Stator of rotary electric machine and method of manufacturing stator coil

A stator of a rotary electric machine comprises a stator core and a stator coil that is wound around the stator core. The stator coil includes a first segment coil, a second segment coil, and a first connecting member that has a first fitting recess portion at a first end of the first connecting member and a second fitting recess portion at a second end of the first connecting member, the first connecting member connecting the first segment coil and the second segment coil by fitting the first segment coil into the first fitting recess portion and by fitting the second segment coil into the second fitting recess portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No. 2018-004509 filed on Jan. 15 2018, which is incorporated herein by reference in its entirety including the specification, drawings and abstract.

BACKGROUND

1. Technical Field

The present disclosure relates to a stator of a rotary electric machine, which includes a stator core and a stator coil that is wound around the stator core, and a method of manufacturing a stator coil.

2. Description of Related Art

A stator of a rotary electric machine is generally configured by winding a stator coil around a stator core. As the stator coil, a stator coil that is formed by connecting a plurality of segment coils is known. When manufacturing such a stator coil, for example, a substantially U-shaped segment coil is inserted into a slot of a stator core, and a portion of the segment coil, which protrudes from the end face of the stator core in an axial direction of the stator core, is tilted and bent in a circumferential direction. Then, an end portion of the bent segment coil is welded and joined to an end portion of another segment coil bent likewise.

SUMMARY

However, in such a technique, after the segment coil is assembled to the stator core, bending or welding of the segment coil, insulation treatment of a welded portion, and the like are needed, and thus a manufacturing process is complicated.

Therefore, in some of the related arts, a technique of bending a segment coil in advance and then assembling it to a stator core is disclosed. For example, Japanese Unexamined Patent Application Publication No. 2009-194999 (JP 2009-194999 A) discloses a technique of manufacturing a stator coil by preparing first and second coils formed in a desired shape in advance, bringing the tip of the first coil and the tip of the second coil into contact with each other and joining them together, thereby fabricating a multiphase circumferentially developing coil having a distributed winding structure, and sequentially inserting the circumferentially developing coils into slots of a stator core.

According to such a technique, after the segment coil is inserted into the slot, treatment such as bending or joining (welding) of the segment coil is not needed, and therefore, a manufacturing process can be simplified to some extent.

However, in JP 2009-194999 A, a joining method such as pressure welding or ultrasonic joining is adopted in order to directly join the tip of the first coil and the tip of the second coil together. However, such a joining method requires large-sized equipment and complicates the manufacturing process.

Therefore, the present disclosure provides a stator of a rotary electric machine and a method of manufacturing a stator coil, in which a manufacturing process can be further simplified.

A first aspect of the disclosure relates to a stator of a rotary electric machine. The stator includes a stator core and a stator coil that is wound around the stator core. The stator coil includes a first segment coil, a second segment coil, and a first connecting member. The first connecting member has a first fitting recess portion at a first end of the first connecting member and a second fitting recess portion at a second end of the first connecting member. The first connecting member connects the first segment coil and the second segment coil by fitting the first segment coil into the first fitting recess portion and by fitting the second segment coil into the second fitting recess portion.

According to the first aspect of the disclosure, the first and second segment coils can be connected solely by press-fitting the first segment coil into the first fitting recess portion and by press-fitting the second segment coil into the second fitting recess portion. In other words, in the connection of the segment coils, treatment such as welding or pressure welding is not needed. As a result, large-sized equipment is not needed and a manufacturing process can be further simplified.

In the stator according to the first aspect of the disclosure, the first connecting member may include a main body that is made of a conductive material and to which the first and second segment coils are fitted, and an insulating film covering an outer surface of the main body. The main body may configure a part of a current path of the stator coil.

According to the aspect of the disclosure, since the first and second segment coils may be spaced apart from each other, an error in the axial dimension of the segment coil can be absorbed by the first connecting member. As a result, the manufacturing process of the segment coil can be simplified.

In the stator according to the first aspect of the disclosure, the first connecting member may include a tubular main body that is made of an insulating material and to which the first and second segment coils are fitted. The first and second segment coils are electrically connected to each other by being in contact with each other inside the main body or through an electric conductor accommodated in the main body.

According to the aspect of the disclosure, the range of selection of the material of the main body of the connecting member is expanded.

In the stator according to the aspect of the disclosure, the first and second segment coils may be electrically connected to each other by an electric conductor inside the main body. The electric conductor may have elasticity or fluidity and the electric conductor may flexible in an axial direction of the electric conductor.

According to the aspect of the disclosure, an error in the axial dimension of the segment coil can be absorbed by the electric conductor. As a result, the manufacturing process of the segment coil can be simplified.

In the stator according to the first aspect of the disclosure, the first segment coil may have a first peeled portion where a first coil film is peeled off at an end portion of the first segment coil. The second segment coil may have a second peeled portion where a second coil film is peeled off at an end portion of the second segment coil. At least a part of the first peeled portion may be accommodated in the first fitting recess portion, and at least a part of the second peeled portion may be accommodated in the second fitting recess portion.

According to the aspect of the disclosure, after the first and second segment coils are connected by the first connecting member, insulation treatment of the peeled portion is not needed, and thus the manufacturing process can be further simplified.

In the stator according to the first aspect of the disclosure, at least one of an end portion of the first segment coil and the first fitting recess portion may be provided with a taper for guiding the other of the end portion of the first segment coil and the first fitting recess portion, and at least one of an end portion of the second segment coil and the second fitting recess portion may be provided with a taper for guiding the other of the end portion of the second segment coil and the second fitting recess portion.

According to the aspect of the disclosure, the first and second segment coils and the first connecting member can be more easily fitted to each other, and thus the manufacturing process can be further simplified.

In the stator according to the first aspect of the disclosure, the first connecting member and a second connecting member aligned adjacent to the first connecting member in a radial direction of the first segment coil may be offset from each other in an axial direction of the first segment coil.

According to the aspect of the disclosure, insulation between the coils can be secured reliably. That is, when there is a gap between the end portion of the first connecting member and the end portion of the coil film, the conducting wire is exposed in the gap. However, with the above configuration, a distance between the exposed portion of the coil and an exposed portion of the other coil aligned adjacent to the coil is increased, and thus insulation is secured.

In the stator according to the first aspect of the disclosure, the first segment coil and the second segment coil may have cross-sectional shapes different from each other.

According to the aspect of the disclosure, since a cross-sectional shape according to the characteristic needed (for example, improvement in space factor, improvement in bendability, or the like) to each segment coil can be adopted, the performance or quality of the stator can be further improved.

In the stator according to the first aspect of the disclosure, the first and second fitting recess portions of the first connecting member have shapes different from each other.

In the stator according to the first aspect of the disclosure, the first segment coil may have a vertical line portion that is accommodated in a slot of the stator core is fitted into the first fitting recess portion of the first connecting member. The second segment coil may be provided outside the stator core in an axial direction of the stator core, extend in a circumferential direction of the stator core, and configures a coil end is fitted into the second fitting recess portion of the first connecting member. The first segment coil and the second segment coil may be connected by the first connecting member in a vicinity of an end portion of the slot in an axial direction of the slot.

According to the aspect of the disclosure, with a configuration in which the first and second segment coils are connected in the vicinity of the end portion of the slot in the axial direction of the slot, the end portion of the first segment coil can be easily accessed even after the first segment coil is assembled to the core. As a result, the work of connecting the segment coils can be easily performed.

A second aspect of the disclosure relates to a method of manufacturing a stator coil that is wound around a stator core. The method includes preparing a first segment coil, a second segment coil, and a connecting member having a first fitting recess portion at a first end of the connecting member and a second fitting recess portion at a second end of the connecting member to form the stator coil, and connecting the first segment coil and the second segment coil by fitting the first segment coil into the first fitting recess portion and by fitting the second segment coil into the second fitting recess portion.

According to the second aspect of the disclosure, the segment coils can be connected solely by fitting the first segment coil into the first fitting recess portion and by fitting the second segment coil into the second fitting recess portion. In other words, when connecting the first and second segment coils, treatment such as welding or pressure welding is not needed. As a result, large-sized equipment is not needed, and the manufacturing process can be further simplified.

In the method according to the second aspect of the disclosure, an outer peripheral surface of the first connecting member may be subjected to insulation treatment before connecting the first and second segment coils.

According to the aspect of the disclosure, after the first and second segment coils are connected, insulation treatment of a peeled portion of the segment coil is not needed, and thus the manufacturing process of the stator coil can be further simplified.

In the method according to the second aspect of the disclosure, after the first segment coil formed in a final shape is assembled to the stator core, the second segment coil formed in a final shape may be connected to the first segment coil through the first connecting member.

According to the aspect of the disclosure, the first segment coil is formed in the final shape before assembling to the stator core, whereby it is possible to remove a bending step after the core assembling, and thus the manufacturing process of the stator coil can be further simplified.

In the method according to the aspect of the disclosure, the first segment coil may have a vertical line portion that is accommodated in a slot of the stator core. The second segment coil may be provided outside the stator core in an axial direction of the stator core, extend in a circumferential direction of the stator core, and forms a coil end. After a plurality of first segment coils is assembled to the stator core, a plurality of second segment coils integrated with resin may be connected to the plurality of the first segment coils through a plurality of the connecting members at once.

According to the aspect of the disclosure, since the second segment coils can be connected at once, the manufacturing process can be further simplified.

In the method according to the aspect of the disclosure, the first segment coil may be fitted to the connecting member after the first segment coil is assembled to the stator core.

In a case where the first segment coil is fitted to the connecting member before the first segment coil is assembled to the stator core, the first segment coil is locally thickened due to an axial compression force that is generated at the time of the fitting, and thus a space factor decreases. However, according to the aspect of the disclosure, the fitting of the first segment coil and the connecting member is performed after the first segment coil is assembled to the stator core, whereby such a problem can be suppressed.

According to the aspects of the disclosure, the segment coils can be connected solely by press-fitting the end portions of the segment coils into the fitting recess portions respectively. In other words, when connecting the first and second segment coils, treatment such as welding or pressure welding is not needed. As a result, large-sized equipment is not needed, and the manufacturing process can be further simplified.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, a stator10of a rotary electric machine will be described with reference to the drawings.FIG. 1is an exploded perspective view of the stator10of a rotary electric machine. The actual stator10has a large number of segment coils22. However, inFIG. 1, for the sake of viewability, solely a few segment coils22are shown.

The stator10is combined with a rotor to configure a rotary electric machine. The rotary electric machine to which the stator10is applied may be a rotary electric machine that is used as an electric motor or may be a rotary electric machine that is used as a generator. Therefore, the stator10of this example may be applied to a rotary electric machine that is, for example, a rotary electric machine that is mounted on an electrified vehicle, and operates as an electric motor that generates power for traveling and also operates as a generator that generates electric power with regenerative torque or the like.

The stator10has a stator core12and a stator coil20that is wound around the stator core12. The stator core12is divided roughly into an annular core back14(in this specification, the expression “annular” also includes the meaning of “substantially annular”) and a plurality of teeth16protruding radially inward from the inner peripheral surface of the core back14. A slot18that is a space in which a part of the stator coil20is accommodated is formed between the teeth16adjacent to each other in a circumferential direction of the core back14. The stator core12may be, for example, a laminated steel sheet that is made by laminating a plurality of electromagnetic steel sheets (for example, silicon steel sheets) in a thickness direction of the stator core12. The stator core12may be a dust core that is made by press-forming magnetic particles coated to be insulated.

The stator coil20is wound around the teeth16of the stator core12. A connection mode and a winding mode of the stator coil20may be appropriately selected according to the specifications of the rotary electric machine. Therefore, the stator coil20may have a configuration in which U-phase, V-phase, and W-phase coils are star-connected or delta-connected. The stator coil20may be wound in distributed winding or may be wound in concentrated winding. In any case, in this example, the stator coil20is configured by connecting a plurality of segment coils22.

The segment coil22is obtained by cutting the stator coil20to a length that is easy to handle. In this example, the segment coil22includes a U-shaped (in this specification, the expression “U-shaped” also includes the meaning of “substantially U-shaped”) first segment coil22aand a chevron-shaped (in this specification, the expression “chevron-shaped” also includes the meaning of “substantially chevron-shaped”) second segment coil22b. In the following, in a case where it is not distinguished between the first segment coil and the second segment coil, it is called a “segment coil22” with the suffix alphabet omitted.

FIG. 2is a front view of the first segment coil22a. The first segment coil22ais formed by covering a conducting wire32made of a conductive material (for example, copper or the like) with a coil film34(shown by black hatching) made of an insulating material. The conducting wire32is a rectangular wire having a rectangular cross section (in this specification, the expression “rectangular” also includes the meaning of “substantially rectangular”). The reason why the conducting wire32is formed of a rectangular wire in this way is for improving a space factor in the slot18.

The first segment coil22ais bent and formed in the same shape as that at the time of completion of the stator, that is, in the final shape. Specifically, the first segment coil22ahas a U-shape having a pair of vertical line portions28that is accommodated in the slots18and a connecting portion27connecting the vertical line portions28. The length of the vertical line portion28is almost the same as the axial dimension of the stator core12. For this reason, when the vertical line portion28is inserted into the slot18, the end of the vertical line portion28is located in the vicinity of an end portion in the axial direction of the slot18. The connecting portion27is provided outside the stator core12in the axial direction of the stator core12, extends in the circumferential direction of the stator core12, and configures a part of a coil end. A peeled portion30where the coil film34is peeled off such that the conducting wire32is exposed to the outside is formed at each of both ends of the first segment coil22a, that is, at the end of each of the vertical line portions28. The tip of the peeled portion30(the conducting wire32) has a tapered shape that tapers off.

FIG. 3is a front view of the second segment coil22b. The second segment coil22bis also formed by covering a conducting wire32made of a conductive material (for example, copper or the like) with a coil film. The second segment coil22bis also formed in the final shape. The second segment coil22bextends in the circumferential direction outside the stator core12in the axial direction on the side opposite to the connecting portion27to configure a part of a coil end. A peeled portion30where the coil film34is peeled off such that the conducting wire32is exposed to the outside is also formed at each of both ends of the second segment coil22b. The tip of the peeled portion30(the conducting wire32) also has a tapered shape that tapers off.

Here, as is apparent fromFIG. 3, the conducting wire32that is used for the second segment coil22bis a round wire having a circular cross section. The reason why the conducting wire32of the second segment coil22bis formed of a round wire in this manner is for facilitating bending of the second segment coil22b. That is, the second segment coil22bneeds to be bent or curved not only in the circumferential direction of the stator10but also in the radial direction of the stator10, compared to the first segment coil22a. For this reason, it is desirable that the second segment coil can be more flexibly bent than in the first segment coil22a. A round wire is easily bent in any direction, compared to a rectangular wire, and therefore, in this example, the second segment coil22bis formed of a round wire.

Not only the conducting wires32of the first and second segment coils22a,22bbut also the coil films34of the first and second segment coils22a,22bmay be different from each other. For example, in a case where the conducting wire32of the second segment coil22bis a flexible round wire, damage to the coil film34at the time of bending can be reduced. For this reason, the coil film34of the second segment coil22bmay be made thinner than the coil film34of the first segment coil22a.

The first segment coil22aand the second segment coil22bare connected to each other by a connecting member24.FIG. 4is a perspective view of the connecting member24.FIG. 5is a schematic sectional view of the periphery of the connecting member24. The connecting member24connects the two segment coils22. The connecting member24has a tubular shape in which a through-hole penetrating in the axial direction thereof is formed. For this reason, the connecting member24has recess portions at both ends of the connecting member24. The recess portion serves as a fitting recess portion36into which the end portion (the peeled portion30) of the segment coil22is fitted. In the following, the recess portion into which the first segment coil22ais fitted is referred to as a first fitting recess portion36a, and the recess portion into which the second segment coil22bis fitted is referred to as a second fitting recess portion36b. In a case where it is not distinguished between the first fitting recess portion and the second fitting recess portion, it is called a “fitting recess portion36” with the suffix alphabet omitted.

The inner peripheral length of the fitting recess portion36is made equal to or slightly smaller than the outer peripheral length of the segment coil22to be fitted into the fitting recess portion36. Therefore, in this example, the fitting recess portion36is circular in cross section. However, the radius of the fitting recess portion36is equal to or slightly smaller than the radius of the conducting wire32of the second segment coil22b. In a case where the outer peripheral length of the conducting wire32of the first segment coil22ais set to be D, the radius of the fitting recess portion36is D/2π or slightly smaller than D/2π. With such a configuration, it is possible to reliably and firmly fit the segment coil22into each fitting recess portion36. When the conducting wire32(rectangular wire) of the first segment coil22ais fitted into the first fitting recess portion36a, the first fitting recess portion36ais deformed into a rectangular cross-sectional shape in accordance with the shape of the conducting wire32to be brought into close contact with the outer surface of the conducting wire32.

The connecting member24in this example includes a tubular main body38made of a conductive material, and an insulating film40covering the outer peripheral surface of the main body38. The inner peripheral surface of the tubular main body38comes into close contact with the fitted segment coil22. In other words, the main body38is fitted to the segment coil22, thereby being electrically connected thereto, and functions as a part of a current path of the stator coil20, that is, a part of the stator coil. Since the outer peripheral surface of the main body38is covered with the insulating film40in advance, insulation between the coils can be easily secured.

The main body38functions as a part of the current path, and therefore, when an electric current flows through the stator coil20, the main body38generates heat together with the stator coil20. The main body38thermally expands due to the generated heat. However, at this time, it is desirable that the main body38is made of a material having an expansion coefficient equal to or smaller than that of the conducting wire32of the segment coil22such that the fitting of the main body38and the conducting wire32of the segment coil22is not loosened. Therefore, the main body38may be made of the same material (for example, copper) as the conducting wire32, for example.

As shown inFIG. 5, the first segment coil22ais fitted to one end (the first fitting recess portion36a) of the connecting member24, and the second segment coil22bis fitted to the other end (the second fitting recess portion36b) of the connecting member24. At this time, the first and second segment coils22a,22bmay come into contact with each other inside the connecting member24, or may be spaced apart from each other, as shown inFIG. 5. That is, even though the first and second segment coils22a,22bare spaced apart from each other, the electrical connection between the two segment coils22is secured by the main body38made of a conductive material. A gap between the first and second segment coils22a,22binside the connecting member24may be filled with conductive paste (for example, metal paste). Such conductive paste is provided, whereby it is possible to reduce electric resistance at the connecting portion and to improve thermal conductivity.

Here, by connecting the segment coils22by using the connecting member24in this manner, the manufacturing process of the stator10can be further simplified compared to the related art. This will be described in comparison with the related art.

Also in the related art, a technique of forming the stator coil20by connecting a plurality of segment coils22is known. However, in the related art, after the segment coil22is assembled to the stator core12, the segment coil22is bent and welded to another segment coil22.FIG. 14AandFIG. 14Bare diagrams showing a state of manufacturing the stator coil20of the related art. As shown inFIG. 14A, in the related art, first, the segment coil22, which has a U-shape and which has the peeled portions30at both ends of the segment coil22, is inserted into the slot18. Subsequently, as shown inFIG. 14B, the segment coil22protruding from the end face of the stator core12in the axial direction of the stator core12is bent in the circumferential direction of the stator core12and then brought into contact with and welded to the end portion of the corresponding other segment coil22(in the illustrated example, another segment coil22adjacent thereto in the radial direction). Finally, insulation treatment, for example, coating of insulating paint, is performed on the peeled portion30.

In the case of such a related art, after the segment coil22is assembled to the stator core12, bending, welding, and insulation treatment of the segment coil22are performed. However, since there is no enough space around the segment coil22after it is assembled to the stator core12, it is cumbersome to perform such processing and treatment.

Since the segment coil22is bent in a narrow space, the coil film34of the segment coil22is easily damaged, so that there is a case where an insulation property decreases. Welding is performed in order to connect the segment coils22. However, there is a possibility that the coil film34may be damaged due to the heat during the welding. In order to restrain damage to the coil film34, it is needed to make the coil end higher. However, this hinders downsizing of the stator10.

Therefore, in some of the related arts, there is disclosed a technique in which the segment coil22is formed into a final shape in advance and the end portions of the segment coils22are brought into contact with each other and joined together (for example, JP 2009-194999 A or the like). In the case of this technique, since it is not needed to bend the segment coil22after the segment coil22is assembled to the stator core12, deterioration of the coil film34caused by bending can be restrained. Since the bending of the segment coil22after the segment coil22is assembled to the stator core12is not needed, it is possible to simplify the manufacturing process to some extent. However, in the case of this technique, since the end face of one of the segment coils22in the axial direction of the segment coil22are brought into contact with the end face of another of the segment coils22, it is needed to control the dimensional precision of the segment coil22in the axial direction of the segment coil22to a high level, and this causes complication of a manufacturing process or an increase in cost. Also in this technique, after joining the segment coils22, insulation treatment of the peeled portion30is needed. In this technique, the segment coils22are joined to each other by pressure welding, ultrasonic joining, or caulking. However, in order to joining the segment coils22, dedicated equipment is needed, causing an increase in equipment cost.

On the other hand, in the stator coil20disclosed in this specification, as described above, the segment coils22are connected by fitting the segment coils22to both ends (the fitting recess portions36) of the connecting member24. In the case of the fitting processing, no heat is generated, and therefore, according to this example, unlike the related art using welding or joining, the deterioration of the coil film34due to heat can be almost reliably restrained. In the case of this example, since it is merely needed to press-fit the conducting wire32of the segment coil22into the fitting recess portion36of the connecting member24, manufacturing equipment can be simplified compared to the related art using welding, pressure welding, ultrasonic joining, or the like.

In this example, since the main body38of the connecting member24configures a part of the current path of the stator coil20, the segment coils22may not be in direct contact with each other. As a result, in this example, an allowable error of the dimension of the segment coil22in the axial direction of the segment coil22can be increased compared to the related art. That is, according to this example, an error in the dimension of the segment coil22in the axial direction of the segment coil22can be absorbed by the distance between the end face of one segment coil and the end face of another segment coil inside the connecting member24.

In this example, since the outer peripheral surface of the connecting member24is insulated in advance and at least a part of the peeled portion30, e.g., almost the whole of the peeled portion30is covered with the connecting member24, it is not needed to separately perform insulation treatment after the connection of the segment coils22. However, as shown inFIG. 5, there is a possibility that a slight gap is generated between the end portion of the connecting member24and the end portion of the coil film34. In such a gap, the conducting wire32of the segment coil22is exposed to the outside. In order to restrain an exposed portion41of the conducting wire32from coming close to the exposed portion41of another conducting wire32, in this example, the connecting members24adjacent to each other in a radial direction of the segment coil is shifted from each other. That is, one of connecting members24and anther of connecting member which is aligned adjacent to the one of the connecting members are offset from each other in a coil axial direction of the coil.

This will be described with reference toFIG. 6.FIG. 6is an image diagram in the slot18, and inFIG. 6, a right-left direction in the plane of the drawing is a stator radial direction (a coil radial direction), and an up-down direction in the plane of the drawing is a coil axial direction. As shown inFIG. 6, in this example, the position in the coil axial direction of the connecting member24(the connecting portion between the segment coils22) is shifted from another connecting member24adjacent thereto in the coil radial direction. With such a configuration, a distance K between the exposed portions41of the conducting wires32is increased, and thus the insulation between the coils can be secured more reliably.

Next, a flow of manufacturing of the stator coil20will be described with reference toFIG. 7.FIG. 7is a flowchart showing a flow of manufacturing of the stator coil20. When manufacturing the stator coil20, first, the segment coil22is manufactured (prepared). Specifically, a long coil material is cut to a desired length (S10). The coil material is a material of the segment coil22and is formed by covering a long conducting wire32with a coil film34. In this example, two types of coil materials, that is, a coil material using a rectangular wire having a rectangular cross section and a coil material using a round wire having a circular cross section are prepared. Each coil material is cut by using a dedicated blade such that a desired cut shape is obtained. In this example, the coil material is cut such that the end portion of the segment coil22has a tapered shape that tapers off.

Subsequently, the coil film34is peeled off at the end portion of each segment coil22to form the peeled portion30(S12). The peeled portion30is formed, for example, by cutting off the coil film34by using a laser or the like.

Subsequently, the segment coil22is bent or curved to be formed into a desired shape (S14). This forming is performed, for example, by pressing the segment coil22against a dedicated die or by bending the segment coil22with a dedicated roller. In this forming, each segment coil22is formed into a final shape. In other words, after the segment coil is assembled to the stator core, each segment coil22is not subjected to bending. Therefore, in this example, the first segment coil22ais formed in a U-shape, and the second segment coil22bis formed in a chevron shape.

When the segment coil22can be formed into a desired shape, the U-shaped first segment coil22ais assembled to the stator core12(S16). That is, the vertical line portion28of the first segment coil22ais inserted into the slot18. The first segment coil22aassembled to the stator core12is held by a dedicated jig so as to maintain the assembled state thereof.

When the first segment coils22acan be assembled to the core, subsequently, the connecting member24is fitted to the peeled portion30of the first segment coil22a(S18). That is, the peeled portion30of the first segment coil22ais press-fitted into the first fitting recess portion36a. At this time, since the tip of the peeled portion30has a tapered shape that tapers off, the peeled portion30can be easily guided into the first fitting recess portion36a, and thus the peeled portion30and the first fitting recess portion36acan easily be connected to each other. In this way, the connecting member24is also assembled to the stator core12.

Finally, the peeled portion30of the second segment coil22bis press-fitted into the second fitting recess portion36bof the connecting member24assembled to the core (S20). Since the tip of the peeled portion30of the second segment coil22balso has a tapered shape that tapers off, the peeled portion30can be easily guided into the second fitting recess portion36b, and thus the peeled portion30and the second fitting recess portion36bcan easily be connected to each other. In this way, the first segment coil22aand the second segment coil22bare mechanically and electrically connected by the connecting member24. Such connection is performed in all the first and second segment coils22a,22b, whereby the stator coil20is completed.

As is apparent from the above description, according to this example, since the segment coils22are connected to each other with simple processing such as fitting, an equipment cost can be reduced compared to the related art using welding or pressure welding. In the case of the fitting, no heat is generated, and therefore, the deterioration of the coil film34can be more reliably restrained. Since the connecting member24covered with the insulating film40in advance is used, the insulation treatment after the segment coils22are connected each other is not needed, and thus the manufacturing process can be further simplified. Since bending of the segment coil22after the segment coil22is assembled to the stator core is not needed, the manufacturing process can be simplified and the deterioration of the coil film34can be restrained.

The manufacturing procedure described above is merely an example, and as long as at least the first and second segment coils22a,22bare fitted into the fitting recess portions36of the connecting member24so as to connect both the coils, the manufacturing procedure may be appropriately changed. Therefore, for example, step S18and step S20may be reversed. That is, after the connecting member24is fitted to the second segment coil22b, the first segment coil22amay be fitted to the connecting member24. Before the first segment coil22ais assembled to the core, the connecting member24may be fitted to the first segment coil22a. That is, step S16and step S18may be reversed. However, in a case where the connecting member24is fitted to the first segment coil22abefore the first segment coil22ais assembled to the core, there is a possibility that the first segment coil22amay be locally thickened due to an axial compression force that is generated when the connecting member24is fitted to the first segment coil22a. When the first segment coil22ais locally thickened, the space factor in the slot18decreases. Therefore, it is desirable that the first segment coil22ais fitted to the connecting member24after the first segment coil22ais assembled to the core.

A plurality of second segment coils22bmay be connected to the corresponding first segment coils22aat once. This will be described with reference toFIG. 8.FIG. 8is a schematic diagram of the stator core as viewed from the inside of the stator core in the radial direction of the stator core. InFIG. 8, a right-left direction in the plane of the drawing is a stator circumferential direction, and an up-down direction in the plane of the drawing is a stator axial direction. As shown inFIG. 8, the second segment coils22bmay be connected and integrated by a resin mold50. Then, the integrated part (the second segment coils22b) may be fitted to a plurality of connecting members at once. With such a configuration, the work of connecting the segment coils22can be further simplified. In this case, the resin mold50connecting the second segment coils22bremains at one end of the stator coil20in the axial direction of the stator coil20.

In the above description, the main body38of the connecting member24is made of a conductive material. However, the main body38of the connecting member24may be made of an insulating material. Therefore, for example, the main body38of the connecting member24may be a tubular body made of an insulating material.FIG. 9is a diagram showing an example in which the main body38is made of an insulating material. In this case, the first segment coil22aand the second segment coil22bmay be brought into contact with each other inside the connecting member24to secure a current path. In this case, it is desirable that the connecting member24is made of an insulating material (for example, glass or ceramics) having a coefficient of thermal expansion equal to or smaller than that of the conducting wire32of the segment coil22.

In a case where the main body38of the connecting member24is made of an insulating material, an electric conductor that comes into contact with the first and second segment coils22a,22bmay be provided inside the main body38. Such an electric conductor is not particularly limited as long as it has conductivity. However, it is desirable that the electric conductor has elasticity or fluidity and the dimension of the electric conductor in the coil axial direction can be changed. That is, the electric conductor is flexible in the coil axial direction. Therefore, for example, an electric conductor42may be conductive paste (for example, metal paste) that is sintered after being filled between the first and second segment coils22a,22b, as shown inFIG. 10. In this case, the conductive paste (the electric conductor42) comes into contact with the entirety of the tip surfaces (including the tapered surfaces) of the first and second segment coils22a,22b. Then, in this case, the contact area between the electric conductor42and each of the segment coils22a,22bbecomes sufficiently large, and thus the electric resistance decreases and the thermal conductivity is improved. As another form, the electric conductor42may include a spring that can expand and contract in the coil axial direction, as shown inFIG. 11. In any case, the electric conductor42deformable in the coil axial direction is provided inside the insulating main body38, whereby an error in the dimension in the coil axial direction of the segment coil22can be absorbed.

In the above description, the connecting member24is a tubular body having a through-hole formed therein. However, the connecting member24may not be a tubular body as long as the fitting recess portions36are formed at both ends thereof. For example, as shown inFIG. 12, the connecting member24may be a non-tubular body in which holes (recess portions) are formed in the end faces in the axial direction of the connecting member. In other words, the first fitting recess portion36aand the second fitting recess portion36bmay not communicate with each other. In this case, the first fitting recess portion36aand the second fitting recess portion36bmay have shapes different from each other. Therefore, for example, the first fitting recess portion36amay have a rectangular shape matching the conducting wire32of the first segment coil22a, and the second fitting recess portion36bmay have a circular shape (in this specification, the expression “circular” also includes the meaning of “substantially circular”) matching the conducting wire32of the second segment coil22b.

In the above description, the first segment coil22ahas a U-shape and the second segment coil22bhas a chevron shape. However, the shapes of the segment coils22may be appropriately changed.FIG. 13AtoFIG. 13Dare diagrams showing variations of the shape of the segment coil22. As shown inFIG. 13A, a configuration is also acceptable in which the first segment coil22ais formed in a straight line shape having solely a portion to be accommodated in the slot18and the second segment coil22bhaving a chevron shape is connected to each of both sides of the first segment coil22a. In the case of such a configuration, the portion of the stator coil20, which is accommodated in the slot, can be formed of a rectangular wire, and the portion to become the coil end can be formed of a round wire. As a result, the coil end portion can be easily formed (bent) while improving the space factor in the slot18.

As another form, as shown inFIG. 13B, all of the segment coils22may be formed in a U-shape. In the case of such a configuration, each segment coil22is fitted to the connecting member24within the slot18. In this case, in order to facilitate the fitting work, it is desirable that the stator core12is a split core divided into two parts in the axial direction. As another form, as shown inFIG. 13C, the segment coil22may be formed in a J-shape (in this specification, the expression “J-shape” also includes the meaning of a “substantially J-shape”) in which the vertical line portion28to be accommodated in the slot18is connected to one end of a chevron-shaped transverse line portion26serving as a coil end.

All the segment coils22described above are connected inside the slot18or in the vicinity of the end portion of the slot18in the axial direction of the slot18. In other words, the portion corresponding to the coil end, of the segment coil22, extends outside the stator core12in the axial direction without interruption in the middle from one slot18to the other slot18. With such a configuration, the height of the coil end can be reduced, and thus the stator10can be downsized.

However, in some cases, as shown inFIG. 13D, the connection between the segment coils22may be performed in the middle of the coil end. In the case of such a configuration, the hollow connecting member24is present in the middle of the coil end, and thus the heat radiation property of the coil end is improved.

In the above description, the shape of the conducting wire32of the first segment coil22ais different from the shape of the conducting wire32of the first segment coil22b. However, the shapes of the conducting wires of both the coils22a,22bmay be the same. By making the shapes of the conducting wires the same, a coil material can be used in common, and thus a material cost can be reduced. In this example, a taper for guiding the fitting recess portion36is provided at the tip of the segment coil22(the peeled portion30). However, instead of or in addition to the segment coil22, a taper for guiding the segment coil22may be provided at the fitting recess portion36.