Stator of rotary electric machine

Abstract

To provide a configuration to connect a plurality of conducting wire segments to wind a single coil on the teeth of a stator core in a stator of a rotary electric machine, and to reduce as much as possible variations in the bond strength and electric resistance between the connected two conducting wire segments.SOLUTION: In a stator, a coil is wound on stator teeth projecting radially inward of a stator core. A plurality of substantially U-shaped conducting wire segments are connected to each other into a single coil. A convex or concave leading end of the conducting wire segment is fitted to a concave or convex end of a connecting member or a concave or convex leading end of another conducting wire segment, and thereby the plurality of conducting wire segments are sequentially connected to each other. One of an outer surface of a convex part 10 of one of the conducting wire segment and the connecting member fitted to the other, and an inner surface of a concave part 20 opposite thereto, has a substantially polygonal cross-sectional shape. The outer surface of the convex part and the inner surface of the concave part are in contact with each other only in a portion 15 on each surface of the substantially polygonal shape.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a stator of a rotating electrical machine, and more particularly, to a stator in which a coil configured by connecting a plurality of conductor segments is wound around teeth (stator teeth) of a stator core.

Background Art

[0002] As a method of winding a coil around teeth of a stator core of a stator of a rotating electrical machine, both ends of a plurality of substantially U-shaped conductor segments are inserted into slots between stator teeth from both sides in the axial direction of the center axis of the stator, and in the slots, the tips of the opposing conductor segments are sequentially connected to form a state where a single coil is wound around the stator teeth. In such a method, in particular, various configurations have been proposed for connecting the tips of opposing conductor segments without using a troublesome welding process or the like. For example, in Patent Document 1, a configuration is proposed in which the tips of opposing conductor segments formed in a convex shape are respectively fitted into concave both ends of a tubular connecting member and connected to each other.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As described above, in a configuration where a single coil wound around a stator tooth is formed by connecting the tips of a plurality of conductor segments, whether the tips of two conductor segments formed in a convex or concave shape are connected via a connecting member having a concave or convex end that fits into them, or whether the convex tip formed on one of the two conductor segments to be connected is inserted into the concave tip formed on the other conductor segment, the surfaces that come into contact with each other at the fitting portion of the conductor segment or the connecting member are formed so as to be fresh surfaces with exposed metal atoms. When the tips are fitted together, such fresh surfaces are crimped to form a metallic bond between the opposing surfaces, resulting in adhesion, which strengthens the connection between the conductor segments. In this regard, when the outer shape of the convex portion inserted into the connecting portion of the above-described conductor segment is polygonal (typically, quadrilateral), if the convex portion and the concave portion are designed such that the entire outer surface of the convex portion contacts the entire opposing inner surface of the concave portion of the fitting destination, it has been experimentally found that the variation in the bonding strength and electrical resistance between the connected conductor segments increases. This is presumably because when the outer surfaces of the convex portion and the inner surfaces of the concave portion opposing them come into contact with each other over the entire area, the rigidity of the concave portion changes depending on the position, and the pressing force on the contact surface becomes stronger at the corners where the polygonal faces of the concave portion intersect and weaker in the flat central region of each face, resulting in variation within each face. When such variation in bonding strength and electrical resistance is large, the characteristics of the coil wound around the stator tooth will also vary, which can lead to a decrease in the accuracy of the control of the rotating electrical machine.

[0005] Therefore, when the inventor of the present invention conducted various studies on the shape of the fitting portion between such wire segments, it was found that on each surface of the convex portion at the connecting portion of the wire segments and the inner surface of the concave portion facing it, only a part of the flat surface, excluding the corner portions of the polygon, contacts over the entire area. When the outer surface of each convex portion and the inner surface of each concave portion are shaped like this, it was found that the variation in the joining strength and electrical resistance between the connected wire segments is significantly reduced. This is presumably because the contact surface between the outer surface of each convex portion and the inner surface of each concave portion consists only of the flat surface excluding the corner portions, so that the pressing force within the contact surface can be made substantially uniform, and the ratio of the area where adhesion has occurred on the contact surface has increased. This finding is utilized in the present invention.

[0006] In view of the above circumstances, the main problem of the present invention is, in the stator of a rotating electrical machine, in a configuration where a plurality of wire segments are connected to wind a single coil around the teeth of a stator core, to suppress as much as possible the variation in the joining strength and electrical resistance between two connected wire segments.

Means for Solving the Problem

[0007] According to the present invention, the above problem is solved by a stator in which a coil is wound around stator teeth protruding radially inward of a stator core of a rotating electrical machine, wherein the coil is a coil formed by connecting a plurality of substantially U-shaped wire segments in series, and the convex or concave tip of the wire segment fits into the concave or convex end of a connecting member or the concave or convex tip of another said wire segment, whereby the plurality of wire segments are sequentially connected. In this configuration, the shape of the cross-section of one of the outer surface of the convex portion and the inner surface of the concave portion that fit with each other of the wire segment or the connecting member is substantially polygonal, and the outer surface of the convex portion and the inner surface of the concave portion are achieved by a stator in which only a part of each surface of the substantially polygonal shape is in contact.

[0008] In the above configuration, the "rotating electrical machine" may be any type of rotating electrical machine (generator, motor, motor-generator) that uses a stator wound with coils. In the present invention, the "coil" is formed by successively connecting a plurality of conductor segments, that is, wires formed of a conductive material (such as copper or aluminum) in a single helical shape as described above. In the above stator core, a plurality of coils may be wound. In that case, each coil is formed by connecting a plurality of conductor segments in a single helical shape (that is, the stator of the present invention includes the case where a plurality of coils are wound around the stator core). Specifically, the connection of each conductor segment may be achieved by successively repeating the insertion of the convex tip of the conductor segment into the concave end of the connecting member, or into the concave tip of another conductor segment, or the fitting of the convex end of the connecting member of the concave tip of the conductor segment. The connecting member may also be formed of the same material as the conductor segment.

[0009] In the present invention, at the connection portion between the conductor segment and the connecting member or at the connection portion between the tips of the conductor segments, the cross-sectional shape of one of the outer surface of the convex portion that fits with each other and the inner surface of the concave portion facing it is substantially polygonal, and only a part of the outer surface of the convex portion and the inner surface of the concave portion are in contact with each other on each surface of the substantially polygonal shape (the contact surface is a flat surface). Then, as understood from the experimental results described in the column of the following embodiments, the area where adhesion occurs at the contact surface between the outer surface of the convex portion and the inner surface of the concave portion facing it becomes larger (the outer surface of the convex portion and the inner surface of the concave portion facing it are each formed on a fresh surface), and the variation in the bonding strength and electrical resistance between the conductor segments can be significantly suppressed compared to the case where the entire area of the outer surface of the convex portion and the inner surface of the concave portion facing it are in contact.

[0010] In an embodiment of the present invention, the inner surface of the concave portion of the wire segment or the connecting member may be formed in a substantially polygonal shape in its cross section, and the outer surface of the convex portion of the wire segment or the connecting member to be fitted therein may be formed so as to partially protrude radially outward and contact the inner surface of the concave portion. Alternatively, the outer surface of the convex portion of the wire segment or the connecting member may be formed in a substantially polygonal shape in its cross section, and the inner surface of the concave portion of the wire segment or the connecting member to be fitted thereto may be formed so as to partially protrude radially inward and contact the outer surface of the convex portion. Further, the portion protruding radially outward or inward of the convex portion or the concave portion may be formed over the entire length of the convex portion or the concave portion in the axial direction of the wire segment or the connecting member, or may be formed only in part.

[0011] As will be described later, it has been experimentally found that in the fitting of the convex portion and the concave portion, the rate of occurrence of adhesion (adhesion rate) on the contact surface depends on the pressing force. Therefore, in order to adjust the pressing force in the fitting of the convex portion and the concave portion so that the adhesion rate becomes higher, the dimensions of the convex portion and the concave portion may be appropriately adjusted. According to experiments, it has been observed that the thicker the wall thickness of the concave portion (the length between the outer surface and the inner surface), the higher the ratio of the area where adhesion occurs.

Advantages of the Invention

[0012] Thus, according to the configuration of the present invention, by bringing only a partial region into contact on the opposing surfaces of the convex portion and the concave portion that are fitted to each other at the connecting portion of the wire segment, the variation in the connecting strength and the electrical resistance at the connecting portion of the wire segment is suppressed. According to such a configuration, the characteristics of the coil wound around the stator teeth are made more uniform, so that it is expected that the accuracy in the control of the rotating electrical machine is improved and the operating stability of the rotating electrical machine is improved.

[0013] Other objects and advantages of the present invention will become apparent from the following description of the preferred embodiments of the present invention.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Explanation of Signs

[0015] Co… Coil, SC… Wire Segment, St… Stator Tooth, SS… Tip of Wire Segment, JT… Connecting Member, DS… Enlarged Diameter Portion of Wire Segment, 10… Convex Portion, 15… Contact Surface, 20… Concave Portion

Best Mode for Carrying Out the Invention

[0016] The present invention will be described in detail below with reference to the accompanying drawings in several preferred embodiments. In the figures, the same reference numerals indicate the same parts.

[0017] Outline of the coil wound around the stator teeth In the stator of the rotating electrical machine according to this embodiment, as in the case of Patent Document 1, the coil wound around a plurality of teeth protruding radially inward of the annular stator core is a coil formed by sequentially connecting wire segments made of a plurality of conductive materials in a spiral manner. More specifically, as schematically depicted in FIG. 1, in this embodiment, a plurality of substantially U-shaped wire segments SC are arranged from both sides in the axial direction of the stator core such that their both ends face each other and surround the stator teeth St (FIG. 1(A)). Thereafter, the wire segments SC are brought closer to each other, and as shown in FIG. 1(B), the tips of the wire segments SC are sequentially connected to the tips of another wire segment SC facing each other, and are wound around the stator teeth St in the state of a single coil Co. Note that the winding pattern of the coil around the stator teeth may be arbitrary (concentrated winding, distributed winding, etc.).

[0018] The wire segment SC is formed by appropriately bending or curving a wire made of a conductive material such as copper or aluminum into a U shape, and its surface is in a state where an insulating coating is applied except for the tip portion. The cross section of the wire segment may be polygonal, for example, a rectangle of 3 mm×2 mm or 3 mm×4 mm, and the length may be, for example, 100 to 150 mm, but is not limited thereto.

[0019] Mode of connection of the conductor segments The connection between the tips of the plurality of the above-described wire segments may be achieved in various manners. Specifically, for example, in a first manner, as shown in FIG. 1(C), the convex tips SS1 and SS2 of two wire segments SC1 and SC2 are respectively inserted into the concave ends of a connecting member JT which may be a hollow tube, and the two wire segments SC1 and SC2 may be connected. Also, in a second manner, as shown in FIG. 1(D), the convex tip SS1 of the wire segment SC1 is inserted into the concave tip SS2 of the wire segment SC2, and the two wire segments SC1 and SC2 may be connected. In a third manner, as shown in FIG. 1(E), the concave tips SS1 and SS2 of two wire segments SC1 and SC2 are respectively fitted to the convex ends of the connecting member JT, and the two wire segments SC1 and SC2 may be connected. And in a fourth manner, as shown in FIG. 1(F), the convex tip SS1 of the wire segment SC1 is inserted into the concave end of the connecting member JT, and the concave tip SS2 of the wire segment SC2 is fitted to the convex end of the connecting member JT, and the two wire segments SC1 and SC2 may be connected. In addition, in the above configuration, the outer surface of the convex portion and the inner surface of the concave portion are respectively new surfaces with exposed metal atoms, and by pressing the outer surface of the convex portion and the inner surface of the concave portion against each other, a metal bond is formed between the surfaces (adhesion), ensuring conduction and connection between the wire segments.

[0020] Relationship between the shape of the connection part of the conductor segments and the degree of adhesion Regarding the configuration in which the convex portion and the concave portion at the tip of the wire segment or the end of the connecting member are fitted together to cause adhesion between their surfaces, as described above, the inventor of the present embodiment studied and found that when the surfaces of the convex portion and the concave portion to be fitted come into contact with each other over the entire area, as shown in the experimental examples described later, the ratio of the area where adhesion occurs on the contact surface (adhesion rate) becomes small, and as a result, it was found that the variations in the joint strength (the force required to separate) and the electrical resistance value between the wire segments increase. As already mentioned, the cross-sectional shapes of the outer surface of the convex portion and the inner surface of the concave portion are substantially polygonal. When each outer surface of the convex portion and the opposing inner surface of the concave portion come into contact with each other over the entire area, the rigidity of the concave portion changes depending on the position, and the pressing force on the contact surface becomes stronger at the corners where the polygonal faces of the concave portion intersect and weaker in the flat central region of each face. This is considered to be because the pressing force varies within each face.

[0021] Therefore, the inventor of the present embodiment conducted various studies on the shapes of the convex portion and the concave portion that would result in a higher adhesion rate. It was found that when the cross-sectional shape of one of the outer surface of the convex portion and the inner surface of the concave portion that are fitted to each other is substantially polygonal, and on each face of the substantially polygonal shape, the outer surface of the convex portion and the inner surface of the concave portion are in contact only in part, the adhesion rate increases, and the variations in the joint strength and the electrical resistance value between the wire segments become small.

[0022] Specifically, for example, first, as shown in FIG. 2(A), the cross-sectional shape of the convex portion 10 is generally cross-shaped, and the cross-shaped protruding flat tips of the convex portion 10 are respectively in contact with the central regions of each surface of the inner surface of the substantially square concave portion 20 to form the contact surfaces 15. Note that the contact surfaces 15 may extend over substantially the entire axial length of the convex portion 10. Alternatively, as shown in FIG. 2(B), the convex portion 10 has a cross-sectional shape that is generally grid-shaped, and the grid-shaped protruding flat tips of the convex portion 10 are respectively in contact with the portions near both edges of each surface of the inner surface of the substantially square concave portion 20 to form the contact surfaces 15. In these configurations, in the cross-section of the concave portion 20, the variation in contact in the vertical and horizontal directions is reduced, and the adhesion rate of each contact surface is improved. Also, as shown in FIGS. 2(C) and (D), for the convex portion 10 inserted into the concave portion 20, only the tip portion or the root portion thereof protrudes radially outward and is respectively in contact with the inner surface of the substantially square concave portion 20 to form the contact surfaces 15. In these configurations, the pressing force becomes more uniform in the axial direction of the convex portion 10, and the adhesion rate of each contact surface is improved. Further, as shown in FIG. 2(E), for each inner surface of the substantially square concave portion 20, the surfaces of the convex portion 10 having a substantially octagonal cross-sectional shape may be alternately in contact to form the contact surfaces 15. Alternatively, as shown in FIG. 2(F), a part of each inner surface of the substantially square concave portion 20 may protrude radially inward and contact each surface of the substantially square convex portion to form the contact surfaces 15. In the shapes of the convex portion and the concave portion exemplified above, the shape of the portion where the contact surface is not formed may be arbitrary. Also, in the convex portion and the concave portion, the portions protruding radially outward or inward may have an alternating fitting shape. As described above, by forming the contact surface between the convex portion and the concave portion at a part of the flat surface instead of the entire area of the outer surface of the opposing convex portion and the inner surface of the concave portion, as shown in the later experimental examples, the adhesion rate can be increased, and the variations in the joining strength and the electrical resistance value between the wire segments can be suppressed to be small.

[0023] In the processing of the tip of the wire segment, after the insulation coating of the wire segment is peeled off, the tip of the wire segment may be processed by forging. As a result, the hardness of the tip is improved, and burrs (foreign matters) during press-fitting can also be suppressed.

[0024] Incidentally, as will be exemplified later, the adhesion rate of the contact surface between the outer surface of the convex portion and the inner surface of the concave portion tends to increase as the pressing force on the contact surface becomes higher. Therefore, it is preferable that the outer dimensions of the convex portion, the inner dimensions of the concave portion, and the wall thickness (the thickness between the outer surface and the inner surface) are appropriately adjusted so that such a pressing force becomes sufficiently high.

[0025] Experimental example The effectiveness of this embodiment was confirmed by the following experimental examples. It should be understood that the following experimental examples illustrate the effectiveness of this embodiment and do not limit the scope of the present invention.

[0026] (a) Change in adhesion rate with respect to the ratio of the contact surface When fitting the convex tip of the wire segment into the concave end of the connecting member, the ratio of the area of the contact surface to the opposing area was variously changed to confirm the adhesion rate. The adhesion rate was determined by fitting the convex tip of the wire segment into the concave end of the connecting member and then, after half a day (within two days), pulling out the convex tip of the wire segment from the concave end of the connecting member and detecting the ratio of the area of the region where adhesion occurred. Incidentally, in the convex tip of the wire segment, the region where adhesion occurred can be confirmed by changing to white (see Fig. 3(C)).

[0027] Figs. 3(A) and (B) respectively show the adhesion rates when the ratio of the contact area between the convex portion and the concave portion is changed in the case where the wall thickness t of the concave end of the connecting member is 0.6 mm and 0.3 mm. As can be understood from the figure and the photograph of Fig. 3(C), it was observed that the adhesion rate was higher when the ratio of the contact area between the convex portion and the concave portion was 1 / 3 or 1 / 6 than when it was 1 (the entire opposing surface was in contact). It was also observed that the adhesion rate was higher when the wall thickness t of the concave end of the connecting member was thicker than when it was thinner.

[0028] (b) Variation of joint strength and electrical resistance value with respect to the ratio of the contact surface When fitting the convex tip of the wire segment into the concave end of the connecting member, the ratio of the area of the contact surface to the opposing area was variously changed. After fitting the convex tip of the wire segment into the concave end of the connecting member and after half a day (within two days), the force (joint strength) required to pull out the convex tip of the wire segment from the concave end of the connecting member and the electrical resistance value in the state where the wire segment and the connecting member were joined were measured. Referring to FIGS. 4(A) and (B), it was observed that for both the joint strength and the electrical resistance value, the variation was significantly reduced when the ratio of the contact area between the convex and concave portions was 1 / 6 rather than 1.

[0029] From the above experimental examples, it was confirmed that by bringing only a partial region into contact on the opposing surfaces of the convex and concave portions that are fitted to each other at the connecting portion of the wire segment, the variation in the connection strength and electrical resistance at the connecting portion of the wire segment is suppressed.

[0030] The above description has been made in relation to the embodiments of the present invention, but many modifications and changes are easily possible for those skilled in the art, and the present invention is not limited to only the embodiments illustrated above, and it will be apparent that the present invention can be applied to various devices without departing from the concept of the present invention.

Claims

【Claim 1】 A stator in which a coil is wound around a stator tooth protruding radially inward of a stator core of a rotating electrical machine, wherein the coil is formed by connecting a plurality of substantially U-shaped conductor segments in series, and the convex or concave tip of the conductor segment fits into the concave or convex end of a connecting member or the concave or convex tip of another said conductor segment, so that the plurality of conductor segments are connected in sequence. In this configuration, the shape of a cross section of one of the outer surface of the convex portion that fits with the other and the inner surface of the concave portion that faces it, among the conductor segment or the connecting member, is substantially polygonal, and the outer surface of the convex portion and the inner surface of the concave portion are in contact only in part on each surface of the substantially polygonal shape. A stator.

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