Stator with slot closure and temperature sensor

Abstract

Stator for an electrical machine, comprising an axially extending stator body with a plurality of circumferentially distributed stator teeth. Stator slots 5 extend axially through the stator body 3 between the stator teeth 4. Windings 6 are arranged in the stator slots 5, wherein the stator slots 5 have a slot base 7 at a first radial end and a slot opening 8 at a second radial end, and at least one of the slot openings 8 is closed by a respective slot closure means 9, 9', so that the windings 6 are held in the stator slot 5. Furthermore, a temperature sensor 10 is provided, which is arranged on or in one of the slot closure means 9.It is provided that the temperature sensor 10 is arranged between a slot closure means 9 and an end winding 20, and that the slot closure means 9 exerts a radial force on the temperature sensor 10, so that the temperature sensor 10 is pressed radially against the end winding 20 by the slot closure means 9.

Description

The present invention relates to a stator for an electric machine. The stator comprises an axially extending stator body having a plurality of stator teeth arranged in a manner distributed circumferentially. Between the stator teeth, stator grooves extend through the stator body in the axial direction, wherein windings are arranged in the stator grooves. The stator slots have a slot base at a first radial end and a slot opening at a second radial end. At least one of the slot openings is closed by a slot closing means, so that the windings are held in the stator slot. Furthermore, the stator comprises a temperature sensor which is arranged on or in one of the groove closure means.In a stator for an electric machine of the internal rotor type, the slot base is located radially on the outside, in a stator for an electric machine of the external rotor type, the slot base is located radially on the inside.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.A detailed illustration of an electric drive is given in an article of the journal ATZ 113. Vol. 05 / 2011, pages 360-365 of Erik Schneider, Frank Fickl, Bernd Cebulski and Jens Liebold, with the title: High-Integration and Flexible Electric Drive Unit for E-vehicles. In this article, a drive unit for an axle of a vehicle is described, which drive unit comprises an electric motor which is arranged concentrically and coaxially with a bevel gear differential, wherein a shiftable 2 gear planetary gear set is arranged in the power train between electric motor and bevel gear differential, which is also positioned coaxially with the electric motor or the bevel gear differential or spur gear differential. The drive unit is of very compact construction and, owing to the shiftable 2 gear planetary gear set, allows a good compromise between climbing capability, acceleration and energy consumption. Drive units of this type are also referred to as E axles or electrically operable drive train.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.In the development of electric machines provided for E-axles or hybrid modules, there is a continuing need to increase their power densities, so that the cooling of the electric machines required for this purpose is becoming increasingly important. Due to the necessary cooling capacities, hydraulic fluids, such as cooling oils, have become established in most concepts for transporting heat away from the thermally exposed regions of an electric machine.For effective thermal management of such an electric machine, a determination of different temperatures at different positions of the electric machine is necessary. In particular, the most accurate possible temperature measurement should be carried out at the expectable thermal hotspots in order to avoid local or general thermal overloading of the electric machine by the control of the electric machine and / or its cooling system.It is thus known from DE 10 2021 120 989 A1 to provide a temperature sensor in or on a groove closure means. The temperature measurement can then be made possible directly in the region of a hotspot at thermally loaded regions of the stator.The construction of such a groove closure means with an integrated temperature sensor is complicated. The exact positioning in the particularly stressed areas, i.e. in the area of the hotspots, i.e. in particular in the axial center of the stator or elsewhere, is difficult to ensure in the axial, radial or circumferential direction. Similarly, introduced inductive disturbances can lead to problems in the evaluation of the sensor signal.The object of the present invention is therefore to reduce at least one of the problems of the known prior art.This object is achieved by a generic stator having the characterizing features of claim 1. Further embodiments according to the invention can be found in the dependent claims.According to the invention, it is provided that the temperature sensor is arranged between a slot closure means and an end winding and that the slot closure means exerts a radial force on the temperature sensor, so that the temperature sensor is pressed radially by the slot closure means onto the end winding. In this way, a uniform and uniform contact point between the end winding and the temperature sensor can be produced over a relatively large surface area. The accuracy of the temperature signal increases. The radial position of the temperature sensor with respect to the windings in the stator slot, in particular with respect to the end winding, can be determined and ensured particularly accurately.Since a plurality of windings are located in the stator slot, which generate heat by the electrical control and the resistance inherent therein, this heat distributes itself in the axial and radial direction in the stator or in the stator body. A hot spot for this heat is therefore to be expected in the winding which is radially closest to the slot opening. This winding is referred to herein as a final winding. An inner rotor motor is the radially innermost winding, and an outer rotor is the radially outermost winding. By fixing the temperature sensor directly on the outer surface of the end winding, the radial position of the temperature sensor is fixed in such a way that it bears radially in the region of the highest temperature.It can further be provided that the groove closure means in the non-installed state has at least in regions a region protruding from a plane. In particular, the groove closure means in this region accommodates the temperature sensor in a recess facing the end winding. In the installed state of the slot closure means, the surface facing away from the end winding in this region lies in a common plane with the remaining surface of the slot closure means facing away from the end winding. This common plane is parallel to the plane in which the end winding lies. In particular, the two parallel planes can have a course in the circumferential direction of the stator following the stator surface. That is, the planes may be slightly curved in the circumferential direction.In an alternative or supplementary embodiment of the groove closure means, the latter has an axial extent which substantially corresponds to the axial extent of the stator body. The axial ends of the groove closing means define a straight line passing through these two ends. In the installed state, this straight line runs parallel to the end winding and to the axis of the stator. In the installed state, the regions of the groove closure means located axially between the axial ends lie on this straight line, or the straight line is located between the ends everywhere within the groove closure means. In order to exert a radial force on the temperature sensor, the groove closure means is radially prestressed in the installed state. For this purpose, in the non-installed state, the groove closure means is formed radially substantially in the shape of a curve, so that the straight line in this prepared region no longer lies within the groove closure means. The orientation of this arc-shaped configuration is designed in such a way that the groove closure means is bent in the direction of the end winding before installation.In a further development, it can preferably be provided that the slot closure means is a slot closure wedge which extends in the axial direction in the stator slot and lies radially between an end winding and an undercut formed in the axial direction by the stator body, so that the slot closure wedge is held parallel in the plane parallel to the end winding, at least in the region outside the prestressed region, by the undercut and the end winding. The prestressed region is prestressed in the direction of the end winding, so that this results in a contact pressure force for pressing the temperature sensor against the end winding; a radial additional restriction in this region by an undercut is at least not necessary here. In this way, the interacting geometries and designs of slot closure wedge and stator body can generate a radially acting force which, on the one hand, fixes the radial position of the slot closure wedge and, on the other hand, ensures permanent and planar contacting of the temperature sensor on the end winding.In order to make possible a uniform course of the groove closure wedge in the installed state, it is provided that the groove closure wedge has a region tapering in the radial direction in the axial direction. In other words, the groove locking wedge becomes thinner in an axial region. The temperature sensor is arranged in this tapered region. In particular, the tapered region can be identical to the region protruding or prestressed from a plane or a partial region thereof. It can also be particularly preferred that the temperature sensor is accommodated in the tapered region in a recess such that it faces the end winding and at the same time the tapered region ensures that the surface of the slot-type locking wedge facing away from the end winding, i.e. its radial upper side, is planar.The tapered region is preferably formed at the most radially thinnest in the region of the temperature sensor and, starting therefrom, radially thickens in the axial direction, in particular in both axial directions, until a control thickness of the groove closure wedge is achieved. The tapered region is selected in such a way that it comprises the region which, as a result of its prestress in the installed state, exerts a contact force on the temperature sensor radially in the direction of the end winding. In particular, the tapered region coincides practically completely with the protruding region or prestressed region. In the case of a groove closure wedge, the protruding region preferably assumes an arcuate course which simultaneously has a radial thickness which tapers in particular continuously in the axial direction, so that in the region of the connection points of the arcuate course to the remaining, non-protruding region of the groove closure wedge, the radial thickness again corresponds to the control thickness of the groove closure wedge which it has in the remaining axial regions. In this way, on the one hand, a tension-optimized construction of the groove closure wedge is realized in a very confined environment and at the same time material is saved.In order to achieve, in addition or as an alternative to the measures described above, axial positioning of the temperature sensor between the slot closure means and the end winding, it is further provided that the slot closure means has, radially between a radial underside of the slot closure element and a radial upper side of the end winding, at least one guide element for axially guiding and / or positioning the temperature sensor in the stator slot, wherein the at least one guide element has an axial stop for application to an axial end of the temperature sensor and is preferably formed integrally from the slot closure means.The terms "radial underside" and "radial upper side" are to be understood here with reference to the direction toward the winding region, i.e. toward the end winding from the point of view of the slot closure means. For the sake of better comprehension, the surface facing away from the end winding is referred to as radial top side or only top side and the side facing the end winding is referred to as radial bottom side or only bottom side. In an internal rotor motor, the end winding is located radially inside the stator slot. The radial top side of the end winding and also the radial top side of the slot closure wedge then correspondingly also lie radially inside and point radially into the stator or in the direction of a rotor. The radial underside of the groove closure means or of the groove closure wedge is then located radially on the outside, facing the end winding. For an electric motor designed as an external rotor, the radial conditions would correspondingly reverse.The axial position of the temperature sensor can be fixed within the range of predetermined tolerances via the axial stop, on the one hand, and the stop can also function as a guide aid or driver when the groove closure means is inserted into the stator groove, on the other hand, as a result of which the temperature sensor is reliably threaded axially into the stator groove.In a further development, it can be provided that the at least one guide element has a radial underside, with which it faces a radial upper side of the end winding in the installed state, but preferably does not touch the latter. Corresponding damage to the end winding, such as e.g. to paint finishes on the end winding, can be avoided. This radial underside of the groove closure means has a curved or rising or oblique course in the non-installed state of the groove closure means, while in the installed state it lies flat on or parallel to the radial upper side of the end winding, so that the radial upper side of the groove closure means takes up an axially flat surface or a surface slightly curved only in the circumferential direction over the entire axial course in the installed state. The guiding element by placing it on the end winding has the effect that the groove closure means is lifted off the end winding. As a result, the contact pressure force on the temperature sensor would be canceled.In order to effectively ensure a spacing between the guide element and the end winding that helps avoid damage to the end winding, it can be provided that the radial height h of the at least one guide element is smaller than the radial height H of the temperature sensor. The radial height h of the guide element is determined from the radial underside of the groove closure means. In this way, in particular the temperature sensor is securely applied to the end winding, so that an accurate determination of the temperature of the end winding in the axial region of the temperature sensor is possible.In a further development, it can be provided that the cross section of the groove closure means increases axially outwards starting from the at least one guide element. A stable groove closure means with a defined desired flexibility in the region of the temperature sensor is thus made possible. The temperature sensor and the groove closing means can be securely inserted into the stator groove and the temperature sensor can be held at the axial position.In a development of the stator, it can be provided that the radially tapered region is arranged axially between two guide elements. The shape of the guide elements is then adapted to the curvature of the groove closure means. Pressing the temperature sensor against the end winding can then be combined with an axial positioning. In this case, by means of stops of the guide elements in both axial directions, the temperature element can be taken along in the axial direction and, furthermore, accurate axial positioning takes place in the range of the tolerance, which is based on the difference between the axial distance of the guide elements and the axial length of the temperature sensor. The region between the guide elements is thus designed such that it is important for both axial and radial positioning. The geometric course of the groove closure means axially between the guide elements with reduced radial thickness and / or reduced width, in particular without radial spacer elements between the groove edge and / or insulation paper with simultaneously increased thickness and increased width axially outside the guide elements ensures a stress-optimized configuration of the groove closure means which prevents a fracture of the groove closure means due to high stresses.In a further development of the invention, it can be provided that the groove closure means is guideless in the circumferential direction in the region of the temperature sensor and free of restriction for the temperature sensor, so that positioning of the temperature sensor in the circumferential direction takes place exclusively, preferably with a clearance fit to the groove edge of the stator groove, or to any insulation paper that may be present. This makes it possible to save material for the groove closure means and at the same time to resort to already present limitations in the stator. Furthermore, an unnecessary overdetermination of the position of the temperature sensor is avoided. A simpler structure of the stator with slot closure means and temperature sensor is made possible.Even more material can be saved if it is provided that the groove closure means in the region of the temperature sensor has a width b in the circumferential direction that is smaller than the control width B in a region of the groove closure means that is located axially further outward. By fixing the circumferential position by the groove edge of the stator groove or the insulation paper optionally present there, further material can be dispensed with in the circumferential direction and the region of the groove closure means for receiving the temperature sensor can be designed to be more stress-optimized.At the same time, it can be provided that the width b of the groove closure means in the region of the temperature sensor is smaller than the distance of the undercuts that close off the stator groove in the radial direction. As a result, for example, a radial position closer to the groove opening for this groove closure means can be made possible than in the case of the remaining groove closure means which do not accommodate a temperature sensor and have a width B over the entire axial length which is greater than the distance between the undercuts, as a result of which the stator teeth engage behind over the entire axial region of these groove closure means.In a further development of the stator, it can be provided that the temperature sensor has at least one cable, with which it is connected to a control device and / or evaluation device, wherein the groove closure means has at least one sensor groove for receiving the at least one cable, and wherein the at least one sensor groove has a transition fit for receiving the at least one cable. In this way, a secure guidance of the cable in the slot closure element can be ensured without the risk of damage to the cable during the insertion of the slot closure element into the stator slot or thereafter.In particular, it can be provided that the radial depth of the sensor groove, i.e. the depth of the sensor groove, starting from the surface of the radial inner side of the groove closure means, is deeper than the diameter or the width of the at least one cable. In this way, it can be ensured that the opening of the sensor groove is practically closed by the end winding. In particular, a small gap can be present between the radial underside of the groove closure means and the radial upper side of the end winding. This gap can be caused by a web which is arranged between two parallel sensor grooves in two cables used. If the radial underside of the groove closure means has lateral protrusions pointing in the circumferential direction, which are located next to the two sensor grooves, then it can be provided that the named web protrudes beyond the surfaces of these protrusions, in particular wing-shaped protrusions, in the radial direction toward the end winding. Gaps are then formed between the protrusions and optionally also between the cables and the radial upper side of the end winding, while the web lies contacting on the end winding. In a final process step, in the assembly of the slot closing means to the stator, these gaps can be closed by resin or the like.In this embodiment, the sensor groove does not have to extend over the entire axial length of the groove closure means. In particular in the region of the temperature sensor and there in particular axially between two guide elements, it is possible to completely dispense with a sensor groove or provide for the depth of the sensor groove to be less than the radius or half the height of the cable. Between guide elements and the region of the groove closure means in which the sensor groove has a depth greater than the cable diameter, a continuous transition of the sensor groove depth can be provided.In order to guide the cable or cables around the temperature sensor and in particular also around the guide elements in the axial environment, it can be provided that the at least one guide element has at least one receiving groove for receiving the at least one cable, and the at least one receiving groove comprises undercuts for clipping in the at least one cable.Furthermore, it can be provided that the undercuts have a mounting chamfer in the radial direction for gently introducing the at least one cable into the at least one receiving groove, whereby damage to the cable during the assembly of the groove closure means and the temperature sensor can be avoided.In order to enable the connection of the temperature sensor also in the installation space between the groove closure means and the end winding, it can be provided that two cables are present for connecting the temperature sensor, and that the two cables, starting from the temperature sensor as far as the axial end of the groove closure means, are guided through sensor grooves and / or receiving grooves without crossing, preferably parallel to one another. This also means, in particular, a non-coaxial arrangement of the two cables with respect to one another. Shielding the cables from induced currents, for example by twisting and the provision of coaxial cables, is hereby expressly dispensed with in favor of a smaller installation space required.It can be provided that one of the cables is guided in a first axial direction and a second cable is guided in the opposite axial direction away from the temperature sensor through the groove closure means. Preferably, both cables are guided axially through the groove closure means on the same axial side of the temperature sensor. Here, sensor grooves and receiving grooves are provided only on the one axial side of the groove closure means and in the guide element provided on this side. The other side of the groove closure means is then constructed without sensors grooves and the guide element present there is not grooves.In order to make it possible to connect the temperature sensor in a small installation space and at the same time to ensure adequate evaluation of the signals of the temperature sensor, it can be provided in a development of the invention that the temperature sensor is connected to a control device and / or an evaluation device by means of two cables, and the two cables are guided in an intersecting manner, preferably parallel in and / or on the groove closure means. While the stator body has an axial extent L, it is provided that the temperature sensor is positioned at a distance x from the axial center of the stator body, the distance x being greater than zero and less than L / 2. The distance x from the axial center of the stator body is defined by the condition that the signal / noise ratio of the temperature signal read out by the control device and / or evaluation device is above a predetermined threshold value, preferably assumes this threshold value. This displacement of the temperature sensor away from the axial center of the stator body does not make it possible to obtain an exact measurement value for the temperature in the region of the expected hotspot in the axial center of the stator body, i.e. the axial center of the end winding. However, it is made possible that the connection of the temperature sensor to the electronics can take place via two untwisted or coaxial cables. This allows the installation space required for installing the temperature sensor to be reduced. If care is taken to ensure the signal / noise ratio during the positioning of the temperature sensor as described, a measure for the temperature in the vicinity of the expected hotspot in the axial center of the stator body can nevertheless be determined, which measure can be used for the actuation of the electric machine or of the cooling oil circuit. The interference signal is due to the two parallel cables which are susceptible along their axial extent to induced voltages which have their origin in the rotor rotation of the E-motor or the alternating frequency of the stator currents. By reducing the necessary length of the cables to the temperature sensor, the induced voltage is correspondingly reduced.Furthermore, the invention is achieved by a method for determining a stator temperature of an electric motor, comprising a rotor and a stator, in which the stator is constructed according to the just described combination of features, in particular the combination of features of claim 18, and which is characterized in that the threshold value is defined as a function of a first low-pass filter used for interference signals as a function of the rotational speed of the rotor and / or a second low-pass filter used as a function of the clock frequency of the inverter of the windings. By using the described low-pass filters, the useful signal can be improved and thus a lower threshold value for the signal / noise ratio of the original signal can be tolerated, so that the temperature sensor can be positioned closer to the axial center of the stator body. That is, the distance x can be reduced, whereby a more accurate temperature measurement in the region of the expected hotspot becomes possible.Alternatively or additionally, the invention can also be achieved by a method for determining a stator temperature of an electric motor, comprising a rotor and a stator according to claim 20, in which the distance x is determined such that the voltage(s) induced by the rotational speed of the rotor and / or clock frequency of the inverter for driving the windings are less than the factor 5, preferably less than the factor 100. Here, a reliably measured signal of the temperature sensor can then be used for determining the temperature of the stator.In the installed state of the slot closure means, the temperature sensor can additionally be connected in a materially integral manner, in particular via a tear-off resin, casting resin or an adhesive, to the slot closure means, to the end winding and the adjacent stator teeth and possibly to insulation paper present. For this purpose, material is accordingly preferably introduced into the stator in a drop method.An exemplary embodiment of the invention, to which the invention is not restricted and from which further features according to the invention can be derived, is illustrated in the following figures. The following are shown: FIG. 1 shows a cross section through a stator, FIG. 2 : an axially parallel section through a stator, FIG. 3 : a detail from the stator according to FIG. 1 with a slot locking wedge and temperature sensor, FIG. 4 : a longitudinal section through a groove closure wedge with temperature sensor, FIG. 4 b : shows a detail section from FIG. 4, FIG. 5 shows a cross section through a groove closure wedge with a temperature sensor, FIG. 6 is a plan view of the radial underside of a groove closure wedge with temperature sensor, FIG. 7 : shows a slot locking wedge during an insertion process into the stator, and FIG. 8 : shows the slot locking wedge according to FIG. 7 in the stator.In FIGS. 1 and 2, a stator 1 with a stator body 3 is shown for the purpose of illustration. The stator body 3 is formed by a plurality of stator laminations or stator laminated cores 19 stacked in the axial direction. The axial direction extends along the axis 18.The stator 1 shown here belongs to an electric machine designed as an internal rotor. In the assembled state of the electric machine, in the interior 14 of the stator 1, there is a rotor, not shown here, which likewise extends in the axial direction. The axis of rotation of the rotor coincides with the axis 18 of the stator 3.The stator body 3 comprises stator teeth 4 which extend radially inward starting from a stator yoke 40. The stator teeth 4 are separated from each other in the circumferential direction by stator grooves 5. Windings 6 of the stator 1 are located in the stator slots 5.The electric machine is driven in a manner known per se by supplying the windings 6 with alternating current via an inverter, not shown here. The rotor, not shown here, then rotates in the changing magnetic field. A suitable alternating frequency for the stator current results in a magnetic field rotating in the circumferential direction, which is followed or preceded by the rotor. The stator teeth 4 are wound around by the windings 6 in such a way that respectively adjacent stator teeth 4 form a magnetic field with opposite polarization.The stator body 3 has an axial extent of the length L with the axial center at L / 2. the stator laminated cores 19 are formed or arranged substantially symmetrically with respect to the axial center L / 2 in the axial direction. The alternating current of the windings 6 generates heat in the stator grooves 5, which is absorbed by the stator yoke 40 and the stator teeth 4 and is dissipated radially inward. The stator body 3 heats up as a result of this heat. In the axial direction, the heat within the stator grooves 5 will form a hot spot of the maximum heat at the axial center L / 2.The stator slots 5 have a radially outer slot base 7 which lies radially on the inside opposite a stator opening 8. The stator slots 5 are substantially completely filled by windings 6, as shown in FIG. 3. FIG. 3 shows a detail from FIG. 2 with three stator slots 5 for this purpose. In each stator slot there are windings 6 from the slot base 7 to the slot opening 8, The radially innermost winding 6 is referred to as the end winding 20, since it terminates the windings 6 in the respective stator slot 5 toward the outside. The stator slots 5 are lined in their interior with an insulation paper 41 for insulating the windings 6 from the stator body 3.The three stator slots 5 in FIG. 3 are each closed radially on the inside by a slot closure wedge 9, 9'. Due to the heat that arises, the functioning of the electric machine can be impaired until damage occurs. Therefore, a temperature sensor 10 is provided, which is intended to output information about the temperature that arises in the stator 1. For this purpose, this temperature sensor 10 is connected to an evaluation or control unit via cable 12. Depending on the determined temperature value, a cooling of the electric machine or the electric machine itself is correspondingly regulated. This can lead to the disconnection of the electric machine and the interruption of the current of the stator. A temperature measurement which is as exact as possible is therefore necessary. Due to the symmetry of the stator 1, the measurement of the temperature in only one location is usually sufficient. For this purpose, the middle slot-locking wedge 9 shown receives the temperature sensor 10, which is clamped between the end winding 20 and the slot-locking wedge 9. The slot-closure wedge 9 exerts a radial force F 1 on the temperature sensor 10, so that the latter bears flat against the end winding 20. The remaining slot locking wedges 9' of the stator 1 do not have a temperature sensor 10 here. However, for redundancy reasons, this can be provided to ensure reliability or also to obtain a better mean value for the stator temperature.The slot locking wedges 9' and 9 are held in the respective stator slot 5 by undercuts 22 in the slot openings 8 formed by the stator body 3. The insulation papers 41 also have a corresponding paper section 42 extending inward in the circumferential direction.The stator groove 5 with the groove closure wedge 9, which accommodates the temperature sensor 10, is constructed identically to the remaining stator grooves 5; undercuts 22 are also present here. The slot-type locking wedge 9, on the other hand, is different from the remaining slot-type locking wedges 9' in order to securely receive, position and place the temperature sensor 10 on the end winding 20. This structure of the groove locking wedge 9 is more clearly shown and recognizable in FIGS. 4 to 7. The structure of the slot-locking wedge 9 results in it exerting the radial force F1on the end winding 20. It has a radial underside 24 which faces the end winding 20 and a radial upper side 43 with which it faces the rotor in the finished E-machine. Due to the configuration of the groove closure wedge 9, the radial upper side 43 of this groove closure wedge 9 lies radially further in the region of the groove opening 8 and thus closer to the rotor than the radial upper sides 43' of the remaining groove closure wedges 9'.FIG. 4 shows the groove locking wedge 9 with temperature sensor 10 in the non-installed state. This is a sectional illustration along its axial extent. The groove closure wedge 9 is so long in the axial direction that it can fill or close a groove opening 8 in the axial direction. The axial extent corresponds here substantially to the effective axial length of the stator 1 and thus to the length L of the stator body 3. The electronics can comprise an evaluation unit for evaluating the sensor signals and / or a regulating or control unit for regulating and / or controlling a cooling, the stator current or the electric machine which accommodates the stator.The cables 12 are fed to an axial end of the groove closure wedge 9 and connected to the temperature sensor 10. No cables 12 are located at the other axial end of the groove closure wedge 9, and the cables 12 are guided in sensor grooves 11 up to a first guide element 26 in the groove closure wedge 9. In the first guide element 26, the cables 12 are guided in receiving grooves 28. In the section 45 between the first guide element 26 and the temperature sensor 10, practically no guidance of the cables 12 takes place. They can also lie in a shell-shaped recess 44 of the radial underside 24 of the groove closure wedge 9. These shell-shaped recesses 44 with cables 12 arranged therein are shown in FIG. 6.The temperature sensor 10 lies axially between the first guide element 26 and a second guide element 26 bin a recess 31 of the groove closure wedge 9, which recess 31 lies axially within a tapered region 23 of the groove closure wedge 9. Within the tapered region 23, the groove closure wedge 9 has a smaller radial thickness d between its radial inner side 24 and its radial outer side 43 than in the rest of the groove closure wedge 9. In this remaining region, it has a control thickness D>d. The tapered region 23 extends axially, starting from the temperature sensor 10, as far as behind the two guide elements 26; this tapered region 23 initially saves material of the groove closure wedge 9. The groove closure wedge 9 is thinnest directly in the region of the temperature sensor 10. These savings provide the space for the temperature sensor 10 and also for the guide elements 26. On the other hand, this creates an arc shape of the groove closure wedge 9 just in this tapered region 23, so that the groove closure wedge 9 is bent in this tapered region 23 in the direction of its radial underside 24. For the sake of better illustration, a line 46 is drawn in FIG. 4, which line passes through the two axial ends of the groove closure wedge 9. Outside the tapered region 23, the radial top side 43 of the groove closure wedge 9 lies on this line 46. in the tapered region 23, the groove closure wedge 9 projects out of the plane of this line 46, i.e. there is a distance between the line 46 and the radial top side 43 in this tapered region 23. This distance increases starting from the regions with the control thickness D as far as the temperature sensor 10, so that the radial top side 43 and thus also the radial bottom side 24 of the groove closure wedge 9 here have an arcuate course in the direction of the radial bottom side 24. With respect to the end winding 20, not shown here, the slot-locking wedge 9 is bent towards this end winding 20. This course of the slot-type locking wedge 9 protruding from the plane of the line 46 then allows a radial contact pressure force F 1 starting from the slot-type locking wedge 9 on the temperature sensor 10 in the installed state of the slot-type locking wedge 9, so that the latter is pressed against the end winding 20. The groove closure wedge 9 thus has, as a result of the arc-shaped course in the relaxed, i.e. non-inserted state, a prestress in the installed state, with which prestress the temperature sensor 10 is pressed against the end winding 20. In the installed state, the groove closure wedge 9 is prestressed to such an extent that its radial upper side 43 follows the line 46 substantially over the entire axial length.For the purpose of illustration, FIG. 4 b shows a detail of the radially tapered region 23 from FIG. 4 in an enlarged manner. The cables 12 extend as far as the beginning of the tapered region 23 within sensor grooves 11, which limit the mobility of the cables 12 both in the radial and in the circumferential direction. This is done by means of an overfitting of the groove walls. As can be seen in FIG. 4 b, the circumferential limitations for the cables 12 are reduced in the axial course of the groove closure wedge 9, while the thickness of the groove closure wedge 9 decreases from a control thickness D toward the thickness d. When the thickness of the groove-locking wedge 9 assumes approximately the smallest extent, the groove-locking wedge 9 forms the first guide element 26. The first guide element 26 has a stop 27 at its end facing the temperature sensor 10. This stop 27 has a height h1. The first guide element 26 has a radial underside 24 bwhich has a thickness increasing axially with respect to the stop 27. The surface profile of the radial underside 24 bis correspondingly oblique toward the temperature sensor 10. This slope is present in the non-installed state and in particular on the radial underside 24 of the groove closure wedge 9, which results in an ascending radial underside 24 b. The bevel is designed in such a way that the radial underside 24 bin the installed state lies substantially parallel to the radial upper side 25 of the end winding 20.Axially on the inside, the first guide element 26 has the axial stop 27 for axial guidance and positioning of the temperature sensor 10. The stop 27 can serve as a driver for the temperature sensor 10 when the groove closure wedge 9 is introduced. As can be seen in FIG. 4, the second guide element 26 also has a steep surface profile of the radial underside 24 band a stop 27. In the installed state, the stops 27 of the two guide elements 26 and 26 bfunction as positioning means for axially positioning the temperature sensor 10. Its tolerance is determined by the greater axial distance of the guide elements 26, 26 bin relation to the axial extent of the temperature sensor 10.In the axial region between the stops 27, there are no restrictions at all in the circumferential direction, neither for the temperature sensor 10 nor for the cables 12. The cables 12 are fixed by the groove locking wedge 9, in particular in the region between the stop 27 of the first guide element 26 and the temperature sensor 10, neither in the circumferential direction nor in the radial direction.A cross section through the groove closure wedge 9 along the section line A-A from FIG. 4 bis illustrated in FIG. 5. This is a spatial illustration in which the region axially between the first guide element 26 and an axial end of the groove closure wedge 9 can also be seen.In the tapered region 23, the width of the groove closure wedge 9 is also reduced from the control width B to the reduced width b. Starting from a control width B, the width in the axial region after the first guide element 26 is reduced to a smaller width b. In the region of the control width B, the cables 12 are guided in sensor grooves 11 with an oversized dimension, so that they are fixed in the circumferential and radial directions. Between the sensor grooves 11, the groove locking wedge 9 forms a web 47. The web 47 projects beyond the wing-like protrusions 48 adjoining the sensor grooves 11 in the circumferential direction in the radial direction, so that in the installed state the web 11 abuts on an end winding 20, while a small gap is present between the wing-like protrusions 48 and the end winding 20. When filling the stator 1 with insulating material, such as resin, this slot and the cables 12 accessible thereby for the cast or tuft material are also securely cast in the sensor grooves 11.By reducing the width B, bof the groove closure wedge 9 with a simultaneous decrease in the radial thickness D, d, the cross section of the groove closure wedge 9 overall decreases, which means a stress optimisation with regard to the contact pressure F 1 exerted on the temperature sensor 10 by the shaping of the groove closure wedge 9.Furthermore, the first guide element 26 is shown in FIG. 5. This has receiving grooves 28 which are designed to receive the cables 12 and which comprise undercuts 29 for the radial fixing of the cables 12 in the first guide element 26. The undercuts 29 have radially effective mounting bevels 30, which allow easy and secure clipping-in of the cables 12. This is advantageous in particular when the cables 12 have an outer insulating layer.The decrease in the width of the groove closure wedge 9 from a control width B to a reduced width b is again clearly shown in FIG. 6. In FIG. 6, a top view of the groove closure wedge 9 from the radial top side 43 is shown for this purpose. The sensor grooves 11 and cables 12 are located on the radial underside 24.In FIG. 7 it is shown how the slot locking wedge 9 is inserted axially into a stator slot 5. In the stator slot 5, windings 6 with the end winding 20 are located radially on the inside, i.e. in the region of the slot opening 8. The radial underside 24 of the slot locking wedge 9 and the radial underside 24 bof the second guide element 26 bare located partially in the stator slot 5 or in the region of the winding head 49 at an axial end of the stator body 3. When the slot-type locking wedge 9 is pushed in further axially, the radial underside 24 bof the second guide element 26 bwill first come into contact with the radial upper side 25 of the end winding 20. Due to the slope of the surface of the radial underside 24 bof the second guide element 26 b, the groove closure wedge 9 is already slightly displaced in the direction of the groove opening 8, i.e. radially inward, in this region and the arcuate region is raised counter to a restoring force. In the further course, the temperature sensor 10 also reaches the stator groove 5 and comes into contact with the radial upper side 25 of the end winding 20, it being possible in this case for the temperature sensor 10 to be subjected to an axial force by the axial stop 27 of the first guide element 26, as a result of which it is pushed axially into the stator groove 5. Since the temperature sensor 10 has a radial height H which is higher than the radial height h2 of the second guide element 26b or of the stop 27' of the second guide element, the radial underside 24b of the second guide element 26b lifts off from the radial upper side 25 of the end winding 20, so that a gap is formed here. When the groove closure wedge 9 is inserted further, no further contact occurs within the tapered region 23 between the end winding and the radial underside 24 of the groove closure wedge 9 or the radial underside 24 bof the first guide element 26, which is also due to the height h 1 of the stop 27 of the first guide element 26, which is smaller than the height H of the temperature sensor 10. Overall, H>h1>h2 applies here.Only when the groove closure wedge 9 is pushed with its region of the control thickness D into the stator groove 5 is at least the web 47 located between the sensor grooves 11, as shown in FIG. 5 and embodied for this purpose, on the end winding 20 or its radial top side 25. Gaps (of different thickness) are now present between the radial upper side 25 of the end winding 20 and the radial lower sides 24 bof the guide elements 26 and 26 band the radial lower sides 24 of the wing-like formations 48. In the axial region between the guide elements 26 and 26 b, the radial underside 24 of the slot-closure wedge 9 is situated completely at a distance from the radial height H of the temperature sensor 10 from the radial upper side 25 of the end winding 20. In this region, no further structures of the slot closure wedge 9 are situated between the cables 12 and the temperature sensor 10, on the one hand, and the insulation paper 41 or the inner side of the stator slot 5. When the stator 1 is finally cast with an insulating material, these gaps and clearances are filled by the insulating material and the positions of the cables 12 and the temperature sensor 10 are finally determined.This final state of the slot locking wedge 9 inserted into the stator slot 5 is shown in FIG. 8. The undersides 24 bof the two guide elements 26 are each spaced apart from the radial upper side 25 of the end winding 20, wherein the radial underside 24 bof the second guide element 26 bis spaced apart further than the radial underside 24 bof the first guide element 26. In the regions of the control width B, the groove closure wedge 9, as described in FIG. 3, is prevented from moving radially inward by the undercuts 24. Since the groove closure wedge 9 is deformed in the tapered region 23 in the direction radially inward, the desired contact pressure force F 1 is present radially outward here, which presses the temperature sensor 10 against the end winding 20. The width b of the groove closure wedge 9 can be smaller here than the distance between the undercuts 22, as a result of which the groove closure wedge 9 is located here further radially inward than the remaining groove closure wedges 9' without a temperature sensor 10.The temperature sensor 10 shown in FIG. 8 is disposed in the stator groove 5 at a distance X from the axial center L / 2 of the stator body 3. The distance X here denotes that part of the temperature sensor 10 which represents for the temperature sensor 10 at least the point of effect in the axial direction for temperature measurement. The distance X is greater than 0 and less than L / 2, which describes a displacement of the temperature sensor 10 away from the axial center L / 2 with the highest temperature to a region axially further outward in the direction of the winding head 49. The temperature sensor 10 now does not measure the temperature of the stator body 3, as ideally desired in the region of the hotspot, but rather axially spaced therefrom. As shown in FIG. 5, the cables 12 for contacting the temperature sensor 10 are situated in the sensor grooves 11 without crossing, parallel, and electromagnetic shielding of the cables 12 is not provided, and the alternating electric field or magnetic field of the stator 1 by the applied alternating frequency of the stator current induces a first interference voltage in the cables 12. The longer the sections of the cables 12 that are located axially within the stator body 3, the greater are these interference signals in the cables 12, so that a measurement or evaluation of the measurement signals of the temperature sensor 10 thereby deteriorates or becomes impossible. In order to achieve the most accurate possible temperature measurement in the region of the hotspot, the distance X is selected such that the signal / noise ratio of the measurement signal lies in a range which reliably enables a measurement or temperature determination and at the same time the measured temperature has the smallest possible deviation from the temperature expected at L / 2 in the hotspot. In this way, the distance X is predetermined by a limit value determination for the signal / noise ratio.In the evaluation device or measuring device or control device, not shown, low-pass filters can also be provided which filter out interference signals at correspondingly higher frequencies depending on the rotational frequency of the rotor and / or the alternating frequency of the inverter to the stator power supply. As a result, the signal / noise ratio can be improved or the limit value for the signal / noise ratio upstream of the low-pass filter or the low-pass filter can be reduced, so that overall a smaller distance X is made possible and the measured temperature is closer to the actual temperature at the hotspot, i.e. at the axial center L / 2.In a drop process following the introduction of the slot closure wedge 9, the temperature sensor 10 and the slot closure wedge 9 are connected in a form-fit and firmly bonded manner to the adjacent components insulation paper 41, stator laminated core 19 and winding 6 or end winding 20. The temperature sensor 10 is then positioned exactly on the end winding 20 at a predetermined axial distance from the hotspot, this distance being within narrow predetermined tolerances.List of reference characters1 Stator 3 Stator body 4 Stator teeth 5 Stator slots 6 Windings 7 Slot base 8 Slot opening 9, 9' Slot closure wedge 10 Temperature sensor 11 Sensor slot 12 Cable 14 Interior 15 Motor vehicle 16 Drive train 17 Control unit 18 Axle 19 Stator laminated core 20 End winding 21 Protruding region 22 Undercut 23 Tapered region 24, 24b Radial underside (NVK; Guide element) 25 Radial top side (end winding) 26 First guide element 26 bSecond guide element 27 Axial stop 28 Receiving groove 29 Undercuts 30 Mounting chamfer 31 Recess 40 Stator yoke 41 Insulation paper 42 Paper section 43, 43' Radial top side 44 Shell-shaped recess 45 Section 46 Line 47 Web 48 Wing-like protrusions 49 Winding head F 1 Contact pressure force d Radial thickness D Control thickness H, h Radial height b Width B Control width A-A Cutting line X Distance L Length Stator L / 2 Axial centerReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2021 120 989 A1

[0008] Cited Non-Patent LiteratureJournal ATZ 113. Vol. 05 / 2011, pages 360-365 by Erik Schneider, Frank Fickl, Bernd Cebulski and Jens Liebold, with the title: High-Integral and Flexible Electric Drive Unit for E-vehicles

[0004]

Claims

A stator (1) for an electric machine, comprising an axially extending stator body (3) having a plurality of stator teeth (4) arranged in a circumferentially distributed manner, stator grooves (5) extending between the stator teeth (4) in the axial direction through the stator body (3), windings (6) arranged in the stator grooves (5), wherein the stator grooves (5) have a groove base (7) at a first radial end and a groove opening (8) at a second radial end, and at least one of the groove openings (8) is closed by at least one groove closure means (9, 9'), such that the windings (6) are held in the stator groove (5), and having a temperature sensor (10) arranged at or in one of the groove closure means (9), characterized in that the temperature sensor (10) is arranged between a groove closure means (9) and an end winding (20), and that the groove closure means (9) exerts a radial force on the temperature sensor (10), so that the temperature sensor (10) is pressed radially by the groove closure means (9) onto the end winding (20).Stator (1) according to Claim 1, characterized in that, in the non-installed state, the slot closure means (9) has, at least in regions, a region (21) which projects out of a plane and has a surface which points away from the end winding (20) and, in the installed state, lies in a common plane, parallel to the plane of the end winding (20), with the remaining surface of the slot closure means (9) which points away from the end winding (20), and wherein the temperature sensor (10) is preferably accommodated in a recess (31) of the region (21) which faces the end winding (20).Stator (1) according to Claim 2, characterized in that the slot closure means is a slot closure wedge (9) which extends in the axial direction in the stator slot (5) and lies radially between an end winding (20) and an undercut (22) formed in the axial direction by the stator body (3), with the result that the protruding region (21) is forced through the undercut (22) and the end winding (20) into the plane parallel to the end winding in such a way that a contact pressure force (F1) for pressing the temperature sensor (10) onto the end winding (20) results as a result.Stator (1) according to Claim 3, characterized in that the slot-locking wedge (9) has a region (23) which narrows in the radial direction in the axial direction, the temperature sensor (10) is arranged in the narrowed region (23), the narrowed region (23) is formed at the radially thinnest in the region of the temperature sensor (10) and, starting therefrom, radially thickens in the axial direction, in particular in both axial directions, until a control thickness (D) of the slot-locking wedge (9) is achieved.Stator (1) according to one of the preceding claims, characterized in that the slot closure means (9) has, radially between a radial underside (24) of the slot closure means (9) and a radial upper side (25) of the end winding (20), at least one guide element (26) for axially guiding and / or positioning the temperature sensor (10) in the stator slot (5), wherein the at least one guide element (10) has an axial stop (27) for application to an axial end of the temperature sensor (10) and is preferably formed integrally from the slot closure means (9).Stator (1) according to Claim 5, characterized in that the at least one guide element (26) has a radial underside (24b), with which it is directed towards a radial upper side (25) of the end winding (20) in the installed state, wherein this radial underside (25b) has a curved or rising or oblique course in the axial direction in the non-installed state of the slot closure means (9) and, in the installed state, is situated flatly on or parallel to the radial upper side (25) of the end winding (20), with the result that the radial upper side (43) of the slot closure means (9) remains unaffected by a cooperation between guide element (26) and end winding (20).Stator (1) according to Claim 6, characterized in that the radial height h of the at least one guide element (26) is less than the radial height H of the temperature sensor (10).Stator (1) according to either of Claims 6 and 7, characterized in that the cross section of the slot closure means (9) increases axially outwards starting from the at least one guide element (26).Stator (1) according to Claim 4 and one of Claims 6 to 8, characterized in that the radially tapered region (23) is provided at least axially between two guide elements (26).Stator (1) according to one of the preceding claims, characterized in that the groove closure means (9) is guideless in the circumferential direction in the region of the temperature sensor (10) and free of restriction for the temperature sensor (10), so that the temperature sensor (10) is positioned in the circumferential direction exclusively, preferably with a clearance fit, with respect to the groove edge of the stator groove (5).Stator (1) according to Claim 10, characterized in that the slot closure means (9) has, in the region of the temperature sensor (10), a width b which is smaller in the circumferential direction than the control width B in a region of the slot closure means (9) which is situated axially further outwards.Stator (1) according to Claims 3 and 11, characterized in that the width b of the slot closure means (9) in the region of the temperature sensor (10) is smaller than the spacing of the undercuts (22) which close off the stator slot (5) in the radial direction.Stator (1) according to one of the preceding claims, characterized in that the temperature sensor (10) has at least one cable (12), by means of which it is connected to a control device and / or evaluation device, wherein the groove closure means (9) has at least one sensor groove (11) for receiving the at least one cable (12), wherein the at least one sensor groove (11) has a transition fit for receiving the at least one cable (12).Stator (1) according to Claim 13, characterized in that the radial depth of the sensor groove (11) is deeper than the diameter or the width of the at least one cable (12), so that the opening of the sensor groove (11) is closed by the end winding (20) by bearing against the latter.Stator (1) according to one of Claims 13 or 14 and one of Claims 5 or 6, characterized in that the at least one guide element (26) has at least one receiving groove (28) for receiving the at least one cable (12), and the at least one receiving groove (28) comprises undercuts (29) for clipping in the at least one cable (12).Stator (1) according to Claim 15, characterized in that the undercuts (29) have a mounting chamfer (30) in the radial direction for gently introducing the at least one cable (12) into the at least one receiving groove (28).Stator (1) according to one of Claims 13 to 16, characterized in that two cables (12) are present for connecting the temperature sensor (10), and in that the two cables (12), starting from the temperature sensor (10), are guided without intersections, preferably parallel to one another, as far as the axial end of the slot closure means (9) through sensor slots (11) and / or receiving slots (28) in the slot closure means (9).Stator (1) according to one of the preceding claims, characterized in that the temperature sensor (10) is connected to a control device and / or an evaluation device by means of two cables (12), the two cables (12) are guided in the and / or on the groove closure means (9) without crossing, preferably parallel, the stator body (3) has an axial extent L, and the temperature sensor (10) is positioned at a distance x from the axial centre L / 2 of the stator body (3), wherein the distance x is greater than zero and less than L / 2 and it is determined in that the signal / noise ratio of the temperature signal read out by the control device and / or evaluation device is above a predefined threshold value.Method for determining a stator temperature of an electric motor, comprising a rotor and a stator according to Claim 18, characterized in that the threshold value is defined as a function of a first low-pass filter used for interference signals as a function of the rotational speed of the rotor and / or a second low-pass filter used as a function of the clock frequency of the inverter of the windings (6).Method for determining a stator temperature of an electric motor, comprising a rotor and a stator according to Claim 18 or according to Claim 19, characterized in that the distance x is determined such that the voltage(s) induced by the rotational speed of the rotor and / or clock frequency of the inverter for driving the windings (6) are less than a factor of 5, preferably less than a factor of 100, in relation to the signal of the temperature sensor (10).Method according to either of Claims 19 and 20, characterized in that the sampling rate of the temperature sensor (10) is defined in an optimized manner as a function of the frequency of the inverter and / or the rotational speed of the rotor.

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