. In other words, the magnet magnetic flux path in the magnet 23 is determined in a direction that crosses the magnet 23 in the short direction, and the direction is an arc shape that is convex toward the central axis of the rotor core 21.

[0043] Magnet 23 has opposing magnetic flux action surfaces 23c and 23d, and magnetic flux action surface 23c is closer to stator 30 than magnetic flux action surface 23d. Note that the magnetic flux action surface refers to the surface through which magnetic flux flows in and out.

[0044] Incidentally, FIG. 3 shows magnet 23 forming a north pole, but when forming a south pole, the magnetization easy axis of magnet 23 is oriented in the opposite direction to the magnetization easy axis shown in FIG.

[0045] In this embodiment, the stator 30 has teeth 34 serving as inter-wire members between stator windings 33 adjacent in the circumferential direction.

[0046] In this embodiment, at least a part of the q-axis core portion 21q constituting the rotor core 21 is magnetically saturated by the magnetic flux of the magnet 23. The q-axis core portion 21q is a portion of the rotor core 21 that straddles the q-axis and is sandwiched between a pair of magnets 23 arranged in the circumferential direction. The magnetic permeability of the magnetically saturated portion of the q-axis core portion 21q is reduced, and the inductance is reduced. This can reduce the amount of magnetic flux that is generated when the stator winding 33 is energized and that interlinks with the magnet 23. As a result, the generation of eddy current loss in the magnet 23 can be suppressed.

[0047] The magnetic saturation of the q-axis core portion 21q by the magnetic flux of the magnet 23 may be realized, for example, by the following two configurations. In the first configuration, as shown in Fig. 3, the magnet 23 is oriented so that the direction of the easy axis of magnetization on the d-axis side is closer to the direction of the d-axis than the direction of the easy axis of magnetization on the q-axis side.

[0048] Next, the second configuration will be described. When the stator winding 33 is energized, the stator 30 functions as one magnetic pole (north or south pole). The total width dimension of the teeth 34 present within the length range (Wn) of the circumferentially extending portion functioning as one magnetic pole corresponds to the circumferential width dimension (Wt) of the teeth 34 as the inter-conductor member in one magnetic pole. In the example shown in FIG. 3, Wt=Wt1+Wt2+Wt3+Wt4+Wt5. Wt2, Wt3, and Wt4 correspond to the circumferential width dimension of the teeth 34, and Wt1 and Wt5 correspond to half the circumferential width dimension of the teeth 34.

[0049] The longitudinal dimension of magnet 23 in one magnetic pole (i.e., the dimension of magnetic flux action surface 23c) corresponds to the circumferential width dimension (Wm) of magnet 23 in one magnetic pole. As shown in Fig. 3, in one magnetic pole, magnetic flux action surfaces 23c exist in a pair on the left and right sides centered on the d-axis, so the circumferential width dimension (Wm) of magnet 23 in one magnetic pole is the sum of the dimension (Wm1) of left magnetic flux action surface 23c and the dimension (Wm2) of right magnetic flux action surface 23c.

[0050] If the saturation magnetic flux density of the stator core 31 is Bs and the residual magnetic flux density of the magnet 23 is Br, then the second configuration is "Wt×Bs≦Wm×Br." The second configuration, which emits strong magnetic flux toward the stator 30 such that "Wt×Bs≦Wm×Br" is satisfied, and the first configuration described above magnetically saturate the q-axis core portion 21q.

[0051] Next, the magnet 23 will be further described with reference to FIG.

[0052] In this embodiment, the magnet 23 is a polar anisotropic rare earth magnet, specifically a sintered neodymium magnet. The magnet 23 has an intrinsic coercive force of 400 [kA / m] or more and a residual magnetic flux density Br of 1.0 [T] or more. Each magnet 23 is composed of a plurality of split magnets 24 (six magnets are illustrated) divided in the axial direction. That is, the magnet 23 is composed of a laminate of the plurality of split magnets 24. The split magnets 24 have a pair of parallel flat surfaces 24a facing each other in the axial direction, and a magnetic flux action surface extending from the end of the flat surfaces 24a in a direction perpendicular to the flat surfaces 24a. The flat surfaces 24a adjacent to each other in the axial direction are fixed together by an adhesive or the like in a state of abutting against each other, thereby integrating the laminate of the plurality of split magnets 24. The magnetic flux action surfaces 23a to 23d in FIG. 3 are constituted by the magnetic flux action surfaces of the split magnets 24. Specifically, the magnetic flux action surface 25a shown in Fig. 4 constitutes the magnetic flux action surface 23a of the magnet 23 on the right side with respect to the d-axis shown in Fig. 3, the magnetic flux action surface 25b shown in Fig. 4 constitutes the magnetic flux action surface 23b shown in Fig. 3, and the magnetic flux action surface 25d shown in Fig. 4 constitutes the magnetic flux action surface 23d shown in Fig. 3. In the split magnet 24 of this embodiment, the cross-sectional shape in a plane perpendicular to the longitudinal direction is rectangular (oblong). Moreover, each split magnet 24 is stacked in the axial direction without skew.

[0053] Next, a method for manufacturing magnet 23 according to this embodiment will be described. Fig. 5 is a diagram for explaining orientation in a magnetic field. As shown in Fig. 5, orientation device 40 includes magnetic field coil 41, orientation core 42 disposed in magnetic field coil 41, and die 43 as a molding die. Magnetic field coil 41 generates a magnetic field that passes through the inside of the coil when current is applied. Orientation core 42 has a role of curving the magnetic field generated by magnetic field coil 41 in a predetermined direction, and the magnetic field curved by orientation core 42 passes through die 43. A linear magnetic field is formed by magnetic field coil 41, and a curved magnetic field is generated by orientation core 42.

[0054] The mold 43 is made of a non-magnetic material and has a mold chamber 43a as a molding space formed to match the shape of the magnet 23. The mold chamber 43a is formed to correspond to the shape of the split magnet 24. This enables near-net-shape processing of the split magnet 24. The mold chamber 43a is formed by the tips of the die and upper and lower punches that constitute the mold 43.

[0055] Next, the manufacturing process of the magnet 23 will be described with reference to FIG.

[0056] In step S10, the mold chamber 43a is filled with magnet powder, and the filled magnet powder is compression molded by the upper and lower punches. At this time, a curved magnetic field is formed by the orientation core 42 in the magnetic field coil 41, and magnetic field orientation is performed on the magnet powder in the mold chamber 43a. The magnet powder is aligned so that the directions of easy magnetization are aligned. This makes it possible to obtain a compact of magnet powder oriented so that the direction of the easy magnetization axis on the d-axis side is closer to the direction of the d-axis than the direction of the easy magnetization axis on the q-axis side.

[0057] In the next step S11, the compact is heated in a sintering device. The sintering temperature of the compact is, for example, 950 to 1050°C. As a result, a sintered body 50 of near-net shape of the divided magnet 24 is obtained, as shown in Fig. 7. That is, the sintered body 50 has a pair of parallel flat surfaces 50a and a surface (magnetic flux acting surface) connecting the ends of each flat surface 50a. The sintered body 50 shrinks to about half the volume of the compact.

[0058] In step S12, a grain boundary diffusion treatment is performed on the sintered body 50. More specifically, first, an attachment is attached to the surface of the sintered body 50. In this embodiment, an attachment is attached only to each of a pair of flat surfaces 50a (two surfaces) of the surface (six surfaces) of the sintered body 50 by an attachment device. In FIG. 7, one of the pair of flat surfaces 50a to which the attachment is attached is shown by hatching.

[0059] For example, the deposit may be a powder of an oxide of Dy or Tb, which is a heavy rare earth element, a powder of a fluoride of Dy or Tb, an alloy powder containing Dy or Tb, or a slurry containing the oxide powder, the fluoride powder, or the alloy powder. The solvent used for the slurry is, for example, alcohol. In this case, for example, the deposit is sprayed onto the pair of flat surfaces 50a from a spraying device as the deposit device, or the deposit is applied to the pair of flat surfaces 50a by a coating device as the deposit device, thereby forming a coating layer on the flat surfaces 50a.

[0060] The deposit may also be, for example, in the form of a strip or sheet containing the oxide powder, the fluoride powder, or the alloy powder.

[0061] Next, the sintered body 50 with the deposits is heated by a heating device. The heating temperature is lower than the sintering temperature in the sintering step, for example, 700 to 1000°C. This heating step causes the heavy rare earth element contained in the deposits to diffuse into the interior through the grain boundaries on the surface of the sintered body 50. This makes the content of the heavy rare earth element higher at the grain boundaries than within the crystal grains. As a result, the coercive force can be increased while maintaining the residual magnetic flux density. After that, the sintered body 50 is subjected to an aging treatment.

[0062] After the grain boundary diffusion treatment, residue remains on the surface of the sintered body 50. Therefore, the residue remaining on the surface of the sintered body 50 is subsequently removed by a remover.

[0063] For example, a shot blasting device may be used as the removal device, and the residual matter present on the surface of the sintered body 50 that has been subjected to the grain boundary diffusion treatment may be removed by projecting shot material onto the residual matter. In this case, the shot material adhering to the sintered body 50 may then be removed by an air blasting device. Alternatively, for example, a polishing device may be used as the removal device, and the residual matter may be removed by mechanically polishing the surface.

[0064] Unlike the present embodiment, a method of obtaining a net-shaped divided magnet having a pair of flat surfaces by subjecting a sintered body of magnet powder to grinding using a grinding wheel, cutting blade, wire saw, or the like is also conceivable. However, in this case, depending on the grinding mode of the sintered body, the orientation of the magnetization easy axis of the divided magnet obtained by the grinding process may be shifted from the intended orientation of the magnetization easy axis, making it impossible to realize the expected magnetic flux. In this respect, in the present embodiment, the sintered body 50 can be obtained by near-net-shape processing, so that an orientation that suitably suppresses the deviation between the orientation of the magnetization easy axis of the divided magnet 24 and the intended orientation of the magnetization easy axis can be guaranteed.

[0065] In the following step S13, the sintered compacts 50 are magnetized by a magnetizing device, thereby obtaining the divided magnets 24. Note that magnetization may be performed on each of the sintered compacts 50 individually, or on the sintered compacts 50 that are layered together with an adhesive or the like.

[0066] The produced split magnets 24 are then used to produce the rotor core 21. In the production process, the operations of the die 43, the sintering device, the adhering, heating and removing device used in step S12, the magnetizing device, and the like are controlled by a controller mainly including a microcomputer.

[0067] In this embodiment, the thickness dimension tmag (see FIG. 7) of the sintered body 50 obtained in step S11 is set to 16 mm or less, taking into consideration that the diffusion of the heavy rare earth element is limited to a range from the surface of the sintered body to a predetermined depth.

[0068] FIG. 8 shows the relationship between the depth (distance) from the surface of the sintered body to which the above-mentioned deposit containing a heavy rare earth element is attached, and the coercive force Hcj of a magnet manufactured using the sintered body at a reference temperature (e.g., 23°C).

[0069] As shown in the figure, the coercive force Hcj decreases as the distance from the surface increases, and when the distance is slightly more than 8 mm, the effect of improving the coercive force Hcj is no longer observed. In consideration of the relationship shown in Figure 8 and the fact that a heavy rare earth element is attached to each of the pair of flat surfaces 50a of the sintered body 50, the thickness dimension tmag of the sintered body 50 is set to 16 mm or less.

[0070] By setting the thickness dimension tmag of the sintered body 50 to 16 mm or less, the heavy rare earth element can be suitably diffused inside the sintered body 50, and the coercive force can be suitably increased. In this embodiment, the magnet 23 is configured as a laminate of the divided magnets 24, so that the thickness dimension tmag of the sintered body 50 can be easily reduced, and the thickness dimension tmag can be easily set to 16 mm or less. This allows the heavy rare earth element to be diffused throughout the sintered body 50, and the coercive force can be suitably increased. This also increases the coercive force of the surface of the sintered body 50, which is the magnetic flux acting surface, and therefore demagnetization due to eddy currents can be suitably suppressed.

[0071] Particularly in this embodiment, the grain boundary diffusion treatment is performed by attaching an attachment to each of the pair of flat surfaces 50a of the sintered body 50. This allows the heavy rare earth element to be more effectively diffused inside the sintered body 50, and the coercive force of the magnet 23 can be more effectively increased.

[0072] As shown in Fig. 8, the difference between the coercive force at the minimum depth from the surface where the coercive force Hcj was examined and the coercive force at which the effect of the grain boundary diffusion treatment is no longer observed is defined as ΔH. In this case, the depth at which the effect of ΔH / 2 is obtained is slightly shallower than 4 mm. From the above, in order to more suitably diffuse the heavy rare earth element throughout the sintered body 50, the thickness dimension tmag of the sintered body 50 can be set to, for example, 8 mm or less, 6 mm or less, or 5 mm or less. The lower limit of the thickness dimension tmag is, for example, 3 mm.

[0073] 1 to 3, when the stator winding 33 constituting the rotating electric machine 10 is configured as short-pitch winding, the fluctuation of the magnetic flux linking the magnet 23 from the stator 30 side is large, and eddy current loss occurring in the magnet 23 is likely to be large, compared to when the stator winding is configured as full-pitch winding. For this reason, there is a great advantage in applying the characteristic configuration of this embodiment to the rotating electric machine 10 in which eddy current loss is likely to be large. Incidentally, the stator winding 33 can be configured as short-pitch winding and concentrated winding, for example.

[0074] <Second embodiment> Hereinafter, the second embodiment will be described with reference to the drawings, focusing on the differences from the first embodiment. In this embodiment, as shown in Fig. 9, an outer rotor type SPM motor is used as a rotating electric machine 110.

[0075] The rotating electric machine 110 includes a rotating electric machine main body having a rotor 120 and a stator 130, and a housing 112 provided to surround the rotating electric machine main body. All of these components are arranged coaxially with a rotating shaft 111 provided integrally with the rotor 120. The rotating electric machine 110 can be mounted on a vehicle by fixing the housing 112 to a vehicle frame or the like.

[0076] The stator 130 is provided to surround the rotating shaft 111, and the rotor 120 is disposed radially outside the stator 130. The rotor 120 and the stator 130 are disposed facing each other in the radial direction with an air gap therebetween, and the rotor 120 rotates integrally with the rotating shaft 111, causing the rotor 120 to rotate radially outside the stator 130. In this embodiment, the rotor 120 corresponds to a "field element," and the stator 130 corresponds to an "armature."

[0077] Rotor 120 has a substantially cylindrical rotor core 121 and magnets 123 fixed to the inner circumferential surface of rotor core 121. Rotor core 121 is fixed to rotating shaft 111. Rotor core 121 functions as a magnet holding member, and magnets 123 are fixed in an annular shape to the radially inner side of rotor core 121. Rotor core 121 is made of a soft magnetic material, and is formed by, for example, laminating a large number of electromagnetic steel plates.

[0078] The magnets 123 form an annular shape concentric with the center of rotation of the rotor 120, and multiple magnets are fixed to the inner circumferential surface of the rotor core 121. The magnets 123 are arranged in a line so that their polarity alternates along the circumferential direction of the rotor 120. This forms multiple magnetic poles in the circumferential direction. As in the first embodiment, the magnets 123 are composed of a laminate of multiple split magnets split in the axial direction. Furthermore, each split magnet is stacked in the axial direction without being skewed.

[0079] In this embodiment, as shown in FIG. 10, each magnet 123 forms one magnetic pole and has a cut surface on the q axis. The magnets 123 adjacent to each other in the circumferential direction are arranged in a state of abutment or close to each other. The magnets 123 on both sides of the q axis attract each other, so that the magnets 123 can maintain a contact state with each other. Therefore, the structure contributes to improving permeance. A plurality of magnetization easy axes are oriented in an arc shape with the center of orientation set on the q axis as the center so that the direction of the magnetization easy axis on the d axis side is closer to the direction of the d axis than the direction of the magnetization easy axis on the q axis side. For example, the magnet 124 having a cut surface on the d axis as shown in FIG. 11, or the magnet 125 having a cut surface on the d axis as well as the q axis as shown in FIG. 12 may be used as the magnet. The magnet 125 shown in FIG. 12 forms one magnetic pole with two magnets 125a and 125b arranged in the circumferential direction. In addition, the positions at which the magnet is divided in the circumferential direction are not limited to the positions shown in Figures 10 to 12, but may be any positions. The number of divisions in the circumferential direction of the magnet can be increased within the range in which the magnet can be manufactured. In addition, the magnet is not limited to one divided in the circumferential direction, and a ring-shaped magnet may be used.

[0080] The stator 130 includes a stator winding 133. The stator winding 133 has a plurality of phase windings, and is formed into a cylindrical shape by arranging the phase windings of each phase in a predetermined order in the circumferential direction. In this embodiment, the stator winding 133 is configured to have a three-phase winding by using U-phase, V-phase, and W-phase windings. The stator winding 133 of each phase has a conductor portion that extends in the axial direction and is arranged in a range including the coil side, and a crossover portion that connects conductor portions of the same phase that are adjacent in the circumferential direction.

[0081] The stator 130 includes a stator core 131. The stator core 131 is configured as a core sheet laminate in which core sheets made of magnetic steel sheets are laminated in the axial direction, and has a cylindrical shape with a predetermined thickness in the radial direction. A stator winding 133 is attached to the radially outer side of the stator core 131, which is on the rotor 120 side. The outer peripheral surface of the stator core 131 is curved without any irregularities. The stator core 131 functions as a back yoke. The stator core 131 is configured by, for example, laminating a plurality of core sheets, which are punched into a circular plate shape, in the axial direction. However, a stator core having a helical core structure may be used as the stator core 131.

[0082] In this embodiment, the stator 130 has a slotless structure that does not have teeth for forming slots, but the configuration may be any of the following (A) to (C). (A) In stator 130, inter-conductor members are provided between each conductor portion in the circumferential direction, and a magnetic material is used for the inter-conductor member such that, when the circumferential width of the inter-conductor member at one magnetic pole is Wt, the saturation magnetic flux density of the inter-conductor member is Bs, the circumferential width of magnet 123 at one magnetic pole is Wm, and the residual magnetic flux density of magnet 123 is Br, the relationship Wt×Bs≦Wm×Br is satisfied. (B) In the stator 130, inter-conductor members are provided between the respective conductor portions in the circumferential direction, and a non-magnetic material is used for the inter-conductor members. (C) In the stator 130, no inter-conductor members are provided between the conductor portions in the circumferential direction.

[0083] In this embodiment, at least a portion (specifically, for example, a portion on the magnet 123 side in the radial direction) of the q-axis core portion 121q (see FIG. 10) constituting the rotor core 121 is magnetically saturated by the magnetic flux of the magnet 123. The q-axis core portion 121q is a portion of the rotor core 121 that straddles the q-axis. The magnetic permeability of the magnetically saturated portion of the q-axis core portion 121q is reduced, and the inductance is reduced. This can reduce the amount of magnetic flux that is generated due to the current passing through the stator winding 133 and that interlinks with the magnet 123. As a result, the generation of eddy current loss in the magnet 123 can be suppressed.

[0084] In addition, magnetic saturation of the q-axis core portion 121q by the magnetic flux of the magnet 123 can be achieved by the above-mentioned slotless structure and a configuration in which the magnet 123 is oriented so that the direction of the easy axis of magnetization on the d-axis side is closer to the direction of the d-axis than the direction of the easy axis of magnetization on the q-axis side, as shown in Figure 10.

[0085] The manufacturing method for the split magnets constituting the magnet 123 of this embodiment is the same as that of the first embodiment.

[0086] <Other embodiments> Each of the above embodiments may be modified as follows.

[0087] In the grain boundary diffusion treatment step, the deposit may be attached to only one of the pair of flat surfaces 50a of the sintered body 50. In this case, the thickness dimension tmag of the sintered body 50 is desirably set to 8 mm or less, and more desirably set to 4 mm or less.

[0088] The rotating electric machine of the first embodiment is not limited to an inner rotor type, but may be an outer rotor type. Also, the rotating electric machine of the second embodiment is not limited to an outer rotor type, but may be an inner rotor type.

[0089] The magnet orienting method is not limited to that shown in Figure 3 or Figures 10 to 12, but any other method may be used as long as the magnet is oriented so that the direction of the easy axis of magnetization on the d-axis side is closer to the direction of the d-axis than the direction of the easy axis of magnetization on the q-axis side.

[0090] The present invention is not limited to a rotating electric machine in which the field element is the rotor, but may be a rotating electric machine in which the armature is the rotor.

[0091] The disclosure in this specification is not limited to the exemplified embodiments. The disclosure includes the exemplified embodiments and modifications based thereon by those skilled in the art. For example, the disclosure is not limited to the combination of parts and / or elements shown in the embodiments. The disclosure can be implemented by various combinations. The disclosure can have additional parts that can be added to the embodiments. The disclosure includes the omission of parts and / or elements of the embodiments. The disclosure includes the substitution or combination of parts and / or elements between one embodiment and another embodiment. The disclosed technical scope is not limited to the description of the embodiments. Some disclosed technical scopes are indicated by the description of the claims, and should be interpreted as including all modifications within the meaning and scope equivalent to the description of the claims.

[0092] Although the present disclosure has been described based on the embodiment, it is understood that the present disclosure is not limited to the embodiment or structure. The present disclosure also includes various modifications and modifications within the equivalent range. In addition, various combinations and forms, and other combinations and forms including only one element, more than one element, or less than one element, are also within the scope and concept of the present disclosure.

Claims

1. a field element (20, 120) having a magnet (23, 123-125) that forms a plurality of magnetic poles whose polarities alternate in a circumferential direction, and a field element core (21, 121) to which the magnet is attached; an armature (30, 130) having a multi-phase armature winding (33, 133) and disposed at a position facing the field element in the radial direction; In a rotating electric machine (10, 110) in which either the field element or the armature is a rotor, The magnet is a divided magnet (24) divided into a plurality of pieces in the axial direction of the rotor, and is composed of a laminate of divided magnets having a pair of opposing flat surfaces and a magnetic flux action surface extending in a direction perpendicular to the flat surfaces, a grain boundary diffusion treatment is performed only on the flat surfaces of the respective divided magnets adjacent to each other in the axial direction, where the respective divided magnets abut, to diffuse a heavy rare earth element into the respective divided magnets; the magnets are oriented such that the direction of the easy axis of magnetization on the d-axis side, which is the magnetic pole center, is closer to the direction of the d-axis than the direction of the easy axis of magnetization on the q-axis side, which is the magnetic pole boundary; a rotating electric machine in which at least a portion of a q-axis core portion (21q, 121q) constituting the field element core is rendered into a state of magnetic saturation by the magnetic flux of the magnet.

2. 2. The rotating electric machine according to claim 1, wherein the magnet (23) is embedded in the field core (21).

3. 2. The rotating electric machine according to claim 1, wherein the magnets (123 to 125) are magnets provided on a peripheral surface of the field core (121) on a radial side of the armature (130).

4. 4. The rotating electric machine according to claim 1, wherein the armature winding is configured as a fractional pitch winding.

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