JP6711460B2 - Stator manufacturing apparatus, stator manufacturing method, and stator - Google Patents

Description

The present invention relates to a stator manufacturing device, a stator manufacturing method, and a stator.

In an electric motor driven in three phases, coils corresponding to each of the three phases are provided in a stator core that constitutes a part of the motor. In such a motor, interphase insulating paper may be provided so that the coils of three phases are insulated from each other at the end surface of the stator core.

In general, the interphase insulating paper has two rectangular insulating parts and two strip-shaped legs connecting the ends of the insulating parts by forming a rectangular hole near the center of the rectangular paper. It is composed by. In the interphase insulating paper, when the legs are arranged in the slots, the two insulating portions are located on the end surface of the stator core and insulate the coils of each phase from each other.

For example, JP 61-185046A discloses a device for inserting interphase insulating paper into a stator core. According to this apparatus, when the interphase insulating paper is set on the outer peripheral surface of the shell-shaped holder, the holder is inserted into the inner diameter of the stator core. The holder is provided with a pushing mechanism that pushes the interphase insulating paper radially outward of the stator core, and pushes the interphase insulating paper radially outward by the pushing mechanism to the slot. By doing so, the leg portions of the interphase insulating paper are inserted into the slots, and the insulating portion is provided on the end surface of the stator core, so that the coils of each phase can be insulated from each other.

According to JPS61-185046A, when the leg portion is moved radially outward of the stator by the pushing mechanism and is inserted into the slot, the leg portion may collide with the tooth. In such a case, since the interphase insulating paper is not correctly inserted into the slot, it is necessary to insert the interphase insulating paper again, and there is a problem that the productivity of the stator is reduced.

The present invention has been invented to solve such a problem, and an object thereof is to improve the productivity of the stator.

According to an aspect of the present invention, there is provided a stator manufacturing apparatus including an inserting device for inserting interphase insulating paper into a slot of a stator core, wherein the interphase insulating paper includes two insulating parts and opposite sides of the insulating parts. And two strip-shaped legs that connect both ends of the. The insertion device includes a main body that is movable along the axial direction of the stator core, a U-shaped curve that extends in the axial direction and opens radially outward, and a radial outside of the curved surface. And a holder for supporting the interphase insulating paper. The radially outer end of the holder is located in the slot on the projection plane in the axial direction.

Embodiments of the present invention and advantages of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a plan view of the interphase insulating paper of the first embodiment. FIG. 2A is a top view of the stator core at the insertion stage. 2B is a cross-sectional view taken along the line AA′ of FIG. 2A. FIG. 3 is a perspective view of the insertion device. FIG. 4A is a diagram showing a setting step. FIG. 4B is a diagram showing an axial insertion step. FIG. 4C is a diagram showing an axial insertion step. FIG. 4D is a diagram showing an axial insertion step. FIG. 4E is a diagram showing a pressing portion extracting process. FIG. 4F is a diagram showing a radial insertion step. FIG. 4G is a diagram showing an inserting device removing step. FIG. 4H is a diagram showing a folding step. FIG. 5A is a perspective view of the insertion device and the interphase insulating paper of the second embodiment. FIG. 5B is a perspective view of the insertion device and the interphase insulating paper. FIG. 6 is a perspective view of the slot insulating paper of the third embodiment. FIG. 7 is a top view of the stator core and the slot insulating paper of the fourth embodiment.

The insertion device according to the first embodiment of the present invention will be described.

FIG. 1 is a plan view of an interphase insulating paper inserted by an inserting device.

According to this figure, the interphase insulating paper 10 is formed by providing a rectangular opening in a rectangular paper, and comprises two rectangular insulating parts 11 and 12 and strip-shaped leg parts 13 and 14. It is configured. Both ends of the opposite sides of the two insulating portions 11 and 12 are connected to each other by the leg portions 13 and 14. The interphase insulating paper 10 will be described below as an insulating paper, but the insulating paper is not limited to paper and may be resinous if it is insulating.

2A and 2B are explanatory diagrams of a situation where the interphase insulating paper 10 is inserted into the stator core 20. The stator core 20 constitutes a part of an electric motor, and the electric motor can also operate as a generator.

FIG. 2A is a top view of the stator core 20 at the stage of inserting the interphase insulating paper 10 into the stator core 20. In the following description, the axial direction, the radial direction, and the circumferential direction of the stator core 20 will be simply referred to as the axial direction, the radial direction, and the circumferential direction, respectively.

The stator core 20 is a hollow tubular member, and the stator core 20 is provided with a plurality of slots 21 that open to the inner diameter side, and spaces between the adjacent slots 21 are referred to as teeth 23. That is, the stator core 20 is configured by arranging the teeth 23 extending inward in the radial direction side by side in the circumferential direction. The coil 22 is wound around the tooth 23 while being inserted so as to straddle the two slots 21.

The interphase insulating paper 10 is set in the holder 32 of the insertion device 30. In addition, in this figure, for the sake of explanation, only the holder 32 of the insertion device 30 is shown. The holder 32 is a substantially U-shaped member that is curved so as to open to the outside in the radial direction, and a part of the tip in the radial direction is inserted into the slot 21. By doing so, the leg portions 13 and 14 of the interphase insulating paper 10 set on the holder 32 are inserted into the slots 21.

The tip of the holder 32 is rounded in the circumferential direction. By doing so, even if the legs 13 and 14 come into contact with the holder 32, damage to the legs 13 and 14 can be suppressed.

2B is a cross-sectional view taken along the line A-A′ of FIG. 2A. Note that the holder 32 of the insertion device 30 is omitted in this figure for readability.

When the holder 32 (not shown) is moved in the axial direction (downward direction in the drawing, arrow direction), the interphase insulating paper 10 is moved with the legs 14 inserted in the slots 21. Then, when the entire leg portion 14 is inserted into the slot 21, the insertion device 30 ends the axial movement.

Here, details of the insertion device 30 for inserting the interphase insulating paper 10 into the slot 21 will be described.

FIG. 3 is a perspective view of the insertion device 30.

The insertion device 30 is provided on the inner surface of the stator core 20 in the projection plane in the axial direction, and includes a main body 31, a holder 32, a holding portion 33, and a rail 34. The holder 32 is attached to the outside of the main body 31 in the radial direction. The main body 31 and the pressing portion 33 are configured to be independently movable in the axial direction along a rail 34 extending in the axial direction.

As described above, the main body 31 is configured to be movable in the axial direction along the rail 34, and the holder 32 is attached to the main body 31 on the radially outer side.

The main body 31 is configured by arranging a main body upper portion 31A, a main body intermediate portion 31B, and a main body lower portion 31C along a rail 34. The main body upper portion 31A and the main body lower portion 31C are provided so as to project radially outward from the main body intermediate portion 31B, and are configured to be movable in the radial direction.

The holder 32 is a U-shaped member that curves so as to open outward in the radial direction, and is configured by arranging a holder upper portion 32A, a holder intermediate portion 32B, and a holder lower portion 32C in the axial direction. The holder upper portion 32A is connected to the main body upper portion 31A, and the holder lower portion 32C is connected to the main body lower portion 31C. Further, the radially outer end portion of the holder intermediate portion 32B projects radially outward with respect to the holder upper portion 32A and the holder lower portion 32C.

When the main body upper portion 31A and the main body lower portion 31C are moved radially outward, the holder upper portion 32A and the holder lower portion 32C are pushed outward in the radial direction. Since the holder middle portion 32B is not connected to the holder upper portion 32A and the holder lower portion 32C but is connected to the main body middle portion 31B via a bridge (not shown), the holder middle portion 32B does not move.

The holding portion 33 includes a holding body portion 33A connected to the rail 34 and a holding plate 33B. The pressing body portion 33A is composed of two rectangular parallelepipeds having the same width in the circumferential direction and different lengths in the radial direction, and a step portion 33C is provided in the radial direction. The end portion of the pressing plate 33B is connected to the step portion 33C. The pressing plate 33B is curved, and the inner diameter surface of the projection surface in the axial direction substantially faces the outer diameter surface of the holder 32.

Next, a method of inserting the interphase insulating paper 10 into the stator core 20 will be described with reference to FIGS. 4A to 4E. A coil is inserted into a part of the slot 21 of the stator core 20, and the step of inserting the legs 13 and 14 of the interphase insulating paper 10 into the slot 21 into which the coil is inserted will be described. In the following, description of the coil is omitted for the sake of readability of the drawings. Unless otherwise specified, the directions in the following description shall mean the directions in the drawings (up, down, left and right).

FIG. 4A is a diagram showing a step of setting the interphase insulating paper 10.

As described above, on the projection plane in the axial direction, the one surface in the radial direction of the pressing plate 33B is provided slightly outside the surface in the radial direction outside of the holder 32. When the interphase insulating paper 10 is attached to the radially outer surface of the holder 32 and the pressing portion 33 is moved along the axial direction onto the holder 32, the interphase insulating paper 10 is fixed by the pressing plate 33B. The top view of the stator core 20 in this state shows that the tip of the holder 32 is provided in the slot 21 on the projection plane in the axial direction, as shown in FIG. 2A.

FIG. 4B is a diagram showing an axial insertion step in which the interphase insulating paper 10 is axially inserted into the slot 21 after the setting step. In this figure, a part of the vicinity of the end surface of the stator core 20 is shown enlarged.

In this figure, the main body 31 and the pressing portion 33 are moved integrally along the rail 34 in the axial direction so as to approach the stator core 20. In this way, the lower end of the interphase insulating paper 10 fixed on the holder 32 is inserted into the opening at the upper end of the slot 21.

FIG. 4C is a diagram showing an axial insertion step in a state where the insertion device 30 is further moved in the axial direction and inserted into the stator core 20 as compared with FIG. 4B. In this figure, a part of the vicinity of the end surface of the stator core 20 is shown enlarged.

In this figure, the main body 31 and the pressing portion 33 are further integrated and inserted further downward into the inner diameter of the stator core 20. By doing so, the ends of the legs 13, 14 of the interphase insulating paper 10 are further inserted into the slots 21.

FIG. 4D is a diagram showing an axial insertion step in which the interphase insulating paper 10 is completely inserted into the slot 21 by further lowering the insertion device 30 compared to FIG. 4C. According to this drawing, the interphase insulating paper 10 is attached to the holder 32, and the leg portions 13 and 14 (not shown) are inserted into the slots 21. In this state, the insulating part 11 is located axially above the slot 21, and the insulating part 12 is located axially below the slot 21.

FIG. 4E is a diagram showing a pressing part extracting step of extracting the pressing part 33 upward from the inner diameter of the stator core 20. As shown in this figure, when only the pressing portion 33 is moved axially away from the stator core 20 with the main body 31 fixed, the pressing portion 33 is pulled out from the stator core 20.

FIG. 4F is a diagram showing a radial insertion step of inserting the interphase insulating paper 10 into the slot 21 in the radial direction.

When the main body upper part 31A and the main body lower part 31C are moved radially outward, the holder upper part 32A and the holder lower part 32C are moved radially outward. By doing so, the insulating portions 11 and 12 are moved radially outward, and the legs 13 and 14 are further inserted radially outward in the slots 21.

FIG. 4G is a diagram showing an insertion device removing step of removing the insertion device 30.

When the interphase insulating paper 10 is inserted into the slot 21, the main body upper portion 31A and the main body lower portion 31C are moved to the initial positions on the radially inner side, and the main body 31 and the pressing portion 33 are axially moved along the rail 34. And is moved upward from the stator core 20 and away from the stator core 20. In this way, the insertion device 30 is taken out from the stator core 20, and the insertion of the interphase insulating paper 10 into the slot 21 is completed.

After the step of FIG. 4G, the step of folding back the interphase insulating paper 10 to the outside in the radial direction may be performed by moving the insulating parts 11 and 12 to the outside in the circumferential direction. FIG. 4H is a top view of the slot 21 after the folding step.

According to this figure, the central portions in the circumferential direction of the insulating portions 11 and 12 are bent outward in the radial direction and are curved so as to open inward in the radial direction. In this state, the legs 13 and 14 rotate in the slot 21, and by doing so, the end face of the stator core 20 is covered with the coil 22 and insulation between phases is maintained.

Note that this folding step may be performed after the step of FIG. 4F. In that case, the main body upper portion 31A and the main body lower portion 31C of the insertion device 30 further move radially outward, and the insulating portions 11 and 12 are folded back radially outward.

According to the first embodiment, the following effects can be obtained.

According to the stator manufacturing apparatus of the first embodiment, the holder 32 is configured in a U-shape that extends in the axial direction and opens outward in the radial direction, and the curved surface has an interphase on the radially outer surface. The insulating paper 10 is held. The outer end of the holder 32 in the radial direction is arranged so as to be located in the slot 21 on the projection plane in the axial direction, and the holder 32 is configured to be movable in the slot 21 in the axial direction.

Here, when the holder 32 moves in the axial direction and reaches the inner diameter side of the stator core 20 in a state where the interphase insulating paper 10 is fixed on the radially outer surface, the radially outer end portion of the holder 32, and The leg portions 13 and 14 of the interphase insulating paper 10 held by the holder 32 are inserted into the slots 21 without colliding with the teeth 23. By doing so, the leg portions 13 and 14 can be inserted into the slot 21 more reliably than in the conventional method, so that the re-insertion of the interphase insulating paper 10 is reduced and the productivity of the stator is improved. You can

According to the stator manufacturing apparatus of the first embodiment, the holder 32 is configured to be movable in the radial direction. When the holder 32 further moves radially outward after the interphase insulating paper 10 is inserted into the slot 21 of the stator core 20, the entire interphase insulating paper 10 is folded back radially outward and opens inward radially. Become. That is, the central portions of the insulating portions 11 and 12 in the circumferential direction are bent outward in the radial direction and are curved inward in the radial direction (FIG. 4G). By doing so, the coil 22 is covered with the insulating portions 11 and 12 on the end surface of the stator core 20, so that insulation between phases can be maintained. By performing such a folding-back process using the insertion device 30, another device for folding-back is not required, so that the productivity of the stator can be improved.

According to the stator manufacturing apparatus of the first embodiment, in the holder 32, the interphase insulating paper 10 is fixed such that the curved outer end in the radial direction is located outside the interphase insulating paper 10. With such a configuration, the interphase insulating paper 10, in particular, the legs 13 and 14 are inserted into the slots 21 while being covered by the holder 32, so that the interphase insulating paper 10 collides with the teeth 23. The risk of damage can be reduced.

According to the stator manufacturing apparatus of the first embodiment, the tip of the holder 32 is rounded. By doing so, it is possible to reduce the possibility that the interphase insulating paper 10 collides with the tip of the holder 32 and damages the interphase insulating paper 10.

According to the stator manufacturing apparatus of the first embodiment, the insertion device 30 further includes the pressing portion 33 that presses the interphase insulating paper 10 fixed to the holder 32 from the outside in the radial direction. Since the interphase insulating paper 10 is fixed on the holder 32 by having such a holding portion 33, the interphase insulating paper 10 can be prevented from falling when the holder 32 moves. Therefore, the re-insertion of the interphase insulating paper 10 is reduced, and the productivity of the motor can be improved.

(Second embodiment)
In the first embodiment, the example in which the interphase insulating paper 10 is directly inserted into the slot 21 from the end surface of the stator core 20 in the axial direction has been described. In the second embodiment, an example will be described in which a guide is provided on the end surface of the stator core 20 and the interphase insulating paper 10 is axially inserted into the slot 21 via the guide.

FIG. 5A is a perspective view of the interphase insulating paper 10 as viewed from the outside in the radial direction in a state in which the insertion device 30 is axially lowered toward the stator core 20. Note that, in this figure, the holding portion 33 is omitted for the sake of explanation.

FIG. 5B is a perspective view of the interphase insulating paper 10 as viewed from the radially inner side in the same state as FIG. 5A.

An insertion jig 40 is provided on the end surface of the stator core 20 on the side where the interphase insulating paper 10 is inserted. The insertion jig 40 includes guides 41 and 42, a bridge 43 that connects the guide 41 and the guide 42, and a bar 44 that is connected to the bridge 43.

The guides 41 and 42 are provided on the end surface of the stator core 20 and have openings through which the interphase insulating paper 10 can pass in the axial direction. The inner wall surfaces of the guides 41 and 42 are continuous with the inner surface of the slot 21 at the end surface of the slot 21, and widen in the direction away from the stator core 20. That is, the inner surfaces of the guides 41 and 42 are tapered in the direction toward the stator core 20, and the opening width becomes narrower toward the lower part.

The guide 41 and the guide 42 are connected by a bridge 43 extending in the circumferential direction. A bar 44 extending outward in the radial direction is connected to an intermediate portion of the bridge 43 in the circumferential direction.

The interphase insulating paper 10 is guided to the upper end opening of the slot 21 through the guides 41 and 42. When inserting the interphase insulating paper 10 into the slot 21, it is first inserted into the guides 41 and 42. Here, of the two axial openings of the guides 41 and 42, the width of the opening on the side where the interphase insulating paper 10 is inserted is wider than the width of the slot 21. Therefore, the interphase insulating paper 10 is first inserted into the opening on the upper end side of the guides 41, 42 wider than the slot 21, so that the interphase insulating paper 10 collides with the teeth 23 and the guides 41, 42. Is suppressed.

According to the second embodiment, the following effects can be obtained.

According to the stator manufacturing apparatus of the second embodiment, the guides 41, 42 provided on the end surface of the stator core 20 are configured so that the inner surface is continuous with the slot 21 and the radial opening becomes wider as the distance from the end surface increases. Is further provided. With such a guide, the slot insulating paper 50 is inserted into the slots 21 after being inserted into the guides 41 and 42 wider than the slot 21, and then guided by the guides 41 and 42.

Therefore, when the interphase insulating paper 10 is inserted into the slot 21, the collision with the teeth 23 is suppressed, so that the reinsertion of the interphase insulating paper 10 is reduced and the productivity of the motor can be improved. it can.

(Modification of the second embodiment)
In the above embodiment, the example in which the guides 41 and 42 are provided on the end surface of the stator core 20 has been described. Hereinafter, a modified example in which the slot insulating paper 50 is provided in the slot 21 and the slot insulating paper has the same function as the guides 41 and 42 will be described.

In general, slot insulation paper 50 is provided in the slot 21 to insulate the slot 21 from the coil 22. Therefore, the interphase insulating paper 10 is inserted into the slot 21 with the slot insulating paper 50 inserted therein.

FIG. 6 is a perspective view of the slot insulating paper of the present embodiment. Although the slot insulating paper is bent and arranged in the slot 21, the description of the slot 21 is omitted for the sake of explanation.

A rectangular main body 51 of the slot insulating paper 50 is inserted into the slot 21 so as to be bent, and its upper end is provided outside the slot 21. A part of the slot insulating paper 50 is exposed to the outside in the axial direction from the slot 21, and a fold line 50A is provided in the radial direction at the exposed portion. Here, the portion of the slot insulating paper 50 that is inserted into the slot 21 below the folding line 50A is referred to as a main body portion 51.

Extension portions 52 and 53 are provided at two end portions on the radially inner side of the main body portion 51 so as to be inclined along the axial direction by being folded at a folding line 50A. In addition, a folded-back portion 54 formed by folding back along a folding line 50A is provided at a position continuous with the extension portion 52 on the outer side in the radial direction. The folding portion 54 is folded 180 degrees along the folding line 50</b>A, and is provided along the main body portion 51. A folded-back portion (not shown) is also provided so as to be continuous with the extension portion 53 on the outer side in the radial direction.

The extension parts 52 and 53 are provided so as to open in a direction away from the main body part 51 in the axial direction, that is, to be separated from each other in the axial direction from a connection part with the main body part 51 as a starting point. With such a configuration, when the interphase insulating paper 10 is inserted into the slot 21, the extension portions 52 and 53 serve as guides, so that the interphase insulating paper 10 is inserted into the slot 21 without colliding with the slot 21. be able to.

According to the modified example of the second embodiment, the following effects can be obtained.

According to the slot insulating paper 50 of the modified example of the second embodiment, in the state where the slot insulating paper 50 is inserted into the slot 21, the radial openings become wider as the extension portions 52 and 53 move away from the end surface of the stator core 20. Is configured to be. The interphase insulating paper 10 is inserted into the slot 21 by using the extension portions 52 and 53 configured to have a narrow width downward in the axial direction.

Therefore, when the interphase insulating paper 10 is inserted into the slot 21, the collision with the teeth 23 is suppressed, so that the reinsertion of the interphase insulating paper 10 is reduced and the productivity of the motor can be improved. it can.

(Third Embodiment)
In the first and second embodiments, the example in which the openings of the slots 21 of the stator core 20 have a substantially equal width in the radial direction has been described. In the present embodiment, an example will be described in which the teeth 23 are provided with the protrusions 23A and the width of the radial opening is narrowed in a part of the slot 21.

FIG. 7 is a top view of the stator core 20 when the interphase insulating paper 10 is inserted in the present embodiment.

According to this drawing, in the tooth 23, a projection portion 23A that projects in the circumferential direction is provided at the end portion on the radially inner side. Therefore, in the slot 21, the width of the opening is narrowed radially inward. The radial opening width d of the slot 21 is configured to be smaller than the width of the leg portions 13 and 14 of the interphase insulating paper 10.

As described above, since the radial opening width d of the slot 21 is narrower than the width of the leg portions 13 and 14, the leg portions 13 and 14 are less likely to protrude from the slot 21, and defective insertion of the interphase insulating paper 10 is reduced. be able to.

According to the third embodiment, the following effects can be obtained.

According to the method of manufacturing the stator of the third embodiment, the width of the leg portions 13 and 14 is wider than the width of the opening of the slot 21 on the radially inner side. Here, the interphase insulating paper 10 is made parallel to the side surface of the slot 21 by the bending step, and then inserted into the slot 21 from the end surface of the stator core 20 in the axial direction by the inserting step. Therefore, when the interphase insulating paper 10 is inserted into the slot 21, the interphase insulating paper 10 is parallel to the side surface of the slot 21, so that the legs 13 and 14 are inserted into the slot 21 without colliding with the teeth 24. Will be.

Further, after the interphase insulating paper 10 is inserted into the slot 21, the width of the legs 13 and 14 is narrower than the width of the opening of the slot 21, so that the legs 13 and 14 are prevented from jumping out of the slot 21. .

Although the embodiment of the present invention has been described above, the above embodiment merely shows a part of the application example of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. Absent. Further, the above embodiments can be combined as appropriate.

Claims (8)

A stator manufacturing apparatus comprising an inserting device for inserting interphase insulating paper into a slot of a stator core,
The interphase insulating paper includes two insulating parts and two strip-shaped leg parts that connect opposite ends of each of the insulating parts.
The insertion device is
A main body configured to be movable along the axial direction of the stator core,
A holder that extends in the axial direction and is curved in a U-shape that opens radially outward and that supports the interphase insulating paper radially outside the curved surface,
The stator manufacturing device, wherein the radially outer end portion of the holder is located in the slot on the projection plane in the axial direction. The manufacturing apparatus of the stator according to claim 1,
The stator manufacturing apparatus, wherein the holder is configured to be movable in a radial direction. The apparatus for manufacturing a stator according to claim 1 or 2, wherein
The said holder supports the said interphase insulating paper in the said curved surface, The manufacturing apparatus of a stator. The stator manufacturing apparatus according to any one of claims 1 to 3,
The stator manufacturing apparatus, wherein a radial tip portion of the holder is rounded. The manufacturing device for a stator according to any one of claims 1 to 4,
The insertion device is
The interphase insulating paper supported by the holder is further provided with a pressing portion that presses from the outside in the radial direction,
The manufacturing device for a stator, wherein the pressing portion is configured to be movable in the axial direction independently of the main body. The manufacturing apparatus for a stator according to any one of claims 1 to 5,
The insertion device is
Manufacture of a stator, further comprising: a guide provided on an axial end surface of the stator core, the guide being configured such that the slot and the inner surface are continuous with each other, and a radial opening width increases as the axial distance from the end surface increases. apparatus. A method of manufacturing a stator by inserting an interphase insulating paper supported by a holder into a slot of a stator core,
The interphase insulating paper includes two insulating parts, and two strip-shaped leg parts connecting both ends of opposite sides of the insulating parts,
The holder is configured to be curved in a U shape that extends in the axial direction and opens outward in the radial direction, is configured to be able to support the interphase insulating paper on the radial outside of the curved surface, and It is configured to be movable in the axial direction of the stator core,
The manufacturing method,
The interphase insulating paper is curved in the holder, and is held at the radially outer end so that the leg portion is located in the slot on the projection plane in the axial direction,
A manufacturing method in which the holder is moved in the axial direction and inserted into the stator core. A method of manufacturing a stator according to claim 7,
The method of manufacturing a stator, wherein the width of the leg portion is set to be wider than the width of the opening on the radially inner side of the slot.

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