Method for manufacturing a stator for a rotating electric machine and a stator for a rotating electric machine

Abstract

Effectively improves the electrical insulation of the coil end. [Solution] A stator for a rotating electric machine is disclosed, comprising a stator core, a stator coil mounted on the stator core and having coil ends at both axial ends, and an insulating material portion provided at the coil ends and formed by foamed varnish, wherein the insulating material portion has an uneven surface due to foaming.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a stator for a rotating electrical machine and a stator for a rotating electrical machine.

Background Art

[0002] A technique is known in which a resin composition containing a microcapsule-type foaming agent is pre-applied to a slot liner for fixing a stator coil of a rotating electrical machine, and after inserting the slot liner and coil wire into the slot of the stator core, the foaming agent is foamed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the conventional technology as described above aims to fix the coil wire in the slot, and it is difficult to enhance the electrical insulation of the coil end.

[0005] Therefore, on one aspect, the present disclosure aims to effectively enhance the electrical insulation of the coil end.

Means for Solving the Problems

[0006] On one aspect, a stator for a rotating electrical machine is provided, which includes a stator core, a stator coil attached to the stator core and having coil ends at both axial ends, and an insulating material portion provided at the coil end and formed of a foamed varnish. The insulating material portion has concavo-convex portions caused by foaming on the surface.

Effects of the Invention

[0007] In one respect, the present disclosure makes it possible to effectively improve the electrical insulation of the coil ends. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic cross-sectional view showing the cross-sectional structure of a motor according to one embodiment. [Figure 2] This is a plan view of the stator core in its individual component state. [Figure 3] This diagram schematically shows a pair of coil pieces assembled to a stator core. [Figure 4] This is a schematic front view of one coil section. [Figure 5] This is a cross-sectional view along line AA in Figure 4. [Figure 6] This is a schematic cross-sectional view showing the insulating material portion provided at the coil end of this embodiment. [Figure 7] This diagram shows a cross-section of the insulating material portion located between two adjacent connecting sections. [Figure 8] This is an explanatory diagram (part 1) showing suitable locations for the formation of the first and second parts. [Figure 9] This is an explanatory diagram (part 2) showing suitable locations for the formation of the first and second parts. [Figure 10] This figure shows the test results for the partial discharge initiation voltage. [Figure 11] This is a schematic flowchart of the essential parts of the manufacturing method for the stator in this embodiment. [Modes for carrying out the invention]

[0009] The following describes each embodiment in detail with reference to the attached drawings. Note that the dimensional ratios in the drawings are merely examples and are not exhaustive. Furthermore, shapes and other details in the drawings may be partially exaggerated for illustrative purposes. Also, for clarity, in some cases, only a portion of parts with the same attribute are assigned reference numerals in the drawings.

[0010] FIG. 1 is a cross-sectional view schematically showing a cross-sectional structure of a motor 1 according to an embodiment.

[0011] In FIG. 1, a rotation shaft 12 of the motor 1 is illustrated. In the following description, the axial direction refers to the direction in which the rotation shaft (rotation center) 12 of the motor 1 extends, and the radial direction refers to the radial direction centered on the rotation shaft 12. Accordingly, the outer side in the radial direction refers to the side away from the rotation shaft 12, and the inner side in the radial direction refers to the side toward the rotation shaft 12. Also, the circumferential direction corresponds to the rotation direction around the rotation shaft 12.

[0012] The motor 1 may be, for example, a motor for vehicle drive used in a hybrid vehicle or an electric vehicle. However, the motor 1 may be used for any other arbitrary application.

[0013] The motor 1 is of an inner rotor type, and the stator 21 is provided so as to surround the outer side in the radial direction of the rotor 30. The outer side in the radial direction of the stator 21 is fixed to the motor housing 10.

[0014] The rotor 30 is disposed on the inner side in the radial direction of the stator 21. The rotor 30 includes a rotor core 32 and a rotor shaft 34. The rotor core 32 is fixed to the outer side in the radial direction of the rotor shaft 34 and rotates integrally with the rotor shaft 34. The rotor shaft 34 is rotatably supported by the motor housing 10 via bearings 14a and 14b. Note that the rotor shaft 34 defines the rotation shaft 12 of the motor 1.

[0015] The rotor core 32 is formed, for example, from a laminated steel sheet of an annular magnetic material. A permanent magnet 321 is inserted into a magnet hole 320 of the rotor core 32. The number, arrangement, etc. of the permanent magnets 321 are arbitrary. In a modified example, the rotor core 32 may be formed of a compacted powder body in which magnetic powder is compressed and solidified.

[0016] As shown in FIG. 1, the rotor shaft 34 has a hollow portion 34A. The hollow portion 34A extends over the entire axial length of the rotor shaft 34. The hollow portion 34A may function as an oil passage. For example, as indicated by an arrow R1 in FIG. 1, oil is supplied from one end side in the axial direction into the hollow portion 34A, and the oil flows along the radially inner surface of the rotor shaft 34, so that the rotor core 32 can be cooled from the radially inner side. Further, the oil flowing along the radially inner surface of the rotor shaft 34 is ejected radially outward through oil holes 341 and 342 formed at both ends of the rotor shaft 34 (arrows R5 and R6), and may be used for cooling the coil ends 240A and 240B.

[0017] In FIG. 1, the motor 1 having a specific structure is shown. However, the structure of the motor 1 is arbitrary as long as it has a stator coil 24 (described later) joined by welding. Therefore, for example, the rotor shaft 34 may not have the hollow portion 34A, or may have a hollow portion having an inner diameter significantly smaller than that of the hollow portion 34A. Also, in FIG. 1, a specific cooling method is disclosed, but the cooling method of the motor 1 is arbitrary. For example, an oil introduction pipe inserted into the hollow portion 34A may be provided, or oil may be dripped from the oil passage in the motor housing 10 radially outward toward the coil ends 240A and 240B.

[0018] Also, in FIG. 1, the motor 1 is an inner rotor type motor in which the rotor 30 is disposed inside the stator 21, but it may be applied to other types of motors. For example, it may be applied to an outer rotor type motor in which the rotor 30 is concentrically disposed outside the stator 21, a dual rotor type motor in which the rotor 30 is disposed both outside and inside the stator 21, or the like. Also, the supply mode of oil (oil for cooling the motor 1) to the motor housing 10 is arbitrary, and it may be supplied using an electric oil pump, a mechanical oil pump, or the scooping of a gear.

[0019] Next, referring to FIGS. 2 and later, the configuration regarding the stator 21 will be described in detail.

[0020] Figure 2 is a plan view of the stator core 22 in its standalone state. Figure 3 is a schematic diagram showing a pair of coil pieces 52 assembled to the stator core 22. Figure 4 is a schematic front view of one of the coil pieces 52. Figure 5 is a cross-sectional view along line AA in Figure 4, and is a cross-sectional view at the slot insertion portion 56. Note that in Figure 3, the relationship between the pair of coil pieces 52 and the slot 220 is shown with the radially inner side of the stator core 22 unfolded. Also, in Figure 3, the stator core 22 is shown by a dotted line, and a portion of the slot 220 is omitted from the illustration.

[0021] The stator 21 includes a stator core 22 and a stator coil 24 (see Figure 1).

[0022] The stator core 22 is made of, for example, an annular laminated steel plate of magnetic material, but in a modified example, the stator core 22 may be formed from a compacted body of magnetic powder that has been compressed and solidified. The stator core 22 may be formed as a segmented core divided in the circumferential direction, or it may be in a form that is not divided in the circumferential direction. Multiple slots 220 around which the stator coil 24 is wound are formed on the radially inner side of the stator core 22. Specifically, as shown in Figure 2, the stator core 22 includes an annular back yoke 22A and multiple teeth 22B extending radially inward from the back yoke 22A, with slots 220 formed between the multiple teeth 22B in the circumferential direction. The number of slots 220 is arbitrary, but in this embodiment, as an example, there are 48.

[0023] The stator coils 24 form the stator coils 24 for the U-phase, V-phase, and W-phase. The base end of each phase's stator coil 24 is connected to an input terminal (not shown), and the end of each phase's stator coil 24 is connected to the end of the other phase's stator coil 24 to form the neutral point of the motor 1. In other words, the stator coils 24 are star-connected. However, the connection configuration of the stator coils 24 may be changed as appropriate depending on the required motor characteristics, etc. For example, the stator coils 24 may be delta-connected instead of star-connected.

[0024] Each phase's stator coil 24 is constructed by joining multiple coil pieces 52. The coil pieces 52 are in the form of segment coils, which divide each phase's stator coil 24 into units that are easy to assemble (for example, units that are inserted into two slots 220). As shown in Figure 5, the coil pieces 52 are made of a linear conductor (flat wire) 60 with a rectangular cross-section, covered with an insulating coating 62. In this embodiment, the linear conductor 60 is made of copper as an example. However, in modified examples, the linear conductor 60 may be made of other conductive materials such as iron or aluminum. Also, the cross-sectional shape of the linear conductor 60 may be other than rectangular.

[0025] Before being assembled to the stator core 22, the coil piece 52 may be formed in a substantially U-shape, having a pair of straight sections 50 and a connecting section 54 that connects the pair of straight sections 50. When assembling the coil piece 52 to the stator core 22, the pair of straight sections 50 are each inserted into a slot 220 (see Figure 3). As a result, the connecting section 54 extends circumferentially across multiple teeth 22B (and consequently multiple slots 220) on the other axial end of the stator core 22, as shown in Figure 3. The number of slots 220 that the connecting section 54 crosses is arbitrary, but there are three in Figure 3. After being inserted into the slots 220, the straight sections 50 are bent circumferentially along their length, as shown by the dashed line in Figure 4. As a result, the straight section 50 consists of a slot insertion section 56 that extends axially within the slot 220 and a connecting section 58 that extends circumferentially on one axial end of the stator core 22. In this case, the connecting section 54 forms one of the coil ends 240A and 240B, and the connecting section 58 forms the other of the coil ends 240A and 240B.

[0026] In Figure 4, the pair of straight sections 50 are bent in a direction away from each other, but this is not limited to this. For example, the pair of straight sections 50 may be bent in a direction towards each other. The stator coil 24 may also have a neutral point coil piece or the like to connect the ends of the stator coils 24 of each phase to form a neutral point.

[0027] Multiple slot insertion portions 56 of the coil pieces 52 shown in Figure 4 are inserted radially into a single slot 220. Consequently, multiple connecting portions 58 extending in the circumferential direction are arranged radially on one axial end of the stator core 22. As shown in Figure 3, the connecting portion 58 of one coil piece 52 that protrudes from one slot 220 and extends in the first circumferential direction (for example, clockwise) is joined to the connecting portion 58 of another coil piece 52 that protrudes from another slot 220 and extends in the second circumferential direction (for example, counterclockwise) at their joining portions 40 (see Figure 4).

[0028] In this embodiment, a coil piece 52 having two slot insertion portions 56 is used as an example, but it is also applicable to other forms of coil pieces, such as a coil piece having four or more slot insertion portions 56.

[0029] Next, the characteristic configuration of this embodiment will be described with reference to Figure 6 and subsequent figures.

[0030] Figure 6 is a schematic cross-sectional view showing the insulating material portion 70 provided on the coil end 240A of this embodiment. In Figure 6, only one side of the cross-section, which is rotationally symmetric with respect to the rotation axis 12, is shown. In Figure 6, the Z direction is the axial direction, and the Z1 side is the axially outward direction. Also, the Y direction is the radial direction, and the Y1 side is the radially outward direction. In the following description, the insulating material portion 70 provided on the coil end 240A will be mainly explained, but a similar insulating material portion may also be provided on the coil end 240B.

[0031] An insulating material portion 70 is provided at the coil end 240A of this embodiment. The insulating material portion 70 is formed of foamed varnish. The material of the foamed varnish is arbitrary, but for example, it may be a resin material containing foam, in which case the foam is foamed in such a manner that it forms uneven surfaces on the surface of the resin material due to foaming.

[0032] The insulating material portion 70 may be provided so as to cover the entire coil end 240A. That is, the insulating material portion 70 may be provided so as not to expose any coil piece 52 that forms the coil end 240A.

[0033] Figure 7 shows a cross-section of the insulating material portion 70 located between two adjacent connecting portions 58. The two adjacent connecting portions 58 are the connecting portions 58 of the two coil pieces 52 that form the coil end 240A.

[0034] As shown in Figure 7, the insulating material portion 70 of this embodiment has an uneven surface 77 caused by foaming. The uneven surface 77 is basically formed over the entire surface. As described above with reference to Figure 1, in this embodiment, cooling oil for motor cooling is supplied to the coil end 240A. When oil is supplied to the insulating material portion 70 of the coil end 240A, the oil penetrates into the uneven surface 77 of the insulating material portion 70 and is easily retained by the uneven surface 77. In addition, the oil is also more easily penetrated into the voids inside the insulating material portion 70.

[0035] In this embodiment, the insulating material portion 70 has a first portion 71 and a second portion 72 at the coil end 240A.

[0036] The first portion 71 is formed in the gap between two adjacent connecting portions 58. The first portion 71 can be formed by introducing (impregnating) foamed varnish into the gap between two adjacent connecting portions 58 and causing the foam to expand.

[0037] The second portion 72 is continuous with the first portion 71 and protrudes convexly from between two adjacent connecting portions 58. The second portion 72 can be formed by introducing a sufficient amount of foaming varnish into the gap between two adjacent connecting portions 58 and causing the foam to expand. That is, when a sufficient amount of foaming varnish is introduced into the gap and the foam is caused to expand, it expands to a volume greater than the volume of the gap, and the second portion 72 is formed.

[0038] Since the second part 72 is a convex protrusion from the gap between two adjacent connecting parts 58, oil is easily supplied directly to the surface of the second part 72. For example, when the motor 1 is operating, oil is basically always supplied to the surface of the second part 72. Therefore, the second part 72 can basically always retain oil when the motor 1 is operating.

[0039] Such first portion 71 and second portion 72 can be formed in the gaps between each connecting portion 58 of the coil end 240A.

[0040] Figures 8 and 9 are explanatory diagrams showing suitable locations for forming the first portion 71 and the second portion 72. For the sake of clarity, the insulating material portion 70 is not shown in Figures 8 and 9.

[0041] In the following explanation, the coil end 240 of one phase refers to the coil end portion formed by that one phase among the coil ends 240A formed by the three-phase stator coils 24.

[0042] Figures 8 and 9 are explanatory diagrams illustrating the positional relationship of the stator coils 24 of each phase at the coil end 240A. Figure 8 shows a portion of the coil end 240A in a side view (view perpendicular to the axial direction), and Figure 9 shows a portion of the coil end 240A in a top view (view in the axial direction). In Figures 8 and 9, for ease of understanding, each phase's coil end 240 is given a different hatching for each phase: the U-phase coil end 240 is labeled 240(U), the V-phase coil end 240 is labeled 240(V), and the W-phase coil end 240 is labeled 240(W). In addition, in Figure 9, the L direction parallel to the radial direction is defined, with the L1 side corresponding to the radially inward direction and the L2 side corresponding to the radially outward direction.

[0043] In this embodiment, the insulating material portion 70 is formed over the entire coil end 240A, including the gap between two adjacent connecting portions 58. Therefore, the insulating material portion 70 is also formed in the gaps Δ1 to Δ3 at locations Q1 to Q3 shown in Figure 8. The insulating material portion 70 formed at locations Q1 and Q2 may have a cross-section along line BB shown in Figure 8 that is the same as the cross-section shown in Figure 7. Locations Q1 and Q2 include the gaps Δ1 and Δ2 between surfaces where different phases face each other in the axial direction (surfaces of two adjacent connecting portions 58), and location Q3 includes the gap Δ3 between surfaces where the same phases face each other in the axial direction (surfaces of two adjacent connecting portions 58).

[0044] Similarly, insulating material portions 70 are also formed in the gaps Δ4 and Δ5 at locations Q4 and Q5 shown in Figure 9. Location Q4 includes a gap Δ4 between surfaces where different phases face each other radially (surfaces of two adjacent connecting portions 58), and location Q5 includes a gap Δ5 between surfaces where the same phases face each other radially (surfaces of two adjacent connecting portions 58). The insulating material portions 70 formed at locations Q4 and Q5 may have a cross-section along line CC shown in Figure 8 that is the same as the cross-section shown in Figure 7.

[0045] Figure 10 shows the test results for the Partial Discharge Inception Voltage (PDIV). Figure 10 shows the test results 101 before the application of the foamed varnish, the test results 102 after the application and foaming of the foamed varnish, and the test results 103 of this embodiment. Note that the test result 103 of this embodiment corresponds to the test result after the application and foaming of the foamed varnish, with oil applied to the foamed varnish. The vertical axis shows the Partial Discharge Inception Voltage, the letters "UV" on the horizontal axis indicate the Partial Discharge Inception Voltage between the U phase and the V phase, "VW" indicates the Partial Discharge Inception Voltage between the V phase and the W phase, and so on.

[0046] As can be seen from Figure 10, comparing test result 103 with other test results 101 and 102, this embodiment allows for a significant increase in the partial discharge initiation voltage. In particular, the fact that the partial discharge initiation voltage can be significantly increased when oil is applied to the foamed varnish (insulating material part 70) compared to when no oil is applied (test result 102) is a new finding. It can be inferred that in this embodiment, the uneven surface of the insulating material part 70 enhances this effect. The oil applied to the foamed varnish (insulating material part 70) may be the same as the oil used to cool the motor 1.

[0047] In this way, according to this embodiment, the electrical insulation between different phases can be effectively increased at the coil end 240A (i.e., the partial discharge initiation voltage can be effectively increased).

[0048] Next, with reference to Figure 11, the manufacturing method of the stator 21 in this embodiment will be outlined.

[0049] Figure 11 is a schematic flowchart of the main parts of the manufacturing method of the stator 21 in this embodiment.

[0050] This manufacturing method includes a step (step S1100) of mounting a stator coil 24 onto a stator core 22 to form an assembly (not shown) having coil ends 240A and 240B at both axial ends.

[0051] Next, this manufacturing method includes a step (step S1102) of impregnating the coil ends 240A and 240B with foamed varnish. This step may be achieved by dripping the foamed varnish onto the coil ends 240A and 240B, or by immersing the coil ends 240A and 240B in a tank containing the foamed varnish.

[0052] Next, this manufacturing method includes a step (step S1104) in which the foamed varnish impregnated into the coil ends 240A and 240B is heated and hardened. During this step, the foamed varnish foams up, and the insulating material portion 70 is formed. That is, an insulating material portion 70 having an uneven surface (particularly the surface of the second portion 72) is formed.

[0053] Next, this manufacturing method includes a cooling step (step S1106), a trimming step (step S1108), and a physical inspection step (step S1110), followed by an oil application step (step S1112). The oil application step includes applying oil to the coil ends 240A and 240B to retain oil in the insulating material portion 70. The method of applying the oil is arbitrary and may include dripping or immersion.

[0054] Furthermore, this manufacturing method includes an electrical inspection step (step S1114). The electrical inspection step may include a step of checking whether the required electrical insulation is ensured at coil ends 240A and 240B. For example, the electrical inspection step may include a step of checking whether the measured value of the partial discharge initiation voltage exceeds a reference value.

[0055] Once it is confirmed in the electrical inspection process (step S1114) that the necessary electrical insulation is ensured, the stator 21 is completed and sent to the shipping process (or the assembly process of the transmission, etc.).

[0056] According to this manufacturing method, a stator 21 can be produced in which the electrical insulation of coil ends 240A and 240B is effectively enhanced.

[0057] Although each embodiment has been described in detail above, the invention is not limited to any particular embodiment, and various modifications and changes are possible within the scope described in the claims. Furthermore, it is possible to combine all or more of the components of the embodiments described above. [Explanation of Symbols]

[0058] 21 Stator (Stator for rotating electric machine), 22 Stator core, 24 Stator coil, 240A, 240B Coil end, 70 Insulating material section, 71 First section, 72 Second section

Claims

1. Stator core and A stator coil mounted on the stator core and having coil ends at both axial ends, The coil end is provided with an insulating material portion formed of foamed varnish, The aforementioned insulating material portion has an uneven surface caused by foaming, and is a stator for a rotating electric machine.

2. The insulating material portion is located at the coil end. A first portion formed in the gap between coil wires related to the stator coil, A stator for a rotating electric machine according to claim 1, further comprising a second portion that is continuous with the first portion and protrudes convexly from between the coil wires.

3. The stator for a rotating electric machine according to claim 1 or 2, wherein the insulating material portion holds oil for cooling the rotating electric machine in the uneven portion.

4. A mounting step involves attaching stator coils to a stator core to form an assembly having coil ends at both axial ends, After the mounting step, a forming step is performed in which foamed varnish is applied to the coil end, and the foamed varnish is foamed to form an insulating material portion on the coil end. The process includes, after the forming step, a step of applying oil to the insulating material portion, A method for manufacturing a stator for a rotating electric machine, comprising the forming step of creating an uneven surface on the insulating material portion due to foaming.

5. A case that forms a containment space containing oil for cooling a rotating electric machine, The rotor and stator housed in the aforementioned case are included. The stator is, Stator core and A stator coil mounted on the stator core and having coil ends at both axial ends, The coil end is provided with an insulating material portion formed of foamed varnish, The insulating material portion has an uneven surface caused by foaming, which is a rotating electric machine having an uneven surface that holds the oil.

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