Keeping cooling channels clear

Abstract

Method for providing at least one cooling channel in a stator for an electric machine, in particular an electric motor or generator, comprising the steps of: - Inserting at least one first conductor element into a slot of the stator at a first position, wherein at least one first width of an active area of ​​the first conductor element is selected such that a first gap is created between the active area of ​​the first conductor element and an inside of the slot; - Introducing, in particular inserting, at least one negative tool into the first gap; - Applying a curable fluid at least in the area of ​​the groove, in particular impregnating and / or dripping and / or potting the stator with the curable fluid; - Removal of the at least one negative tool after the curable fluid has become dimensionally stable, preferably at least substantially cured, to expose at least one cooling channel.

Description

[0001] The invention relates to a method for providing at least one cooling channel in a stator, in particular for electric motors, comprising at least one cooling channel for cooling the electrical conductors which run in the stator core.

[0002] Active cooling of electric motors is now standard practice in automotive engineering and other high-speed or high-frequency applications for electric motors. Such motors inherently generate a certain amount of thermal energy, making cooling necessary for efficient operation. It is generally advantageous to apply the cooling directly to the conductor itself, as this significantly increases cooling efficiency and allows for a more compact design.

[0003] Typically, the conductors are inserted into a pre-machined groove in a stator core, preferably via cooling channels within or near the groove. While it is generally known in the art to provide cooling channels along the conductors in a stator, arranging these channels in the immediate vicinity of the conductors is complex.

[0004] Prior art solutions exist that loosely insert the conductors into the groove, creating gaps within the groove that allow for the circulation of air, oil, or similar substances, thus providing some cooling to the conductors. However, these solutions have the disadvantage that the conductors are poorly mechanically secured and therefore slip or rattle, which is considered detrimental. Furthermore, thermal coupling is poor or unpredictable because the channel size is difficult or impossible to adjust.

[0005] Another approach, known from the prior art, involves using gaps between the conductors or conductor elements by placing placeholders between them. Because the conductors are separated by these placeholders, spaces are created through which the cooling fluid can circulate. However, this solution is also considered disadvantageous, as the placeholders themselves take up space, leading either to a reduction in the cross-section of the cooling channel and thus to lower cooling capacity, or to a reduction in the cross-section of the conductor elements and thus to impaired conductivity.

[0006] Furthermore, in the aforementioned methods, the electrical insulation of the conductors is complex or costly.

[0007] There is therefore a need to provide a simplified procedure for providing cooling channels near the conductors, which at least partially overcomes the disadvantages described above.

[0008] The solution to the above problem is provided by a method according to claim 1, as well as by a negative tool according to claim 12 and a stator core according to claim 13.

[0009] In particular, this problem is solved by a method for providing at least one cooling channel in a stator for an electric machine, especially an electric motor or generator, (or a corresponding manufacturing method for manufacturing a stator), comprising the steps: - Inserting at least one first conductor element into a slot of the stator at a first position, wherein at least one first width of an active area of ​​the first conductor element is chosen such that a first gap is created between the active area of ​​the first conductor element and an inner surface of the slot; - Insertion (before, during and / or, preferably, after the insertion of the at least one first conductor element into the groove), in particular insertion, of at least one negative tool into the first gap; - Applying a curable fluid (or resin) at least in the area of ​​the groove, in particular impregnating and / or dripping and / or potting and / or coating the stator with the curable fluid (or resin); - Removal of the negative tool(s) after the curable fluid has become dimensionally stable, preferably at least substantially cured, to expose at least one cooling channel.

[0010] A key idea of ​​the invention is to provide a cooling channel by “blocking” a certain space within the gap forming between the inside of the groove and the conductor element using the negative tool, and then introducing a curable fluid into the stator.

[0011] The curing fluid then fills the remaining gaps (clefts), simultaneously insulating the conductors (secondary insulation) and encasing the negative mold. Once the curing fluid has stabilized sufficiently to be dimensionally stable, the negative mold can be removed, leaving a channel in the areas previously blocked by the mold. This channel then serves as a cooling channel for circulating a cooling fluid. For example, the mold can be removed after a resin has gelled (especially at the end of the gelation phase) but before (complete) curing (especially before, but possibly also after, the start of the resin's curing phase).

[0012] The invention offers the advantage that secondary insulation and the formation of the cooling channel can be carried out in a single step, enabling more efficient and therefore more cost-effective manufacturing. Furthermore, the introduction of a curable fluid creates a metallurgical bond with the conductor element, allowing for better heat transfer than air. In addition, the shape and course of the cooling channel can be easily and cost-effectively adjusted by selecting the appropriate width of an active area of ​​the conductor element.

[0013] The active area of ​​the conductor is understood to be, in particular, the area that is inserted into the groove or at least substantially contained within the groove. Specifically, the active area is that part of the conductor element which is arranged at least substantially parallel to the longitudinal direction of the groove.

[0014] According to the invention, the width of the active area is understood to be the extent of the conductor element in a direction orthogonal to the longitudinal direction of the groove. Preferably, the extent is along the direction connecting a left-bounding inner surface with a right-bounding inner surface of the groove, orthogonal to the direction connecting the back surface of the groove with the opening of the groove. Preferably, the width of the active area (of at least one conductor element) is less than 90% of the width of the groove (at the corresponding location), more preferably less than 80%, and even more preferably less than 75%.

[0015] In a preferred embodiment, the method comprises the steps: - Inserting at least one second conductor element into the slot of the stator at a second position, wherein a second width of the active area of ​​the second conductor element is chosen such that a second gap is created between the active area of ​​the second conductor element and an inside of the slot, wherein the first and the second gap form a continuous gap; - Inserting, in particular placing, the negative tool and / or a further negative tool into the second space, wherein the corresponding negative tool is shaped in such a way that it fills a continuous area with a respective section in both the first and the second space, preferably to form a continuous channel in the first and second space.

[0016] This allows for the provision of cooling channels with a cross-section larger than a single (first or second) gap. According to this embodiment, adjacent gaps are combined into a single, continuous gap, which can then accommodate a correspondingly larger cooling channel.

[0017] By combining multiple cooling channels into larger ones, the cross-sectional area of ​​the cooling channels can be easily adjusted. This is particularly advantageous because the hydrostatic pressure within the cooling channels depends significantly on their cross-sectional area. A large number of small cooling channels therefore exhibits a higher pressure drop than a smaller number of large channels, where "small" and "large" refer to the cross-sectional area. By appropriately selecting the number and / or cross-sectional area of ​​cooling channels, the pressure drop within the stator can thus be tailored to specific requirements.

[0018] Either a single negative tool can be inserted into the formed continuous space, or two disjoint negative tools can be used, in which case the two disjoint negative tools should at least be in contact with each other to ensure that a common cooling channel is formed.

[0019] Alternatively, two separate cooling channels can be formed in a common, interconnected space by ensuring that the two negative tools do not come into contact with each other, or are not in contact with each other.

[0020] In a further preferred embodiment, the method alternatively or additionally comprises the following steps: - Inserting at least one third conductor element into a slot of a stator at a third position, wherein at least one third width of an active area of ​​a third conductor element is selected such that a third gap is created between the active area of ​​the third conductor element and an inside of the slot, wherein the third gap is located on a side of the third conductor element opposite the first gap; - Introducing, in particular inserting, the negative tool and / or another negative tool into the third space.

[0021] The third conductor element should be distinguished from the second conductor element primarily in terms of concept. In this sense, a second and a third conductor element may be provided; however, this is not mandatory.

[0022] Within a groove, for example, all the spaces can be located on one side. Alternatively, the spaces can be arranged alternately on opposite sides. Intermediate solutions are also possible (e.g., two spaces arranged on the same side forming a pair, with several such pairs arranged alternately).

[0023] If the width of the active area of ​​the conductor element is less than the width of the groove, the conductor element can be positioned closer to one of the inner sides of the groove. Depending on whether the conductor element is closer to the left or right inner side of the groove, the gap forms on the right or left side of the groove, respectively. By staggering the arrangement, offset gaps and thus cooling channels can be created.

[0024] This offers the advantage that the spaces between the elements can be easily separated, simplifying the provision of numerous cooling channels. Furthermore, this staggered arrangement of the conductor elements results in a larger surface area exposed to the negative mold or cooling channel, as a certain overhang of the active area, in addition to one side, also borders the negative mold or cooling channel. This allows for better adjustment and, preferably, an increase in cooling performance.

[0025] Each groove can contain at least or exactly two, or at least or exactly three, or at least or exactly four, or at least six conductor elements. Each groove can contain at most 20, or at most 12, or at most eight, or possibly at most six, conductor elements.

[0026] According to a further preferred embodiment, the first and / or second and / or third width is selected such that a clamping effect is created between an inside of the groove and the first and / or second and / or third conductor element.

[0027] A clamping action secures the conductor element in the groove, resulting in improved handling during the introduction of the curing fluid. This is particularly advantageous in applications where the conductor elements are formed by so-called hairpins (or simply pins). In these applications, the conductor elements preferably have a (at least approximately) U-shaped (or horseshoe-shaped) form, with each leg of the U-shape being inserted into one of two adjacent grooves. The conductor elements are easily secured by clamping between the grooves. Optionally, either the inner or outer side of the leg can rest against the groove, or the conductor elements can be slid inwards or outwards.

[0028] According to another embodiment, the curable fluid is a potting compound and / or an impregnating resin, preferably based on epoxy resin, unsaturated polyester and / or polyesterimide and / or silicone resin.

[0029] The use of impregnating resins is advantageous because they possess both the mechanical and electrical properties desirable for encasing cooling channels and insulating conductor elements. On the one hand, these resins effectively fill the gaps left behind; on the other hand, after curing, they form a sufficiently stable secondary insulation. Furthermore, properties such as thermal conductivity are also beneficial, particularly due to the strong bond with the surrounding elements.

[0030] According to another embodiment, the curable fluid is electrically insulating, at least in its cured state.

[0031] The use of electrically insulating resins thus allows for simple but effective insulation of the conductor elements, as well as electrical insulation of the cooling channels.

[0032] In this embodiment, the negative tool can be used in such a way that it is in contact with the active area of ​​the conductor element (preferably allowing penetration of curable fluid between the negative tool and the conductor element).

[0033] The negative tool is preferably used in such a way that it is in contact with an inner side (inner surface) of the groove.

[0034] According to another embodiment, a conductor element is a pin, preferably a hairpin.

[0035] The use of hairpins is advantageous because the conductor element's essentially U-shaped form allows for easy insertion into the groove, particularly overlapping insertion, where one leg of the U-shape is inserted into one groove and the other leg into an adjacent groove. This makes it particularly easy to achieve a clamping effect.

[0036] The negative mold preferably has a low roughness and / or is smoothed, in particular polished, and / or is coated and / or is moistened with a sliding material, such as grease. This simplifies removal after impregnation and stabilization, and optionally curing, of the curable material. Smoothing can be achieved by polishing, burnishing, grinding, lapping, honing, pickling, sandblasting, bristle blasting, etching, vapor deposition, and / or corrosion. The mean roughness Ra (according to DIN EN ISO 4287) is preferably at most 1.0 µm; more preferably at most 0.4 µm; and / or at least 0.001 µm, optionally at least 0.01 µm, or at least 0.1 µm.

[0037] Before and / or during the removal of the negative mold, frictional force reduction (or a frictional force reduction measure) can be implemented, for example, through thermal treatment (heating and / or cooling) and / or vibration. Frictional force reduction is preferably only a temporary (especially reversible) measure. This simplifies removal after impregnation and stabilization, and possibly curing, of the curable material.

[0038] A method according to one of the preceding claims, wherein the stator is fixed, in particular clamped, during the removal of the negative tool (in order to be able to apply a force that overcomes the frictional force). This also simplifies removal after impregnation and stabilization, and optionally curing, of the curable material.

[0039] The object of the invention is also solved by a negative tool, wherein the negative tool has a plurality of prongs, wherein the prongs are each inserted into at least one space, wherein the position of the prongs is chosen so that it corresponds to the position of the conductor element in such a way that a desired space pattern results.

[0040] Instead of individually positioning many negative tools in the respective gaps, it is advantageous to use a "comb-like" arrangement of a single, continuous negative tool. This allows the appropriate gap pattern to be determined in advance by the arrangement of the prongs, significantly increasing the manufacturing speed.

[0041] The problem according to the invention is also solved by a stator comprising at least one cooling channel, manufactured according to the method described above.

[0042] The problem according to the invention is also solved by a method for manufacturing a stator for an electric machine, in particular an electric motor or generator, comprising the method for providing at least one cooling channel.

[0043] The invention is described below with regard to further details, features, and advantages, which are explained in more detail with reference to the figures. The described features and combinations of features, as shown below in the figures and described with reference to the drawing, are applicable not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention.

[0044] This shows: Fig. 1: A side view representation of the stator groove; Fig. 2: a cross-sectional view of the stator slot with three inserted conductor elements; Fig. 3: a cross-sectional view of the stator slot with three inserted conductor elements; Fig. 4: a cross-sectional view of the stator slot with five inserted conductor elements; Fig. 5: a cross-sectional view of the stator slot with five inserted conductor elements; Fig. 6: a cross-sectional view of the stator slot with five inserted conductor elements; Fig. 7: a cross-sectional view of the stator slot with five inserted conductor elements; Fig. 8: a cross-sectional view of the stator slot with five inserted conductor elements; Fig. 9: a cross-sectional view of the stator slot with five inserted conductor elements; Fig. 10: a representation of a hairpin as a conductor element; and Fig. 11: a representation of a negative tool;

[0045] Fig. Figure 1 shows a side view of a stator core 1, which displays a conductor element 11 having a hairpin shape. In particular, it can be seen that the active section 101 of the conductor element runs within the stator core itself, whereas a roof section 102 is not in contact with the inside of the stator. The respective legs of the conductor element are inserted into two slots 2, which extend along the stator at least substantially parallel to each other.

[0046] Also shown is a negative tool 31, which was inserted into the groove together with the conductor element 11, with the conductor element 11 being positioned on the right inside of the groove 2 and the negative tool 31 on the left inside of the groove 2.

[0047] Fig. Figure 2 shows a cross-section through a portion of the stator core, essentially following the perspective along section xx in Fig. 1 corresponds to. As shown here, the first negative tool 31 is inserted into the first gap 21 that has formed between the (right) inner side of the groove 2 and the first conductor element 11. The width of the first conductor element 11 is chosen such that a sufficiently large first gap 21 is formed.

[0048] In the illustrated embodiment, a second gap 22 adjoins the first gap 21, which is in turn formed between the inside of the groove 2 and the second conductor element 12. In the illustrated configuration, the two gaps are connected, resulting in a single, larger gap.

[0049] Furthermore, a third conductor element 13 is also positioned within the groove 2, the positioning being such that a third gap 23 is formed between the (left) inner side of the groove 2 and the third conductor element 13. The third gap 23 is opposite the first and second gaps 21, 22.

[0050] Fig. 3 essentially shows the same configuration as Fig. 2, wherein the first negative tool 31 is now dimensioned such that it fills a contiguous area with a respective section in both the first 21 and the second 22 space. It is equally possible (indicated here by a dashed line) that a first and a second negative tool 31, 32 are each inserted accordingly into the first and second spaces 21, 22.

[0051] In Fig. Figure 4 shows a staggered arrangement of conductor elements 11, 12, 13, 14, 15 according to a further embodiment of the invention. The width of each conductor element 11, 12, 13, 14, 15 is selected such that a corresponding space 21, 22, 23, 24, 25 is formed, in which a negative tool 31, 32, 33, 34, 35 (or a part of a single negative tool, etc.) is inserted to keep a corresponding cavity free, which becomes a cooling channel 5 after curing.

[0052] Such a staggered arrangement of the conductor elements 11, 12, 13, 14, 15, which alternately form opposing gaps 21, 22, 23, 24, 25, results in a multitude of individual cooling channels. In particular, the alternating opposing gaps 21, 22, 23, 24, 25 allow for particularly efficient cooling, since each negative tool 31, 32, 33, 34, 35 (and thus subsequently each cooling channel 5) borders both laterally on an associated conductor element 11, 12, 13, 14, 15 and on a projection of a conductor element 11, 12, 13, 14, 15 that lies above or below the associated conductor element 11, 12, 13, 14, 15. This increases the total area that can be cooled by the subsequent cooling channel 5, resulting in more efficient cooling.

[0053] In principle, the pressure loss can be specifically influenced, increased or decreased, by increasing or decreasing the number of separate channels while keeping the number of gaps and conductor elements constant. In particular, a low pressure loss can be achieved by selecting large, continuous channels.

[0054] Fig. Figure 5 shows an arrangement with five conductor elements 11, 12, 13, 14, 15, wherein the first, second, and third conductor elements 11, 12, 13 are each arranged or positioned on the left inner side of the groove 2, and the fourth and fifth conductor elements 14, 15 are arranged on the right side of the groove 2. In the illustrated embodiment, three separate negative tools, namely the first 31, the second 32, and the third 33, are each inserted into the first 21, the second 22, and the third 23 spaces, respectively, in such a way that they touch each other, preventing any curable fluid from passing between them. In this way, it is possible to form a continuous cooling channel 5 across a certain number of adjacent and therefore connected spaces 21, 22, 23, even with several negative tools.

[0055] Opposite each other are the fourth conductor element 14 and the fifth conductor element 15, so that a further connected space is formed from the fourth space 24 and the fifth space 25, into which a fourth negative tool 34 and a fifth negative tool 35 are inserted.

[0056] By appropriately selecting the positions of the conductor elements 11, 12, 13, 14, 15, various channel patterns with a multitude of differently dimensioned channels can be achieved.

[0057] Fig. Figure 6 shows another arrangement with five conductor elements 11, 12, 13, 14, 15, all now positioned on the left inner side of groove 2, creating a large continuous gap across the five spaces 21, 22, 23, 24, 25. Three negative tools are shown inserted into these spaces. The first negative tool 31 is inserted into the first space 21, the second negative tool 32 into the second space 22, and a third (combined) negative tool 31, 34, 35 is inserted into the third, fourth, and fifth spaces 23, 24, and 25. It would also be possible to insert an individual negative tool into each of the spaces or to choose other combinations. In the illustrated embodiment, there is again no gap between the negative tools 31, 32, 33, 34, 35, resulting in a continuous cooling channel 5 (not shown).In situations where a continuous channel is to be created over a large number of adjacent spaces 21, 22, 23, 24, 25, it may be advantageous to use only one negative tool instead of many individual ones.

[0058] Fig. Figures 7-9 show a corresponding arrangement according to the Fig. 4-6 after the introduction and (at least partial) curing of the curable fluid 4. As can be seen here, the curable fluid 4 is directed into the remaining spaces within the stator core, where it then cures. In the illustrated configurations, the negative tools 31, 32, 33, 34, 35 have already been removed, so that the remaining impression has led to the formation of a cooling channel 5 of the corresponding shape.

[0059] It should be noted that the arrangement of the negative tools 31, 32, 33, 34, 35 in Fig. 7 to five individual cooling channels 5 has led, whereas in Fig. 8 two interconnected cooling channels were formed and in Fig. 9 a single continuous cooling channel was formed.

[0060] It should be generally noted that the constellations shown, or numbers and arrangements of the spaces, ladder elements and negative tools, are only examples and any other combinations and arrangements are possible.

[0061] Fig. Figure 10 shows a side view of a pin 7, which has an active area 101 and a roof area 102. The active area 101 need not be materially distinguishable from the roof area 102, but is only delimited by its positioning. In particular, the pin 7 can also be a single piece.

[0062] Fig.Figure 11 shows a continuous negative tool, in which four forks 31, 32, 33, 34 are each designed to be inserted into a corresponding space. These are held together by a bridge element 8, which speeds up and simplifies the insertion process.

[0063] It should be noted here that all parts described above, considered individually and in any combination, especially the details shown in the drawings, are claimed as essential to the invention. Modifications to this are familiar to those skilled in the art.

[0064] Furthermore, it is noted that the broadest possible scope of protection is sought. Therefore, the disclosure contained in the claims can also be specified by features that are described by further features (even if these further features are not necessarily included). It is explicitly pointed out that parentheses and the term "in particular" are intended to emphasize the optionality of features in the respective context (which does not imply that a feature is mandatory in the corresponding context without such indication). The term "element" can denote a coherent structure, which in turn may be connected to at least one other structure (to form a potentially monolithic and / or internally immobile overall structure) (or may be distinct from all other structures). Reference symbol list 1 Stator core 2 Nut 11, 12, 13, 14, 15 ladder element 21, 22, 23, 24, 25 space 31, 32, 33, 34, 35 Negative tool(s) 101 Active area 102 Roof area 4 Curable Fluid 5 Cooling channel 7-pin 8 Bridge area

Claims

[1] Method for providing at least one cooling channel in a stator for an electric machine, in particular an electric motor or generator, comprising the steps: - Inserting at least one first conductor element into a slot of the stator at a first position, wherein at least one first width of an active area of ​​the first conductor element is selected such that a first gap is created between the active area of ​​the first conductor element and an inside of the slot; - Introducing, in particular inserting, at least one negative tool into the first gap; - Applying a curable fluid at least in the area of ​​the groove, in particular impregnating and / or dripping and / or potting the stator with the curable fluid; - Removal of the at least one negative tool after the curable fluid has become dimensionally stable, preferably at least substantially cured, to expose at least one cooling channel. [2] Method according to claim 1, further comprising the steps: - Inserting at least one second conductor element into the slot of the stator at a second position, wherein a second width of the active area of ​​the second conductor element is chosen such that a second gap is created between the active area of ​​the second conductor element and an inside of the slot, wherein the first and the second gap form a continuous gap; - Inserting the negative tool and / or another negative tool into the second space, wherein the corresponding negative tool is shaped to fill a continuous area with a respective section in both the first and second spaces, preferably to form a continuous channel in the first and second spaces. [3] A method according to any of the preceding claims, comprising the steps of: - Inserting at least one third conductor element into a slot of a stator at a third position, wherein at least one third width of an active area of ​​a third conductor element is selected such that a third gap is created between the active area of ​​the third conductor element and an inside of the slot, wherein the third gap is located on a side of the third conductor element opposite the first gap; - Inserting the negative tool and / or another negative tool into the third space. [4] Method according to one of the preceding claims, wherein the first and / or second and / or third width is selected such that a clamping effect is created between an inside of the groove and the first and / or second and / or third conductor element. [5] Method according to any of the preceding claims, wherein the curable fluid is a potting compound and / or an impregnating resin, preferably based on epoxy resin, unsaturated polyester and / or polyesterimide and / or silicone resin. [6] Method according to any of the preceding claims, wherein the curable fluid is electrically insulating, at least in the cured state. [7] Method according to one of the preceding claims, wherein at least one conductor element is a pin, preferably a hair-pin. [8] Method according to one of the preceding claims, wherein the negative tool has a low roughness and / or is polished and / or coated and / or is wetted with a sliding material, such as grease. [9] Method according to one of the preceding claims, wherein a reduction in frictional force is carried out before and / or during the removal of the negative tool, for example by thermal treatment and / or by vibration. [10] Method according to one of the preceding claims, wherein the stator is fixed, in particular clamped, during the removal of the negative tool. [11] Negative tool for use in a method according to one of claims 1 to 10, wherein the negative tool has a plurality of prongs, the prongs being inserted into at least one space, the position of the prongs being selected to correspond to the position of the conductor element so that a desired space pattern is obtained. [12] Stator for an electric machine, in particular an electric motor or generator, comprising at least one cooling channel, manufactured according to the method of claims 1 to 11.

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