JP2009232525A - Rotor for ipm motor and ipm motor - Google Patents

Abstract

A rotor for an IPM motor having a structure capable of effectively suppressing thermal demagnetization even when thermal demagnetization caused by a reversal magnetic field that can occur in a permanent magnet is provided. An IPM motor is provided.
A plurality of permanent magnets 2 are accommodated in slots 13 of a rotor core 10, and a resin material 3 for fixing the permanent magnets is interposed between at least a part of the side surfaces of the permanent magnets 2 and the inner surface of the slots 13. In the rotor 1 for an IPM motor, a connecting portion 4 made of a magnetic material is formed in the resin material 3 so as to communicate with the side surface of the permanent magnet 2 and the inner surface of the slot 13.
[Selection] Figure 2

Description

  The present invention relates to an IPM motor rotor in which a permanent magnet is embedded in a rotor, and an IPM motor including the rotor.

  A magnet-embedded motor (hereinafter referred to as an IPM motor) in which a permanent magnet is embedded in a rotor can obtain a reluctance torque in addition to a magnet torque caused by the attractive force / repulsive force of a coil and a permanent magnet. Compared with a surface magnet type motor in which a magnet is attached to the outer peripheral surface of a rotor, it has high torque and high efficiency. Therefore, this IPM motor is used for a drive motor of a hybrid vehicle, an electric vehicle and the like that require high output performance. In addition, as this permanent magnet, it consists of sintered magnets, such as a rare earth magnet, a ferrite magnet, and an alnico magnet.

  By the way, when the permanent magnet is exposed to a high temperature and a high reverse magnetic field, the magnetization direction is reversed and demagnetized, and the reversal magnetic field (reversal magnetic flux) due to this demagnetization further promotes the progress of demagnetization. It is well known that it becomes a factor to do. Therefore, the conventional permanent magnet is designed so that the magnet does not demagnetize even when a magnetic field at the maximum torque is applied to the magnet.

  In the IPM motor, the permanent magnet is fixed in the slot for inserting the permanent magnet formed in the rotor core. Therefore, as in the rotor for the IPM motor disclosed in Patent Document 1, for example, the resin of the nonmagnetic material is made permanent with the slot. Filled and hardened in the gaps between the magnets. If the demagnetization (thermal demagnetization) described above occurs in the permanent magnet in this state, the reversal magnetic field tries to pass through the portion having the lowest magnetic resistance, and therefore passes through the interior of the permanent magnet, not the cured resin material. This promotes the progress of magnet demagnetization.

JP 2007-236020 A

  The present invention has been made in view of the above-described problems, and relates to a rotor for an IPM motor. Even when thermal demagnetization due to a reversal magnetic field that can occur in a permanent magnet occurs, this thermal demagnetization is effective. An object of the present invention is to provide a rotor for an IPM motor having a structure that can be suppressed to a low level, and an IPM motor including the same.

  In order to achieve the above object, in the rotor for an IPM motor according to the present invention, a plurality of permanent magnets are accommodated in a slot of a rotor core, and the permanent magnet is fixed between at least a part of the side surface of the permanent magnet and the inner surface of the slot. A rotor for an IPM motor in which a resin material for use is interposed, which is in communication with a side surface of the permanent magnet and an inner surface of the slot, and a connecting portion made of a magnetic material is formed in the resin material. It is what.

  The rotor for an IPM motor of the present invention assumes that the permanent magnet embedded in the rotor core is thermally demagnetized during the period of use of the motor, and this demagnetization is performed even if thermal demagnetization occurs in the permanent magnet. This is related to an IPM motor rotor that can effectively suppress the initial magnetic force (magnetic characteristics) of a permanent magnet or a magnetic force close to it over the period of use. That is, as described above, the conventional rotor for an IPM motor assumes a case where thermal demagnetization occurs in the permanent magnet, and exhibits a structure in which the magnetic characteristics of the permanent magnet are not reduced as much as possible even by thermal demagnetization. In that respect, the rotor for an IPM motor of the present invention can be said to be a novel technical idea (structure).

  As a configuration for that purpose, in the slot for the permanent magnet formed in the rotor core, a connecting portion is formed between the side surface of the permanent magnet and the inner surface of the slot to flow an inversion magnetic field that causes thermal demagnetization. It is embedded in a non-magnetic resin material.

  In the slot, after inserting the permanent magnet into the slot, a non-magnetic resin for fixing the permanent magnet in the slot is filled and cured to form a resin material, and the permanent magnet is fixed by this resin material. However, the connecting portion is made of a soft magnetic material and is disposed so as to connect the side surface of the permanent magnet and the inner surface of the slot of the rotor core.

  Here, it is desirable that the connecting portion is formed outside the magnetic flux saturation region in the resin material described above. According to the inventors of the present invention, it has been specified that the magnetic flux saturation region is formed in a region on the stator side of the resin material on the side of the permanent magnet. However, it has been specified that it is difficult to effectively escape the reversal magnetic field acting on the permanent magnet to the side resin material.

  The rotor core may be formed from a powder magnetic core formed by press-molding soft magnetic metal powder. For example, the rotor core may be formed from a steel sheet laminate formed by laminating steel sheets such as electromagnetic steel sheets. When the rotor core is formed from the laminated body, the connecting portion described above may be integrally formed from the same steel plate that forms the rotor core, and may be a protrusion that protrudes into the slot.

  In this embodiment, the laminated steel plates are punched into a disk shape for the rotor core, and when the number of permanent magnet slots corresponding to the number of poles is punched in the inside, the projecting material protruding inside the slots is provided. By processing the slot so as to form, a rotor core in which a projecting material protrudes into the slot when a predetermined number of steel plates are laminated can be manufactured.

  By inserting the permanent magnet into the slot, the projecting material comes into contact with the side surface of the permanent magnet, and the rotor for the IPM motor is formed by filling and curing the nonmagnetic resin in the slot in this posture.

  According to the rotor for an IPM motor described above, even if thermal demagnetization occurs in the permanent magnet during the motor use period, the reversal magnetic field (flow) that causes this is transmitted via the magnetic material connecting portion to the rotor core. It is possible to escape to the side, and the amount of demagnetization in the permanent magnet can be reduced.

  In another embodiment of the rotor for an IPM motor according to the present invention, a plurality of permanent magnets are accommodated in slots of the rotor core, and the permanent magnets are disposed between at least a part of the side surfaces of the permanent magnets and the inner surface of the slots. A rotor for an IPM motor in which a fixing resin material is interposed, wherein a demagnetization reference point formed from the stator side of the permanent magnet is defined as P point, and the point opposite to the stator of the permanent magnet from P point L1 is the distance to the end region, R1 is the magnetic resistivity of the permanent magnet, L2 is the distance from the point P to the end of the resin material on the rotor core side, and L2 When the magnetic resistivity of the material is R2, L2 × R2 has a combination of a resin material and a shape of the resin material that are smaller than L1 × R1.

  In the present embodiment, the resin may be filled and cured in the slot, or a resin material having a predetermined shape may be formed in advance, and the resin material may be inserted into the slot. Good.

  If it is assumed that thermal demagnetization occurs in the permanent magnet, if a reversal magnetic field acts on the permanent magnet, demagnetization occurs from the stator side of the permanent magnet.

  When a certain point of the permanent magnet is used as a demagnetization reference point, whether a reversal magnetic field flows from the reference point to the rotor core from the end region on the opposite side of the stator through the permanent magnet, or this reference point Whether the reversal magnetic field flows from the base to the side of the permanent magnet and flows through the resin material to the rotor core is the magnitude of the magnetoresistance of both routes from this reference point, that is, the reversal magnetic field is difficult to flow (or easy flow) )).

  Therefore, by increasing the magnetic resistance of the route through which the reversal magnetic field flows in the permanent magnet from the reference point as compared to the route through the resin material, the reversal magnetic field can be easily released from the reference point to the resin material side. The demagnetization in the permanent magnet is suppressed as much as possible.

  The value of the magnetic resistance is multiplied by the magnetic resistivity in both routes, that is, the magnetic resistivity of the permanent magnet and the magnetic low efficiency of the resin material, and the distance through which the reversed magnetic field flows from the reference point in both routes. Find the combined value, and set the combination of the resin material (specific magnetic low efficiency) and the shape (the route length changes depending on the shape) so that the value of the route through which the reversed magnetic field flows in the permanent magnet becomes small That's fine.

  As the material of the resin material, it is possible to use a resin material having high strength and high heat resistance, and further having high thermal conductivity. For example, epoxy resin, phenol resin, and alumina or Examples include materials mixed with fillers such as silica. The resin material has a smooth shape composed of a convex portion projecting from the side of the permanent magnet toward the rotor core and a concave portion entering into the permanent magnet side. The concave portion is reversed from the reference point of demagnetization described above. As a result, the distance that the reversal magnetic field flows from the reference point can be shortened, so that the product of this distance and the magnetic resistivity of the resin material can be reduced.

  The motor including the rotor for an IPM motor according to the present invention described above has a rotor core on the outer side of the permanent magnet that effectively causes the reversal magnetic field that causes this even if thermal demagnetization that has not been assumed in the past occurs in the permanent magnet. Thus, demagnetization in the permanent magnet can be minimized. Therefore, a motor equipped with this rotor for an IPM motor is suitable for a hybrid vehicle or an electric vehicle, which has been actively produced recently and has been sought to mount a drive motor with excellent performance.

  As can be understood from the above description, the IPM motor rotor of the present invention can suppress the amount of demagnetization to a minimum even if thermal demagnetization occurs in the permanent magnet.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view of a rotor for an IPM motor, and FIG. 2 is an enlarged view of a portion II in FIG. 1, and is a plan view showing an embodiment of a permanent magnet and a resin material in a slot.

  The illustrated rotor 1 for an IPM motor is obtained by inserting and fixing a permanent magnet 2 in a slot 13 formed in a steel sheet laminated body in which electromagnetic steel sheets are laminated or a rotor core 10 made of a dust core. More specifically, the planar view is rectangular in each of the slots 13 and 13 that are formed in a substantially V shape (two rectangles are substantially spaced apart from each other) in plan view per pole. Permanent magnets 2 and 2 are arranged to form a V-shaped permanent magnet, which has a predetermined number of poles extending in the circumferential direction.

  A shaft opening 12 is formed at the center of the rotor 1 and is formed by a plurality of teeth protruding radially inward from a hollow portion in a stator core (not shown), that is, a substantially annular yoke in plan view. In the hollow portion, the illustrated rotor 1 is disposed in a posture in which a predetermined gap is formed between the tip of the teeth and the stator side surface 11 of the rotor core 10 to form an IPM motor.

  The rotor core 10 is provided with a slot 13 having a planar shape that conforms to the planar shape of the permanent magnet 2 shown in FIG. 2 and the resin materials 3 and 3 provided on the side thereof. The magnetized permanent magnet 2 is inserted into the slot 13 and the resin is filled and cured on the side thereof, whereby the resin material 3 is formed and the permanent magnet 2 is fixed in the slot.

  In FIG. 2, a connecting portion 4 made of a magnetic material is interposed between the permanent magnet 2 and the inner surface of the slot 13, and a reversal magnetic field indicated by an arrow Y flows through the connecting portion 4, and the outer periphery of the slot 13. This reversal magnetic field escapes to the rotor core 10. Note that the point at which this reversal magnetic field escapes to the connecting portion 4 in the permanent magnet 2 is defined as a reference point P1.

  The arrangement position of the connecting portion 4 in the slot 13, more specifically, the position of the reference point P <b> 1 is provided outside the saturation magnetic flux region indicated by the A region in the drawing, so that Thermal demagnetization can be effectively suppressed.

  When the rotor core 10 is made of a steel plate laminate formed by laminating electromagnetic steel plates, the connecting portion 4 is preferably made of an electromagnetic steel plate in the same manner as the rotor core 10. When the electromagnetic steel sheet is punched, the connecting part 4 is formed so as to protrude into the slot, and the connecting part 4 made of the electromagnetic steel sheet extending in the height direction of the slot is efficiently formed by laminating this. It is because it can form.

  On the other hand, FIG. 3 is a plan view showing another embodiment of the permanent magnet and the resin material in the slot.

  In this embodiment, the resin material 3A has a shape including two convex portions 3a and 3c projecting from the side surface of the permanent magnet 2 toward the rotor core side, and a concave portion 3b formed therebetween, and is shown in FIG. It does not require a form of communication section.

  In the figure, when a demagnetization occurs in the permanent magnet 2 due to a reversal magnetic field, and an arbitrary point where the heat demagnetization has progressed is defined as the reference point P2, the reversal magnetic field passes through the resin material 3A from the reference point P2. A reversal magnetic field route Y2 escaping to the rotor core 10 side passes through the recess 3b.

  Here, the distance in the resin material 3 from the reference point P2 through the route Y2 to the rotor core 10 is L2, and the end portion of the reference material P2 passes through the permanent magnet 2 without passing through the route Y2. The distance to the rotor core 10 in the route Y3 flowing through the rotor core 10 via L1 is L1. Here, the end portion of the permanent magnet 2 through which the route Y3 passes is meant to include the end side or side surface of the permanent magnet 2 opposite to the stator.

  When the magnetic resistivity of the resin material 3A is R2 and that of the permanent magnet 2 is R1, the material of the resin material and its shape (here, the value of R2 × L2 is smaller than the value of R1 × L1) By setting the illustrated shape forming the distance L2, the reversal magnetic field from the reference point P2 is released to the rotor core 10 through the route Y2 that is easy to flow, and the demagnetization that has progressed to the reference point P2 Progressing beyond the point P2 in the permanent magnet 2 (on the shaft side) is suppressed. Also in the figure, the route Y2 is adjusted so as to be formed outside the saturation magnetic flux region A in the resin material 3A.

  The reference point P2 described above changes depending on the degree of progress of demagnetization. Therefore, the reference point P2 is set to an arbitrary point obtained by analysis or the like, and L2 from the reference point P2 is minimum. The shape of the resin material 3A can be set as follows. In setting the shape, the magnetic characteristics (magnetic resistivity) of both the resin material and the permanent magnet are also taken into consideration, and the resin material 3A has a relatively small magnetic resistance of the route Y2 at the product value described above. Shape setting is performed.

[Analysis and results of magnet demagnetization with changing temperature conditions]
The inventors have modeled an IPM motor having a rotor having a reversal magnetic field escape structure shown in FIG. 2 and applied a magnetic field at the maximum torque for each temperature condition while changing the temperature condition. The reduction rate of motor no-load induced voltage was compared.

  The created model includes a conventional motor (comparative example) having a rotor without a magnetic flux escape structure, a motor (Example 1) having a rotor in which the reference point P of the magnetic flux escape structure is provided on the stator side, and These are three models of a motor (Example 2) having a rotor in which the reference point P of the magnetic flux release structure is provided at substantially the center of the magnet.

  FIG. 4A is a diagram for explaining the magnetic flux escape structure on the magnet side surface in the first embodiment, and FIG. 4B is a diagram for explaining the magnetic flux escape structure on the magnet side surface in the second embodiment.

  Regarding the first embodiment shown in FIG. 4a, the permanent magnet model M1 has a resin material model M2 on the left side, and the position of the reference point P1a is provided at a position on the stator side of 35% of the magnet thickness. The resin material model M3 is provided, and the position of the reference point P1b is provided at a position on the 1/4 stator side of the magnet thickness.

  On the other hand, with respect to Example 2 shown in FIG. 4b, the permanent magnet model M1 has a resin material model M4 on the left side, and the position of the reference point P1c is provided at the position on the rotor center side of 40% of the magnet thickness (magnet The resin material model M5 is further provided on the right side, and the position of the reference point P1d is provided at the center position of the magnet thickness.

  The analysis results are shown in FIG. 5, in which the graph Z1 shows the results of the comparative example, the graph Z2 shows the results of the example 1, and the graph Z3 shows the results of the example 2. In this analysis, the motor no-load induced voltage is measured under a certain reference temperature: Ta temperature condition. The temperature condition is Ta + 40 ° C. higher by ΔT (= 40 ° C.) than this reference temperature, and further 60 ° C. higher than the reference temperature. The motor no-load induced voltage was measured under the temperature condition of Ta + 60 ° C., and the rate of decrease with respect to the voltage at the reference temperature: Ta was calculated.

  From the figure, under the temperature condition of Ta + 60 ° C., the demagnetization is about 32% in the comparative example, whereas the demagnetization is about 21% in the first embodiment and about 17% in the second embodiment. It has been demonstrated that the effect of the magnetic flux escape structure can be sufficiently obtained.

  Further, comparing Examples 1 and 2, under the temperature condition of Ta + 40 ° C., Example 1 has a demagnetization factor of about 2%, and Example 2 has a demagnetization factor of about 4%. It can be seen that the effect of suppressing demagnetization is excellent. This indicates that it is preferable to position the reference point in place according to the set temperature condition.

  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.

It is a top view of the rotor for IPM motors. FIG. 2 is an enlarged view of a portion II in FIG. 1 and is a plan view showing an embodiment of a permanent magnet and a resin material in a slot. It is the top view which showed other embodiment of the permanent magnet and resin material in a slot. FIG. 7 is a diagram illustrating a magnetic flux escape structure on the side surface of a magnet in a motor rotor used in an analysis relating to a magnet demagnetization factor when a temperature condition is changed, and (a) shows the structure of Example 1. (B) is the figure which showed the structure of Example 2. FIG. It is a graph which shows an analysis result.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Rotor, 10 ... Rotor core, 11 ... Stator side surface, 12 ... Shaft opening, 13 ... Slot, 2 ... Permanent magnet, 3, 3A ... Resin material, 3a, 3c ... Convex part, 3b ... Concave part, 4 ... Contact P, demagnetization reference point

Claims (4)

A rotor for an IPM motor, wherein a plurality of permanent magnets are accommodated in a slot of a rotor core, and a resin material for fixing the permanent magnet is interposed between at least a part of the side surface of the permanent magnet and the inner surface of the slot. ,
A rotor for an IPM motor, characterized in that a connecting portion made of a magnetic material is formed in the resin material so as to communicate with a side surface of the permanent magnet and an inner surface of the slot.   2. The rotor for an IPM motor according to claim 1, wherein the rotor core is made of a steel plate laminate formed by laminating steel plates, and the connecting portion is a protrusion formed from the steel plate and protruding into the slot. A rotor for an IPM motor, wherein a plurality of permanent magnets are accommodated in a slot of a rotor core, and a resin material for fixing the permanent magnet is interposed between at least a part of the side surface of the permanent magnet and the inner surface of the slot. ,
The demagnetization reference point formed from the stator side of the permanent magnet is P point, the distance from the P point to the end region of the permanent magnet opposite to the stator is L1, and the magnetic resistance of the permanent magnet is R1. When the distance from the point P through the resin material on the side of the permanent magnet to the end of the resin material on the rotor core side is L2, and the magnetic resistivity of the resin material is R2, L2 × R2 is L1 A rotor for an IPM motor having a combination of a resin material smaller than R1 and the shape of the resin material.   An IPM motor comprising the rotor according to claim 1.

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