Device for widening axial ends of insulating papers in stator slots of electrical machines

Abstract

Device for expanding axial ends of insulating papers (30) inserted into stator slots (21) of a stator lamination stack (20) of an electric machine, wherein the device has at least one application head (10) with a press punch (12), and wherein the press punch (12) has a shoulder region (14) which is designed such that, after a previously defined travel path of the application head (10) in the axial direction of the slot (21), a portion (31) of the slot insulating paper (30) which protrudes axially from this slot (21) can be expanded in the radial and / or circumferential direction, characterized in that at least one nozzle (13) is provided for blowing out a gaseous medium and is oriented in relation to the press punch (12) such that the gaseous medium can flow substantially in the axial direction in this slot (21).

Description

[0001] The invention relates to a device for widening axial ends of slot insulation papers inserted into stator slots of a stator lamination stack of an electric machine, having the features of the preamble according to claim 1.

[0002] Electric machines are used to convert electrical energy into mechanical energy (motor) or vice versa (generator). Electric motors with so-called hairpin windings are frequently used, particularly as drive motors for motor vehicles. To insulate the windings from the metallic stator core, an insulating paper (a multilayer material resembling paper only in appearance, including insulating film) is inserted into each stator slot. After these slot insulating papers are inserted into the slots, their protruding ends must be secured to prevent the papers from slipping out of position during further stator assembly, such as when inserting the hairpin conductor bars or during stator transport.It is known that the protruding ends of the slot insulation papers are mechanically deformed – also called "tufting" or "tufting" – so that the ends are bent radially outwards and fit snugly against the slot edges. This mechanical widening of the insulation papers at the axial slot exit serves, on the one hand, to reliably prevent subsequent axial displacement of the papers within the slot. On the other hand, it creates a funnel-shaped opening, which significantly facilitates the insertion of rigid winding wires, such as hairpin conductors, into the slots, as the conductor ends can slide more easily into the widened opening of the slot insulation papers.

[0003] In industrial practice, the crimping of the slot insulation papers is carried out either simultaneously from both ends of the stator lamination stack, or sequentially from each side, or possibly only from one side. However, each of these known methods has its drawbacks. When both ends of the insulation paper are simultaneously crimped in opposite directions, it is practically impossible to precisely synchronize the force and displacement applied to both sides. Even slight asynchronies cause the paper to slip in the slot, and this movement impairs or prevents controlled crimping. When crimping from both sides sequentially, the opposite side of the paper cannot be effectively supported in the second step because it has already been plastically deformed by the first crimping process and has therefore become unstable in the axial direction. Secure fixation of the insulation papers is thus not guaranteed.

[0004] This problem is exacerbated by the increasing trend towards using ever thinner insulating materials. Reduced material thickness leads to decreased stiffness of the insulating paper, making it more susceptible to bending under pressure in the groove. Thin groove insulating papers are therefore particularly prone to folding inwards under pressure or creasing against the groove wall, instead of curling open as desired. In the worst-case scenario, this completely prevents the insulation from curling open.

[0005] To mitigate the described difficulties, various approaches were tested in the prior art. Typically, the paper is joined in the same direction as the individual layers of the stack were die-cut. However, the hairpins are joined precisely in the opposite direction to the die-cutting, i.e., also opposite to the die-cutting edges. The paper is supported against the groove-wall ridges of the individual axial stator laminations of the stator stack and does not lose its position relative to the stator. Furthermore, there are papers on the market that are equipped with a sliding coating on the wire side. Variations in the die geometry and special surface treatments of the dies were also tested to improve the tufting process. Even thermal stress during the pressing process was considered. However, none of these measures could completely eliminate the risk of the groove insulation slipping during pressing.

[0006] No technical teaching is currently known that achieves reliable fixation of the slot insulation papers during the tufting process. In particular, no solution to the problem described above has emerged from the patent literature. DE 100 18 140 A1 describes a device and a method for manufacturing a stator, but does not disclose any specific measure to reliably prevent axial displacement of the slot insulation papers during expansion. Therefore, there is a need for an improved device that makes the tufting of the slot insulation papers effective and process-reliable.

[0007] The object of the invention is to provide a device with which axial slippage or buckling of the insulation papers is reliably prevented when the insulation papers are expanded.

[0008] The problem is solved by a device for expanding axial ends of insulating papers inserted into stator slots of a stator lamination stack of an electric machine, wherein the device has at least one application head with a press punch, and wherein the press punch has a shoulder area which is designed such that, after a previously defined travel distance of the application head in the axial direction of the slot, a portion of the slot insulating paper which protrudes axially from this slot can be expanded in the radial and / or circumferential direction, wherein, in addition, at least one nozzle for blowing out a gaseous medium is provided and is aligned with respect to the press punch such that the gaseous medium can flow substantially in the axial direction in this slot.

[0009] The combination of the aforementioned features achieves a completely novel effect. During the expansion process, a gaseous medium, preferably air, can be injected into the stator groove via the nozzle, pressing and stabilizing the groove insulation paper against the groove walls. This reliably prevents lateral displacement of the paper within the groove and the associated buckling – especially with very thin insulation paper. The groove insulation paper remains securely in position while the press ram expands the axially protruding ends from the outside. Even a slight overpressure is sufficient, thanks to the comparatively large effective area in the groove, to generate a sufficiently high frictional force between the paper and the groove wall, counteracting the mechanical pressing force of the ram.Even small leaks in the device hardly affect the effectiveness of this air support, so that the fixing of the slot insulation papers is secure and reproducible.

[0010] Particularly preferred is the provision that at least one nozzle is an integral part of the press ram and is provided as at least one outlet on a pin extending on the press ram in the direction of travel and capable of being inserted into the stator slots, wherein the outlet is arranged on the surface of the pin in such a way that the gaseous medium can flow in the stator slot.

[0011] This design further optimizes the effect described above. The nozzle is integrated directly into the press ram, so the airflow is introduced immediately at the point of action – namely, within the volume enclosed by the insulating paper inserted into the respective groove. This creates counter-pressure in the groove precisely where the insulating paper could shift during mechanical expansion. The pressure exerted by the predominantly thinner paper presses it against the inner wall of the groove, increasing the friction between the paper and the sheet metal core. Axial displacement of the paper is reliably prevented, and buckling – especially with thin-walled insulating papers – is avoided. Overall, integrating the nozzle into the press ram allows for a very compact design and precise airflow control.

[0012] It is also preferred that the at least one nozzle is designed as an outlet on the end face of the pin. In this advantageous embodiment, the gas outlet is located on the end face of the pin. This allows the airflow to begin shortly before or at the moment when the pin penetrates the axially projecting insulating paper. The insulating paper is thus immediately pressed outwards and stabilized, even as the pin penetrates the groove insulation. This ensures particularly secure insertion of the pin without any snagging on the inwardly inclined edges of the paper end.

[0013] In a further alternative embodiment, a support device is provided which, when the stator lamination stack is located between it and the application head, acts in its direction of action opposite to the travel path of the press ram, and wherein this support device comprises at least one nozzle which is arranged so that the gaseous medium can be blown into the stator groove.

[0014] This measure accommodates different implementation scenarios. If the expansion of the slot insulation papers is to occur only from one side of the stator (one-sided compression), a support device can be installed on the opposite side of the stator lamination stack, through which an airflow can also be blown into the slot. In this way, the inventive effect – fixing the slot insulation by gas pressure – can also be utilized even if the press ram expands the paper only from one end face. In this case, the counter-ram support prevents the paper from shifting on the open side, while its integrated nozzle additionally presses the insulation papers against the slot wall. The nozzle cross-section of the support device can, if necessary, be dimensioned larger than would be possible with the given dimensions of the press ram.

[0015] It may also be preferred that the device comprises two application heads arranged such that one of the application heads can be moved in opposite directions into one of the slots on one of the two axial sides of the stator lamination stack, and wherein at least one of the two application heads comprises at least one nozzle for venting the gaseous medium.

[0016] This enables symmetrical, double-sided processing of the stator. If the slot insulation papers are mechanically expanded from both sides simultaneously using two opposing application heads, this design ensures that a gas flow is introduced into the respective slot via at least one of the two application heads. Thus, the advantages of the air support according to the invention are not lost even with simultaneous, double-sided crimping – one head or even both can be equipped with the described nozzle assembly. Furthermore, the use of two application heads allows for an overall shorter process time, since both slot ends are expanded and fixed in parallel.

[0017] Furthermore, it is particularly advantageous that a temperature control device is provided, allowing the gaseous medium flowing through the at least one nozzle to be brought to different operating temperatures. This further development opens up the possibility of preheating or cooling the gas introduced into the groove to achieve additional effects. For example, by blowing in heated air, a thermal pre-fixation of the groove insulation papers can be achieved: The warm gas heats the insulation paper, or an additionally introduced heat-activated adhesive, as it is blown in, causing it to plasticize slightly and, in its expanded form, adhere to the groove wall as soon as it cools. This can further improve mechanical stabilization and thermal transfer. Conversely, the paper could be quickly stiffened by using cooled air.The temperature control device therefore makes it possible to adapt the injection medium to different requirements or process steps and to optimize the fixing effect and the thermal transfer.

[0018] Another preferred embodiment provides that a device for covering a radial opening of the respective groove of the stator lamination stack inserted into the device is also provided on the application head and / or the support device and / or as a separate device. This makes the invention applicable to stators with open grooves as well. Open groove geometries with U-shaped groove insulation papers can also benefit from the described effect by covering the groove opening in this way. By temporarily closing the open groove during the expansion process, the injected gas remains reliably within the groove area and presses the insulation paper against the groove walls. Otherwise, the gas medium would escape largely unhindered in open grooves and would not build up sufficient support pressure. The covering device (or a correspondingly designed component of the application head or support device)The support device thus acts as a seal for the groove openings. In addition, the cover device can also have one or more nozzles through which the gaseous medium can be introduced.

[0019] Preferably, several application heads are arranged so that insulating papers in two or more slots can be expanded simultaneously. This leads to a significant increase in process efficiency. If several slots are processed in parallel, their insulating papers can also be mechanically expanded and stabilized by gas pressure at the same time. This reduces the time required to process a stator. Particularly in automated production lines, such parallelization allows the cycle rate to be increased. For example, several application heads can be grouped radially around a stator and actuated synchronously to simultaneously bend and clamp a large number of slot insulating papers. This simultaneous processing of multiple slots not only improves throughput but also ensures a uniform result, since all processed slot insulating papers are subjected to the same process conditions.

[0020] Furthermore, the gaseous medium can be air. Air is a particularly advantageous gaseous medium for the device according to the invention. Air is readily available everywhere in sufficient quantities, is inexpensive, requires no special storage, and is not subject to any special safety requirements, especially regarding ESH requirements. It is also non-flammable and does not chemically react with conventional insulating materials or metal parts of the stator, thus enabling safe operation. Of course, the invention is not limited to air; in principle, other gases or gas mixtures can also be used, provided they have similar physical properties (pressure build-up, compatibility, etc.).

[0021] Furthermore, the design stipulates that at least one application head must have a base body and an inlet for the gaseous medium. This facilitates the technically advantageous supply of gas to the application head. The application head has a base body (usually made of metal) with an integrated inlet. The gaseous medium – for example, from an external compressed air source – can be fed directly into the application head via this inlet. From there, the gas flows through internal channels to the nozzle described above. This design allows for a compact application head and simplifies connection to a gas supply. Moreover, the inlet enables precise control of the medium's flow rate and pressure, allowing for optimal adaptation to the specific requirements of the expansion process.

[0022] The invention is explained in more detail using the figures as examples. They are shown schematically and not to scale: Fig. 1 schematically an application head of the device according to the invention Fig. 2. In perspective, an insulating paper widened by such an application head.

[0023] In Fig. Figure 1 shows an embodiment of the device according to the invention. An application head 10 with a press punch 12 provided thereon is oriented such that it can be moved axially into a stator slot 21 of a stator lamination stack 20. The press punch 12 has a pin 15 which forms a shoulder region 14 at its transition to the base body 11 of the application head 10. When the pin 15 is inserted into a slot, the shoulder region 14 meets an end 31 of insulating paper that projects axially from the slot. By further engaging the press punch 12 towards the slot, this protruding section of the insulating paper 31 is expanded outwards by the shoulder region 14. Simultaneously, a gaseous medium is blown axially into the slot 21 via a nozzle 13.In the illustrated example, the nozzle 13 is designed as an integral part of the press ram 12: It is located as an outlet opening on the end face of the pin 15. Thus, even as the pin 15 penetrates the groove, air flowing from the nozzle 13 (schematically indicated by an arrow) can enter the interior of the groove 21 and thereby press the outer surface of an insulating paper firmly against the groove wall of a stator lamination stack. This keeps the insulating paper 30 stationary in its intended position throughout the entire expansion process. Even thin-walled paper is prevented by the applied air pressure forces from shifting axially or buckling at any point within the groove.

[0024] Fig.Figure 2 shows the result of the expansion process. Visible is a flared portion 31 of the insulating paper 30 of a slot insulating paper 30 inserted into a groove 21. The end 31 of the insulating paper protruding axially from the groove was bent outwards into a funnel shape by the application head 10. It can be seen that this section 31 now lies above the groove exit like an outwardly projecting collar. This shape allows the end of the insulating paper 30 to act as an insertion funnel, facilitating the insertion of the rigid winding conductors (hairpins) into the groove. Thanks to the airflow blown in during the expansion process, the insulating paper 30 is neither displaced nor creased or otherwise deformed, but remains in contact with the inner wall of the groove.The presented device thus ensures that the slot insulation papers remain securely in position until the conductor rods are fully inserted and fixed in a subsequent step, for example by impregnation or potting.

[0025] Even without separate illustration in the figures, further advantageous variants of the device can be implemented. For example, the device can have two identical application heads 10 on opposite sides of the stator lamination stack 20 to simultaneously bend both axial ends of the slot insulation papers. Alternatively, in the case of a one-sided widening, a support device with a nozzle 13 can be positioned on the opposite side to blow air into the slot. The support device can, but need not, be identical to a fixing or holding device for the stator lamination stack. Furthermore, the blown-in gas can be heated by means of a temperature control device to warm the insulation paper before deformation.For open grooves, a cover can be attached to the application head 10 and / or the support device or another separate device, which closes the groove opening during expansion so that the medium remains in the groove. Furthermore, it is possible to operate several application heads 10 simultaneously on different grooves in order to bend several insulating papers in parallel. The preferred medium is ordinary air, and the application head 10 can have a base body 11 with an inlet 16 for supplying the air. REFERENCE MARK LIST 10 Application head 11 Basic shapes 12 press dies 13 nozzle 14 Shoulder area 15 cones 16 Admission 20 Stator lamination stack 21 Stator slot 30 insulation paper (slot insulation) 31 Part of the groove insulation paper protruding from the groove QUOTES INCLUDED IN THE DESCRIPTION

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

[0000] DE 100 18 140 A1

[0006]

Claims

[1] Device for expanding axial ends of insulating papers (30) inserted into stator slots (21) of a stator lamination stack (20) of an electric machine, wherein the device has at least one application head (10) with a press punch (12), and wherein the press punch (12) has a shoulder region (14) which is designed such that, after a previously defined travel path of the application head (10) in the axial direction of the slot (21), a portion (31) of the slot insulating paper (30) which protrudes axially from this slot (21) can be expanded in the radial and / or circumferential direction. characterized by , that at least one nozzle (13) is provided for blowing out a gaseous medium and is aligned in relation to the press ram (12) such that the gaseous medium can flow substantially in the axial direction in this groove (21). [2] Device according to claim 1 characterized by, that at least one nozzle (13) is an integral part of the press ram (12) and is provided as at least one outlet on a pin (15) extending on the press ram (12) in the direction of travel and which can be penetrated into the stator slots (21), wherein the outlet is arranged on the surface of the pin (15) in such a way that the gaseous medium can flow in the stator slot (21). [3] Device according to claim 2 characterized by , that at least one nozzle (13) is designed as an outlet on a head side of the pin (15). [4] Device according to any one of the preceding claims 1 to 3 characterized by , that a support device is provided which, when the stator (20) is located between it and the application head (10), acts in its direction of action opposite to the travel path of the press ram (12), and wherein this support device comprises at least one nozzle (13) which is arranged in such a way that the gaseous medium can be blown into the stator groove (21). [5] Device according to any one of the preceding claims 1 to 3 characterized by , that the device comprises two application heads (10) arranged such that one of the application heads (10) is movable in opposite directions into one of the slots (21) on one of the two axial sides of the stator (20) and wherein at least one of the two application heads (10) comprises at least one nozzle (13) for the outflow of the gaseous medium. [6] Device according to any one of the preceding claims 1 to 5 characterized by , that a temperature control device is provided with which the gaseous medium flowing through the at least one nozzle (13) can be brought to different operating temperatures. [7] Device according to any one of the preceding claims 1 to 6 characterized by, that in addition a device is provided for covering a radial opening of the respective groove (21) of the stator (20) inserted into the device on the application head (10) and / or the support device and / or a separate device. [8] Device according to any one of the preceding claims 1 to 7 characterized by that several application heads are arranged in such a way that insulating papers can be expanded in two or more grooves simultaneously. [9] Device according to any one of the preceding claims 1 to 8 characterized by that the gaseous medium is air.

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