Motor rotor, electric motor, supercharger, and method for manufacturing motor rotor

Abstract

The motor rotor includes a cylindrical permanent magnet disposed around a rotating shaft and a cylindrical guard ring disposed around the permanent magnet, and the permanent magnet and the guard ring are integrally sintered.

Description

Technical Field

[0001] The present disclosure relates to a motor rotor, an electric motor, a supercharger, and a method for manufacturing the motor rotor. Background Art

[0002] A motor described in Patent Document 1 is known. The motor's rotor includes permanent magnets mounted on a shaft and a protective ring surrounding the permanent magnets. When the rotor rotates at high speed and strong centrifugal forces act on the permanent magnets, the protective ring prevents the permanent magnets from detaching from the rotor. The protective ring is fixed to the outer circumference of the permanent magnets by shrink fit.

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 9-275651

[0004] Patent Document 2: Japanese Patent No. 46810081

[0005] However, when shrink-fitting a protective ring onto the outer circumference of a permanent magnet, both the outer circumference of the permanent magnet and the inner circumference of the protective ring must be polished to adjust the surface roughness, and the tolerances of both components must be strictly managed. Therefore, using the above-described method cannot guarantee high productivity of the motor rotor, nor can it guarantee high productivity of the electric motor or supercharger incorporating the motor rotor. Therefore, the present disclosure describes a motor rotor, an electric motor, a supercharger, and a method for manufacturing a motor rotor with high productivity. Summary of the Invention

[0006] A motor rotor according to one embodiment of the present disclosure includes a cylindrical magnet disposed around a rotating shaft and a cylindrical protection ring disposed around the magnet, wherein the magnet and the protection ring are integrally sintered.

[0007] According to the present disclosure, a motor rotor, an electric motor, a supercharger, and a method for manufacturing a motor rotor with high productivity can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a cross-sectional view including the rotation axis of the supercharger of this embodiment.

[0009] Figure 2 It is a cross-sectional view including the rotation axis of the motor rotor according to this embodiment.

[0010] Figure 3 (a) to (c) are diagrams for explaining the manufacturing process of the motor rotor. DETAILED DESCRIPTION

[0011] The gist of the present disclosure lies in the following [1] to [6].

[0012] [1] A motor rotor comprising: a cylindrical magnet disposed around a rotating shaft; and a cylindrical protection ring disposed around the magnet, wherein the magnet and the protection ring are integrally sintered.

[0013] [2] A motor rotor according to [1], wherein the magnet and the protective ring are sintered integrally by sintering a composite molded body formed by overlapping a metal powder molded body formed by metal powder as the material of the magnet with another metal powder molded body as the material of the protective ring.

[0014] [3] The motor rotor according to [1] or [2], wherein the magnet is a samarium cobalt magnet and the material of the protective ring is alloy 718.

[0015] [4] An electric motor comprising the motor rotor described in any one of [1] to [3].

[0016] [5] A supercharger comprising the electric motor described in [4] as an assist electric motor for imparting torque to the rotating shaft of the impeller.

[0017] [6] A method for manufacturing a motor rotor, which is a method for manufacturing a motor rotor as described in any one of [1] to [3], wherein the method comprises the following step: sintering a composite molded body formed by overlapping a metal powder molded body formed by forming another metal powder as the material of the protective ring around the metal powder molded body formed by forming the metal powder of the material of the magnet, thereby sintering the magnet and the protective ring as a whole.

[0018] Embodiments of a motor rotor, an electric motor, a supercharger, and a method for manufacturing a motor rotor according to the present disclosure will be described with reference to the accompanying drawings. Figure 1 This is a cross-sectional view taken along a section including the rotation axis H of the supercharger 1. The supercharger 1 is a variable geometry supercharger equipped with a motor rotor according to an embodiment. In the following description, the terms "axial," "radial," and "circumferential" refer to the axial, radial, and circumferential directions of the rotating shaft 14, described later, respectively.

[0019] The supercharger 1 is used in machines that operate by chemical reactions between fuel and oxygen, such as internal combustion engines in vehicles and fuel cells. The supercharger 1 increases the amount of oxygen involved in the chemical reactions by compressing air and supplying it to these machines. Figure 1As shown, the supercharger 1 includes a turbine 2 and a compressor 3. The turbine 2 includes a turbine housing 4 and a turbine wheel 6 housed in the turbine housing 4. The turbine housing 4 has a scroll flow path 16 extending circumferentially around the turbine wheel 6. The compressor 3 includes a compressor housing 5 and a compressor wheel 7 housed in the compressor housing 5. The compressor housing 5 has a scroll flow path 17 extending circumferentially around the compressor wheel 7.

[0020] The turbine impeller 6 is provided at one end of a rotating shaft 14, and the compressor impeller 7 is provided at the other end of the rotating shaft 14. A bearing housing 13 is provided between the turbine housing 4 and the compressor housing 5. The rotating shaft 14 is rotatably supported by the bearing housing 13 via bearings 15. The rotating shaft 14, the turbine impeller 6, and the compressor impeller 7 rotate about the rotation axis H as a single rotating body 12.

[0021] The turbine housing 4 is provided with an exhaust gas inlet (not shown) and an exhaust gas outlet 10. Exhaust gas from an internal combustion engine (not shown) flows into the turbine housing 4 through the exhaust gas inlet. The exhaust gas then flows into the turbine impeller 6 through the vortex flow path 16, causing the turbine impeller 6 to rotate. The exhaust gas then flows out of the turbine housing 4 through the exhaust gas outlet 10.

[0022] The compressor housing 5 is provided with an intake port 9 and an exhaust port (not shown). As the turbine impeller 6 rotates as described above, the compressor impeller 7 rotates via the rotating shaft 14. The rotating compressor impeller 7 draws in external air through the intake port 9. This air is compressed by the compressor impeller 7 and the vortex flow path 17 and discharged from the exhaust port. The compressed air discharged from the exhaust port is supplied to the internal combustion engine described above.

[0023] In addition, the supercharger 1 is equipped with an electric motor 21. For example, when the torque of the rotating shaft 14 is insufficient, the electric motor 21 applies torque to the rotating shaft 14 to compensate for the deficiency, such as when the vehicle is accelerating. The electric motor 21 is, for example, a brushless AC motor and includes a motor rotor 25 as a rotating part and a motor stator 27 as a fixed part. The vehicle's battery can be used as a driving source for the electric motor 21. In addition, when the vehicle is decelerating, the electric motor 21 can regenerate electricity using the rotational energy of the rotating body 12. The electric motor 21 has characteristics that can cope with high-speed rotation of the rotating shaft 14 (for example, 100,000 to 200,000 rpm).

[0024] The motor rotor 25 is arranged between the bearing 15 and the compressor impeller 7 in the axial direction. The rotating shaft 14 is inserted through the center of the motor rotor 25, and the motor rotor 25 and the compressor impeller 7 are connected by a nut 18 (see FIG. Figure 1 ) is fastened to the rotating shaft 14. Thus, the motor rotor 25 is fixed to the rotating shaft 14 and can rotate together with the rotating shaft 14.

[0025] The motor stator 27 is housed in the bearing housing 13 and is arranged to circumferentially surround the motor rotor 25. The motor stator 27 includes multiple coils and an iron core (not shown). When current is supplied to these coils, the motor stator 27 generates a magnetic field. This magnetic field exerts a circumferential force on the permanent magnets 37 of the motor rotor 25, resulting in torque being applied to the rotating shaft 14.

[0026] Next, refer to Figure 2 as well as Figure 3 、 one The motor rotor 25 and its manufacturing method are further described. Figure 2 As shown, the motor rotor 25 is an assembly including permanent magnets 37, end rings 39, 39, and a protective ring 43. The permanent magnets 37 are cylindrical and disposed around the rotating shaft 14. The protective ring 43 is cylindrical and disposed around the permanent magnets 37. The protective ring 43 prevents radial scattering of fragments of the permanent magnets 37 in the event of damage. Furthermore, the protective ring 43 needs to have a certain degree of rigidity to suppress deformation of the permanent magnets 37 and reduce the possibility of damage. The outer diameter of the pair of annular end rings 39, 39 is substantially the same as the inner diameter of the protective ring 43, and the pair of end rings 39, 39 are arranged so as to sandwich the permanent magnets 37 and the protective ring 43 in the axial direction.

[0027] The permanent magnet 37 is integrally bonded to the protective ring 43 in a manner described below. The end rings 39, 39 are press-fitted into the inner circumferential surface of the protective ring 43 and are also press-fitted into the rotating shaft 14. Due to this joint structure, the torque applied to the permanent magnet 37 by the motor 21 is transmitted from the permanent magnet 37 to the rotating shaft 14 in sequence through the protective ring 43 and the end rings 39, 39. Furthermore, although the permanent magnet 37 is bonded to the rotating shaft 14 with an adhesive, the strength of this joint is relatively weak, only sufficient to withstand polishing of the outer periphery of the permanent magnet 37 during manufacturing, and is not strong enough to directly transmit torque from the permanent magnet 37 to the rotating shaft 14 during high-speed rotation.

[0028] Permanent magnet 37 may be, for example, a neodymium magnet (Nd-Fe-B) or a samarium-cobalt magnet. Guard ring 43 may be made of non-magnetic metals such as Alloy 718 or Ti64 (Ti-6Al-4V). End rings 39, 39 may be made of non-magnetic metals such as SUS, thermosetting resins, or thermoplastic resins.

[0029] In order to reliably transmit torque between the permanent magnets 37 and the protective ring 43 during high-speed rotation of the motor rotor 25, the permanent magnets 37 and the protective ring 43 must be firmly bonded to each other. Therefore, the permanent magnets 37 and the protective ring 43 are firmly bonded to each other by being sintered as a single unit. The method for manufacturing the motor rotor 25 having such permanent magnets 37 and the protective ring 43 includes a sintering step for sintering a compact. The compact is a multi-component compact formed by stacking other metal powder compacts around a metal powder compact. The metal powder compact is formed by molding the metal powder of the material of the permanent magnets 37, and the other metal powder compacts are formed by molding the metal powder of the material of the protective ring 43. A specific example of this manufacturing method is described below.

[0030] First, the metal powder as the material of the permanent magnet 37 is mixed with a predetermined binder, placed in a mold and compressed, thereby Figure 3 As shown in (a), a cylindrical metal powder molded body 51 is formed. In addition, a mixture of metal powder as a material of the protective ring 43 and a predetermined adhesive is arranged around the above-mentioned metal powder molded body 51, and is placed in a mold together with the metal powder molded body 51 and compressed. Figure 3 As shown in (b) of FIG. 5 , the mixture is formed into a metal powder compact 52 . The metal powder compact 52 is formed into a cylindrical shape surrounding the outer peripheral surface of the metal powder compact 51 and in close contact with the outer peripheral surface of the metal powder compact 51 .

[0031] Next, as described above, the composite compact 53 formed by radially overlapping the metal powder compacts 51 and 52 is sintered. Specifically, the composite compact 53 is heated and pressurized while being placed in a mold. Figure 3 As shown in (c), the cylindrical permanent magnet 37 corresponding to the portion of the metal powder compact 51 and the cylindrical protection ring 43 corresponding to the portion of the metal powder compact 52 are sintered together to form an integrated state. Thereafter, the integrated permanent magnet 37 and protection ring 43 are attached to the rotating shaft 14 together with the end rings 39, 39, thereby completing the motor rotor 25 ( Figure 2 ).

[0032] The normal sintering temperature when sintering each metal material is 1040°C for neodymium magnets, 1215°C for samarium-cobalt magnets, 1450°C for Ti64, and 1250°C for alloy 718. Since the composite compact 53 described above includes two of these metal materials, the sintering temperature when sintering the composite compact 53 is the same as the lower temperature of the normal sintering temperatures of the two metal materials, and the sintering is performed for a longer time than the normal sintering time.

[0033] For example, when the permanent magnets 37 of the motor rotor 25 are neodymium magnets and the protection ring 43 is made of Ti64, the sintering temperature of the composite compact 53 is 1040°C, which is the typical sintering temperature for neodymium magnets on the lower temperature side. For example, when the permanent magnets 37 of the motor rotor 25 are neodymium magnets and the protection ring 43 is made of alloy 718, the sintering temperature of the composite compact 53 is 1040°C, which is the typical sintering temperature for neodymium magnets on the lower temperature side. For example, when the permanent magnets 37 of the motor rotor 25 are samarium cobalt magnets and the protection ring 43 is made of Ti64, the sintering temperature of the composite compact 53 is 1215°C, which is the typical sintering temperature for samarium cobalt magnets on the lower temperature side. For example, when the permanent magnets 37 of the motor rotor 25 are samarium cobalt magnets and the guard ring 43 is alloy 718, the sintering temperature of the composite compact 53 is 1215° C., which is the lower temperature of the normal sintering temperature of samarium cobalt magnets.

[0034] The effects of the motor rotor 25 and its manufacturing method according to this embodiment will be described. In the manufacturing method of the motor rotor 25 according to this embodiment, as described above, the permanent magnets 37 and the protection ring 43 are integrally sintered with the metal powder compacts 51 and 52 in a state of close contact. This allows diffusion between the metals at the interface between the metals of the permanent magnets 37 and the metals of the protection ring 43, resulting in a secure bond between the permanent magnets 37 and the protection ring 43 through diffusion bonding. This bonding technique eliminates the need for strict surface roughness adjustment and tolerance management of the bonding surfaces between the permanent magnets 37 and the protection ring 43, compared to shrink-fitting the permanent magnets 37 and the protection ring 43. Consequently, the productivity of the motor rotor 25 is improved. Furthermore, the productivity of the electric motor 21 and the supercharger 1 incorporating this motor rotor 25 is also improved.

[0035] The present disclosure can be implemented in various ways with various changes and improvements based on the knowledge of those skilled in the art, mainly based on the above-mentioned embodiments. In addition, it is also possible to use the technical matters described in the above-mentioned embodiments to constitute a modified example. It is also possible to appropriately combine the structures such as the various embodiments for use.

[0036] Description of Reference Numerals

[0037] 1...supercharger; 14...rotating shaft; 21...electric motor; 25...motor rotor; 37...permanent magnet; 43...protective ring; 51...metal powder compact; 52...metal powder compact; 53...composite compact.

Claims

1. A motor rotor, characterized in that: The invention comprises: a cylindrical magnet arranged around a rotating shaft, and a cylindrical protection ring arranged around the magnet. The magnet and the protection ring are sintered integrally.

2. The motor rotor according to claim 1, wherein: The magnet and the guard ring are integrally sintered by sintering a composite compact formed by overlapping another metal powder compact formed by forming another metal powder as the material of the guard ring around the metal powder compact formed by forming the metal powder of the magnet.

3. The motor rotor according to claim 1, wherein: The magnet is a samarium cobalt magnet, and the material of the protection ring is alloy 718.

4. An electric motor, characterized in that: A motor rotor according to any one of claims 1 to 3 is provided.

5. A supercharger, characterized in that: As an assist motor for applying torque to the rotating shaft of the impeller, the motor according to claim 4 is provided.

6. A method for manufacturing a motor rotor, comprising manufacturing the motor rotor according to claim 1, wherein: With the following processes: The magnet and the guard ring are integrally sintered by sintering a composite compact formed by overlapping another metal powder compact formed by forming another metal powder as the material of the guard ring around the metal powder compact formed by forming the metal powder of the magnet.

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