JP2024059321A - Rotating electric machine stator - Google Patents

Abstract

[Problem] To effectively reduce the axial size of a stator due to coil end portions. [Solution] A stator for a rotating electric machine is disclosed, which includes a stator core, and a stator coil formed by joining multiple coil pieces having a rectangular cross section and including a U-shape, and wound around the stator core, the multiple coil pieces have slot insertion portions inserted into slots of the stator core, and transition portions extending in the circumferential direction in a manner that connects pairs of slot insertion portions axially outside an end face of the stator core, the transition portions including non-joining type transition portions that do not have joints between the coil pieces, and the non-joining type transition portions have bent portions that bend radially inward or outward. [Selected Figure] Figure 3

Description

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

A known technique involves inserting a U-shaped slot insertion portion of a coil piece into a slot in a stator core, bending the portion of the coil piece exposed from the slot (the portion of the coil piece related to the coil end portion) in the circumferential direction, and overlapping the tips of the bent portions of multiple coil pieces into a C-shape and welding them together.

JP 2019-122187 A

However, while the above-mentioned conventional technology can reduce the axial size of the stator due to the coil end portions by bending the coil piece portions related to the coil end portions in the circumferential direction, it is difficult to further reduce the axial size.

Therefore, in one aspect, the present disclosure aims to effectively reduce the axial size of the stator caused by the coil end portion.

In one aspect, a rotor includes a stator core;
a stator coil formed by combining a plurality of coil pieces having a rectangular cross section and including a U-shape, and wound around the stator core;
The coil pieces include
a slot insertion portion to be inserted into a slot of the stator core;
a bridge portion extending in a circumferential direction so as to connect a pair of the slot insertion portions on an axially outer side of an end face of the stator core,
The transition portion includes a non-joint type transition portion that does not have a joint portion between the coil pieces,
There is provided a stator for a rotating electric machine, wherein the non-coupled transition portion has a bent portion that is bent radially inward or radially outward.

In one aspect, the present disclosure makes it possible to effectively reduce the axial size of the stator due to the coil end portion.

1 is a cross-sectional view showing a schematic cross-sectional structure of a motor according to an embodiment; FIG. 2 is a side view of the stator of the present embodiment. FIG. FIG. FIG. 2 is a perspective view showing a single coil piece in a single component state. 5 is a perspective view showing a state in which the coil piece of FIG. 4 is assembled to a stator core. FIG. 13 is a diagram showing another example of a coil piece. FIG. 4 is a cross-sectional view of a portion including a transition portion. FIG. 11 is an explanatory diagram of a bending process part of a transition part. FIG. 11 is a perspective view showing a configuration of a coil end portion according to a comparative example. 4A and 4B are diagrams showing an example of a cross-sectional shape of a stator coil in a slot of a stator core; FIG. 11 is a cross-sectional view showing the configuration of a coil end portion according to another embodiment.

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

Figure 1 is a cross-sectional view that shows a schematic cross-sectional structure of a motor 1 (an example of a rotating electric machine) according to one embodiment.

Motor 1 may be a motor for driving a vehicle, such as that used in a hybrid vehicle or an electric vehicle. However, motor 1 may also be used for any other purpose.

The motor 1 is an inner rotor type, and the stator 21 is provided so as to surround the radial outside of the rotor 30. The radial outside of the stator 21 is fixed to the motor housing 10. The stator 21 has a stator core 211 made of, for example, a circular magnetic laminated steel plate, and a plurality of slots 2111 (see FIG. 5) in which the stator coils 212 are wound are formed on the radial inside of the stator core 211. Note that the stator 21 is illustrated diagrammatically in FIG. 1, and the details of the stator 21 will be described later with reference to FIG. 2A and subsequent figures.

The rotor 30 is disposed radially inside the stator 21. The rotor 30 includes a rotor core 32 and a rotor shaft 34.

The rotor core 32 is fixed to the radially outer surface of the rotor shaft 34 and rotates together with the rotor shaft 34. The rotor core 32 has an axial hole 320 into which the rotor shaft 34 is fitted. The rotor core 32 may be fixed to the rotor shaft 34 by shrink fitting, press fitting, or the like. For example, the rotor core 32 may be connected to the rotor shaft 34 by a key connection or a spline connection. The rotor shaft 34 is rotatably supported in the motor housing 10 via bearings 14a and 14b. The rotor shaft 34 defines the rotating shaft 12 of the motor 1.

The rotor core 32 is formed, for example, from laminated steel plates of a circular magnetic material. A plurality of permanent magnets (not shown) may be provided inside the rotor core 32. End plates 35A, 35B may be provided on both axial end surfaces of the rotor core 32. In a modified example, the rotor core 32 may be formed from a green compact in which magnetic powder is compressed and solidified.

Note that, although FIG. 1 shows a motor 1 having a specific structure, the structure of the motor 1 is not limited to such a specific structure. For example, in FIG. 1, the rotor shaft 34 is hollow, but it may be solid.

Next, the stator 21 of this embodiment will be described in detail with reference to Figure 2A onwards. Note that in Figure 2A etc., for ease of viewing, only some of the parts with the same attribute may be given reference symbols.

Figure 2A is a side view of the stator 21 of this embodiment, Figure 2B is a plan view (axial plan view) of the stator 21, and Figure 3 is a perspective view of the stator 21. Figure 4 is a perspective view showing one coil piece 20 in a single state. Figure 5 is a perspective view showing the coil piece 20 of Figure 4 assembled to the stator core 211. Figure 6 is a view showing a coil piece 20A according to another example. Note that in Figure 6, the coil piece 20A is shown in a state prior to processing for the bent portion (bent portion bent in the radial direction) described below.

In the following description, the axial direction refers to the direction in which the central axis of the stator 21 (= rotating shaft 12) extends, and the radial direction refers to the radial direction centered on the central axis. Therefore, the radially outer side refers to the side away from the central axis, and the radially inner side refers to the side toward the central axis. Additionally, the axially outer side refers to the side away from the axial center of the stator 21, and the axially inner side refers to the side approaching the axial center of the stator 21. Additionally, the circumferential direction corresponds to the direction of rotation around the central axis.

The stator 21 includes a stator core 211 made of, for example, a circular ring-shaped laminated steel plate of a magnetic material, and a stator coil 212 is wound around the stator core 211. A plurality of slots 2111 into which the stator coils 212 are inserted are formed on the radially inner side of the stator core 211. A plurality of slots 2111 are formed at equal intervals in the circumferential direction. The number and shape of the slots 2111 are arbitrary.

The stator coil 212 may be formed by joining together a number of coil pieces 20 as shown in FIG. 4, for example. The coil pieces 20 include a rectangular wire having a rectangular cross section (specifically, a rectangle). The rectangular wire may be made of a highly conductive metal such as copper or aluminum. The coil pieces 20 may be in the form of a rectangular wire covered with an insulating coating.

The coil piece 20 includes a U-shaped shape. The U-shaped shape is formed by two slot insertion parts 230 inserted into the slots of the stator core and circumferential crossover parts 234, 236 connecting the two slot insertion parts. In the example shown in FIG. 4, one coil piece 20 has a U-shaped coil part for four turns every 90 degrees, but the configuration of one coil piece 20 is arbitrary as long as it has a U-shaped shape. For example, one coil piece 20 may be replaced with the coil piece 20A shown in FIG. 6, in which case the coil piece 20A has a U-shaped shape of the minimum unit of one turn. That is, the coil piece 20A is formed by two slot insertion parts 230A for one turn and crossover parts 234A, 236A for one turn. The crossover part 236A is formed by bending the end in the circumferential direction (see angle α).

The transition portion 234 extends circumferentially axially outward from the end face of the stator core 211 on one axial side, forming the coil end portion 220 (see FIG. 1). The transition portion 236 extends circumferentially axially outward from the end face of the stator core 211 on the other axial side, forming the coil end portion (no reference number given in FIG. 1). The transition portion 234 may be on the non-lead side or the lead side. The transition portions 234 and 236 are each connected to the slot insertion portion 230 and are portions that protrude axially outward from the axial end face of the stator core 211 and connect two circumferentially separated slot insertion portions 230.

In one coil piece 20, both of the crossover portions 234 and 236 are non-bonded crossover portions that do not have a joint between the coil pieces. On the other hand, in the case of the coil piece 20A shown in FIG. 6, of the crossover portions 234A and 236A, only the crossover portion 234A is a non-bonded crossover portion that does not have a joint between the coil pieces. The crossover portion 236A of one coil piece 20A is joined to the crossover portion 236A of the other coil piece 20A by welding or the like.

Next, while still referring to Figures 1 to 5, we will now refer to Figures 7 onwards to provide further details about the stator coil 212.

Figure 7 is a cross-sectional view of a portion including the transition portion 234, taken along a plane including the central axis.

In this embodiment, the transition portion 234 has bent portions 71 and 72 that are bent in the radial direction, as shown in FIG. 7.

In the example shown in FIG. 7, the stator core 211 has 8 turns of slot insertion portion 230 (not visible in FIG. 7) inserted into each slot 2111. All of the 8 turns of the crossover portion 234 continuing from the 8 turns of the slot insertion portion 230 have bent portions 71 and 72. In this case, of the 8 turns of the crossover portion 234, the 4 turns of the radially inner crossover portion 234 continuing from the slot insertion portion 230 inserted on the radially inner side have a bent portion 71 bent radially inward. On the other hand, of the 8 turns of the crossover portion 234, the 4 turns of the radially outer crossover portion 234 continuing from the slot insertion portion 230 inserted on the radially outer side have a bent portion 72 bent radially outward.

The bent portions 71 and 72 may be pre-processed (pre-formed) before the coil pieces 20 are assembled to the stator core 211.

In the following, to distinguish between them, the transition portion 234 having the bent portion 71 is also referred to as the "radially inner transition portion 234-1," and the transition portion 234 having the bent portion 72 is also referred to as the "radially outer transition portion 234-2."

In this embodiment, eight turns are shown as an example, but the number of turns is arbitrary. Also, although the bending sections 71, 72 are realized with the same number of turns, they may be different. For example, in a modified example, of the eight-turn crossover section 234, only one turn continuing from the slot insertion section 230 inserted radially inward may be the radially inner crossover section 234-1 (having the bending section 71 bent radially inward), and the rest may all be the radially outer crossover section 234-2. Also, in another modified example, only a portion of the eight-turn crossover section 234 may have the bending section 71 and/or the bending section 72.

Figure 8 is an explanatory diagram of the bent portions 71, 72 of the transition portion 234, and is a perspective view partially showing the bent portions 71, 72 for four turns of one coil piece 20.

The radially inner crossover portion 234-1 has bent portions 71 on both circumferential sides, as shown in FIG. 8. The bent portions 71 on both circumferential sides may be formed simultaneously by the same bending process radially inward. The bent portions 71 are preferably formed by bending at 90 degrees, as shown in FIG. 7. This allows the axial size of the radially inner crossover portion 234-1 to be reduced compared to bending at less than 90 degrees (i.e., the axially outermost position of the radially inner crossover portion 234-1 can be extended axially inward).

The bent portion 71 can be formed by so-called flatwise bending. In this case, in part or all of the radially inner crossover portion 234-1, the bending R of the bent portion 71 may start from an axial position corresponding to the axial end face of the stator core 211. This allows the axial size of the radially inner crossover portion 234-1 to be reduced compared to when the bending R starts axially outside the axial position corresponding to the axial end face of the stator core 211.

The radially inner crossover portion 234-1 has, in addition to the bent portion 71, a circumferentially bent portion 75 on the side closer to the apex 77 than the bent portion 71. The circumferentially bent portion 75 is, for example, an edgewise bend, and may have a relatively large bend radius due to molding constraints, and the bend angle may be significantly greater than 90 degrees.

The radially outer crossover portion 234-2 has bent portions 72 on both circumferential sides, as shown in FIG. 8. The bent portions 72 on both circumferential sides may be formed simultaneously by the same bending process radially outward. The bent portions 72, like the bent portion 71, are preferably formed by bending at 90 degrees, as shown in FIG. 7. This allows the axial size of the radially outer crossover portion 234-2 to be reduced compared to bending at less than 90 degrees.

The bent portion 72 can be formed by so-called flatwise bending. In this case, in part or all of the radially outer crossover portion 234-2, the bending R of the bent portion 72 may start from an axial position corresponding to the axial end face of the stator core 211. This allows the axial size of the radially outer crossover portion 234-2 to be reduced compared to when the bending R starts axially outside the axial position corresponding to the axial end face of the stator core 211.

In addition to the bent portion 72, the radially outer transition portion 234-2 has a circumferentially bent portion 76 on the side closer to the apex 78 than the bent portion 72. The circumferentially bent portion 76 is, for example, an edgewise bend, and may have a relatively large bend radius due to molding constraints, and the bend angle may be significantly greater than 90 degrees.

Here, the effects of this embodiment will be explained with reference to the comparative example shown in Figure 9.

Figure 9 is a perspective view showing the configuration of a coil end portion 220' according to a comparative example. In the comparative example, the coil piece 20' does not have a radially bent portion such as bent portions 71 and 72, but instead has a bent portion 75' such as circumferentially bent portions 75 and 76. Note that the bend R of the bent portion 75' may start from an axial position corresponding to the axial end face of the stator core 211.

In this comparative example, the bent portion 75' is edgewise bent, and due to forming constraints, it is necessary to have a relatively large bend R, which tends to increase the axial size. In addition, the crossover portions are stacked in the axial direction, which tends to increase the axial size. In other words, in a configuration that attempts to reduce the axial size of the coil end portion 220' only by using the bent portion 75', there is a limit to the amount of reduction that can be achieved.

In contrast, according to this embodiment, as described above, by having radially bent portions 71 and 72, the axial size of coil end portion 220 can be efficiently reduced compared to the comparative example. In particular, in this embodiment, the structure in which each transition portion is stacked in the axial direction according to the comparative example is changed to a structure in which transition portion 234 is stacked in the radial direction, so that the axial size of coil end portion 220 can be efficiently reduced.

In addition, according to this embodiment, multiple bridge sections 234 continuing from multiple slot insertion sections 230 inserted into one slot 2111 form a radially inner bridge section 234-1 and a radially outer bridge section 234-2. That is, for one slot 2111, radially inward bending sections 71 and radially outward bending sections 72 are distributed and arranged radially inside and outside. As a result, compared to a case in which multiple bridge sections 234 from within one slot 2111 all have only one of the bending sections 71 or the bending section 72, it is possible to suppress axial stacking, and therefore the axial size of the coil end section 220 can be efficiently reduced.

In this embodiment, the radially bent portions 71, 72 are preferably arranged around the entire circumference of the stator coil 212. This allows the axial size of the coil end portion 220 to be efficiently reduced around the entire circumference of the stator 21.

In the example shown in FIG. 7, the radially inner jumper section 234-1 has the same four turns as the radially outer jumper section 234-2, but since the start position of the bend R is on the axially outer side, the axial size is larger than that of the radially outer jumper section 234-2. In this way, for example, when the required clearance with the surrounding members is relatively large, it is possible not to minimize the axial size of a part of the circumferential direction and/or a part of the radial direction of the coil end section 220, taking into account workability, etc. Also, for example, when the required clearance with the surrounding members is relatively large on the radially inner side, the radially inner jumper section 234-1 may handle more than half of the eight turns. This allows the axial size of the coil end section 220 to be efficiently reduced according to the required clearance with the surrounding members.

However, in this embodiment, since the radially bent sections 71 and 72 are provided, as described above, the axial size of the coil end section 220 can be reduced, but the radial size tends to increase.

However, generally, the rotor core (not shown) on the radial inner side of the stator core 211 is not arranged in a manner that protrudes relatively far axially outward from the axial end face of the stator core 211. Therefore, the increase in the radial size of the coil end portion 220 toward the radial inner side of the stator core 211 is unlikely to be a problem. In addition, since the stator core 211 has a back yoke radially outward from the slots 2111, the increase in the radial size of the coil end portion 220 toward the radial outer side of the stator core 211 is tolerable to a certain extent. In other words, according to this embodiment, the dead space on the radial inner side and the radial outer side is effectively utilized, making it possible to efficiently reduce the axial size of the coil end portion 220.

Next, while still referring to FIG. 7, we will now refer to FIG. 10 and FIG. 11 to explain preferred examples of the cross-sectional shape of the stator coil 212.

Figure 10 is a diagram showing an example of the cross-sectional shape of the stator coil 212 in the slot 2111 of the stator core 211. Figure 11 is a cross-sectional view showing the configuration of the coil end portion 220B according to another embodiment, and is a cross-sectional view for comparison with Figure 7.

In this embodiment, as shown in Figures 7 and 10, the aspect ratio of the rectangular cross section of the stator coil 212 at the bridge portion 234 is different from the aspect ratio of the rectangular cross section at the slot insertion portion 230.

In the example shown in Figures 7 and 10, in the slot insertion portion 230, as shown in Figure 10, the long side (the side along the circumferential direction) is significantly larger than the short side (the side along the radial direction), for example, about three times larger. In contrast, the transition portion 234 is approximately square (i.e., the aspect ratio is approximately 1). This makes it possible to reduce the radial increase in size of the coil end portion 220 caused by the transition portion 234 (bent portions 71, 72) while ensuring the necessary space factor within the slot 2111.

In another embodiment shown in FIG. 11, there are bent portions 71B and 72B corresponding to the bent portions 71 and 72, but the aspect ratio of the rectangular cross section of the transition portion 234B is the same as the aspect ratio of the rectangular cross section of the slot insertion portion 230. In this case, as shown in FIG. 11, the radial increase in size of the coil end portion 220B due to the transition portion 234B can be significant. In particular, as shown in FIG. 11, if the transition portion 234B extends radially outward from the outer circumferential surface 2114 of the stator core 211, it becomes difficult to ensure the necessary clearance from the motor housing 10 (see FIG. 1) on the outer circumferential side of the stator core 211 without increasing the radial size of the motor 1 as a whole, including the motor housing 10.

In contrast, according to this embodiment, as described above, the aspect ratio of the crossover portion 234 is set so that the radial width of the rectangular cross section is small, so that the radial increase in the size of the coil end portion 220 due to the crossover portion 234 (bending portions 71, 72) can be reduced. In particular, as shown in FIG. 7, the radially outer crossover portion 234-2 does not reach the radially outer side of the outer peripheral surface 2114 of the stator core 211, but remains radially inner than the outer peripheral surface 2114 of the stator core 211. That is, the outermost position of the radially outer crossover portion 234-2 is located radially inner than the outer peripheral surface 2114 of the stator core 211. In other words, in this embodiment, the aspect ratio of the rectangular cross section of the radially outer crossover portion 234-2 may be set so that the crossover portion 234 (coil end portion 220) does not reach the radially outer side of the outer peripheral surface 2114 of the stator core 211 due to the bending portion 72. Note that the "outer peripheral surface 2114 of the stator core 211" here refers to the outer peripheral surface 2114 of the base portion of the stator core 211, and uneven portions (e.g., welding grooves, etc.) that may be set on the outer peripheral surface 2114 of the base portion may be ignored. For example, the stator core 211 may have a radial protrusion that is fixed to the motor housing 10 (see FIG. 1), but the outer peripheral surface 2114 of the base portion refers to the outer peripheral surface of the portion excluding such protrusion.

In this embodiment, the aspect ratio of the transition portion 234 is such that the radial width of the rectangular cross section is small, but if reducing the axial size is a priority, the aspect ratio of the transition portion 234 may be such that the axial width of the rectangular cross section is small. Also, the aspect ratio may be different between the radially inner transition portion 234-1 and the radially outer transition portion 234-2. For example, the radially outer transition portion 234-2 may have a different aspect ratio of rectangular cross section from the slot insertion portion 230, but the radially inner transition portion 234-1 may have the same aspect ratio of rectangular cross section as the slot insertion portion 230.

In this embodiment, the aspect ratio of the rectangular cross section of the transition portion 234 may be different from that of the slot insertion portion 230 throughout its entirety, but preferably only a portion including the apexes 77 and 78 may have a different aspect ratio. In other words, the transition portion 234 may preferably have a rectangular cross section aspect ratio different from that of the slot insertion portion 230 only in the range not including the bent portions 71 and 72. This makes it possible to make the aspect ratio of the rectangular cross section of the transition portion 234 different from that of the slot insertion portion 230 without impairing the formability of the bent portions 71 and 72.

Although each embodiment has been described in detail above, it is not limited to a specific embodiment, and various modifications and changes are possible within the scope of the claims. It is also possible to combine all or some of the components of the above-mentioned embodiments.

For example, in the above-described embodiment, the bent portions 71 and 72 are bent portions formed by bending, but they may also be bent portions formed in a similar shape by a method that does not involve bending, such as casting or forging.

21: stator (stator for rotating electrical machines), 211: stator core, 2114: outer periphery, 2111: slot, 212: stator coil, 20, 20A: coil piece, 230: slot insertion part, 234, 234A: transition part (non-bonded transition part), 71, 72: bending part (bent part)

Claims (6)

A stator core;
a stator coil formed by combining a plurality of coil pieces having a rectangular cross section and including a U-shape, and wound around the stator core;
The coil pieces include
a slot insertion portion to be inserted into a slot of the stator core;
a bridge portion extending in a circumferential direction so as to connect a pair of the slot insertion portions on an axially outer side of an end face of the stator core,
The transition portion includes a non-joint type transition portion that does not have a joint portion between the coil pieces,
The non-coupled type transition portion has a bent portion that is bent radially inward or radially outward. The plurality of non-bonded transition portions include
A radially inner transition portion continuing from the slot insertion portion that is inserted into the radially inner side of each slot;
a radially outer jumper portion that is continuous from the slot insertion portion that is inserted into the radially outer side of each slot,
The radially inner transition portion has the bent portion bent radially inward,
The stator for a rotating electric machine according to claim 1 , wherein the radially outer transition portion has the bent portion that is bent radially outward. The stator for a rotating electric machine according to claim 1, wherein the outermost diameter position of the transition portion having the bent portion is located radially inward from the outer circumferential surface of the stator core. The stator for a rotating electric machine according to claim 1, wherein the bend is in the form of a 90-degree bend in which the bend R starts from an axial position corresponding to the axial end face of the stator core. The stator for a rotating electric machine according to claim 1, wherein the aspect ratio of the rectangular cross section of the stator coil at the transition portion having the bent portion is different from the aspect ratio of the rectangular cross section at the slot insertion portion. The stator for a rotating electric machine according to any one of claims 1 to 5, wherein the bent portion of the non-coupled transition portion is disposed around the entire circumference of the stator coil.