Stator manufacturing using a brazing method

Abstract

The invention relates to a method for producing a hairpin winding for driving a stator of an electric motor of a motor vehicle. First, a stator base body having a plurality of stator slots is provided. The hair pins (1) are then arranged in the stator slots such that the free hair pin ends (2) of the hair pins (1) protrude from the stator base body in the axial direction. One of the free hairpin ends (2) is arranged on the current conductor (3). Finally, the free pin end (2) is connected to the current conductor (3) by brazing. According to the invention, a hard solder (4) is arranged on the free hair pin end (2) before the free hair pin end (2) is connected to the current conductor (3).

Description

TECHNICAL FIELD

[0001] The invention relates to a method for producing a hairpin winding of a stator of an electric motor for driving a motor vehicle. BACKGROUND

[0002] Methods for producing a hairpin winding of a stator of an electric motor for driving a motor vehicle are known, in which a hard solder platelet is arranged at a busbar and a hairpin to be connected with the busbar is bent towards the hard solder platelet. Here, the hard solder has to be arranged and fixed on the busbar particularly dimensionally accurately, for example via a spot welding method or the like. Subsequently, the busbar has to be aligned dimensionally accurately with the hairpin in order to fix the hairpin at the busbar by means of a hard soldering method. Here, it is particularly problematic that the hairpin has to be aligned accurately with the busbar in order to provide the hard solder sufficiently for the hard soldering. In the case of too great a misalignment between the hairpin and the hard solder, the connection between the hairpin and the busbar can have insufficient strength, with the result that the rejection rate is increased.

[0003] A method for producing a hairpin winding is known from document DE 10 2012 215 309 B4, in which two conductor ends to be connected with one another are arranged parallel to one another and next to one another. A solder platelet is arranged between the conductor ends. Subsequently, the conductor ends are pressed against one another and welded to one another by means of a soldering process. The solder platelet can be supplied by means of a coil or as a strip. Document CN 102 362 416 B shows another method for soldering conductor ends of a hairpin winding. A solder platelet is arranged in a recess of a carrier strip and arranged between the hairpin ends to be soldered by means of the carrier strip. After the soldering process, the carrier strip is removed again. Both methods have the disadvantage that a very accurate alignment between the hairpin ends to be connected and the solder platelet is also required. SUMMARY

[0004] It is therefore an object of the present invention to eliminate or at least partially eliminate the above-mentioned disadvantages in a method for producing a hairpin winding of a stator of an electric motor for driving a motor vehicle. In particular, it is an object of the present invention to provide a method for producing a hairpin winding of a stator of an electric motor for driving a motor vehicle, which has a lower rejection rate in a simple and cost-advantageous manner and / or places lower requirements on the orientation of the hairpin when connecting with the current conductor.

[0005] The above-mentioned object is achieved by the present invention. Accordingly, the object is achieved by a method for producing a hairpin winding of a stator of an electric motor for driving a motor vehicle according to the invention. Further features and details of the invention result from the description and the drawings.

[0006] According to the invention, the object is achieved by a method for producing a hairpin winding of a stator of an electric motor for driving a motor vehicle. The method has:

[0007] - providing a stator base with a plurality of stator slots,

[0008] - arranging hairpins in the stator slots such that the free hairpin ends of the hairpins project in axial direction from the stator base,

[0009] - arranging one of the free hairpin ends at a current conductor, and

[0010] - connecting the free hairpin end with the current conductor by brazing.

[0011] According to the invention, a brazing material is arranged at the free hairpin end before connecting the free hairpin end with the current conductor.

[0012] First, a stator base is provided. The stator base extends along a stator longitudinal axis and is preferably constructed as a plate pack of a plurality of coaxially arranged plate pieces, for example of electrical sheets. The plate pieces preferably have an electrically insulating portion, for example a lacquer consisting of back lacquer or the like, in order to avoid a current flow through the plate pack. The stator base preferably has a plurality of stator teeth, wherein a stator slot is constructed between two stator teeth, respectively. The stator slots are preferably uniformly distributed over the circumference of the stator and have a slot length along the stator longitudinal axis, a slot depth in radial direction and a slot width in circumferential or tangential direction. The stator slots are open at both axial end portions of the stator base, which are also referred to as "stator end sides". The stator slots are preferably open towards the stator longitudinal axis.

[0013] Next, hairpins are arranged in the stator slots, for example by plugging in axial direction from the first stator end side towards the second stator end side. According to the invention, the hairpins can be constructed as I-hairpins or U-hairpins, for example. The arrangement of the hairpins in the stator slots is performed such that the free hairpin ends of the hairpins project in axial direction from the stator base at the stator end sides. The hairpins are preferably arranged in a plurality of hairpin layers in radial direction in the stator slots.

[0014] The free hairpin end or the free hairpin ends of one or more hairpins are arranged at a current conductor. The current conductor can be constructed as a busbar, in particular a copper busbar, for example, for electrically coupling the stator with a control device or power electronics for operating the electric motor. The arrangement of the free hairpin end at the current conductor can be achieved by plastic deformation of the hairpin, for example by interleaving or the like, for example. Further preferably, the free hairpin end is held in a brazing position at the current conductor, where the brazing process is to be performed, by a holding device.

[0015] Finally, the free hairpin end or the free hairpin ends arranged at the current conductor are connected with the current conductor by brazing. In this way, a mechanical and electrical coupling is established between the hairpin or the hairpins and the current conductor. Next, the holding device is removed from the hairpin.

[0016] According to the application, the hard solder is arranged at the free pin end beforehand, so that the hard solder is always arranged correctly between the free pin end and the current conductor even in the case of a large deviation of the predefined relative position of the free pin end to the current conductor.

[0017] The method according to the application for manufacturing a pin-finish winding of a stator of an electric motor for driving a motor vehicle has the advantage over conventional methods that a soldered connection between the pin and the current conductor can be established in a simple manner and in a cost-effective manner. By arranging the hard solder at the free pin end, it is ensured that the hard solder is advantageously arranged for the hard-soldering process after the pin end has been arranged at the current conductor. This enables a large tolerance in arranging the free pin end at the current conductor, so that complex, precise alignment movements can be dispensed with. A high product quality is thus ensured with reduced manufacturing outlay.

[0018] According to a preferred refinement of the application, in the method for manufacturing a pin-finish winding of a stator it can be provided that the hard solder is fixed as a hard-solder plate at the free pin end. The hard-solder plate can have, for example, a rectangular, in particular square, base. Preferably, the hard-solder plate has a constant thickness. The length and / or the width of the hard-solder plate is preferably at least five times, preferably at least ten times, as large as the thickness of the hard-solder plate. The length and / or the width of the hard-solder plate is preferably at most forty times, preferably at most twenty times, as large as the thickness of the hard-solder plate. The hard-solder plate can be fixed at the pin end, for example, by adhesive bonding. This is achieved in such a way that, after the hard soldering, an electrical connection between the pin and the current conductor is additionally ensured. Thus, for example, an adhesive can be provided which wets only a comparatively small area of the hard solder, so that there is additionally direct contact between the hard solder and the pin. Alternatively or additionally, an adhesive can be provided which evaporates during the hard soldering, so that no electrical insulation between the pin and the current conductor is formed by the adhesive. This has the advantage that reliable arrangement and secure retention of the hard solder at the pin end is ensured in a simple manner and in a cost-effective manner.

[0019] It is preferred according to the application that the hard solder is slipped as a hard solder cap onto the free pin end. In the context of the application, a cap is understood to be such a configuration of the hard solder in which the free pin end can be surrounded from at least three sides. The cap is preferably configured to surround the free pin end from four or five sides. The cap can for example have an approximately ring-shaped configuration with two free openings. According to the application, the cap can also have a main side of a plate-like configuration and a plurality of secondary sides of a wire-like configuration, wherein the main side is provided for arrangement between the free pin end and the current conductor. The secondary sides are therefore only used for the fixation of the main side at the free pin end. The cap preferably has an inner cross section which corresponds or at least approximately corresponds in shape and size to the outer cross section of the free pin end, so that the slipping of the cap onto the free pin end can be easily achieved. Preferably, the cap has a widening at the free openings, so that the cap is easily arranged on the free pin end. Preferably, the inner cavity of the cap has a tapering from the free openings, so that the cap can be caused to grip on the free pin end when slipped on. This has the advantage that the reliable arrangement and secure holding of the hard solder at the pin end is ensured in a cost-advantageous manner with simple means.

[0020] It is further preferred that the hard solder is fixed at the free pin end via spot welding or soldering. It is preferred here that the hard solder is configured as a hard solder platelet. The spot welding is preferably carried out on the face center of the hard solder. The hard solder is reliably held at the free pin end by the spot welding. This has the advantage that the reliable arrangement and secure holding of the hard solder at the pin end is ensured in a cost-advantageous manner with simple means.

[0021] In a particularly preferred design of the application, it can be provided in the method for manufacturing a pin-type winding of a stator of an electric motor that the hard solder is fixed at the free pin end by plastic deformation. The plastic deformation can for example be achieved via crimping, tamping, etc. It can for example be provided that the hard solder has a bulge on both sides of the free pin end in the width direction of the pin, which is bent around the free pin end according to the clamp via plastic deformation. Alternatively, for example a point-like or line-like pressure can be applied to the hard solder, by which a portion of the hard solder is pressed into the pin end, so that a mechanical tamping is created between the hard solder and the pin end. In order to reduce the process forces required for this, it can be provided that a surface treatment, for example roughening, knurling, etc., is carried out beforehand at the free pin end. This has the advantage that the reliable arrangement and secure holding of the hard solder at the pin end is ensured in a cost-advantageous manner with simple means.

[0022] Preferably, the hard solder is arranged at the free hairpin end before the hairpin is arranged in the stator slot. Thus, the hairpin is subjected to a treatment in which the hard solder is arranged at the free hairpin end before the hairpin is arranged in the stator slot. The arrangement of the hard solder is preferably effected here in such a way that the arrangement of the hairpin in the stator slot is not impeded by the hard solder and the hard solder remains at the free hairpin end when the hairpin is arranged in the stator slot. It can be provided, for example, that a hard solder having a chamfer is provided, through which the hairpin can be caused to slide better in the stator slot. This has the advantage that the hairpin is finished in pre-production with simple means and in a cost-advantageous manner, so that the arrangement of the hard solder does not have to be carried out again in the final manufacture of the stator. The production efficiency can thus be further improved.

[0023] According to a preferred embodiment of the application, the hairpin is separated and / or staggered before or during the arrangement of the hard solder at the free hairpin end. It is preferred in this context that the arrangement of the hard solder is effected after the hairpin has been arranged in the stator slot. The process sequence can be, for example, that the hairpin is first arranged in the stator slot, then the hard solder is arranged at the free hairpin end and preferably fixed, and then the separation and / or staggering of the free hairpin end is effected. Alternatively thereto, the separation and / or staggering of the free hairpin end can also be carried out only after the hairpin has been arranged in the stator slot, wherein the arrangement of the hard solder at the free hairpin end can be effected only in the separated or staggered state. According to a further alternative, the hard solder can be arranged at the free hairpin end via the tool used for the separation or staggering, so that the arrangement of the hard solder at the free hairpin end takes place simultaneously with the separation or staggering. This has the advantage that a reliable arrangement of the hard solder at the hairpin end and a secure holding are ensured with simple means and in a cost-advantageous manner.

[0024] It is particularly preferred that the hard solder is arranged at each of the free hairpin ends. It can be provided, for example, that in addition to the fixing of the free hairpin end at the current conductor, the other free hairpin ends of the hairpin are to be connected to one another in pairs, for example, for forming a winding head of the stator. This can also be effected by brazing. By arranging the hard solder at all the free hairpin ends, the number of variants of the hairpin can be reduced, so that it can be better manufactured in pre-production, in which the hard solder is arranged at the free hairpin end. The hairpin ends to be connected to one another now already have the hard solder, so that the brazing process can be carried out directly after the separation and staggering. This has the advantage that the manufacturing efficiency of the stator is further improved with simple means and in a cost-advantageous manner.

[0025] It is preferred according to the application that a hard solder is provided with a width which is less than or equal to the width of the free needle end. It is further preferred that the hard solder is provided at the free needle end in such a way that the hard solder ends laterally flush with the free needle end or at least is not raised laterally in relation to the free needle end. This has the advantage that a reliable arrangement and secure holding of the hard solder at the needle end is ensured in a simple manner and in a cost-effective manner. Furthermore, a waste of hard solder can thus be avoided.

[0026] It is preferred that a recess is produced at the free needle end before the hard solder is arranged at the free needle end, wherein the hard solder is arranged at least partially in the recess. For example, the recess can be configured as a flat, wherein the free needle end has a smaller thickness in the region of the flat than beside the flat. Alternatively, the recess can also be configured as a shaped portion in which the thickness of the free needle end remains constant and the free needle end thus has a corresponding elevation on the side facing away from the recess. The recess preferably extends over the full width of the free needle end. It is further preferred that the recess extends in the longitudinal direction of the needle to the edge of the free needle end. Alternatively, the recess can also be configured spaced apart from one or more edges of the free needle end. It is preferred that the hard solder is arranged at the recess by pressing in, so that the hard solder is held at the free needle end. This has the advantage that a reliable arrangement and secure holding of the hard solder at the needle end is ensured in a simple manner and in a cost-effective manner. BRIEF DESCRIPTION OF DRAWINGS

[0027] The method according to the application for producing a needle-shaped winding for a stator of an electric motor for driving a motor vehicle is explained in more detail below with reference to the drawings. The respective schematic:

[0028] Figure 1 A current conductor configured as a busbar when carrying out the method according to the prior art is shown in a top view,

[0029] Figure 2 A free needle end during the execution of a preferred first implementation form of the method according to the application is shown in a top view,

[0030] Figure 3 A free needle end during the execution of a preferred second implementation form of the method according to the application is shown in a top view,

[0031] Figure 4 A current conductor configured as a busbar when carrying out a preferred implementation form of the method according to the application, and

[0032] Figure 5 A preferred implementation form of the method according to the application is shown in a flowchart.

[0033] InFigures 1 to 5 In the figures, elements having the same function and mode of action are provided with the same reference signs. DETAILED DESCRIPTION

[0034] In Figure 1 In the top view, a current conductor 3 configured as busbar when performing a method according to the prior art is schematically illustrated in a top view. The current conductor 3 has three hard solders 4 configured as hard solder plates which are arranged at defined positions at the current conductor 3 spaced apart from one another. Furthermore, three free needle ends 2 of three needles 1 are schematically illustrated which are aligned to the current conductor 3 during the manufacture of the stator. The needle 1 left in the view has the correct orientation with respect to the associated hard solder 4. The needle 1 in the middle in the view has an orientation with a small left offset with respect to the associated hard solder 4. The needle 1 right in the view has an orientation with a large left offset with respect to the associated hard solder 4. These offsets can easily arise when aligning the needles 1 to the current conductor 3 and can lead to faulty hard solder connections between the needles 1 and the current conductor 3.

[0035] Figure 2 The free needle end 2 of a needle 1 during the performance of the preferred first implementation form of the method according to the application is schematically illustrated in a top view. A hard solder 4 configured as hard solder plate is arranged at the free needle end 2. The hard solder 4 is fixed at the needle 1 by a spot weld 5.

[0036] In Figure 3 The free needle end 2 of a needle 1 during the performance of the preferred second implementation form of the method according to the application is schematically illustrated in a top view. A hard solder 4 configured as hard solder cap is arranged at the free needle end 2. The cap preferably has a slight undersize with respect to the free needle end 2 so that the cap clamps on the free needle end 2. In addition, the hard solder 4 is fixed at the needle 1 by a spot weld 5 which is optional in this case.

[0037] Figure 4 The current conductor 3 configured as busbar when performing the preferred implementation form of the method according to the application is schematically illustrated in a top view. In front of the current conductor 3, three free needle ends 2 of three needles 1 are schematically illustrated which are aligned to the current conductor 3 during the manufacture of the stator. Since the hard solder 4 is always arranged and fixed at the free needle end 2 first when performing the method according to the application, it is ensured that the hard solder 4 is arranged correctly between the needle 1 and the current conductor 3 even in the case of an offset between the needle 1 and the current conductor 3. Thus, the requirements for the alignment of the needle 1 to the current conductor 3 are significantly lower compared to the prior art.

[0038] In Figure 5A preferred embodiment of the method according to the application is presented schematically in a flow chart. In a first method action 100, a stator base body with a plurality of stator slots is provided. In a second method action 200, a field pin 1 is provided, which is arranged and fixed at its field pin end 2 with a hard solder 4 configured as a hard solder plate. In a third method action 300, the field pin 1 is arranged in a stator slot in such a way that the free field pin end 2 projects axially from the stator base body. In a fourth method action 400, at least one of the free field pin ends 2, at which the hard solder 4 is arranged, is arranged at a current conductor 3. In a fifth method action 500, the free field pin end 2 is connected to the current conductor 3 by means of a hard soldering. Here, the hard solder 4 arranged at the free field pin end 2 is first melted and then solidified again.

[0039] List of reference signs

[0040] 1 field pin

[0041] 2 free field pin end

[0042] 3 current conductor

[0043] 4 hard solder

[0044] 5 spot weld

[0045] 100 first method action

[0046] 200 second method action

[0047] 300 third method action

[0048] 400 fourth method action

[0049] 500 fifth method action.

Claims

1. A method for manufacturing a stator winding of an electric motor for driving a motor vehicle, comprising: - Provides a stator base with multiple stator slots; - Arrange the hairpin (1) in the stator slot such that the free hairpin end (2) of the hairpin (1) extends axially from the stator base; - Place one of the free needle ends (2) at the current conductor (3); and - The free hairpin end (2) is connected to the current conductor (3) by hard soldering. Its features are, Before connecting the free needle end (2) to the current conductor (3), hard solder (4) is applied to the free needle end (2).

2. The method according to claim 1, Its features are, The hard solder (4) is fixed as a hard solder plate at the free needle end (2).

3. The method according to claim 1 or 2, Its features are, The hard solder (4) is flipped onto the free needle end (2) as a hard solder cap.

4. The method according to any one of the preceding claims, Its features are, The hard solder (4) is fixed at the free needle end (2) by spot welding or brazing.

5. The method according to any one of the preceding claims, Its features are, The hard solder (4) is fixed at the free needle end (2) by plastic deformation.

6. The method according to any one of the preceding claims, Its features are, Before placing the hairpin (1) in the stator slot, the hard solder (4) is placed at the free hairpin end (2).

7. The method according to any one of claims 1 to 5, Its features are, Before or during the placement of the hard solder (4) at the free needle end (2), the needles (1) are separated and / or interleaved.

8. The method according to any one of the preceding claims, Its features are, The hard solder (4) is placed at each of the free needle ends (2).

9. The method according to any one of the preceding claims, Its features are, Provide a hard solder (4) with a width less than or equal to the width of the free needle tip (2).

10. The method according to any one of the preceding claims, Its features are, Before the hard solder (4) is placed at the free needle end (2), a recess is made at the free needle end (2), wherein the hard solder (4) is at least partially placed in the recess.

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