Stator with slot closure means and temperature sensor

Abstract

The invention relates to a stator (1) for an electric machine, comprising an axially extending stator body (3) with a plurality of circumferentially distributed stator teeth (4); stator slots (5) which extend through the stator body (3) in the axial direction between the stator teeth (4); windings (6) provided in the stator slots (5); an outermost end winding (20) of the windings (6), 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') such that the windings (6) are held in the stator slot (5); and a temperature sensor (10) which is provided on or in one of the slot closure means (9). The temperature sensor (10) is connected to a control device and / or an analysis device by means of two cables (12), the two cables (12) are guided in and / or on the slot closure means (9) without crossing each other, preferably in a parallel manner, the stator body (3) has an axial extension L, and the temperature sensor (10) is positioned at a distance x to the axial center L / 2 of the stator body (3). The distance x is greater than null and less than L / 2 and is determined such that the signal-to-noise ratio of the temperature signal read by the control device and / or analysis device lies above a specified threshold.

Description

[0001] Stator with slot closure means and temperature sensor The present invention relates to a stator for an electrical machine. The stator comprises an axially extending stator body with a plurality of stator teeth arranged in a circumferentially distributed manner. Stator slots extend between the stator teeth in the axial direction through the stator body, with windings arranged in the stator slots. The outermost winding of these windings is referred to as the end winding. 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 closure means such that the windings are held in the stator slot. The stator further comprises a temperature sensor which is arranged on or in one of the slot closure means.In a stator for an internal rotor electric machine, the slot base is located radially on the outside; in a stator for an external rotor electric machine, the slot base is located radially on the inside. The end winding is the winding that is located on the outside relative to the slot base and is the last winding in the area of ​​the slot opening. In an internal rotor, the end winding is the radially innermost winding; in an external rotor, it is the radially outermost winding. Electric motors are increasingly being used to power motor vehicles as alternatives to combustion engines that require fossil fuels. Considerable efforts have already been made to improve the everyday suitability of electric drives and to offer users the same driving comfort they are accustomed to. A detailed description of an electric drive can be found in an article in the magazine ATZ 113.Year, 05 / 2011, pages 360-365 by Erik Schneider, Frank Fickl, Bernd Cebulski and Jens Liebold with the title: Highly Integrated and Flexible Electric Drive Unit for E-Vehicles. This article describes a drive unit for one axle of a vehicle, which comprises an electric motor arranged concentrically and coaxially with a bevel gear differential. In the power train between the electric motor and the bevel gear differential, a switchable 2-speed planetary gear set is arranged, which is also positioned coaxially with the electric motor or the bevel gear differential or spur gear differential. The drive unit is very compact and, thanks to the switchable 2-speed planetary gear set, allows a good compromise between climbing ability, acceleration and energy consumption. Such drive units are also referred to as E-axles or electrically operated drive trains.In addition to purely electric drivetrains, hybrid drivetrains are also known. Such drivetrains in a hybrid vehicle typically comprise a combination of an internal combustion engine and an electric motor, enabling purely electric operation—for example, in urban areas—while maintaining sufficient range and availability, particularly during cross-country journeys. Furthermore, in certain operating situations, it is possible to use both the internal combustion engine and the electric motor to drive the vehicle simultaneously. In the development of the electric motors intended for e-axles or hybrid modules, there is a continuing need to increase their power density, so the necessary cooling of the electric motors is becoming increasingly important.Due to the necessary cooling performance, hydraulic fluids such as cooling oils have become established in most concepts for dissipating heat from the thermally stressed areas of an electrical machine. For effective thermal management of such an electrical machine, it is necessary to determine various temperatures at different positions on the electrical machine. In particular, at expected thermal hotspots, the temperature measurement should be as accurate as possible in order to avoid local or general thermal overload of the electrical machine by the control of the electrical machine and / or its cooling system. For example, it is known from DE 102021120989 A1 to provide a temperature sensor in or on a slot closure means. The temperature measurement can then be made directly in the area of ​​a hotspot in thermally stressed areas of the stator.The construction of such a slot closure device with an integrated temperature sensor is complex. Precise positioning in the particularly stressed areas, i.e., in the area of ​​the hotspots, i.e., particularly in the axial center of the stator or elsewhere, is difficult to ensure in the axial, radial, or circumferential direction. Likewise, introduced inductive interference can cause problems in the evaluation of the sensor signal. The present invention is therefore based on the object of reducing at least one of the problems of the known prior art. This object is achieved by a generic stator with the characterizing features of claim 1. Further embodiments of the invention can be found in the subclaims.According to the invention, the temperature sensor is connected to a control device and / or an evaluation device by means of two cables, wherein the two cables are guided without crossing, preferably parallel in and / or on the slot closure means. While the stator body has an axial extent L with an axial center at L / 2, it is provided that the temperature sensor is positioned at a distance x from the axial center L / 2 of the stator body. The distance x should be greater than zero and less than L / 2. The distance x from the axial center of the stator body can preferably be determined via the condition that the signal-to-noise ratio of the temperature signal read out by the control device and / or evaluation device is above a predetermined threshold value.By moving the temperature sensor away from the axial center of the stator body, there is no longer any possibility of obtaining an exact measured value for the temperature in the area of ​​the expected hotspot in the axial center of the stator body, i.e. the axial center of the end winding. However, this does make it possible to connect the temperature sensor to the electronics via two untwisted or coaxial cables. This can reduce the space required for installing the temperature sensor. If the signal-to-noise ratio is observed as described when positioning the temperature sensor, a measure of the temperature in the area of ​​the expected hotspot in the axial center of the stator body can still be determined. This measure can be used to control the electric motor or the cooling oil circuit despite the expected deviation from the actual temperature at the hotspot.The interference signal is due to the two parallel cables, which are susceptible to induced voltages along their axial extension, which originate from the rotor rotation of the electric 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 reduced accordingly. Thus, two cables are required to connect the temperature sensor, with the two cables being routed without crossings from the temperature sensor to the axial end of the slot closure means. This particularly includes a non-coaxial arrangement of the two cables. Shielding of the cables against induced currents, e.g.by twisting and the provision of coaxial cables is expressly dispensed with in favor of a smaller required installation space, so that it is possible to accommodate the temperature sensor in the small installation space between the slot closure means and the end winding. In a further development, it is provided that the slot 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, secure guidance of the cable in the slot closure means can be ensured without there being any risk of damage to the cable when inserting the slot closure means 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 inside of the slot closure means, is deeper than the diameter, orthe maximum width of at least one cable. In this way, it can be ensured that the opening of the sensor slot is practically closed by the end winding. In particular, a small gap can be present between the radial underside of the slot 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 slots when two cables are used. If the radial underside of the slot closure means has lateral formations pointing in the circumferential direction, which are located next to the two sensor slots, then it can be provided that said web projects beyond the surfaces of these lateral formations, in particular wing-shaped formations, in the radial direction towards the end winding. Between the lateral formations and, if applicable,Gaps then also form between the cables and the radial upper side of the end winding, while the web lies in contact with the end winding. In a final process step, when the slot closing device is assembled with the stator, these gaps can be closed with resin or something similar. The terms “radial underside” and “radial upper side” are to be understood here in relation to the direction to the winding area, i.e. to the end winding from the perspective of the slot closing device. For ease of understanding, the surface facing away from the end winding is referred to as the radial upper side or just the upper side, and the side facing the end winding is referred to as the radial underside or just the underside. In an internal rotor motor, the end winding is located radially inside the stator slot.The radial upper side of the end winding and also the radial upper side of the slot closure wedge are then located radially inward and point radially into the stator or in the direction of a rotor. The radial underside of the slot closure means or of the slot closure wedge is then located radially outward, facing the end winding. For an electric motor designed as an external rotor, the radial relationships would be reversed. As already described, the end winding is the winding that is on the outside relative to the slot base and is the last winding in the area of ​​the slot opening. For an internal rotor, the end winding is the radially innermost winding; for an external rotor, it is the radially outermost winding.It can further be provided that the slot closure means has at least one guide element for axially guiding and / or positioning the temperature sensor in the stator slot radially between a radial underside of the slot closure means and a radial upper side of the end winding. In order to also guide the cables in the axial area around the temperature sensor and in particular also around the guide elements, it can be provided that the at least one guide element has at least one receiving groove for receiving at least one of the cables, and that the at least one receiving groove comprises undercuts for clipping in the cable. Preferably, two receiving grooves are provided next to one another in the circumferential direction so that both cables can be held and guided parallel to one another in the guide element.Furthermore, it can be provided that these undercuts have an assembly chamfer in the radial direction for careful insertion of the cable into the at least one receiving groove, whereby damage to the cable during assembly of the groove closure means and temperature sensor can be avoided. In a further development, it can be provided that the temperature sensor is arranged between the groove closure means and the end winding, and that the groove closure means exerts a radial force on the temperature sensor so that the temperature sensor is pressed radially against the end winding by the groove closure means. In this way, a uniform and consistent contact point can be established between the end winding and the temperature sensor over a relatively large surface area. The accuracy of the temperature signal increases.The radial position of the temperature sensor in relation to the windings in the stator slot, particularly in relation to the end winding, can be determined and guaranteed with particular precision. Since the stator slot contains a plurality of windings which generate heat due to the electrical control and their inherent resistance, this heat is distributed axially and radially in the stator or stator body. A hotspot for this heat is therefore to be expected in the winding which is radially closest to the slot opening. As described, this winding is referred to as the end winding. By fixing the temperature sensor directly on the outer surface of the end winding, the radial position of the temperature sensor is now determined so that it is located radially in the area of ​​the highest temperature. This increased radial accuracy of the temperature measurement means that a larger axial deviation of the temperature sensor can be tolerated.It can further be provided that the slot closure means, in the non-installed state, has at least one region that protrudes from a plane. In particular, the slot closure means accommodates the temperature sensor in this region in the 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 lies 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 that follows the stator surface. This means that the planes can be slightly curved in the circumferential direction.In an alternative or additional embodiment of the slot closure means, it has an axial extent that essentially corresponds to the axial extent of the stator body. The axial ends of the slot closure means define a straight line that passes through these two ends. When installed, this straight line runs parallel to the end winding and the stator axis. When installed, the regions of the slot closure means axially located between the axial ends lie on this straight line, or the straight line is located everywhere within the slot closure means between the ends. In order to exert a radial force on the temperature sensor, the slot closure means is radially preloaded when installed. For this purpose, the slot closure means is radially curved in the non-installed state, so that the straight line in this curved region no longer lies within the slot closure means.The orientation of this arcuate formation is designed such that the slot closure means is bent towards 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 through the stator body, so that the slot closure wedge is held in the plane parallel to the end winding by the undercut and the end winding, at least in the area outside the prestressed area. The prestressed area is prestressed in the direction of the end winding, resulting in a contact force for pressing the temperature sensor against the end winding. In this area, additional radial restriction, e.g. by an undercut, is not necessary.In this way, the interacting geometries and designs of the slot closure wedge and stator body can generate a radially acting force that, on the one hand, determines the radial position of the slot closure wedge and, on the other hand, ensures permanent and surface-wide contact with the temperature sensor on the end winding. Overall, this can increase measurement accuracy while simultaneously allowing axial deviation of the temperature sensor from the hotspot. To enable a uniform profile of the slot closure wedge when installed, the slot closure wedge is provided with a radially tapered area in the axial direction. In other words, the slot closure wedge becomes thinner in one axial area. The temperature sensor is arranged in this tapered area. In particular, the tapered area can be identical to the area protruding from a plane or prestressed area, or it can be a sub-area thereof.It may further be particularly preferred for the temperature sensor to be accommodated in a recess in the tapered region so that it faces the end winding, and at the same time the tapered region ensures that the surface of the slot closure wedge facing away from the end winding, i.e. its radial upper side, is flat. The tapered region is preferably radially thinnest in the region of the temperature sensor and thickens from there in the axial direction, in particular radially in both axial directions, until a standard thickness of the slot closure wedge is reached. The tapered region is selected so that it encompasses the region which, due to 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 completely with the protruding region or prestressed region.In the case of a slot-locking wedge, the protruding region preferably takes on an arcuate shape, which simultaneously has a radial thickness that continuously tapers in the axial direction, so that in the area where the arcuate shape connects to the remaining, non-protruding area of ​​the slot-locking wedge, the radial thickness corresponds to the standard thickness of the slot-locking wedge, which it has in the remaining axial areas. This allows for a stress-optimized design of the slot-locking wedge in a very confined space, while simultaneously saving material.In order to achieve an axial positioning of the temperature sensor between the slot closure means and the end winding that meets the requirements, it is further provided that the slot closure means has at least one guide element for axially guiding and / or positioning the temperature sensor in the stator slot between a radial underside of the slot closure element and a radial top side of an end winding of the windings, wherein the at least one guide element has an axial stop for contact with an axial end of the temperature sensor and is preferably formed integrally from the slot closure means. Since a plurality of windings are located in the stator slot, which generate heat due to the electrical control and their inherent resistance, this heat is distributed in the axial and radial directions in the stator or in the stator body.A hotspot for this heat is therefore to be expected in the winding that is radially closest to the slot opening. As already mentioned, this winding is referred to as the end winding. In an internal rotor motor, this is the radially innermost winding, in an external rotor motor, it is the radially outermost winding. By defining the axial position of the temperature sensor using the axial stop on the outer surface of the end winding, the axial position of the temperature sensor is set so that it lies within the required range, so that the signal-to-noise ratio is always above the threshold value, and the temperature sensor is axially as close as possible to the hotspot, i.e. the area of ​​the highest temperature. Furthermore, the axial stop can be used to define the axial position of the temperature sensor within a range of specified tolerances.The stop can also act as a guide aid or driver when inserting the slot closure means into the stator slot, whereby the temperature sensor is securely threaded axially into the stator slot. 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 this. Corresponding damage to the end winding, such as to the paint finish on the end winding, can be avoided. This radial underside of the at least one guide element has a curved or rising or oblique course in the non-installed state of the slot closure means, whereas in the installed state it lies flat on or parallel and spaced apart from the radial upper side of the end winding.In particular, there is no contact between the radial underside of the guide element and the radial upper side of the end winding in such a way that there would be a reaction on the course of the radial upper side of the slot closure means. The radial upper side of the slot closure means remains unaffected by the lack of interaction between the guide element and the end winding. In particular, it can be provided that the radial upper side of the slot closure means has an axially flat surface over its entire axial course in the installed state or is only slightly curved in the circumferential direction. A reaction of the guide element due to it being placed on the end winding could, for example, cause the slot closure means to be lifted off the end winding in the area of ​​the guide element.In order to effectively ensure a spacing between the guide element and the end winding, which helps to avoid damage to the end winding, it can be provided that the radial height h1, h2 of the at least one guide element is smaller than the radial height H of the temperature sensor. The radial height h1, h2 of the guide element is determined from the radial underside of the slot closure means. In this way, the temperature sensor in particular is reliably not influenced in its radial position relative to the end winding by the guide element(s), so that positioning of the temperature sensor is effected exclusively in the axial direction. In a further development, it can be provided that the cross section of the slot closure means increases axially outwards, starting from the at least one guide element.This enables a stable slot closure means with a defined, desired flexibility in the area of ​​the temperature sensor. The temperature sensor and the slot closure means can be securely inserted into the stator slot, and the temperature sensor can be held in the axial position. This can also be provided, in particular, if two guide elements are provided, each axially spaced from the temperature sensor. In a further development of the stator, it can be provided that two guide elements are provided axially spaced from one another on the slot closure means. The slot closure means can thus form a recess axially between the two guide elements for receiving the temperature sensor. A radially tapered area is also provided axially between the two guide elements. This design also supports the effect of the guide elements exclusively on the axial positioning or axial transport of the temperature sensor.The guide elements are prevented from (co-)determining the radial positioning of the temperature sensor. Stops on the guide elements in both axial directions enable the temperature element to be driven axially, and precise axial positioning can also be achieved within the tolerance range. The tolerance here is based on the difference between the axial distance of the guide elements and the axial length of the temperature sensor. To enable the temperature sensor to be connected in the installation space between the slot closure means and the end winding, it can be provided that the two cables, starting from the temperature sensor and ending at the axial end of the slot closure means, are guided through sensor grooves and / or receiving grooves without crossing, preferably parallel to one another. In this design, the sensor groove does not have to extend over the entire axial length of the slot closure means.In particular, in the area of ​​the temperature sensor and there in particular axially between the two guide elements, a sensor groove can be dispensed with entirely or it can be provided that the depth of the sensor groove is smaller than the radius or half the maximum width of the cable. A continuous transition of the sensor groove depth can be provided between guide elements and the area of ​​the slot closure means in which the sensor groove has a depth greater than the cable diameter. It can be provided that one of the cables is guided through the slot closure means in a first axial direction and a second cable in the opposite axial direction away from the temperature sensor. Preferably, both cables are guided axially through the slot closure means on the same axial side of the temperature sensor. Here, sensor grooves and receiving grooves are only present on one axial side of the slot closure means and in the guide element provided on this side.The other side of the slot closure means is then constructed without a sensor groove, and the guide element present there is constructed without a receiving groove. In a further development of the invention, it can be provided that the slot closure means is circumferentially guideless in the area of ​​the temperature sensor and is free of limitations for the temperature sensor, so that the temperature sensor is positioned circumferentially exclusively, preferably with a clearance fit, with the groove edge of the stator slot or with any insulation paper present. This makes it possible to save material for the slot closure means and, at the same time, to use existing limitations in the stator. Furthermore, unnecessary overdetermination of the position of the temperature sensor is avoided. A simpler design of the stator with slot closure means and temperature sensor is enabled.Even more material can be saved if the slot closure means in the area of ​​the temperature sensor is provided with a smaller width b in the circumferential direction than the standard width B in an axially further outwardly located area of ​​the slot closure means. By determining the circumferential position by the slot edge of the stator slot, or by the insulating paper that may be present there, further material can be omitted in the circumferential direction and the area of ​​the slot closure means for accommodating the temperature sensor can be designed in a more stress-optimized manner. At the same time, it can be provided that the width b of the slot closure means in the area of ​​the temperature sensor is smaller than the distance between the undercuts that close off the stator slot in the radial direction. This can, for example,A radial position closer to the slot opening is made possible for this slot closure means than with the other slot closure means, which do not accommodate a temperature sensor and have a width B over the entire axial length that is greater than the distance between the undercuts, whereby the stator teeth engage behind the entire axial area of ​​these slot closure means. The area between the guide elements can be designed overall in such a way that it is important for both axial and radial positioning and, at the same time, positioning in the circumferential direction is achieved by the stator body, in particular by the insulation paper and / or the stator slot.The geometric configuration of the slot closure means axially between the guide elements with reduced radial thickness and / or reduced width, in particular without radial spacers between the slot edge and / or insulation paper, while simultaneously increasing the thickness and width axially outside the guide elements, ensures a stress-optimized design of the slot closure means, which prevents the slot closure means from breaking due to high stresses. This accordingly supports the accuracy of the positioning of the temperature sensor in the radial direction in the area of ​​the hotspot, in the axial direction at a specified distance X from the hotspot, and in the circumferential direction secured by the edge of the stator slot. This precise positioning ensures the appropriate quality of the temperature sensor signal.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 combination of features just described, in particular the combination of features of claim 18, and which is characterized in that the threshold value is determined as a function of a first low-pass filter used to protect against interference signals, depending on the speed of the rotor, and / or a second low-pass filter used, depending on 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-to-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. This meansthe distance x can be reduced, thereby enabling a more precise temperature measurement in the area of ​​the expected hotspot. 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 controlling the windings are smaller than a factor of 5, preferably smaller than a factor of 100. In this case, a reliably measured signal from the temperature sensor can then be used to determine the temperature of the stator. Alternatively or additionally, it can be provided that the sampling rate of the temperature sensor is set as a function of the frequency of the inverter and / or the rotational speed of the rotor. This also allows the measurement to be carried out with less noise.When the slot closure means is installed, the temperature sensor can be additionally connected to the slot closure means, the end winding, the adjacent stator teeth, and any insulating paper present, in particular using a trickling resin, potting resin, or an adhesive. For this purpose, appropriate material is preferably introduced into the stator using a trickling process. An exemplary embodiment of the invention, to which the invention is not limited and from which further features according to the invention can arise, is illustrated in the following figures. They show: Fig. 1: a cross section through a stator, Fig. 2: an axially parallel section through a stator, Fig. 3: a section from the stator according to Fig. 1 with a slot closure wedge and temperature sensor, Fig. 4: a longitudinal section through a slot closure wedge with temperature sensor, Fig. 4b: a detailed section from Fig. 4, Fig. 5: a cross section through a slot closure wedge with temperature sensor, Fig.6: a plan view of the radial underside of a slot sealing wedge with temperature sensor, Fig. 7: a slot sealing wedge during an insertion process into the stator, and Fig. 8: the slot sealing wedge according to Fig. 7 in the stator. In Fig. 1 and Fig. 2, a stator 1 with a stator body 3 is shown for illustrative purposes. The stator body 3 is formed by a plurality of stator laminations or stator lamination packages 19 stacked in the axial direction. The axial direction extends along the axis 18. The stator 1 is essentially rotationally symmetrical to the axis 18. The stator 1 shown here belongs to an electric machine designed as an internal rotor. In the interior 14 of the stator 1, when the electric machine is assembled, there is a rotor (not shown here), which also 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 from a stator yoke 40. The stator teeth 4 are separated from one another in the circumferential direction by stator slots 5. Windings 6 of the stator 1 are located in the stator slots 5. The electric motor 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 creates a magnetic field rotating in the circumferential direction, which the rotor follows or leads. The stator teeth 4 are wound by the windings 6 in such a way that adjacent stator teeth 4 form a magnetic field with opposite polarization. The stator body 3 has an axial extension of length L with the axial center at L / 2.The stator lamination stacks 19 are formed or arranged essentially symmetrically to the axial center L / 2 in the axial direction. The alternating current of the windings 6 generates heat in the stator slots 5, which is absorbed by the stator yoke 40 and the stator teeth 4 and dissipated radially inward. This heat heats the stator body 3. In the axial direction, the heat within the stator slots 5 forms a hotspot of maximum heat at the axial center L / 2. The stator slots 5 have a radially outer slot base 7, which is located radially inward opposite a stator opening 8. The stator slots 5 are essentially completely filled by windings 6, as shown in Fig. 3. Fig. 3 shows a section from Fig. 2 with three stator slots 5. Each stator slot contains windings 6, extending from the slot base 7 to the slot opening 8.The radially innermost winding 6 is referred to as the end winding 20 because it closes off the windings 6 in the respective stator slot 5 to the outside. The stator slots 5 are lined on the inside with insulating paper 41 to insulate 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'. The heat generated can impair the function of the electric motor, even to the point of damage. A temperature sensor 10 is therefore provided to provide information about the temperature generated in the stator 1. This temperature sensor 10 is connected to an evaluation or control unit via cable 12. Depending on the temperature value determined, cooling of the electric motor or the electric motor itself is regulated accordingly. This can even lead to the electric motor being switched off and the stator current being interrupted.The most precise temperature measurement possible is therefore necessary. Due to the symmetry of the stator 1, measuring the temperature at just one location is usually sufficient. For this purpose, the middle slot locking wedge 9 shown accommodates the temperature sensor 10, which is clamped between the end winding 20 and the slot locking wedge 9. The slot locking wedge 9 exerts a radial force F1 on the temperature sensor 10, so that it rests flat against the end winding 20. The other slot locking wedges 9' of the stator 1 do not have a temperature sensor 10. However, this can be provided, for example, for redundancy reasons, to ensure reliability or to obtain a better average 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, which are formed through the stator body 3.The insulation papers 41 also have a corresponding paper section 42 extending inward in the circumferential direction. The stator slot 5 with the slot closure wedge 9, which accommodates the temperature sensor 10, is constructed identically to the other stator slots 5; undercuts 22 are also present here. The slot closure wedge 9, however, differs from the other slot closure wedges 9' in that it securely accommodates and positions the temperature sensor 10 and applies it to the end winding 20. This construction of the slot closure wedge 9 is shown and can be seen more clearly in Figures 4 to 7. The construction of the slot closure wedge 9 causes it to exert the radial force F1 on 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 electric machine.Due to the design of the slot closure wedge 9, the radial upper side 43 of this slot closure wedge 9 lies radially further in the area of ​​the slot opening 8 and thus closer to the rotor than the radial upper sides 43' of the other slot closure wedges 9'. Fig. 4 shows the slot closure wedge 9 with temperature sensor 10 in the non-installed state. This is a sectional view along its axial extent. The slot closure wedge 9 is long enough in the axial direction that it can fill or close a slot opening 8 in the axial direction. The axial extent essentially corresponds to the effective axial length of the stator 1 and thus the length L of the stator body 3. The slot closure wedge 9 accommodates two cables 12 that connect the temperature sensor 10 to electronics (not shown here).The electronics can include an evaluation unit for evaluating the sensor signal and / or a regulation or control unit for regulating and / or controlling a cooling system, the stator current, or the electric motor that accommodates the stator. The cables 12 are fed to one axial end of the slot closure wedge 9 and connected to the temperature sensor 10. There are no cables 12 at the other axial end of the slot closure wedge 9. In the slot closure wedge 9, the cables 12 are guided in sensor grooves 11 up to a first guide element 26. 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, the cables 12 are practically not guided at all. They can still lie in a bowl-shaped recess 44 in the radial underside 24 of the slot closure wedge 9. These bowl-shaped recesses 44 with cables 12 arranged therein are shown in Fig.6.The temperature sensor 10 is located axially between the first guide element 26 and a second guide element 26b in a recess 31 of the slot closure wedge 9. This recess 31 is located axially within a tapered region 23 of the slot closure wedge 9. Within the tapered region 23, the slot 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 slot closure wedge 9. In this remaining region, it has a standard thickness D>d. The tapered region 23 extends axially, starting from the temperature sensor 10, to behind the two guide elements 26. This tapered region 23 initially saves material in the slot closure wedge 9. The slot closure wedge 9 is at its thinnest directly in the region of the temperature sensor 10. These savings provide space for the temperature sensor 10 and also for the guide elements 26.On the other hand, this creates an arcuate shape of the slot closure wedge 9 precisely in this tapered region 23, so that the slot closure wedge 9 is bent in this tapered region 23 towards its radial underside 24. For better illustration, a line 46 is drawn in Fig. 4, which passes through the two axial ends of the slot closure wedge 9. Outside the tapered region 23, the radial upper side 43 of the slot closure wedge 9 lies on this line 46. In the tapered region 23, the slot closure wedge 9 protrudes from the plane of this line 46, ie there is a distance between the line 46 and the radial upper side 43 in this tapered region 23.This distance increases from the areas with the standard thickness D up to the temperature sensor 10, so that the radial upper side 43 and thus also the radial underside 24 of the slot closure wedge 9 have an arc-shaped course in the direction of the radial underside 24. With respect to the end winding 20 (not shown here), the slot closure wedge 9 is bent in the direction of this end winding 20. This course of the slot closure wedge 9, which protrudes from the plane of the line 46, then enables a radial contact force F1, originating from the slot closure wedge 9, onto the temperature sensor 10 when the slot closure wedge 9 is installed, so that the temperature sensor 10 is pressed against the end winding 20. Due to the arc-shaped course, the slot closure wedge 9 has a preload in the installed state in the relaxed, i.e. non-inserted, state, with which preload the temperature sensor 10 is pressed against the end winding 20.In the installed state, the slot closure wedge 9 is preloaded to such an extent that its radial upper side 43 essentially follows the line 46 over the entire axial length. In Fig. 4b, a section of the radially tapered region 23 from Fig. 4 is shown enlarged for illustrative purposes. The cables 12 run within sensor grooves 11 up to the beginning of the tapered region 23. These limit the mobility of the cables 12 in both the radial and circumferential directions. This is achieved by means of an overlap of the groove walls. As can be seen in Fig. 4b, the circumferential limitations for the cables 12 are reduced in the axial course of the slot closure wedge 9, while the thickness of the slot closure wedge 9 decreases from a standard thickness D to thickness d. When the thickness of the slot closure wedge 9 assumes approximately the smallest extent, the slot closure 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 24b, which has a thickness that increases axially towards the stop 27. The surface profile of the radial underside 24b is correspondingly inclined towards the temperature sensor 10. This inclination is present in the non-installed state and in particular on the radial underside 24 of the slot closure wedge 9, which results in a rising radial underside 24b. The inclination is designed such that the radial underside 24b is essentially parallel to the radial top side 25 of the end winding 20 when installed. Axially inward, 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 inserting the slot locking wedge 9.As can be seen in Fig. 4, the second guide element 26 also has a steep surface profile of the radial underside 24b and a stop 27. When installed, the stops 27 of the two guide elements 26 and 26b act as positioning means for the axial positioning of the temperature sensor 10. The axial position of the temperature sensor 10 is thus determined by the axial distance between the two guide elements 26, 26b. Their tolerance is determined by the larger axial distance between the guide elements 26, 26b in relation to the axial extent of the temperature sensor 10. In the axial area between the stops 27, there are no limitations in the circumferential direction, neither for the temperature sensor 10 nor for the cables 12. The cables 12 are not fixed by the slot closure wedge 9 in the circumferential direction or in the radial direction, particularly in the area between the stop 27 of the first guide element 26 and the temperature sensor 10.A cross-section through the slot closure wedge 9 along the section line AA from Fig. 4b is shown in Fig. 5. This is a spatial representation in which the axial area between the first guide element 26 and an axial end of the slot closure wedge 9 can also be seen. In the tapered area 23, the width of the slot closure wedge 9 is reduced from the standard width B to the reduced width b. Starting from a standard width B, the width in the axial area after the first guide element 26 is reduced to a smaller width b. In the area of ​​the standard width B, the cables 12 are guided in sensor grooves 11 with an excess, so that they are fixed in the circumferential and radial directions. The slot closure wedge 9 forms a web 47 between the sensor grooves 11.The web 47 projects radially beyond the wing-like projections 48 adjoining the sensor slots 11 in the circumferential direction, so that in the installed state the web 11 rests on an end winding 20, while a small gap exists between the wing-like projections 48 and the end winding 20. When the stator 1 is filled with insulating compound, such as resin, this slot and the cables 12 in the sensor slots 11 that are thereby accessible for the casting or trickling material are also securely cast. By reducing the width B, b of the slot closure wedge 9 with a simultaneous decrease in the radial thickness D, d, the overall cross-section of the slot closure wedge 9 decreases, which means an optimization of the stress with regard to the contact force F1 exerted on the temperature sensor 10 by the shape of the slot closure wedge 9. The first guide element 26 is also shown in Fig. 5.This has receiving grooves 28 designed to accommodate the cables 12, which include undercuts 29 for radially securing the cables 12 in the first guide element 26. The undercuts 29 have radially effective mounting chamfers 30, which enable easy and secure clipping in of the cables 12. This is particularly advantageous when the cables 12 have an outer insulating layer. The reduction in the width of the slot closure wedge 9 from a standard width B to a reduced width b is clearly shown again in Fig. 6. Fig. 6 shows a plan view of the slot closure wedge 9 from the radial upper side 43. The sensor grooves 11 and cables 12 are located on the radial underside 24. Fig. 7 shows how the slot closure wedge 9 is inserted axially into a stator slot 5. In the stator slot 5 there are windings 6 with the end winding 20 radially inward, ie in the area of ​​the slot opening 8.The end winding 20 has a radial upper side 25, which here is already partially covered by the slot closure wedge 9. The radial underside 24 of the slot closure wedge 9 and the radial underside 24b of the second guide element 26b are located partially in the stator slot 5 or in the region of the winding overhang 49 at one axial end of the stator body 3. The tapered region 23 still has the pre-bent structure, as shown and described in Fig. 4. Upon further axial insertion of the slot closure wedge 9, the radial underside 24b of the second guide element 26b will 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 24b of the second guide element 26b, the slot closure wedge 9 is already slightly displaced in this area in the direction of the slot opening 8, ie radially inward, and the arcuate area is raised against a restoring force.As the process continues, the temperature sensor 10 also enters the stator slot 5 and comes into contact with the radial upper side 25 of the end winding 20. It is possible that the temperature sensor 10 experiences an axial force from the axial stop 27 of the first guide element 26, whereby it is pushed axially into the stator slot 5. Since the temperature sensor 10 has a radial height H that is greater than the radial height h2 of the second guide element 26b, or the stop 27' of the second guide element, the radial underside 24b of the second guide element 26b lifts off the radial upper side 25 of the end winding 20, so that a gap forms here. When the slot closure wedge 9 is pushed in further, there is no further contact between the end winding and the radial underside 24 of the slot closure wedge 9 or the radial underside 24b of the first guide element 26 within the tapered area 23.This is also due to the height h1 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 slot closure wedge 9 is pushed with its region of standard thickness D into the stator slot 5 does at least the web 47 between the sensor slots 11, as shown in Fig. 5 and designed for this purpose, rest on the end winding 20 or its radial upper side 25. Gaps (of different thicknesses) now exist between the radial upper side 25 of the end winding 20 and the radial undersides 24b of the guide elements 26 and 26b and the radial undersides 24 of the wing-like formations 48. In the axial region between the guide elements 26 and 26b, the radial underside 24 of the slot closure wedge 9 is located completely at a distance of the radial height H of the temperature sensor 10 from the radial upper side 25 of the end winding 20.In this area, there are no further structures of the slot closure wedge 9 between the cables 12 and the temperature sensor 10 on the one hand, and the insulating paper 41 or the inside of the stator slot 5 on the other. In this area with the smaller width b of the slot closure element 9, the temperature sensor 10 and the cables 12 are circumferentially delimited exclusively by the stator slot 5 or by the insulating paper 41. During the final potting of the stator 1 with an insulating material, these gaps and free spaces 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 closure wedge 9 inserted into the stator slot 5 is shown in Fig. 8.The undersides 24b of the two guide elements 26 are each spaced apart from the radial upper side 25 of the end winding 20, with the radial underside 24b of the second guide element 26b being spaced further apart than the radial underside 24b of the first guide element 26. The curvature of the slot closure wedge 9 visible in Fig. 7, particularly in the tapered region 23, is eliminated here, so that the radial upper side 43 now essentially follows the radial upper side 25 of the end winding everywhere. In the regions of the standard width B, the slot closure wedge 9 is prevented from moving radially inward by the undercuts 24, as described in Fig. 3. Since the slot closure wedge 9 is deformed in the tapered region 23 in the radially inward direction, the desired contact pressure F1 is now present radially outward, which presses the temperature sensor 10 against the end winding 20.The width b of the slot closure wedge 9 can be smaller than the distance between the undercuts 22, whereby the slot closure wedge 9 is located further radially inward than the other slot closure wedges 9' without the temperature sensor 10. At the same time, forces are also exerted radially outward on the slot closure wedge 9 by a correspondingly shaped paper section 22, as shown in Fig. 3. The temperature sensor 10 shown in Fig. 8 is arranged at a distance X from the axial center L / 2 of the stator body 3 in the stator slot 5. The distance X here refers to the part of the temperature sensor 10 which represents at least the effective point in the axial direction for temperature measurement for the temperature sensor 10. The distance X is greater than 0 and less than L / 2, whereby a displacement of the temperature sensor 10 away from the axial center L / 2 with the highest temperature to an area further axially outward in the direction of the winding overhang 49 is described.The temperature sensor 10 now measures the temperature of the stator body 3 not in the area of ​​the hotspot, as ideally desired, but at an axial distance from it. As shown in Fig. 5, the cables 12 for contacting the temperature sensor 10 are arranged parallel and without crossings in the sensor slots 11. There is no electromagnetic shielding of the cables 12, and the alternating electric field or magnetic field of the stator 1 caused by the applied alternating frequency of the stator current induces a first interference voltage in the cables 12. The rotating magnetic field of the rotor magnets causes a second interference voltage in the cables 12 due to the unshielded induction. The longer the sections of the cables 12 that are located axially within the stator body 3, the greater the interference signals in the cables 12, so that measurement or evaluation of the measurement signals of the temperature sensor 10 is impaired or becomes impossible.In order to achieve the most accurate temperature measurement possible in the area of ​​the hotspot, the distance X is selected such that the signal-to-noise ratio of the measurement signal lies in a range that reliably enables measurement or temperature determination and, at the same time, the measured temperature has the smallest possible deviation from the temperature expected in the hotspot at L / 2. In this way, the distance X is specified by setting a limit value for the signal-to-noise ratio. In the evaluation device, measuring device, or control device (not shown), further low-pass filters can be provided which, depending on the rotation frequency of the rotor and / or the alternating frequency of the inverter for the stator power supply, filter out interference signals at correspondingly higher frequencies. This can improve the signal-to-noise ratio orthe limit value for the signal-to-noise ratio before the low-pass filter(s) can be reduced so that overall a smaller distance X is possible and the measured temperature is closer to the actual temperature at the hotspot, i.e. at the axial center L / 2. A further improvement in the signal from the temperature sensor is achieved by setting the sampling rate when reading the temperature sensor as a function of the frequency of the inverter and / or the speed of the rotor. This setting is chosen so that the noise is reduced or the accuracy of the signal is improved. In a trickling process following the insertion of the slot sealing wedge 9, the temperature sensor 10 and the slot sealing wedge 9 are connected in a form-fitting and material-fitting 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 with a predetermined axial distance from the hotspot, this distance being within narrow predetermined tolerances.

[0002] List of reference symbols Stator Stator body Stator teeth Stator slots Windings Slot base Slot opening , 9' Slot closure wedge 0 Temperature sensor 1 Sensor slot 2 Cable 4 Interior 5 Motor vehicle 6 Drive train 7 Control unit 8 Axle 9 Stator laminated core 0 End winding 1 Protruding area 2 Undercut 3 Tapered area 4, 24b Radial underside 5 Radial top side 6 First guide element 6b Second guide element 7 Axial stop 8 Receiving groove 9 Undercuts 0 Mounting chamfer 1 Recess 40 Stator yoke 41 Insulating paper 42 Paper section 43, 43' Radial top side 44 Bowl-shaped recess 45 Section 46 Line 47 Web 48 Wing-like projections 49 Winding head F1 Contact pressure d Radial thickness D Standard thickness H, h1, h2 Radial height b Width B Standard width AA Section line X Distance L Length of stator L / 2 axial center

Claims

1. Stator (1) for an electrical machine, comprising an axially extending stator body (3) with a plurality of circumferentially distributed stator teeth (4), stator slots (5) extending between the stator teeth (4) in the axial direction through the stator body (3), windings (6) arranged in the stator slots (5), a radially outermost end winding (20) of the windings (6), 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), and with a temperature sensor (10) which is arranged on or in one of the slot closure means (9), characterized in that the temperature sensor (10) is two cables (12) are connected to a control device and / or an evaluation device,the two cables (12) are guided without crossing, preferably parallel, in and / or on the slot closure means (9), the stator body (3) has an axial extent L, and the temperature sensor (10) is positioned at a distance x from the axial center L / 2 of the stator body (3), wherein the distance x is greater than zero and less than L / 2 and is determined by the signal-to-noise ratio of the temperature signal read out by the control device and / or evaluation device being above a predetermined threshold value.

2. Stator (1) according to claim 1, characterized in that the slot closure means (9) has at least one sensor slot (11) for receiving at least one of the cables (12), wherein the sensor slot (11) has a transition fit for receiving the at least one cable (12).

3. Stator (1) according to claim 2, characterized in that the radial depth of the sensor groove (11) is deeper than the diameter or the maximum width of the, at least one cable (12), so that the opening of the sensor slot (11) is closed by the end winding (20) by resting against the latter.

4. Stator (1) according to one of claims 2 or 3, characterized in that the slot closure means (9) has at least one guide element (26, 26b) for axially guiding and / or positioning the temperature sensor (10) in the stator slot (5) radially between a radial underside (24) of the slot closure means (9) and a radial upper side (25) of the end winding (20), the at least one guide element (26) has at least one receiving groove (28) for receiving at least one of the cables (12), and the at least one receiving groove (28) comprises undercuts (29) for clipping in the cable (12).

5. Stator (1) according to claim 4, characterized in that the undercuts (29) have a mounting bevel (30) in the radial direction for the careful insertion of the cable (12) into the at least one receiving groove (28).Stator (1) according to one of claims 1 to 5, characterized in that the temperature sensor (10) is arranged between the slot closure means (9) and the 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).

7. Stator (1) according to claim 6, characterized in that the slot closure means (9) in the non-installed state has at least in some areas a region (21) protruding from a plane, which has a surface facing away from the end winding (20) which, 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) facing away from the end winding (20), and wherein preferably the temperature sensor (10) is in a recess (31) of the region (21) facing the end winding (20). is received.

8. Stator (1) according to claim 7, 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 through the stator body (3), so that the protruding region (21) is forced by the undercut (22) and the end winding (20) into the plane parallel to the end winding, thereby resulting in a contact force (F1) for pressing the temperature sensor (10) onto the end winding (20). 9.Stator (1) according to claim 8, characterized in that the slot closure wedge (9) has a region (23) tapering in the radial direction in the axial direction, the temperature sensor (10) is arranged in the tapered region (23), the tapered region (23) is radially thinnest in the region of the temperature sensor (10) and, proceeding therefrom, thickens radially in the axial direction, in particular in both axial directions, until a standard thickness (D) of the slot closure wedge (9) is reached. 10.Stator (1) according to at least one of the preceding claims, characterized in that the slot closure means (9) has at least one guide element (26) for axially guiding and / or positioning the temperature sensor (10) in the stator slot (5) radially between a radial underside (24) of the slot closure means (9) and a radial upper side (25) of the end winding (20), wherein the at least one guide element (10) has an axial stop (27) for contact with an axial end of the temperature sensor (10) and is preferably formed integrally from the slot closure means (9).

11. Stator (1) according to claim 10, 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) in the non-installed state. the slot closure means (9) has a curved or rising, or oblique course in the axial direction and, in the installed state, lies flat on or parallel to the radial upper side (25) of the end winding (20), so that the radial upper side (43) of the slot closure means (9) remains unaffected by an interaction between the guide element (26) and the end winding (20).

12. Stator (1) according to claim 11, characterized in that the radial height (h1, h2) of the at least one guide element (26) is smaller than the radial height H of the temperature sensor (10).

13. Stator (1) according to one of claims 10 or 11, characterized in that the cross section of the slot closure means (9) increases axially outwards starting from the at least one guide element (26). 14.Stator (1) according to one of claims 10 to 13, characterized in that two guide elements (26, 26b) are provided axially spaced from one another on the slot closure means (9), the slot closure means (9) has a recess (31) between the two guide elements (26, 26b) for receiving the temperature sensor (10), and a radially tapered region (23) of the slot closure element (9) is provided axially between the two guide elements (26, 26b).

15. Stator (1) according to one of the preceding claims, characterized in that the slot closure means (9) is guideless in the circumferential direction in the region of the temperature sensor (10) and is free of restrictions for the temperature sensor (10), so that positioning of the temperature sensor (10) in the circumferential direction takes place exclusively, preferably with a clearance fit, with the groove edge of the stator slot (5). 16.Stator (1) according to claim 15, characterized in that the slot closure means (9) in the region of the temperature sensor (10) has a smaller width b in the circumferential direction than the standard width B in an axially further outwardly lying region. surrounding area of ​​the slot closure means (9).

17. Stator (1) according to claims 9 and 17, characterized in that the width b of the slot closure wedge (9) in the area of ​​the temperature sensor (10) is smaller than the distance between the undercuts (22) that close off the stator slot (5) in the radial direction.

18. Method for determining a stator temperature of an electric motor, comprising a rotor and a stator according to one of the preceding claims, characterized in that the threshold value is determined as a function of a first low-pass filter used against interference signals as a function of the 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 one of the preceding claims or according to claim 18, 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 controlling the windings (6) are smaller than a factor of 5, preferably smaller than a factor of 100 in relation to the signal of the temperature sensor (10).

20. Method according to one of claims 18 or 19, characterized in that the sampling rate of the temperature sensor (10) is determined as a function of the frequency of the inverter and / or the rotational speed of the rotor.

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