JP5640678B2 - IPM motor rotor and IPM motor - Google Patents

Description

  The present invention relates to an IPM motor rotor and an IPM motor including the rotor.

  Among various motors including a brushless DC motor, a motor (hereinafter referred to as an IPM motor) having a permanent magnet embedded rotor in which a plurality of permanent magnets are embedded in a rotor core is well known. For example, this IPM motor is used as a drive motor for a hybrid vehicle or an electric vehicle.

  By the way, a coil is formed in the stator teeth by concentrated winding or distributed winding. A magnetic flux is generated by applying a current to the coil, and magnet torque and reluctance are generated between the stator teeth and the magnetic flux generated by the permanent magnet. Torque is generated. In the case of this distributed winding coil, the number of magnetic poles is larger than in the case of the concentrated winding coil. Therefore, the magnetic flux (or change in magnetic flux) that enters the permanent magnet of the rotor from the teeth side when the rotor rotates is relative. Has continuity. Therefore, the change of the magnetic flux density at the time of rotor rotation is relatively small. On the other hand, in the case of concentrated winding coils, the change in magnetic flux density is relatively large, so eddy currents are likely to be generated in the permanent magnets. The generation of eddy currents causes the permanent magnets to generate heat, and irreversible thermal demagnetization occurs. Inviting the magnetic properties of the permanent magnet itself will be reduced.

  Speaking of drive motors used in recent hybrid vehicles and electric vehicles, for example, the number of revolutions and the number of poles have been increased while the improvement in motor output performance has been pursued. As a result, the fluctuation rate of the magnetic field acting on the magnet increases due to an increase, and as a result, the eddy current is likely to occur, and the motor performance is adversely deteriorated due to the thermal demagnetization of the magnet caused by heat generation, and the durability of the motor is reduced. The problem that it leads to is generated.

  In order to prevent the generation of the eddy current and the induction of thermal demagnetization, the permanent magnet is formed from a plurality of divided pieces, and the divided pieces are bundled into a magnet slot. Measures for insertion are taken (for example, see Patent Document 1).

  The above-described divided pieces are manufactured by separately manufacturing each divided piece, or machining a permanent magnet formed into an inner space shape and an inner space size of a magnet slot into which a permanent magnet is to be inserted into a plurality of divided pieces ( Cutting). From the viewpoint of manufacturing efficiency and manufacturing cost, it can be said that the latter processing method is generally performed. In this machining, for example, an expensive cutting blade with a diamond tip attached to the outer peripheral side of a super steel disk is necessary. However, since this cutting blade is a consumable part, it must be replaced periodically. As the number of blades increases, the frequency of blade replacement increases, and so on, and maintenance labor and manufacturing costs are rising. Moreover, since the magnet material equivalent to the thickness of the cutting blade is removed by pushing the blade when cutting, there is a problem that the material yield is reduced.

  Furthermore, the method of cutting a permanent magnet by the above machining has the following problems. That is, rare earth magnets such as neodymium magnets, which are permanent magnets, and ferrite magnets have a metal structure composed of a main phase contributing to magnetization and a grain boundary phase contributing to coercive force. When this permanent magnet is divided while being cut by machining, the cutting line at the time of cutting often cuts the main phase of the metal structure, so the cut main phase is smaller than before cutting, This causes a decrease in the residual magnetic flux density as compared to before cutting. Furthermore, the grain boundary phase expresses a coercive force with respect to the main phase covered by the grain boundary phase, but the main phase in contact with the cut surface is broken by the coating of the grain boundary phase. It becomes easy to cause magnetization reversal, and this magnetization reversal phase becomes a starting point to reduce the coercive force of the whole magnet.

  Therefore, Patent Document 2 discloses a method of manufacturing a split magnet (cleaved magnet) by cleaving a permanent magnet instead of machining. The split magnet disclosed here is one in which a permanent magnet is cut, restored, and inserted into a magnet slot.

  By the way, whether it is the above-mentioned divided magnet that has been mechanically cut or a divided magnet that has been cut, it is disposed in the magnet slot in a posture in which the cut surfaces or split sections of the adjacent divided magnets are in close contact with each other. Therefore, the present inventors have specified that the magnet area that should have reduced the magnetic flux passage area in the division is likely to be the same as that before the division, and the effect of reducing the vortex loss due to the division is not sufficiently obtained. .

  And this inventor etc. also specified that this problem is more remarkable in the case of the above-mentioned cleaved magnet, because the cleaved surfaces of the cleaved divided magnets are three-dimensionally fitted and adhered. Yes.

  By applying the rotor structure disclosed in Patent Document 3 to the above problem, a structure in which the divided surfaces of the divided magnets are not brought into contact with each other can be obtained. In the rotor structure disclosed in Patent Document 3, three divided magnets are disposed in a rotor slot having a concave shape in one plan view per pole. Since the rotor slot is concave, adjacent divided magnets are used. It is possible to eliminate the contact between the two at the dividing surface. However, the rotor disclosed in Patent Document 3 has a problem of reducing the cogging torque, and the problem is to reduce the eddy loss generated in the permanent magnet described above. Absent.

  Further, in each of the rotors disclosed in Patent Documents 1 to 3, a magnet is disposed in one rotor slot per pole. Accordingly, two magnet slots are formed in a substantially V-shape, and magnets are arranged in each magnet slot to form one pole, which is formed at intervals in the circumferential direction of the rotor. Therefore, it is unclear whether the techniques disclosed in these documents can be applied to this type of rotor.

Japanese Patent Laid-Open No. 11-4555 JP 2009-33958 A JP 2002-223538 A

  The present invention has been made in view of the above-mentioned problems, and two magnet slots are formed in a substantially V shape, and magnets are arranged in each magnet slot to form a pole. With respect to a rotor for an IPM motor formed at intervals in the circumferential direction, it is possible to eliminate the fact that the divided surfaces or split sections of the divided magnets inserted into each slot are in close contact with each other. An object of the present invention is to provide an IPM motor rotor capable of effectively reducing vortex loss by guaranteeing a small magnetic flux passage area and an IPM motor including the rotor.

  In order to achieve the above object, in the rotor for an IPM motor according to the present invention, in the rotor, two magnet slots are formed in a substantially V shape, and a magnet is arranged in each magnet slot to form one pole. This is a rotor for an IPM motor formed at intervals in the circumferential direction of the rotor, and the magnet slot has a substantially curved shape convex toward the center of the rotor in plan view, and a plurality of slots are provided in the magnet slot. The divided magnets are arranged so that adjacent divided magnets are in contact with each other only at one point on the rotor side surface in a plan view.

  The rotor for an IPM motor of the present invention is intended for a rotor in which a split magnet (including a cleaving magnet) is disposed in each of two magnet slots opened in a substantially V shape to form one magnetic pole. Each slot has a substantially curved shape convex toward the center of the rotor in a plan view, so that adjacent divided magnets are in contact with each other only at one point on the side of the rotor in a plan view. It is a rotor that can eliminate this. A single magnetic pole is composed of a plurality of divided magnets arranged in each of two magnet slots opened in a substantially V shape, thereby ensuring a smooth flow of magnetic flux entering the rotor from the stator side. The torque performance is improved as compared with a rotor structure in which a plurality of divided magnets are disposed in one magnet slot per pole.

  As one shape form of the magnet slot, the substantially curved shape is formed from at least two linear sections that are inclined with respect to each other in a plan view, and a split magnet (a cleaving magnet) having a linear length of each linear section in the plan view. Is disposed in the slot of the corresponding straight section, it can be ensured that the adjacent divided magnets are in contact with each other only at one point on the rotor side surface in a plan view. For example, when one slot is formed from two linear sections inclined with respect to each other, two divided magnets are respectively disposed in two slots for two magnets having a substantially V shape, and three slots inclined with respect to each other are arranged. When one slot is formed from the straight section, three divided magnets are disposed in each slot.

Here, the magnet (permanent magnet) disposed in the rotor of the present invention includes a rare earth magnet, a ferrite magnet, an alnico magnet, and the like. The term “permanent magnet” as used herein means a sintered body before magnetization or just a green compact in addition to the rare earth magnet after magnetization. Examples of the rare earth magnet include a ternary neodymium magnet obtained by adding iron and boron to neodymium, a samarium cobalt magnet made of a binary alloy of samarium and cobalt, a samarium iron nitrogen magnet, and a praseodymium magnet. Among these, rare earth magnets have a maximum energy product (BH) _max higher than that of ferrite magnets or alnico magnets, and therefore are suitable for application to drive motors such as hybrid vehicles that require high output.

  Since the magnet slot described above has a substantially curved shape convex toward the rotor center in plan view, when the divided magnets are disposed in the slot, the adjacent divided magnets are in contact with each other on the rotor side surface side. At the same time, the distance from each other increases toward the center of the rotor, and a substantially triangular gap is formed as a whole in plan view. This gap may be left as an air gap or may be filled with an insulating resin. Particularly in the latter case, the posture of each divided magnet can be more firmly fixed by the cured insulating resin.

  When the split magnet is a cleaved magnet, the cleaved magnet is provided with, for example, a predetermined number of notches on one side of one magnet and cleaves with the notch as a cleave starting point. The cutting line that can be formed on the other side is often formed as a result. That is, one of the cleaved magnets that is cleaved is wide on the other side of the magnet, and the other cleaved magnet that is cleaved is likely to be narrow on the other side of the magnet.

  Thus, even when a cleaved magnet that has been cleaved so that the width of the other side of the magnet without a cleave starting point such as a notch is widened, the side surface on the wide side should be within the gap of the above-described triangle. Therefore, especially in the case of a cleaved magnet, the magnet slot shape constituting the rotor of the present invention described above is effective. Further, in the case of a cleaving magnet, the contact resistance of a magnet formed by adhering adjacent cleaved magnets is lower than that of a magnet formed by adhering divided magnets by mechanical cutting. Since the vortex loss tends to increase due to the close contact, the rotor structure of the present invention is suitable when the split magnet is a cleaved magnet.

  In a preferred embodiment of the rotor for an IPM motor according to the present invention, the angle between the two divided magnets is adjusted to 9 degrees or more around the one point where the adjacent divided magnets are in contact with each other. .

  The inventors have created an analysis model in a computer by varying the angle between adjacent divided magnets, that is, the central angle of the above-described substantially triangular gap, and conducted a magnetic field analysis to obtain the optimum distance between the divided magnets. The angle of was verified. As a result, compared with the comparative example in which the divided magnets having the conventional structure are disposed in the slots, the angle between the divided magnets is more than 9 degrees as the effect of reducing the vortex loss while ensuring the insulation between the magnets. I have specified that.

  Furthermore, in a preferred embodiment of the rotor for an IPM motor according to the present invention, the height of the divided magnet in the rotor axial direction is longer than the width of the divided magnet in the circumferential direction of the rotor.

  For example, the magnitude of vortex loss caused by the magnetic flux passing through the side surface of a rectangular magnet is determined by the size of the short side of this side surface. Therefore, when two or more divided magnets are inserted into a magnet slot having a substantially curved shape that is convex toward the center of the rotor in plan view, the height of the divided magnet in the rotor axial direction is the rotor of the divided magnet. By designing it to be longer than the width in the circumferential direction, a greater eddy loss reduction effect can be expected.

  Furthermore, the present invention extends to an IPM motor comprising the rotor described above and a stator disposed around the rotor. Since the vortex loss that can occur in the magnet can be effectively reduced by applying the rotor described above, the torque performance and rotational performance of the IPM motor including this rotor are improved. Therefore, the production of this IPM motor has recently been expanded, and is suitable for, for example, a drive motor of a hybrid vehicle or an electric vehicle that requires high performance for the mounted equipment.

  As can be understood from the above description, according to the rotor for an IPM motor of the present invention and the IPM motor including the rotor, two magnet slots are formed in a substantially V shape, and a magnet is arranged in each magnet slot. The rotor for an IPM motor is provided with one pole and is formed at intervals in the circumferential direction of the rotor. The magnet slot has a substantially curved shape that is convex toward the center of the rotor in plan view. A plurality of divided magnets are arranged in the slot for use, and adjacent divided magnets are in contact with each other only at one point on the rotor side surface in a plan view, so that vortex loss that can occur in the magnet can be effectively reduced. Therefore, it can be used for an IPM motor excellent in torque performance and rotational performance.

It is the top view which showed the rotor for IPM motors of this invention partially. (A) is the top view which expanded the slot for magnets, (b) is a perspective view which shows a division | segmentation magnet. (A) is a perspective view which shows the magnet before cleaving, (b) is a perspective view which shows a cleaving magnet. It is a top view which shows the state by which the cleaving magnet shown by FIG. 3b was arrange | positioned in the slot for magnets. It is a graph which shows a magnetic field analysis result.

  Embodiments of the present invention will be described below with reference to the drawings. The illustrated rotor for the IPM motor shows only one magnetic pole composed of two substantially V-shaped magnet slots and divided magnets arranged in the respective magnet slots. Of course, the magnetic poles are arranged in a desired number of magnetic poles at intervals in the circumferential direction of the rotor.

  FIG. 1 is a plan view partially showing a rotor for an IPM motor according to the present invention, FIG. 2a is a plan view enlarging a slot for magnets, and FIG. 2b is a perspective view showing split magnets.

  The IPM motor shown in FIG. 1 is composed of a substantially annular yoke in plan view and teeth projecting radially inward from the yoke, and a stator 4 formed by laminating electromagnetic steel plates, and wound around the teeth. The coil 5 and a rotor 1 that is rotatably arranged inside the stator 4 and is formed by laminating disc-shaped electromagnetic steel plates,.

  In the rotor 1, a drive shaft slot is opened at the rotor center 1c, and a magnet slot 1b extending in a direction along the rotor center 1c is opened at a peripheral portion of the rotor 1 by a predetermined number of magnetic poles. A plurality of divided magnets 2,... Are inserted into the magnet slot 1b.

  This segmented magnet is composed of permanent magnets such as rare earth magnets, ferrite magnets, and alnico magnets. As the rare earth magnets, a ternary neodymium magnet obtained by adding iron and boron to neodymium, and a two-component system composed of samarium and cobalt. Any one of alloy samarium cobalt magnet, samarium iron nitrogen magnet, praseodymium magnet, etc. can be applied.

  Here, one magnetic pole provided in the rotor 1 has two magnet slots 1b and 1b opened in a substantially V shape, and each of the magnet slots 1b and 1b has three divided magnets 2 in the illustrated example. Are arranged. Since one magnetic pole is composed of a plurality of divided magnets 2,... Disposed in each of two magnet slots 1b, 1b opened in a substantially V shape, the rotor 1 is entered from the stator 4 side. A smooth flow X of magnetic flux is ensured, and torque performance can be improved as compared with a rotor structure in which a plurality of divided magnets are disposed in one magnet slot per pole.

  In addition, the two magnet slots 1b and 1b each having a substantially V shape have a substantially curved shape that protrudes toward the rotor center 1c in a plan view, unlike a conventional general rectangular shape in a plan view. The adjacent divided magnets 2 and 2 are in contact with each other only at one point 1b 'on the rotor side surface 1a side in a plan view, and the divided magnets 2 and 2 are in close contact with each other over the entire divided surface. It is not.

  In the illustrated example, the substantially curved shape is formed of three linear sections 1b1, 1b2, and 1b3 that are inclined with respect to each other in a plan view, and has a linear length (both length t1) in each linear section in a plan view. Is disposed in the slot of the corresponding straight section to ensure that the adjacent divided magnets 2 and 2 are in contact with each other only at one point 1b 'on the rotor side surface in a plan view. The straight sections may be different in length from each other. In addition to the magnet slots composed of the three straight sections inclined to each other as in the illustrated example, the two straight sections inclined to each other. There are a variety of planar shapes such as a magnet slot, a magnet slot composed of four or more linear sections inclined to each other, and a curved magnet slot. In particular, in the case of a magnet slot composed of a plurality of linear sections that are inclined with respect to each other as in the illustrated example, each of the divided magnets is automatically inserted by inserting a split magnet according to the length and dimension of each linear section. In-slot fixing is ensured, and one-point contact on the side surface of the rotor can be ensured.

  It is eliminated that the divided surfaces of the divided magnets 2 and 2 inserted in the magnet slots 1b are in close contact with each other, thereby ensuring a small magnetic flux passage area of the divided magnets 2 and effective eddy loss. Can be reduced.

  When the divided magnets 2, 2, 2 are inserted into the respective straight sections 1 b 1, 1 b 2, 1 b 3 of the magnet slot 1 b, the gap between the divided magnets 2, 2 is naturally a substantially triangular gap (insulating region indicated by the oblique lines in FIG. 2a). R) is formed, and the straight sections 1b1, 1b2, 1b3 are inclined with respect to each other at an angle θ about the contact 1b ′ of the divided magnets 2, 2.

  This gap may be an air gap without filling anything, but by filling and hardening the insulating resin 3 in the gap as in the illustrated example, the fixing of the divided magnet 2 in the slot becomes more rigid, and the rotor rotates. The problem of the noise etc. by the shift | offset | difference of the divided magnet 2 and the divided magnets 2 and 2 colliding with each other can be solved.

  It should be noted that the curved projecting regions at both ends of the magnet slot 1b are slots for reducing leakage magnetic flux from the split magnet and fixing the split magnet from the end by filling and curing the insulating resin here. It is an area.

  Further, as shown in FIG. 2b, the divided magnet 2 inserted into the magnet slot 1b has a height t2 in the rotor axial direction longer than a width t1 in the rotor circumferential direction of the divided magnet 2, and the magnetic flux J The magnitude of the eddy loss that can occur on the side surface A of the magnet passing through is defined by the short side length t1 of the magnet area A.

  Next, the case where a split magnet consists of a split magnet is demonstrated.

  As described above, by applying the cleaving magnet, the magnet material equivalent to the thickness of the cutting blade is removed by pressing the blade during cutting, as in the case of manufacturing a divided magnet by mechanically cutting a permanent magnet piece. The problem that the material yield decreases and the problem that the cutting blade requires maintenance are also solved. Furthermore, since the problem of cutting the main phase constituting the metal structure of the magnet cannot occur, this does not reduce the residual magnetic flux density, and the grain boundary that covers the main phase and contributes to the development of coercive force. Since the phase is not broken by the cutting blade, there are many advantages that the magnetization reversal with respect to the external magnetic field does not easily occur and the coercive force of the entire magnet is not lowered.

  In FIG. 3, an example of the manufacturing method of a cleaving magnet is simulated. There are a wide variety of methods for manufacturing the cleaving magnet, such as a method of irradiating a laser on one side of the permanent magnet piece, or a predetermined number of notches 2'a on one side of the magnet piece 2 'before cleaving as shown in FIG. There is a method in which the notch 2′a is used as a starting point for cleaving, and the magnet piece 2 ′ is cleaved while being bent.

  The two notches 2'a and 2'a shown in the figure are provided at positions that divide the magnet piece 2 'into three equal parts. By cleaving the magnet piece 2' using the notch 2'a as a starting point, In the magnet piece 2 ', a cleaving line is formed by reason, and the cleaving line facing the side surface 2'b having no notch is generally not divided into three equal parts as shown in FIG. Three cleaved magnets 2a, 2b, and 2c that are cleaved differently at s2 and s3 and have different overall dimensions and shapes are manufactured.

  FIG. 4 shows a state in which the three cleaving magnets 2a, 2b, and 2c are disposed in the magnet slot 1b.

  As can be seen from the figure, the cleaved magnet 2b formed in a substantially trapezoidal shape in plan view has a wide side width of s2 with no notch, but is substantially triangular in the vicinity of the break point of the magnet slot 1b. Since this has the insulating region R, this becomes a buffer region that accommodates the width s2. That is, even in a cleaving magnet whose shape and dimensions are often formed, the cleaving magnet can be smoothly arranged by applying the magnet slot 1b having the illustrated shape.

[Magnetic field analysis and results]
When the inventors applied the rotor structure of the present invention by modeling the rotor structure of the present invention (Examples 1, 2 and 3) and the conventional rotor structure (comparative example) in a computer and performing magnetic field analysis The effect of reducing the loss (vortex loss) of the split magnet was confirmed.

Here, the rotor model is a rotor model in which two magnet slots are opened in a substantially V shape and three divided magnets are arranged in each magnet slot to form one pole, and a predetermined number of them are provided. It is. As analysis conditions, a current of ± 106.07 A was applied at a rotational speed of the rotor of 10,000 rpm and 833.33 Hz. In addition, the electric resistance of the divided magnet is 1.35 × 10 ⁻⁶ Ωm, the electric contact resistance between the divided magnets is 1.91 × 10 ⁻⁵ Ωm, the electric resistance of the insulating resin is 5.34 × 10 ⁻² Ωm, A magnetic field having a frequency of 2500 Hz and a magnetic flux density of ± 0.073 T was applied to the split magnet. The analysis result is shown in FIG.

  In FIG. 5, the comparative example has an angle θ of 0 degree, the angle θ of Example 1 is 9 degrees, the angle θ of Example 2 is 18 degrees, and the angle θ of Example 3 is 27 degrees. In the comparative example model, the divided magnets are in close contact with each other over the entire divided surface. The loss density when the divided magnets are completely insulated is 350 W / kg.

  From the graph, the maximum loss density of the comparative example is 1983 W / kg, whereas the maximum loss density of Example 1 is 456 W / kg, Example 2 is 407 W / kg, and Example 3 is 352 W / kg. It has been demonstrated that an extremely large loss reduction effect can be obtained at an angle of 9 degrees or more with the angle of 9 degrees of Example 1 as an inflection point. Incidentally, the loss of Example 1 is reduced to about 23% of the comparative example.

  From this analysis result, by adjusting the angle between the divided magnets in the magnet slot shown in FIG. 2 to 9 degrees or more, a very high vortex loss reduction effect is achieved in the divided magnet, and this rotor is provided. By using an IPM motor, its torque performance and rotational performance can be greatly improved.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. They are also included in the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Rotor, 1a ... Rotor side surface, 1b ... Magnet slot, 1c ... Rotor shaft (rotor center), 2 ... Split magnet, 2a, 2b, 2c ... Cleaving magnet, 2 '... Magnet piece before cleaving, 2'a ... notch, 2'b ... side surface without notch, 3 ... insulating resin, 4 ... stator, 5 ... coil

Claims (4)

In the rotor, two magnet slots are formed in a substantially V-shape, and magnets are arranged in each magnet slot to form one pole, which is formed at intervals in the circumferential direction of the rotor. A rotor for a motor,
The magnet slot has a substantially curved shape convex toward the rotor center in plan view, a plurality of divided magnets are disposed in the magnet slot, and the adjacent divided magnets are only one point on the rotor side surface in plan view. The rotor for an IPM motor in which the angle between the two divided magnets is adjusted to 9 degrees or more around the one point where the adjacent divided magnets are in contact with each other .   The rotor for an IPM motor according to claim 1, wherein the plurality of divided magnets are cleaved magnets obtained by cleaving one magnet. The rotor for an IPM motor according to claim 1 or 2 , wherein a height of the divided magnet in the rotor axial direction is longer than a width of the divided magnet in the circumferential direction of the rotor. IPM motor consisting of a rotor according to any one of claims 1 to 3, a stator disposed around the rotor.

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