JP7845064B2 - stator - Google Patents

Description

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

In a stator with a segment structure, the tips of the conductor segments are joined together by welding at the coil ends. Furthermore, the tip of the conductor segment connected to the neutral point of the stator winding is joined to the neutral point busbar by welding (see, for example, Patent Document 1).

Japanese Patent Publication No. 2016-77026

The neutral busbar is welded to each phase's conductor segment and supported by the stator winding (conductor segment) through this joint. In this case, the joint between the conductor segment and the neutral busbar requires a higher joint strength than the joints between the conductor segments themselves. However, increasing the welding energy to enhance the joint strength between the conductor segment and the neutral busbar raises concerns about excessive heat buildup on the conductor segment side, potentially causing problems such as melting of the insulating coating.

This invention has been made in view of the above-mentioned problems, and its objective is to provide a stator that can properly connect a neutral point busbar to a conductor segment.

The following describes the means and effects of solving the above-mentioned problems.

Method 1 is,
A stator comprising: a stator core; a stator winding provided on the stator core and having a plurality of phase windings; and a neutral point busbar provided at the coil end of the stator winding, connected to the phase windings of each phase,
The stator winding is constructed using multiple conductor segments, each of which is connected to the others.
At the coil end, the tips of the conductor segments are joined by welding in an overlapping state, while the tip of the conductor segment connected to the neutral point of the stator winding and the busbar terminal of the neutral point busbar are joined by welding in an overlapping state.
The connection between the tip of the conductor segment and the busbar terminal is characterized in that the area of the cross-sectional surface of the busbar terminal is smaller than the conductor cross-sectional area of the conductor segment.

In a segmented stator, the ends of the conductor segments are joined by welding at the coil ends, overlapping each other. Furthermore, the end of the conductor segment connected to the neutral point of the stator winding is joined by welding to the busbar terminal of the neutral point busbar, overlapping each other. This joining connects the neutral point busbar to the conductor segment. In particular, at the joint between the conductor segment end and the busbar terminal, the cross-sectional area of the busbar terminal is smaller than the conductor cross-sectional area of the conductor segment.

In this case, during welding of the segment tips and busbar terminals, the busbar terminals become hotter than the segment tips due to the difference in cross-sectional area. This allows for a greater welding depth compared to welding the tips of the conductor segments together. In other words, while maintaining the same welding energy and other welding conditions for welding the tips of the conductor segments together and welding the segment tips and busbar terminals together, the welding depth can be increased in the case of welding the segment tips and busbar terminals. Comparing the joining of the tips of the conductor segments together with the joining of the segment tips and busbar terminals, the way loads are applied at each joint differs, and the latter may require greater joint strength; however, this method can adequately meet such requirements. As a result, the neutral point busbar can be properly joined to the conductor segments.

In means 2, as in means 1, the tip of the conductor segment and the busbar terminal each have a substantially rectangular cross-section, with one side of the tip of the conductor segment and the busbar terminal overlapping each other. The busbar terminal has a rectangular cross-section consisting of a long side and a short side, with the long side overlapping the tip of the conductor segment and having the same width as the tip.

In a configuration where the tip of a conductor segment and one side of a busbar terminal are joined with overlapping edges, the longer side of the busbar terminal, which has a rectangular cross-section, is overlapped with the tip of the conductor segment, and the width of the longer side of the busbar terminal and the tip of the conductor segment are made equal. In this case, even though the cross-sectional areas of the tip of the conductor segment and the busbar terminal are different, the overlapping of the joining portion can be performed in the same way as the welding portion between the tips of the conductor segments. This allows for efficient welding.

In means 3, in means 1 or 2, the neutral point busbar has a long main body portion extending in the circumferential direction of the stator core, and a plurality of protrusions projecting from the main body portion in a direction intersecting its longitudinal direction. Each protrusion portion has the busbar terminal portion at its tip and a root portion between the main body portion and the busbar terminal portion. In the neutral point busbar, the cross-sectional areas of the main body portion and the root portion are each larger than the cross-sectional area of the busbar terminal portion.

In a neutral point busbar, multiple protrusions extend from the main body, which extends circumferentially from the stator core. The tip of each protrusion serves as the busbar terminal, while the base is located on the main body side. Furthermore, the cross-sectional areas of the main body and base are larger than those of the busbar terminal. This configuration ensures that when welding the tip of the conductor segment and the busbar terminal, the welded area becomes highly heated. This heat is then transferred to the main body of the neutral point busbar via the base, making it easier for the heat to pass through to the conductor segment and the neutral point busbar. In other words, the heat from welding is more easily transferred to the neutral point busbar than to the conductor segment. Therefore, problems such as the insulation coating of the conductor segment melting due to heat are less likely to occur.

In method 4, a temperature sensor is integrally mounted to the neutral point busbar in method 3.

The neutral busbar becomes hot due to the heat generated when current flows through it, and this temperature is detected by a temperature sensor. However, in this case, if the heat from the neutral busbar escapes to the conductor segment side through the protrusion, there is a concern that the accuracy of temperature detection will decrease. Furthermore, while the stator winding switches the current flow for each phase, the neutral busbar remains energized regardless of which phase is energized, so it is possible that the neutral busbar will become hotter.

In this regard, as described above, in the neutral point busbar, the cross-sectional area of the main body and the base are larger than the cross-sectional area of the busbar terminal. In other words, the cross-sectional area of the busbar terminal is smaller than the cross-sectional area of the main body and the base. This suppresses the heat from the neutral point busbar from escaping to the conductor segment. Therefore, the decrease in temperature detection accuracy by the temperature sensor is suppressed.

In means 5, in means 4, the area of the cross-sectional surface of the portion of the neutral point busbar where the temperature sensor is assembled is the same as the conductor cross-sectional area of the conductor segment.

By having the same cross-sectional area of the portion of the neutral busbar where the temperature sensor is mounted as the same cross-sectional area of the conductor segment, the current density becomes the same when the conductor segment and the neutral busbar are energized. This allows for improved temperature detection accuracy in the temperature sensor integrated into the neutral busbar.

A perspective view showing part of the stator. A front view showing part of the stator. Plan view of the stator. An explanatory diagram showing the state of inserting a conductive segment into the stator core. Perspective view of the neutral point busbar. A perspective view showing a magnified view of the junction between the conductor segment and the busbar terminal. A plan view showing a magnified view of the joint between the conductor segment and the busbar terminal.

The following describes embodiments of the rotating electric machine according to the present invention with reference to the drawings. In the following embodiments and modifications, parts that are identical or equivalent to each other are denoted by the same reference numerals in the drawings, and the descriptions of these parts are provided below. The motor, as a rotating electric machine in this embodiment, can be used, for example, as an electric motor for vehicles or for aircraft.

The rotating electric machine of this embodiment is applicable to permanent magnet synchronous motors, wound field motors, and induction motors, and is a rotating electric machine having multiphase windings. The rotating electric machine comprises a cylindrical stator and a rotor arranged radially opposite the stator. The rotor is rotatably positioned around the axis of rotation. First, the schematic configuration of the stator 10 will be described using Figures 1 to 3. In the following description, "axial direction" refers to the axial direction of the stator 10, i.e., the axial direction of the rotor's axis of rotation; "radial direction" refers to the radial direction of the stator 10, i.e., the direction perpendicular to the rotor's axis of rotation; and "circumferential direction" refers to the circumferential direction of the stator 10, i.e., the circumferential direction around the rotor's axis of rotation.

The stator 10 comprises a ring-shaped stator core 11 and stator windings 12 wound around the stator core 11. The rotating electric machine of this embodiment is an inner-rotor type, with the rotor positioned radially inside the stator 10 in a rotatable manner. The stator windings 12 have U-phase windings, V-phase windings, and W-phase windings as phase windings, and these phase windings are Y-connected, forming a three-phase winding. The stator windings 12 generate magnetic flux when power (AC power) is supplied from a power source via an inverter (not shown).

The stator core 11 has an annular back yoke 21 and a plurality of teeth 22 that protrude radially inward from the back yoke 21 and are arranged at predetermined distances in the circumferential direction, with slots 23 formed between adjacent teeth 22. The slots 23 have an open shape extending radially and are provided at equal intervals in the circumferential direction on the stator core 11. The stator windings 12 are provided wound around these slots 23. The stator core 11 is constructed as a core sheet laminate, in which core sheets made of, for example, magnetic electromagnetic steel sheets are stacked axially.

The stator winding 12 is constructed using multiple conductor segments 30, which are divided conductors formed into a roughly U-shape from electrical conductors of a uniform thickness and a roughly rectangular cross-section (flat-angle cross-section). Each conductor segment 30 is connected to the others at the coil end CE. The coil end CE is the portion that is axially outward from the stator core 11 on both axial sides. The segment structure of the stator winding 12 will be described in detail below.

Figure 4 is an explanatory diagram showing the insertion of the conductor segment 30 into the slot 23 of the stator core 11. As shown in Figure 4, the conductor segment 30 is roughly U-shaped and has a pair of straight sections 31 and a bent section 32 connecting the pair of straight sections 31. The pair of straight sections 31 have a length longer than the axial thickness of the stator core 11. The conductor segment 30 is constructed using a rectangular conductor (a conductor having a pair of opposing planar sections) covered with an insulating coating. The tip of each straight section 31 is a conductor exposed section 33 where the insulating coating is removed, exposing the conductor.

Multiple conductor segments 30 are inserted into the slots 23 of the stator core 11 in a radially aligned row. This allows the linear portions 31 of the conductor segments 30 to be stacked in multiple layers within the slots 23. In the conductor segments 30, a pair of linear portions 31 are housed in two slots 23 separated by a predetermined coil pitch. An insulating sheet 24 is provided within the slots 23 to electrically insulate the stator core 11 from the stator windings 12 (conductor segments 30). The insulating sheet 24 is folded to surround the multiple conductor segments 30 inserted into the slots 23 and is positioned between the inner circumferential surface (inner wall surface) of the stator core 11 and the conductor segments 30 within the slots 23.

The pair of straight sections 31 of the conductor segment 30 are housed in the two slots 23 with their radial positions offset by one. For example, if one straight section 31 is housed at the nth position from the radial rear (back yoke side), the other straight section 31 is housed at the (n+1)th position from the radial rear.

When inserting each conductor segment 30 into the slot 23 of the stator core 11, the straight portion 31 of each conductor segment 30 is inserted from the first end side of the axial ends of the stator core 11, and the tip of the straight portion 31 protrudes from the second end side. In this case, at the first end side of the stator core 11, the coil end CE on one axial side is formed by the turned portion 32 of the conductor segment 30.

Furthermore, at the second end of the stator core 11, the opposite-turned portion of each straight section 31 is bent circumferentially, and the straight sections 31 of different conductor segments 30 are joined by welding, thereby forming the coil end CE on the other axial side (see Figure 2). At the joint of each conductor segment 30, the tips of each conductor segment 30 extend in the same direction (i.e., axially), and the tips of the conductor segments 30 overlap each other. They are joined by welding from the axial direction (direction A in Figure 1). In this case, the tips of each conductor segment 30 are joined by laser welding with their flat surfaces facing each other and overlapping.

Furthermore, in the stator winding 12, the phase windings of each phase are interconnected by a neutral point busbar 40. As shown in Figure 1, the neutral point busbar 40 is positioned radially outward of the stator winding 12 at the coil end CE and is connected by welding to the conductor segments 30 that form the winding ends of each phase winding. The configuration of the neutral point busbar 40 will be described in detail below.

As shown in Figure 5, the neutral point busbar 40 is made of a flat rectangular conductor and has a long main body portion 41 and three protrusions 42 that project from the main body portion 41 in a direction intersecting its longitudinal direction. The neutral point busbar 40 is made of a punched material cut from a flat plate. The main body portion 41 is formed to be long and extend in an arc shape in a plan view. In terms of the assembly state to the stator winding 12, the neutral point busbar 40 has a main body portion 41 that extends in the circumferential direction and protrusions 42 that extend radially inward from the main body portion 41 toward the stator winding 12 side (see Figure 1). The three protrusions 42 are parts that are joined to the winding ends of the U-phase, V-phase, and W-phase windings, respectively. In this embodiment, the radial tips of the protrusions 42 are joined to the winding ends of each phase winding at the coil end CE by laser welding.

More specifically, the projection 42 has a busbar terminal portion 42a at its tip, which is the part joined to the conductor segment 30, and a base portion 42b between the main body portion 41 and the busbar terminal portion 42a. The projection 42 is bent so that the busbar terminal portion 42a and the base portion 42b extend in directions that intersect each other. Furthermore, the busbar terminal portion 42a and the base portion 42b have different widths, with the base portion 42b being wider than the busbar terminal portion 42a. Moreover, in the neutral point busbar 40, the cross-sectional areas of the main body portion 41 and the base portion 42b are each larger than the cross-sectional area of the busbar terminal portion 42a.

Furthermore, a folded portion 43 is provided in the middle of the main body 41, formed by folding back a part of a rectangular conductor. The folded portion 43 is a sensor mounting section for attaching a temperature sensor 45 (see Figure 1) that detects the temperature of the stator 10. Specifically, the temperature sensor 45 is attached to the neutral point busbar 40 while sandwiched between the folded portion 43. Although not shown, a signal line is connected to the temperature sensor 45.

The main body 41 of the neutral point busbar 40 has a cross-sectional area equal to that of the conductor segment 30. As a result, the cross-sectional area of the portion of the main body 41 where the temperature sensor 45 is mounted is the same as that of the conductor segment 30. Therefore, when the conductor segment 30 and the neutral point busbar 40 are energized, the current density becomes the same, improving the temperature detection accuracy of the temperature sensor 45 integrated into the neutral point busbar 40.

Figures 6 and 7 show enlarged views of the joint between the tip of the conductor segment 30 and the busbar terminal 42a. Figure 7 is a plan view of the joint between the conductor segment 30 and the busbar terminal 42a, viewed from the axial direction.

In Figure 6, the tip of the conductor segment 30 and the busbar terminal portion 42a of the neutral point busbar 40 each extend axially, with the conductors overlapping. In this state, they are joined together by welding. The conductor segment 30 is joined to the busbar terminal portion 42a at the conductor exposed portion 33. During the welding of the segment tip and the busbar terminal portion 42a, laser welding is performed axially (direction A in the figure), similar to the welding of the conductor segments 30 themselves.

Furthermore, as shown in Figure 7, the conductor exposed portion 33 and the busbar terminal portion 42a of the conductor segment 30 each have a substantially rectangular cross-section, and one side of each overlaps with the other. More specifically, the busbar terminal portion 42a has a rectangular cross-section consisting of a long side and a short side, with the long side overlapping the conductor exposed portion 33 of the conductor segment 30, and the width of the long side being the same as that of the conductor exposed portion 33. Also, the width W1 of the short side of the conductor exposed portion 33 of the conductor segment 30 and the width W2 of the short side of the busbar terminal portion 42a are such that W1 > W2. Due to this configuration, at the joint between the conductor segment 30 and the busbar terminal portion 42a, the cross-sectional area of the busbar terminal portion 42a is smaller than the conductor cross-sectional area of the conductor segment 30.

The effects and benefits of the stator 10 with the above configuration are described below.

In the stator 10, at the joint between the conductor segment 30 and the busbar terminal portion 42a, the cross-sectional area of the busbar terminal portion 42a is smaller than the conductor cross-sectional area of the conductor segment 30. In this case, during welding of the segment tip and the busbar terminal portion 42a, the busbar terminal portion 42a becomes hotter than the segment tip due to the difference in cross-sectional area. This allows for a greater welding depth compared to welding the conductor segments 30 together. In other words, while maintaining the same welding conditions, such as welding energy, for welding the conductor segments 30 together and welding the segment tip and busbar terminal portion 42a, the welding depth can be increased in the welding of the segment tip and busbar terminal portion 42a.

Comparing the joining of conductor segments 30 to the joining of the segment tips and busbar terminals 42a, the way loads are applied at each joining point differs, and the latter may require greater joining strength. This requirement can be adequately met. Specifically, at the joining point of the segment tips and busbar terminals 42a, external forces such as the weight of the neutral point busbar 40 itself and contact with other components may act, making it desirable to increase the load-bearing capacity compared to the joining point of the conductor segments 30. As described above, increasing the welding depth makes it possible to increase the joining strength. As a result, the neutral point busbar 40 can be properly joined to the conductor segments 30.

The longer side of the cross-section of the busbar terminal portion 42a is overlapped with the segment tip, and the widths of the longer side of the busbar terminal portion 42a and the segment tip are made equal. This allows the overlapping of the joint portion to be performed in the same way as the welding of the conductor segments 30, even though the areas of the cross-sections of the segment tip and the busbar terminal portion 42a are different. Therefore, welding work can be performed more efficiently.

In the neutral point busbar 40, the cross-sectional areas of the main body portion 41 and the base portion 42b are each larger than the cross-sectional area of the busbar terminal portion 42a. This configuration allows the welded portion to become very hot during welding of the segment tip and the busbar terminal portion 42a. When this heat is transferred to the conductor segment 30 and the neutral point busbar 40, it is more easily transferred to the main body portion 41 of the neutral point busbar 40 via the base portion 42b. In other words, the heat from welding is more easily transferred to the neutral point busbar 40 side than to the conductor segment 30 side. Therefore, the temperature rise on the conductor segment 30 side is suppressed, and problems such as the insulating coating of the conductor segment 30 melting due to heat are less likely to occur.

Furthermore, the neutral busbar 40 becomes hot due to the heat generated when current flows through it, and this temperature is detected by the temperature sensor 45. However, in this case, if the heat from the neutral busbar 40 escapes to the conductor segment 30 side through the protrusion 42, there is a concern that the temperature detection accuracy will decrease. While the stator winding 12 switches the energization for each phase, the neutral busbar 40 remains energized regardless of which phase is energized, so it is conceivable that the neutral busbar 40 will become hotter. In this regard, as described above, the cross-sectional area of the main body 41 and the base 42b of the neutral busbar 40 is larger than the cross-sectional area of the busbar terminal 42a. In other words, the cross-sectional area of the busbar terminal 42a is smaller than the cross-sectional area of the main body 41 and the base 42b. This suppresses the escape of heat from the neutral busbar 40 to the conductor segment 30 side. Therefore, the decrease in the temperature detection accuracy by the temperature sensor 45 is suppressed.

(Other embodiments)
The above embodiment may be modified as follows, for example.

In the above embodiment, the cross-sections of the tip of the conductor segment 30 and the busbar terminal portion 42a were both approximately rectangular, and their sides overlapped. However, this configuration may be changed. For example, the cross-section of the busbar terminal portion 42a may be made into a shape other than approximately rectangular, such as approximately triangular or approximately semicircular, and the planar portions of the tip of the conductor segment 30 and the busbar terminal portion 42a may be overlapped. In any case, at the joint between the tip of the conductor segment 30 and the busbar terminal portion 42a, it is sufficient that the area of the cross-sectional surface of the busbar terminal portion 42a is smaller than the conductor cross-sectional area of the conductor segment 30.

The main body 41 of the neutral busbar 40 and the conductor segment 30 may have different conductor cross-sectional areas. In this case, it is possible to have a configuration where the main body 41 of the neutral busbar 40 has a larger conductor cross-sectional area than the conductor segment 30, or a configuration where the main body 41 of the neutral busbar 40 has a smaller conductor cross-sectional area than the conductor segment 30.

• In the above embodiment, an example of application in an inner rotor type rotating electric machine was described, but it is also possible to apply it to an outer rotor type rotating electric machine.

10…Stator, 11…Stator core, 12…Stator winding, 30…Conductor segment, 40…Neutral busbar, 42a…Busbar terminal, CE…Coil end.

Claims (7)

A stator (10) comprising a stator core (11), a stator winding (12) provided on the stator core and having a plurality of phase windings, and a neutral point busbar (40) provided at the coil end (CE) of the stator winding, connected to the phase windings of each phase,
The stator winding is constructed using a plurality of conductor segments (30), and each of these conductor segments is connected to the other.
At the coil end, the tips of the conductor segments are joined by welding in an overlapping state, while the tip of the conductor segment connected to the neutral point of the stator winding and the busbar terminal portion (42a) of the neutral point busbar are joined by welding in an overlapping state.
The tip of the conductor segment and the busbar terminal each have a substantially rectangular cross-section, and one side of the tip of the conductor segment and the busbar terminal overlap each other.
The cross-section of the busbar terminal portion has a long side and a short side, and of the long side and short side, the long side overlaps the tip of the conductor segment .
A stator in which, at the joint between the tip of the conductor segment and the busbar terminal, the cross-sectional area of the busbar terminal is smaller than the conductor cross-sectional area of the conductor segment. The stator according to claim 1 , wherein the width W1 of the short side of the tip of the conductor segment and the width W2 of the short side of the busbar terminal portion are in the relationship W1 > W2. A stator (10) comprising a stator core (11), a stator winding (12) provided on the stator core and having a plurality of phase windings, and a neutral point busbar (40) provided at the coil end (CE) of the stator winding, connected to the phase windings of each phase,
The stator winding is constructed using a plurality of conductor segments (30), and each of these conductor segments is connected to the other.
At the coil end, the tips of the conductor segments are joined by welding in an overlapping state, while the tip of the conductor segment connected to the neutral point of the stator winding and the busbar terminal portion (42a) of the neutral point busbar are joined by welding in an overlapping state.
The neutral point busbar has an elongated main body portion (41) extending in the circumferential direction of the stator core, and a plurality of protrusions (42) projecting from the main body portion in a direction intersecting its longitudinal direction.
The aforementioned protruding portion has the busbar terminal portion at its tip and a base portion (42b) between the main body portion and the busbar terminal portion.
At the joint between the tip of the conductor segment and the busbar terminal, the area of the cross-section of the busbar terminal is smaller than the conductor cross-sectional area of the conductor segment.
A stator in the neutral point busbar, wherein the cross-sectional area of the main body portion and the base portion are each larger than the cross-sectional area of the busbar terminal portion . The stator according to claim 3, wherein in the cross-section of the busbar terminal portion, in the direction in which the joint surface with the tip of the conductor segment extends, on one side the respective sides of the busbar terminal portion and the base portion are continuous, and on the other side the respective sides of the busbar terminal portion and the base portion are discontinuous in a stepped manner, so that the area of the cross-section of the base portion is larger than the area of the cross-section of the busbar terminal portion. The tip of the conductor segment and the busbar terminal each have a substantially rectangular cross-section, and one side of the tip of the conductor segment and the busbar terminal overlap each other.
The stator according to claim 3 or 4 , wherein the busbar terminal portion has a rectangular cross-section consisting of a long side and a short side, and the long side of the long side overlaps the tip of the conductor segment. The stator according to claim 3 or 4 , wherein a temperature sensor (45) is integrally mounted to the neutral point busbar. The stator according to claim 6 , wherein the area of the cross-section of the portion of the neutral point busbar to which the temperature sensor is assembled is the same as the conductor cross-sectional area of the conductor segment.