Clamping tool and method for clamping wire ends of a hairpin winding used in a stator of an electric machine

Abstract

The invention relates to a clamping tool (1) for clamping wire ends (2) of a hairpin winding (5) inserted in a stator (3) of an electric machine (4), wherein two of the wire ends (2) to be electrically connected to each other form a hairpin pair (21), wherein several hairpin pairs (21) are arranged equidistantly on several concentric circular tracks (22) or on sections of concentric circular tracks (22) in the circumferential direction (23), such that the hairpin pairs (21) are aligned along radially oriented rows (24) which are spaced apart from each other by radial gaps (26) extending in the radial direction (25), and the individual hairpin pairs (21) arranged in a radially oriented row (24) are spaced apart from each other in the radial direction (25) by annular gaps (26) extending between the concentrically arranged circular tracks (22). are, and wherein the clamping tool (1) has a linear actuator (6),by means of which the clamping tool (1) can perform a lifting movement relative to the wire ends (2), as well as a first clamping element (7) and a second clamping element (8), which are movable relative to each other in a tangential direction to the hairpin winding (5).

Description

The present invention relates to a clamping tool for clamping wire ends of a hairpin winding used in a stator of an electric machine, wherein in each case two of the wire ends to be connected to one another in an electrically conductive manner form a hairpin pair, wherein a plurality of hairpin pairs are arranged equidistantly in the circumferential direction on a plurality of circular paths arranged concentrically with one another or on portions of concentric circular paths, such that the hairpin pairs are aligned along radially oriented rows which are spaced apart circumferentially with respect to one another via radial gaps running in the radial direction and the individual hairpin pairs arranged in a radially oriented row are spaced apart in the radial direction with respect to one another via annular gaps running between the circular paths arranged concentrically with respect to one another, and wherein the clamping tool has a linear actuator by means of which the clamping tool can execute a stroke movement relative to the wire ends, and a first clamping element and a second clamping element, which are displaceable relative to one another in a tangential direction to the hairpin winding. The invention further relates to a method for bracing wire ends of a hairpin winding used in a stator of an electric machine.Electric motors are increasingly used for the drive in motor vehicles in order to create alternatives to internal combustion engines that require fossil fuels. In order to improve the suitability of electric drives for all days and in addition to be able to offer users the usual riding comfort, considerable efforts have already been made.In addition to the purely electrically operated drive trains, hybrid drive trains are also known. Drive trains of this type of a hybrid vehicle usually comprise a combination of an internal combustion engine and an electric motor, and make possible, for example in balling areas, a purely electric operating mode with a simultaneously sufficient range and availability, especially during cross country drives. In addition, it is possible to drive simultaneously by the internal combustion engine and the electric motor in certain operating situations.For the development of electric machines, in particular of electric machines for the above-mentioned hybrid or fully electrically operable motor vehicles or also for wheel hub drives, fundamentally different winding technologies for a stator of an electric machine are known.In electric machines which have a stator with a hollow cylindrical stator, that is to say are designed as an internal rotor machine and are configured for use as a traction drive of a motor vehicle, a stator winding with a rectangular cross section often has in order to achieve a high power density. In the case of electric machines which are provided for driving motor vehicles, the stator windings are therefore typically designed as hairpin windings. Here, for example, substantially U-shaped wire segments are introduced into the stator grooves from one end side of the stator and then formed on an opposite end side of the stator and connected, for example, by welding.The winding of the stator generally takes place in such a way that first the U-shaped hair pins are inserted into the predetermined slots of the stator. The wire ends project out of the grooves. After the insertion of the wires, their ends must be tensioned precisely in order to ensure a precise positioning for the contacting process. In this case, special clamping tools or devices are typically used to grip and position the wire ends. The wire ends are then brought into the correct position and tensioned with a defined force. This step requires high precision to ensure that the wire ends are exactly aligned and have the proper tension. After the wire ends are tensioned and aligned, they are often temporarily fixed to maintain their position during the following contacting process (e.g., welding or soldering). Subsequent to the clamping, the actual contacting process then takes place. In this case, the wire ends are usually soldered or welded in order to produce an electrical connection to the corresponding contact points.Since heat may be generated in a large amount in the thermal bonding (soldering or welding) methods, it is important to efficiently dissipate the heat in order to avoid damage to the stator or the windings. In order to protect the insulation of the wires from damage caused, for example, by laser radiation during welding, suitable coverings or protective measures must likewise be taken.The clamping thus ensures that the wire ends are accurately positioned to establish a correct and reliable connection with the contact points in the stator, which can also exert an influence on the electrical performance and efficiency of the motor. The correct tensioning also ensures that the wires are not subjected to excessive mechanical stresses during operation, which could lead to a fracture. Evenly tensioned wires eventually also contribute to a standardized, high manufacturing quality, which is especially important in mass production of electric motors.As already outlined at the beginning, a corresponding clamping tool is usually used for clamping the wire ends of the hairpine winding in order to precisely clamp and position the wire ends of the hairpine. The construction and function of such a tool may vary depending on the specific application and manufacturer, but there are some basic features and operations that are typical. Thus, a clamping tool generally has a mechanism, usually pliers or clamping devices, which can securely grip the wire ends. These devices are often designed to handle various wire diameters and shapes.Another important component is the positioning unit, which makes it possible to position the wire ends exactly. This unit may be manual, semi-automatic or fully automatic depending on the degree of automation in manufacturing. To tension the wire ends, elements are required for applying a precise force. These can be operated mechanically, pneumatically or electrically in order to ensure uniform tension.During the manufacturing process, the clamping tool then first grips the wire ends of the hair pins with its gripping mechanism and aligns the wire ends by means of the positioning unit such that they are positioned precisely for the contacting process. A defined tension is exerted on the wire ends by the force application elements. This voltage must be controlled precisely in order to avoid damage to the wires and at the same time to ensure a firm connection. After the contacting process (e.g., welding or soldering) is completed, the tool releases the wire ends without damaging them.The welding operation may be performed, for example, by a laser beam or by resistance heating to melt and thus bond the ends of the hair pins. The resulting connection point must have specific mechanical and electrical properties. A basic requirement for the joining operation is the accurate and repeatable positioning of the wire ends of the hairpin winding relative to each other and to the welding tool, such as the laser beam that must be directed at the wire ends of the hairpin winding to produce the joint by welding.WO 2018 / 185 620 A1 discloses an apparatus for aligning wire conductors comprising an alignment unit having a plurality of independently movable elements which hold the ends of the conductor pairs in the correct position during and after the alignment step in order to carry out the welding operation. The alignment unit may be configured for different configurations of the stators with different winding and size characteristics of the stator types. For each alignment step, several movements of the elements are necessary.Similar alignment units are known, for example, from JP 2017-98 161 A, U.S. Pat. No. 2022 / 0 069 679 A1 or DE 10 2018 107 598 A1, wherein U.S. Pat. No. 2022 / 0 069 679 A1 can be regarded as generic.The current state of the art in the field of clamping tools often has limited flexibility when adaptation to different product variants is concerned. The number of slots per stator and the number of wire ends vary widely, requiring a universal or modular clamping technique. While there are developments toward universal clamping techniques, they are often not sufficiently conformable to efficiently respond to the variety of product requirements. Another criticism is the time required for the setting up of the clamping devices. In a highly productive environment, such as the manufacture of electric motors, time is a critical factor. Existing technologies often require a considerable amount of time for the set-up, which impairs the efficiency of production. Although clamping accuracy is a critical aspect to ensure high quality final products, it often lacks the required precision in existing clamping techniques. Inaccurate tension may result in misalignments that affect the performance and reliability of the finished electric motors. Protecting the wire insulation from laser radiation during the welding process may present another challenge. The current technique may not always provide adequate solutions to effectively protect the insulation from the high energy of the laser beams.Overall, it has been found in the prior art that despite developments toward more universal clamping techniques, there is still a considerable need for improvements, in particular with regard to flexibility, efficiency and precision, in order to meet the diverse and demanding requirements in the production of electric motors.It is therefore the object of the invention to avoid or at least reduce the disadvantages known from the prior art and to provide an improved clamping tool. It is also the object of the invention to realize an optimized method for bracing wire ends of a hairpin winding used in a stator of an electric machine.This object is achieved by a clamping tool for clamping wire ends of a hairpin winding used in a stator of an electric machine, wherein in each case two of the wire ends to be connected to one another in an electrically conductive manner form a hairpin pair, wherein a plurality of hairpin pairs are arranged equidistantly on a plurality of circular paths arranged concentrically with respect to one another or on portions of concentric circular paths in the circumferential direction, such that the hairpin pairs are aligned along radially oriented rows which are spaced apart circumferentially with respect to one another via radial gaps running in the radial direction and the individual hairpin pairs arranged in a radially oriented row are spaced apart in the radial direction with respect to one another via annular gaps running between the circular paths arranged concentrically with respect to one another, and wherein the clamping tool has a linear actuator by means of which the clamping tool can execute a stroke movement relative to the wire ends, and a first clamping element and a second clamping element, which can be displaced relative to one another in the tangential direction to the hairpine winding, wherein the linear actuator is coupled to a U-shaped actuating element, which is mounted within the clamping tool so as to be linearly displaceable with respect to a slide element, wherein the actuating element has, on its free legs, ramps which drop in each case toward the free end of a leg and which can slide along correspondingly formed ramps on the slide element and cooperate in such a way that pressing the actuating element onto the slide element on its ramps generates a force component acting in the circumferential direction to the hairpine winding, and the slide element is formed in such a way that the force components produce an offset, generated in the circumferential direction to the hairpine winding, of a first connection section of the slide element, to which the first clamping element is fixed, and causing an offset, generated in the circumferential direction with respect to the hairpin winding, of a second connection section of the slide element, to which connection section the second clamping element is fixed, so that, when the actuating element is pressed against the slide element, the first clamping element and the second clamping element are moved toward one another in the circumferential direction and away from one another when the actuating element is released from the slide element.This achieves the advantage that the clamping tool for clamping wire ends of a hairpin winding enables reliable and precise clamping by virtue of the fact that it engages in a targeted manner the radial and annular gaps of the pairs of hairpins.The use of a linear actuator in combination with a U-shaped actuating element and a slide element with corresponding ramps ensures a uniform movement of the clamping elements, which movement is especially exactly controllable in the circumferential direction. These can thus securely grip and clamp the wire ends. The described mechanism enables efficient power transmission and intuitive operability of the tool, which may contribute to a reduction in assembly times and an increase in processing quality.The cleaning of the clamping tool has likewise proven to be a simple and uncomplicated process, since simple tools or keys can be used for removing the clamping elements. This contributes to a reduction of machine downtime and increases the efficiency of the entire manufacturing process. Moreover, the serviceability of the clamping tool is particularly advantageous since the clamping elements are simple and individually replaceable. This also allows rapid recovery of operational readiness in the event of element replacement and reduces the risk of longer downtime. Accordingly, no complicated operation is required even when the clamping tool is fitted. The replacement of the clamping elements can be carried out correspondingly quickly and without special tools, which entails a high flexibility with regard to the adaptability of the clamping tool to different hairpin designs. The good covering function of the clamping elements additionally contributes to the safety of the process in that it reliably protects the wire ends during the clamping and at the same time offers easy accessibility for downstream process steps. In addition, the direct controllability of the clamping force allows gap-free clamping of the pairs of hair pins, which contributes to efficient use of the clamping tool and to consistently high-quality connection results. The precise adjustability of the force additionally opens up the possibility of accessing the specific properties of the materials to be processed and thus adjusting the clamping process precisely to the requirements of the respective wire material.In the sense of this patent application, a clamping element is a mechanical component of the clamping tool, which is designed to fix and clamp wire ends of a hairpin winding of an electric machine. The clamping element is used to press the individual wire ends of a pair of hairpine against each other and to hold them in an exact position so that an electrically conductive connection can be established between them, typically by welding or soldering. A tension member functions as part of the tensioning process by allowing precise and stable alignment of the wire ends while applying the necessary forces to tension the wire ends in the desired position. It thus provides an optimum contact area and assists in establishing a high-quality and reliable connection of the hairpin wires. Furthermore, the clamping element can be designed such that it protects the wire ends from mechanical damage during the method. With regard to the materials, clamping elements can be manufactured from different materials, which are adapted to the specific requirements of the field of application. It is thus possible to produce clamping elements from hardened steel in order to ensure high strength and durability, in particular when they are exposed to high mechanical loads. Alternatively, the use of aluminum or other light metal alloys is conceivable to reduce the overall weight of the clamping tool, which facilitates handling and possibly improves the energy efficiency of automated production facilities. In addition, tension members may be provided with specific surface treatments or coatings to minimize friction and increase resistance to corrosive influences. The geometric configuration of the clamping elements can likewise vary. In addition to plate-like flat clamping elements, clamping elements with special profiles or recesses, such as grooves or windows, are also possible, which allow, for example, the passage during the welding process. These geometric configurations preferably also take account of possible thermal expansions of the wire ends and facilitate accessibility for welding electrodes and visual inspection of the welded connections.The actuating element is a component of the clamping tool which is in direct kinematic connection with the linear actuator and is used for moving the clamping elements. It is part of the mechanism which converts the lifting movement of the linear actuator into a tangential movement of the clamping elements relative to the wire ends of a hairpin winding. An essential function of the actuator is to accommodate the linear motion exerted by the linear actuator and convert it to produce a component of force acting in the circumferential direction of the hairpine winding. According to the invention, this is done by interaction with ramps on the slide element, which allow a tangential displacement of the clamping elements. As a result, the clamping elements are moved and released again for gripping the wire ends. According to the invention, the actuating element is U-shaped with descending ramps on the free legs, which slides along corresponding ramps on the slide element. This configuration enables efficient conversion of the lifting movement into a tangential displacement movement.A further component of the clamping tool is the slide element, which is in direct functional relationship with the actuating element and is responsible for the transmission of the force generated by the actuating element into a movement of the clamping elements. The slide element thus forms an interface between the actuating mechanism and the clamping elements and is essential for converting the linear actuator movement into a tangential movement required for clamping the wire ends. The slide element serves to absorb and guide the ramp movement of the actuating element and effectively transmit the tangential force component thereby arising to the clamping elements. By its specific construction, which has corresponding ramps for interaction with the actuator, the slider element translates the linearly moved force into a tangential movement, which is then taken up by the tension members to tighten or loosen the wire ends.The stator to be wound is intended for use in an electric machine. The electric machine serves for converting electrical energy into mechanical energy and / or vice versa, and it generally comprises the stationary part referred to as a stator, stator or armature and a part referred to as a rotor or rotor and arranged movably, in particular rotatably, with respect to the stationary part. In particular, the electric machine is dimensioned such that vehicle speeds greater than 50 km / h, preferably greater than 80 km / h and in particular greater than 100 km / h can be achieved. Particularly preferably, the electric motor has a power greater than 30 kW, preferably greater than 50 kW and in particular greater than 70 kW. It is furthermore preferred that the electric machine provides rotational speeds greater than 5,000 U / min, particularly preferably greater than 10,000 U / min, very particularly preferably greater than 12,500 U / min.The stator can be energized in particular by power electronics. The power electronics are preferably designed to control or regulate a power per phase with a peak power, preferably continuous power, of at least 10 W, preferably at least 100 W, particularly preferably at least 1000 W.Motor vehicles in the sense of this application are land vehicles which are moved by machine power without being bound to railway tracks. A motor vehicle can be selected, for example, from the group of passenger cars (passenger cars), trucks (trucks), small-size trucks, light-weight trucks, bicycles, buses (COM) or tractors.The stator to be wound can preferably be configured for a radial flux machine. The stator of a radial flux machine is usually cylindrical or has a ring-shaped cylindrical structure and generally consists of a stator body which is formed by electric sheets which are electrically insulated from one another and are of layered structure and are laminated to form laminated cores. As a result of this structure, the eddy currents in the stator caused by the stator field are kept low. Distributed over the circumference, stator grooves are let into the electric sheet, running parallel to the rotor shaft, which grooves accommodate the stator winding or parts of the stator winding. Depending on the design towards the surface, the grooves can be closed with closure elements, such as closure wedges or covers or the like, in order to prevent the stator winding from coming off.The stator body is preferably formed in one piece. A one-piece stator body is distinguished in that the entire stator body, viewed circumferentially, is formed in one piece. The stator body is generally formed from a multiplicity of stacked laminated electric sheets, each of the electric sheets being formed closed to form a circular ring. The individual laminations can be held together in the stator body, for example, by adhesion, welding or screwing.The stator teeth of the stator are preferably formed in the stator body. Stator teeth are components of the stator body which are formed as circumferentially spaced-apart parts of the stator body which are directed radially inward (inner rotor) or radially outward (outer rotor) in a toothed manner and between the free ends of the stator body and a rotor body an air gap for the magnetic field and for the rotational movement of the rotor is formed. The air gap is the nonmagnetic gap existing between the rotor and the stator. In a radial flux machine, this is, for example, a substantially circular ring-shaped gap having a radial width which corresponds to the distance between the rotor body and the stator body.The hairpin winding is inserted into the stator slots of the stator.According to an advantageous embodiment of the invention, it can be provided that the ramps of the actuating element and the corresponding ramps of the slide element are configured to be angled such that the first clamping element and the second clamping element are movable not only toward and away from one another in the circumferential direction, but also in the radial direction. This results in improved adaptability of the clamping tool to different sizes of hairpin coils and helps to provide universal utility of the tool. The increased flexibility in the bracing of differently designed pairs of hair pins thus contributes to a cost reduction, since no change of the tool is necessary for different hair pins designs. The radially and tangentially movable clamping elements also permit exact alignment of the pairs of hair pins in two spatial directions, which ensures a constantly high quality of the clamped windings.According to a further preferred development of the invention, it can also be provided that the clamping tool has at least one spring element which exerts a spring force on the clamping elements acting counter to the closing direction of the clamping elements. The presence of at least one spring element, which exerts a spring force on the clamping elements counter to the closure direction, promotes automatic opening of the clamping elements after the clamping has ended. This not only increases efficiency and user-friendliness, but also safety of the operation, since the clamping elements can automatically move back into a safe rest position.Furthermore, according to a likewise advantageous embodiment of the invention, it can be provided that the first clamping element and the second clamping element are arranged offset in the axial direction relative to the hairpin winding and overlap in the circumferential direction at least in the closed position of the clamping elements. This offers the advantage that the wire ends are held securely during the tensioning even in the case of movements or positioning inaccuracies and the risk of the wire ends slipping is thereby reduced.According to a further particularly preferred embodiment of the invention, it can be provided that the first clamping element and / or the second clamping element is / are designed in the manner of a plate. It is thus possible, for example, to form the clamping elements by means of forming methods, for example from a sheet metal, which is particularly cost-effective and clamping elements can thus also be produced in large numbers and in a wide variety of plate-like configurations.Furthermore, the invention can also be further developed in that the first clamping element has, for each pair of hair pins to be braced, a circumferential clamping surface extending in the radial direction, against which the pairs of hair pins abut with a first circumferential side in the closed position of the clamping elements, and the second clamping element has, for each pair of hair pins to be braced, a circumferential clamping surface extending in the radial direction, against which the pairs of hair pins abut with a second circumferential side in the closed position of the clamping elements. By providing specially designed circumferential clamping surfaces for each pair of hair pins, a firm and secure fit of the wire ends is ensured, which improves the connection reliability. The specific alignment of these surfaces enables an effective transmission of the clamping forces and thus facilitates the subsequent connection method, for example by welding.In a likewise preferred embodiment variant of the invention, it can also be provided that the first clamping element has a radial clamping surface extending in the circumferential direction for each pair of hair pins to be braced, on which surface the pairs of hair pins abut with a first radial side in the closed position of the clamping elements, and the second clamping element has a radial clamping surface extending in the circumferential direction for each pair of hair pins to be braced, on which surface the pairs of hair pins abut with a second radial side in the closed position of the clamping elements. In this case, the clamping tool offers the advantage that an additional clamping dimension is created by radially oriented clamping surfaces, which further stabilizes the positioning of the wire ends and thus further increases the connection reliability.It can also be advantageous to further develop the invention to the effect that the first clamping element has at least one first window and the second clamping element has at least one first window, which can each be penetrated by the same pair of hair pins. Particularly large clamping forces can be transmitted by the window construction, since the clamping elements have particularly high structural integrity due to the closed circumferential contour of the windows.According to a further preferred embodiment of the subject matter of the invention, it can be provided that the linear actuator comprises a piston which is displaceable relative to a housing of the clamping tool and is connected to a slide which is displaceable in the housing and which in turn is coupled to the clamping elements via the actuating element and the slide element, such that displacement of the piston relative to the housing brings about a stroke movement of the clamping elements relative to the wire ends of the hairpin winding, wherein the slide, in its movement towards the wire ends of the hairpin winding, runs against a mechanical stop, but the piston continues to execute a stroke movement in the direction of the wire ends and thus can press the actuating element against the slide element and thereby transfer the clamping elements into their closed position. The configuration of the linear actuator with a piston and a slide coupled via actuating and slide elements allows a clean mechanical or kinematic separation of stroke movement and clamping action. This leads to increased precision during the clamping process and to robustness with respect to disturbances due to the lifting movement. Because both the lifting movement and the transfer of the clamping elements into their closed position only one linear actuator or one piston is necessary, the corresponding mechanism or actuator system can be designed particularly cost-effectively.Finally, the object of the invention can also be achieved by a method for bracing wire ends of a hairpin winding inserted in a stator of an electric machine by means of a clamping tool according to one of Claims 1-9, comprising the following steps:• positioning the first tension member and the second tension member above the wire ends of the hairpin winding;• Actuation of the linear actuator so that the tension elements engage between the pairs of hair pins of the wire ends;• Pressing the actuating element against the slide element, so that the clamping elements engaging between the pairs of hair pins are transferred into their closed position.The claimed method for tensioning wire ends offers a structured sequence which enables a quick and secure tensioning of the wire ends. It contributes to process safety and time saving, since the individual steps are clearly defined and matched to one another. The locking position of the clamping elements is precisely achieved, which ensures a high quality of the clamping result.The invention will be explained in more detail below with reference to figures without limiting the general concept of the invention.It shows: FIG. 1 shows a clamping tool with a stator wound with a hairpin winding in a perspective view, FIG. 2 shows a clamping tool with a stator wound with a hairpin winding in a plan view, FIG. 3 shows a slide element with clamping elements encompassing the ends of the hairpine winding in a perspective detailed view, FIG. 4 shows a first embodiment of clamping elements in a position encompassing the pairs of hair pins in a plan view, FIG. 5 shows a first embodiment of clamping elements in a position clamping the pairs of hair pins in a plan view, FIG. 6 shows a second embodiment of clamping elements in a position encompassing the pairs of hair pins in a plan view, FIG. 7 shows a second embodiment of clamping elements in a position clamping the pairs of hair pins in a plan view, FIG. 8 shows a first embodiment of a first clamping element in a perspective view, FIG. 9 shows a first embodiment of a second clamping element in a perspective view, FIG. 10 is a perspective view of the slide member, FIG. 11 is a perspective view of the actuating element, FIG. 12 shows a clamping tool in two different longitudinal sectional views.FIGS. 1-2 show a clamping tool 1 for clamping wire ends 2 of a hairpin winding 5 inserted in a stator 3 of an electric machine in various views. The clamping tool 1 has a linear actuator 6, by means of which the clamping tool 1 can execute a stroke movement relative to the wire ends 2, which will be discussed in more detail later.Firstly, a possible configuration of a hairpin winding 5 to be braced is explained in more detail by way of example with reference to FIG. 4. It can be seen clearly that in the exemplary embodiment shown, in each case two of the wire ends 2 to be connected to one another in an electrically conductive manner form a pair of hair pins 21, wherein two pairs of hair pins 21 are arranged equidistantly on two circular paths 22 arranged concentrically with respect to one another or on sections of concentric circular paths 22 in the circumferential direction 23, such that the pairs of hair pins 21 are aligned along radially oriented rows 24 which are spaced apart circumferentially with respect to one another on the one hand via radial gaps 26 running in the radial direction 25. On the other hand, the individual pairs of hairpines 21 arranged in a radially oriented row 24 are spaced apart from one another in the radial direction 25 via an annular gap 27 running between the circular paths 22 arranged concentrically with respect to one another.As can be easily seen, for example, from the overview of FIGS. 3-5, the clamping tool 1 has a first clamping element 7 and a second clamping element 8, which can be displaced relative to one another in the tangential direction to the hairpin winding 5. In order to enable this movement, the linear actuator 6 is coupled to a U-shaped actuating element 9 which is mounted within the clamping tool 1 so as to be linearly displaceable with respect to a slide element 10, wherein the actuating element 9 has, on its free legs 11, ramps 13 which drop in each case toward the free end 12 of a leg 11 and which can slide along correspondingly formed ramps 14 on the slide element 10 and cooperate in such a way that pressing of the actuating element 9 onto the slide element 10 on its ramps 14 in each case generates a force component which acts in the circumferential direction 23 with respect to the hairpin winding 5. This cooperation can be easily understood from the overview of FIGS. 10-12.The slide element 10 is now designed such that the force components cause an offset, generated in the circumferential direction 23 with respect to the hairpin winding 5, of a first connection section 16 of the slide element 10, to which the first clamping element 7 is fixed, and an offset, generated in the circumferential direction 23 with respect to the hairpin winding 5, of a second connection section 17 of the slide element 10, to which the second clamping element 8 is fixed, such that, when the actuating element 9 is pressed against the slide element 10, the first clamping element 7 and the second clamping element 8 are moved toward one another in the circumferential direction 23 and, when the actuating element 9 is released from the slide element 10, away from one another, which can be seen in FIGS. 4-7.It can be seen from FIG. 10 that the ramps 13 of the actuating element 9 and the corresponding ramps 14 of the slide element 10 are configured to be angled such that the first clamping element 7 and the second clamping element 8 are movable not only toward one another and away from one another in the circumferential direction 23, but also in the radial direction 25 This produced kinematics can also be seen from the comparison of FIG. 4 with FIG. 5 and FIG. 6 with FIG. 7. The slide element 10 has a gap 20 which runs approximately centrally and through its longitudinal extent and simplifies the compression of the slide element 10 in the circumferential direction.The actuating element 9 can be seen in detail in FIG. 11. The opening 19 for the passage of the slide 28 is also visible, by means of which the slide element 10 is displaced with respect to the actuating element 9.The clamping tool 1 has at least one spring element (which is not shown in the figures) which exerts a spring force on the clamping elements 7, 8 acting counter to the closing direction of the latter.As shown in FIG. 3, the first clamping element 7 and the second clamping element 8 are arranged offset in the axial direction relative to the hairpine winding 5 and overlap radially and circumferential direction 23 at least in the closed position of the clamping elements 7, 8. The figures show embodiments in which the first clamping element 7 and the second clamping element 8 are plate-like.It can be seen by means of FIGS. 5 and 7 that the first clamping element 7 has, for each pair of hair pins 21 to be clamped, a circumferential clamping surface 30 extending in the radial direction 25, on which the pairs of hair pins 21 bear with a first circumferential side 31 in the closed position of the clamping elements 7, 8. Analogously, the second clamping element 8 also has, for each pair of hair pins 21 to be braced, a circumferential clamping surface 32 extending in the radial direction 25, against which the pairs of hair pins 21 abut with a second circumferential side 33 in the closed position of the clamping elements 7, 8. Furthermore, the first clamping element 7 has, for each pair of hair pins 21 to be braced, a radial clamping surface 34 extending in the circumferential direction 23, against which the pairs of hair pins 21 abut with a first radial side 39 in the closed position of the clamping elements 7, 8. Likewise, the second clamping element 8 also has, for each pair of hair pins 21 to be braced, a radial clamping surface 35 extending in the circumferential direction 23, against which the pairs of hair pins 21 abut with a second radial side 36 in the closed position of the clamping elements 7, 8. By means of this configuration, a scissors-like cutting movement can now be carried out between the included pairs of hair pins 21 by means of the clamping elements 7, 8, in which the clamping elements 7, 8 are moved towards one another in the circumferential direction 23 and also in the radial direction 25 and in the process clamp the pairs of hair pins 21.In a first embodiment of the clamping elements 7, 8, which can be seen particularly well in FIGS. 8-9, the first clamping element 7 has at least one first window 37 and the second clamping element 7 has a first window 38, which can each be penetrated by the same pair of hair pins 21, as is also shown in FIGS. 4-5.The actuator system of the clamping tool 1 can be explained and reproduced easily on the basis of FIG. 12. The linear actuator 6 comprises a piston 41 which is displaceable relative to a housing 40 of the clamping tool 1 and is connected to a slide 42 which is displaceable in the housing 40 and which in turn is coupled to the clamping elements 7, 8 via the actuating element 9 and the slide element 10, so that displacement of the piston 41 relative to the housing 40 brings about a lifting movement of the clamping elements 7, 8 relative to the wire ends 2 of the hairpine winding 5. The slide 42 moves towards the wire ends 2 of the hairpine winding 5 against a mechanical stop 43 and is secured in this operating position against a further lifting movement in the direction of the wire ends 2. However, the piston 41 can continue to execute a stroke movement in the direction of the wire ends 2 and thus press the actuating element 9 against the slide element 10 via a slide 28 and thereby transfer the clamping elements 7, 8 into their closed position, wherein the axial position of the clamping elements 7, 8 remains unchanged by the stop 43.The method for bracing the wire ends 2 of the hairpin winding 5 inserted in the stator 3 of the electric machine by means of the clamping tool 1 known from FIGS. 1-12 can thus comprise the following steps. First, the first clamping element 7 and the second clamping element 8 are positioned above the wire ends 2 of the hairpin winding 5. In this operating position, the actuation element 9 is then pressed against the slide element 10, so that the clamping elements 7, 8 engaging between the pairs of hair pins 21 are transferred into their closed position.In the basic position, the clamping elements 7, 8, i.e. above the wire ends 2, are positioned and are in an open state, as can be seen in FIGS. 4 and 6. During operation, the downward movement of the piston 41 of the linear actuator 6 then causes the carriage 42 to move downward, towards the hairpine winding 5, and to lower the clamping elements 7, 8 accordingly. The wire ends 2 of a row 24 of the hairpine winding 5 then enter, for example, into opening windows 37, 38 of the clamping elements 7, 8, as can be seen in FIG. 4. The downward movement of the carriage 42 is stopped by a fixed stop 43, which exactly defines the clamping height. As the piston 41 continues to move, it drives the slide 28 and the actuator 9 further downwardly. This leads via the ramps 14 on the slide element 10 to the clamping elements 7, 8 approaching one another, so that they close and securely grip the wire ends 2 between them. This operating state, which is also referred to as bracing, is shown in FIG. 5 and FIG. 7. After the clamping, the piston 41 is moved open, the slide element 10 then being pushed apart again, which results in the opening of the clamping elements 7, 8. By a further upward movement of the piston 41, the slide 42 thus comes back into its original position, the clamping elements 7, 8 then coming to stand again above the wire ends 2. This step makes it possible to continue the stator 3 for the next clock operation.Thanks to the angled arrangement of the ramps 13 on the actuating element 9 and the corresponding ramps 14 on the slide element 10, the clamping elements 7, 8 simultaneously move both radially and tangentially to the stator 3 during the closing process. When the clamping elements 7, 8 are opened, a relatively large window is thus formed, which allows simple catching of the wire ends.The invention is not limited to the embodiments shown in the figures. The foregoing description is, therefore, not to be considered as limiting, but illustrative. The following claims should be understood to mean that a said feature is present in at least one embodiment of the invention. This does not exclude the presence of further features. If the patent claims and the above description define "first" and "second" features, this designation serves to distinguish two features of the same type without specifying a ranking.List of reference characters1 Clamping tool 2 Wire ends 3 Stator 5 Hairpin winding 6 Linear actuator 7 Clamping element 8 Clamping element 9 Actuating element 10 Slide element 11 Limbs 12 End 13 Ramps 14 Ramps 16 Connecting portion 17 Connecting portion 19 Opening 20 Gap 21 Hairpin pair 22 Circular paths 23 Circumferential direction 24 Rows 25 Radial direction 26 Radial gap 27 Annular gaps 28 Slides 30 Circumferential clamping surface 31 Circumferential side 32 Circumferential clamping surface 33 Circumferential side 34 Radial clamping surface 35 Radial clamping surface 36 Radial side 37 Window 38 Window 39 Radial side 40 Housing 41 Piston 42 Slide 43 Stop

Claims

Clamping tool (1) for clamping wire ends (2) of a hairpin winding (5) used in a stator (3) of an electric machine, wherein in each case two of the wire ends (2) to be connected to one another in an electrically conductive manner form a hairpin pair (21), wherein a plurality of hairpin pairs (21) are arranged equidistantly in the circumferential direction (23) on a plurality of circular paths (22) arranged concentrically with respect to one another or on sections of concentric circular paths (22), such that the hairpin pairs (21) are aligned along radially oriented rows (24), the circumferentially spaced apart from one another via radial gaps (26) running in the radial direction (25), and the individual hairpin pairs (21) arranged in a radially oriented row (24) are spaced apart from one another in the radial direction (25) via annular gaps (27) running between the circular paths (22) arranged concentrically with respect to one another, and wherein the clamping tool (1) has a linear actuator (6) by means of which the clamping tool (1) can execute a stroke movement relative to the wire ends (2), and a first clamping element (7) and a second clamping element (8) which can be displaced relative to one another in the tangential direction to the hairpin winding (5), characterized in that the linear actuator (6) is coupled to a U-shaped actuating element (9) which is mounted within the clamping tool (1) in a linearly displaceable manner with respect to a slide element (10), wherein the actuating element (9) has, on its free legs (11), ramps (13) which drop in each case toward the free end (12) of a leg (11) and which can slide along correspondingly formed ramps (14) on the slide element (10) and thus cooperate, a pressing of the actuating element (9) against the slide element (10) on its ramps (14) generates a force component acting in the circumferential direction (23) toward the hairpin winding (5), and the slide element (10) is designed such that the force components cause an offset, generated in the circumferential direction (23) toward the hairpin winding (5), of a first connection section (16) of the slide element (10), to which the first clamping element (7) is fixed, and an offset, generated in the circumferential direction (23) toward the hairpin winding (5), of a second connection section (17) of the slide element (10), to which the second clamping element (8) is fixed, so that when the actuating element (9) is pressed against the slide element (10), the first clamping element (7) and the second clamping element (8) are moved towards each other in the circumferential direction (23) and away from each other when the actuating element (9) is released from the slide element (10).Clamping tool (1) according to claim 1, characterised in that the ramps (13) of the actuating element (9) and the corresponding ramps (14) of the slide element (10) are configured to be angled such that the first clamping element (7) and the second clamping element (8) are movable not only towards one another and away from one another in the circumferential direction (23), but also in the radial direction (25).Clamping tool (1) according to one of the preceding claims, characterized in that the clamping tool (1) has at least one spring element which exerts a spring force on the clamping elements (7, 8) acting counter to the closure direction of the clamping elements.Clamping tool (1) according to one of the preceding claims, characterized in that the first clamping element (7) and the second clamping element (8) are arranged offset in the axial direction relative to the hairpine winding (5) and overlap in the circumferential direction (23) at least in the closed position of the clamping elements (7, 8).Clamping tool (1) according to one of the preceding claims, characterized in that the first clamping element (7) and / or the second clamping element (8) are / is designed in the form of a plate.Clamping tool (1) according to one of the preceding claims, characterized in that the first clamping element (7) has, for each pair of hair pins (21) to be clamped, a circumferential clamping surface (30) which extends in the radial direction (25) and against which the pairs of hair pins (21) bear with a first circumferential side (31) in the closed position of the clamping elements (7, 8), and the second clamping element (8) has, for each pair of hair pins (21) to be clamped, a circumferential clamping surface (32) which extends in the radial direction (25) and against which the pairs of hair pins (21) bear with a second circumferential side (33) in the closed position of the clamping elements (7, 8).Clamping tool (1) according to one of the preceding claims, characterized in that the first clamping element (7) has, for each pair of hair pins (21) to be clamped, a radial clamping surface (34) which extends in the circumferential direction (23) and against which the pairs of hair pins (21) bear with a first radial side (39) in the closed position of the clamping elements (7, 8), and the second clamping element (8) has, for each pair of hair pins (21) to be clamped, a radial clamping surface (35) which extends in the circumferential direction (23) and against which the pairs of hair pins (21) bear with a second radial side (36) in the closed position of the clamping elements (7, 8).Clamping tool (1) according to one of the preceding claims, characterized in that the first clamping element (7) has at least one first window (37) and the second clamping element (7) has at least one first window (38), which can each be penetrated by the same pair of hair pins (21).Clamping tool (1) according to one of the preceding claims, characterized in that the linear actuator (6) comprises a piston (41) which is displaceable with respect to a housing (40) of the clamping tool (1) and is connected to a slide (42) which is displaceable in the housing (40) and which in turn is coupled to the clamping elements (7, 8) via the actuating element (9) and the slide element (10), such that displacement of the piston (41) with respect to the housing (40) brings about a lifting movement of the clamping elements (7, 8) with respect to the wire ends (2) of the hairpine winding (5), wherein the slide (42), in its movement towards the wire ends (2) of the hairpine winding (5), runs against a mechanical stop (43), However, the piston (41) continues to execute a stroke movement in the direction of the wire ends (2) and thus presses the actuating element (9) against the slide element (10) and can thereby transfer the clamping elements (7, 8) into their closed position.Method for bracing wire ends (2) of a hairpin winding (5) inserted in a stator (3) of an electric machine by means of a clamping tool (1) according to one of the preceding claims, comprising the following steps: • positioning the first clamping element (7) and the second clamping element (8) above the wire ends (2) of the hairpin winding (5); • actuating the linear actuator (6) such that the clamping elements (7, 8) engage between the pairs of hair pins (21) of the wire ends (2); • pressing the actuating element (9) against the slide element (10) such that the clamping elements (7, 8) engaging between the pairs of hair pins (21) are transferred into their closed position.

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