Method for producing a winding head of a hairpin motor component

Abstract

The present invention relates to a method for producing a winding head of a hairpin motor component for an electric motor for driving a motor vehicle. The method comprises: - Providing a component base body with a longitudinal axis and a plurality of base body grooves extending along the longitudinal axis, wherein hairpins (1) are arranged in the base body grooves, wherein hairpin ends (2) of the hairpins (1) protrude from the base body grooves in the axial direction (A), - Targeted grouping of adjacent hairpin ends (2) into hairpin end pairs (3), - Materially connecting the hairpin ends (2) within the hairpin end pairs (3) to create hairpin end pair connections. According to the invention, the material connection of the hairpin ends (2) is carried out by resistance brazing.

Description

[0001] The present invention relates to a method for producing a winding head of a hairpin motor component for an electric machine for driving a motor vehicle.

[0002] Electric motors for driving motor vehicles are known in which a winding of a motor component, such as a stator, is not made from a single wound wire, but from a plurality of rod-shaped or hairpin-shaped conductor elements. Due to the geometry of these conductor elements, they are also referred to as "hairpins." Hairpins are either rod-shaped or have a central section bent by 180° and two legs. Rod-shaped hairpins are sometimes also referred to as "I-pins." Hairpins with a bent section and two legs are also known as "U-pins."

[0003] During the production of the engine component, the hairpins are inserted into the base body grooves of the engine component's base body such that the hairpin ends protrude axially from the base body grooves on at least one end face of the component's base body. With I-pins, the hairpin ends protrude from the component's base body on both end faces. With U-pins, the hairpin ends protrude from one end face, and the bent areas protrude from the component's base body on the other end face. The legs of a U-pin are arranged in different base body grooves.

[0004] In each base body groove, several hairpins or legs, for example four, six, or eight, are arranged next to each other in the radial direction. The areas of the hairpins arranged in the base body grooves are usually electrically insulated, for example, by means of a varnish, additional insulating strips, or the like.

[0005] Furthermore, the hairpin ends are bent in the circumferential direction, partly clockwise and partly counterclockwise, such that hairpin ends of different base body slots are arranged adjacent to one another. Bending can occur before or after the hairpins are inserted into the base body slots. The adjacent hairpin ends are captured, clamped, cut to length, and joined together as hairpin end pairs on the front side of the component base body by a holding tool. The joined ends are always achieved using a welding process, such as laser beam welding, electron beam welding, TIG welding, or the like. Such methods for producing winding heads for traction machines are known, for example, from documents DE 10 2012 215 309 B4 and DE 10 2006 019 312 A1.

[0006] Known processes for manufacturing winding heads of hairpin motor components for electric motors used to power motor vehicles have the disadvantage that the integral joining of the hairpin end pairs by welding can lead to relatively high rejection rates of approximately 1% to 2%. This results in increased overall costs for the production of electric motors used to power motor vehicles.

[0007] It is therefore an object of the present invention to eliminate, or at least partially eliminate, the disadvantages described above in the manufacture of electric machines for driving motor vehicles. In particular, it is an object of the present invention to provide a method for producing a winding head of a hairpin motor component for an electric machine for driving a motor vehicle, which method reduces rejects and / or required rework and thus the costs of manufacturing electric machines for driving motor vehicles in a simple and cost-effective manner.

[0008] The above object is achieved by the patent claims. Accordingly, the object is achieved by a method for producing a winding head of a hairpin motor component for an electric machine for driving a motor vehicle, having the features of independent claim 1. Further features and details of the invention emerge from the subclaims, the description, and the drawings.

[0009] According to the invention, the object is achieved by a method for producing a winding head of a hairpin motor component for an electric machine for driving a motor vehicle. The method comprises: - Providing a component base body with a longitudinal axis and a plurality of base body grooves extending along the longitudinal axis, wherein hairpins are arranged in the base body grooves, wherein hairpin ends of the hairpins protrude from the base body grooves in the axial direction, - Targeted grouping of adjacent hairpin ends into hairpin end pairs, - Material-to-material connection of the hairpin ends within the hairpin end pairs to produce hairpin end pair connections. According to the invention, the material-to-material connection of the hairpin ends is carried out by resistance brazing.

[0010] The winding head of a hairpin motor component is an area of the motor component in which hairpins from different base body slots are connected to one another. The term originally comes from motor components that use a wound wire to generate a magnetic field and is also used for hairpin motor components due to the technical similarity. The winding head is located on one end of the base body. The motor component can be, for example, a stator or a rotor for an electric machine.

[0011] The provided component base body has the base body with the longitudinal axis. The base body grooves are formed in the component base body and are evenly distributed over the circumference of the component base body. The base body grooves extend along the longitudinal axis and have a groove depth in the radial direction.

[0012] The hairpins are inserted into the base body slots such that the hairpin ends protrude axially from the base body slots on at least one end face of the component base body. With I-pins, the hairpin ends protrude from the component base body on both ends. With U-pins, the hairpin ends protrude from one end face, and the bent areas protrude from the component base body on the other end face. The legs of a U-pin are arranged in different base body slots.

[0013] In each base body groove, several hairpins or legs, for example four, six, or eight, are arranged next to one another in the radial direction. The areas of the hairpins arranged in the base body grooves are preferably electrically insulated, for example by means of a varnish, additional insulating strips, in particular made of paper, or the like.

[0014] Furthermore, the hairpin ends are bent circumferentially, partly clockwise and partly counterclockwise, so that hairpin ends from different base body grooves are arranged adjacent to one another. Bending can occur before or after the hairpins are inserted into the base body grooves. Thus, the targeted grouping of the adjacent hairpin ends into hairpin end pairs can already be carried out when the component base body is prepared or at a later time. The adjacent hairpin ends are captured, clamped, cut to length, and firmly bonded to one another on the front side of the component base body as hairpin end pairs by a holding tool.

[0015] For the integral connection to form hairpin pairs, the hairpin end pairs are preferably clamped between two soldering electrodes, which are then energized. The energization heats the hairpin end pairs to a working temperature. The working temperature is preferably between 800°C and 900°C, particularly preferably approximately 850°C. The working temperature is preferably selected such that it is higher than the upper operating temperature of the electric machine during continuous full-load operation, thus ensuring the fatigue strength of the integral connection during operation of the electric machine.

[0016] In addition, a solder additive is used to create the material-to-material connection between the hairpin end pairs. The solder additive is applied to the hairpin end pairs and is selected such that it is fluid at the operating temperature and solid below the operating temperature. The solder additive can be provided, for example, via an additional solder wire that is brought to the hairpin end pairs. Alternatively, the hairpin end pairs can already be coated with a film of solder additive. The film thickness of the solder additive is preferably precisely determined so that a voltage drop between the soldering electrodes at the hairpin end pairs, and thus an energy input for heating the hairpin end pairs, can be precisely determined. A hard solder, in particular a copper-silver base, such as CuPAg, is preferably used as the solder additive.

[0017] A method according to the invention for producing a winding head of a hairpin motor component for an electric motor for driving a motor vehicle has the advantage over conventional methods that a material-to-material connection between the hairpin end pairs can be produced using simple means and in a cost-effective manner with a particularly low rejection rate. Furthermore, resistance brazing can significantly reduce process times for producing the material-to-material connections compared to conventional laser welding processes.

[0018] According to a preferred further development of the invention, a method can be provided that, before the hairpin end pair composite is created, a solder additive is arranged directly between and / or on the end face between the adjacent hairpin ends of the hairpin end pair. The solder additive is preferably provided as a solder plate, which is arranged between the adjacent hairpin ends and clamped during resistance brazing. A thickness of the solder plate is preferably precisely defined in order to precisely control the heat generated at the solder plate during resistance brazing. According to the invention, it can be provided that the solder platelets protrude from the hairpin end pairs in the axial direction, so that it is easily recognizable from the outside that a solder platelet is present. Furthermore, this can improve the formation of a lid during soldering at the hairpin ends.This has the advantage that the winding head can be manufactured particularly efficiently and with improved quality using simple means and in a cost-effective manner, since the amount of solder added can be dosed particularly precisely in this way.

[0019] According to the invention, it is preferred that a solder filler thickness of the solder filler and / or a solder filler material composition of the solder filler is determined based on a required voltage drop at the respective solder filler. The ohmic resistance of the solder filler can be determined via the solder filler thickness and the solder filler material composition. This resistance is relevant for the resistance brazing process, particularly when several hairpin end pairs are to be soldered simultaneously in a series circuit between the two soldering electrodes, since different temperatures can arise at the hairpin end pairs. If the temperature of the solder filler is too high or too low, this can, for example, be detrimental to the durability of the material-to-material connection. If the temperature is too high, the resistance of the solder filler is too high.By reducing the solder filler thickness and / or changing the solder filler composition to a material with higher electrical conductivity, the temperature of the solder filler can be reduced during the resistance brazing process, thus improving the quality of the bonded joint. When several solder fillers in a row are to be soldered simultaneously, the solder fillers can have different solder filler thicknesses and / or different solder filler material compositions, so that the individual temperatures during resistance brazing are the same or at least within a specified deviation. This has the advantage of further improving the quality of the bonded joint in the hairpin end pair assembly using simple means and in a cost-effective manner.

[0020] Further preferably, the hairpin end pairs are pressed together between two solder electrodes during resistance brazing. The solder electrodes preferably lie against the hairpin ends, thus establishing an electrical coupling between the respective solder electrode and the respective hairpin end. Pressing ensures that the hairpin ends of the hairpin end pair composites are arranged particularly closely next to one another.

[0021] Furthermore, a reliable current flow can be ensured during resistance brazing. This has the advantage of further improving the quality of the bonded connection in the hairpin end pair assembly using simple and cost-effective means.

[0022] In a particularly preferred embodiment of a method according to the invention, an electrically conductive spacer is arranged between adjacent hairpin end pairs to simultaneously create the hairpin end pair composites. The spacers preferably project beyond the hairpin ends in the axial direction away from the component base body. The adjacent hairpin end pairs are preferably arranged in a straight line in the radial direction, thus improving a clamped arrangement between soldering electrodes. For example, if two hairpin end pairs are to be connected to one another simultaneously, one spacer arranged between the hairpin end pairs is sufficient. If three hairpin end pairs are to be connected to one another simultaneously, one spacer is arranged between each adjacent hairpin end pair, so that two spacers are required, etc. The entire arrangement is then preferably clamped between the soldering electrodes.In this way, several soldered connections can be created simultaneously with a single current application. It can be provided that the resistance brazing takes place simultaneously at an angular offset of 180°, i.e., along the diameter of the engine component. This halves the time required to create the integral connections for one engine component. Furthermore, it can be provided according to the invention that a total of four brazing processes are carried out with an angular offset of 90°. This halves the time required to create the integral connections for one engine component compared to the 180° variant explained above. The spacers preferably have a particularly high electrical conductivity, such as copper or aluminum. By carefully selecting the brazing filler material composition and the brazing filler thickness, the temperatures during the resistance brazing process can be precisely controlled in such a series connection.After the soldering process, the spacers are removed from the hairpin ends along with the solder electrodes. This has the advantage of significantly reducing the time required to create the bonded connections using simple and cost-effective means. Furthermore, spacer adhesion to adjacent hairpin end pairs and thus short circuits in the component winding can be avoided.

[0023] The hairpins are preferably cooled by a cooling device. The cooling device is preferably arranged against a region of the hairpins that is adjacent to the hairpin ends. This region is preferably designed as an electrically insulated region that surrounds a conductor cross-section of the hairpin. Thus, the insulated region is cooled more intensively than the hairpin end, so that impairment of the soldering process is as minimal as possible, while the insulated region is better protected from impairment by heat. More preferably, cooling takes place during the soldering process, so that energy consumption for carrying out the method is as low as possible. The cooling device is preferably pressed against the hairpins, preferably flatly, so that heat transfer is improved.This has the advantage that the insulation of the hairpins is better protected from heat damage using simple means and in a cost-effective manner, thus further improving the quality of the engine component.

[0024] According to a preferred embodiment of the invention, the spacers are cooled directly by the cooling device. For this purpose, the spacers can, for example, have cooling channels through which a cooling fluid is conducted. The spacers are preferably designed such that they contact the free hairpin ends and an insulated region of the hairpins. The spacers are preferably only cooled in the insulated region so as not to hinder the soldering process. Furthermore, spacers are preferably used which minimize heat exchange between the insulated region and the hairpin end, for example by thermal insulation in an intermediate region of the spacer. The spacer can, for example, have three regions: a head region which rests against the hairpin ends, an intermediate region, and a foot region which rests against the insulated region of the hairpins. The intermediate region is preferably designed as a thermal insulator.The intermediate region is preferably also designed as an electrical insulator. The base region preferably has a particularly high thermal conductivity, so that the cooling of the insulation is improved. Asymmetric cooling is thus provided via the spacer. The head region preferably has a particularly good electrical conductivity in order to improve the soldering process. This has the advantage that the insulation of the hairpins is better protected from heat damage using simple means and in a cost-effective manner, thus further improving the quality of the engine component. Furthermore, the targeted cooling of the spacers makes it possible to reduce the number of individual work steps during the production of the engine component, since the additional moving of a separate cooling device is thus unnecessary.

[0025] Particularly preferred for resistance brazing are solder electrodes which have such different solder electrode materials that the solder electrodes have no or only a tolerated temperature difference during resistance brazing. The different solder electrode materials thus ensure that the solder electrodes are heated more evenly than with identical solder electrode materials. Additionally or alternatively, it can also be provided that the solder electrodes can have different dimensions and / or shapes for the same purpose. Molten solder additive has a tendency to flow towards the hotter solder electrode, thus creating a faulty material-to-material bond. With a more even temperature distribution, this flow is avoided or at least reduced to such an extent that the required quality of the material-to-material bond is guaranteed.This has the advantage that the quality of the engine component is further improved using simple means and in a cost-effective manner.

[0026] According to the invention, it is preferred that a temperature is monitored during resistance brazing, with process parameters of the resistance brazing being adjusted as needed based on the monitored temperature. The temperature can be monitored, for example, by a thermal imaging camera and / or by contact measurement. Monitoring the temperature is particularly advantageous during setup, start-up, or regular monitoring of the production of a winding head. Preferably, a working temperature at one hairpin end pair is monitored during the brazing process. More preferably, working temperatures at several hairpin end pairs are monitored and compared with one another during the brazing process. Temperature deviations between the working temperatures are preferably counteracted by targeted manipulation of the solder additive.If working temperatures are on average too high or too low, adjusting the current strength during resistance brazing can be a possible remedy. Furthermore, temperatures in isolated areas of the hairpins can also be monitored, for example, to evaluate the effectiveness of cooling or the risk of heat damage to the insulation and to implement countermeasures. The temperatures at the soldering electrodes can also be monitored, with temperature deviations between the soldering electrodes being able to be compensated for by specifically modifying one or both soldering electrodes. This allows process parameters for the manufacture of the engine component to be optimized, particularly for large-scale production. This has the advantage of further improving the quality of the engine component using simple and cost-effective means.

[0027] A method according to the invention for producing a winding head of a hairpin motor component for an electric motor for driving a motor vehicle is explained in more detail below with reference to the drawings. They show schematically: Fig. 1 shows a sectional view of an arrangement for producing a material-locking connection during the implementation of a preferred first embodiment of the method according to the invention, Fig. 2 shows a sectional view of an arrangement for producing a material-locking connection during the implementation of a preferred second embodiment of the method according to the invention, and Fig. 3 shows a flow chart of a preferred embodiment of a method according to the invention.

[0028] Elements with the same function and mode of action are listed in the Fig. 1 to 3 are each provided with the same reference numerals.

[0029] In Fig. 1 schematically shows a sectional view of an arrangement for creating a material-to-material connection during the implementation of a preferred first embodiment of the method according to the invention. Several hairpins 1 with electrical insulation 8 are shown, with hairpin ends 2 of the hairpins 1 not having electrical insulation 8. The hairpin ends 2 protrude in an axial direction A from base body slots (not shown) of a component base body (not shown) of a stator or rotor.

[0030] In the illustration, hairpin ends 2 of different hairpins 1 are combined to form hairpin end pairs 3. Furthermore, several hairpin end pairs 3 arranged next to one another in the radial direction R are held spaced apart from one another by spacers 6 and, together with the spacers 6, are clamped between two soldering electrodes 5. Between the hairpin ends 2 of the individual hairpin end pairs 3, a solder additive 4 in the form of a solder platelet with a specific solder additive thickness D is arranged. In this example, the solder plates protrude from the hairpin end pair 3 in the axial direction A.

[0031] Fig. 2 shows a schematic sectional view of an arrangement for creating a material-to-material connection during implementation of a preferred second embodiment of the method according to the invention. The preferred second embodiment differs from the preferred first embodiment in a configuration of the spacers 6. The spacers 6 extend further in the axial direction A along the hairpins 1 and now also contact the insulation 8. In a region directly adjacent to the insulation 8, the spacers 6 have a cooling device 7, by means of which the insulation 8 can be cooled during resistance brazing. In a central region, the spacers 6 additionally have thermal insulation 9 in order to reduce any influence of the cooling on the brazing process.

[0032] In Fig.3, a preferred embodiment of a method according to the invention is shown schematically in a flow diagram. In a first method step 100, a component base body with base body grooves is provided, in which hairpins 1 are arranged. The hairpin ends 2 of the hairpins 1 protrude from the component base body in the axial direction A. In a second method step 200, hairpin ends 2 to be connected to one another are combined to form hairpin end pairs 3. In this case, preferably several hairpin end pairs 3 are kept spaced apart from one another by spacers 6. A solder platelet is arranged between the hairpin ends 2 of the hairpin end pairs 3 as a solder additive 4. The hairpin end pairs 6 are also pressed together between two soldering electrodes 5. In a third method step 300, the soldering electrodes 5 are specifically energized so that the solder additive 4 is melted and the hairpin ends 2 of the hairpin end pairs 3 are each bonded to one another.After the current supply has ended, the solder additive 4 cools down and solidifies. List of reference symbols 1 hairpin 2 hairpin ends 3 pairs of hairpin ends 4 Solder additive 5 soldering electrode 6 spacers 7 Cooling device 8 electrical insulation 9 thermal insulation 100 first procedural action 200 second procedural action 300 third procedural action A axial direction D Additional solder thickness R radial direction QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2012 215 309 B4

[0005] DE 10 2006 019 312 A1

[0005]

Claims

[1] Method for producing a winding head of a hairpin motor component for an electric machine for driving a motor vehicle, comprising: - Providing a component base body with a longitudinal axis and a plurality of base body grooves extending along the longitudinal axis, wherein hairpins (1) are arranged in the base body grooves, wherein hairpin ends (2) of the hairpins (1) protrude from the base body grooves in the axial direction (A), - Targeted grouping of adjacent hairpin ends (2) into hairpin end pairs (3), - Materially connecting the hairpin ends (2) within the hairpin end pairs (3) to produce hairpin end pair connections, characterized by that the material connection of the hairpin ends (2) is carried out by resistance brazing. [2] Method according to claim 1, characterized bythat before the hairpin end pair composite is produced, a solder additive (4) is arranged directly between and / or on the front side between the adjacent hairpin ends (2) of the hairpin end pair (3). [3] Method according to claim 2, characterized by that a solder additive thickness (D) of the solder additive (4) and / or a solder additive material composition of the solder additive (4) is determined based on a required voltage drop at the respective solder additive (4). [4] Method according to one of the preceding claims, characterized by that the hairpin end pairs (3) are pressed together between two soldering electrodes (5) during resistance brazing. [5] Method according to one of the preceding claims, characterized by that several hairpin end pairs are generated simultaneously. [6] Method according to claim 5, characterized bythat an electrically conductive spacer (6) is arranged between adjacent hairpin end pairs (3) to simultaneously produce the hairpin end pair connections. [7] Method according to one of the preceding claims, characterized by that the hairpins (1) are cooled by a cooling device (7). [8] Method according to claims 6 and 7, characterized by that the spacers (6) are cooled directly by the cooling device (7). [9] Method according to one of the preceding claims, characterized by that soldering electrodes (5) are used for resistance brazing which have such different soldering electrode materials that the soldering electrodes (5) have no or only a tolerated temperature difference during resistance brazing. [10] Method according to one of the preceding claims, characterized bythat a temperature is monitored during resistance brazing, with resistance brazing process parameters being adjusted as needed based on the monitored temperature.

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