Stator with cooling structure, and electric motor

Abstract

Provided are a stator with which increase in size due to an inlet and outlet for a refrigerant is suppressed while efficient cooling by the refrigerant is enabled, and an electric motor that includes the stator. This stator includes: a coil; a core including a slot in which the coil is disposed and a flow passage for a refrigerant; a mold resin part in which an axial end part of the coil is at least partially embedded; and an introduction port and a lead-out port that are formed in a coil end axial direction section between an axial end surface of the core and an axial tip end of the axial end part of the coil, are open on a lateral surface of the core where the slot is not formed, and are in fluid communication with the flow passage.

Description

Stator and motor with cooling structure

[0001] The present disclosure relates to a stator having a cooling structure and an electric motor having the stator.

[0002] In an electric motor having a stator around which a coil is wound and a rotor that rotates relative to the stator, a flow path for a coolant may be formed in the stator to remove heat generated by energizing the coil, etc. (See, for example, Patent Documents 1 to 3.

[0003] Also known is a motor that includes a molded resin part that molds a plurality of laminated plates and coils that make up the stator, and that has a flow path for a cooling medium formed in the molded resin part (see, for example, Patent Document 4).

[0004] JP-T-2018-504881 A JP-A-10-051983 A JP-A-2008-312292 A JP-A-2023-166527 A

[0005] In a liquid-cooled electric motor that is cooled using a refrigerant, it is necessary to provide an inlet / outlet for introducing and discharging the refrigerant on or near the stator, but providing an inlet / outlet can increase the size of the electric motor, particularly its axial dimension. Therefore, a stator that enables efficient cooling by the refrigerant while suppressing the increase in size due to the inlet / outlet for the refrigerant, and an electric motor having such a stator are desired.

[0006] One aspect of the present disclosure is a stator comprising a coil, a core having a slot in which the coil is arranged and a flow path for a refrigerant, a molded resin portion that at least partially embeds the axial end of the coil, and an inlet and an outlet formed within the coil end axial section between the axial end face of the core and the axial tip of the axial end of the coil, opening on a side of the core where the slot is not formed and fluidly communicating with the flow path.

[0007] Another aspect of the present disclosure is an electric motor including the stator described above and a rotor configured to be rotatable relative to the stator.

[0008] 1. A schematic axial cross-sectional view of an electric motor having a stator according to a first embodiment. A radial cross-sectional view taken along line II-II in FIG. 1. A schematic axial cross-sectional view of a stator according to a second embodiment. An enlarged view of a main portion of the stator according to the first embodiment. An enlarged view of a main portion of the stator according to the second embodiment. An enlarged view of a main portion of a stator according to a comparative example. A radial cross-sectional view taken along line VII-VII in FIG. 4. A radial cross-sectional view showing one configuration example of a cooling channel. A radial cross-sectional view showing another configuration example of a cooling channel. A radial cross-sectional view showing yet ... schematic axial cross-sectional view showing an example in which recesses are formed in a molded resin. A schematic radial cross-sectional view showing an example in which protrusions are formed in a molded resin. A schematic radial cross-sectional view showing an example in which a stator has a divided structure. A schematic axial cross-sectional view showing an example in which a stator is formed from a plurality of electromagnetic steel plates. A schematic axial cross-sectional view showing an example in which the inner surface of an iron core is covered with resin. A schematic axial cross-sectional view showing one configuration example of an outer rotor type electric motor.

[0009] Fig. 1 is an axial cross-sectional view showing a schematic configuration of a main part of an electric motor 2 according to a first embodiment, and Fig. 2 is a radial cross-sectional view taken along line II-II in Fig. 1. The electric motor 2 can be used as a drive source for industrial robots and machine tools, for example, and has a stator 4 and a rotor 8 that rotates about an axis 6 relative to the stator 4. The electric motor 2 according to the first embodiment is a so-called inner rotor type electric motor in which the rotor 8 is disposed radially inward of the stator 4, but is not limited to this.

[0010] The stator 4 has a coil 10 made of a winding, a substantially cylindrical core (iron core) 16 having slots 12 in which the coil 10 is arranged, and at least one refrigerant flow path 14. The core 16 can be formed, for example, by stacking multiple electromagnetic steel sheets. In the illustrated example, multiple flow paths 14 are provided at the same angular positions as the coils 10, and each flow path 14 extends linearly in the axial direction within the core 16. The core 16 is accommodated in a housing 22, and molded resin portions 20 are formed at both axial ends of the core 16. The molded resin portions 20 at least partially embed (in the illustrated example, the entire coil end 18) axial ends 18 of the coil 10 protruding from the core 16 in the axial direction and at least partially fill the slots 12.

[0011] Although there are no particular restrictions on the material for forming the molded resin portion 20, a material having electrical insulation and high heat conductivity, such as epoxy resin, is preferred. The molded resin portion 20, in cooperation with the axial end face of the core 16, defines an inlet 24 for introducing a refrigerant into the flow passage 14 extending axially within the core 16 and an outlet 26 for discharging the refrigerant from the flow passage 14. The inlet 24 and the outlet 26 are formed in an axial section L1 (hereinafter also referred to as the coil end axial section) between the axial tip of the coil end 18 and the axial end face 32 of the core 16, and open on one of the side surfaces (outer surface and inner surface) of the substantially cylindrical core 16 where the slots 12 are not formed (i.e., where the coils 10 adjacent to the rotor 8 are not arranged) (the outer surface in the example of FIGS. 1-2 ).

[0012] 3 is an axial cross-sectional view showing a schematic configuration of a main part of an electric motor 2a according to a second embodiment. The second embodiment differs from the first embodiment in that the shape of the coil end 18a is different from that of the coil end 18 of the first embodiment. However, other parts may be the same as those of the first embodiment. Therefore, corresponding components are given the same reference numerals as those of the first embodiment, and detailed description thereof will be omitted.

[0013] 4 and 5 are enlarged views of the axial end portions of the electric motor 2 according to the first and second embodiments, respectively. As shown in FIG. 4 , in the first embodiment, the radial shortest distance d1 of the flow passage 14 is longer than the radial longest distance d2 of the coil end 18. However, as shown in FIG. 5 , in the second embodiment, the radial shortest distance d1 of the flow passage 14 is shorter than the radial longest distance d3 of the coil end 18a. In other words, the coil end 18a protrudes radially toward the inlet 24 or outlet 26 from the portion of the flow passage 14 farthest from the inlet 24 or outlet 26. More specifically, the coil end 18a protrudes radially outward from the radially innermost portion of the flow passage 14. Generally, coil ends are compressed axially during the manufacture of the electric motor, and therefore have a shape that expands radially outward. Therefore, in the second embodiment, the coil end axial section L2 can be shorter than the coil end axial section L1 in the first embodiment, thereby shortening the overall length of the electric motor. Furthermore, in the second embodiment, the coil ends 18a can be placed closer to the inlet 24, so that the coil ends 18a, which are also heat sources, can be cooled efficiently.

[0014] 6 is an enlarged view of the axial end of a stator 104 according to a comparative example. The stator 104 has a coil 110 made of a winding and a substantially cylindrical core 116 having a refrigerant flow path 114. The core 116 is housed in a housing 122, and molded resin portions 120 are formed at both axial ends of the core 116 to embed coil ends 118 of the coil 10 that protrude axially from the core 116.

[0015] The flow passages 114 are formed radially inward of the coils 110 and open to the axial end face of the core 116, rather than to the outer or inner surface thereof. However, in such a structure, the axial length of the molded resin portion 120 is inevitably much longer than the coil end axial section L3, and as a result, the overall length of the stator 104 is also longer.

[0016] In contrast, in the first and second embodiments, by forming the inlet 24 and outlet 26 within the coil end axial section L1 or L2, the overall length of the stator 4 can be made approximately the same as or slightly longer than the axial length of the coil 10.

[0017] In the comparative example, the flow passage 114 is located radially inward of the coil 110, and in this positional relationship, it may be necessary to reduce the volume of the coil 110 in accordance with the volume occupied by the flow passage 114. Also, since the flow passage 114 is close to the coil 110, it is relatively easy to cool the coil 110, but it is difficult to efficiently cool the radially outer side of the core 116. Furthermore, there are significant dimensional restrictions on the radially inner side of the stator, making it difficult to form a flow passage with a relatively large radial cross-sectional area.

[0018] On the other hand, in the first and second embodiments, the flow passages 14 are disposed radially outward from the coil 10, so there is little need to reduce the volume of the coil 10 by forming the flow passages 14, and the flow passages 14 can be located close to both the radially outer sides of the coil 10 and the core 16, so it is possible to efficiently cool both the coil 10 and the core 16. Furthermore, the flow passages 14 are less subject to dimensional constraints, and it is possible to easily form flow passages with a relatively large radial cross-sectional area, which also contributes to efficient cooling.

[0019] Figure 7 is a cross-sectional view taken along line VII-VII in Figure 4. The stator 4 is defined by the axial end face of the core 16 and the molded resin part 20, and has an annular refrigerant flow path 30 that is fluidly connected to the inlet 24 or the outlet 26, and the refrigerant flow path 30 is fluidly connected to each of the multiple linear flow paths 14. By forming the annular refrigerant flow path 30, only one inlet 24 and one outlet 26 are required, and the refrigerant can flow evenly within each flow path 14.

[0020] 8 to 12 show various shapes and arrangements of refrigerant flow paths in the core 16. In the example of FIG. 8, flow paths 14a, each having a circular radial cross section, are arranged at the same angular position in the circumferential direction as the slots 12. More specifically, the flow paths 14a are formed radially outward from the slots 12, and are arranged so that the centers of the flow paths 14a are located on line segments 17 that represent the circumferential angular positions of the slots 12. Because the flow paths 14a are formed relatively close to the coils 10, which are also heat sources, the coils 10 can be efficiently cooled by the refrigerant flowing through the flow paths 14a.

[0021] In the example of Fig. 9, the arrangement of the flow paths 14 is similar to that of the flow paths 14a, but the radial cross-sectional shape of each flow path 14 is an ellipse that is long in the circumferential direction. In this way, the distance from the radial outside of the flow path 14 to the outer surface of the core 16 can be made longer than in the example of Fig. 8, and the circumferential magnetic flux is less likely to be blocked, thereby suppressing a decrease in torque of the electric motor.

[0022] In the example of Fig. 10, the arrangement of the flow paths 14b is similar to that of the flow paths 14a or 14, but the radial cross-sectional shape of each flow path 14b is a substantially triangular shape with an apex at the same circumferential angular position as the center of the slot 12 (more specifically, the apex is located on the line segment 17 that represents the angular position of the center of the slot 12). In the example of Fig. 10, as in the example of Fig. 9, the circumferential magnetic flux is less likely to be blocked, so that a decrease in torque of the electric motor can be suppressed. In addition, compared to the example of Fig. 9, the radial distance between the radially inner wall surface of the flow path 14b and the coil 10 can be reduced, so that the core 16 and the coil 10 can be cooled efficiently.

[0023] 11, in addition to the flow passage 14a shown in FIG. 8, the core 16 has an outer surface formed with a groove 15a extending in the axial direction, which defines a flow passage for the coolant in cooperation with the housing 22. To prevent the circumferential magnetic flux from being blocked, the groove 15a is preferably formed so that its center is located between the angular positions of adjacent slots 12, in other words, on a line segment 19 representing the angular position of the center of the teeth 13. In the example of FIG. 11, the two types of flow passages 14a, 15a allow a large amount of coolant to flow, which not only enables the core 16 to be cooled efficiently but also suppresses a decrease in torque of the electric motor.

[0024] In the example of Fig. 12, the arrangement of the flow paths is the same as in Fig. 11, but the flow path at the same angular position as the slot 12 is the elliptical flow path 14a shown in Fig. 9, and the flow path defined by the outer surface of the core 16 and the housing 22 has a substantially semi-elliptical shape that is long in the circumferential direction, rather than a substantially semicircular shape like the groove 15a in Fig. 10. In the example of Fig. 12, the magnetic flux in the circumferential direction is even less likely to be blocked than in the example of Fig. 11, so that the decrease in torque of the electric motor can be significantly suppressed.

[0025] FIG. 13 is an enlarged view of the axial end of an electric motor 2b according to the third embodiment, and parts that may be similar to those in the first embodiment are given the same reference numerals as in the first embodiment, and detailed descriptions thereof will be omitted.

[0026] For example, in the example shown in Fig. 5, depending on the conditions (pressure, flow rate, etc.) of the refrigerant introduced through the inlet 24, stress may concentrate at a boundary 32 between the axial end face of the core 16 and the molded resin portion 20, which may cause local deterioration of the core 16 or the molded resin portion 20 near the boundary 32 or cause refrigerant leakage from the boundary 32. In contrast, in the example shown in Fig. 13, the molded resin portion 20a has a recess 34 that is recessed radially toward the coil 10 relative to the portion of the flow path 14 farthest from the inlet 24a or the outlet in the radial direction. More specifically, the molded resin portion 20a has a recess 34 that is recessed radially inward relative to the radially innermost portion of the flow path 14. Therefore, in the example shown in Fig. 13, stress concentration at the boundary 32 is alleviated, making it possible to suppress local deterioration and refrigerant leakage.

[0027] Fig. 14 is a radial cross-sectional view showing the annular flow path 30, similar to Fig. 7. In the example of Fig. 14, the molded resin portion 20 has a protrusion 36 that protrudes radially away from the coil (in the illustrated example, radially outward) at the same circumferential angular position as the inlet 24. The protrusion 36 prevents the refrigerant from perpendicularly impinging on the outer diameter surface of the molded resin portion 20 and facilitates the refrigerant to flow circumferentially through the annular flow path 30, thereby enabling efficient cooling of the stator 4 while suppressing local deterioration of the molded resin portion 20 and refrigerant leakage.

[0028] 15 shows an example in which the core of the stator 4 has a divided structure. Specifically, the core 16c has a first core portion 38a having slots 12 that accommodate the coils 10, and a second core portion 38b having an inner diameter surface fixed to the outer diameter surface of the first core portion 38a and in which the flow passages 14a are formed. The first core portion 38a and the second core portion 38b can be joined to each other by shrink fitting, adhesive, press fitting, etc., but can also be separated from each other.

[0029] As in the example of Figure 15, by making the core structure so that it can be divided into a part with slots and a part with flow paths, it becomes possible to easily change or upgrade the specifications of the motor, such as changing the shape and number of flow paths without changing the shape and number of slots.

[0030] 16 is a schematic axial cross-sectional view showing an example in which core 16 is formed from a plurality of identically shaped electromagnetic steel sheets 40. Typically, when forming flow passages 14 in core 16, before stacking the plurality of electromagnetic steel sheets 40, each electromagnetic steel sheet 40 is punched out in the direction of arrow 42 at a location corresponding to flow passage 14. This punching process leaves burrs 44 protruding in the punching direction on electromagnetic steel sheets 40. In particular, when electromagnetic steel sheets with different shapes are stacked, the burrs can cause localized gaps in the flow passages, which can lead to refrigerant leakage.

[0031] 16, it is preferable that the plurality of electromagnetic steel sheets 40 all have the same shape and are stacked so that the directions in which their burrs 44 protrude (punching directions) are all the same direction 42. In this way, even if each electromagnetic steel sheet 40 has burrs 44, it is possible to form a flow path 14 without gaps, and it is possible to prevent refrigerant leakage.

[0032] 17 is a schematic axial cross-sectional view showing an example in which the inner surface of the core is covered with resin. The side of the side of the core 16 on which the slots are formed (inner diameter surface in the illustrated example) is covered with, for example, the same resin 46 as that forming the molded resin portion 20, and the resin 46 covering the inner diameter surface of the core 16 is in communication with the molded resin portion 20. Covering the inner diameter surface of the core 16 with resin 46 protects the inner diameter surface and prevents refrigerant leakage between adjacent electromagnetic steel sheets 40 and between the core 16 and the molded resin portion 20.

[0033] 18 is a schematic axial cross-sectional view showing one example of the configuration of an outer rotor type electric motor. The electric motor 2d has a stator 4d and an outer rotor 8d that rotates radially outside the stator 4d relative to the stator 4d. Components of the electric motor 2d that are functionally equivalent to those of the electric motor 2 according to the first embodiment are given reference numerals with the letter "d" added to the reference numerals of the components of the first embodiment, and detailed descriptions thereof will be omitted.

[0034] In the outer rotor type electric motor 2d, the inlet ports 24d and outlet ports 26d for flowing refrigerant into the refrigerant flow paths 14d of the core 16d are formed in the coil end axial section L4 between the coil end 18d and the axial end face of the core 16d, and open on the side surfaces (outer surface and inner surface) of the substantially cylindrical core 16 where no slots are formed (i.e., where no coil 10d adjacent to the rotor 8d is disposed) (the inner surface in the example of FIG. 18). Therefore, the outer rotor type electric motor also achieves the same effects as the above-described inner rotor type electric motor.

[0035] For example, if the example of Fig. 5 is applied to an outer rotor type electric motor 2d, the coil end 18d will protrude radially inward from the radial outermost portion of the flow passage 14d. If the example of Fig. 13 is applied to the electric motor 2d, the molded resin portion 20d will have a recess that is recessed radially outward from the radial outermost portion of the flow passage 14d. Furthermore, if the example of Fig. 14 is applied to the electric motor 2d, the molded resin portion 20d will have a protrusion that protrudes radially inward from the coil 10d in the radial direction, at the same circumferential angular position as the inlet 24d. Furthermore, if the example of Fig. 15 is applied to the electric motor 2d, the core 16d will have a first core portion having a slot that accommodates the coil 10d, and a second core portion having an outer diameter surface fixed to the inner diameter surface of the first core portion and in which the flow passage 14d is formed. 17 is applied to electric motor 2d, the outer diameter surface of core 16d is covered with the same resin as that forming molded resin portion 20d, and the resin covering the outer diameter surface of core 16d is in communication with molded resin portion 20d. In this way, the embodiment applicable to inner rotor type electric motors can also be applied to outer rotor type electric motors based on the same concept.

[0036] According to the above-described embodiment, the inlet and outlet ports for circulating the coolant into the core are defined by the core and the mold resin, which are components typically provided in an electric motor, in cooperation with each other, eliminating the need for separate components for forming the inlet and outlet ports. Furthermore, because the inlet and outlet ports are formed within the coil end axial section, providing the inlet and outlet ports does not increase the overall length of the stator, allowing for the construction of a compact electric motor.

[0037] The following additional notes are provided regarding the above-described embodiment and modifications.

[0038] (Supplementary Note 1) A stator comprising: a coil; a core having a slot in which the coil is arranged and a refrigerant flow path; a molded resin portion at least partially embedding an axial end of the coil; and an inlet and an outlet formed in a coil end axial section between the axial end face of the core and the axial tip of the axial end of the coil, the inlet and outlet opening on a side surface of the core where the slot is not formed and fluidly communicating with the flow path.

[0039] (Supplementary Note 2) The stator according to Supplementary Note 1, wherein the inlet and the outlet are defined by the axial end surface of the core and the molded resin portion.

[0040] (Supplementary Note 3) The stator according to Supplementary Note 1 or 2, wherein the axial end of the coil protrudes radially toward the inlet or outlet more than a portion of the flow path farthest from the inlet or outlet in the radial direction.

[0041] (Appendix 4) The stator according to any one of Appendices 1 to 3, wherein the molded resin portion has an annular refrigerant flow path fluidly communicating with the inlet or the outlet, and the refrigerant flow path fluidly communicating with each of the plurality of flow paths.

[0042] (Supplementary Note 5) The stator according to any one of Supplementary Notes 1 to 4, wherein the flow passages extend in the axial direction within the core and are arranged at the same circumferential angular positions as the slots.

[0043] (Supplementary Note 6) The stator according to Supplementary Note 5, wherein a radial cross section of the flow path has an elliptical shape that is long in the circumferential direction.

[0044] (Supplementary Note 7) The stator according to Supplementary Note 5, wherein a radial cross section of the flow passage has a substantially triangular shape having a vertex at the same circumferential angular position as the center of the slot.

[0045] (Supplementary Note 8) The stator according to any one of Supplementary Notes 1 to 7, further comprising a groove formed on a surface of the core, extending in the axial direction, and positioned between circumferential angular positions of adjacent slots in a radial cross section of the core.

[0046] (Supplementary Note 9) The stator according to any one of Supplementary Notes 1 to 8, wherein the molded resin portion has a recess that is recessed radially toward the coil relative to a portion of the flow path that is farthest from the inlet or the outlet in the radial direction.

[0047] (Supplementary Note 10) The stator according to any one of Supplementary Notes 1 to 9, wherein the molded resin portion has a protrusion that protrudes radially to the opposite side from the coil, at the same circumferential angular position as the inlet.

[0048] (Appendix 11) The stator according to Appendix 1, wherein the core has a first core portion having the slot, and a second core portion having an inner diameter surface fixed to the outer diameter surface of the first core portion or an outer diameter surface fixed to the inner diameter surface of the first core portion, and in which the flow path is formed.

[0049] (Appendix 12) The stator according to any one of Appendices 1 to 11, wherein the core is made of a plurality of stacked electromagnetic steel plates, and the electromagnetic steel plates are stacked such that burrs on each electromagnetic steel plate protrude in the same direction.

[0050] (Supplementary Note 13) The stator according to any one of Supplementary Notes 1 to 12, wherein the side of the core on which the slot is formed is covered with the same material as the material forming the molded resin portion.

[0051] (Supplementary Note 14) An electric motor comprising: the stator according to any one of Supplementary Notes 1 to 13; and a rotor configured to be rotatable relative to the stator.

[0052] 2 electric motor 4 stator 8 rotor 10 coil 12 slot 14, 15 flow path 16 core 18 coil end 20 molded resin portion 22 housing 24 inlet 26 outlet 30 annular flow path 32 axial end face 34 recess 36 protrusion 38a inner core portion 38b outer core portion 40 electromagnetic steel sheet 44 burr

Claims

1. A stator comprising: a coil; a core having a slot in which the coil is arranged and a refrigerant flow path; a molded resin portion at least partially embedding the axial end of the coil; and an inlet and outlet formed within the coil end axial section between the axial end face of the core and the axial tip of the axial end of the coil, opening on a side surface of the core where the slot is not formed and fluidly communicating with the flow path.

2. The stator according to claim 1, wherein the inlet and outlet are defined by the axial end face of the core and the molded resin portion.

3. A stator as described in claim 1 or 2, wherein the axial end of the coil extends radially toward the inlet or outlet side more than the part of the flow path farthest from the inlet or outlet side in the radial direction.

4. A stator according to any one of claims 1 to 3, wherein the molded resin portion has an annular refrigerant flow path that is fluidly connected to the inlet or outlet, and the refrigerant flow path is fluidly connected to each of the plurality of flow paths.

5. A stator according to any one of claims 1 to 4, wherein the flow passages extend axially within the core and are arranged at the same circumferential angular positions as the slots.

6. A stator according to claim 5, wherein the radial cross section of the flow passage has an elliptical shape that is elongated in the circumferential direction.

7. A stator according to claim 5, wherein the radial cross section of the flow passage has a substantially triangular shape having a vertex at the same circumferential angular position as the center of the slot.

8. A stator according to any one of claims 1 to 7, having grooves formed on the surface of the core, extending in the axial direction, and positioned between the circumferential angular positions of adjacent slots in a radial cross section of the core.

9. A stator according to any one of claims 1 to 8, wherein the molded resin portion has a recess that is recessed radially toward the coil, relative to the portion of the flow path that is farthest radially from the inlet or outlet.

10. A stator according to any one of claims 1 to 9, wherein the molded resin portion has a protrusion that protrudes radially opposite the coil at the same circumferential angular position as the inlet.

11. A stator as described in claim 1, wherein the core has a first core portion having the slot, and a second core portion having an inner diameter surface fixed to the outer diameter surface of the first core portion or an outer diameter surface fixed to the inner diameter surface of the first core portion, and in which the flow path is formed.

12. A stator according to any one of claims 1 to 11, wherein the core is made of a plurality of laminated electromagnetic steel plates, and the electromagnetic steel plates are laminated so that the burrs on each electromagnetic steel plate protrude in the same direction.

13. A stator according to any one of claims 1 to 12, wherein the side of the core on which the slots are formed is covered with the same material as the material forming the molded resin portion.

14. An electric motor comprising: a stator according to any one of claims 1 to 13; and a rotor configured to be rotatable relative to the stator.

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