Method for manufacturing stator of electric motor

Abstract

The invention relates to a method for producing a stator (2) of an electric rotating machine (1) by arranging a winding system (3) in a magnetic conductor, in particular an axially stacked laminated core (4), in a slot (6) facing an inner bore (5) such that a respective winding head (10) is formed on an end face of the magnetic conductor, connecting the magnetic conductor to an in particular heat-conducting housing (12) in a rotationally fixed manner, the invention relates to a stator (2) comprising a housing (12), in particular a laminated core (4), said housing (12) extending axially on both sides of the laminated core (4) of the stator (2) at least as far as an axially outer edge of a respective winding head (10), such that a respective circumferential gap (14) is formed in the region of the winding head (10) between a radially outer side (16) of the winding head (10) and an inner edge (17) of the housing (12), and filling the circumferential gap (14) between the radially outer side (16) of the winding head (10) and the inner edge (17) of the housing (12) with a potting mixture (18) having at least one rheologically optimized additive such that the winding head (10) is thermally connected to the housing (12).

Description

Technical Field

[0001] The present invention relates to a method of manufacturing a stator of an electric rotating machine, an electric rotating machine having such a stator, and applications of such an electric rotating machine. Background Art

[0002] The electric motor has a stator with a magnetic conductor. In this magnetic conductor, in particular in an axially stacked lamination stack, a winding system is arranged in essentially axially extending slots, which is directed toward the rotor. The winding system causes the rotor to rotate during operation of the electric motor by electromagnetic interaction with the rotor. The winding system has electrical conductors, for example round enameled wires. These wires are positioned in the corresponding slots in various ways, for example by an insertion method or a dripping method. The winding heads are formed on the end faces of the stator.

[0003] The lacquer on the conductor corresponds to the primary insulation in the field of application of low-voltage motors up to 1 kV, for example. However, further impregnation or potting is usually performed for further mechanical reinforcement and passivation against external influences.

[0004] For cost reasons, electric rotating machines in the low voltage range of <1 kV and power classes between 0.5 kW and 2000 kW are impregnated by cold or hot impregnation (e.g., galvano-UV method). In this process, the stator is immersed in a basin with liquid resin and then thermally cured. The geometric center area of ​​the winding in the slots of the stator is mainly filled with resin, which reinforces it, additionally electrically insulates it and thermally connects it to the laminated core.

[0005] The winding heads, i.e. the necessary conductor bundles, are located in the end face region of the stator, which connect the active regions of the conductors in the slots to each other. Before the impregnation process, the winding heads are again equipped with surface insulation (e.g. paper inserts) to electrically isolate the different electrical phases of the motor from each other. Furthermore, the winding heads are pressed, compressed and tied to conform to the predetermined geometric dimensions and not to exceed a predetermined overall axial length.

[0006] The thermal connection of the winding head to the housing is provided only via an intermediate area filled with air. Therefore, the heat dissipation from the winding head via the thermal contact transition from the winding to the air and further from the air to the housing occurs extremely inadequately. This situation constitutes a critical factor and a factor that limits the power rating of the electric machine, because so-called hot spots can occur in particular in the winding head. In the winding system, due to the relatively high currents and the additional geometrically and mechanically necessary compression in the winding head or the fixing of the winding system, areas are generated that are significantly hotter than inside the stator slots. In the slots of the stator, the heat dissipation via the surrounding iron sheets is very effective.

[0007] Inside low-voltage motors, the possible heat dissipation of the winding heads is achieved by impellers that are mounted directly on the shaft and have a constant speed, and these impellers drive air convection in proportion to the motor speed, so that the winding heads are surrounded by a convective air flow. However, this ventilation again has a negative impact on the performance and efficiency of the motor and is complex and relatively cost-intensive to manufacture and produce.

[0008] If better heat dissipation is required due to higher power requirements on the electric motor, the winding head must be thermally connected to the housing by "winding head potting".

[0009] In addition to the material costs, the process costs for winding head potting are also clearly more significant, since the impregnated stator must be removed from the standard production process and prepared for winding head potting (first one side, then the other) through a potting mold. An internal mandrel is inserted into the inner bore of the stator in a form-fitting manner and the stator may be heated to a higher temperature (e.g. 80° C. to improve the fluidity of the potting mixture). The potting mixture is then poured into the winding head container surrounded in this way. The mixture is then hardened for several hours at approximately 150° C., for example in a hot air oven. After hardening (and cooling), the other side of the winding head is also treated in the same way.

[0010] After these two separate processes, the potting body thus surrounds both winding heads radially inside and radially outside, whereas in a closed motor the heat flow is mainly radially outwards towards the housing. Complete encapsulation is more of a process phenomenon, since the inner mandrel serves as the housing wall for the potting and must then be removed and cleaned.

[0011] Overall, this is a very complex manufacturing process that requires time, energy and material costs. In addition, this manufacturing process results in unnecessary materials in the motor that are irrelevant to the work of the motor.

[0012] An electric motor is known from DE 693 07 422 T2 which shows a completely cast winding system using a core.

[0013] DE 199 57 942 C1 discloses a high-frequency motor spindle, the winding head of which is surrounded by a U-shaped hollow body, wherein the free space between the winding head and the hollow body is cast.

[0014] DE 199 02 837 C1 discloses a rotating electrical machine, the winding heads of which are thermally coupled to a supporting body via a thermal bridge, wherein the thermal bridge has a solid ring and a potting resin body.

[0015] However, the listed known solutions for heat dissipation of winding heads of stators of electric rotating machines are relatively complex, in particular when it comes to electric motors that need to be produced in large quantities. Summary of the invention

[0016] Based on this, the object of the present invention is in particular to create an electric motor which has sufficient cooling, in particular good heat dissipation of the overwindings of the stator of the electric motor, with relatively low production outlay.

[0017] The solution to the proposed object is achieved by the method for manufacturing a stator for an electric rotating machine by means of the following steps:

[0018] - arranging the winding system in a magnetic conductor, in particular an axially stacked lamination stack, in a slot facing the inner opening so that a corresponding winding head is produced at the end face of the magnetic conductor,

[0019] - connecting the magnetic conductor to a particularly heat-conducting housing in a rotationally fixed manner, wherein the housing extends axially on both sides of the stator laminated core at least to the axially outer edge of the respective overwinding, so that in the region of the overwinding a circumferential gap is produced between the radial outer side of the overwinding and the inner edge of the housing,

[0020] - filling the circumferential gap between the radial outer side of the winding head and the inner edge of the housing with a potting compound having at least one rheology-optimizing additive, so that a thermal connection is achieved between the winding head and the housing

[0021] The stated object is also achieved by an electric rotating machine having a stator with a magnetic conductor, in particular an axially stacked laminated core, wherein a winding system is arranged in slots pointing toward an inner opening of the stator, the winding system forming a winding head at the end face of the magnetic conductor.

[0022] - wherein a rotationally fixed connection is provided between the magnetic conductor and the housing, which is in particular heat-conducting,

[0023] wherein the housing extends axially on both sides of the magnetic conductor of the stator at least to the axial outer edge of the corresponding winding head,

[0024] wherein in the region of the winding head the circumferential gap between the radial outer side of the winding head and the inner edge of the housing is filled with a potting compound having at least one rheology-optimizing additive, so that the winding head is thermally connected to the housing,

[0025] - and having a rotor, wherein the stator and the rotor are separated by an air gap.

[0026] The entirety of the electrical conductors including any insulation is considered to be the winding system of the stator. The conductors can be formed coils, round wires or flat wires with or without insulation. This also includes single-phase, three-phase or multi-phase systems. Likewise, winding technology includes tooth coil technology and string windings or lap windings. The decisive factor is always the direct thermal coupling of the winding head formed by any winding system to the housing.

[0027] According to the invention, the winding head is now thermally connected to the housing surrounding the winding head. This is achieved by a directed distribution process of a heat-conducting, flowable mixture into the circumferential gap between the winding head and the housing. The heat-conducting potting mixture is characterized by the following process-optimized properties.

[0028] The potting compound is a molding material (reactive resin, such as epoxy resin, polyurethane or polyester) filled with thermally conductive particles. Depending on the required thermal conductivity and the required price level of the molding material, the filler particles, especially made of quartz powder, fused quartz, boron nitride or aluminum oxide, etc., are dispersed as microparticles in the matrix (reactive resin) with an optimized particle size distribution, so that a molding compound that is as fluid and flowable as possible remains. The filling rate of the filler in the matrix is ​​between 20 volume percent and 70 volume percent, which depends on the required fluidity at the processing temperature.

[0029] In addition to the filling with the above-mentioned thermally conductive particles, the potting mixture is also provided with a rheologically optimized additive. This additive causes the fluidity of the potting mixture to assume thixotropic and structurally viscous properties, and therefore when the shear rate is increased (which is achieved by an automatic dispenser, a metering unit), its viscosity decreases significantly and then returns to a significantly higher viscosity at a low shear rate. Thus, a metering unit equipped for this purpose can be used to fill a vertically placed stator to gradually fill an area, which is in particular the gap between the winding head and the housing. Due to the shear forces that occur during the dispensing, the flowing potting mixture reduces its viscosity, so that it is evenly distributed in the target area and surrounds the individual wires around the winding head in a form-fitting manner.

[0030] As the flow progresses slower and slower between the slot outlets, the viscosity increases due to the reduced shear forces, which causes the flow front to self-solidify between the slot outlets.

[0031] Thus, without any additional housing being required, an inner core shaft of the inner bore of the stator fills / pots the intermediate portion between the winding head and the housing.

[0032] A typical example of a thixotropic additive is fumed silica (silica gel), which is dispersed into the potting compound (0.1 wt. % to 1 wt. %) to obtain these desired properties.

[0033] Another material property of the potting mixture is that it is a two-component reaction resin, which is mixed in situ in the metering unit (resin and hardener components). The potting mixture is therefore ensured within a relatively short time (several hours to only a few minutes) without any further temperature input settings. Due to the formation of the chemical network, the base viscosity of the potting mixture increases, so that the production process is not interrupted and work can continue on the stator or motor.

[0034] The introduction of temperature into this process would reduce the viscosity and is therefore not possible, since otherwise the potting mixture would be transferred in particular between the outlets of the grooves without a housing or an inner mandrel and flow into the inner radius of the stator, ie the inner bore.

[0035] The goal is then to cure the stator in the housing at room temperature within 24 hours, which can be achieved, for example, by using a two-component epoxy resin containing an amine curing agent component.

[0036] With the invention presented here, the process of thermally connecting the winding head to the housing is significantly more cost-effective in terms of cycle time, energy input (room temperature) and process complexity than using conventional connections known from the prior art.

[0037] Thus, at the same electrical and thermal load, the realization of electric motors with higher power ratings or longer service life can be produced significantly more cost-effectively.

[0038] According to the invention, the combination of the following parameters leads to tool-free potting of the stator of an electric motor.

[0039] The potting compound is thixotropic and highly filled, thus achieving a high base viscosity under shear and an even higher static viscosity after standing for a few seconds / minutes. This allows the potting compound to flow without pores and fit snugly into the area between the winding head outer diameter and the housing, the area between the slot outlets being filled, a "solidified" flow front being generated due to the rheology, so that no tooling in the form of a jacket-shaped potting mold is required in the stator bore area (i.e. no overflow of potting compound is sealed at the inner diameter of the winding head).

[0040] The potting material consists of a highly reactive system which at least gels at room temperature and thus loses its fluidity (preferably 2K, ideally hardens within hours / days). This avoids the need for elevated temperatures for gelling / curing, which inevitably leads to a decrease in viscosity and the need for a sealing potting mold. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The invention and its further advantageous embodiments will be explained in detail with the aid of an exemplary embodiment shown in principle, in which:

[0042] Figure 1 shows a longitudinal section of an electric rotating machine in principle,

[0043] Figure 2 shows a side view of the stator in the housing,

[0044] Figure 3 shows a perspective partial view of the stator in the housing,

[0045] Figure 4 , Figure 5 A further housing embodiment is shown. DETAILED DESCRIPTION

[0046] It should be pointed out that terms such as "axial", "radial", "tangential" etc. refer to the axis 7 used in the corresponding figures or in the examples described in the respective case. In other words, the axial, radial and tangential directions always refer to the axis 7 of the rotor 19 and therefore to the corresponding symmetry axes of the stator 2. Therein, "axial" describes a direction parallel to the axis 7, "radial" describes a direction perpendicular to the axis 7, towards or away from it, and "tangential" is a direction circumferentially around the axis 7 at a constant radial distance from the axis 7 and in a constant axial position. The term "circumferentially" is synonymous with "tangential".

[0047] With respect to a region, eg a cross-sectional region, the terms "axial", "radial", "tangential" etc. describe the orientation of the normal vector to the region, ie the vector perpendicular to the relevant region.

[0048] In the term "coaxial components", for example, coaxial components such as rotor 19 and stator 2 are understood here as components having the same normal vectors, so that the planes defined by the coaxial components are parallel to each other. Furthermore, the term should include coaxial components whose center points are located on the same axis of rotation or axis of symmetry. However, these center points can be located at different axial positions on the axis and thus the mentioned planes have a distance greater than 0. The term does not require that the coaxial components have the same radius.

[0049] The term "complementary" when referring to two components that "complement" each other means that their shapes are designed so that one component can be placed preferably completely in the component that complements it, so that the inner surface of one component and the outer surface of the other component are in contact seamlessly or ideally over their entire surface. Thus, in the case of two complementary objects, the shape of one object is determined by the shape of the other object. The term "complementary" can be replaced by the term "inverse".

[0050] For the sake of clarity, sometimes not all components are labeled with reference symbols in the figures when a component appears multiple times.

[0051] The described embodiments can be combined arbitrarily. Likewise, individual features of the corresponding embodiments can also be combined with one another without departing from the essence of the invention.

[0052] The entirety of the electrical conductors including any insulation is considered to be a winding system 3 of the stator 2. The conductors can be formed coils, round wires or flat wires with or without insulation. This also includes single-phase systems, three-phase systems or multi-phase systems. Likewise, winding technology includes tooth coil technology and string windings or lap windings. The decisive factor here is that the winding head 10 formed by any winding system 3 must be directly thermally coupled to the housing 12.

[0053] Figure 1 The schematic longitudinal section of an electric rotating machine 1 is shown, which is fixed in a rotationally fixed manner in a housing 12. The stator 2 is designed as a magnetic conductor, in particular as a laminated core 4, which has a winding system 3 in a slot 6 pointing toward an air gap 15 of the electric motor 1. The winding system 3 forms a winding head 10 with a flange 24 and a winding neck 11 on the respective end face of the stator 2. The winding neck 11 is the section of the winding head 10 which forms the section of the winding system 3 immediately after leaving the slot 6, wherein the electrical conductor still extends substantially axially, before which the electrical conductor forms the flange 24.

[0054] The winding head 10 of the winding system 3 has an axial extension 13, which corresponds to the subsequent filling height of the potting compound 18. Between the inner edge 17 of the housing 12 and the outer side of the winding head 10 of the winding system 3 there is a gap 14 which is filled with the potting compound 18 described in detail later.

[0055] A rotor 19 is arranged at a distance from the stator 2 by an air gap 15, which is connected to the shaft 8 in a rotationally fixed manner and is mounted rotatably about the axis 7. In this case, the rotor 19 is laminated and has a short-circuit cage 20 arranged in the laminated core. The housing 12 has ribs 21 at least in places on the outer circumference.

[0056] The gap 14 is now provided with a potting compound 18 in its axial extension 13, so that at least the outer side of the winding head 10 of the winding system 3 is thermally well connected to the housing 12. Due to the material properties of the potting compound 18, it penetrates at least into the radially outer region of the winding head 10, but only to the extent that the potting compound does not escape from the radially inner region of the winding head 10.

[0057] Figure 2 A stator 2 is shown in a side view, which is positioned in a housing 12 and has its winding system 3, which forms a winding head 10 at the end face of the stator 2. The gap 14 is filled with a potting compound 18. The stator 2 is positioned in particular vertically or obliquely. First, the end face of the stator is provided with the potting compound 18, and then the other end face is filled with the potting compound.

[0058] The filling of the stator 2 in the vertical or inclined state requires sequential processing of the corresponding end faces. Between the completion of filling on one end face and the start of filling on the other end face, about 15 minutes to 30 minutes must be allowed at room temperature depending on the size of the gap 14 (depending on the type of motor in particular).

[0059] Due to the material properties of the potting compound 18, it penetrates the winding head 10, i.e. the flange 24 and the winding neck 11, and only to a certain extent the inner hole 5 remains free of the potting compound 18. This simplifies the production and potting of the winding system 3 in a simple manner. In addition, the thermal connection of the winding head 10 to the housing 12 is improved.

[0060] Figure 3 A section of a stator 2 located in a housing 12 is shown in a perspective partial view. The stator 2 is equipped with a winding system 3. Axially outside the lamination stack 4 of the stator 2, the winding necks 11 can be seen, the electrical conductors of which extend axially. In the flange 24 of the winding head 10, these conductors are then bent to be guided into the other slots 6. The packing density of the conductors of the winding system 3 increases radially inwardly in the flange 24, so that the capillaries between the conductors of the potting compound 18 are increasingly narrowed, and the viscosity is additionally reduced, so that the penetration inwardly in the radial direction through the winding head 10 is more difficult.

[0061] Due to the good thermal conductivity of the individual conductors adjacent to one another, in particular copper conductors, even if the individual conductors are not directly surrounded by the potting compound 18 , there is nevertheless a relatively acceptable thermal conductivity to the outside within the flange 24 .

[0062] Due to the mutual contact of the electrical conductors, thermal conductivity also occurs here radially outwards into the region of the winding head 10 , which is provided with a potting compound 18 having good thermal conductivity.

[0063] The potting compound 18 uses a molding material (reaction resin, such as epoxy resin, polyurethane or polyester) filled with thermally conductive particles. Depending on the thermal conductivity required for the potting compound, these filler particles, including quartz powder, fused silica, boron nitride or aluminum oxide, are dispersed as microparticles in the matrix (reaction resin) with an optimized particle size distribution so that a fluid molding compound with the lowest possible viscosity is still present. The filling degree of the filler in the matrix is ​​between 20 volume percent and 70 volume percent, depending on the required fluidity at the processing temperature.

[0064] According to the invention, in addition to the filling with the above-mentioned thermally conductive particles, the potting mixture 18 is also provided with a rheologically optimized additive. This additive causes the flowability of the potting mixture 18 to assume thixotropic and structurally viscous properties and thus its viscosity decreases significantly at an increased shear rate and returns to a significantly higher viscosity at a subsequent low shear rate. The metering unit provided for this purpose can be used to fill the area step by step, in particular the gap 14 between the winding head 10 and the inner edge 17 of the housing 12, the stator 2 preferably being placed vertically up to the axial extension 13 of the winding head 10. Due to the shear forces that occur during dispensing, the flowing potting mixture 18 reduces its viscosity, distributes itself evenly in the gap 14 and wraps the individual wires of the winding head 10 in a form-fitting manner.

[0065] As the flow process between the winding necks 11 and inside the winding necks and in the flanges 24 gradually slows down, the viscosity continues to increase due to the reduction in shear forces, which causes the flow front of the potting compound 18 to solidify independently between the winding necks 11 .

[0066] The intermediate region or gap 14 between the winding head 10 and the housing 12 can thus be filled / potted without an additional housing, ie without using an inner mandrel for the inner bore of the stator 2 .

[0067] A typical example of a thixotropic additive is fumed silica (silica gel), which is dispersed in the potting mixture 18 (0.1 weight percent to 1 weight percent) to achieve these desired properties.

[0068] Another material property of the potting compound 18 is that it is a two-component reaction resin which is mixed in situ in the metering unit (resin component and hardener component). This ensures that the potting compound 18 is set within a relatively short time (several hours to only a few minutes) without any additional temperature input. Due to the formation of the chemical network, the base viscosity of the potting compound 18 increases, so that the production process is not interrupted and work can continue on the stator 2 or electric motor 1.

[0069] The temperature input into the process would reduce the viscosity and is therefore not possible, since otherwise the potting compound 18 would pass without a housing or inner mandrel, in particular between the winding necks 11 and / or the flanges 24 and flow into the inner radius, ie the inner bore, of the stator 2 .

[0070] In principle, the housing 12 can be made of aluminum or other heat-conducting materials. In addition, in order to further improve the cooling, it can be equipped with ribs 21 at least in sections.

[0071] Figure 4The housing 12 is shown with an exemplary arrangement for liquid cooling 22 . In this case, spiral cooling pipes are arranged in the housing 12 . This improves the cooling of the electric motor 1 , in particular the stator 2 and there in particular the winding heads 10 .

[0072] Figure 5 A further design possibility of the housing 12 is shown, which now provides the possibility of a closed internal air cooling cycle. In this case, air is conveyed into the interior of the machine 1 via a fan arranged in the housing 12 , in particular via the winding head 10 .

[0073] Due to its simple design and efficiency, such an electric rotating machine 1 is used in industry, food production and traffic engineering as a fan, compressor, supercharger, pump or the like.

Claims

1. A method for manufacturing a stator (2) of an electric rotating machine (1), the method comprising the following steps: - arranging a winding system (3) in a magnetic conductor, in particular an axially stacked lamination stack (4), in a slot (6) facing the inner bore (5) so that a corresponding winding head (10) is produced on the end face of the magnetic conductor, - connecting the magnetic conductor, in particular a laminated core (4), to a housing (12) which is in particular heat-conducting in a rotationally fixed manner, wherein the housing (12) extends axially on both sides of the laminated core (4) of the stator (2) at least as far as the axial outer edge of the respective winding head (10), so that in the region of the winding head (10) a respective circumferential gap (14) is produced between the radial outer side (16) of the winding head (10) and the inner edge (17) of the housing (12), - filling the circumferential gap (14) between the radial outer side (16) of the winding head (10) and the inner edge (17) of the housing (12) with a potting compound (18) having at least one rheology-optimizing additive, so that the winding head (10) is thermally connected to the housing (12), - wherein the potting compound (18) penetrates into the radially outer region of the winding head (10), but only in such a way that the potting compound (18) does not overflow at the radially inner edge of the winding head (10).

2. The method for manufacturing a stator (2) of an electric rotating machine (1) according to claim 1, characterized in that The magnetic conductor is heat shrunk into the housing (12).

3. The method for manufacturing a stator (2) of an electric rotating machine (1) according to claim 1 or 2, characterized in that: The winding system (3) has a preformed coil or a wire.

4. A method for manufacturing a stator (2) for an electric rotating machine (1) according to any one of the preceding claims, characterized in that In particular, fumed silica is used as additive.

5. A method for manufacturing a stator (2) for an electric rotating machine (1) according to any one of the preceding claims, characterized in that In the potting mixture (18), a two-component reaction resin and / or a filler are additionally provided to increase the overall viscosity and thermal conductivity.

6. A method for manufacturing a stator (2) for an electric rotating machine (1) according to any one of the preceding claims, characterized in that The stator (2) is filled with a vertical axis (7) or with an inclination of the axis (7) of a maximum of 45 degrees.

7. An electric rotating machine (1) having a stator (2) with a magnetic conductor, in particular an axially stacked lamination stack (4), wherein: A winding system (3) is arranged in a groove (6) facing an inner bore (5) of the stator (2), the winding system forming a winding head (10) on each end face of the magnetic conductor, wherein a rotationally fixed connection is provided between the magnetic conductor and an in particular heat-conducting housing (12). wherein the housing (12) extends axially on both sides of the magnetic conductor of the stator (2) at least as far as the axial outer edge of the respective winding head (10), wherein a circumferential gap (14) between the radial outer side (16) of the winding head (10) and the inner edge (17) of the housing (12) is filled in the region of the winding head (10) with a potting compound (18) using at least one rheologically optimized additive, so that the winding head (10) is thermally connected to the housing (12), And the electric rotating machine has a rotor (19), wherein the stator (2) and the rotor (19) are spaced apart from each other by an air gap (15).

8. The electric rotating machine (1) according to claim 7, characterized in that When viewed in the circumferential direction and / or in the axial direction, the housing (12) has at least partially protruding ribs (21).

9. The electric rotating machine (1) according to claim 7 or 8, characterized in that: The housing (12) has means for providing water jacket cooling (22) or a closed internal air cooling circuit (23).

10. The electric rotating machine (1) according to any one of claims 7 to 9, characterized in that The housing (12) is made of aluminum or other heat-conducting materials.

11. Use of an electric rotating machine (1) according to any one of claims 1 to 6 and according to claims 7 to 10 as a drive, in particular for use in fans, compressors, superchargers and pumps.

12. Use of an electric rotating machine (1) according to claim 11, for example in an industrial environment, in the food industry, in traffic engineering or in air conditioning systems.

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