JP2012004147A - Magnet and rotary machine - Google Patents

Abstract

The present invention provides a magnet and a rotating machine that can solve problems caused by divided magnets as well as have an optimum coercive force distribution (residual magnetic flux density distribution).
A magnet has a surface adjacent to a stator. When the rotating machine 1 functions as a motor, a demagnetizing field is applied to a portion of the surface 34 opposite to the rotation direction R when rotating in the rotation direction R of FIG. When the rotating machine 1 functions as a generator, a demagnetizing field is applied to the rotation direction R side portion of the rotor 21. In these cases, the demagnetizing field exhibits a maximum value at the above portion of the surface 34 of the magnet 31, and decreases as it goes to the inside of the magnet 34. Since a demagnetizing field with such a distribution is applied to the magnet 31, the diffusion region 32 is formed in a part of the surface 34. In the diffusion region 32, heavy rare earth elements such as Dy and Tb diffuse from the surface 34 toward the inside, and the coercive force decreases as the surface moves toward the inside.
[Selection] Figure 2

Description

  The present invention relates to a magnet and a rotating machine containing a heavy rare earth element and having a high coercive force, and more particularly to an improvement in coercive force distribution.

  The magnet is provided, for example, in a slot of a rotor of a rotating machine. If a demagnetizing field is applied to the magnet during use of the rotating machine, the magnet will demagnetize and the magnetic force will decrease, so the magnet can be made to have a high coercive force by containing a heavy rare earth element such as Dy or Tb. Yes. 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.

  Various techniques have been proposed to solve the above problems. For example, a magnet provided in a slot is divided into a plurality of magnet parts (that is, a plurality of magnet parts are formed as separate bodies), and one magnet part has a high coercive force (low residual magnetic flux density) and the other The magnet is configured to have a high residual magnetic flux density (low coercive force) (for example, Patent Documents 1 and 2). In this technique, magnet portions are bonded together and fixed in a slot.

JP 2009-27847 A JP 2009-118687 A

  However, the technique of Patent Document 2 only divides the magnet into a plurality of magnet parts, and does not consider the distribution of the demagnetizing field applied to the magnet when the rotating machine is used. For this reason, it does not have the optimum coercive force distribution (magnetic flux density distribution) in order to achieve the required levels of magnetic flux density and coercive force and to reduce the manufacturing cost. Further, when the divided magnet of the above technique is applied to a rotor of a rotating machine, there is a risk of a decrease in adhesive strength, a decrease in magnetic force, an increase in an air gap, and an increase in an assembly process.

  That is, when the rotor is used, a large centrifugal force due to a high rotation is usually applied and there is a rotational fluctuation, so that stress is applied in the circumferential direction and the radial direction, and there is a possibility that they are separated from each other starting from the bonded portion. Moreover, since nonmagnetic parts, such as an adhesion part, exist inevitably, the space factor of a magnet falls and the whole magnetic force falls. In addition, the non-magnetic part becomes an air gap on the magnetic circuit, which may cause a reduction in output torque. Furthermore, in the manufacture of a rotating machine, the divided magnet is placed in the rotor slot after processing and is fixed by resin, but in this case, a separate magnet processing step is required, and the split magnet is inserted into the slot of the divided magnet. A process for performing the placement with high accuracy is required, and productivity is lowered.

  An object of the present invention is to provide a magnet and a rotating machine that can solve the above-described problems caused by the divided magnets and can have an optimum coercive force distribution (residual magnetic flux density distribution). .

  As a result of examining the demagnetizing field received by the magnet when the rotor rotates, the present inventor obtained knowledge that the demagnetizing field is not uniform, locally large, and otherwise has a small distribution. It has been found that the problem of the conventional magnet can be solved by forming a coercive force distribution in the magnet corresponding to the distribution. This will be described.

  When the rotor rotates in the direction of rotation, a demagnetizing field is applied to at least a portion of the surface of the magnet adjacent to the stator. FIG. 6 shows an example of the coercive force distribution from a part of the surface of the magnet to the inside. The horizontal axis indicates the position in the internal direction with respect to the surface of the magnet. In this case, as shown in FIG. 6, for example, the demagnetizing field decreases from the surface of the magnet toward the inside, and becomes substantially constant from a predetermined position.

  7A and 7B show the relationship between the coercive force of each magnet and the position from the surface. FIG. 7A shows the coercive force distribution of a conventional magnet with a uniformly high coercive force, and FIG. A coercive force distribution of a conventional magnet (divided magnet) to which a coercive magnet part is bonded, (C) is a graph of a coercive force distribution of an example magnet of the present invention. In FIG. 7, a thick line indicates a necessary coercive force, a broken line indicates a demagnetizing force (corresponding to FIG. 6), and a cross-hatched portion indicates an extra coercive force.

  When a conventional magnet having a uniformly high coercive force is used as the rotating machine magnet, the coercive force is larger than the demagnetizing field in all regions as shown in FIG. However, if the demagnetizing field distribution is taken into consideration, the coercive force is appropriate on the surface, but in other regions, the coercive force is larger than necessary. It has been added. When a conventional magnet (divided magnet) is used, as shown in FIG. 7B, the coercive force is an appropriate size on the surface, but the distribution of the demagnetizing field is not taken into consideration, so In the region up to a predetermined position (high coercive force magnet portion), the coercive force is larger than necessary, and extra rare earth elements are added accordingly. Therefore, the present inventor can optimize the coercive force distribution by setting the coercive force corresponding to a demagnetizing field having a locally large distribution as shown in FIG. 7C, for example. As a result, the present invention has been completed.

  In the magnet of the present invention, in a magnet provided in a rotor of a rotating machine, a diffusion region in which heavy rare earth elements are diffused from the surface is formed on at least a part of the surface, and the diffusion region is directed from the surface to the inside. According to the above, the coercive force is reduced.

  The magnet of the present invention can have a coercive force distribution by forming the diffusion region, and such a coercive force distribution can correspond to a demagnetizing field distribution. Specifically, it is possible to form a diffusion region only in a portion where demagnetization resistance is necessary to obtain a high coercive force, and to provide a low coercive force in the other region. Moreover, in this case, in the diffusion region, the coercive force is reduced as it goes from the surface toward the inside, so that a high coercive force can be achieved only in the desired region in the diffusion region, and in this manner, in the other regions, the residual force remains. The magnetic flux density can be improved.

  The magnet of the present invention having such a diffusion region which is an inclined region is different from a conventional divided magnet having a high coercive force magnet portion and a low coercive force magnet portion having different coercive forces (the coercive force changes in a step shape). The required level of coercive force and residual magnetic flux density can be efficiently realized. Therefore, the output torque can be improved efficiently. In addition, since expensive heavy rare earth elements can be reduced, the manufacturing cost can be reduced. In addition, unlike the conventional split magnet, such an effect can be obtained without dividing the magnet into a plurality of parts. Therefore, the problems that have occurred with the conventional split magnet (decrease in adhesive strength, decrease in magnetic force, air) The increase in the gap and the increase in the assembly process can be eliminated.

  Various configurations can be used for the magnet of the present invention. For example, the diffusion region is preferably a ridge line portion that is parallel to the rotation axis of the rotor and is adjacent to the stator of the rotating machine. The diffusion region is preferably an outer peripheral edge adjacent to the stator of the rotating machine. In the diffusion region, it is preferable that the coercive force is higher than in the non-diffusion region other than the diffusion region, and the residual magnetic flux density is higher in the non-diffusion region than in the diffusion region.

  The rotating machine of the present invention includes the magnet of the present invention. In the rotating machine of the present invention, the same effect as the magnet of the present invention can be obtained.

  According to the magnet or rotating machine of the present invention, the required level of coercive force and residual magnetic flux density can be efficiently realized. In addition, it is possible to obtain an effect such as solving problems (decrease in adhesive strength, decrease in magnetic force, increase in air gap, and increase in assembly process) that have occurred in the conventional split magnet.

It is a schematic sectional drawing showing the whole structure of the rotary machine which concerns on one Embodiment of this invention. It is an expanded sectional view showing a part of outer peripheral part of the rotor of the rotary machine of FIG. (A)-(C) are sectional drawings showing the specific example of the diffusion area | region formed in the magnet of FIG. (A)-(C) represent the specific example of the spreading | diffusion area | region formed in the magnet of FIG. 1, (A) is sectional drawing, (B), (C) is a front view. The schematic structure of various magnets is shown, (A) is a conventional magnet having a uniformly high coercive force, (B) is a conventional magnet (split magnet) in which a high coercive force magnet portion and a low coercive force magnet portion are bonded, (C ) Is a perspective view of an example magnet of the present invention. It is a graph which shows an example of coercive force distribution from a part of surface of a magnet to the inside. The relationship between the coercive force of each magnet and the position from the surface is represented, (A) is a coercive force distribution of a conventional magnet having a uniformly high coercive force, and (B) is a high coercive force magnet portion and a low coercive force magnet portion. Is a coercive force distribution of a conventional magnet (split magnet) to which are attached, and (C) is a graph of the coercive force distribution of the magnet of the present invention.

(1) Overall Configuration Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing the overall configuration of a rotating machine 1 according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a part of the outer peripheral portion of the rotor 21 of the rotating machine 1 of FIG. The rotating machine 1 includes a stator 11 and a rotor 21. The stator 11 includes a yoke 12, and a tooth 13 that extends radially outward from the inner peripheral surface is formed on the yoke 12. A coil is wound around the teeth 13.

  The rotor 21 is disposed in the central hole portion 11 </ b> A of the stator 11. The rotor 21 includes a rotor core 22 whose outer peripheral surface faces the inner peripheral surface of the yoke 12. A gap 41 is formed between the inner peripheral surface of the yoke 12 and the outer peripheral surface of the rotor core 22. A slot 23 is formed in the outer peripheral portion of the rotor core 22, and a magnet 31 is provided in the slot 23. The magnet 31 has a surface 34 adjacent to the yoke 12.

  Here, when the rotating machine 1 functions as a motor, a demagnetizing field is applied to at least a part of the surface 34 of the magnet 31 when the rotor 21 rotates in the rotation direction R of FIG. The demagnetizing field is applied to, for example, a portion of the surface 34 of the magnet 31 opposite to the rotation direction R. In this case, for example, the demagnetizing field shows a maximum value on the surface 34 on the opposite side of the rotation direction R of the magnet 31, decreases from there toward the inside of the magnet 34, and becomes substantially constant from a predetermined position. On the other hand, when the rotating machine 1 functions as a generator during regenerative braking, for example, a demagnetizing field is applied to the rotation direction R side portion of the rotor 21, contrary to the mode of functioning as a motor. In this case, for example, the demagnetizing field shows a maximum value on the surface 34 in the rotation direction R side portion of the magnet 31, decreases from there toward the inside of the magnet 34, and becomes substantially constant from a predetermined position.

  Since the demagnetizing field having such a distribution is applied to the magnet 31, the diffusion region 32 is formed in the portion opposite to the rotation direction R and the rotation direction R side portion of the surface 34. In the diffusion region 32, heavy rare earth elements such as Dy and Tb diffuse from the surface 34 toward the inside, and the coercive force decreases (gradually decreases) from the surface 34 toward the inside. The diffusion region 32 has a high coercive force (low residual magnetic flux density). The regions other than the diffusion region 32 are non-diffusion regions 33 in which heavy rare earth elements are not diffused, and the non-diffusion regions 33 have a high residual magnetic flux density (low coercive force). In this case, in the diffusion region 32, the residual magnetic flux density is increased by decreasing the coercive force from the surface 34 toward the inside, and the diffusion region 32 is an inclined region of the coercive force and the residual magnetic flux density. .

(2) Specific Example of Magnet The diffusion region 32 has a configuration shown in FIGS. 3A to 3C are cross-sectional views illustrating specific examples of the diffusion region 32 formed in the magnet 31 of FIG. 4A to 4C show specific examples of the diffusion region 32 formed in the magnet 31 of FIG. 1, FIG. 4A is a sectional view, and FIG. 4B is a diffusion region 32D on the surface 34 of FIG. (C) is a figure of another example of the shape of diffusion region 32D in surface 34 of (A). 3A to 4A are cross-sectional views in the direction perpendicular to the rotation axis of the rotor 21. FIG. 4B and 4C are front views of the surface 34. FIG.

  The diffusion region 32A of the magnet 31 shown in FIG. 3A is formed in the ridge line portion C1 opposite to the rotation direction R and the ridge line portion C2 on the rotation direction R side in the surface 34, and the other regions are non-diffusion regions 33A. It is. The diffusion region 32B of the magnet 31 shown in FIG. 3 (B) is formed on the entire end on the opposite side of the rotation direction R and the rotation direction R side, and the other region is a non-diffusion region 33B. The diffusion region 32C of the magnet 31 shown in FIG. 3C is formed from the ridge line portion C1 opposite to the rotation direction R on the surface 34 to the substantially central portion, and from the ridge line portion C2 on the rotation direction R side to the substantially central portion. The other region formed is a non-diffusion region 33C. The diffusion regions 32 </ b> A to 32 </ b> C extend in a direction parallel to the rotation axis of the rotor 21 (a direction perpendicular to the paper surface of FIG. 3).

  The diffusion region 32D of the magnet 31 shown in FIG. 4A is formed from the corner on the surface 34 opposite to the rotation direction R to the corner on the rotation direction R side, and the other region is a non-diffusion region 33D. In this case, the diffusion region 32D may be formed on the entire surface 34 as shown in FIG. 4B, or formed on the outer peripheral edge of the surface 34 as shown in FIG. May be.

  In the present embodiment, the aspect in which the rotating machine 1 functions as a motor and a generator is used, but an aspect in which the rotating machine 1 functions as either a motor or a generator may be used. Specifically, in the mode of functioning as a motor, diffusion regions 32A to 32C are formed only on the opposite side in the rotation direction R in the magnet 31 shown in FIGS. In an aspect that functions as a generator, in the magnet 31 shown in FIGS. 3A to 3C, the diffusion regions 32A to 32C are formed only on the rotation direction R side.

(3) Magnet Manufacturing Method A method for manufacturing the magnet 31 will be described. For example, Dy is attached as a heavy rare earth element only to a necessary portion of the surface of the magnet 31, and the magnet 31 is heated to diffuse the heavy rare earth element from the magnet surface to the inside along the grain boundary.

  As described above, in the present embodiment, it is possible to have a coercive force distribution by forming the diffusion region 32 in the magnet 31, and it is possible to make such a coercive force distribution correspond to the demagnetizing field distribution. Specifically, the diffusion region 32 can be formed only in a portion where the demagnetization proof strength is required to have a high coercive force, and the other non-diffusion region 33 can have a low coercive force. In addition, in this case, in the diffusion region 32, the coercive force is decreased from the surface 34 toward the inside, so that a higher coercive force can be achieved only in a desired region in the diffusion region 32, and in other regions. The residual magnetic flux density can be improved.

  The magnet 31 having the diffusion region 32 which is such an inclined region has a high coercive force magnet portion and a low coercive force magnet portion having different coercive forces (different from the conventional divided magnet in which the coercive force changes in a step shape), The required level of coercive force and residual magnetic flux density can be efficiently realized. Therefore, the output torque can be improved efficiently. In addition, since the amount of heavy rare earth elements can be reduced, the manufacturing cost can be reduced. In addition, unlike the conventional split magnet, such an effect can be obtained without dividing the magnet into a plurality of parts. Therefore, the problems that have occurred with the conventional split magnet (decrease in adhesive strength, decrease in magnetic force, air) The increase in the gap and the increase in the assembly process can be eliminated.

  A reduction in the amount of Dy used as a heavy rare earth element, improvement in coercive force, and reduction in residual magnetic flux density will be described using specific examples. 5A and 5B show schematic configurations of various magnets, in which FIG. 5A is a conventional magnet 101 with a uniformly high coercive force, and FIG. 5B is a conventional magnet in which a high coercivity magnet portion 102A and a low coercivity magnet portion 102B are bonded. 102 (divided magnet) and (C) are perspective views of the magnet 103 of the present invention having the diffusion region 103A and the non-diffusion region 103B. The numerical value in the figure is the ratio of each part or each region of the magnets 102 and 103 to the conventional magnet 101 in the longitudinal direction when the length in the longitudinal direction of the conventional magnet 101 is set as a reference (= 1).

  The conventional magnet 101 having a uniformly high coercive force is a magnet having a residual magnetic flux density of 12 kG and a coercive force of 30 kOe. In the conventional magnet 101, the amount of Dy used (content ratio relative to the entire magnet) is 8%.

  In the conventional magnet 102 which is a split magnet, the ratio in the longitudinal direction of the high coercivity magnet part 102A is 0.3, and the ratio in the longitudinal direction of the low coercivity magnet part 102B is 0.7. The high coercive force magnet portion 102A has a residual magnetic flux density of 12 kG and a coercive force of 30 kOe, and the low coercive force magnet portion 102B has a residual magnetic flux density of 13 kG and a coercive force of 25 kOe. In the conventional magnet 102, the amount of Dy used (content ratio with respect to the entire magnet) is 6.6%.

  In the magnet 103 of the present invention, the ratio of the diffusion region 103A in the longitudinal direction is 0.3, and the ratio of the non-diffusion region 103B in the longitudinal direction is 0.7. The volume fraction of the entire diffusion region 103A with respect to the magnet is 0.1. The volume fraction of the non-diffusing region 103B with respect to the entire magnet is 0.9. In the diffusion region 103A, the residual magnetic flux density is 12 kG and the coercive force is 30 kOe, and in the non-diffusion region 103B, the residual magnetic flux density is 13 kG and the coercive force is 25 kOe. In the example magnet 103 of the present invention, the amount of Dy used (content ratio relative to the whole magnet) is 6.1%.

  When the average magnetic flux is calculated based on the volume fraction of the conventional magnet 102 and the magnet 103 of the present invention, the average magnetic flux of the conventional magnet 102 is 12.7 kG (= 13 × 0.7 + 12 × 0.3). The torque is increased by 5% and the torque is also increased by 5%. On the other hand, the average magnetic flux of the magnet 103 of the present invention is 12.95 kG (= 13 × 0.9 + 12 × 0.1), which is 8% higher than that of the conventional magnet 102 and the torque is also increased 8%. To do. In addition, since the magnetic flux and the torque of the magnet are proportional to 1: 1, the calculation was made assuming that the magnetic flux improvement becomes the torque improvement.

  As described above, in the magnet of the present invention, compared to the conventional magnets 101 and 102, the amount of Dy used can be reduced, the coercive force can be improved, and the residual magnetic flux density can be reduced.

  DESCRIPTION OF SYMBOLS 1 ... Rotating machine, 11 ... Stator, 21 ... Rotor, 31 ... Magnet, 32, 32A-32D ... Diffusion area, 33, 33A-33D ... Non-diffusion area, 34 ... Surface, C1, C2 ... Ridge part

Claims (5)

In the magnet provided in the rotor of the rotating machine,
A diffusion region in which heavy rare earth elements are diffused from the surface is formed on at least a part of the surface,
In the diffusion region, the coercive force decreases from the surface toward the inside.   The magnet according to claim 1, wherein the diffusion region is a ridge line portion that is parallel to a rotation axis of the rotor and is adjacent to a stator of the rotating machine.   The magnet according to claim 1, wherein the diffusion region is an outer peripheral edge adjacent to a stator of the rotating machine. In the diffusion region, the coercive force is higher than the non-diffusion region other than the diffusion region,
The magnet according to claim 1, wherein the non-diffusion region has a residual magnetic flux density higher than that of the diffusion region.   A rotating machine comprising the magnet according to claim 1.

Images