JP7600727B2 - Rotating electric machine stator - Google Patents

Description

This disclosure relates to a stator for a rotating electric machine.

A technique is known in which the insulating material (resin material) of the insulating film is different between the coil end portion of the coil material and the slot accommodation portion. In this technique, an electrodeposition coating layer of polyamide-imide resin or polyimide resin is applied on top of an electrodeposition coating layer of epoxy resin to the coil end portion, and only an electrodeposition coating layer of polyamide-imide resin or polyimide resin is applied to the slot accommodation portion.

JP 2012-235648 A

However, in the conventional technology described above, the resin material of the insulating film is simply changed, making it difficult to provide an electrocoat layer with suitable characteristics and thickness for each of the coil end portion and the slot accommodating portion.

Therefore, in one aspect, the present disclosure aims to realize an insulating film that has suitable characteristics and thickness for each of the coil end portion and the slot accommodating portion.

According to one aspect, there is provided a stator for a rotating electric machine, in which a coil having an insulating film is wound around a stator core,
The coil has a slot receiving portion to be inserted into the slot of the stator core and a coil end portion,
the insulating film includes a first insulating layer and a second insulating layer;
The first insulating layer is provided in the slot-accommodating portion and the coil end portion,
the second insulating layer is provided only in the coil end portion of the slot accommodating portion and the coil end portion, and is provided outside the first insulating layer;
The second insulating layer has a higher partial discharge inception voltage or dielectric breakdown voltage than the first insulating layer, thereby providing a stator for a rotating electric machine.

In one aspect, the present disclosure makes it possible to realize an insulating film with suitable characteristics and thickness for each of the coil end portion and the slot accommodating portion.

FIG. 2 is a cross-sectional view taken along the axial direction of the stator. FIG. 2 is a three-view diagram of one coil piece. 4 is a schematic cross-sectional view of a slot-receiving portion of a coil piece according to the first embodiment. FIG. 3 is a schematic cross-sectional view of a transition portion (coil end portion) of a coil piece according to the first embodiment. FIG. FIG. 2 is an explanatory diagram of an overview of a first electrodeposition coating step according to Example 1. FIG. 2 is an explanatory diagram of an overview of the second electrodeposition coating step according to Example 1. FIG. 2 is a schematic plan view showing one workpiece according to the first embodiment. 11 is a schematic cross-sectional view of a slot-receiving portion of a coil piece according to a second embodiment. FIG. 11 is a schematic cross-sectional view of a transition portion (coil end portion) of a coil piece according to a second embodiment. FIG. FIG. 10 is an explanatory diagram of an overview of a first electrodeposition coating process according to Example 2. FIG. 11 is an explanatory diagram of an overview of a second electrodeposition coating process according to Example 2.

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

Below, we will first explain the stator 10 for a rotating electric machine of this embodiment, and then explain the coil manufacturing method.

Figure 1 is a cross-sectional view along the axial direction of the stator 10 with the coil pieces 52 assembled to the stator core 112. Note that Figure 1 also shows an enlarged view of part Q2 in the figure. Figure 2 is a three-view diagram of one of the multiple coil pieces 52.

The stator coil 114 includes 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 coil 114 is star-connected. However, the connection mode of the stator coil 114 may be changed as appropriate depending on the required motor characteristics, etc. For example, the stator coil 114 may be delta-connected instead of star-connected.

Each phase coil of the stator coil 114 is formed by joining multiple coil pieces 52. The coil pieces 52 are in the form of segment coils (segment conductors) in which the phase coil is divided into units that are easy to assemble (for example, units that can be inserted into two slots 23).

One coil piece 52 is formed by combining a segment conductor 52A on one side in the axial direction with a segment conductor 52B on the other side in the axial direction.

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

In one slot 23, multiple slot-accommodated portions 50 of the coil pieces 52 shown in FIG. 1 are inserted side by side in the radial direction. Therefore, multiple coil end portions 54 extending in the circumferential direction are radially arranged at both axial ends of the stator core 112. 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).

In the example shown in FIG. 2, the segment conductors 52A and 52B are each capable of coupling one of the slot accommodating portions 50 on both circumferential sides, while the other is offset in a direction away from each other by one layer in the radial direction. Specifically, the segment conductors 52A and 52B each have offset portions 521A and 521B at the top of the opposing surface 42, and the offset portions 521A and 521B realize offsets in opposite directions in the radial direction.

The coil pieces 52 are wound around the stator core 112 in a lap winding configuration. In this case, the segment conductors 52A and 52B constituting one coil piece 52 are joined at the joint portions 40 (i.e., the open ends) of the slot accommodation portions 50 on one side of the slot accommodation portions 50 on both circumferential sides, as shown in FIG. 2. In this case, the slot accommodation portion 50 on the other side is joined to the other 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 come into surface contact with each other, and the joint portions 40 are joined together with the opposing surfaces 42 overlapping each other.

1 and 2 show the stator core 112 and the stator coil 114 of a specific structure, but the structure of the stator core 112 and the stator coil 114 is arbitrary as long as the stator coil 114 has insulating films 130A and 130B. Furthermore, the coil pieces in the form of segment coils are not limited to being joined within the slots 23 of the stator core 112 like the coil pieces 52, but may be in other forms, such as being joined at one axial end. Furthermore, 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, we will explain the coil insulating film configuration and coil manufacturing method for each example.

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

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. Also, the cross-sectional shape of the linear conductor may be other than rectangular.

In this embodiment, the insulating film 130A is formed in different manners for the slot accommodation portion 50 and the coil end portion 54. Specifically, the insulating film 130A in the slot accommodation portion 50 has a first electrocoating layer 1301A, whereas the insulating film 130A in the coil end portion 54 has a first electrocoating layer 1301A and a second electrocoating layer 1302A. In this embodiment, the insulating film 130A in the slot accommodation portion 50 is made of the first electrocoating layer 1301A, but may include other layers (layers different from the second electrocoating layer 1302A). Similarly, in this embodiment, the insulating film 130A in the coil end portion 54 is made of the first electrocoating layer 1301A and the second electrocoating layer 1302A, but may include other layers.

In addition, in this embodiment, in the coil end portion 54, the second electrocoating layer 1302A is formed outside the first electrocoating layer 1301A. That is, in the coil end portion 54, the first electrocoating layer 1301A is provided in a manner in which it contacts the linear conductor 120, similar to the slot accommodation portion 50.

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

The second electrocoating layer 1302A is a layer formed by electrocoating with paint. The paint is the same as the paint used to form the first electrocoating layer 1301A.

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

In the coil pieces 52, it is desirable that the insulating film 130A be relatively thick in the coil end portions 54 in order to improve the insulation between different phases (i.e., to increase the inception voltage of partial discharge). It is also desirable that the coil end portions 54 have a relatively high resistance to partial discharge (the characteristic of being less susceptible to deterioration even when a partial discharge phenomenon occurs).

On the other hand, in the coil piece 52, in the slot receiving portion 50 that is received in the slot 23, it is desirable for the insulating film 130A to be relatively thin in order to increase the conductor occupancy rate (coil space factor) within the slot 23.

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 electrocoating layer 1302A in addition to the first electrocoating layer 1301A. In particular, in this embodiment, the second electrocoating layer 1302A is not provided in the slot accommodating portion 50, so it can be formed to the desired thickness without being restricted by the conductor occupancy rate in the slot accommodating portion 50. As a result, the second electrocoating layer 1302A formed to the desired thickness can effectively improve the insulation in the coil end portion 54. In addition, when the paint contains the above-mentioned filler, it can effectively improve the resistance to partial discharge in the coil end portion 54.

In addition, in this embodiment, since the second electrocoating layer 1302A is not provided in the slot accommodating portion 50, the insulating film 130A (first electrocoating layer 1301A) in the slot accommodating 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 electrocoating layer 1301A can be formed to match the desired configuration of the insulating film 130A in the slot accommodating portion 50. Therefore, as in this embodiment, the first electrocoating 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.

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 progression of electrical trees).

Next, the coil manufacturing method according to Example 1 will be described in detail with reference to Figure 4A and subsequent figures.

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

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.

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 (excluding the open end W3), and hereinafter will be referred to simply as the workpiece W.

Figure 4A is an explanatory diagram of the outline of the first electrodeposition coating process, and Figure 4B is an explanatory diagram of the outline of the second electrodeposition coating process. Figure 4C is a schematic plan view showing one workpiece W. In Figures 4A and 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 lower side, respectively.

The electrocoating process includes a first process in which the workpiece W is deeply immersed in the electrocoating tank 701 as shown in FIG. 4A, and a second process in which the workpiece W is shallowly immersed in the electrocoating tank 701 as shown in FIG. 4B. The first and second processes are carried out continuously in this order.

The electrodeposition tank 701 is filled with paint. In Fig. 4A and Fig. 4B, the paint filled in the electrodeposition tank 701 is shown diagrammatically by the hatched area 721. The paint is as described above.

When a potential difference occurs between the first electrode 74 and the second electrode 76 in the electrodeposition tank 701, a direct current is generated through the paint (the coating film components electrophores), and a paint film (coating 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 process, the paint in the electrodeposition tank 701 has a flow. For example, during the first process, the paint is supplied to the electrodeposition tank 701 from a supply side pipe (not shown) and discharged from the discharge side. In this case, the paint is circulated through the electrodeposition tank 701.

In the first step, as shown in FIG. 4A, the workpiece W is immersed in an electrodeposition bath 701 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 accommodating portion 50. 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 accommodating portion 50. In this way, the workpiece W is electrodeposited in the electrodeposition bath 701 with the first electrodeposition coating layer 1301A described above at the portion W1 that will become the coil end portion 54 and the portion W2 that will become the slot accommodating portion 50.

In the second step, as shown in FIG. 4B, the workpiece W is immersed in only the portion W1 of 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 accommodating portion 50. In the electrochemical deposition 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 way, the above-mentioned second electrochemical coating layer 1302A is electrochemically coated 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 electrochemically coated on a part of the portion W2 (a part adjacent to the portion W1), or may not be electrochemically coated on a part of the portion W1 (a part adjacent to the portion W2). In other words, when the workpiece W is immersed in the electrochemical deposition 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 accommodating portion 50.

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 electrocoating layer 1301A electrocoated 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 electrocoating layer 1301A is an insulator, the paint can be deposited on the surface of the first electrocoating layer 1301A on the workpiece W (i.e., the second electrocoating layer 1302A can be properly formed). In addition, when the first electrocoating layer 1301A is formed with a relatively thin film thickness as described above, the resistance of the first electrocoating layer 1301A is relatively small, so the paint can be deposited on the surface of the first electrocoating layer 1301A on the workpiece W.

In this embodiment, as described above, the second step is performed continuously following the first step using the same electrodeposition tank 701 as the first step, making it possible to deposit the second electrodeposition coating layer 1302A on the first electrodeposition coating layer 1301A. However, in a modified example, the second step may be performed using an electrodeposition tank different from the first step. In this case, the paint in each electrodeposition tank is the same.

Thus, according to this embodiment, the electrocoating process includes a first process of forming the first electrocoating layer 1301A, followed by a second process of forming the second electrocoating layer 1302A. This allows the above-mentioned coil piece 52 to be manufactured, which has the first electrocoating layer 1301A in the slot accommodation portion 50 and the first electrocoating layer 1301A and the second electrocoating layer 1302A in the coil end portion 54.

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 accommodating portion 50, so it becomes difficult to apply the relatively thick first electrodeposition coating layer 1301A to the coil end portion 54 in the subsequent first step. This is because, as described above in the "Problem to be Solved by the Invention" section, 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 accommodating portion 50 without the second electrodeposition coating layer 1302A in the electrodeposition bath 701 in the first step. In addition, if the first step is performed after the second step, in order to ensure a significant difference in film thickness (the difference in film thickness due to the relatively thick first electrocoating layer 1301A), the first step will require a long time, which may result in an unnecessarily large film thickness in the slot accommodating portion 50 (the thickness of the first electrocoating layer 1301A), and may result in a decrease in the space factor of the conductor in the slot 23.

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 accommodating 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 accommodating 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 accommodating 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 accommodating portion 50 by electrocoating.

In this embodiment, the coating ratio between the thickness t1 of the first electrocoating layer 1301A (see FIG. 3B) and the thickness t2 of the second electrocoating 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 electrocoating layer 1301A and the thickness t2 of the second electrocoating layer 1302A is 0.5:9.5 to 9.5:0.5, making it possible to easily change the quality characteristics and cost characteristics.

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 Figures 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 the portion that forms the joint 40 of the coil piece 52 in the form of the segment coil shown in Figure 2. A coating for forming the insulating film 130A may be applied to the joint 40 (open end W3) of such a coil piece 52 in a process subsequent to the electrocoating process of this embodiment. For example, such a coating may be applied by any method other than electrocoating (e.g., varnish application) after assembly into the stator core 112.

[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.

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-accommodating 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.

As shown in Figs. 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.

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 electrocoating layer 1301B, whereas the insulating film 130B in the coil end portion 54 has a first electrocoating layer 1301B and a second electrocoating layer 1302B. In this embodiment, the insulating film 130B in the slot accommodating portion 50 is made of the first electrocoating layer 1301B, but may include other layers (layers different from the second electrocoating layer 1302B). Similarly, in this embodiment, the insulating film 130B in the coil end portion 54 is made of the first electrocoating layer 1301B and the second electrocoating layer 1302B, but may include other layers.

In addition, in this embodiment, the second electrocoating layer 1302B is formed on the outer side of the first electrocoating layer 1301B in the coil end portion 54. That is, in the coil end portion 54, the first electrocoating layer 1301B is provided in contact with the linear conductor 120, similar to the slot accommodating portion 50. However, in a modified example, the second electrocoating layer 1302B may be formed on the inner side of the first electrocoating layer 1301B in the coil end portion 54 (i.e., in contact with the linear conductor 120).

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

The second electrocoating layer 1302B is a layer formed by electrocoating 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.

The first filler is a material with a low dielectric constant, and may be, for example, a bubble-filled capsule filler, PTFE (polytetrafluoroethylene) particles of a fluorine-based resin, or the like. The bubble-filled 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.

The second filler is a discharge-resistant material, and may be, for example, scaly mica particles, scaly silica particles, or the like. Such a second filler also has the function of increasing the creepage distance.

The second paint preferably contains both the first filler and the second filler. In this case, it is possible to achieve both the function of lowering the relative dielectric constant of the insulating film 130B and the function of increasing the resistance of the insulating film 130B to partial discharge.

In the following, when there is no particular distinction between the first filler and the second filler, the filler contained in the second paint will simply be referred to as the filler.

In the coil end portions 54 of the coil pieces 52, it is desirable that the dielectric constant of the insulating film 130B is relatively low and the thickness is relatively large 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 also desirable that the coil end portions 54 have a relatively high resistance to partial discharge (the characteristic of being less susceptible to deterioration even when a partial discharge phenomenon occurs).

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 in order to increase 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 first filler and second filler described above) in order to reduce costs. Also, in the slot-accommodated portion 50, unlike the coil end portion 54, partial discharge problems are less likely 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.

In this respect, in the present embodiment, the coil piece 52 has 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 this embodiment, the second electrocoating layer 1302B is not provided in the slot accommodating portion 50, so it can be formed to a desired thickness without being restricted by the conductor occupancy rate in the slot accommodating 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. In addition, 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, more preferably 2.2 to 3.0. In addition, when the second electrocoating layer 1302B contains the second filler, the resistance to partial discharge in the coil end portion 54 can be effectively increased.

In addition, in this embodiment, since the second electrocoating layer 1302B is not provided in the slot accommodating portion 50, the insulating film 130B (first electrocoating layer 1301B) in the slot accommodating 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 electrocoating layer 1301B can be formed to match the desired configuration of the insulating film 130B in the slot accommodating portion 50. Therefore, as in this embodiment, the first electrocoating layer 1301B can be formed only with the first paint that does not contain a filler, and can be formed to the 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. By forming the insulating film 130B (first electrocoating layer 1301B) in the slot receiving portion 50 using only the first paint that does not contain a 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, compared to when the first electrocoating layer 1301B is formed using a paint that contains the first filler. In addition, in this embodiment, since the first paint does not contain a relatively expensive filler, it is possible to reduce costs.

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 does not contain any filler. 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 established. In this embodiment, the following relationship is established.
Breakdown voltage of the second filler layer > breakdown voltage of the first filler layer > onset voltage of the first filler layer > onset voltage of the 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.

Next, the coil manufacturing method according to Example 2 will be described in detail with reference to Figure 6A and subsequent figures.

The coil manufacturing method of this embodiment first includes a preparation step of preparing the coil material before the insulating film 130B is applied and after molding. The preparation step is the same as that of the above-mentioned embodiment 1.

The coil manufacturing method of this embodiment includes an electrocoating process in which insulating film 130B is applied by electrocoating to the coil material (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 electrocoating process.

The target portion of the workpiece W to which the insulating film 130B is applied (the portion to be coated) 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 (excluding the open end W3), and hereinafter will be referred to simply as the workpiece W.

Figure 6A is an explanatory diagram of the overview of the first electrodeposition coating process, and Figure 6B is an explanatory diagram of the overview of the second electrodeposition coating process.

The electrocoating process includes a first process of immersing the workpiece W in a first electrocoating tank 701B as shown in FIG. 6A, and a second process of immersing the workpiece W in a second electrocoating tank 702B as shown in FIG. 6B. The first and second processes are carried out continuously in this order.

The first electrodeposition tank 701B is filled with the first paint. In FIG. 6A, the paint filled in the first electrodeposition tank 701B is shown diagrammatically by the hatched area 721B. The first paint is as described above.

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 formed in this way 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 supply side pipe (not shown) and discharged from the discharge side. In this case, the first paint is circulated through the first electrodeposition tank 701B.

In the first electrodeposition bath 701B, the workpiece W is immersed at 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 accommodating 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 accommodating portion 50. In this way, the workpiece W is electrocoated with the above-mentioned first electrocoating layer 1301B at the portion W1 that will become the coil end portion 54 and the portion W2 that will become the slot accommodating portion 50 in the first electrodeposition bath 701B.

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 diagrammatically by the hatched area 722B. The second paint is as described above.

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 formed in this way 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 side pipe (not shown) and discharged from the discharge side. In this case, the second coating material is circulated through the second electrodeposition tank 702B.

In the second electrodeposition bath 702B, only the portion W1 of the workpiece W that will become the coil end portion 54 (see FIG. 4C) and the portion W2 that will become the slot accommodating 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 will become the coil end portion 54. In this way, the workpiece W is electrocoated with the above-mentioned second electrocoating layer 1302B only on the portion W1 that will become the coil end portion 54. However, in a modified example, the second paint may also be electrocoated on a part of the portion W2 (a part adjacent to the portion W1), or may not be electrocoated on a part of the portion W1 (a part adjacent to the portion W2). In other words, 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 will become the coil end portion 54 and the portion W2 that will become the slot accommodating portion 50.

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 electrocoating layer 1301B electrocoated 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 electrocoating layer 1301B is an insulator, the second paint can be deposited on the surface of the first electrocoating layer 1301B on the workpiece W. Also, when the first electrocoating layer 1301B is formed with a relatively thin film thickness as described above, the resistance of the first electrocoating layer 1301B is relatively small, so the second paint can be deposited on the surface of the first electrocoating layer 1301B on the workpiece W.

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 may be mixed into the second coating. However, according to this embodiment, the first coating can have the same resin component as the second coating, so that no inconvenience (such as paint defects) due to the mixing of the first coating does not occur. In addition, by making the resin components of the first coating and the second coating the same, the adhesion between the first electrodeposition coating layer 1301B and the second electrodeposition coating layer 1302B can be improved.

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 process can be performed immediately following the first process. The first electrode 74 and the DC power supply (rectifier) 78 may be shared between the first and second processes. In this case, the first process can be moved to the second process without releasing the connection between the first electrode 74 and the workpiece W, so that the time from the completion of the first process to the start of the second process can be effectively shortened. Furthermore, the equipment configuration can be simplified by sharing the first electrode 74 and the DC power supply (rectifier) 78.

Thus, according to this embodiment, the electrocoating process includes a second step of forming the second electrocoating layer 1302B following the first step of forming the first electrocoating layer 1301B. This allows the above-mentioned coil piece 52 to be manufactured, which has the first electrocoating layer 1301B in the slot accommodation portion 50 and the first electrocoating layer 1301B and the second electrocoating layer 1302B in the coil end portion 54.

In addition, according to this embodiment, since the first step is performed before the second step, a first electrocoating layer 1301B that does not contain filler can be formed on the surface of the linear conductor 120. This effectively improves the adhesion between the insulating film 130B and the linear conductor 120 compared to when the first step is performed after the second step.

However, when the first step is performed after the second step, the second electrocoating layer 1302B is applied only to the coil end portion 54 out of the coil end portion 54 and the slot accommodating portion 50, so it becomes difficult to apply the relatively thick first electrocoating layer 1301B to the coil end portion 54 in the subsequent first step. This is because, as described above in the "Problem to be Solved by the Invention" section, when the first step is performed after the second step, the potential difference between the coil end portion 54 on which the second electrocoating layer 1302B has already been formed and the first paint in the first electrocoating tank 701B tends to be smaller than the potential difference between the slot accommodating portion 50 without the second electrocoating layer 1302B and the first paint. In addition, if the first step is performed after the second step, in order to ensure a significant difference in film thickness (the difference in film thickness due to the relatively thick first electrocoating layer 1301B), the first step will require a long time, which may result in an unnecessarily large film thickness in the slot accommodating portion 50 (the thickness of the first electrocoating layer 1301B), and may result in a decrease in the space factor of the conductor in the slot 23.

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 accommodating 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 accommodating 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 accommodating 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 accommodating portion 50 by electrocoating.

In this embodiment, the coating ratio between the thickness t1 of the first electrocoating layer 1301B (see FIG. 5B) made of the first paint and the thickness t2 of the second electrocoating 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 electrocoating layer 1301B and the thickness t2 of the second electrocoating layer 1302B is 0.5:9.5 to 9.5:0.5, making it possible to easily change the quality characteristics and cost characteristics.

In the above-mentioned embodiment, the second electrocoating layer 1302B contains a filler, and therefore tends to reduce the formability of the coil pieces 52 more than the first electrocoating layer 1301B. However, in this embodiment, as described above, the second electrocoating 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, so that the reduction in formability of the coil pieces 52 caused by the second electrocoating layer 1302B does not cause any substantial inconvenience.

In the electrocoating process of this embodiment, the workpiece W is immersed in the first electrocoating tank 701B and the second electrocoating tank 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 other than electrocoating (e.g., varnish application) after assembly into the stator core 112.

Next, we will explain a preferred variation that can be applied to the above-mentioned embodiment (hereinafter referred to as "this variation").

In the above-described embodiment, the first paint does not contain any filler, but the first paint may contain a filler in a content significantly less than the second paint or in a content equal to or greater than the second paint. In this case, the filler contained in the first paint may be the same as or different from the filler contained in the second paint.

In this modified example, in the slot accommodating portion 50, the first paint contains the second filler from the viewpoint of increasing the dielectric breakdown resistance of the insulating film 130B (i.e., from the viewpoint of preventing the progress of electrical trees and increasing the creepage distance). 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.

In this modified example, the filler contained in the second paint may be adjusted depending on the filler contained in the first paint. For example, if the first paint contains a 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.

In addition, in this modified example (or in the above-mentioned embodiment), the first paint may contain a highly heat-conductive filler (i.e., heat-dissipating filler) (an example of a third filler) such as alumina in order to improve the heat dissipation of the slot accommodating portion 50. Note that alumina has high electrical insulation properties, so it does not impair the insulation properties of the insulating film 130B. High-purity alumina spherical particles may be used as the alumina filler.

This modified example can achieve the same effects as the above-mentioned embodiment. In addition, this modified example can improve the dielectric breakdown resistance of the insulating film 130B in the slot accommodating portion 50. Furthermore, if the first paint contains a heat dissipating filler, the heat dissipation properties of the slot accommodating portion 50 can be further improved.

Although each embodiment has been described above in detail, it is not limited to the 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 superordinate concept (independent claim).
For example, in the above-described embodiment, the insulating films 130A and 130B are formed by electrodeposition coating, but a part or the whole of each of the insulating films 130A and 130B may be formed by a method other than electrodeposition coating.

10: stator (stator for rotating electric machine), 23: slot, 130A, 130B: insulating film, 114: stator coil (coil), 50: slot housing, 54: coil end, 1301A, 1301B: first electrocoat layer (first insulating layer), 1302A, 1302B: second electrocoat layer (second insulating layer), 701: electrocoat bath (common electrocoat bath), 701B: first electrocoat bath, 702B: second electrocoat bath

Claims (5)

A stator for a rotating electric machine in which a coil having an insulating film is wound around a stator core,
The coil has a slot receiving portion to be inserted into the slot of the stator core and a coil end portion,
the insulating film includes a first insulating layer and a second insulating layer;
The first insulating layer is provided in the slot-accommodating portion and the coil end portion,
the second insulating layer is provided only in the coil end portion of the slot accommodating portion and the coil end portion, and is provided outside the first insulating layer;
The second insulating layer has a higher partial discharge inception voltage or a higher dielectric breakdown voltage than the first insulating layer,
a second insulating layer including at least one of a first filler having a function of increasing a partial discharge inception voltage and a second filler having a function of increasing a dielectric breakdown voltage; The stator for a rotating electric machine according to claim 1 , wherein the first insulating layer does not include either the first filler or the second filler. 2 . The stator for a rotating electric machine according to claim 1 , wherein the first insulating layer includes at least one of the second filler and a third filler having a function of increasing heat dissipation of the coil. 4. The stator for a rotating electric machine according to claim 1, wherein the first insulating layer and the second insulating layer have the same resin component. 5. The stator for a rotating electric machine according to claim 4 , wherein the first insulating layer and the second insulating layer are electrocoating layers.