Stator and manufacturing method of the same

A stator for a rotary electric machine includes a stator core, a stator winding, and a sensor unit. The stator has a hollow cylindrical shape and includes slots. The stator winding includes segment conductors respectively inserted in the slots. The sensor unit includes a sensor holding conductor, and a temperature sensor. The sensor holding conductor is welded to first and second segment conductors among the segment conductors. The temperature sensor is held by the sensor holding conductor. The sensor holding conductor includes first and second end portions, and a bent portion. The first end portion is welded to an end portion of the first segment conductor. The second end portion is welded to an end portion of the second segment conductor. The bent portion couples the first end portion and the second end portion to each other. The temperature sensor is held at an inner side of the bent portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from Japanese Patent Application No. 2020-085662 filed on May 15, 2020, the entire contents of which are hereby incorporated by reference.

BACKGROUND

The disclosure relates to a stator of a rotary electric machine and a manufacturing method of the same.

A rotary electric machine, such as an electric motor and a generator, includes a stator wound with a stator coil. As such a stator coil, there have been proposed stator coils including plural segment coils bent substantially in a U shape (see Japanese Unexamined Patent Application Publication (JP-A) No. 2014-90546, JP-A No. 2016-214011, JP-A No. 2018-88790, and JP-A No. 2012-175861).

SUMMARY

An aspect of the disclosure provides a stator configured to be installed in a rotary electric machine. The stator includes a stator core, a stator winding, and a sensor unit. The stator core has a hollow cylindrical shape, and includes slots. The stator winding includes segment conductors respectively inserted in the slots. The segment conductors include a first segment conductor and a second segment conductor. The sensor unit includes a sensor holding conductor, and a temperature sensor. The sensor holding conductor is welded to the first segment conductor and the second segment conductor. The temperature sensor is held by the sensor holding conductor. The sensor holding conductor includes a first end portion, a second end portion, and a bent portion. The first end portion is welded to an end portion of the first segment conductor. The second end portion is welded to an end portion of the second segment conductor. The bent portion couples the first end portion and the second end portion to each other. The temperature sensor is held on an inner side of the bent portion.

An aspect of the disclosure provides a manufacturing method of a stator configured to be installed in a rotary electric machine. The method includes inserting segment conductors respectively into slots formed in a stator core having a hollow cylindrical shape. The method includes bending end portions of the segment conductors which protrude from an end surface of the stator core so as to arrange conductor joint portions in both of a circumferential direction and a radial direction of the stator core. The conductor joint portions include the end portions of the segment conductors. The method includes temporarily attaching a sensor unit between a first segment conductor and a second segment conductor that constitute one of the conductor joint portions. The sensor unit includes a sensor holding conductor and a temperature sensor. The method includes welding the conductor joint portions individually so as to form a stator winding with the segment conductors. The welding includes welding the first segment conductor and the sensor holding conductor to each other. The welding includes welding the second segment conductor and the sensor holding conductor to each other.

DETAILED DESCRIPTION

Since a stator coil generates heat when powered, temperature of the stator coil is to be monitored to appropriately control a rotary electric machine. In view of this, a temperature sensor such as a thermistor is attached to bus bars coupled to power points and neutral points of the stator coil. However, because the bus bars provided with the temperature sensor are disposed apart from the stator coil in many cases, it was difficult to detect the temperature of the stator coil appropriately.

It is desirable to appropriately detect the temperature of the stator coil.

In the following, some preferred but non-limiting implementations of the disclosure are described in detail with reference to the accompanying drawings. Note that sizes, materials, specific values, and any other factors illustrated in respective implementations are illustrative for easier understanding of the disclosure, and are not intended to limit the scope of the disclosure unless otherwise specifically stated. Further, elements in the following example implementations which are not recited in a most-generic independent claim of the disclosure are optional and may be provided on an as-needed basis. Throughout the present specification and the drawings, elements having substantially the same function and configuration are denoted with the same reference numerals to avoid any redundant description. Further, elements that are not directly related to the technology are unillustrated in the drawings. The drawings are schematic and are not intended to be drawn to scale.

In the following description, as a rotary electric machine11including a stator10according to an embodiment of the disclosure, a three-phase alternating current synchronous motor-generator mounted on an electric vehicle, a hybrid vehicle, and other vehicles will be given as an example. However, this is not to be construed in a limiting sense. Any rotary electric machine may be applied insofar as the rotary electric machine includes the stator10assembled with segment coils40.

Configuration of Rotary Electric Machine

FIG.1is a cross-sectional view of an example of the rotary electric machine11including the stator10according to the embodiment of the disclosure. As illustrated inFIG.1, the rotary electric machine11is a motor-generator and includes a motor housing12. The motor housing12includes a housing body13of a bottomed, hollow cylindrical shape, and an end cover14that closes an open end of the housing body13. The stator10is secured in the housing body13and includes a stator core15of a hollow cylindrical shape that includes plural silicon steel sheets, for example, and a three-phase stator coil SC wound on the stator core15. In one example, the stator coil SC may serve as a “stator winding”. It is noted that an oil passage16to guide oil is formed in the motor housing12. Via this oil passage16, cooling oil is supplied to a coil end Ce of the stator coil SC.

A bus bar unit20is coupled to the coil end Ce of the stator coil SC. This bus bar unit20includes three power bus bars21,22, and23coupled to three power points Pu, Pv, and Pw of the stator coil SC, a neutral bus bar24that couples three neutral points Nu, Nv, and Nw of the stator coil SC to one another, and an insulating member25to hold these bus bars21,22,23, and24. End portions of the power bus bars21,22, and23protrude outward from the motor housing12, and a power cable27extending from an inverter26, for example, is coupled to each of the power bus bars21,22, and23.

A rotor30of a solid cylindrical shape is rotatably accommodated in a center of the stator core15. This rotor30includes a rotor core31of a hollow cylindrical shape that includes plural silicon steel sheets, for example, plural permanent magnets32buried in the rotor core31, and a rotor shaft33secured in a center of the rotor core31. One end of the rotor shaft33is supported by a bearing34disposed on the housing body13, and the other end of the rotor shaft33is supported by a bearing35disposed on the end cover14.

Configuration of Stator

FIG.2is a cross-sectional view of the stator10taken along line A-A inFIG.1.FIG.3is a cross-sectional view of the stator core15including a phase winding of a U phase (hereinafter referred to as U-phase coil Cu).FIG.4is a perspective view of one of the segment coils40as an example. As described later, the stator coil SC includes a phase winding of a V phase (hereinafter referred to as V-phase coil Cv) and a phase winding of a W phase (hereinafter referred to as W-phase coil Cw) as well as the U-phase coil Cu. The U-phase coil Cu, the V-phase coil Cv, and the W-phase coil Cw in the drawings have an identical coil configuration, and are wound on the stator core15and have phases displaced from one another by 120°.

As illustrated inFIG.2, plural slots S1to S48are formed in an inner-peripheral portion of the stator core15of the hollow cylindrical shape at predetermined intervals in a circumferential direction. Each of the slots S1to S48contains the segment coil40. The plural segment coils40are coupled to one another to constitute the stator coil SC. In one example, the segment coil40may serve as a “segment conductor”. As illustrated inFIGS.2and3, the segment coils40that constitute the U-phase coil Cu are held in the slots S1, S2, S7, S8. . . , the segment coils40that constitute the V-phase coil Cv are held in the slots S5, S6, S11, S12. . . , and the segment coils40that constitute the W-phase coil Cw are held in the slots S3, S4, S9, S10. . . .

As illustrated inFIG.4, each of the segment coils40bent substantially in the U shape includes a coil side41held in one of the slots (e.g., the slot S1), and a coil side42held in another slot (e.g., the slot S7) at a predetermined coil pitch. The segment coil40also includes an end portion43that couples the pair of coil sides41and42to each other, and joint end portions44and45that respectively extend from the pair of coil sides41and42. It is noted that the segment coil40is made of a rectangular wire of a conductive material such as copper, and that the segment coil40except distal ends of the joint end portions44and45is coated with an insulating film of enamel, resin or the like. The end portion43of the segment coil40is not limited to a bent shape illustrated inFIG.4but is bent in various shapes in accordance with an assembling position with respect to the stator core15.

FIG.5is a perspective view of the stator10.FIGS.6A and6Bare diagrams illustrating an example of a coupling state of the segment coils40. As illustrated inFIGS.2and5, the plural segment coils40are assembled in each of the slots S1to S48of the stator core15. As illustrated inFIGS.5,6A, and6B, when the segment coils40are assembled with the stator core15, the joint end portions44and45of the segment coils40protrude from one end surface50of the stator core15to a power-line side, and the end portions43of the segment coils40protrude from the other end surface S1of the stator core15to a reverse power-line side. In one example, the one end surface50may serve as an “end surface”.

As illustrated inFIGS.6A and6B, the joint end portions44and45that protrude from the one end surface50of the stator core15are bent to come into contact with the joint end portions44and45of other segment coils40and thereafter welded to the joint end portions44and45of the other segment coils40in contact. Thus, the joint end portions44and45of the segment coils40are welded to one another into conductor joint portions60with which the plural segment coils40are coupled to one another into a single conductor. In other words, the plural segment coils40constitute the U-phase coil Cu, the plural segment coils40constitute the V-phase coil Cv, and the plural segment coils40constitute the W-phase coil Cw. It is noted that the joint end portions44and45after welded undergo insulating processing to form a resin film, for example, to coat the conductor.

FIG.7is a diagram illustrating an example of a connection state of the stator coil SC. As illustrated inFIG.7, the U-phase coil Cu, the V-phase coil Cv, and the W-phase coil Cw constitute the stator coil SC. The U-phase coil Cu includes the plural segment coils40connected to one another in series. One end of the U-phase coil Cu serves as a power point Pu, and the other end of the U-phase coil Cu serves as a neutral point Nu. The V-phase coil Cv includes the plural segment coils40connected to one another in series. One end of the V-phase coil Cv serves as a power point Pv, and the other end of the V-phase coil Cv serves as a neutral point Nv. The W-phase coil Cw includes the plural segment coils40connected to one another in series. One end of the W-phase coil Cw serves as a power point Pw, and the other end of the W-phase coil Cw serves as a neutral point Nw. The neutral point Nu of the U-phase coil Cu, the neutral point Nv of the V-phase coil Cv, and the neutral point Nw of the W-phase coil Cw are coupled to one another. These phase coils Cu, Cv, and Cw constitute the stator coil SC.

Configuration for Temperature Detection

Next, a configuration to detect temperature of the stator coil SC will be described.FIG.8is a diagram illustrating some of the conductor joint portions60at the coil end Ce of the stator coil SC. As illustrated inFIG.8, on the one end surface50side of the stator core15, the joint end portions44and45of the segment coils40are welded to each other to form the plural conductor joint portions60. These conductor joint portions60are arranged in both of the circumferential direction and a radial direction of the stator core15. As a joint portion group including the plural conductor joint portions60, there are a first joint portion group G1located on an outermost side in the radial direction and arranged in the circumferential direction, and a second joint portion group G2located on an inner side of the first joint portion group G1in the radial direction. As illustrated inFIG.8, a sensor unit61to detect temperature of the stator coil SC is disposed on a conductor joint portion60x, which is one of the conductor joint portions60that constitute the second joint portion group G2. That is, when the plural conductor joint portions60are divided into the first joint portion group G1and the second joint portion group G2, the sensor unit61is disposed on the conductor joint portion60xof the second joint portion group G2.

FIG.9is an enlarged perspective view of a range a inFIG.5.FIG.10is a diagram illustrating the conductor joint portion60xwhere the sensor unit61is attached. It is noted that although the segment coils are denoted by a reference symbol “40” in the preceding description, the segment coils40where the sensor unit61is attached will be denoted by reference symbols “C1and C2” in the following description. As described above, the conductor joint portion60where the sensor unit61is provided is denoted by the reference symbol “60x”.

As illustrated inFIGS.9and10, the conductor joint portion60xincludes a joint end portion71of a segment coil C1, and a joint end portion72of a segment coil C2. In one example, the joint end portion71of the segment coil C1may serve as an “end portion” of a “first segment conductor”, and the joint end portion72of the segment coil C2may serve as an “end portion” of a “second segment conductor”. The sensor unit61including a sensor holding conductor62and a thermistor63is interposed between the joint end portion71of the segment coil C1and the joint end portion72of the segment coil C2. In one example, the thermistor63may serve as a “temperature sensor”. The sensor holding conductor62bent substantially in a U shape includes a joint end portion62aextending in a straight line, a joint end portion62bextending in a straight line, and a bent portion62cthat couples this pair of joint end portions62aand62bto each other. In one example, the joint end portion62amay serve as a “first end portion”, and the joint end portion62bmay serve as a “second end portion”. The joint end portions62aand62bof the sensor holding conductor62are apart from each other, and a predetermined gap S is defined between the joint end portion62aand the joint end portion62b.

The joint end portion62aof the sensor holding conductor62is welded to the joint end portion71of the segment coil C1, and the joint end portion62bof the sensor holding conductor62is welded to the joint end portion72of the segment coil C2. The thermistor63is disposed inside the bent portion62cof the sensor holding conductor62, and the thermistor63is secured to the sensor holding conductor62with an encapsulating material64such as resin. That is, the thermistor63to detect temperature is held inside the bent portion62cof the sensor holding conductor62. It is noted that the sensor holding conductor62is made of a rectangular wire of the same material as the segment coils C1and C2, namely, a conductive material such as copper.

In this manner, the sensor unit61is attached to the conductor joint portion60xso that temperature of the stator coil SC can be appropriately detected. That is, because the sensor unit61is assembled to the coil end Ce of the stator coil SC, measurement of the temperature of the stator coil SC can be performed at a location where a higher degree of temperature can be obtained than when the sensor unit61is assembled to the bus bar unit20. Moreover, because the thermistor63is surrounded by the bent portion62cof the sensor holding conductor62that generates heat when powered, measurement of the temperature of the stator coil SC can be performed at a location where a higher degree of temperature can be obtained.

Furthermore, as illustrated inFIG.8, the sensor unit61is disposed in the second joint portion group G2on the inner side in the radial direction. From this point of view as well, the temperature of the stator coil SC can be appropriately detected. That is, because an inner-peripheral portion of the coil end Ce is less likely to be cooled than an outer-peripheral portion of the coil end Ce, the sensor unit61is disposed in the second joint portion group G2so that measurement of the temperature of the stator coil SC can be performed at a location where a higher degree of temperature can be obtained. Besides, as illustrated inFIG.1, because cooling oil is supplied to the outer-peripheral portion of the coil end Ce, temperature of the outer-peripheral portion of the coil end Ce is more likely to be low than other portions. Even with such a cooling structure, the sensor unit61is disposed in the second joint portion group G2so that measurement of the temperature of the stator coil SC can be performed at a location where a higher degree of temperature can be obtained.

Manufacturing Method

Next, a manufacturing method of the stator10according to the embodiment of the disclosure will be described.FIG.11is a simplified flowchart of part of the manufacturing method of the stator10.FIGS.12A and12Bare diagrams illustrating an assembling process of the sensor unit61.FIGS.13A to13Care diagrams illustrating an attachment process of the sensor unit61to the conductor joint portion60x.

As illustrated inFIG.11, a manufacturing process of the stator10includes a coil insertion step100of inserting the segment coils40into the stator core15, and a coil bending step110of bending the joint end portions of the segment coils40. At the coil insertion step100, as illustrated inFIGS.2and6A, the plural segment coils40are inserted into the plural slots S1to S48formed in the stator core15. At the coil bending step110, as illustrated inFIGS.6B and8, the joint end portions44and45of the segment coils40that protrude from the one end surface50of the stator core15are bent to provide the plural conductor joint portions60in both of the circumferential direction and the radial direction of the stator core15.

As illustrated inFIG.11, the manufacturing process of the stator10also includes a sensor assembling step200of assembling the sensor unit61. At the sensor assembling step200, as illustrated inFIG.12A, a measurement member63aof the thermistor63is contained within the bent portion62cof the sensor holding conductor62, and as illustrated inFIG.12B, the thermistor63is secured to the sensor holding conductor62with the encapsulating material64such as resin. In this manner, the thermistor63is secured to the sensor holding conductor62so as to form the sensor unit61including the sensor holding conductor62and the thermistor63. In some embodiments, in order to detect a higher degree of temperature of the stator coil SC, the measurement member63aof the thermistor63is in contact with the sensor holding conductor62.

As illustrated inFIG.11, the manufacturing process of the stator10further includes a sensor temporary attachment step120of attaching the sensor unit61to the conductor joint portion60x, and a coil welding step130of welding the conductor joint portions60,60xby TIG welding, for example. At the sensor temporary attachment step120, as illustrated inFIG.13A, the sensor unit61including the sensor holding conductor62and the thermistor63is inserted between the first segment coil C1and the second segment coil C2that constitute the conductor joint portion60x. At the coil welding step130, as indicated by a symbol X inFIG.13B, the joint end portion71of the segment coil C1and the joint end portion62aof the sensor holding conductor62are welded to each other, and the joint end portion72of the segment coil C2and the joint end portion62bof the sensor holding conductor62are welded to each other. Thus, as illustrated inFIG.13C, the segment coils C1and C2, and the sensor holding conductor62are jointed to each other with penetration portions65formed by welding. It is noted that at the coil welding step130, other conductor joint portions60without the sensor unit61are also welded. That is, at the coil welding step130, the plural conductor joint portions60,60xare individually welded.

At the coil welding step130, heat generated by welding is transmitted to the thermistor63. However, as illustrated inFIG.13B, the joint end portion62aand the joint end portion62bof the sensor holding conductor62are apart from each other so that the heat can be released to the gap S to enhance heat dissipation of the joint end portions62aand62b, thereby protecting the thermistor63from the heat generated by welding. Moreover, the joint end portions62aand62bof the sensor holding conductor62are elongated to make the thermistor63apart from welding locations indicated by the symbol X so that the thermistor63can be protected from the heat generated by welding.

As described above, the sensor unit61including the sensor holding conductor62and the thermistor63is formed and attached to the conductor joint portion60xso as to facilitate attachment of the thermistor63to the stator coil SC. That is, when the thermistor63is attached to the stator coil SC, the thermistor63is handled not solely but as the sensor unit61. This notably facilitates handling of the thermistor63in the manufacturing process.

It is needless to say that the disclosure is not limited to the foregoing embodiments and various modifications can be made thereto within the scope that does not depart from the gist thereof. In the foregoing description, the sensor unit61is attached to the conductor joint portion60xincluding the two segment coils C1and C2. However, this is not to be construed in a limiting sense. The sensor unit61may be attached to a conductor joint portion including three or more segment coils40. That is, in the foregoing description, the plural segment coils40are connected in series to constitute each of the phase coils Cu, Cv, and Cw. However, this is not to be construed in a limiting sense. The plural segment coils40may be connected in parallel to constitute each of the phase coils Cu, Cv, and Cw. For example, when the two segment coils40are connected in parallel, the four segment coils40form a conductor joint portion. In this manner, even in the case of forming a conductor joint portion including three or more segment coils40, the sensor unit61is interposed between the segment coils40that constitute the conductor joint portion so as to appropriately detect the temperature of the stator coil SC.

In the foregoing description, in view of detecting the temperature of the stator coil SC at a location where a higher degree of temperature is obtained, the sensor unit61is disposed on the conductor joint portion60xbelonging to the second joint portion group G2. However, this is not to be construed in a limiting sense. For example, depending upon a temperature distribution of the stator coil SC that generates heat, the sensor unit61may be disposed on the conductor joint portion60belonging to the first joint portion group G1. In the foregoing description, the thermistor63is used as the temperature sensor. However, this is not to be construed in a limiting sense. Other temperature sensors may be used. In the foregoing description, the conductor joint portions60are welded by arc welding such as TIG welding. However, this is not to be construed in a limiting sense. The conductor joint portions60may be welded by laser welding, for example. It is noted that in the example illustrated inFIG.1, cooling oil is supplied to the coil end Ce of the stator coil SC. However, this is not to be construed in a limiting sense. The disclosure is applicable to the stator10including other cooling structures.

In the illustrated example, the eight segment coils40are inserted into each slot. However, this is not to be construed in a limiting sense. For example, more than eight segment coils40may be inserted into each slot, and less than eight segment coils40may be inserted into each slot. In the foregoing description, the stator core15where the number of the slots is 48 is used. However, this is not to be construed in a limiting sense. The stator core15with another number of the slots may be used.