JP2017070037A - Rotor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotor which can prevent occurrence of failure without damaging advantages of injection molding when a bond magnet is embedded into a magnet hole of a rotor core by the injection molding.SOLUTION: A rotor 10 comprises: a rotor core 12 that has a plurality of magnet holes 14, is formed by laminating a plurality of core sheets S made of a magnetic steel sheet, and has a cylindrical shape; and a bond magnet 16 that includes magnetic powder and a resin binder, and is filled into each of the magnet holes 14. When the thickness of the bond magnet 16 is T and an axial direction length of the rotor core 12 is L, the thickness T and the axial direction length L satisfy a relation of L/T≤25. As the bond magnet 16 can be embedded into each of the magnet holes 14 by single injection molding, occurrence of failure such as insufficient filling of a magnet material constructing the bond magnet 16 and deformation of the rotor core 12 can be prevented without impairing advantages of the injection molding.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a rotor used in a radial gap type rotating electrical machine, and more particularly to a rotor for an embedded magnet type rotating electrical machine.

  A radial gap type rotating electrical machine is a rotating electrical machine including a rotor disposed to be rotatable about a rotation axis and a stator disposed with a gap in the radial direction of the rotor. There exists what is called an interior permanent magnet (Interior Permanent Magnet) type | mold (henceforth "IPM type | mold") in this kind of rotary electric machine.

  A general rotor for an IPM type rotating electrical machine includes a cylindrical rotor core in which a plurality of core sheets made of electromagnetic steel sheets are laminated. The rotor core is provided with a plurality of magnet holes penetrating in the axial direction in the circumferential direction at equal pitches. A magnet is embedded in each of the magnet holes.

  Patent Document 1 discloses a rotor in which each of the magnets is a bonded magnet. Each of the bonded magnets is formed by magnetizing and hardening a magnet material containing magnetic powder and a resin binder in each magnet hole. The bonded magnet can be embedded in the magnet hole using a known injection molding machine by applying “injection molding” which is a known technique relating to molding and processing of resin. This makes it possible to enjoy the advantages of injection molding with excellent productivity of molded products with complicated shapes, increasing the degree of freedom regarding the shape of the magnet holes, and embedding bonded magnets in multiple magnet holes at once. Is possible.

  However, bond magnet injection molding has the drawback of low material fluidity compared to resin injection molding. One reason is that “the temperature of the magnet material”, which is one of the molding conditions of injection molding, cannot be set to a temperature equal to or higher than the Curie temperature unique to the magnetic powder contained in the magnet material. If the fluidity is low, the magnet material is not well filled in the magnet hole, and not only the advantages of the injection molding can be enjoyed, but also productivity and yield may be deteriorated.

  On the other hand, it is conceivable to increase the “injection pressure”, which is another molding condition, to compensate for the above-mentioned difficulty. In this case, however, the mechanical strength of the rotor core is insufficient, and the outer peripheral surface bulges in the radial direction. There is a risk of such deformation. On the other hand, if the number of injection moldings is increased under the molding conditions that do not cause the above-mentioned problems and the magnet material is refilled from the opposite side of the magnet hole, the occurrence of the problems itself can be prevented, but the production man-hours and Since the lead time is increased, the advantages of the injection molding are impaired.

JP 2005-269734 A

  In view of the above-described problems, an object of the present invention is to provide a rotor capable of preventing the occurrence of the above-described problems without impairing the advantages of the injection molding as much as possible.

  In order to achieve the above object, a rotor according to the present invention includes a cylindrical rotor core having a plurality of magnet holes and a plurality of core sheets made of electromagnetic steel sheets, a magnetic powder, and a resin binder. A bonded magnet filled in each of the magnet holes, where the thickness of the bonded magnet is T and the axial length of the rotor core is L, the thickness T and the axial length L are , L / T ≦ 25 is satisfied.

  In the rotor having the first configuration, the rotor core is provided with a skew in each of the magnet holes, and the thickness T and the axial length L satisfy a relationship of L / T ≦ 20. It may be characterized by.

  The rotor of the present invention includes a plurality of cylindrical core blocks having a plurality of magnet holes and a plurality of core sheets made of electromagnetic steel plates, and each of the core blocks is coaxially connected. A plurality of bond magnets that are filled in each of the magnet holes and divided in the axial direction at the boundary surface between the connected core blocks of the rotor core, and the thickness of the bond magnet is T, where L is the axial length of the rotor core, the thickness T and the axial length L satisfy the relationship L / T> 25.

  In the rotor having the second configuration, the rotor core is provided with a skew in each of the magnet holes, and the thickness T and the axial length L satisfy a relationship of L / T> 20. It may be characterized by.

  The magnetic powder may include an Nd-Fe-B magnet.

  Furthermore, the resin binder may be a nylon resin or a polyphenylene sulfide resin.

  According to the rotor of the present invention, since it is configured to satisfy the above relational expression, when the bond magnet is embedded in each of the magnet holes provided in the rotor core by injection molding, the bond magnet is configured as much as possible. Since the influence of the temperature change of the magnet material can be reduced, it is possible to prevent the occurrence of the above problems such as insufficient filling of the bond magnet in the magnet hole and deformation of the rotor core without impairing the advantages of the injection molding.

(A) is a top view which shows the rotor which concerns on embodiment, (b) is a perspective view which shows the rotor. (A) is sectional drawing of a rotor core, (b) is a figure which shows the relationship between the axial direction length of the said rotor core, and the temperature change of a magnet material. It is a perspective view which shows the rotor which concerns on the modification of the said embodiment. (A) is a perspective view which shows the rotor which concerns on other embodiment, (b) is a perspective view which shows the modification of the rotor which concerns on other embodiment. It is a perspective view which shows the rotor which concerns on the other modification of other embodiment.

  Hereinafter, embodiments of a rotor according to the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the rotor 10 according to the embodiment includes a cylindrical rotor core 12. The rotor core 12 is provided with four magnet holes 14 penetrating in the axial direction (also simply referred to as “axial direction”). Bonded magnets (hereinafter simply referred to as “magnets”) 16 are embedded in the respective magnet holes 14. A hollow portion surrounded by the inner peripheral surface of the rotor core 12 is a shaft hole 18, and a rotation shaft (not shown) is fitted into the shaft hole 18 so as to be coaxial with the rotor core 12. The rotor 10 which is a component of the IPM type rotating electrical machine (not shown) is disposed so as to face the stator (not shown) with a gap in the radial direction.

  The rotor core 12 is a laminated body in which a plurality of core sheets S are laminated. The core sheet S is made of an electromagnetic steel sheet in which a soft magnetic material is rolled into a thin plate shape having a thickness of about 0.2 to 1 mm (preferably about 0.3 to 0.5 mm) and the surface thereof is subjected to an insulation treatment. Each of the core sheets S has a hollow disk shape having a circular hole S8 at the center thereof. Each of the core sheets S is provided with four through holes S4 having the same shape in the circumferential direction at an equal pitch (at an interval of 90 degrees in mechanical angle). Each of the through holes S4 is a belt-shaped arc-shaped hole that protrudes toward the circular hole S8. In FIG. 1A, among the magnet holes 14 arranged vertically and horizontally, the portion of the magnet hole 14 positioned at the lower portion is provided with the sign of the through hole S4 of the core sheet S at the axial end portion of the rotor core 12. It is attached.

  In the rotor core 12, the core sheets S are laminated so that the positions of the through holes S4 between the core sheets S adjacent in the axial direction are aligned, that is, the corresponding S4s are overlapped with each other. As a result, in the rotor core 12, one magnet hole 14 is formed by each of the through holes S4 that are communicated in the axial direction, and similarly configured magnet holes 14 are arranged at an equal pitch in the circumferential direction. A total of four are formed at a mechanical angle of 90 degrees. Similarly, a shaft hole 18 is formed in the rotor core 12 by each of the circular holes S8 that are communicated in the axial direction.

  Each of the magnets 16 is filled with a magnet material including magnetic powder and a resin binder in the corresponding magnet hole 14 by “injection molding” described later, and is magnetized and cured. Therefore, the shape of each magnet 16 is substantially the same as the shape of the corresponding magnet hole 14. Specifically, the shape of the cross section of each magnet 16 cut by a virtual plane (not shown) orthogonal to the axial direction is the shape of the magnet hole 14 (through hole S4) in plan view (FIG. 1A). )), And has a curved plate shape (FIG. 1 (b)) having a convex curved surface as a main surface on the shaft hole 18 (circular hole S8) side.

  In each of the magnets 16, the curved surfaces on the outer peripheral surface side of the rotor core 12 are magnetic pole surfaces 16N and 16S magnetized to different polarities (N poles and S poles) between the magnets 16 adjacent to each other in the circumferential direction. Yes. Each of the magnets 16 serves as a magnetomotive force source, and the rotor core 12 is magnetized. A four-pole magnetic pole MP in which N poles and S poles are alternately arranged in the circumferential direction is formed on the outer peripheral portion of the magnetized rotor core 12 facing the magnetic pole faces 16N and 16S.

  In this example, among the magnet materials constituting each of the magnets 16, the magnetic powder includes neodymium (Nd), iron (Fe), boron (B) as main components, and a neodymium magnet having excellent magnetic properties ( Nd-Fe-B magnets) are used. As the resin binder, polyphenylene sulfide (PPS) resin having good fluidity and excellent heat resistance is used. Each of the magnets 16 is magnetized so that the easy magnetization axis of the magnetic powder is aligned in the d-axis direction (a direction along a line (not shown) connecting the center of the magnetic pole MP and the axis of the rotor core 12). Thus, it is composed of an anisotropic bonded magnet having a strong magnetic force in the d-axis direction.

  In the rotor 10 having the above-described configuration, each of the magnets 16 applies “injection molding”, which is a known technique related to molding and processing of resin, and utilizes a known “injection molding machine” to respectively correspond to the corresponding magnet holes 14. Buried in In the following, illustration of the known “injection molding machine” and “each step of injection molding” is omitted, and the injection molding of the magnet 16 will be described together with an outline of injection molding by a general injection molding machine.

  The injection molding machine includes a mold composed of a fixed mold and a movable mold. Clamping is performed by a mold clamping mechanism in a state where the rotor core 12 is set in the mold, and a magnet material is filled into each of the magnet holes 14 through the mold by the injection mechanism. At that time, the magnet 16 is magnetized by applying a magnetic field with the magnetic field orientation mold facing the outer peripheral surface of the rotor core 12. The magnet 16 magnetized by the magnetization is cured, and the rotor core 12 is taken out from the mold. In this way, the magnet 16 is embedded in each of the magnet holes 14 of the rotor core 12.

  Here, in the injection molding, the magnet material is heated in the injection mechanism to melt the resin binder, and the entire magnet material has a certain fluidity. The temperature of the magnet material in this state is hereinafter referred to as “injection temperature”. Further, there is a temperature at which the crystallization speed of the resin binder reaches a peak in the process of cooling and curing the resin binder of the magnet material filled in the magnet hole 14 from the molten state. This peak temperature specific to the resin binder is hereinafter referred to as “crystallization temperature”.

  The molding conditions in injection molding include various conditions such as the above injection temperature, injection pressure, and mold temperature. These molding conditions depend on the shape and size of the molded product and the type of material (resin). By controlling, mass production of molded products is realized with high accuracy. However, as already described in the above background art, in the injection molding of the magnet 16 as in this example, some restrictions specific to the magnet material are imposed on the molding conditions. There is a possibility that problems such as insufficient filling (short shot) and deformation (bulging) of the rotor core 12 may occur. On the other hand, by increasing the number of injection moldings under molding conditions in which such defects do not occur, and by refilling the magnet material from the opposite side of the short-shot magnet hole 14, the occurrence of the defects is prevented. However, since it leads to an increase in production man-hours and lead time, the advantages of injection molding are impaired.

  Therefore, as a result of intensive studies, the present inventors have paid attention to the temperature change of the magnet material from the injection temperature to the crystallization temperature. It has been found that the above-mentioned problems can be prevented without impairing the advantages of injection molding. Specifically, when the thickness of the magnet 16 is T and the axial length of the rotor core 12 is L, the thickness T and the axial length L satisfy the relationship L / T ≦ 25. It is characterized in that it is added as one of the design conditions of the rotor core 12.

  The tendency of the temperature change of the magnet material from the injection temperature to the crystallization temperature will be described with reference to FIG. FIG. 2A shows a cross section of the rotor core 12 set in a mold (not shown). The thickness T (FIG. 1A) of the magnet 16 that is injection-molded in the magnet hole 14 provided in the rotor core 12 may be regarded as the same as the thickness t of the magnet hole 14. In FIG. 2A, for comparison, a magnet hole 14s having a thickness ts smaller than the thickness t of the magnet hole 14 is indicated by a two-dot chain line.

  In the graph shown in FIG. 2 (b), the magnet material was filled into the magnet hole 14 (magnet hole 14s) of the rotor core 12 shown in FIG. 1 (a) by injection molding from the left side of the paper under the same molding conditions. The state of the temperature change of the magnet material is shown. In FIG. 2B, the temperature change in the magnet hole 14 is indicated by a “solid line”, and the temperature change in the magnet hole 14s is indicated by a “two-dot chain line”.

  In the magnet hole 14, the temperature of the magnet material gradually decreases from the injection temperature as the position of the rotor core 12 in the axial length L moves away from the injection side (filled side). And even after reaching the crystallization temperature, the magnet material is filled up to the back of the magnet hole 14 (the end opposite to the filled side) while gradually decreasing in temperature. On the other hand, in the magnet hole 14 s, as with the magnet hole 14, the temperature of the magnet material decreases from the injection temperature as the distance from the injection side increases, but the degree of the decrease is greater than in the magnet hole 14. For this reason, the crystallization temperature is reached at a position close to the injection side, and as a result, the magnet material is not filled to the back of the magnet hole 14s, and a short shot state is obtained.

  From this, even under the same molding conditions, if the thicknesses t and ts of the magnet holes 14 and 14s are different, the magnet 16 can be embedded by injection molding (magnet hole 14) and not (magnet hole 14s). You can see that there is. Even if the molding conditions for injection molding are changed to fill the magnet hole 14s with the magnet material, the injection temperature has a restriction of "curie temperature unique to magnetic powder", and if the injection pressure is increased excessively, The rotor core 12 is deformed.

  In this regard, in the rotor 10 of the present embodiment, the rotor core 12 is configured to satisfy the above relational expression (L / T ≦ 25), and thus is within the range of the molding conditions in which the above restrictions are imposed. However, the magnet 16 can be embedded in each of the magnet holes 14 provided in the rotor core 12 without causing problems such as a short shot by one injection molding. Thus, according to the rotor 10 of this embodiment, since the influence of the temperature change of the magnet material which comprises the magnet 16 can be reduced, generation | occurrence | production of an above-described malfunction can be prevented, without impairing the advantage of injection molding. .

  Note that the short shot or the like described above is likely to occur when, for example, the axial length L of the rotor core 12 is considerably long, or when the thickness T of the magnet 16 (the thickness t of the magnet hole 14) is considerably small. There is a tendency. In recent years, various techniques for improving the magnetic properties of bonded magnets have been developed, and the shape of the magnet hole 14 formed in the rotor core 12 can be complicated from various technical viewpoints. Therefore, the rotor 10 of the present embodiment can be widely applied, for example, from an IPM type rotating electrical machine having a maximum output of about 1 kw to a large-sized or highly functional IPM type rotating electrical machine.

  While the rotor 10 according to the embodiment has been described above, the present invention can be implemented in other forms. In the following description, components having basically the same configuration as those in the above embodiment are denoted by the same reference numerals, and the explanation regarding matters common to those in the above embodiment is only a simple reference. Or, it will be omitted as appropriate.

[Modification]
In the rotor 10 of the above-described embodiment, each of the magnet holes 14 penetrates in parallel to the axial direction of the rotor core 12. However, like the rotor 20 shown in FIG. 3, the rotor core 22 is a magnet provided with a skew. A configuration in which the holes 24 are formed may be used. The rotor core 22 is a laminated body in which the same plurality of core sheets S as the rotor core 12 described above are laminated in a state where the through holes S4 of the adjacent core sheets S are shifted from each other by a predetermined angle in the circumferential direction. Each of the magnet holes 24 is inclined at a fixed skew angle with respect to the axial direction of the rotor core 22.

  In the rotor 20 according to the modification, when the thickness of the magnet 26 is T and the axial length of the rotor core 22 is L, the thickness T and the axial length L satisfy the relationship of L / T ≦ 20. It is configured as follows. On the inner wall surface of the magnet hole 24 provided with the skew, a stepped portion (not shown) is formed. Therefore, when the axial length L is the same, the magnet hole 24 has a larger contact area with the magnet material than the magnet hole 14 described above. Further, when the skew is provided like the magnet hole 24, the flow resistance of the magnet material is higher than that of the straight magnet hole 14. Due to these effects, the temperature drop of the magnet material is accelerated, and the position reaching the crystallization temperature in the magnet hole 24 approaches the injection side. For this reason, in the rotor 20, the axial length that enables the magnet 26 to be embedded in each of the magnet holes 24 provided in the rotor core 22 without causing problems such as short shots by one injection molding. The length L is shorter than that of the rotor 10 described above.

[Other Embodiments and Modifications]
In both of the above-described embodiments and modifications thereof, a relational expression that enables a magnet to be embedded in each of the magnet holes provided in the rotor core without causing problems such as short shots by one injection molding. Although the rotor is configured to satisfy the requirements, the number of injection moldings is not limited to one at a time as long as the advantages of injection molding are not impaired in producing one rotor.

  For example, the rotor 30 according to another embodiment shown in FIG. 4A includes a plurality of core blocks 32B and 32B having the same configuration as the rotor core 12 described above. Each of the core blocks 32B and 32B is provided with four magnet holes 34 as with the rotor core 12. In each of the magnet holes 34, magnets 36 are respectively embedded by injection molding in the same manner as the magnet 16 described above. That is, each of the core blocks 32B embedded in the magnet holes 34 corresponding to the magnets 36 has the same configuration as that of the rotor 10 described above.

  The core blocks 32B and 32B are connected coaxially to form the rotor 30. In other words, the rotor 30 is formed by connecting two rotors 10 coaxially. For this reason, in the rotor 30, the rotor core 32 is comprised by the two core blocks 32B and 32B connected coaxially, and there exists a boundary surface BP between the core blocks 32B and 32B adjacent to each other in the axial direction. Further, the magnets 36 embedded in the respective magnet holes 34 of the rotor core 32 are divided in the axial direction on the boundary surface BP. For connecting the core blocks 32B and 32B, known fixing means (not shown) such as bolts and nuts are used.

  In the rotor 30 having the above-described configuration, when the thickness of the magnet 36 is T and the axial length of the rotor core 32 is L, the thickness T and the axial length L satisfy the relationship L / T> 25. It has a configuration like this. The rotor 30 that satisfies such a relational expression does not satisfy the relational expression for the rotor 10 as a whole, and the axial length L of the rotor core 32 is twice that of the rotor core 12. For this reason, in one injection molding, the magnet 36 cannot be embedded in each of the magnet holes 34 without causing problems such as short shots.

  However, when viewed in units of one core block 32B, the above-described relational expression (L / T ≦ 25) in the rotor 10 is satisfied. In short, due to the axial length L of the rotor core 32, the rotor 30 cannot embed the magnet 36 in each of the magnet holes 34 by one injection molding. It is a configuration that can be achieved.

  The same can be said for the rotor 40 according to the modified example of the other embodiment shown in FIG. The rotor 40 is formed by providing a skew in each of the magnet holes 34 of the rotor 30 and forming a magnet hole 44. Accordingly, each of the core blocks 42B embedded in the magnet holes 44 corresponding to the magnets 46 has the same configuration as the rotor 20 described above. In the rotor 40 having the above configuration, when the thickness of the magnet 46 is T and the axial length of the rotor core 42 is L, the thickness T and the axial length L are L / T> 20. It is the composition which satisfies.

[Other variations]
Further, as in a rotor 50 according to another modification shown in FIG. 5, each of the magnet holes 54 provided in the rotor core 52 may be skewed in units of the core block 52B. Such a skew is called a stage skew. Each of the core blocks 52B and 52B has the same configuration as that of the rotor 10 described above. The upper and lower core blocks 52B and 52B are coaxially connected by shifting one magnet hole 54 in the circumferential direction with respect to the other magnet hole 54. As a result, the magnets 56 divided vertically are displaced in the circumferential direction in the same manner as the magnet hole 54. In the step skew, the axial lengths of the core blocks 52B and 52B may be the same or different.

[Still other variations]
(1) In each of the above-described embodiments and modifications, a total of four magnetic poles having four magnets as a magnetomotive force source and having N and S poles alternately arranged in the circumferential direction of the rotor core are formed. However, the number of poles of the magnetic pole is not particularly limited as long as it is an even number. For example, it may have two poles, six poles, or more.

  (2) In each of the above-described embodiments and modifications, the shape of the magnet is a curved plate having a circular cross section, but other shapes such as a flat plate shape, a V shape, and a W shape are possible. You may have a shape. Further, the end portion of the magnet may have an end portion bent from one end of the main body portion toward the peripheral surface of the rotor core.

  (3) In each embodiment and each modification described above, one magnetic pole is formed per magnet, but one magnetic pole is formed by two or more magnets. It does not matter.

  (4) In each of the above-described embodiments and modifications, the neodymium-based material mainly containing neodymium (Nd), iron (Fe), and boron (B) as the magnetic powder contained in the material of the magnet (bonded magnet). A magnet (Nd—Fe—B magnet) powder is used, but a magnet containing other magnetic powder may be used. Other magnetic powders include samarium-based magnets (Sm-Fe-N-based magnets) that contain samarium (Sm), iron (Fe), and nitrogen (N) as main components, and composite magnetism of neodymium-based magnets and samarium-based magnets. Materials and the like.

  (5) In each of the above-described embodiments and modifications, polyphenylene sulfide resin is used as the resin binder contained in the material of the magnet (bonded magnet), but other resins may be used. Other resin binders are not particularly limited as long as they are suitable for injection molding, such as nylon resins and other thermoplastic resins, or thermosetting resins such as phenol resins and epoxy resins.

  (6) Each of the above-described embodiments and modifications exemplifies the inner rotor disposed on the inner peripheral side of the stator, but the present invention is applied to the outer rotor disposed on the outer peripheral side of the stator. Of course, it is also possible.

  The present invention can be implemented in a mode in which various improvements, modifications, or variations are added based on the knowledge of those skilled in the art without departing from the spirit of the present invention. Moreover, you may implement with the form which substituted any invention specific matter to the other technique within the range which the same effect | action or effect produces.

10-50 Rotor 12-52 Rotor core 32B-52B Core block 14-54 Magnet hole 16-56 Magnet (bond magnet)
T Magnet (bonded magnet) thickness L Rotor core axial length BP Boundary surface

Claims (6)

A cylindrical rotor core having a plurality of magnet holes and a plurality of core sheets made of electromagnetic steel plates are laminated;
A bonded magnet containing magnetic powder and a resin binder and filled in each of the magnet holes;
With
A rotor characterized in that the thickness T and the axial length L satisfy the relationship L / T ≦ 25, where T is the thickness of the bonded magnet and L is the axial length of the rotor core. The rotor core is provided with a skew in each of the magnet holes,
The rotor according to claim 1, wherein the thickness T and the axial length L satisfy a relationship of L / T ≦ 20. A rotor core having a plurality of magnet holes, including a plurality of cylindrical core blocks formed by laminating a plurality of core sheets made of electromagnetic steel sheets, each of the core blocks being connected coaxially;
A plurality of bonded magnets filled in each of the magnet holes and divided in the axial direction at the interface between the connected core blocks of the rotor core;
With
A rotor characterized in that the thickness T and the axial length L satisfy the relationship L / T> 25, where T is the thickness of the bonded magnet and L is the axial length of the rotor core. The rotor core is provided with a skew in each of the magnet holes,
The rotor according to claim 3, wherein the thickness T and the axial length L satisfy a relationship of L / T> 20.   The rotor according to any one of claims 1 to 4, wherein the magnetic powder includes an Nd-Fe-B magnet.   The rotor according to any one of claims 1 to 5, wherein the resin binder is a nylon resin or a polyphenylene sulfide resin.

Images