electric motor

Abstract

To provide an electric motor that can cool the stator core using the magnetic caloric effect while suppressing an increase in physical size. [Solution] The electric motor comprises a hollow stator core, a plurality of coils provided on the stator core and arranged along the circumferential direction of the stator core, a rotor extending along the axial direction of the stator core within the hollow of the stator core, and a cooling system having a plurality of refrigerant passages located in the yoke portion of the stator core. The plurality of refrigerant passages are distributed along the circumferential direction of the stator core. The cooling system controls the flow rate of refrigerant flowing through each of the plurality of refrigerant passages based on the rotation angle of the rotor.

Description

Technical Field

[0001] The technology disclosed in this specification relates to an electric motor.

Background Art

[0002] An electric motor includes a hollow stator core, a plurality of coils provided in the stator core and arranged along the circumferential direction of the stator core, and a rotor extending along the axial direction of the stator core within the hollow of the stator core.

[0003] Patent Document 1 discloses an electric motor further including a blower fan that blows air toward one end face of the stator core, and a magnetic cooling means disposed between the stator core and the blower fan. The magnetic cooling means includes a permanent magnet, a magnetocaloric effect material, and a moving mechanism that moves the magnetocaloric effect material between a position where a magnetic field is applied by the permanent magnet and a position where no magnetic field is applied. The magnetocaloric effect material is a material that generates heat when excited and absorbs heat when demagnetized, and is a material whose temperature changes with a change in magnetic field. In the technology of Patent Document 1, the magnetocaloric effect material that has moved to the position where the magnetic field is applied generates heat, and the heat is exhausted. As a result, the temperature of the magnetocaloric effect material that has moved to the position where no magnetic field is applied is lower than the ambient temperature. The position where no magnetic field is applied is located in the air blowing path of the blower fan. As a result, the air cooled by the magnetocaloric effect material is blown onto the stator core.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The technology described in Patent Document 1 requires space to install permanent magnets for generating a magnetic field. Furthermore, the technology described in Patent Document 1 also requires space to install a moving mechanism for moving the magnetocaloric material between a position where a magnetic field is applied and a position where it is not. For this reason, the electric motor described in Patent Document 1 has the problem of being large in size. This specification provides an electric motor that can cool the stator core by the magnetocaloric effect while suppressing the increase in size. [Means for solving the problem]

[0006] The electric motor disclosed herein may comprise a hollow stator core, a plurality of coils provided on the stator core and arranged along the circumferential direction of the stator core, a rotor extending along the axial direction of the stator core within the hollow of the stator core, and a cooling system having a plurality of refrigerant passages located in the yoke portion of the stator core. The plurality of refrigerant passages may be distributed along the circumferential direction of the stator core. The cooling system may control the flow rate of refrigerant flowing through each of the plurality of refrigerant passages based on the rotation angle of the rotor.

[0007] Magnetic flux, associated with the rotating magnetic field, passes through the yoke portion of the stator core. The magnetic flux passing through any point in the yoke portion varies based on the rotation angle of the rotating magnetic field, i.e., the rotation angle of the rotor. Therefore, at any point in the yoke portion, there are times when magnetic flux passes through and times when it does not, based on the rotation angle of the rotor. The yoke portion is made of a magnetic material and has a magnetocaloric effect. Therefore, at any point in the yoke portion, heat is generated when magnetic flux passes through and heat is absorbed when magnetic flux does not pass through. In the above-described electric motor, multiple refrigerant passages located in the yoke portion are distributed along the circumferential direction of the stator core. Therefore, in the above-described electric motor, when the rotor rotates, there are times when magnetic flux passes through parts of the yoke portion where some of the multiple refrigerant passages are located, and times when magnetic flux does not pass through parts of the yoke portion where other refrigerant passages are located. The cooling system of the above-described electric motor can efficiently cool the stator core while maintaining the refrigerant flow rate of the cooling system by, for example, making the flow rate of the refrigerant in the yoke section, which generates heat due to the passage of magnetic flux, greater than the flow rate of the refrigerant in the yoke section, which absorbs heat because magnetic flux does not pass through it. In this way, the above-described electric motor can cool the stator core by utilizing the magnetocaloric effect of the yoke section by controlling the flow rate of the refrigerant flowing through each of the multiple refrigerant flow paths based on the rotation angle of the rotor. The above-described electric motor does not require permanent magnets or moving mechanisms like the electric motor in Patent Document 1. The above-described electric motor can cool the stator core by utilizing the magnetocaloric effect while suppressing an increase in size. [Brief explanation of the drawing]

[0008] [Figure 1] This diagram schematically illustrates the configuration of the electric motor of this embodiment as viewed from the direction of the rotation axis. [Figure 2] This diagram schematically illustrates the configuration of the cooling system in this embodiment. [Figure 3] This diagram illustrates the rotating magnetic field generated by the electric motor of this embodiment and the magnetic flux associated with that rotating magnetic field. [Figure 4]This figure illustrates the rotating magnetic field generated by the electric motor of this embodiment and the magnetic flux associated with that rotating magnetic field, and shows the case when the rotor rotation angle is different from that of Figure 3. [Figure 5] This figure schematically illustrates the configuration of a valve plate in an electric motor of a modified example of this embodiment. [Figure 6] This figure schematically illustrates the configuration of the valve plate in an electric motor of a modified example of this embodiment, and shows a case where the position of the valve plate is different from that in Figure 5. [Modes for carrying out the invention]

[0009] The technologies disclosed herein will be described below with reference to a three-phase synchronous motor. The technologies disclosed herein are also broadly applicable to other types of motors.

[0010] As shown in Figure 1, the electric motor 1 comprises a stator core 10, a plurality of coils 20a, 20b, 20c, a rotor 30, and a plurality of refrigerant passages 42a, 42b, 42c.

[0011] The stator core 10 has a hollow cylindrical yoke portion 12 and a plurality of teeth 14 extending radially inward from the inner circumferential surface of the yoke portion 12. A rotor 30 is inserted into the central hole of the yoke portion 12. The rotor 30 is positioned in the central hole of the stator core 10 such that its central axis coincides with the central axis AX (i.e., the axis of rotation) of the stator core 10. Hereinafter, the direction parallel to the central axis AX will be referred to as the axial direction, and the direction along the circle centered on the central axis AX will be referred to as the circumferential direction.

[0012] Each of the multiple teeth 14 extends axially from one end face to the other of the yoke portion 12 and is arranged circumferentially at 120-degree intervals from one another. The yoke portion 12 and teeth 14, excluding the multiple magnetocaloric effect material portions 16a, 16b, and 16c described later, are formed by laminating multiple electromagnetic steel sheets in the axial direction.

[0013] Each of the coils 20a, 20b, and 20c is positioned corresponding to one of the teeth 14 and is wound around that corresponding tooth 14. As a result, the coils 20a, 20b, and 20c are also positioned at 120-degree intervals in the circumferential direction. AC currents with phase differences of 120 degrees are passed through the coils 20a, 20b, and 20c. For example, the first coil 20a is supplied with an AC current corresponding to the U phase, the second coil 20b is supplied with an AC current corresponding to the V phase, and the third coil 20c is supplied with an AC current corresponding to the W phase.

[0014] The yoke portion 12 has a plurality of magnetocaloric effect material portions 16a, 16b, and 16c. The magnetocaloric effect material constituting the plurality of magnetocaloric effect material portions 16a, 16b, and 16c is the magnetic material of the yoke portion 12 other than the plurality of magnetocaloric effect material portions 16a, 16b, and 16c, i.e., a material with a larger change in magnetic entropy than the electromagnetic steel sheet. The magnetocaloric effect material is not particularly limited, but may be, for example, an alloy containing gadolinium or an alloy containing manganese.

[0015] Multiple magnetocaloric effect material sections 16a, 16b, and 16c are arranged in a dispersed manner along the circumferential direction. In this example, the first magnetocaloric effect material section 16a is positioned between the first coil 20a and the second coil 20b, the second magnetocaloric effect material section 16b is positioned between the second coil 20b and the third coil 20c, and the third magnetocaloric effect material section 16c is positioned between the third coil 20c and the first coil 20a.

[0016] Each of the multiple magnetocaloric effect material sections 16a, 16b, and 16c extends between the inner and outer surfaces of the yoke section 12 when viewed in a cross-section perpendicular to the axial direction, and divides the yoke section 12 other than the magnetocaloric effect material along the circumferential direction. Alternatively, each of the multiple magnetocaloric effect material sections 16a, 16b, and 16c may be positioned in a part between the inner and outer surfaces of the yoke section 12. Also, each of the multiple magnetocaloric effect material sections 16a, 16b, and 16c extends along the axial direction from one end face to the other end face of the yoke section 12 when viewed in a cross-section parallel to the axial direction. Alternatively, each of the multiple magnetocaloric effect material sections 16a, 16b, and 16c may be positioned in a part between one end face and the other end face of the yoke section 12. Thus, each of the multiple magnetocaloric effect material parts 16a, 16b, and 16c can be arranged in various ways, as long as they are dispersed along the circumferential direction.

[0017] Multiple refrigerant channels 42a, 42b, and 42c are provided in the yoke portion 12 and are distributed along the circumferential direction. Each of the multiple refrigerant channels 42a, 42b, and 42c corresponds to one of the multiple magnetocaloric effect material portions 16a, 16b, and 16c, and is positioned in contact with the corresponding magnetocaloric effect material portion. More specifically, each of the multiple refrigerant channels 42a, 42b, and 42c extends along the axial direction from one end face of the yoke portion 12 to the other end face, penetrating the corresponding magnetocaloric effect material portion. In this example, the first refrigerant channel 42a extends through the first magnetocaloric effect material portion 16a, the second refrigerant channel 42b extends through the second magnetocaloric effect material portion 16b, and the third refrigerant channel 42c extends through the third magnetocaloric effect material portion 16c.

[0018] Figure 2 schematically shows the configuration of the cooling system 40. The cooling system 40 has an input flow path 41, a plurality of refrigerant flow paths 42a, 42b, 42c, a plurality of electromagnetic valves 44a, 44b, 44c, and a valve control device 46. The plurality of refrigerant flow paths 42a, 42b, 42c are flow paths connected in parallel on the downstream side of the input flow path 41. Each of the plurality of electromagnetic valves 44a, 44b, 44c is arranged corresponding to one of the plurality of refrigerant flow paths 42a, 42b, 42c. In this example, the first electromagnetic valve 44a is arranged in the first refrigerant flow path 42a, the second electromagnetic valve 44b is arranged in the second refrigerant flow path 42b, and the third electromagnetic valve 44c is arranged in the third refrigerant flow path 42c. The valve control device 46 controls the valve opening degrees of the plurality of electromagnetic valves 44a, 44b, 44c based on the rotation angle of the rotor 30, as will be described later.

[0019] Lubricating oil is supplied as the refrigerant to the input flow path 41. The lubricating oil is sucked from a storage portion provided at the bottom of the case that houses the electric motor 1 by a pump or the like, cooled by a heat exchanger or the like, and then supplied to the input flow path 41. The lubricating oil flowing through each of the plurality of refrigerant flow paths 42a, 42b, 42c is discharged from the discharge ports 48a, 48b, 48c after exchanging heat with the corresponding magnetocaloric effect material portion. Each of the plurality of refrigerant flow paths 42a, 42b, 42c may have separate discharge ports or may have a common discharge port. The lubricating oil discharged from the discharge ports 48a, 48b, 48c of the plurality of refrigerant flow paths 42a, 42b, 42c may be discharged toward, for example, a lubrication target portion or a cooling target portion of the electric motor 1. An example of the cooling target portion is not particularly limited, but may be, for example, the end coils of the plurality of coils 20a, 20b, 20c.

[0020] Figures 3 and 4 show the rotating magnetic field when the rotation angle of the rotor 30 is different and the magnetic flux passing through the stator core 10 along with the rotating magnetic field. The rotating magnetic field is indicated by a dashed arrow, and the magnetic flux is indicated by a solid arrow.

[0021] The timing shown in FIG. 3 is the timing when the rotating magnetic field is directed from the central axis AX to the first coil 20a. At this time, the magnetic flux associated with the rotating magnetic field passes through the first magnetocaloric effect material portion 16a and the third magnetocaloric effect material portion 16c of the yoke portion 12, and does not pass through the second magnetocaloric effect material portion 16b. The timing shown in FIG. 4 is the timing when the rotating magnetic field is directed from the central axis AX to the third coil 20c. At this time, the magnetic flux associated with the rotating magnetic field passes through the second magnetocaloric effect material portion 16b and the third magnetocaloric effect material portion 16c of the yoke portion 12, and does not pass through the first magnetocaloric effect material portion 16a.

[0022] The valve control device 46 of the cooling system 40 controls to increase the valve opening degrees of the first solenoid valve 44a and the third solenoid valve 44c and decrease the valve opening degree of the second solenoid valve 44b at the timing shown in FIG. 3. Note that the valve opening degree of the second solenoid valve 44b may be controlled to be zero, that is, the second solenoid valve 44b may be completely closed. Thereby, the flow rate of the lubricating oil flowing through the first refrigerant flow path 42a and the third refrigerant flow path 42c becomes larger than the flow rate of the lubricating oil flowing through the second refrigerant flow path 42b. On the other hand, the valve control device 46 of the cooling system 40 controls to increase the valve opening degrees of the second solenoid valve 44b and the third solenoid valve 44c and decrease the valve opening degree of the first solenoid valve 44a at the timing shown in FIG. 4. Note that the valve opening degree of the first solenoid valve 44a may be controlled to be zero, that is, the first solenoid valve 44a may be completely closed. Thereby, the flow rate of the lubricating oil flowing through the second refrigerant flow path 42b and the third refrigerant flow path 42c becomes larger than the flow rate of the lubricating oil flowing through the first refrigerant flow path 42a.

[0023] Thus, the valve control device 46 of the cooling system 40 controls the flow rate of the refrigerant flow path corresponding to the magnetocaloric effect element portion through which the magnetic flux passes to be larger than the flow rate of the refrigerant flow path corresponding to the magnetocaloric effect element portion through which the magnetic flux does not pass. Note that the valve control device 46 may control the valve opening degrees of the plurality of solenoid valves 44a, 44b, 44c based on, for example, the phases of the currents flowing through the plurality of coils 20a, 20b, 20c, that is, the phases of the three-phase alternating current. More specifically, the valve control device 46 may control the valve opening degrees of the plurality of solenoid valves 44a, 44b, 44c based on the control signal of the inverter for generating the three-phase alternating current.

[0024] The magnetocaloric effect materials constituting the multiple magnetocaloric effect material sections 16a, 16b, and 16c generate heat when a magnetic field is applied due to a decrease in magnetic entropy, and absorb heat when no magnetic field is applied due to an increase in magnetic entropy. In other words, the cooling system 40 controls the flow rate of the refrigerant channel corresponding to the magnetocaloric effect element section in the heat-generating state to be greater than the flow rate of the refrigerant channel corresponding to the magnetocaloric effect element section in the heat-absorbing state. As a result, the flow rate of the refrigerant channel with high heat dissipation efficiency is controlled to be greater than the flow rate of the refrigerant with low heat dissipation efficiency. As a result, the stator core 10 is efficiently cooled while maintaining the flow rate of lubricating oil flowing through the cooling system 40.

[0025] The electric motor 1 is an example of actively utilizing the magnetocaloric effect by arranging multiple magnetocaloric effect material parts 16a, 16b, and 16c in the yoke section 12. Alternatively, the multiple magnetocaloric effect material parts 16a, 16b, and 16c may not be arranged in the yoke section 12. In this case, the stator core 10 can be cooled by the same mechanism as described above by utilizing the magnetocaloric effect of the electromagnetic steel sheet of the yoke section 12.

[0026] The valve control device 46 may determine whether or not to perform valve opening control of the plurality of solenoid valves 44a, 44b, and 44c based on the rotational speed of the rotor 30. For example, when the rotational speed of the rotor 30 is less than or equal to a predetermined value, the valve control device 46 may perform control to increase or decrease the valve opening of the plurality of solenoid valves 44a, 44b, and 44c based on the rotation angle of the rotor 30, and when the rotational speed of the rotor 30 is greater than a predetermined value, it may perform control to keep the valve opening of the plurality of solenoid valves 44a, 44b, and 44c constant, regardless of the rotation angle of the rotor 30.

[0027] When the rotational speed of the rotor 30 exceeds a predetermined value, it becomes difficult to increase or decrease the refrigerant flow rate in accordance with the rotation angle of the rotor 30, even if control is performed to increase or decrease the valve opening. For this reason, when the rotational speed of the rotor 30 exceeds a predetermined value, the valve openings of the multiple solenoid valves 44a, 44b, and 44c are controlled to a constant value. Even in this case, because the heat dissipation effect when the magnetocaloric effect material part generates heat is large, the stator core 10 can be cooled more efficiently than in the case where the magnetocaloric effect material part is not provided.

[0028] On the other hand, when the rotational speed of the rotor 30 is below a predetermined value, control is performed to increase or decrease the valve opening of the multiple solenoid valves 44a, 44b, and 44c, allowing the refrigerant flow rate to be significantly increased or decreased in accordance with the timing of heat generation and heat absorption in the magnetocaloric effect material. As a result, the magnetocaloric effect of the magnetocaloric effect material can be actively utilized, and the stator core 10 is cooled more efficiently.

[0029] The cooling system 40 described above is an example of controlling the refrigerant flow rate using a plurality of solenoid valves 44a, 44b, and 44c. Alternatively, the cooling system 40 may control the refrigerant flow rate using a mechanical mechanism. Figures 5 and 6 show an example of controlling the refrigerant flow rate using a valve plate 50 connected to the rotor 30. The valve plate 50 is fixed to a flange (not shown) extending radially from the rotor 30 and is configured to rotate around the central axis AX of the stator core 10 as the rotor 30 rotates. The valve plate 50 has a predetermined shape and is configured to close the refrigerant flow path corresponding to the magnetocaloric effect element in an endothermic state and open the refrigerant flow path corresponding to the magnetocaloric effect element in an exothermic state by rotating around the central axis AX of the stator core 10. The valve plate 50 is not particularly limited, but for example, it may be positioned outside the end face of the stator core 10 in the axial direction and configured to open and close the outlets 48a, 48b, and 48c of a plurality of refrigerant flow paths 42a, 42b, and 42c. Such a mechanical mechanism does not require multiple solenoid valves 44a, 44b, 44c and valve control device 46, and can be manufactured at low cost.

[0030] The embodiments disclosed herein are summarized below. Note that the technical elements described below are independent technical elements that exhibit technical usefulness individually or in various combinations.

[0031] (Aspect 1) An electric motor comprising: a hollow stator core; a plurality of coils provided on the stator core and arranged along the circumferential direction of the stator core; a rotor extending along the axial direction of the stator core within the hollow of the stator core; and a cooling system having a plurality of refrigerant passages arranged in the yoke portion of the stator core, wherein the plurality of refrigerant passages are distributed along the circumferential direction of the stator core, and the cooling system controls the flow rate of refrigerant flowing through each of the plurality of refrigerant passages based on the rotation angle of the rotor.

[0032] (Aspect 2) The electric motor according to embodiment 1, wherein the yoke portion of the stator core has a plurality of magnetocaloric effect material portions dispersed along the circumferential direction of the stator core, the plurality of magnetocaloric effect material portions are made of a material that exhibits a larger change in magnetic entropy than the magnetic material of the rest of the yoke portion, and each of the plurality of refrigerant flow paths is arranged to correspond to one of the plurality of magnetocaloric effect material portions.

[0033] (Aspect 3) The electric motor according to embodiment 2, wherein each of the plurality of refrigerant flow paths extends through the yoke portion along the axial direction of the stator core and is in contact with the corresponding magnetocaloric effect material portion.

[0034] (Aspect 4) The electric motor according to any one of embodiments 1 to 3, wherein the cooling system has a plurality of solenoid valves, each of the plurality of solenoid valves is provided corresponding to one of the plurality of refrigerant flow paths, and the cooling system controls the valve opening of each of the plurality of solenoid valves based on the rotation angle of the rotor.

[0035] (Aspect 5) The electric motor according to embodiment 4, wherein the cooling system controls the valve opening of each of the plurality of solenoid valves based on the rotation angle of the rotor when the rotation speed of the rotor is less than or equal to a predetermined value.

[0036] (Aspect 6) The electric motor according to any one of embodiments 1 to 3, wherein the cooling system has a valve plate connected to the rotor, and the valve plate is configured to rotate around the axis of the stator core in conjunction with the rotation of the rotor, thereby closing some of the multiple refrigerant passages and opening other refrigerant passages.

[0037] Although embodiments have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above. The technical elements described in this specification or drawings exhibit technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technologies illustrated in this specification or drawings achieve multiple objectives simultaneously, and achieving even one of these objectives constitutes technical usefulness in itself. [Explanation of symbols]

[0038] 1: Electric motor, 10: Stator core, 12: Yoke section, 14: Teeth, 16a, 16b, 16c: Magnetic caloric effect material section, 20a, 20b, 20c: Coil, 30: Rotor, 42a, 42b, 42c: Coolant flow path

Claims

1. A hollow stator core, A plurality of coils provided on the stator core and arranged along the circumferential direction of the stator core, A rotor extending along the axial direction of the stator core is located within the hollow of the stator core. The cooling system comprises a plurality of refrigerant flow paths arranged in the yoke portion of the stator core, The plurality of refrigerant flow paths are arranged in a dispersed manner along the circumferential direction of the stator core. The cooling system comprises an electric motor that controls the flow rate of refrigerant flowing through each of the plurality of refrigerant passages based on the rotation angle of the rotor.

2. The yoke portion of the stator core has a plurality of magnetocaloric material portions that are dispersed along the circumferential direction of the stator core, The plurality of magnetocaloric effect material parts are made of materials that exhibit a larger change in magnetic entropy than the other magnetic materials in the yoke part. The electric motor according to claim 1, wherein each of the plurality of refrigerant flow paths is arranged to correspond to one of the plurality of magnetocaloric effect material sections.

3. The electric motor according to claim 2, wherein each of the plurality of refrigerant flow paths extends through the yoke portion along the axial direction of the stator core and is in contact with the corresponding magnetocaloric effect material portion.

4. The cooling system has a plurality of solenoid valves, Each of the plurality of solenoid valves is provided in correspondence to one of the plurality of refrigerant flow paths, The electric motor according to any one of claims 1 to 3, wherein the cooling system controls the valve opening of each of the plurality of solenoid valves based on the rotation angle of the rotor.

5. The electric motor according to claim 4, wherein the cooling system controls the valve opening of each of the plurality of solenoid valves based on the rotation angle of the rotor when the rotation speed of the rotor is less than or equal to a predetermined value.

6. The cooling system has a valve plate connected to the rotor, The electric motor according to any one of claims 1 to 3, wherein the valve plate is configured to rotate around the axis of the stator core in conjunction with the rotation of the rotor, thereby closing some of the plurality of refrigerant passages and opening other refrigerant passages.

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