ROTOR CORE AND METHOD FOR MANUFACTURING ROTOR CORE

Abstract

To provide a rotor core with a secondary conductor and a rotor core manufacturing method.SOLUTION: A rotor core includes a body portion formed by stacking a plurality of plate members made of a first metal in the direction of the rotation axis. The rotor core has a through hole extending through the main body in the rotation axis direction. The rotor core includes a secondary conductor disposed in the through hole. The secondary conductor is made of a second metal different from the first metal. A bonding layer containing carbon as a main component is formed on the contact surface between the inner wall of the through hole and the secondary conductor. The first metal and carbon are chemically bonded between the inner wall of the through hole and the bonding layer. The second metal and carbon are chemically bonded between the secondary conductor and the bonding layer.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a rotor core and a method for manufacturing a rotor core. [Background technology]

[0002] Patent Document 1 discloses a rotor core for an induction motor. The rotor core is formed by laminating electromagnetic steel sheets. A plurality of through holes extending in the direction of the rotation axis are formed in the outer periphery of the rotor core. Copper conductor bars are arranged inside the plurality of through holes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5155420 Summary of the Invention [Problem to be solved by the invention]

[0004] To realize a highly efficient motor, it is necessary to make the air gap between the outer circumference of the rotor core and the inner circumference of the stator as small as possible. However, when the rotor core rotates, centrifugal force is generated in the conductor bars that moves them toward the outer circumference, which can cause the conductor bars to protrude into the air gap, making it difficult to achieve high rotation speeds. One way to prevent the conductor bars from protruding out is to join the conductor bars to the rotor core, but joining is difficult because the conductor bars and the electromagnetic steel sheets are dissimilar metals. [Means for solving the problem]

[0005] The rotor core disclosed in this specification includes a main body portion formed by stacking a plurality of plate materials made of a first metal in the direction of the rotation axis. The rotor core includes a through hole extending in the main body portion in the direction of the rotation axis. The rotor core includes a secondary conductor disposed in the through hole. The secondary conductor is made of a second metal different from the first metal. A bonding layer mainly composed of carbon is formed on a contact surface between an inner wall of the through hole and the secondary conductor. The first metal and carbon are chemically bonded between the inner wall of the through hole and the bonding layer. The second metal and carbon are chemically bonded between the secondary conductor and the bonding layer.

[0006] The first metal located on the inner wall of the through hole and the second metal that constitutes the secondary conductor can be chemically bonded via a bonding layer. This makes it possible to firmly bond the first metal and the second metal together. Since the secondary conductor does not protrude from inside the through hole to the outer periphery when the rotor core rotates, high speed rotation is possible.

[0007] The bonding layer may have a carbon concentration that decreases from the central region toward the inner wall of the through hole, and from the central region toward the secondary conductor. This allows the first metal and carbon to be chemically bonded to each other in the central region of the bonding layer, and allows the second metal and carbon to be chemically bonded to each other. The first metal and the second metal can be bonded together via the carbon.

[0008] The bonding layer may include a carbide of a first metal and a carbide of a second metal. The concentration of the carbide of the first metal may decrease from the central region toward the inner wall of the through hole, and the concentration of the carbide of the second metal may decrease from the central region toward the secondary conductor. This allows the carbide of the first metal to chemically bond the first metal to carbon in the central region of the bonding layer, and the carbide of the second metal to chemically bond the second metal to carbon. The first metal and the second metal can be bonded together via carbon.

[0009] The bonding layer may include carbon that is not bonded to the first metal and the second metal.

[0010] The second metal may be a metal having a higher density than the first metal.

[0011] The first metal may be iron and the second metal may be copper.

[0012] The manufacturing method of the rotor core disclosed in this specification is a manufacturing method of a rotor core including a main body formed by stacking a plurality of plate materials made of a first metal in the rotation axis direction, a through hole extending in the main body in the rotation axis direction, and a secondary conductor made of a second metal different from the first metal. The manufacturing method includes a step of arranging the secondary conductor inside the through hole. The manufacturing method includes a step of arranging a solution containing carbon between the inner wall of the through hole and the secondary conductor. The manufacturing method includes a step of forming a bonding layer mainly composed of carbon by heating the area where the solution is arranged. Between the inner wall of the through hole and the bonding layer, the first metal and carbon are chemically bonded. Between the secondary conductor and the bonding layer, the second metal and carbon are chemically bonded. This allows the first metal located on the inner wall of the through hole to be chemically bonded to the second metal constituting the secondary conductor via the bonding layer. It becomes possible to firmly bond the first metal and the second metal together.

[0013] The carbon contained in the solution is composed of carbon atoms and may have a double bond. By heating, the double bond of the carbon is opened to generate a bond. The generated bond can then be chemically bonded to the first metal atom and the second metal atom.

[0014] The carbon contained in the solution may include fullerene or carbon nanotubes. Fullerene or carbon nanotubes contain many double bonds. Therefore, by opening the double bonds, many bonds can be generated.

[0015] The area where the solution is disposed may be heated by laser irradiation. Since localized heating is possible by laser, the heating time can be shortened, and the manufacturing cost can be reduced. [Brief description of the drawings]

[0016] [Figure 1] FIG. 2 is a top view of the rotor core 1. [Diagram 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Diagram 3] FIG. 2 is an enlarged view of a portion indicated by region III in FIG. [Figure 4] 2 is an enlarged cross-sectional view of the vicinity of the bonding layer 15. FIG. [Diagram 5] 3 is a flow diagram illustrating a manufacturing method of the rotor core 1. FIG. [Figure 6] FIG. 1 shows the structure of C60 fullerene. [Figure 7] 13A and 13B are diagrams showing modified examples of the cross-sectional shape of a through hole 11h. [Figure 8] 13A and 13B are diagrams showing modified examples of the cross-sectional shape of a through hole 11h. [Figure 9] FIG. 1 shows a structure having multiple conductive wires 12a. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] <Structure of rotor core 1> Fig. 1 shows a top view of a rotor core 1 according to this embodiment. Fig. 2 shows a cross-sectional view taken along line II-II in Fig. 1. Fig. 3 shows an enlarged view of a portion indicated by region III in Fig. 1. The rotor core 1 is a squirrel-cage rotor of an induction motor. In Figs. 1 and 2, the stator is omitted. For ease of viewing, end rings 13 are indicated by dashed lines in Fig. 1, and are omitted in Fig. 3. Fig. 2 also shows a state in which the rotor shaft 20 is inserted into the rotor shaft insertion hole 11r.

[0018] The rotor core 1 includes a main body 11, conductor bars 12, and end rings 13 and 14. The main body 11 is formed into a cylindrical shape by laminating a plurality of electromagnetic steel plates in the rotor shaft 20 direction (z direction). A ferromagnetic material such as iron containing silicon is used for the electromagnetic steel plates. A rotor shaft insertion hole 11r is formed in the center of the main body 11, into which the rotor shaft 20 is inserted.

[0019] In addition, a plurality of through holes 11h extending in the rotor shaft 20 direction are formed in the outer periphery of the main body 11. The through holes 11h have a substantially rectangular cross section perpendicular to the longitudinal direction. The through holes 11h extend from the upper surface 11u to the lower surface 11b of the main body 11. The plurality of through holes 11h are arranged rotationally symmetrical with respect to the rotor shaft insertion hole 11r. Therefore, in the specification, a single through hole 11h may be described. The through hole 11h is also provided with a communication hole 11c communicating with the outer periphery of the main body 11 and extending in the rotor shaft 20 direction. The through hole 11h is partially open to the outer periphery of the main body 11 by the communication hole 11c.

[0020] The conductor bar 12 is a conductor constituting a secondary conductor. The metal forming the conductor bar 12 is a metal having a higher density than the metal forming the main body 11. In this embodiment, the metal forming the conductor bar 12 is copper (density: 8.94 g / cm 3 The metal forming the main body 11 was an electromagnetic steel sheet (iron containing a few percent silicon) (density: 7.87 g / cm 3 ).

[0021] The end rings 13 and 14 are provided on the upper surface 11u and the lower surface 11b, respectively, of the main body 11. The end rings 13 and 14 are configured to short-circuit the conductor bars 12 by being connected to both axial ends of the conductor bars 12. The conductor bars 12 and the end rings 13 and 14 may be joined to each other by brazing using a brazing material such as silver brazing or friction stir welding.

[0022] As shown in the enlarged view of FIG. 3, a bonding layer 15 is formed between the inner wall 11w of the main body 11 and the surface of the conductor bar 12. FIG. 4 shows an enlarged cross-sectional view of the vicinity of the bonding layer 15. The bonding layer 15 is a layer mainly composed of carbon. Specifically, the bonding layer 15 has a structure in which iron carbide, copper carbide, iron, and carbon not bonded to copper are mixed. Here, a region existing at a position approximately equidistant from the inner wall 11w and the surface of the conductor bar 12 is defined as a central region CR. The bonding layer 15 has the highest carbon concentration in the central region CR. The carbon concentration and the iron carbide concentration decrease from the central region CR toward the inner wall 11w of the main body 11 (arrow A1 side). The carbon concentration and the copper carbide concentration decrease from the central region CR toward the conductor bar 12 (arrow A2 side).

[0023] As described above, the concentrations of carbon, iron carbide, and copper carbide are gradually decreased. Therefore, the interface between the main body 11 and the bonding layer 15 and the interface between the conductor bar 12 and the bonding layer 15 actually have widths and may not be clearly defined. However, in Figures 3 and 4, the interface of the bonding layer 15 is shown by a solid line for convenience.

[0024] <Manufacturing method of rotor core 1> The manufacturing method of the rotor core 1 will be described with reference to the flow diagram of Fig. 5. In step S1, a process of arranging the conductor bar 12 inside the through hole 11h is performed. Specifically, the conductor bar 12 is inserted into the through hole 11h from the upper surface 11u or the lower surface 11b. After insertion, a gap is formed between the inner wall 11w of the through hole 11h and the surface of the conductor bar 12 due to fit tolerance.

[0025] In step S2, a solution containing carbon is placed in the gap between the inner wall 11w and the conductor bar 12. The solution can be placed in the gap by surface tension. The carbon contained in the solution is composed of simple carbon and has a double bond. In this embodiment, the carbon contained in the solution is fullerene, and the solvent is an organic solvent (e.g., xylene). Fullerene is C 60It is not limited to fullerene, but may include higher fullerenes consisting of 70 or more carbon atoms.

[0026] The solution may be arranged in various ways. For example, with the conductor bar 12 arranged inside the through-hole 11h, the solution may be poured from above the through-hole 11h as shown by the arrow A3 in Fig. 2. Also, for example, the solution may be applied to the surface of the conductor bar 12, and then the conductor bar 12 may be inserted into the through-hole 11h.

[0027] In step S3, a process of forming a bonding layer 15 is performed by heating the area where the solution is placed. The heating temperature is equal to or higher than the temperature at which carbon reacts with iron or copper. Various heating methods may be used. In this embodiment, heating was performed by laser irradiation. Laser irradiation allows for localized heating compared to heating the main body 11 in a furnace. Therefore, the heating time can be shortened, and manufacturing costs can be reduced. In addition, various laser irradiation methods may be used. In this embodiment, the laser was irradiated from the direction of the arrow A3 in FIG. 2.

[0028] The specific contents of the process of forming the bonding layer 15 will be described. By heating the area where the solution is placed, carbon can be penetrated and diffused (carburized) from the surface of the inner wall 11w to the inside, and carbon can be penetrated and diffused (carburized) from the surface of the conductor bar 12 to the inside. Carburization can be performed even when an oxide film or a film of a contaminant is present on the surface of the inner wall 11w or the conductor bar 12. In addition, by heating, the iron forming the inner wall 11w can be reacted with the carbon in the solution, and the iron and carbon can be chemically bonded. In addition, by heating, the copper forming the conductor bar 12 can be reacted with the carbon in the solution, and the copper and carbon can be chemically bonded. The carbon not used in the reaction is present in the bonding layer 15 in a state not bonded to the iron and copper. As a result, the bonding layer 15 is formed as shown in FIG. 4.

[0029] As described above, before heating, a gap exists between the inner wall 11w and the conductor bar 12. A gap also forms when the surface roughness of the inner wall 11w or the conductor bar 12 is large. In the heating process of step S3, at least a part of the gap can be filled with the bonding layer 15. This is because the volume of the inner wall 11w or the conductor bar 12 can be expanded by carburizing the inner wall 11w or the conductor bar 12 with carbon. This allows the inner wall 11w and the conductor bar 12 to be bonded via the bonding layer 15.

[0030] A specific model of the formation process of the bonding layer 15 will be described. 60 The structure of fullerene is shown below. 60 Fullerene has a stable structure with 20 six-membered rings and 12 five-membered rings. It also has 30 double bonds. When the carbon of the fullerene is excited by the heating process of step S3, the double bonds can be opened. The bonds generated by the ring opening can be chemically bonded to the iron atoms of the inner wall 11w and the copper atoms of the conductor bar 12. This produces iron carbide and copper carbide. An interface between the generated iron carbide and copper carbide is formed in the vicinity of the central region CR (see FIG. 4). At the interface between the iron carbide and copper carbide, a structure is formed in which one carbon atom is shared between the iron atom and the copper atom. That is, in the vicinity of the central region CR, a state is formed in which the iron atom and the copper atom are chemically bonded via the carbon atom.

[0031] As a result, iron and carbon can be chemically bonded between the inner wall 11w and the bonding layer 15. Also, copper and carbon can be chemically bonded between the conductor bar 12 and the bonding layer 15. That is, the inner wall 11w and the conductor bar 12 can be chemically bonded via the bonding layer 15. Iron and copper, which are dissimilar metals, can be firmly bonded together.

[0032] In step S4, the end rings 13 and 14 are joined to the ends of the conductor bar 12. The joining may be performed by brazing using a brazing material such as silver brazing or by friction stir welding. Through the above steps, the rotor core 1 is completed.

[0033] <Effects> In order to realize a highly efficient motor, it is necessary to make the air gap between the outer circumference of the rotor core 1 and the inner circumference of the stator as small as possible. However, as shown in FIG. 2, when the rotor core 1 rotates, a centrifugal force F1 is generated that moves the conductor bar 12 to the outer circumference. In addition, since the copper constituting the conductor bar 12 has a higher density than the iron constituting the main body portion 11, the centrifugal force F1 is also large. Therefore, the conductor bar 12 may jump out into the air gap, making it difficult to achieve high rotation. In addition, although it is possible to weld the conductor bar 12 to the main body portion 11, there are problems such as a large thermal strain being easily generated at the joint and the difficulty of welding between dissimilar metals. On the other hand, in the technology of this embodiment, the iron located on the inner wall 11w of the through hole 11h and the copper constituting the conductor bar 12 can be chemically bonded via the bonding layer 15. This makes it possible to firmly bond the dissimilar metals, iron and copper, together. When the rotor core 1 rotates, the conductor bar 12 does not jump out from inside the through hole 11h, making it possible to achieve high rotation.

[0034] In the technology of this embodiment, fullerene is used as the carbon contained in the solution. As described with reference to FIG. 6, fullerene contains many double bonds, and therefore many bonds can be generated by opening the double bonds. In addition, fullerene is composed of carbon alone, and therefore no unnecessary chemical modification is performed. Therefore, it is possible to reduce the obstacles when bonding the bonds with iron atoms and copper atoms. In addition, fullerene is more reactive than aromatic compounds such as benzene. As described above, by using fullerene, it is possible to efficiently form the bonding layer 15.

[0035] Specific examples of the technology disclosed in this specification have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples exemplified above. The technical elements described in this specification or the drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. The technology exemplified in this specification or the drawings can achieve multiple objectives simultaneously, and achieving one of the objectives itself has technical utility.

[0036] <Modification> The carbon contained in the solution may be a nanocarbon other than fullerene. For example, a carbon nanotube in which graphene sheets are arranged in a single or multi-layered coaxial tube shape can be used to obtain the same effect.

[0037] The carbon contained in the solution does not have to be composed of simple carbon. For example, it may be a synthetic resin containing an organic portion (e.g., epoxy, acrylate, etc.). It may also be various types of carbides.

[0038] The cross-sectional shape of the through hole 11h may be various. For example, as shown in Fig. 7, a through hole 11c2 having the same width as the through hole 11h may be provided, and the through hole 11h may be completely open to the outer periphery. As shown in Fig. 8, the through hole 11h may not have a through hole, and may be closed toward the outer periphery. The cross-sectional shape of the through hole 11h perpendicular to the longitudinal direction is not limited to a rectangle, and may be various, such as a circle.

[0039] The conductor bar 12 is not limited to an integral structure. For example, as shown in Fig. 9, it may have a structure in which a plurality of conductor wires 12a are wound. In this case, the conductor wires 12a and the through holes 11h can be joined by a joining layer 15 arranged between the conductor wires 12a and the through holes 11h, and the conductor wires 12a can be joined by a joining layer 15 arranged between the conductor wires 12a. The shape of the cross section perpendicular to the longitudinal direction of the conductor bar 12 is not limited to a rectangle, and may be various, such as a circle.

[0040] The material of the main body 11 is not limited to an electromagnetic steel plate, and various materials can be used, such as a cold-rolled steel plate, a hot-rolled steel plate, an aluminum plate, an aluminum alloy plate, or the like.

[0041] The material of the conductor bar 12 is not limited to copper, and various materials can be used. For example, it may be aluminum, an aluminum alloy, a copper alloy, a magnesium alloy, gold, silver, etc. Furthermore, the conductor bar 12 may have various structures. For example, it may be a pressed product, a cast product, a forged product, a die-cast product, etc.

[0042] The heating method in step S3 is not limited to laser irradiation, and various methods can be used, such as indirect furnace heating, contact heating, electrical heating, and induction heating.

[0043] 3, the bonding layer 15 is formed on the entire contact surface between the inner wall 11w and the conductor bar 12, but the present invention is not limited to this. It is sufficient that the bonding layer 15 is formed on at least a part of the contact surface.

[0044] The conductor bar 12 is an example of a secondary conductor. [Explanation of symbols]

[0045] 1: rotor core 11: main body 11h: through hole 11w: inner wall 12: conductor bar 13, 14: end ring 15: joining layer CR: central region

Claims

1. a main body formed by stacking a plurality of plates made of a first metal in a rotation axis direction; a through hole extending in the main body in the direction of the rotation axis; a secondary conductor disposed in the through hole, the secondary conductor being made of a second metal different from the first metal; Equipped with a bonding layer containing carbon as a main component is formed on a contact surface between an inner wall of the through hole and the secondary conductor; the first metal and the carbon are chemically bonded between an inner wall of the through hole and the bonding layer, A rotor core, wherein the second metal and the carbon are chemically bonded between the secondary conductor and the bonding layer.

2. The bonding layer is The carbon concentration decreases from the central region toward the inner wall side of the through hole, The rotor core according to claim 1 , wherein the carbon concentration decreases from the central region toward the secondary conductor.

3. the bonding layer includes a carbide of the first metal and a carbide of the second metal, The concentration of the carbide of the first metal decreases from the central region toward the inner wall side of the through hole, and 3. The rotor core according to claim 1, wherein a concentration of carbides of the second metal decreases from a central region toward the secondary conductor.

4. 4. The rotor core according to claim 1, wherein the bonding layer contains carbon that is not bonded to the first metal and the second metal.

5. The rotor core according to any one of claims 1 to 4, wherein the second metal has a higher density than the first metal.

6. The rotor core according to claim 5 , wherein the first metal is iron and the second metal is copper.

7. a main body formed by stacking a plurality of plates made of a first metal in a rotation axis direction; a through hole extending in the main body in the direction of the rotation axis; a secondary conductor formed of a second metal different from the first metal; A manufacturing method of a rotor core comprising: disposing the secondary conductor inside the through hole; disposing a solution containing carbon between an inner wall of the through hole and the secondary conductor; forming a carbon-based bonding layer by heating the area where the solution is disposed; Equipped with the first metal and the carbon are chemically bonded between an inner wall of the through hole and the bonding layer, The second metal and the carbon are chemically bonded between the secondary conductor and the bonding layer. A manufacturing method of a rotor core.

8. The method for manufacturing a rotor core according to claim 7 , wherein the carbon contained in the solution is composed of simple carbon and has a double bond.

9. The method for manufacturing a rotor core according to claim 8 , wherein the carbon contained in the solution includes fullerene or carbon nanotubes.

10. The method for manufacturing a rotor core according to any one of claims 7 to 9, wherein the region in which the solution is disposed is heated by laser irradiation.

11. The method for manufacturing a rotor core according to any one of claims 7 to 10, wherein the second metal has a higher density than the first metal.

12. The method for manufacturing a rotor core according to claim 11 , wherein the first metal is iron and the second metal is copper.

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