JP2013219847A - Rotor of rotary electric machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotor of a rotary electric machine that can suppress demagnetization of a permanent magnet for a magnetic gap while reducing the consumption of a heavy rare-earth element.SOLUTION: A permanent magnet 31 includes a high holding power portion 33 which has higher holding force at a corner portion than any other portions. In each magnet insertion hole 25, two permanent magnets 31, 31 are arranged abutting against each other. The two permanent magnets 31, 31 arranged in the magnet insertion hole 25 have an abutting surface 35 arranged opposite a magnetic gap formed by a swollen portion 29.

Description

  The present invention relates to a rotor of a rotating electrical machine provided with a permanent magnet.

  Conventionally, an IPM motor in which a permanent magnet is embedded in a rotor of a rotating electrical machine is known. If a demagnetizing field is applied to the permanent magnet during use of this rotating electric machine, the permanent magnet will be demagnetized and the magnetic force will be reduced. It is planned. However, since the coercive force and the magnetic flux density are in a trade-off relationship, when a heavy rare earth element is contained in the entire magnet, the coercive force is increased while the magnetic flux density is decreased, resulting in a decrease in output torque. . In addition, in this case, since the heavy rare earth element is expensive, the manufacturing cost increases.

  On the other hand, in the rotating electrical machine described in Patent Document 1, heavy rare earth elements are applied to a part of the surface of the permanent magnet that faces the stator, and the holding force is reduced from the surface toward the inside. A structure that has an optimal distribution of holding force is proposed.

  By the way, in the IPM motor, in order to fix the permanent magnet arranged in the magnet insertion hole, a bulging part is formed so that a part of the periphery of the magnet insertion hole swells, and the bulging part is used as an inlet for the filler. A technique is also known in which a permanent magnet is fixed in a magnet insertion hole by injecting a filler such as resin from a bulging portion.

JP 2012-4147 A

  However, in an IPM motor in which a bulging portion is formed in the magnet insertion hole, the bulging portion becomes a magnetic gap, and the magnetic resistance increases against a demagnetizing field that acts substantially perpendicularly to the permanent magnet. At a location facing the magnetic gap, the permeance represented by the reciprocal of the magnetic resistance is reduced. That is, as shown in FIG. 6, the bulging portion 129 becomes a magnetic gap with respect to a demagnetizing field (arrow in the figure) acting substantially perpendicular to the permanent magnet 131, and the permanent magnet 131 in the figure At a location X facing the magnetic gap indicated by the hatched portion, the permeance represented by the reciprocal of the magnetic resistance is reduced.

FIG. 7 is a graph showing a demagnetization curve and a permeance line of a permanent magnet, where the vertical axis represents magnetic flux density (B (T)) and the horizontal axis represents coercive force (-H (A / m)).
The operating point of the permanent magnet is determined by the intersection of the demagnetization curve and the permeance line. When a current is applied to the stator, a demagnetizing field acts on the permanent magnet, and the permeance line moves in the negative direction as shown by arrow A. Approach the inflection point. At this time, in the portion where the permeance of the permanent magnet is small, the permeance line is inclined in the direction indicated by the arrow B so that the inclination of the permeance line (permeance coefficient) is twisted. For example, when a current is applied at temperature T1, the bending point does not exceed the bending point at the point B1 where the permeance is large, reaches the bending point at the point B2 where the permeance is medium, and the magnetic flux density exceeds the bending point at the point B3 where the permeance is small. It is getting smaller rapidly. In this way, when the magnetic flux density once decreases beyond the bending point in a part of the permanent magnet, the magnetic flux density of the permanent magnet is lower than the original magnetic flux density even when the demagnetizing field action is lost. End up. That is, the permanent magnet is demagnetized.

  On the other hand, since the demagnetization curve of the high coercive force portion shown in FIG. 7 has a large coercive force, demagnetization does not occur at the point B3 ′ where the permeance is small and does not exceed the bending point. If the rare earth element is contained in the whole magnet, the manufacturing cost increases.

  Therefore, it is important to reduce the demagnetization at a location where the permeance of the permanent magnet is low while reducing the content of the heavy rare earth element in order to generate a large torque in the rotating electrical machine.

  In the rotating electrical machine described in Patent Document 1, when the bulging portion is formed at a part of the periphery of the magnet insertion hole, the bulging portion becomes a magnetic gap, and the permeance decreases at a position facing the magnetic gap of the permanent magnet. There is a risk of demagnetization.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a rotor for a rotating electrical machine that can suppress demagnetization of a permanent magnet with respect to a magnetic gap while reducing the amount of heavy rare earth elements used. Is to provide.

In order to achieve the above object, the invention according to claim 1
A rotor core (for example, a rotor core 21 in an embodiment described later);
A plurality of magnet insertion holes (for example, a magnet insertion hole 25 in an embodiment described later) formed in the rotor core;
A rotor (for example, a later-described embodiment) of a rotating electrical machine (for example, a rotating electrical machine 10 in a later-described embodiment) provided with a permanent magnet (for example, a permanent magnet 31 in a later-described embodiment) inserted into the magnet insertion hole. Rotor 20) of
The permanent magnet has a high holding force portion (for example, a high holding force portion 33 in an embodiment described later) having a higher holding force than the other portions at the corners,
In each of the magnet insertion holes, a plurality of the permanent magnets are arranged in contact with each other,
A bulging portion (for example, in an embodiment described later) is formed on a part of the outer peripheral side wall portion or the inner peripheral side wall portion of each magnet insertion hole so that a part of the peripheral edge of the magnet insertion hole bulges when viewed from the axial direction. A bulging portion 29) is formed, and a magnetic gap is formed by the bulging portion between the magnet insertion hole and the plurality of permanent magnets disposed in the magnet insertion hole;
In the plurality of permanent magnets arranged in the magnet insertion holes, contact surfaces of the plurality of permanent magnets (for example, contact surfaces 35 in the embodiments described later) are disposed at locations facing the magnetic gap. It is characterized by that.

In addition to the configuration of claim 1, the invention according to claim 2
The bulging portion is formed at a substantially center in the circumferential direction of the magnet insertion hole.

In addition to the configuration of claim 1 or 2, the invention according to claim 3
The bulging portion is an injection port for injecting a filler.

In addition to the structure of any one of Claims 1-3, the invention which concerns on Claim 4
The plurality of permanent magnets arranged in the magnet insertion hole are provided with the high holding force portion on the contact surface.

In addition to the structure of any one of Claims 1-4, the invention which concerns on Claim 5 is
The circumferential width (for example, width L1 of the embodiment described later) of the high holding force portion of the plurality of permanent magnets arranged in the magnet insertion hole is the circumferential width of the bulging portion ( For example, it is characterized by being wider than a width L2) of an embodiment described later.

In addition to the structure of any one of Claims 1-5, the invention which concerns on Claim 6 is
The high holding force portion is formed by vacuum vapor deposition of a heavy rare earth element.

According to the first aspect of the present invention, as compared with a permanent magnet in which heavy rare earth elements are uniformly dispersed throughout the magnet as in the prior art, a decrease in magnetic flux density is suppressed by adding heavy rare earth elements at corners. The holding power can be increased while the manufacturing cost can be reduced.
In addition, when a magnetic gap is formed between the magnet insertion hole and the permanent magnet by the bulging portion formed at a part of the periphery of the magnet insertion hole, the magnetic gap is formed at a location facing the magnetic gap of the permanent magnet. Resistance increases and permeance decreases. In places where the permeance is small, demagnetization tends to occur. However, the contact surfaces of a plurality of permanent magnets having high holding force portions at the corners are arranged opposite to the magnetic gap, so that the permanent magnets The demagnetization at the location facing the magnetic gap can be suppressed.

  Further, according to the invention of claim 2, since a plurality of permanent magnets can be arranged in the magnet insertion hole using the same shape of permanent magnets, the cost can be reduced as compared with the case of using different shape permanent magnets. Can be reduced. Moreover, since the same-shaped permanent magnet is used, incorrect assembly can be prevented.

  According to the invention of claim 3, the permanent magnet can be pressed and fixed toward the outer peripheral side wall or inner peripheral side wall of the magnet insertion hole, and the permanent magnet can be stably held. In addition, since the permanent magnet can be pressed and fixed toward the outer peripheral side wall portion or the inner peripheral side wall portion of the magnet insertion hole, the permanent magnet can be prevented from being inclined and arranged in the magnet insertion hole. The variation in the magnetic performance of the rotating electrical machine can be suppressed.

  Further, according to the invention of claim 4, since the high holding force portion is provided on the contact surface between the permanent magnets in addition to the corner portion of the permanent magnet, the reduction at the location facing the magnetic gap of the permanent magnet is achieved. Magnetism can be further effectively suppressed.

  According to the invention of claim 5, since the high coercive force portion can be disposed corresponding to the entire circumferential direction of the portion facing the magnetic gap of the permanent magnet, demagnetization is further effectively suppressed. be able to.

  According to the invention of claim 6, it is possible to form a permanent magnet having a high holding force with respect to the amount of heavy rare earth element. Moreover, since the residual magnetic flux density is large in the internal low coercive force portion surrounded by the high coercive force portion, the output torque can be improved.

It is a top view of the rotary electric machine of 1st Embodiment of this invention. It is the elements on larger scale of the rotor of the rotary electric machine shown in FIG. It is a figure explaining the positional relationship of the contact surface and bulging part of two permanent magnets which comprise a permanent magnet body. It is a graph which shows the difference of the demagnetization factor in an Example and Comparative Examples 1 and 2. It is the graph which compared the magnet temperature and the induced voltage reduction | decrease rate in an Example and the comparative example 2. FIG. It is a figure which shows the area | region where permeance becomes small among permanent magnets with respect to a demagnetizing field. It is a graph which shows the demagnetization curve and permeance line of a permanent magnet.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The drawings are viewed in the direction of the reference numerals.
As shown in FIGS. 1 and 2, the rotating electrical machine 10 of the present embodiment is an IPM type rotating electrical machine used as a traction motor of an electric vehicle, for example, and mainly includes a stator 11 and a rotor 20. . The rotor 20 is rotatably disposed inside the stator 11 with a slight gap.

  The stator 11 includes a stator core 13 in which a plurality of slots 14 and teeth 15 are formed on the inner peripheral side of laminated electromagnetic steel sheets, and a multi-phase armature that is accommodated in the slots 14 and generates a rotating magnetic field to rotate the rotor 20. Winding 16 is provided.

  The rotor 20 includes a substantially cylindrical rotor shaft (not shown), a rotor core 21 provided on the outer periphery thereof, and a plurality of magnetic pole portions 23A and 23B located in the rotor core 21. The magnetic pole portions 23A and the magnetic pole portions 23B have different magnetization directions and are alternately arranged in the circumferential direction.

  The rotor core 21 is configured by laminating a plurality of electromagnetic steel plates 27 to 27 in the axial direction. Each electromagnetic steel sheet 27 ... 27 has a substantially annular shape, and a hole 24 is formed at the center thereof. Further, a plurality of pairs of magnet insertion holes 25, 25 are formed in the circumferential direction on the outer periphery of each of the electromagnetic steel plates 27 ... 27, and the pair of magnet insertion holes 25, 25 are the stator facing surfaces of the rotor core 21. It has a substantially V shape spreading toward the outer peripheral surface.

  The pair of magnet insertion holes 25, 25 constitute one magnetic pole portion 23A (23B) together with the permanent magnet body 30 disposed inside, and are partitioned by a center rib 28 having a predetermined width. Each magnet insertion hole 25 is formed so that the bulging portion 29 swells toward the inner peripheral side at the center of the inner peripheral long side. The bulging portion 29 functions as an injection port for injecting a filler such as resin in order to fix the permanent magnet body 30 disposed in each magnet insertion hole 25.

  Here, the permanent magnet body 30 disposed in each magnet insertion hole 25 has a rectangular shape when viewed from the axial direction, and the two permanent magnets 31, 31 having the same shape abut the short sides of each other. Are arranged. Accordingly, one magnetic pole portion 23A (23B) includes a pair of magnet insertion holes 25 and 25 arranged in a V shape, and four permanent magnets 31 and 31 arranged in the pair of magnet insertion holes 25 and 25. 31, 31. Each magnet insertion hole 25 is formed to have a larger width than the permanent magnet body 30 composed of two permanent magnets 31, and the space on one end side and the other end side in the longitudinal direction of the permanent magnet body 30 suppresses short-circuiting of magnetic flux. It functions as a flux barrier.

  Each permanent magnet 31 constituting the permanent magnet body 30 is formed in the sintered magnet body by vacuum-depositing a heavy rare earth element containing at least one of Dy and Tb and diffusing the heavy rare earth element from the surface to the inside, as shown in FIG. As shown, the entire outer peripheral surface is a high holding force portion 33 in which heavy rare earth elements are diffused so as to surround the low holding force portion 32 located at the center. The low holding force portion 32 has a higher residual magnetic flux density than the high holding force portion 33, and the high holding force portion 33 has a higher holding force than the low holding force portion 32.

  The high coercive force portion 33 is not limited to vacuum vapor deposition, and heavy rare earth elements may be formed by coating. However, by vacuum vapor deposition, the manufacturing process can be simplified as compared with coating diffusion. It is possible to have a high holding power with respect to the amount. Further, the high holding force portion 33 does not need to be formed on the entire outer peripheral surface, and may be formed at each corner portion of the abutting surface where at least two permanent magnets abut, and constitutes the permanent magnet body 30. The two permanent magnets 31 and 31 are preferably formed on the contact surface of the two permanent magnets 31 and more preferably on the entire outer peripheral surface.

  The two permanent magnets 31, 31 configured in this way constitute the permanent magnet body 30 and are disposed in one magnet insertion hole 25 so as to have the same magnetization direction. At this time, the contact surfaces 35 of the two permanent magnets 31 and 31 are arranged at positions facing the bulging portion 29. The width L <b> 1 of the high holding force portion 33 of the two permanent magnets 31, 31 arranged at the position facing the bulging portion 29 is wider than the circumferential width L <b> 2 of the bulging portion 29. In this way, the four permanent magnets 31, 31, 31, 31 are arranged in the pair of magnet insertion holes 25, 25 constituting one magnetic pole portion 23A (23B) so as to have the same magnetization direction, and this magnetic pole portion 23A. Four permanent magnets 31, 31, 31, 31 are arranged in a pair of magnet insertion holes 25, 25 constituting the magnetic pole part 23 </ b> B (23 </ b> A) adjacent to (23 </ b> B) so that the magnetization direction is different from that of the magnetic pole part 23 </ b> A. Thus, the magnetic pole portions 23A and 23B are formed to be alternately positioned in the circumferential direction.

  Then, by injecting a filler such as resin from the bulging portion 29 of each magnet insertion hole 25, the two permanent magnets 31, 31 constituting the permanent magnet body 30 are pressed against the outer peripheral side wall portion of the magnet insertion hole 25. To fix the magnet insertion hole 25. At this time, the filler injected into the bulging portion 29 becomes a magnetic gap having a larger magnetic resistance than metal.

  In the present invention, since the contact surfaces 35 of the two permanent magnets 31 and 31 having the high holding force portion 33 formed on the entire outer peripheral surface including the corner portions are disposed at locations facing the magnetic gap, the magnetic gap Even when the permeance is lowered at a position facing the, the operating point becomes difficult to exceed the bending point of the demagnetization curve, and demagnetization is suppressed.

Examples of the present invention will be described below.
As described in the above embodiment, a single magnet insertion hole is provided with two permanent magnets whose entire outer peripheral surface is a high holding force part in which heavy rare earth elements are diffused so as to surround the low holding force part. As an example of the present invention, one permanent magnet not containing a heavy rare earth element is disposed in each magnet insertion hole as Comparative Example 1, and the entire outer peripheral surface contains heavy rare earth elements so as to surround the low holding force portion. A configuration in which one permanent magnet serving as a diffused high coercive force portion was arranged was used as Comparative Example 2, and the usage environment was set to 180 ° C., and the state of demagnetization was observed.

FIG. 4 is a graph showing the demagnetization rate of the example and the comparative examples 1 and 2, and shows that the higher the concentration, the greater the demagnetization.
In FIG. 4, the permanent magnet body arranged in one of a pair of magnet insertion holes formed in a substantially V shape that constitutes one of the adjacent magnetic pole portions is on the left side, and the other of the adjacent magnetic pole portions is on the other side. Two permanent magnet bodies constituting different magnetic pole portions were arranged in a line with the permanent magnet body arranged in the other of the pair of magnet insertion holes formed in a V shape constituting the magnetic pole portions of the magnetic pole portion on the right side. In the center of each magnet insertion hole, a bulging portion serving as a magnetic gap is formed. When this is applied to the above embodiment, the permanent magnet body 30 inserted into the magnet insertion hole 25 constituting the magnetic pole portion 23A shown in FIG. 2 and the permanent magnet body inserted into the magnet insertion hole 25 constituting the magnetic pole portion 23B. 30 in a line.

  As is apparent from FIG. 4, it can be seen that in Comparative Example 1, large demagnetization occurs uniformly from the portion facing the magnetic gap toward the outer peripheral side. This is because the permanent magnet body arranged in each magnet insertion hole is composed of one permanent magnet that does not contain heavy rare earth elements, and demagnetization has occurred over a wide range from the location facing the magnetic gap. It is considered a thing.

  On the other hand, in Comparative Example 2, the area of the large portion of demagnetization is reduced compared with Comparative Example 1 and the demagnetization is improved, but at the location facing the magnetic gap and the central portion of the permanent magnet body. It can be seen that large demagnetization occurs. This is because the permanent magnet body arranged in each magnet insertion hole is composed of one permanent magnet whose entire outer peripheral surface is a high coercive force portion in which heavy rare earth elements are diffused, and therefore, the demagnetization suppressing effect is weak. It is considered that demagnetization occurred at the location facing the magnetic gap and at the low coercive force portion of the permanent magnet.

  On the other hand, in the example of the present invention, demagnetization occurs slightly at the position facing the magnetic gap, but the demagnetization factor is smaller than those in Comparative Examples 1 and 2, and the overall reduction is also achieved. It can be seen that there is almost no magnetism and the demagnetization is greatly improved as compared with Comparative Examples 1 and 2. This is because the contact surfaces of the two permanent magnets, which are high coercive force portions in which the entire outer peripheral surface is diffused with heavy rare earth elements, are arranged at locations facing magnetic gaps where demagnetization is likely to occur. It is thought that demagnetization was suppressed.

FIG. 5 compares the magnet temperature of the example and the comparative example 2 with the induced voltage reduction rate of the rotating electrical machine.
The demagnetization curve described with reference to FIG. 7 has temperature dependence, and changes as indicated by a broken line in FIG. 7 as the temperature increases in order of T1, T2, and T3. Therefore, the higher the temperature of the permanent magnet, the closer the operating point becomes to the bending point, and demagnetization tends to occur.

  As is clear from FIG. 5, in the rotating electrical machine adopting the comparative example 2, the induced voltage decreases after the temperature A1 is exceeded, and further, the induced voltage decreases further after the temperature A2 is exceeded. I understand that. On the other hand, in the rotating electrical machine adopting the embodiment of the present invention, the induced voltage is hardly decreased even when the temperature exceeds A1, and the induced voltage decreases from the point where the temperature exceeds A2 and exceeds the temperature A3. It can be seen that a greater decrease in induced voltage has occurred since then.

  When observing the decrease of the induced voltage between the example of the present invention and the comparative example 2, a large difference is observed in the decrease rate of the induced voltage within the range of the temperature A1 to the temperature A3. In the rotating electrical machine adopting the example of the present invention, It was confirmed that the reduction rate of the induced voltage was greatly improved by suppressing the occurrence of demagnetization. This means that the rotating electrical machine using the embodiment of the present invention can be used even in a higher temperature environment.

  As described above, according to the present invention, compared with a permanent magnet in which heavy rare earth elements are uniformly dispersed throughout the magnet, the addition of heavy rare earth elements at the corners increases the decrease in magnetic flux density. The holding force can be increased, and the manufacturing cost can be further reduced. Further, heavy rare earth elements can be vacuum-deposited to increase the holding power with a small amount of heavy rare earth elements, and the manufacturing process can be simplified.

  Further, the abutting surfaces 35 of the two permanent magnets 31, 31 having the high holding force portion 33 at the corners are arranged so as to face the magnetic gap, thereby facing the magnetic gap of the permanent magnets 31, 31. Demagnetization can be suppressed, and a decrease in induced voltage can be suppressed even when the magnet temperature rises. Further, by injecting a filler such as a resin from the bulging portion 29 serving as a magnetic gap, the permanent magnet body 30 can be pressed and fixed toward the outer peripheral side wall portion of the magnet insertion hole 25, and the permanent magnet 31, 31 can be stably held.

  Further, by making the two permanent magnets 31 and 31 constituting the permanent magnet body 30 the same shape, it is possible to reduce costs and prevent erroneous assembly as compared with the case of using different shape permanent magnets. be able to.

In addition, this invention is not limited to embodiment mentioned above, A deformation | transformation, improvement, etc. are possible suitably.
For example, in the above embodiment, an inner rotor type rotating electrical machine is illustrated, but an outer rotor type rotating electrical machine may be used. In this case, the bulging portion 29 is formed so as to bulge to the outer peripheral side at the center of the outer peripheral long side of each magnet insertion hole 25.
Moreover, in the said embodiment, although the bulging part used as a magnetic space | gap is formed in the center of each magnet insertion hole, you may form in the edge part side of the circumferential direction rather than the center of each magnet insertion hole. . In this case, demagnetization at a location facing the magnetic gap of the permanent magnet can be suppressed by arranging the contact surfaces of the two permanent magnets having different widths facing the magnetic gap.

21 Rotor core 25 Magnet insertion hole 31 Permanent magnet 10 Rotating electrical machine 20 Rotor 33 High holding force part 29 Swelling part 35 Contact surface

Claims (6)

Rotor core,
A plurality of magnet insertion holes formed in the rotor core;
A rotor of a rotating electrical machine comprising a permanent magnet inserted into the magnet insertion hole,
The permanent magnet has a high holding force part having a higher holding force than the other part at the corner part,
In each of the magnet insertion holes, a plurality of the permanent magnets are arranged in contact with each other,
A bulging part is formed in a part of the outer peripheral side wall part or inner peripheral side wall part of each of the magnet insertion holes so that a part of the peripheral edge of the magnet insertion hole swells when viewed from the axial direction. A magnetic gap is formed by the bulging portion between the hole and the plurality of permanent magnets arranged in the magnet insertion hole,
The rotor of a rotating electrical machine, wherein the plurality of permanent magnets arranged in the magnet insertion hole have contact surfaces of the plurality of permanent magnets arranged at locations facing the magnetic gap.   The rotor of a rotating electrical machine according to claim 1, wherein the bulging portion is formed at a substantially center in a circumferential direction of the magnet insertion hole.   The rotor of a rotating electrical machine according to claim 1, wherein the bulging portion is an inlet for injecting a filler.   4. The rotating electrical machine according to claim 1, wherein the plurality of permanent magnets arranged in the magnet insertion hole include the high holding force portion on the contact surface. Rotor.   The circumferential width of the high holding force portion of the plurality of permanent magnets arranged in the magnet insertion hole is wider than the circumferential width of the bulging portion. The rotor of the rotating electrical machine according to any one of 4.   The rotor of a rotating electrical machine according to any one of claims 1 to 5, wherein the high holding force portion is formed by vacuum vapor deposition of a heavy rare earth element.