Device for aligning the end of an electrical conductor rod and method of manufacturing an electrical machine stator

Abstract

The invention relates to a device for aligning end portions of electric conductor rods to be welded to each other, comprising a holder for holding the conductor rods in a predetermined position, wherein two end portions forming a welding pair are arranged adjacent to each other, each end portion comprising a contour having a contour width and a contour height perpendicular thereto, such that joint faces extending perpendicular to the contour height are aligned opposite to each other, and a clamp having two clamping jaws defining a clamping space, the two clamping jaws being movable relative to each other in a direction reducing the clamping space, the clamp being positionable such that the welding pair axially passes through the clamping space, each clamping jaw having two jaw walls, a first jaw wall and a second jaw wall, arranged at a right angle to each other, the second jaw wall being longer than the contour height, the clamp being positionable such that its first jaw wall is aligned parallel to the joint faces, the clamping jaws being movable relative to each other in a diagonal direction connecting the angle vertices of their jaw angles.

Description

Technical Field

[0001] This invention relates to a device for aligning the ends of electrical conductor rods to be welded together, comprising:

[0002] - A retainer for holding a conductor rod in a predetermined position, wherein two ends forming a weld pair are arranged adjacent to each other, each end having a profile (typically but not necessarily approximately rectangular) with a profile width and a profile height perpendicular to it, such that mating surfaces extending perpendicular to the profile height face each other, and

[0003] - A clamp having two clamping jaws that define a clamping space and can move relative to each other in a direction that reduces the clamping space, wherein the clamp can be positioned such that the welding pair is arranged axially through the clamping space.

[0004] The present invention also relates to a method for manufacturing an electric motor stator using such an apparatus. Background Technology

[0005] Such apparatus and method are known from CN 117506292A.

[0006] As is well known, the stator of an electric motor, particularly the stator of a traction motor for an electrified motor vehicle, is essentially composed of a so-called lamination assembly through which electrical windings pass. The lamination assembly is typically a cluster of closely stacked disc-shaped electrical boards. These laminations have through-holes that collectively form channels extending axially through the lamination assembly. Conductor rods are located within these channels, projecting axially over the lamination assembly on both sides and connected to each other in different pairs on each side of the lamination assembly. It is known to manufacture such stators using conductor rods referred to as "hairpins." A hairpin consists of two parallel extending rod regions connected to each other on one side by a deflection region of a complex shape, and its overall shape is reminiscent of the named hairpin. This hairpin is inserted individually or in a pre-assembled set into the aforementioned channels of the laminated assembly and held therein. Devices for this purpose are known from DE 10 201 9114 221 A1 and DE 10 202 1 133 843 A1. The deflection regions are typically located on the axial side of the lamination assembly, often referred to as the bending side. The free ends protrude from the other axial side of the lamination core, often referred to as the twisted side or weld side. They undergo a forming process (twisting), designed to ensure that the ends to be joined are abutted against each other through their respective mating surfaces, allowing them to be joined in a subsequent joining process (welding). However, due to the inherent elasticity of the conductor rods, it is nearly impossible, solely through the forming process, to precisely position the ends to be welded together (here referred to as weld pairs) and ensure their mating surfaces are tightly abutted against each other, thus enabling reliable and reproducible welding. However, inaccuracies during the welding process can lead to differences in local conductivity between different weld pairs, which can result in locally different temperature developments and reduced operational efficiency with respect to the high currents flowing through the electric traction machine during operation.

[0007] As known from the aforementioned general standard CN 117506292A, prior to the welding process, the ends of the weld pair to be welded together are pressed together by their mating surfaces. For this purpose, clamping jaws extending parallel to the mating surfaces are provided, which move perpendicular to the mating surfaces toward each other, thereby pressing the ends to be welded together toward each other. A disadvantage of this method is that any lateral offset of the mating surfaces is not compensated for. Therefore, during twisting, the ends can be offset in their profile width direction. This lateral offset persists even during clamping along the profile height direction, where the mating surfaces are pressed together. Accordingly, the effective or usable mating surfaces may differ from weld pair, leading to the aforementioned unfavorable differences in local conductivity. Summary of the Invention

[0008] The object of this invention is to provide a device that can connect weld pairs more accurately and reproducibly.

[0009] This objective is achieved by combining the features of the preamble of claim 1 in the following manner:

[0010] - Each clamping jaw has two jaw walls arranged at right angles to each other, namely a first jaw wall and a second jaw wall, wherein the second jaw wall is longer than the profile height.

[0011] - The clamp can be positioned such that its first claw wall is parallel to and aligned with the mating surface, and

[0012] - The clamping claws are able to move relative to each other in a diagonal direction at the vertices of the claw corners that connect them.

[0013] The method of manufacturing an electric motor stator using this device is the subject of claim 10.

[0014] The preferred embodiments of the present invention are the subject of the dependent patent claims.

[0015] The basic idea of ​​this invention is to introduce contact pressure by which the two ends of a pair of welds are pressed together obliquely relative to their mating surfaces. This oblique contact pressure can be vectorarily divided into a force component along the profile height direction and a force component along the profile width direction. These two components are effectively introduced into each end of the weld pair because the clamping jaws of the fixture according to the invention have two correspondingly oriented jaw walls, i.e., perpendicular to each other and parallel to the axial direction. Thus, each clamping jaw abuts against the rear side of the corresponding end facing away from the mating surface by its first jaw wall. At least in the later stage of the pressing process, its second jaw wall abuts against a side of the conductor rod end, which faces the latter and is oriented perpendicular to the mating surface. In this way, by the obliqueness of the clamping jaws relative to each other, especially diagonally, any possible lateral offset of the conductor rod ends can be reduced to zero, such that in the final state of the pressing process, the two ends to be welded together are abutting each other across the entire surface through their mating surfaces. This result is obtained independently of the magnitude of any possible initial lateral offset. Therefore, the final connection, especially the welding process, can be performed in a precisely reproducible manner under always the same initial conditions. The above explanation is particularly easy to understand when attempting to comprehend it at the end of a trapezoidal rod with a rectangular profile. However, the invention is also applicable to other profile shapes, such as semi-circular profiles.

[0016] The basic idea of ​​the invention can be implemented in particular in two different variations, which are referred to herein as the “open” variation and the “closed” variation.

[0017] In the open variant, each clamping jaw defines a portion of the clamping space that is open to the corresponding other clamping jaw. In other words, the clamping jaws have an open angular shape and consist essentially only of their first and second jaw walls. In this embodiment, the clamping jaws can be arranged at their own level relative to the axial direction of the weld pair. Thus, the clamping jaws feed each other in the same feed plane. The advantage of this variant is that the axial structural space defined downward by the minimum thickness of the clamping jaws, specified for stability reasons, is minimized. This allows for minimizing the protrusion of the conductor rod ends onto the stator laminations. However, in such an embodiment, care must be taken that the first jaw wall is shorter than the profile width and / or the second jaw wall is shorter than twice the profile height. Otherwise, the clamping jaws may collide with each other undesirably. However, the second clamping jaw should be longer than the simple profile height so that, in the event of any lateral offset at the end, it can laterally "capture" the end that is not primarily captured by it. The longer the second jaw wall, the larger the initial gap between the mating surfaces.

[0018] In the closed variant, each clamping jaw defines a completely enclosed portion of space perpendicular to the axial direction of the weld pair, where the clamping space corresponds to the overlap of two portion spaces. In other words, each clamping jaw has a clamping through-hole through which the weld pair protrudes. In this case, the two clamping jaws are arranged at different heights relative to the axial direction of the weld pair. Therefore, in addition to the movable jaw walls also present in the open variant, each clamping jaw also has two opposing inactive jaw walls that are not used in the actual clamping process. These contribute to stability, which can be structurally translated into a reduction in the minimum thickness of the clamping jaws. This helps to suppress the increase in the axial mounting space of the clamping device, a problem caused by the need for the clamping jaws to be arranged at different axial heights. It should be understood that the size of the clamping through-hole defining the clamping space must be excessive relative to the weld pair, including its manufacturing and positioning tolerances. This excessive size defines the tolerable deviations in the desired positioning and dimensions of the ends relative to each other.

[0019] The clamp according to the invention can advantageously grip multiple welding pairs simultaneously. For this purpose, preferably, each clamping jaw is part of a clamping disc comprising multiple clamping jaws. In the open variant, these clamping discs have toothed edges facing each other, the toothed sides representing the first and second jaw walls, respectively. In the closed variant, the clamping discs have a corresponding row of clamping through holes near their facing edges.

[0020] As explained at the beginning, welding of the weld pairs preferably occurs on the hairpins already inserted into the lamination assembly. The weld pairs form a complex, dense arrangement that extends parallel to the end walls of the lamination assembly on the torsional or welding side of the assembly. This makes individual weld pairs of the clamp more difficult to access, especially when the clamp is designed with two clamping discs having relatively large surface areas. Therefore, in a further development of the invention, an arrangement is provided in which each clamping disc has clearance through-holes that correspond in arrangement and size to the arrangement of multiple weld pairs held in the retaining device. Such clamping discs can be fitted axially onto the arrangement of the weld pairs. When the clamping discs are facing each other, only the clamping jaws are active. The clearance through-holes are so large that they do not, or at least do not collide uncomfortably with the weld pairs (already welded or still to be welded) passing through them. In this way, the clamping discs can have almost any desired size, which benefits their stability and thus reduces the minimum thickness they require.

[0021] In the context of the above description, retainers for holding conductor rods or weld pairs are generally referred to. However, as mentioned earlier, this is preferably a retainer for indirectly holding one or more weld pairs. Therefore, preferably, the retainer has a retaining element for directly holding the lamination assembly of the motor stator, which in turn has a longitudinal channel for directly holding the conductor rod.

[0022] The method for manufacturing an electric motor stator using such an alignment device according to the invention preferably includes the following steps:

[0023] a) The retainer holds the stack of laminations with multiple conductor rods.

[0024] Each end of the conductor rod has a (preferably substantially rectangular) profile with a profile width and profile height, protruding beyond the lamination assembly on one side, aligned in a common axial direction, and forming a pair of welded pairs with mating surfaces facing each other and extending perpendicular to the profile height.

[0025] Furthermore, the weld pairs are arranged in the lamination group in a predetermined pattern perpendicular to the axial direction.

[0026] (b) The clamping disc is fed axially so that each weld pair is inserted into the clamping space or the clearance through hole.

[0027] (c) The radial feed clamping disc moves toward each other in the direction of the respective diagonals of the corners connecting their claw angles, thereby pressing the ends located in the respective clamping spaces together through their mating surfaces.

[0028] d) Weld the ends of each compression weld pair together.

[0029] Since hairpins are typically inserted into the stator at excessive lengths, it is preferable to perform a step of cutting the length of each compressed weld pair between the step of radially advancing the clamping disc and the step of welding the ends of each pressed weld pair, wherein the ends of the respective weld pairs are cut at the same axial height on the side of the clamping disc facing away from the stack. Attached Figure Description

[0030] Other features and advantages of the invention will become apparent from the following detailed description and drawings.

[0031] In the attached diagram:

[0032] Figure 1 A schematic plan view of the end face of a prefabricated stack of wafers with a ready-to-use clamp according to the alignment device of the present invention is shown.

[0033] Figure 2 This shows the start of the clamping step. Figure 1 The magnified representation of magnified details is indicated by II in the text.

[0034] Figure 3 Show Figure 2 Details at the end of the clamping step

[0035] Figure 4 Two clamping discs are shown as an alternative embodiment of the clamp of the alignment device according to the invention, and

[0036] Figure 5 It is shown Figure 4 A schematic cross-sectional diagram illustrating the working principle of the fixture.

[0037] The same reference numerals in the accompanying drawings denote the same or similar elements. Detailed Implementation

[0038] Figure 1 The clamp 10 of the alignment device according to the invention is shown in a highly schematic manner in an operating position on a preform blank. Figure 2 and Figure 3 It shows Figure 1 A magnified view of region II in the image shows the different processing times. Unless otherwise explicitly stated, these will be described together below. Figures 1 to 3 .

[0039] The stator blank includes a lamination assembly 40 with axial channels, wherein conductor rods are pre-fixed, specifically so-called hairpins, i.e., conductor rods connected by bent portions (not shown). Figure 1 Only the ends 51 and 52 of the conductor rod extending axially in the lamination group 40 are shown. In particular, the two ends 51 and 52 are associated with the welding pair 50, respectively. Figure 1The positions of ends 51 and 52 shown do not correspond to their positions extending beyond the end faces of the laminate assembly 40. For clarity, Figure 1 The bending transition region between the illustrated ends 51, 52 and their exit position from the stack 40, created by the preceding forming process (i.e., so-called twisting), is not shown. In the context of this invention, it is only necessary to note that, respectively, the two ends 51, 52 assembled into the weld pair 50 will be pressed together by their mating surfaces 53 facing each other so that they can subsequently be welded together. The clamp 10 according to the invention is used for this clamping operation. Figure 1 In the illustrated embodiment, it includes two clamping discs 20, 30, which can move relative to each other according to the white arrows. Figure 1 The clamping operation shown begins at the position where Figure 2 The details are shown in magnified form.

[0040] The opposing edges of the clamping discs 20 and 30 are serrated, creating a series (four in the illustrated embodiment) of clamping spaces 11 between the clamping discs 20 and 30 of the clamping fixture 10. Each clamping space 11 is defined by two clamping claws formed by the teeth of the clamping disc edges, each claw having a first claw wall 21 and 31 and a second claw wall 22 and 32, respectively. The first claw walls 21 and 31 are perpendicular to the correspondingly associated second claw walls 22 and 32. In particular, the first claw walls 21 and 31 are oriented perpendicular to the profile height of the ends 51 and 52, i.e., parallel to the mating surface 53 of the correspondingly associated weld pair 50, or perpendicular to the gap between the ends 51 and 52, which will be reduced by contact pressure. On the other hand, the second claw walls 22 and 32 are perpendicular to the profile width of the ends 51 and 52, i.e., perpendicular to the mating surface 53 of the correspondingly associated weld pair 50, or parallel to the gap between the ends 51 and 52.

[0041] In order to achieve respectively Figure 1 and Figure 2 In the indicated state, the clamp 10 moves axially upward to the stack 40 pre-assembled with the welding pairs 50, such that the actual welding pairs 50, i.e., the ends 51, 52 to be welded together in the subsequent welding step, are positioned in the clamping space 11. In other words, the clamp 10 is fitted onto the welding pairs 50. To avoid collisions with remaining welding pairs that have been welded in previous welding steps or will still be welded in subsequent welding steps, the clamping discs 20, 30 have corresponding clearance through holes 23, 33 through which non-actual welding pairs 50 that are prone to collision can protrude.

[0042] In order to perform the clamping steps according to the invention, such as Figure 1 The white arrow in the middle and Figure 2As indicated by the black arrows, the clamping jaws move diagonally relative to each other (relative to the clamping space). Therefore, the clamping space 11 decreases, and the ends 51, 52 of the actual weld pair 50 move toward each other in both their profile width and profile height directions until their mating surfaces 53 are abutting each other across the entire surface. This situation is as follows: Figure 3 As shown.

[0043] During this process, the clearance holes 23 and 33 do not change their dimensions. Although they move in position relative to the non-current welding pair 50 they enclose, the clearance holes 23 and 33 are too large relative to the non-current welding pair 50, thus not hindering the clamping process of the current welding pair 50 described above.

[0044] As can be seen, by means of the method according to the invention, even with considerable tolerances, particularly for weld pairs 50 aligned laterally and rotationally offset, their mating surfaces are precisely pressed together across the entire surface, allowing subsequent welding processes to be performed with high reproducibility. In particular, since the second claw walls 22, 32 are longer than the simple profile height in the illustrated exemplary embodiment, the laterally offset ends 51, 52 of the weld pair 50 can be laterally "captured".

[0045] In order to clamp the next row of welding pairs 50, after the actual welding pairs 50 are welded, the clamp 10 first moves upward again, then lifts axially, moves further in azimuth relative to the prefabricated stack 40, and moves axially onto the stack 40 again.

[0046] Figure 4 An alternative embodiment of the clamp 10 with two clamping discs 20, 30 is shown, which have closed clamping channels 24, 34 instead of open partial clamping spaces. Figure 4 The clamping discs 20 and 30, shown separately and spaced apart from each other, are arranged at different axial heights during use and have overlapping clamping through holes 24 and 34. According to Figure 4 The relative displacement of clamping discs 20 and 30 (marked by the white arrow) causes... Figures 1 to 3 The open variant of the fixture 10 shown yields the same result, so the above can be referenced in this regard.

[0047] Figure 5 Again shown in a highly schematic cross-section Figure 4 The clamping discs 20 and 30 of the closed variant of the clamp 10 are arranged. Furthermore, Figure 5 The step of cutting the length of the weld pair 50 along the cutting line is shown, preferably performed between the clamping and welding steps. Of course, this intermediate step can also be performed in the case of welding the weld pair 50, which is clamped through the opening of the clamp 10.

[0048] Of course, the embodiments discussed in the detailed description and shown in the accompanying drawings are merely illustrative embodiments of the invention. Based on the disclosure herein, those skilled in the art will recognize a wide range of possibilities for variation. Particularly in the closed-loop variant embodiments, it is conceivable to clamp multiple weld pairs 50 simultaneously; however, in this case, a compromise must be made regarding the feed direction relative to the perfect diagonal of the clamping jaws, which is practically preferred but not absolutely necessary.

[0049] List of reference numerals

[0050] 10 clamps

[0051] 11 Clamping Space

[0052] 20 clamping discs

[0053] 21 First Claw Wall

[0054] 22 Second Claw Wall

[0055] 23 Avoidance through hole

[0056] 24-hole clamp

[0057] 30 clamping disc

[0058] 31 First Claw Wall

[0059] 32 Second Claw Wall

[0060] 33 Avoidance through hole

[0061] 34 clamp through holes

[0062] 40 stacks

[0063] 50 welding pairs

[0064] 51 (the end of the conductor rod)

[0065] 52 (the end of the conductor rod)

[0066] 53 Joint Surface

[0067] 60 cutting line

Claims

1. A device for aligning the ends (51, 52) of electrical conductor rods to be welded together, comprising: - A retainer for holding the conductor rod in a predetermined position, wherein two ends (51, 52) forming a weld pair (50) are arranged adjacent to each other, each end including a profile having a profile width and a profile height perpendicular thereto, such that mating surfaces (53) extending perpendicularly to the profile height are aligned facing each other, and - A clamp (10) having two clamping jaws (11) defining a clamping space (11), the two clamping jaws being movable relative to each other in a direction that reduces the clamping space (11), wherein, The clamp (10) can be positioned such that the welding pair (50) passes axially through the clamping space (11). Its features are, - Each clamping jaw has two jaw walls (21, 22; 31, 32) arranged at right angles to each other, namely the first jaw wall (21; 31) and the second jaw wall (22; 32), wherein the second jaw wall (22; 32) is longer than the profile height. - The clamp can be positioned such that its first claw walls (21; 31) are aligned parallel to the mating surface (53), and - The clamping claws can move relative to each other in the diagonal direction of the corner vertices of the claws that connect them.

2. The apparatus according to claim 1, Its features are, Each clamping jaw defines a portion of the clamping space (11), which is open to the corresponding other clamping jaw.

3. The apparatus according to claim 2, Its features are, The first claw wall (21; 31) is shorter than the profile width and / or the second claw wall (22; 32) is shorter than twice the profile height.

4. The apparatus according to claim 3, Its features are, The clamping jaws are arranged at the same height relative to the axial arrangement of the welding pair (50).

5. The apparatus according to claim 1, Its features are, Each clamping jaw defines a fully enclosed partial space perpendicular to the axial direction of the welding pair (50), wherein the clamping space (11) corresponds to the overlap of the two partial spaces.

6. The apparatus according to claim 5, Its features are, The clamping jaws are arranged at different heights relative to the axial arrangement of the welding pair (50).

7. The apparatus according to any of the preceding claims, Its features are, Each clamping jaw is part of a clamping disc that includes multiple clamping jaws.

8. The apparatus according to claim 7, Its features are, Each clamping disc (20; 30) has an arrangement of clearance through holes (23; 33) that corresponds in arrangement and size to the arrangement of multiple weld pairs (50) held in the retaining device.

9. The apparatus according to any one of the preceding claims, Its features are, The retainer is configured to indirectly retain one or more pairs of welds (50) by means of retaining elements for directly retaining the laminations (40) for the motor stator, the laminations having longitudinal channels for directly retaining the conductor rods.

10. A method for manufacturing an electric motor stator using the apparatus of claims 8 and 9, comprising the following steps: a) The retainer holds the stack of laminations with multiple conductor rods. The ends (51, 52) of the conductor rod each have a profile including a profile width and a profile height. The ends protrude beyond the lamination assembly (40) on one side, are aligned in a common axial direction, and form welding pairs (50) respectively, having mating surfaces (53) facing each other and extending along the profile width. Furthermore, the weld pairs (50) are arranged in the lamination group (40) in a predetermined arrangement pattern perpendicular to the axial direction. (b) Axially feed the clamping discs (20; 30) so that each weld pair (50) is inserted into the clamping space (11) or the clearance through hole (23; 33), respectively. (c) The clamping discs (20; 30) are radially fed such that the clamping jaws, which define the clamping spaces (11) in pairs, move toward each other in the direction of the respective diagonals of the corners connecting their jaw angles, thereby pressing the ends (51, 52) located in the respective clamping spaces (11) together through their mating surfaces (53), and d) Weld the ends (51, 52) of each pressed-together weld pair (50) together.

11. The method according to claim 10, Its features are, Between the step of radially feeding the clamping disc (20; 30) and the step of welding the ends (51, 52) of each compressed weld pair (50) together, a step of cutting the length of each compressed weld pair (50) is performed, wherein the ends (51, 52) of the corresponding weld pair (50) are cut at the same axial height on the side of the clamping disc (20; 30) facing away from the stack (40).

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