Coil manufacturing method

Abstract

To ensure a meaningful difference of thickness of an insulator film between a coil end portion and a slot housing portion, which are electrocoated with the film.SOLUTION: A production method of a coil having an insulator film including a first isolation layer and a second isolation layer, comprises: a preparation step for preparing a coil material before being coated with the insulator film and after being formed; a first electrocoating step for forming the first isolation layer by electrocoating a coil end portion and a slot housing portion of the coil material; and a second electrocoating step, which is performed after the first electrocoating step, for forming the second isolation layer on the outside of the first isolation layer of the coil end portion of the coil material by electrocoating only the coil end portion among the coil end portion and the slot housing portion of the coil material.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a method for manufacturing a coil. [Background technology]

[0002] A technique is known in which the thickness of an insulating film is made different between the coil end portion and the slot-receiving portion of a coil material by using multiple electrodeposition baths (for example, Patent Document 1). In this technique, a first layer of insulating film is formed on the coil end portion of the coil end portion and the slot-receiving portion in one electrodeposition bath, and then a second layer of insulating film is formed on both the coil end portion and the slot-receiving portion in another electrodeposition bath. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-235648 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned conventional technology, since both the coil end portion and the slot-receiving portion are immersed in another electrodeposition bath with the insulating film (first layer) applied only to the coil end portion, it is difficult to ensure a significant thickness of the second layer of the insulating film in the coil end portion. This is because the potential difference between the coil end portion on which the insulating film (first layer) has already been formed and the paint is likely to be smaller than the potential difference between the slot-receiving portion and the paint in the other electrodeposition bath, making it difficult to form a further insulating film (second layer). As a result, it is difficult to ensure a significant difference in the thickness of the insulating film between the coil end portion and the slot-receiving portion. Note that if a significant difference in thickness is to be ensured, a long electrodeposition process for the second layer is required, and the thickness of the slot-receiving portion becomes unnecessarily large, which may reduce the conductor occupancy rate (coil space factor) in the slot of the stator core.

[0005] Therefore, in one aspect, an object of the present invention is to ensure a significant difference in thickness of the insulating film between the coil end portion and the slot receiving portion by electrocoating. [Means for solving the problem]

[0006] In one aspect, a method for manufacturing a coil having an insulating film including a first insulating layer and a second insulating layer, comprising: a preparation step of preparing a coil material before the insulating film is applied and after molding; a first electrodeposition coating step of forming the first insulating layer by electrodeposition coating the coil end portion and the slot-accommodated portion of the coil blank; There is provided a manufacturing method including a second electrocoating process that is executed after the first electrocoating process, and that forms the second insulating layer outside the first insulating layer in the coil end portion of the coil material by electrocoating only the coil end portion of the coil material and the slot accommodating portion. Effect of the Invention

[0007] In one aspect, it is possible to ensure a significant difference in thickness of the insulating film between the coil end portion and the slot receiving portion by electrocoating. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a cross-sectional view taken along the axial direction of the stator. [Diagram 2] FIG. 2 is a three-view diagram of one coil piece. [Figure 3A] 4 is a schematic cross-sectional view of a slot-receiving portion of a coil piece according to the first embodiment. FIG. [Figure 3B] 3 is a schematic cross-sectional view of a transition portion (coil end portion) of a coil piece according to Example 1. FIG. [Figure 4A] FIG. 2 is an explanatory diagram of an outline of a first electrodeposition coating step according to the first embodiment. [Figure 4B] FIG. 4 is an explanatory diagram of an outline of a second electrodeposition coating step according to the first embodiment. [Figure 4C]FIG. 2 is a schematic plan view showing one workpiece according to the first embodiment. [Figure 5A] FIG. 11 is a schematic cross-sectional view of a slot-receiving portion of a coil piece according to a second embodiment. [Figure 5B] 11 is a schematic cross-sectional view of a transition portion (coil end portion) of a coil piece according to Example 2. FIG. [Figure 6A] FIG. 1 is an explanatory diagram of an outline of a first electrodeposition coating step according to Example 2. [Figure 6B] FIG. 10 is an explanatory diagram of an outline of a second electrodeposition coating step according to Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Each embodiment will be described in detail below with reference to the accompanying drawings. Note that the dimensional ratios in the drawings are merely examples and are not intended to be limiting, and shapes and the like in the drawings may be partially exaggerated for the sake of explanation.

[0010] In the following, first, the stator 10 for a rotating electric machine according to this embodiment will be described, and then the coil manufacturing method will be described.

[0011] Fig. 1 is a cross-sectional view taken along the axial direction of the stator 10 in a state in which the coil pieces 52 are assembled to the stator core 112. An enlarged view of a portion Q2 in Fig. 1 is also shown. Fig. 2 is a three-view diagram of one of the coil pieces 52.

[0012] The stator coils 114 include a U-phase coil, a V-phase coil, and a W-phase coil (hereinafter, when U, V, and W are not distinguished, they are referred to as "phase coils"). The base end of each phase coil is connected to an input terminal (not shown), and the end of each phase coil is connected to the end of the other phase coil to form a neutral point. In other words, the stator coils 114 are star-connected. However, the connection mode of the stator coils 114 may be changed as appropriate depending on the required motor characteristics, etc. For example, the stator coils 114 may be delta-connected instead of star-connected.

[0013] Each phase coil of the stator coil 114 is formed by connecting a plurality of coil pieces 52. The coil pieces 52 are in the form of segment coils (segment conductors) obtained by dividing the phase coil into units that are easy to assemble (for example, units that can be inserted into two slots 23).

[0014] Each coil piece 52 is formed by coupling a segment conductor 52A on one axial side to a segment conductor 52B on the other axial side.

[0015] Each of the segment conductors 52A and 52B may be formed into a U-shape having a pair of linear slot-accommodated portions 50 and a coil end portion (crossover portion) 54 connecting the pair of slot-accommodated portions 50. When the coil pieces 52 are assembled to the stator core 112, the pair of slot-accommodated portions 50 are inserted into the slots 23 (see FIG. 1). In this case, the coil pieces 52 can be assembled, for example, in the axial direction.

[0016] 1 are inserted into one slot 23, lined up in the radial direction. Thus, at both axial ends of the stator core 112, a plurality of circumferentially extending coil end portions 54 are lined up in the radial direction. Note that only the slot-accommodated portions 50 of the coil pieces 52 forming the same phase coil are inserted into one slot 23. Here, as an example, six coil pieces 52 are assembled into one slot 23 (i.e., a six-layer winding structure).

[0017] 2, the segment conductors 52A and 52B are each configured such that one of the slot-accommodating portions 50 on both circumferential sides can be coupled, while the other is offset from the other by one layer in the radial direction. Specifically, the segment conductors 52A and 52B each include offset portions 521A and 521B at the tops of the opposing surfaces 42, and the offset portions 521A and 521B are offset in opposite radial directions.

[0018] The coil pieces 52 are wound around the stator core 112 in a lap winding manner. In this case, the segment conductor 52A and the segment conductor 52B constituting one coil piece 52 are joined at the joint portions 40 (i.e., the open end portions) of the slot-accommodated portions 50 on one side of the slot-accommodated portions 50 on both circumferential sides, as shown in Fig. 2. In this case, the slot-accommodated portion 50 on the other side is joined to another coil piece 52. In this case, the joint portions 40 have opposing surfaces 42 that are entirely opposed to each other in the radial direction and are in surface contact with each other, and the joint portions 40 are joined together with the opposing surfaces 42 overlapping each other.

[0019] 1 and 2 show the stator core 112 and the stator coil 114 having a specific structure, the structure of the stator core 112 and the stator coil 114 is arbitrary as long as the stator coil 114 has the insulating films 130A and 130B. The coil pieces in the form of a segment coil are not limited to being coupled in the slots 23 of the stator core 112 like the coil pieces 52, and may be in other forms, such as being coupled at one axial end side. The winding method of the stator coil 114 is also arbitrary, and may be a winding method other than the lap winding type described above, such as a wave winding type. Next, the coil insulating film configuration and the coil manufacturing method will be described for each embodiment.

[0020] [Example 1] First, the cross-sectional structure (insulating film 130A, etc.) of coil piece 52 according to Example 1 will be described in detail with reference to Figures 3A and 3B. Figure 3A is a schematic cross-sectional view of slot-receiving portion 50 in coil piece 52 according to Example 1, and Figure 3B is a schematic cross-sectional view of coil end portion 54 in coil piece 52 according to Example 1.

[0021] As shown in Figures 3A and 3B, the coil piece 52 is formed by covering a linear conductor (rectangular wire) 120 having a substantially rectangular cross section with an insulating film 130A. Here, the linear conductor is formed of copper, as an example. However, in modified examples, the linear conductor may be formed of other conductive materials such as iron or aluminum. Furthermore, the cross-sectional shape of the linear conductor may be other than rectangular.

[0022] In this embodiment, the insulating film 130A is formed in a different manner for the slot-accommodating portion 50 and the coil end portion 54. Specifically, the insulating film 130A in the slot-accommodating portion 50 has a first electrodeposition coating layer 1301A, whereas the insulating film 130A in the coil end portion 54 has a first electrodeposition coating layer 1301A and a second electrodeposition coating layer 1302A. In this embodiment, the insulating film 130A in the slot-accommodating portion 50 is made of the first electrodeposition coating layer 1301A, but may include other layers (layers different from the second electrodeposition coating layer 1302A). Similarly, in this embodiment, the insulating film 130A in the coil end portion 54 is made of the first electrodeposition coating layer 1301A and the second electrodeposition coating layer 1302A, but may include other layers.

[0023] In this embodiment, the second electrodeposition coating layer 1302A is formed outside the first electrodeposition coating layer 1301A in the coil end portion 54. That is, in the coil end portion 54, like the slot accommodating portion 50, the first electrodeposition coating layer 1301A is provided in a manner in which it contacts the linear conductor 120.

[0024] The first electrodeposition coating layer 1301A is a layer formed by electrodeposition coating with paint. The paint may be an insulating paint containing polyamide-imide resin or polyimide resin, or an insulating paint containing epoxy resin.

[0025] The second electrodeposition coating layer 1302A is a layer formed by electrodeposition coating with paint, which is the same as the paint used to form the first electrodeposition coating layer 1301A.

[0026] The paint may contain a filler that has a function of increasing the resistance of the insulating film 130A to partial discharge. Such a filler is a material that has discharge resistance, and may be, for example, scaly mica particles, scaly silica particles, or the like. Such a filler also has a function of increasing the creepage distance.

[0027] Incidentally, in order to improve the insulation between different phases (i.e., to increase the inception voltage of partial discharge) in the coil end portions 54 of the coil pieces 52, it is desirable that the insulating film 130A has a relatively large thickness. Also, it is desirable that the coil end portions 54 have a relatively high resistance to partial discharge (a property that makes it difficult for deterioration to occur even if a partial discharge phenomenon occurs).

[0028] On the other hand, in the slot-received portion 50 in which the coil piece 52 is received in the slot 23, it is preferable that the insulating film 130A is relatively thin in order to increase the occupancy rate of the conductor in the slot 23 (coil space factor).

[0029] In this respect, in the present embodiment, the coil piece 52 can have a relatively large thickness in the coil end portion 54 because the insulating film 130A has the second electrodeposition coating layer 1302A in addition to the first electrodeposition coating layer 1301A. In particular, in this embodiment, the second electrodeposition coating layer 1302A is not provided in the slot-receiving portion 50, so it can be formed to a desired thickness without being restricted by the conductor occupancy rate in the slot-receiving portion 50. As a result, the second electrodeposition coating layer 1302A formed to the desired thickness can effectively improve the insulation properties of the coil end portion 54. Furthermore, when the paint contains the above-mentioned filler, it can effectively improve the resistance to partial discharge in the coil end portion 54.

[0030] In addition, in this embodiment, since the second electrodeposition coating layer 1302A is not provided in the slot receiving portion 50, the insulating film 130A (first electrodeposition coating layer 1301A) in the slot receiving portion 50 is less subject to restrictions related to the desired configuration of the insulating film 130A in the coil end portion 54. As a result, the first electrodeposition coating layer 1301A can be formed so as to conform to the desired configuration of the insulating film 130A in the slot receiving portion 50. Therefore, as in this embodiment, the first electrodeposition coating layer 1301A can be formed to a desired relatively thin thickness. In this case, the conductor occupancy rate (coil space factor) in the slot 23 is preferably 63% or more, and more preferably 65% ​​or more.

[0031] In this embodiment, when the paint contains the above-mentioned filler, the relative dielectric constant of the insulating film 130A is higher in the coil end portion 54 than when the paint does not contain any of the above-mentioned filler. However, in this case, even if partial discharge occurs, the durability (lifespan) of the insulating film 130A is significantly higher than when the paint does not contain any filler (i.e., when it is only a resin component) due to the barrier effect of the above-mentioned scale-like filler (i.e., the function of preventing the progress of electrical treeing).

[0032] Next, the coil manufacturing method according to the first embodiment will be described in detail with reference to FIG. 4A and subsequent figures.

[0033] The coil manufacturing method of this embodiment first includes a preparation step of preparing a coil material before the insulating film 130A is applied and after shaping. The shaped coil material is formed, for example, by bending a linear conductor. The shaped coil material may be only partially shaped, or may be completely shaped into a form corresponding to the segment conductors 52A and 52B of the coil piece 52 shown in FIG. 2 (see FIG. 4C).

[0034] The coil manufacturing method of this embodiment includes an electrodeposition coating process in which an insulating film 130A is applied by electrodeposition coating to the coil material (hereinafter also referred to as "workpiece W") prepared in the preparation process. Note that other processes (e.g., a cleaning process, etc.) may be included between the preparation process and the electrodeposition coating process.

[0035] The target portion (portion to be coated) of the workpiece W to which the insulating film 130A is applied may be the entire workpiece W or a part of the workpiece W. In this embodiment, as an example, the target portion of the workpiece W to which the insulating film 130A is applied is substantially the entire workpiece W (a portion excluding the open-side end portion W3), and hereinafter will be simply referred to as the workpiece W.

[0036] Fig. 4A is an explanatory diagram of the outline of the first electrodeposition coating process, and Fig. 4B is an explanatory diagram of the outline of the second electrodeposition coating process. Fig. 4C is a schematic plan view showing one workpiece W. In Fig. 4A and Fig. 4B, the Z axis is defined, and the Z1 side and Z2 side along the Z direction are defined with respect to the Z axis. The Z direction corresponds to the up-down direction, and the Z1 side and Z2 side correspond to the upper side and the lower side, respectively.

[0037] The electrodeposition coating process includes a first process in which the workpiece W is deeply immersed in an electrodeposition bath 701 as shown in Fig. 4A, and a second process in which the workpiece W is shallowly immersed in the electrodeposition bath 701 as shown in Fig. 4B. The first and second processes are carried out continuously in this order.

[0038] The electrodeposition tank 701 is filled with paint. In Figures 4A and 4B, the paint filled in the electrodeposition tank 701 is shown typically by a hatched area 721. The paint is as described above.

[0039] In the electrodeposition tank 701, when a potential difference occurs between the first electrode 74 and the second electrode 76, a direct current is generated through the paint (the paint film components electrophores), and a paint film (paint film) is deposited (electrodeposited) on the surface of the workpiece W immersed in the electrodeposition tank 701. The paint film thus formed becomes the first electrodeposition coating layer 1301A and the second electrodeposition coating layer 1302A of the insulating film 130A. The first electrode 74 is directly conducted to the workpiece W, the second electrode 76 is disposed in the electrodeposition tank 701, and a direct current power source (rectifier) ​​78 is electrically connected between the first electrode 74 and the second electrode 76. In addition, during the first step, the paint in the electrodeposition tank 701 has a flow. For example, during the first step, the paint is supplied to the electrodeposition tank 701 from a piping (not shown) on the supply side and discharged from the discharge side. In this case, the paint is circulated through the electrodeposition tank 701.

[0040] In the first step, as shown in Fig. 4A, a portion W1 (see Fig. 4C) of the workpiece W that will become the coil end portion 54 and a portion W2 (see Fig. 4C) that will become the slot-receiving portion 50 are immersed in an electrodeposition bath 701. In the electrodeposition bath 701, the second electrode 76 extends in the Z direction so as to face the portion W1 that will become the coil end portion 54 and the portion W2 that will become the slot-receiving portion 50. In this manner, the workpiece W is electrodeposited in the electrodeposition bath 701 with the above-mentioned first electrodeposition coating layer 1301A on the portion W1 that will become the coil end portion 54 and the portion W2 that will become the slot-receiving portion 50.

[0041] In the second step, as shown in FIG. 4B, of the workpiece W, only the portion W1 (see FIG. 4C) that will become the coil end portion 54 and the portion W2 (see FIG. 4C) that will become the slot receiving portion 50 are immersed. In the electrodeposition bath 701, the second electrode 76 extends in the Z direction so as to face the portion W1 that will become the coil end portion 54. In this manner, the above-mentioned second electrodeposition coating layer 1302A is electrodeposited only on the portion W1 of the workpiece W that will become the coil end portion 54. However, in a modified example, the paint may also be electrodeposited on a part of the portion W2 (a part adjacent to the portion W1), or may not be electrodeposited on a part of the portion W1 (a part adjacent to the portion W2). That is, when the workpiece W is immersed in the electrodeposition bath 701, the liquid level of the paint may be slightly shifted from the boundary position between the portion W1 that will become the coil end portion 54 and the portion W2 that will become the slot receiving portion 50.

[0042] In this embodiment, as described above, the second step is performed continuously following the first step. In this case, the second step is performed before the first electrodeposition coating layer 1301A electrochemically coated in the first step is completely cured. For example, the second step may be performed immediately after the first step, or may be performed continuously in a manner in which only the immersion depth is changed while maintaining the immersion state. In this case, even though the first electrodeposition coating layer 1301A is an insulator, the paint can be deposited on the surface of the first electrodeposition coating layer 1301A of the workpiece W (i.e., the second electrodeposition coating layer 1302A can be appropriately formed). In addition, when the first electrodeposition coating layer 1301A is formed with a relatively thin film thickness as described above, the resistance of the first electrodeposition coating layer 1301A is relatively small, so that the paint can be deposited on the surface of the first electrodeposition coating layer 1301A of the workpiece W.

[0043] In this embodiment, as described above, the second step is performed consecutively following the first step using the same electrodeposition tank 701 as the first step, so that the second electrodeposition coating layer 1302A can be deposited on the first electrodeposition coating layer 1301A. However, in a modified example, the second step may be performed using an electrodeposition tank different from that used in the first step. In this case, the paint in each electrodeposition tank is the same.

[0044] Thus, according to this embodiment, the electrodeposition coating process includes a first step of forming the first electrodeposition coating layer 1301 A, followed by a second step of forming the second electrodeposition coating layer 1302 A. This makes it possible to manufacture the above-mentioned coil piece 52 having the first electrodeposition coating layer 1301A in the slot accommodating portion 50 and the first electrodeposition coating layer 1301A and the second electrodeposition coating layer 1302A in the coil end portion 54.

[0045] However, when the first step is performed after the second step, the second electrodeposition coating layer 1302A is applied only to the coil end portion 54 out of the coil end portion 54 and the slot-receiving portion 50, so that in the subsequent first step, it becomes difficult to apply the relatively thick first electrodeposition coating layer 1301A to the coil end portion 54. This is because, as described above in the section "Problems to be Solved by the Invention", when the first step is performed after the second step, the potential difference between the paint and the coil end portion 54 on which the second electrodeposition coating layer 1302A has already been formed is likely to be smaller than the potential difference between the paint and the slot-receiving portion 50 without the second electrodeposition coating layer 1302A in the electrodeposition bath 701 in the first step. Furthermore, when the first step is performed after the second step, in order to ensure a significant film thickness difference (film thickness difference due to the relatively thick first electrocoat layer 1301A), a long first step is required, which may result in the film thickness of the slot accommodating portion 50 (the thickness of the first electrocoat layer 1301A) becoming unnecessarily large, and may result in a decrease in the space factor of the conductor in the slot 23.

[0046] On the other hand, when the first step is performed before the second step, the film thickness difference between the coil end portion 54 and the slot-receiving portion 50 is substantially the thickness of the second electrocoating layer 1302A applied only to the coil end portion 54 by the second step. In this case, a significant film thickness difference of the insulating film 130A between the coil end portion 54 and the slot-receiving portion 50 can be easily ensured by simply forming the second electrocoating layer 1302A in the second step. Even if the time of the second step is relatively long in order to make the second electrocoating layer 1302A relatively thick (i.e., to make the film thickness difference relatively large), the second electrocoating layer 1302A is not applied to the slot-receiving portion 50, so there is no risk of a decrease in the space factor of the conductor in the slot 23. In this way, according to this embodiment, it is possible to ensure a significant film thickness difference of the insulating film 130A between the coil end portion 54 and the slot-receiving portion 50 by electrocoating.

[0047] In this embodiment, the coating ratio between the thickness t1 of the first electrodeposition coating layer 1301A (see FIG. 3B) and the thickness t2 of the second electrodeposition coating layer 1302A (see FIG. 3B) may be appropriately determined according to the required motor specifications. For example, the coating ratio between the thickness t1 of the first electrodeposition coating layer 1301A and the thickness t2 of the second electrodeposition coating layer 1302A is 0.5:9.5 to 9.5:0.5, which makes it possible to easily change the quality characteristics and cost characteristics.

[0048] Here, in the electrocoating process of this embodiment, the workpiece W is immersed in the electrocoating tank 701 with its open end W3 held on the first electrode 74 side, as shown in Figs. 4A and 4B. Therefore, the first electrocoating layer 1301A and the second electrocoating layer 1302A are not applied to the open end W3 of the workpiece W. The open end W3 is a portion that forms the joint 40 of the coil pieces 52 in the form of the segment coil shown in Fig. 2. A coating for forming the insulating film 130A may be applied to the joint 40 (open end W3) of such coil pieces 52 in a process subsequent to the electrocoating process of this embodiment. For example, after assembly into the stator core 112, such a coating may be applied by any method other than electrocoating (for example, varnish application).

[0049] [Example 2] In the following description, components that may be similar to those in the first embodiment described above will be given the same reference numerals and descriptions thereof may be omitted.

[0050] First, the cross-sectional structure (insulating film 130B, etc.) of coil piece 52 according to Example 2 will be described in detail with reference to Figures 5A and 5B. Figure 5A is a schematic cross-sectional view of slot-receiving portion 50 in coil piece 52 according to Example 2, and Figure 5B is a schematic cross-sectional view of coil end portion 54 in coil piece 52 according to Example 2.

[0051] As shown in Figures 5A and 5B, the coil piece 52 is formed by covering a linear conductor (rectangular wire) 120 having a substantially rectangular cross section with an insulating film 130B. Here, the linear conductor is formed of copper, as an example. However, in modified examples, the linear conductor may be formed of other conductive materials such as iron or aluminum. Furthermore, the cross-sectional shape of the linear conductor may be other than rectangular.

[0052] In this embodiment, the insulating film 130B is formed in different manners for the slot-accommodating portion 50 and the coil end portion 54. Specifically, the insulating film 130B in the slot-accommodating portion 50 has a first electrodeposition coating layer 1301B, whereas the insulating film 130B in the coil end portion 54 has a first electrodeposition coating layer 1301B and a second electrodeposition coating layer 1302B. In this embodiment, the insulating film 130B in the slot-accommodating portion 50 is made of the first electrodeposition coating layer 1301B, but may include other layers (layers different from the second electrodeposition coating layer 1302B). Similarly, in this embodiment, the insulating film 130B in the coil end portion 54 is made of the first electrodeposition coating layer 1301B and the second electrodeposition coating layer 1302B, but may include other layers.

[0053] Furthermore, in this embodiment, the second electrodeposition coating layer 1302B is formed outside the first electrodeposition coating layer 1301B in the coil end portion 54. That is, in the coil end portion 54, the first electrodeposition coating layer 1301B is provided in a manner in which it contacts the linear conductor 120, similar to the slot accommodating portion 50. However, in a modified example, the second electrodeposition coating layer 1302B may be formed inside the first electrodeposition coating layer 1301B in the coil end portion 54 (i.e., in a manner in which it contacts the linear conductor 120).

[0054] The first electrodeposition coating layer 1301B is a layer formed by electrodeposition coating with a first paint. The first paint may be an insulating paint containing a polyamide-imide resin or a polyimide resin, or an insulating paint containing an epoxy resin.

[0055] The second electrodeposition coating layer 1302B is a layer formed by electrodeposition coating with a second paint. The second paint contains at least one of a first filler having a function of lowering the relative dielectric constant of the insulating film 130B and a second filler having a function of increasing the resistance of the insulating film 130B to partial discharge. The second paint has the same resin component as the first paint. For example, the second paint may be the first paint to which at least one of the first filler and the second filler has been added.

[0056] The first filler is a material with a low relative dielectric constant, and may be, for example, a bubble-containing capsule filler, a fluorine-based resin PTFE (polytetrafluoroethylene) particle, or the like. The bubble-containing capsule may be in the form of a gas sealed in a capsule of, for example, about 10 μm. The type of gas sealed in the capsule is arbitrary.

[0057] The second filler is a material having resistance to discharge, and may be, for example, flaky mica particles, flaky silica particles, or the like. Such a second filler also has the function of increasing the creepage distance.

[0058] The second paint preferably contains both the first filler and the second filler, which can achieve both a function of lowering the relative dielectric constant of the insulating film 130B and a function of increasing the resistance of the insulating film 130B to partial discharge.

[0059] Hereinafter, the filler contained in the second coating material will be simply referred to as a filler unless there is a particular distinction between the first filler and the second filler.

[0060] Incidentally, in the coil end portions 54 of the coil pieces 52, from the viewpoint of improving the insulation between different phases (i.e., from the viewpoint of increasing the inception voltage of partial discharge), it is desirable that the insulating film 130B has a relatively low relative dielectric constant and a relatively large thickness. Also, it is desirable that the coil end portions 54 have a relatively high resistance to partial discharge (a property that makes it difficult to deteriorate even if a partial discharge phenomenon occurs).

[0061] On the other hand, in the slot-accommodated portion 50 where the coil piece 52 is accommodated in the slot 23, it is desirable that the insulating film 130B be relatively thin from the viewpoint of increasing the conductor occupancy rate (coil space factor) in the slot 23. Also, in the slot-accommodated portion 50, it is desirable that the insulating film 130B have a low filler content (the above-mentioned first filler and second filler) from the viewpoint of reducing costs. Also, in the slot-accommodated portion 50, unlike the coil end portion 54, problems related to partial discharge are unlikely to occur, so there is little need to make the relative dielectric constant of the insulating film 130B as low as in the coil end portion 54.

[0062] In this respect, in the present embodiment, the coil piece 52 can have a relatively large thickness in the coil end portion 54 because the insulating film 130B has the second electrocoating layer 1302B in addition to the first electrocoating layer 1301B. In particular, in the present embodiment, the second electrocoating layer 1302B is not provided in the slot receiving portion 50, and can be formed to a desired thickness without being restricted by the conductor occupancy rate in the slot receiving portion 50. As a result, the second electrocoating layer 1302B formed to a desired thickness can effectively improve the insulation in the coil end portion 54. Furthermore, when the second electrocoating layer 1302B contains the first filler, the relative dielectric constant of the insulating film 130B can be lowered in the coil end portion 54, and the insulation in the coil end portion 54 can be further effectively improved. In this case, the content of the first filler in the second paint may be adjusted so that the relative dielectric constant of the insulating film 130B in the coil end portion 54 is preferably 2.0 to 3.2, and more preferably 2.2 to 3.0. Furthermore, when the second electrodeposition coating layer 1302B contains the second filler, the resistance to partial discharge in the coil end portion 54 can be effectively improved.

[0063] In addition, in this embodiment, since the second electrodeposition coating layer 1302B is not provided in the slot receiving portion 50, the insulating film 130B (first electrodeposition coating layer 1301B) in the slot receiving portion 50 is less subject to restrictions related to the desired configuration of the insulating film 130B in the coil end portion 54. As a result, the first electrodeposition coating layer 1301B can be formed so as to conform to the desired configuration of the insulating film 130B in the slot receiving portion 50. Therefore, as in this embodiment, the first electrodeposition coating layer 1301B can be formed only with the first paint containing no filler, and can be formed to a desired relatively thin thickness. In this case, the occupancy rate of the conductor in the slot 23 (coil space factor) is preferably 63% or more, and more preferably 65% ​​or more. By forming the insulating film 130B (first electrodeposition coating layer 1301B) in the slot-receiving portion 50 only with the first paint containing no filler, it is possible to improve the electrical characteristics such as the breakdown voltage of the insulating film 130B in the slot-receiving portion 50 and to improve the adhesion between the insulating film 130B and the linear conductor 120, as compared to the case where the first electrodeposition coating layer 1301B is formed with a paint containing the first filler. Furthermore, in this embodiment, the first paint does not contain a relatively expensive filler, which allows for cost reduction.

[0064] In this embodiment, when the second paint contains the second filler but not the first filler, the relative dielectric constant of the insulating film 130B is higher in the coil end portion 54 than when the second paint contains no filler at all. However, in this case, even if partial discharge occurs, the durability (lifespan) of the insulating film 130B is significantly higher than when the second paint does not contain any filler (i.e., when it is only a resin component) due to the barrier effect of the scaly second filler (i.e., the function of preventing the progress of electrical treeing). In addition, if there is no defect in the insulating film, the relationship of dielectric breakdown voltage>partial discharge inception voltage is basically satisfied. In this embodiment, the following relationship is satisfied. Breakdown voltage of second filler layer > breakdown voltage of first filler layer > onset voltage of first filler layer > onset voltage of second filler layer Here, the first filler layer corresponds to the second electrocoating layer 1302B when the second paint contains only the first filler, and the second filler layer corresponds to the second electrocoating layer 1302B when the second paint contains only the second filler.

[0065] Next, a coil manufacturing method according to the second embodiment will be described in detail with reference to FIG. 6A and subsequent figures.

[0066] The coil manufacturing method of this embodiment first includes a preparation step of preparing a coil material before the insulating film 130B is applied and after molding. The preparation step is the same as that of the first embodiment described above.

[0067] The coil manufacturing method of this embodiment includes an electrodeposition coating process in which the insulating film 130B is applied to the coil material (workpiece W) prepared in the preparation process by electrodeposition coating. Note that other processes (e.g., a cleaning process, etc.) may be included between the preparation process and the electrodeposition coating process.

[0068] The target portion (coated portion) of the workpiece W to which the insulating film 130B is applied may be the entire workpiece W or a part of the workpiece W. In this embodiment, as an example, the target portion of the workpiece W to which the insulating film 130B is applied is substantially the entire workpiece W (a portion excluding the open-side end portion W3), and hereinafter will be simply referred to as the workpiece W.

[0069] FIG. 6A is an explanatory diagram showing an overview of the first electrodeposition coating step, and FIG. 6B is an explanatory diagram showing an overview of the second electrodeposition coating step.

[0070] The electrodeposition coating process includes a first step of immersing the workpiece W in a first electrodeposition bath 701B as shown in Fig. 6A, and a second step of immersing the workpiece W in a second electrodeposition bath 702B as shown in Fig. 6B. The first and second steps are carried out continuously in this order.

[0071] The first electrodeposition tank 701B is filled with a first paint. In Fig. 6A, the paint filled in the first electrodeposition tank 701B is shown typically by a hatched area 721B. The first paint is as described above.

[0072] In the first electrodeposition tank 701B, when a potential difference occurs between the first electrode 74 and the second electrode 76A, a direct current is generated through the first paint (the coating film components electrophores), and a film (coating film) of the first paint is deposited (electrodeposited) on the surface of the workpiece W immersed in the first electrodeposition tank 701B. The film of the first paint thus formed becomes the first electrodeposition coating layer 1301B of the insulating film 130B. The first electrode 74 is directly conducted to the workpiece W, the second electrode 76A is disposed in the first electrodeposition tank 701B, and a direct current power source (rectifier) ​​78 is electrically connected between the first electrode 74 and the second electrode 76A. In addition, during the first process, the first paint in the first electrodeposition tank 701B has a flow. For example, during the first process, the first paint is supplied to the first electrodeposition tank 701B from a piping (not shown) on the supply side and discharged from the discharge side. In this case, the first paint is circulated through the first electrodeposition tank 701B.

[0073] In the first electrodeposition bath 701B, the workpiece W is immersed at a portion W1 (see FIG. 4C) that will become the coil end portion 54 and a portion W2 (see FIG. 4C) that will become the slot-receiving portion 50. In the first electrodeposition bath 701B, the second electrode 76A extends in the Z direction so as to face the portion W1 that will become the coil end portion 54 and the portion W2 that will become the slot-receiving portion 50. In this manner, the workpiece W is electrodeposited with the above-mentioned first electrodeposition coating layer 1301B in the first electrodeposition bath 701B at the portion W1 that will become the coil end portion 54 and the portion W2 that will become the slot-receiving portion 50.

[0074] The second electrodeposition tank 702B is filled with the second paint. In Fig. 6B, the paint filled in the second electrodeposition tank 702B is shown typically by the hatched area 722B. The second paint is as described above.

[0075] In the second electrodeposition tank 702B, when a potential difference occurs between the first electrode 74 and the second electrode 76B, a direct current is generated through the second paint (the coating film components electrophores), and a film (coating film) of the second paint is deposited (electrodeposited) on the surface of the workpiece W (the surface of the first electrodeposition coating layer 1301B) immersed in the second electrodeposition tank 702B. The film of the second paint thus formed becomes the second electrodeposition coating layer 1302B of the insulating film 130B. The first electrode 74 is directly conducted to the workpiece W, the second electrode 76B is disposed in the second electrodeposition tank 702B, and a direct current power supply (rectifier) ​​78 is electrically connected between the first electrode 74 and the second electrode 76B. In addition, during the second process, the second paint in the second electrodeposition tank 702B has a flow. For example, during the second step, the second coating material is supplied to the second electrodeposition tank 702B from a supply pipe (not shown) and discharged from the discharge pipe. In this case, the second coating material is circulated through the second electrodeposition tank 702B.

[0076] In the second electrodeposition bath 702B, only the portion W1 of the workpiece W that is to become the coil end portion 54 (see FIG. 4C) and the portion W2 that is to become the slot receiving portion 50 (see FIG. 4C) is immersed. In the second electrodeposition bath 702B, the second electrode 76B extends in the Z direction so as to face the portion W1 that is to become the coil end portion 54. In this manner, the workpiece W is electrodeposited with the above-mentioned second electrodeposition coating layer 1302B only on the portion W1 that is to become the coil end portion 54. However, in a modified example, the second paint may also be electrodeposited on a part of the portion W2 (a part adjacent to the portion W1), or may not be electrodeposited on a part of the portion W1 (a part adjacent to the portion W2). That is, when the workpiece W is immersed in the second electrodeposition bath 702B, the liquid level of the second paint may be slightly shifted from the boundary position between the portion W1 that is to become the coil end portion 54 and the portion W2 that is to become the slot receiving portion 50.

[0077] In this embodiment, as described above, the second step is performed continuously following the first step. In this case, the second step is performed before the first electrodeposition coating layer 1301B, which is electrodeposition coated in the first step, is completely cured. For example, the second step is performed immediately after the first step is performed. In this case, even though the first electrodeposition coating layer 1301B is an insulator, the second paint can be deposited on the surface of the first electrodeposition coating layer 1301B of the workpiece W. In addition, when the first electrodeposition coating layer 1301B is formed with a relatively thin film thickness as described above, the resistance of the first electrodeposition coating layer 1301B is relatively small, so that the second paint can be deposited on the surface of the first electrodeposition coating layer 1301B of the workpiece W.

[0078] In this embodiment, as described above, the second step is performed continuously following the first step, which allows the second electrodeposition coating layer 1302B to be deposited on the first electrodeposition coating layer 1301B, but there is a possibility that the first coating material may be mixed into the second coating material. However, according to this embodiment, the first coating material can have the same resin component as the second coating material, so that no inconvenience (such as coating defects) occurs due to the mixing of the first coating material. Furthermore, by making the resin components of the first coating material and the second coating material the same, the adhesion between the first electrodeposition coating layer 1301B and the second electrodeposition coating layer 1302B can be improved.

[0079] In this embodiment, the first electrodeposition tank 701B and the second electrodeposition tank 702B may be provided adjacent to each other so that the second step can be performed immediately following the first step. The first electrode 74 and the DC power supply (rectifier) ​​78 may be shared between the first step and the second step. In this case, the first step can be moved to the second step without releasing the connection between the first electrode 74 and the workpiece W, so that the time from the completion of the first step to the start of the second step can be effectively shortened. Furthermore, the equipment configuration can be simplified by sharing the first electrode 74 and the DC power supply (rectifier) ​​78.

[0080] Thus, according to this embodiment, the electrodeposition coating process includes a first step of forming the first electrodeposition coating layer 1301B, followed by a second step of forming the second electrodeposition coating layer 1302B. This makes it possible to manufacture the above-mentioned coil piece 52 having the first electrodeposition coating layer 1301B in the slot accommodating portion 50 and the first electrodeposition coating layer 1301B and the second electrodeposition coating layer 1302B in the coil end portion 54.

[0081] Furthermore, according to this embodiment, since the first step is performed before the second step, the first electrodeposition coating layer 1301B that does not contain filler can be formed on the surface of the linear conductor 120. This makes it possible to effectively improve the adhesion between the insulating film 130B and the linear conductor 120, compared to the case where the first step is performed after the second step.

[0082] However, when the first step is performed after the second step, the second electrodeposition coating layer 1302B is applied only to the coil end portion 54 out of the coil end portion 54 and the slot-receiving portion 50, so that in the subsequent first step, it becomes difficult to apply the relatively thick first electrodeposition coating layer 1301B to the coil end portion 54. This is because, as described above in the section "Problems to be Solved by the Invention", when the first step is performed after the second step, in the first electrodeposition bath 701B, the potential difference between the coil end portion 54 on which the second electrodeposition coating layer 1302B has already been formed and the first paint is likely to be smaller than the potential difference between the slot-receiving portion 50 without the second electrodeposition coating layer 1302B and the first paint. Furthermore, when the first step is performed after the second step, in order to ensure a significant film thickness difference (film thickness difference due to the relatively thick first electrocoat layer 1301B), a long first step is required, which may result in the film thickness of the slot accommodating portion 50 (the thickness of the first electrocoat layer 1301B) becoming unnecessarily large, and may result in a decrease in the space factor of the conductor in the slot 23.

[0083] On the other hand, when the first step is performed before the second step, the film thickness difference between the coil end portion 54 and the slot-receiving portion 50 is substantially the thickness of the second electrocoating layer 1302B applied only to the coil end portion 54 by the second step. In this case, a significant film thickness difference of the insulating film 130B between the coil end portion 54 and the slot-receiving portion 50 can be easily ensured by simply forming the second electrocoating layer 1302B in the second step. Even if the time of the second step is relatively long in order to make the second electrocoating layer 1302B relatively thick (i.e., to make the film thickness difference relatively large), the second electrocoating layer 1302B is not applied to the slot-receiving portion 50, so there is no risk of a decrease in the space factor of the conductor in the slot 23. In this way, according to this embodiment, it is possible to ensure a significant film thickness difference of the insulating film 130B between the coil end portion 54 and the slot-receiving portion 50 by electrocoating.

[0084] In this embodiment, the coating ratio between the thickness t1 of the first electrodeposition coating layer 1301B (see FIG. 5B) made of the first paint and the thickness t2 of the second electrodeposition coating layer 1302B (see FIG. 5B) made of the second paint may be appropriately determined according to the required motor specifications. For example, the coating ratio between the thickness t1 of the first electrodeposition coating layer 1301B and the thickness t2 of the second electrodeposition coating layer 1302B is 0.5:9.5 to 9.5:0.5, which makes it possible to easily change the quality characteristics and cost characteristics.

[0085] In the above-mentioned embodiment, the second electrodeposition coating layer 1302B contains a filler, and therefore tends to reduce the formability of the coil pieces 52 more than the first electrodeposition coating layer 1301B. However, in this embodiment, as described above, the second electrodeposition coating layer 1302B is applied to the workpiece W in a state in which the portion related to the coil end portion 54 has been formed, and therefore the reduction in formability of the coil pieces 52 caused by the second electrodeposition coating layer 1302B does not cause any substantial inconvenience.

[0086] Here, in the electrocoating process of this embodiment, the workpiece W is immersed in the first electrocoating bath 701B and the second electrocoating bath 702B with its open end W3 held on the first electrode 74 side, as shown in Figs. 6A and 6B. Therefore, the first electrocoating layer 1301B and the second electrocoating layer 1302B are not applied to the open end W3 of the workpiece W. The open end W3 is a portion that forms the joint 40 of the coil pieces 52 in the form of the segment coil shown in Fig. 2. A coating for forming the insulating film 130B may be applied to the joint 40 (open end W3) of such coil pieces 52 in a process subsequent to the electrocoating process of this embodiment. For example, such a coating may be applied by any method (e.g., varnish application) other than electrocoating after incorporation into the stator core 112.

[0087] Next, a preferred modification applicable to the above-described embodiment (hereinafter, referred to as "this modification") will be described.

[0088] In the above embodiment, the first coating does not contain any filler, but the first coating may contain a significantly less amount of filler than the second coating, or the same or more amount of filler than the second coating, in which case the filler contained in the first coating may be the same as or different from the filler contained in the second coating.

[0089] In this modification, the first paint contains the second filler from the viewpoint of enhancing the dielectric breakdown resistance performance of the insulating film 130B (i.e., from the viewpoint of preventing the progress of electrical treeing and increasing the creepage distance) in the slot-accommodating portion 50. In this case, the first paint may contain only the second filler out of the first and second fillers, or may contain a significantly larger amount of the second filler than the first filler.

[0090] In this modified example, the filler contained in the second paint may be adjusted according to the filler contained in the first paint. For example, when the first paint contains the second filler, the second paint may contain only the first filler out of the first and second fillers, or may contain a significantly larger amount of the first filler than the second filler.

[0091] In this modification (or in the above-described embodiment), the first paint may contain a filler with high thermal conductivity (i.e., a heat dissipation filler) such as alumina in order to improve the heat dissipation of the slot receiving portion 50. Note that alumina has high electrical insulation properties, so the insulation properties of the insulating film 130B are not impaired. High-purity alumina spherical particles may be used as the alumina filler.

[0092] This modification can also provide the same effects as the above-described embodiment. In addition, this modification can improve the dielectric breakdown resistance of the insulating film 130B in the slot-receiving portion 50. Furthermore, when the first paint contains a heat dissipating filler, the heat dissipation of the slot-receiving portion 50 can be further improved.

[0093] Although each embodiment has been described in detail above, it is not limited to a specific embodiment, and various modifications and changes are possible within the scope of the claims. It is also possible to combine all or a plurality of the components of the above-mentioned embodiments. Furthermore, among the effects of each embodiment, the effects related to the dependent claims are additional effects that are distinguished from the generic concept (independent claim). [Explanation of symbols]

[0094] 10 stator (stator for rotating electric machine), 23 slot, 130A, 130B insulating film, 114 stator coil (coil), 50 slot receiving portion, 54 coil end portion, 1301A, 1301B first electrodeposition coating layer (first insulating layer), 1302A, 1302B second electrodeposition coating layer (second insulating layer), 701 electrodeposition bath (common electrodeposition bath), 701B first electrodeposition bath, 702B second electrodeposition bath

Claims

1. A method for manufacturing a coil having an insulating film including a first insulating layer and a second insulating layer, comprising the steps of: a preparation step of preparing a coil material before the insulating film is applied and after molding; a first electrodeposition coating step of forming the first insulating layer by electrodeposition coating the coil end portion and the slot-receiving portion of the coil blank; a second electrodeposition coating step that is executed after the first electrodeposition coating step, and that forms the second insulating layer on the outside of the first insulating layer in the coil end portion of the coil material by electrodeposition coating only the coil end portion of the coil material and the slot accommodation portion, The manufacturing method, wherein the first electrodeposition coating step and the second electrodeposition coating step are carried out in a common electrodeposition tank.

2. The manufacturing method according to claim 1 , wherein the coil material is in the form of a U-shaped segment coil.

3. In the first electrodeposition coating step and the second electrodeposition coating step, the coil material is electrodeposited while the U-shaped open end portion is held, The manufacturing method according to claim 2 , further comprising the step of applying a coating to form the insulating film to the open end of the coil blank after the second electrocoating step.

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