CN110544570A - Permanent magnet and motor - Google Patents
Permanent magnet and motor Download PDFInfo
- Publication number
- CN110544570A CN110544570A CN201910417170.2A CN201910417170A CN110544570A CN 110544570 A CN110544570 A CN 110544570A CN 201910417170 A CN201910417170 A CN 201910417170A CN 110544570 A CN110544570 A CN 110544570A
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- rotor
- permanent magnet
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- region
- permanent
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F7/00—Magnets
- H01F7/02—Permanent magnets [PM]
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02K—DYNAMO-ELECTRIC MACHINES
- H02K1/00—Details of the magnetic circuit
- H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
- H02K1/22—Rotating parts of the magnetic circuit
- H02K1/27—Rotor cores with permanent magnets
- H02K1/2706—Inner rotors
- H02K1/272—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis
- H02K1/274—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis the rotor consisting of two or more circumferentially positioned magnets
- H02K1/2753—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis the rotor consisting of two or more circumferentially positioned magnets the rotor consisting of magnets or groups of magnets arranged with alternating polarity
- H02K1/276—Magnets embedded in the magnetic core, e.g. interior permanent magnets [IPM]
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Permanent Field Magnets Of Synchronous Machinery (AREA)
- Iron Core Of Rotating Electric Machines (AREA)
Abstract
The invention provides a permanent magnet (4) mounted on a rotor (3) of a motor (1), which is composed of one permanent magnet having an irregularity, and has a region having a thickness larger than other regions on one end side in a cross section orthogonal to a rotation axis of the rotor (3) when mounted on the rotor (3).
Description
Technical Field
The present invention relates to a permanent magnet and a motor.
background
in a magnet-embedded motor in which a permanent magnet is embedded in a rotor, the permanent magnet may be demagnetized by a demagnetizing field generated when the rotor rotates. In contrast, for example, japanese patent application laid-open No. 2012-4147 discloses the following technique: the magnet is formed with regions having different coercive forces by forming regions in which the heavy rare earth element is diffused in a part of the magnet by attaching the heavy rare earth element to the surface of the magnet and diffusing the heavy rare earth element into the magnet by heat treatment.
Disclosure of Invention
Problems to be solved by the invention
However, in the technique described in japanese patent application laid-open No. 2012-4147, the heavy rare earth element for improving the coercive force of the magnet is basically expensive, and therefore, the cost increases. In addition, there is a cost for operation of diffusion of heavy rare earth elements such as heat treatment.
The present invention has been made in view of the above circumstances, and an object thereof is to provide a permanent magnet that can be manufactured at low cost and can suppress local demagnetization when a rotor rotates, and a motor using the permanent magnet.
Means for solving the problems
In order to achieve the above object, a permanent magnet according to one aspect of the present invention is mounted to a rotor of an electric motor, and is configured by one permanent magnet having an irregularity, and has a region having a thickness larger than other regions on one end portion side in a cross section perpendicular to a rotation axis of the rotor when mounted to the rotor.
Further, an electric motor according to an aspect of the present invention includes: the permanent magnet assembly includes a rotor having a plurality of magnet insertion holes, and a plurality of permanent magnets respectively housed in the magnet insertion holes, wherein a part of the permanent magnets has irregularities, and a region having a thickness larger than other regions is provided on one end portion side in a cross section perpendicular to a rotation axis of the rotor when the permanent magnets are mounted on the rotor.
With the permanent magnet and the motor described above, the surface magnetic flux of the permanent magnet can be controlled by forming a region in which the thickness of the permanent magnet is large on the one end side. Therefore, when a region having a large thickness is provided on one end portion side of the permanent magnet, local demagnetization occurring when the rotor rotates can be suppressed when the permanent magnet is attached to the rotor. Further, the permanent magnet is excellent in workability because it is composed of one permanent magnet having irregularities.
Here, when the permanent magnet is attached to the rotor, the region having a large thickness can be formed by projecting a part of a main surface of the permanent magnet disposed outside the rotor.
The permanent magnet is easily affected by local demagnetization due to a demagnetization field when the rotor rotates. Therefore, the structure in which a part of the outer main surface of the rotor protrudes can appropriately suppress local demagnetization during rotation.
The region having a large thickness may be formed by irregularities provided on at least one of the pair of main surfaces of the permanent magnet.
by providing the irregularities on at least one main surface as described above, a region having a large thickness can be formed, and the surface area of the permanent magnet can be increased. Therefore, the heat radiation effect can be improved, and local demagnetization caused by rotation of the rotor can be suppressed.
In the above-described motor, the plurality of magnet insertion holes may be periodically arranged in the rotation axis of the rotor, the magnetic poles of the rotor may be formed by permanent magnets inserted into one or more continuous magnet insertion holes among the plurality of magnet insertion holes, and a permanent magnet arranged at an end portion on a rear side with respect to the rotation direction of the rotor among the permanent magnets forming the magnetic poles may have a region having a thickness larger than other regions on one end portion side in a cross section orthogonal to the rotation axis of the rotor.
Among the permanent magnets attached to the rotor to form magnetic poles, the permanent magnet at the end portion on the rear side with respect to the rotational direction is susceptible to local demagnetization during rotation. Therefore, the permanent magnet formed at the end portion on the rear side with respect to the rotation direction has a region having a larger thickness on one end portion side than the other region, and thus local demagnetization during rotation can be appropriately suppressed.
In the motor, the plurality of magnet insertion holes are periodically arranged on the rotation axis of the rotor, the magnetic poles of the rotor are formed by two permanent magnets inserted into two consecutive magnet insertion holes among the plurality of magnet insertion holes, the two permanent magnets forming the magnetic poles are arranged symmetrically with respect to an imaginary line, and the two permanent magnets have a region having a thickness larger than other regions on one end side farther from the imaginary line in a cross section orthogonal to the rotation axis of the rotor.
As described above, by configuring two permanent magnets that are symmetrically arranged with respect to the virtual line and constitute the same magnetic pole to have a region having a larger thickness than the other regions on one end portion side farther from the virtual line in a cross section perpendicular to the rotation axis of the rotor, local demagnetization that may occur at the end portion on the rear side with respect to the rotation direction can be appropriately suppressed regardless of the rotation direction of the rotor.
ADVANTAGEOUS EFFECTS OF INVENTION
According to the present invention, there are provided a permanent magnet that can be manufactured at low cost and can suppress local demagnetization when a rotor rotates, and a motor using the permanent magnet.
Drawings
Fig. 1 is a schematic plan view of a motor according to an embodiment of the present invention.
Fig. 2A is a schematic perspective view illustrating the structure of the permanent magnet.
Fig. 2B is a schematic plan view illustrating the structure of the permanent magnet.
Fig. 3 is an enlarged view of a part of fig. 1.
fig. 4 is a flowchart for explaining an example of the method for manufacturing the permanent magnet.
Fig. 5 shows the results of evaluating the change in the magnetic flux generated on the surface of the permanent magnet by providing the groove portion.
Fig. 6A is a diagram showing a modification of the permanent magnet.
Fig. 6B is a diagram showing a modification of the permanent magnet.
Fig. 6C is a diagram showing a modification of the permanent magnet.
Fig. 7 is a diagram showing a modification of the permanent magnet.
Description of the symbols
1 … electric motor; 3 … rotor; 4. 11 to 14 … permanent magnets; 7 … core; 41 … groove parts; 42 … lobe region.
Detailed Description
Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. The present invention is not limited to the following embodiments, and various modifications can be made.
First, the structure of the motor 1 according to the embodiment will be described with reference to fig. 1.
As shown in fig. 1, the motor 1 includes a stator 2(stator), a rotor 3(rotor) rotatably disposed inside the stator 2, and a shaft 8 coupled to a core 7 of the rotor 3. The motor 1 is a so-called magnet embedded motor (IPM motor) in which a permanent magnet 4 is embedded in a rotor 3.
The stator 2 is composed of a core 5 and a plurality of windings 6 wound around the core 5. A predetermined number of windings 6 are arranged at equal intervals on the inner circumferential surface of the stator 2, and a rotating magnetic field for rotating the rotor 3 is generated by energizing the windings 6.
The rotor 3 is composed of a core 7, a plurality of magnet insertion holes 9 (slots) provided in the core 7, and a plurality of permanent magnets 4 accommodated and fixed in the plurality of magnet insertion holes.
The core 7 is formed of a laminate of thin electromagnetic steel sheets or the like. A shaft hole is formed in the center portion of the core 7, and a shaft 8 serving as a rotation shaft of the rotor 3 is fitted in the shaft hole. A plurality of pairs (4 pairs in fig. 1) of magnet insertion holes 9 arranged periodically on the axis of the core 7 (corresponding to the rotation axis of the rotor 3) are provided near the outer periphery of the core 7. Each pair of magnet insertion holes 9 is arranged symmetrically with respect to an imaginary line a (see fig. 3) extending from the axis of the core 7. The 2 permanent magnets 4 accommodated in the 2 (1 pair) magnet insertion holes 9 symmetrically arranged about the virtual line a are arranged so that the outer sides of the cores 7 have the same pole, and constitute 1 pole. In the case of the motor 1 shown in fig. 1, the number of poles of the rotor 3 is 4.
The permanent magnets 4 shown in fig. 2A and 2B are accommodated in the magnet insertion holes 9. Fig. 2A is a perspective view of the permanent magnet 4, and fig. 2B is a plan view of the permanent magnet 4. In the present embodiment, the shape of the magnet insertion hole 9 corresponds to the shape of the inserted magnet. However, the shape of the magnet insertion hole 9 may be changed as long as it can accommodate at least the permanent magnet 4 therein. Therefore, for example, a space to be a magnetic shield bridge may be formed in the magnet insertion hole 9. Further, a space or a flow path through which a cooling medium for cooling the magnet flows may be formed. For the sake of explanation, fig. 2 shows an XYZ rectangular coordinate system.
As shown in fig. 2A and 2B, the permanent magnet 4 has a substantially rectangular flat plate shape and has irregularities as described below. The "plate-like" magnet in the present embodiment is a magnet having main surfaces arranged to face each other and substantially parallel to each other. In the permanent magnet 4, a groove 41 is formed in one main surface 4a of the pair of main surfaces 4a and 4 b. The groove 41 extends in the axial direction (Z-axis direction) of the rotor in the vicinity of the center of the permanent magnet 4 in the longitudinal direction (X-axis direction).
the size of the permanent magnet 4 is appropriately selected according to the outer diameter, the number of poles, and the like of the rotor. In the permanent magnet 4, for example, the length of the long side (length in the X-axis direction) is in the range of 3mm to 70mm, and the thickness (length in the Y-axis direction) is in the range of 1mm to 40 mm.
In the groove 41, for example, the width L1 (length in the X-axis direction) is in the range of 1mm to 69mm, and the depth L2 (length in the Y-axis direction) is in the range of 1mm to 36 mm. The width L1 of the groove portion 41 ranges from 3% to 97% of the length of the permanent magnet 4 in the longitudinal direction when viewed along the longitudinal direction (X-axis direction) of the permanent magnet 4. The depth L2 of the groove 41 is in the range of 3% to 90% of the thickness of the permanent magnet 4.
In addition, in the permanent magnet 4, by providing the groove portion 41, the convex portion region 42 in which the thickness of the permanent magnet 4 is increased in the thickness direction (Y-axis direction length) compared to the region in which the groove portion 41 is formed. In the permanent magnet 4, the convex regions 42 are provided at both ends of the permanent magnet 4 in the longitudinal direction (X-axis direction), and extend along the axial direction (Z-axis direction) of the rotor, respectively. As described above, the permanent magnet 4 of the present embodiment has regions in which the thicknesses of the permanent magnets 4 are different from each other. The permanent magnet 4 has a concave shape having convex regions 42 formed at both ends as a cross-sectional shape (a plane parallel to the XY plane).
Fig. 3 is a partially enlarged view of fig. 1. The permanent magnets 4 are disposed as shown in fig. 3 by being accommodated in magnet insertion holes 9 provided in the core 7 of the rotor 3. In fig. 3, the magnet insertion hole 9 is omitted.
the permanent magnets 4 are arranged symmetrically with respect to an imaginary line a extending from the axis of the core 7. More specifically, the permanent magnets 4 are symmetrically arranged such that an angle formed by a straight line extending from the long side and the virtual line a is inclined by a predetermined angle (for example, about 45 ° to 85 °, which is not particularly limited). In this way, the permanent magnet 4 is housed in the magnet insertion hole 9 so as to face upward in fig. 2 (the Y-axis positive side) toward the outer peripheral side of the core 7. When housed in the magnet insertion hole 9, the permanent magnet 4 has a cross section perpendicular to the rotation axis of the rotor 3 (core 7) and parallel to the XY plane of the permanent magnet 4 in fig. 2.
As a result, as shown in fig. 3, the thickness of the permanent magnets 4 (the width of the permanent magnets 4 when viewed along the direction in which the long sides of the permanent magnets 4 extend on the main surface of the core 7) is increased in both the end portions on the side farther from the virtual line a (the side closer to the outer periphery of the rotor 3) and the end portions on the side closer to the virtual line a (the side closer to the inner periphery of the rotor 3) of the pair of permanent magnets 4.
The permanent magnet 4 can be fixed in the magnet insertion hole by appropriately filling the magnet insertion hole with the filler. As the filler, a thermosetting resin, for example, an epoxy resin, a silicone resin, or the like can be used. However, the permanent magnet 4 accommodated in the magnet insertion hole may be fixed to the magnet insertion hole, and the filler is not necessarily used.
The plurality of permanent magnets 4 attached to the rotor 3 may be permanent magnets made of the same material. The permanent magnet 4 of the present embodiment can be appropriately selected from a rare earth magnet, a ferrite magnet, an alnico magnet, and the like. The type of the permanent magnet 4 is not particularly limited, and in the case of a sintered magnet, the permanent magnet 4 can be produced by a simpler method as described later. However, a bond magnet may be used as the permanent magnet 4. The plurality of permanent magnets 4 may be made of different materials.
as the permanent magnet 4, for example, a rare earth permanent magnet can be used. The rare earth permanent magnet may be, for example, an R-T-B permanent magnet. Among them, R-T-B sintered magnets are possible. The R-T-B sintered magnet has grains (crystal grains) composed of R2T14B crystals and grain boundaries.
R in the R-T-B sintered magnet represents at least 1 type of rare earth element. The rare earth elements refer to Sc, Y and lanthanoid elements belonging to IIIB group of the long period periodic Table. Included among lanthanides are, for example, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and the like. T in the R-T-B sintered magnet represents Fe or Fe and Co. In addition, 1 or more kinds selected from other transition metal elements may be contained. In the R-T-B sintered magnet, B represents boron (B) or boron (B) and carbon (C).
The R-T-B sintered magnet of the present embodiment may contain Cu, Al, or the like. By adding these elements, the temperature characteristics of high coercivity, high corrosion resistance, or magnetic characteristics can be improved.
In the R-T-B sintered magnet according to the present embodiment, Dy, Tb, or both of them may be contained as the heavy rare earth element. Heavy rare earth elements may also be included in the grains and grain boundaries. In the case where the heavy rare earth element is not substantially contained in the crystal grain, it is preferably contained in the grain boundary. The concentration of the heavy rare earth element in the grain boundary is preferably higher than that in the crystal grain. The R-T-B sintered magnet of the present embodiment may be an R-T-B sintered magnet in which a heavy rare earth element is grain boundary diffused. The R-T-B sintered magnet in which the heavy rare earth element is grain boundary diffused can have a higher residual magnetic flux density and a higher coercive force with a smaller amount of the heavy rare earth element than those of the R-T-B sintered magnet in which the grain boundary diffusion is not generated. In the case where an R-T-B sintered magnet in which a heavy rare earth element is grain boundary diffused is used as the permanent magnet 4 of the present embodiment, a magnet in which a heavy rare earth element is grain boundary diffused in the entire magnet rather than in a part of the magnet can be used. By forming such a structure, productivity is improved and cost is reduced.
When the permanent magnet 4 of the present embodiment is an R-T-B-based permanent magnet, the R-T-B-based permanent magnet is not limited to the R-T-B-based sintered magnet produced by sintering as described above. For example, an R-T-B permanent magnet produced by hot forming and hot working instead of sintering may be used.
When a cold compact obtained by molding a raw material powder at room temperature is subjected to hot molding in which pressure is applied while heating, pores remaining in the cold compact disappear, and the cold compact can be densified regardless of whether or not it is sintered. Further, by subjecting the molded body obtained by the thermoforming to hot extrusion processing as hot working, an R-T-B-based permanent magnet having a desired shape and magnetic anisotropy can be obtained.
Next, a method for manufacturing the permanent magnet 33 used for the rotor 3 will be described with reference to fig. 4. Fig. 4 is a flowchart showing an example of the method for manufacturing permanent magnet 33. In fig. 4, the case where the permanent magnet 33 is a rare earth sintered magnet has been described, but the permanent magnet can be produced by the same method in the case of a ferrite sintered magnet.
First, fine metal powder (raw material powder) and resin, which are raw materials of the composition of the present embodiment, are prepared (step S11). The resin is preferably a thermoplastic resin, and for example, polypropylene, polystyrene, polyethylene, polyacetal, EVA resin, AS resin, ABS resin, or the like can be used. Further, additives such as paraffin wax and a plasticizer may be used as necessary.
Next, the resin is charged into the kneader (step S12). As the kneading machine, for example, a closed batch type kneading machine such as a planetary mixer or a pressure kneader can be used. The resin is charged into the kneading vessel of the kneader.
Next, the resin is heated and stirred in the kneading vessel, thereby heating and melting the resin (step S13). The conditions for heating and melting are not particularly limited, and are determined according to the kind of the resin and the like. Before the resin is heated and melted, the interior of the kneading vessel is preferably set to a low-oxygen atmosphere having an oxygen concentration of 200ppm or less. The method of forming the low-oxygen atmosphere is not limited, and a method of using a vacuum pump to perform evacuation and introduction of an inert gas in combination is exemplified. The shape of the resin to be charged into the kneading vessel is not particularly limited, and the resin may be charged in the form of resin pellets, for example. The amount of the resin is not particularly limited, and can be 3 to 15% by mass when the metal fine powder is 100% by mass.
During the heating and melting of the resin by the kneader, the atmosphere inside the kneading vessel is evacuated to perform a defoaming treatment of the resin (step S14). The method of the defoaming treatment is not particularly limited, and examples thereof include a method of reducing the pressure inside the kneading vessel by evacuation using a vacuum pump or the like. Further, the flow of inert gas in the interior of the reduced-pressure kneading vessel may be used in combination. When the interior of the kneading vessel is set to a low-oxygen atmosphere after the heating and melting, the low-oxygen atmosphere may be set by the same method as that used before the heating and melting, or may be set to a low-oxygen atmosphere by a different method.
next, the fine metal powder is charged into the kneading container (step S15). The fine metal powder is easily oxidized by oxygen contained in the ambient air, and therefore, a container for charging (pot) or the like, in which the inside is set to a low oxygen atmosphere in advance, may be used to prevent the oxidation.
After the metal fine powder is charged into the kneading vessel of the kneader, the heating inside the kneading vessel is continued and the metal fine powder is stirred together with the molten resin in the kneading vessel, thereby heating and kneading (step S16) to obtain an injection molding composition (composition for resin molded article containing metal powder). The heating temperature and the kneading time are not limited, and for example, the kneading is preferably carried out at 100 to 250 ℃ for 5 to 180 minutes.
next, the kneaded injection molding composition (composition for resin molded body containing metal powder) obtained by the production method of the present embodiment described above is fed into an injection molding machine and injection molded in an oriented magnetic field (step S17). The rare earth sintered magnet can be produced by performing the degreasing (binder removal) step (step S18) and the sintering step (step S19). The conditions of the injection molding step, the degreasing step, and the sintering step are not particularly limited.
The injection molding step is performed by injecting a composition for injection molding (a composition for resin molded article containing metal powder) while applying an orientation magnetic field to a molding die. By applying an orienting magnetic field, the molded body can be made to have magnetic anisotropy. The magnetic field strength and application time of the orientation magnetic field in the injection molding step are not particularly limited.
the degreasing step is performed by heating the molded article obtained by injection molding in an atmosphere such as vacuum, inert gas flow, inert gas reduced pressure, or hydrogen flow. The heating temperature and the heating time in the degreasing step are not particularly limited. The oxygen concentration of the atmosphere gas in the degreasing step can be set to, for example, 5ppm or less.
The sintering step is performed by heating the molded body obtained in the degreasing step in an atmosphere such as vacuum, inert gas flow, or inert gas reduced pressure. The sintering temperature and sintering time are not particularly limited and may be determined depending on the kind of the fine metal powder and the like. Then, aging treatment is performed as necessary.
The rare earth sintered magnet can be obtained by the above method. When the oxygen content of the rare earth sintered magnet is 2000ppm or less, a rare earth sintered magnet having a sintered density of 99.0% or more can be obtained. A rare earth sintered magnet having an oxygen content of 2000ppm or less and a sintered density of 99.0% or more can have very excellent characteristics.
The above steps are examples. The method of manufacturing permanent magnet 33 is not limited to the above method. Therefore, for example, the permanent magnet 33 may be manufactured by performing a recess forming process on the sintered magnet later.
as described above, the permanent magnet 4 of the present embodiment has a region with a thickness larger than that of the other regions on one end side. In the case of the permanent magnet 4, both end portions have the convex regions 42 when viewed in a cross section (a plane parallel to the XY plane). As a result, the convex portion region 42 becomes thicker than the other region (the region where the groove portion 41 is formed). In other words, the rotor 3 has a thick region on one end side in a cross section perpendicular to the rotation axis (a cross section parallel to the main surface of the core 7). With such a configuration, demagnetization of the region in which demagnetization is likely to occur can be suppressed.
in a motor having permanent magnets mounted thereon, a magnetic field (demagnetizing field) in a direction opposite to the magnetization direction of some of the magnets is applied by the rotation of a rotor. The region to which the demagnetizing field is applied varies depending on the arrangement of the permanent magnets, and the demagnetizing field is applied to the end portion on the rear side (the side opposite to the rotational direction) with respect to the rotational direction of the rotor. For example, when an arrow R shown in fig. 3 indicates a rotation direction of the rotor 3, it is considered that a demagnetizing field is applied to the vicinity of a right end of the right permanent magnet 4 of the two permanent magnets 4 shown in fig. 3. In this way, demagnetization of the permanent magnet may occur in the region where the demagnetization field occurs. In contrast, demagnetization is conventionally prevented by increasing the coercive force of a material containing a heavy rare earth element or the like in a magnet material. However, heavy rare earth elements are expensive, resulting in an increase in material cost of the magnet. In view of this, it has been studied to contain a heavy rare earth element only in a partial region by diffusion or the like of a heat treatment, but it cannot be said that the manufacturing cost of the permanent magnet can be sufficiently suppressed since the material cost of containing the heavy rare earth element is expensive and the heat treatment is required.
On the other hand, the permanent magnet 4 of the present embodiment has the convex regions 42 on both end sides. That is, by forming a region in which the thickness of the permanent magnet 4 is large in a cross section perpendicular to the rotation axis of the rotor 3 on at least one end portion side, the magnetic permeability of the permanent magnet 4 can be adjusted. The magnetic permeability is a coefficient that changes according to the ratio of the thickness of the magnetization direction of iron to the width of the magnet in the direction perpendicular to the magnetization direction of the magnet (in fig. 2, the length in the X axis direction when the magnetization direction is the Y axis direction). In addition, in the magnet, a region having a small magnetic permeability is easily affected by a demagnetizing field or the like, and demagnetization easily occurs. Therefore, in the permanent magnet 4, by providing the region (the convex region 42) having a large thickness on the side of the one end portion which is likely to receive the demagnetization field in the permanent magnet 4, local demagnetization occurring when the rotor 3 rotates can be suppressed when the permanent magnet 4 is attached to the rotor 3. That is, by disposing a region of the permanent magnet 4 having a large thickness in a region where a demagnetization field is likely to be applied, demagnetization in this region can be suppressed.
Further, by providing a region having a large thickness in the permanent magnet 4 having the groove portion 41 and the convex portion region 42, the magnetic flux on the surface of the permanent magnet 4 can be concentrated on the convex portion region 42. As a result, demagnetization can be suppressed in this region.
Fig. 5 shows the results of evaluating the change in the magnetic flux generated on the surface of the permanent magnet 4 by providing the groove portion 41. Fig. 5 shows the magnitude of change in magnetic flux density when measuring the magnetic flux density of the surface (the surface of the periphery on the main surface 4a side) of the permanent magnet 4 detected by the hall element when the hall element is moved in the longitudinal direction of the permanent magnet 4. As the permanent magnet 4, a permanent magnet having a length in the longitudinal direction (X-axis direction) of 14mm and a thickness of 4mm was used. The main surface 4a or the main surface 4b is formed in a semicircular shape, includes a longitudinal center, has a predetermined width, and has a groove portion having a depth of half the width. When the width of the groove was varied from 1.0mm to 4.0mm by 1.0mm and the depth of the corresponding groove was varied from 0.5mm to 2mm by 0.5mm, the difference in the intensity of the magnetic flux density between the end portion and the central portion was measured.
First, when the groove portion is not formed in the permanent magnet 4, it is confirmed that the difference in the intensity of the magnetic flux density between the end portion and the central portion is small. On the other hand, when the groove portion 41 is increased, the difference in intensity of the magnetic flux density between the end portion (the convex portion region where the groove portion is not formed) and the central portion (the region where the groove portion is formed) is increased. In particular, when the groove 41 is formed on the main surface 4a side on which the hall element is moved, it is confirmed that the greater the width of the groove 41, the greater the difference in the intensity of the magnetic flux density. In the case where the groove portion 41 is formed in the main surface 4b on the opposite side to the main surface 4a for moving the hall element, it is confirmed that the greater the width of the groove portion 41, the greater the difference in the intensity of the magnetic flux density. However, the difference in the intensity of the magnetic flux density is smaller than that in the case where the magnetic flux density is provided on the main surface 4a side.
By providing the groove 41 in this way, the magnetic flux density on the surface of the permanent magnet 4 can be controlled, and in particular, the magnetic flux density in the convex region (the region where the groove 41 is not provided) can be increased. Therefore, demagnetization can be suppressed.
When the width L1 of the groove portion 41 is 3% to 97% of the length of the permanent magnet 4 in the longitudinal direction when viewed along the longitudinal direction (X-axis direction) of the permanent magnet 4, the effect of suppressing demagnetization by concentration of the magnetic flux is further enhanced. The depth L2 of the groove 41 is set to be in the range of 3% to 90% of the thickness of the permanent magnet 4. By setting the depth L2 to the above range, the effect of suppressing demagnetization by concentration of the magnetic flux is further improved. However, if the groove 41 is excessively increased, the effect of suppressing demagnetization is enhanced, but the volume of the entire permanent magnet 4 may be reduced, and the magnetic force may become insufficient. Therefore, by setting the above range, the effect of suppressing demagnetization is enhanced while the function as a permanent magnet is exhibited.
The permanent magnet 4 has a larger surface area than a conventional flat permanent magnet having no convex portion 42. Therefore, the contact area with the cooling medium for cooling or the like becomes large, and the heat radiation effect is improved. Since the rotor 3 and the motor 1 to which the permanent magnet 4 is attached are likely to have high temperatures, it is considered that the permanent magnet 4 may also have a high temperature. In particular, the region where the demagnetizing field is generated is also a region where the temperature rises sharply. In contrast, since the permanent magnet 4 has the groove portion 41 and the convex portion region 42, and the surface area is increased, the cooling effect of the cooling medium such as oil filled around the permanent magnet 4 is improved, and the temperature rise is suppressed. Further, the above-described demagnetization suppressing effect can be improved by suppressing the temperature rise. Furthermore, the heat resistance required of the permanent magnet 4 can be reduced by suppressing the temperature rise of the permanent magnet 4. Therefore, the amount of heavy rare earth metals added to improve heat resistance can be reduced, and the material cost of the permanent magnet 4 can be reduced.
Further, since the permanent magnet 4 is integrally formed, it is easily inserted or assembled into the magnet insertion hole 9. In addition, in the case where the permanent magnet 4 having the groove portion 41 and the convex portion region 42 is manufactured by injection molding, cost reduction can be achieved as compared with the case where the permanent magnet is manufactured by cutting or the like. When the sintered magnet is subjected to cutting, the manufacturing cost may be increased. In contrast, the manufacturing method using injection molding can reduce the cost.
The "one end portion side" in the cross section perpendicular to the rotation axis of the rotor 3, in which the thickness of the permanent magnet 4 is increased, means that the region in which the thickness of the permanent magnet 4 is increased in the cross section perpendicular to the rotation axis of the rotor 3 is not provided near the center of the permanent magnet 4 but is provided near the end portion. In the permanent magnet of the present embodiment, the region having a large thickness is formed in the one end portion and the region where the magnet 4B extends from the one end portion, but the "region having a large thickness" need not be provided so as to include the one end portion of the permanent magnet. For example, the inside region may be a region "thicker" than the end portion by rounding the corner portion of the permanent magnet 4.
Fig. 6A to 6C and fig. 7 show an example of deforming the shape of the permanent magnet 4. Fig. 6A to 6C are sectional views (sectional views of a section perpendicular to the rotation axis of the rotor) of permanent magnets showing modifications.
The permanent magnet 11 shown in fig. 6A is a permanent magnet in which the groove 41 is provided on both the pair of main surfaces 11a and 11 b. In this way, even when the groove 41 is provided on both the pair of main surfaces 11a and 11b, the effect of suppressing demagnetization is enhanced as in the case of the permanent magnet 4. When the grooves 41 formed on both the pair of main surfaces 11a and 11b have the same shape and are provided at the centers of the main surfaces 11a and 11b, the permanent magnet 11 has a vertically symmetrical and horizontally symmetrical cross-sectional shape. In the case where the permanent magnet 11 has the above-described shape, it is not necessary to consider the insertion direction or the like when inserting the permanent magnet 11 into the magnet insertion hole 9. That is, since the insertion direction of the permanent magnet 11 can be prevented from being mistaken, the work efficiency of assembling the motor 1 can be improved.
the groove portion of the permanent magnet 12 shown in fig. 6B has a different shape. That is, the groove 45 provided in the permanent magnet 12 is formed in a wave shape in which a plurality of concave shapes are combined. When the groove 45 has such a shape, the convex portion region 42 is formed in the permanent magnet 12, as in the case of other permanent magnets, and therefore the above-described effect of suppressing demagnetization can be obtained. Further, in permanent magnet 12, since groove 45 is formed in a wave shape, the surface area of permanent magnet 12 is increased as compared with permanent magnet 4. Therefore, the cooling effect of the surrounding cooling medium or the like is improved, and thus the effect of suppressing demagnetization by suppressing heat generation is also obtained.
In the permanent magnet 13 shown in fig. 6C, a through hole is provided instead of the groove portion in order to provide the convex portion region 42. The through hole 47 is provided in the center of the permanent magnet 13 and extends in the direction of the rotation axis of the rotor 3. By providing such through-holes 47, the thickness of the central portion of the permanent magnet 13 is reduced, and the thickness is substantially increased because the through-holes 47 are not provided at both end portions. In the case of such a shape, since the regions having a large thickness are formed on both end sides, demagnetization can be suppressed even when the rotor 3 of the motor 1 is mounted. Further, since the cooling effect is enhanced by flowing a cooling medium such as oil through the through-hole 47, the effect of suppressing demagnetization by heat generation is also obtained.
Fig. 7 is a perspective view of a permanent magnet 14 according to a modification. Permanent magnet 14 differs from permanent magnet 4 in that a recess 81 is formed as a structure corresponding to groove portion 41. The recessed portion 81 is not a recessed portion that penetrates in the rotation axis direction of the rotor 3 like the groove portion 41, but convex portions 82 and 83 are formed around the recessed portion. In such a permanent magnet 14, the cross-sectional shape is the same as that of the permanent magnet 4 except for the regions at both ends of the rotor 3 in the rotation axis direction (see fig. 2B), but the concave portions 81 do not have the cross-sectional shape but only become convex regions 83 at both ends of the rotor 3 in the rotation axis direction. In such a permanent magnet 14, since a region having a large thickness (convex regions 82 and 83) is formed on the end portion side in the region where the concave portion 81 has the cross-sectional shape, the effect of suppressing demagnetization can be obtained.
As described above, according to the permanent magnet 4 of the present embodiment and the motor 1 having the permanent magnet 4 mounted thereon, the magnetic flux density on the surface of the permanent magnet 4 can be adjusted by forming the region having a large thickness of the permanent magnet 4 on the one end side. Therefore, if a region having a large thickness is provided on one end portion side of the permanent magnet 4, local demagnetization occurring when the rotor 3 rotates can be suppressed when the permanent magnet 4 is attached to the rotor 3. The permanent magnet 4 is excellent in handling properties because it is formed of 1 permanent magnet.
Further, when the permanent magnet 4 is attached to the rotor 3, a portion of the main surface disposed outside the rotor 3 is projected to form a region having a large thickness, whereby the influence of local demagnetization can be appropriately suppressed outside the rotor.
The thick region may be formed by irregularities provided on at least one of the pair of main surfaces 4a and 4b of the permanent magnet 4. By providing the irregularities on at least one main surface in this manner, a region having a large thickness can be formed, and the surface area of the permanent magnet 4 can be increased. Therefore, the heat radiation effect can be improved, and local demagnetization caused by rotation of the rotor can be suppressed.
Among the permanent magnets attached to the rotor 3 of the motor 1 to constitute magnetic poles, the permanent magnet 4 at the end portion on the rear side with respect to the rotational direction is susceptible to local demagnetization during rotation. Therefore, as described in the above embodiment, by configuring the permanent magnet 4 at the end portion on the rear side with respect to the rotation direction to have a region having a thickness larger than the other regions on the side of one end portion, local demagnetization during rotation can be appropriately suppressed.
In addition, in the case of the configuration in which the 2 permanent magnets 4 constituting the same magnetic pole are symmetrically arranged with respect to the virtual line a and each have a region having a larger thickness than the other regions on the end portion side farther from the virtual line in the cross section orthogonal to the rotation axis of the rotor, local demagnetization at the time of rotation that may occur at the end portion on the rear side with respect to the rotation direction can be appropriately suppressed regardless of the rotation direction of the rotor. Further, when all of the plurality of magnetic poles provided on the rotor 3 have the above-described configuration, the permanent magnets 4 having the same shape are inserted into all of the magnet insertion holes provided on the rotor 3. In this case, the assembling workability of the motor 1 is also improved.
The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the invention.
For example, the number of magnet insertion holes provided in the motor can be increased or decreased as appropriate, and the positional relationship with respect to the magnet insertion holes can be changed as appropriate.
In the above-described embodiment, the case where the permanent magnet has the regions having the larger thickness than the other regions on both end sides has been described, but the regions having the larger thickness than the other regions may be provided on at least one end side. That is, in the permanent magnet 4 shown in fig. 2, the convex regions 42 are provided on both end sides, but one of the convex regions 42 may be flat at the same height as the groove 41. Even if the rotor is formed in such a shape, an effect of suppressing demagnetization when attached to the rotor 3 can be obtained.
Claims (7)
1. A permanent magnet to be mounted to a rotor of an electric motor,
Which is composed of a permanent magnet having concavities and convexities,
the rotor has a region having a thickness larger than other regions on one end side in a cross section perpendicular to a rotation axis of the rotor when attached to the rotor.
2. the permanent magnet according to claim 1,
When the permanent magnet is attached to the rotor, the thick region is formed by projecting a part of a main surface of the permanent magnet disposed outside the rotor.
3. The permanent magnet according to claim 1,
The rotor has the regions with a large thickness on both end sides in a cross section perpendicular to a rotation axis of the rotor when attached to the rotor.
4. A permanent magnet according to any one of claims 1 to 3,
The region having a large thickness is formed by irregularities provided on at least one of a pair of main surfaces of the permanent magnet.
5. An electric motor, comprising:
A rotor having a plurality of magnet insertion holes, and
A plurality of permanent magnets respectively received in the plurality of magnet insertion holes,
The permanent magnets have projections and recesses in a part thereof, and have a region having a thickness larger than other regions on one end side in a cross section perpendicular to a rotation axis of the rotor when the permanent magnets are attached to the rotor.
6. The motor according to claim 5, wherein,
The plurality of magnet insertion holes are periodically arranged around a rotation axis of the rotor,
The magnetic poles of the rotor are formed by permanent magnets inserted into one or more continuous magnet insertion holes among the plurality of magnet insertion holes,
Among the permanent magnets constituting the magnetic poles, the permanent magnet disposed at the end on the rear side with respect to the rotational direction of the rotor has a region having a thickness larger than other regions on one end side in a cross section orthogonal to the rotational axis of the rotor.
7. The motor according to claim 5, wherein,
The plurality of magnet insertion holes are periodically arranged around a rotation axis of the rotor,
The magnetic poles of the rotor are formed by two permanent magnets inserted into two consecutive magnet insertion holes among the plurality of magnet insertion holes,
The two permanent magnets constituting the magnetic pole are arranged symmetrically with respect to an imaginary line,
The two permanent magnets have a region with a thickness larger than that of other regions on one end side farther from the imaginary line in a cross section perpendicular to the rotation axis of the rotor.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2018-101821 | 2018-05-28 | ||
| JP2018101821A JP7263698B2 (en) | 2018-05-28 | 2018-05-28 | permanent magnets and motors |
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| Publication Number | Publication Date |
|---|---|
| CN110544570A true CN110544570A (en) | 2019-12-06 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201910417170.2A Pending CN110544570A (en) | 2018-05-28 | 2019-05-20 | Permanent magnet and motor |
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| JP (1) | JP7263698B2 (en) |
| CN (1) | CN110544570A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2020096411A (en) * | 2018-12-10 | 2020-06-18 | 本田技研工業株式会社 | Rotor and production method of arc-like magnets for rotor |
| JP7083170B2 (en) * | 2019-11-18 | 2022-06-10 | 株式会社ニューギン | Pachinko machine |
| JP7083171B2 (en) * | 2019-11-18 | 2022-06-10 | 株式会社ニューギン | Pachinko machine |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101682221A (en) * | 2007-05-11 | 2010-03-24 | 丰田自动车株式会社 | Rotor of rotary electric machine, and production method therefor |
| CN102347656A (en) * | 2010-07-27 | 2012-02-08 | 富士电机株式会社 | Permanent magnet type rotary machine |
| CN103026585A (en) * | 2010-07-23 | 2013-04-03 | 丰田自动车株式会社 | Rotor and IPM motor |
| CN104871409A (en) * | 2012-12-21 | 2015-08-26 | 三菱电机株式会社 | Permanent magnet buried type electric motor and compressor |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2012139068A (en) * | 2010-12-27 | 2012-07-19 | Mitsubishi Electric Corp | Rotor for embedded magnet type motor |
| JP2015192587A (en) * | 2014-03-31 | 2015-11-02 | ダイキン工業株式会社 | rotor |
| JP2018129938A (en) * | 2017-02-08 | 2018-08-16 | 本田技研工業株式会社 | Rotary electric machine |
| JP6852575B2 (en) * | 2017-06-05 | 2021-03-31 | 株式会社デンソー | An electric motor equipped with a rotor for an electric motor and a rotor for an electric motor |
-
2018
- 2018-05-28 JP JP2018101821A patent/JP7263698B2/en active Active
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2019
- 2019-05-20 CN CN201910417170.2A patent/CN110544570A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101682221A (en) * | 2007-05-11 | 2010-03-24 | 丰田自动车株式会社 | Rotor of rotary electric machine, and production method therefor |
| CN103026585A (en) * | 2010-07-23 | 2013-04-03 | 丰田自动车株式会社 | Rotor and IPM motor |
| CN102347656A (en) * | 2010-07-27 | 2012-02-08 | 富士电机株式会社 | Permanent magnet type rotary machine |
| CN104871409A (en) * | 2012-12-21 | 2015-08-26 | 三菱电机株式会社 | Permanent magnet buried type electric motor and compressor |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2019208306A (en) | 2019-12-05 |
| JP7263698B2 (en) | 2023-04-25 |
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Application publication date: 20191206 |