Coil tooth module and manufacturing method thereof

Abstract

To provide a toothed coil module capable of enhancing a filling factor of an installation space in accordance with an application by changing a cross section each time a helical coil is wound.SOLUTION: The invention relates to a toothed coil module 100 and a method for producing the same. A pre-prepared coil 102 is filled with a metal powder and the powder is then pressed into a tooth, thus producing a toothed coil module, in which the tooth bears directly on the coil.SELECTED DRAWING: Figure 6A

Description

[Technical Field]

[0001] The present application relates to a method for manufacturing a coil tine module and a coil tine module manufactured using the method. [Background technology]

[0002] Wound coils are used in electric machines. In many applications, the coils do not optimally fill the available installation space, resulting in low power or torque density for the weight or installation space. The use of cast, die-wound, or printed coils with varying cross-sections of the inner longitudinal contour defined by the coil improves the fill factor and alleviates the above-mentioned drawbacks.

[0003] To improve the efficiency of the electric machine, coils are placed or wound on the teeth. The teeth can be made of or consist of sheet layers or laminate stacks or soft magnetic composites (SMC). To attach the coils to the teeth to allow for attachment, they must be reduced in size. Contact between the coil and the teeth is not ideal. Summary of the Invention

[0004] The present application presents a coil tine module and a method for manufacturing the same that reduces the above-mentioned drawbacks.

[0005] The object is achieved by a method according to claim 1 and by a coil tooth module according to claim 10. Further embodiments can be derived from the dependent claims and the exemplary embodiments described.

[0006] According to the method of the present invention, a pre-formed coil is inserted into a press mold. The press mold can support the coil, for example, at its bottom surface. The pre-formed coil defines, using windings, an inner contour around which the coil extends. The inner contour extends longitudinally from the lower opening of the coil to the upper opening of the coil. The pre-formed coil is preferably a helical coil, having an exemplary shape as shown in EP 2 387 135 A2. The pre-formed coil is preferably formed into a helical shape using a printing method, a casting method, or a die-winding method.

[0007] After the coil is placed in the press die, the inner contour of the coil is filled with metal powder, preferably SMC powder, and in this process the inner contour is preferably completely filled.

[0008] After the filling process is complete, the metal powder is compressed into the tooth shape using a press die, for example, with a plunger. The coil-tooth module thus produced has a very large contact surface between the coil and the tooth, since the powder is packed into the inner contour, leaving essentially no voids between the coil and the powder. Once the powder is compressed to form the tooth, the tooth directly contacts the coil. The tooth itself is dense and at the same time, is tightly thermally and magnetically coupled to the inner shape of the coil.

[0009] The pressing process forces the powder particles into cavities and compresses them under high pressure, preferably filling all voids within the interior space of the coil and compacting the bulk powder. The hundreds of megapascals of pressure present during pressing create a form fit between the particles such that they are pressed together to form a solid.

[0010] The better contact between the teeth and the coil of the coil tooth module described above compared to conventional coil tooth modules improves the thermal contact between the coil and the teeth and improves the magnetic properties of the coil tooth module, thereby improving the heat dissipation of the coil and increasing the magnetic permeability of the coil tooth module. In contrast to conventionally manufactured coil tooth modules, it is not necessary (and potentially impossible) to seal the cavity between the coil and the teeth with a potting compound.

[0011] In one embodiment of the method, the metal powder may further be excited to flow during filling or prior to pressing, for example by vibrating or shaking the press mold, so that the bulk powder is better distributed within the interior space of the coil, thereby filling gaps between the individual coil turns.

[0012] The press die can be designed as a component of a press tool. In a first embodiment, the bottom of the press die supports at least the surface of the coil including the lower opening (hereinafter referred to as the lower surface). Using a plunger of the press tool, the coil is compressed or pressed from the surface of the coil including the upper opening (the upper surface), i.e., the surface of the coil opposite the lower surface, after being filled with metal powder.

[0013] In addition to the bottom, the press mold can also have one or more side walls that define an internal space into which the outer contour of the coil, defined by the outer surface of the coil tooth module to be produced, preferably abuts the internal space. The side walls of the press tool prevent the coil from deforming or being pushed outward while compressing or pressing the bulk powder disposed in the coil's internal space. In this way, powder particles cannot escape through the gap between two adjacent turns of the coil, improving the filling of the cavities and the gap between the two adjacent turns. Since bulk powder is preferably not present between the side walls of the press mold and the outer side of the coil, the outer side of the coil is not surrounded by the pressed metal powder after pressing. This means that the outer side is not surrounded by additional metal powder that creates the teeth.

[0014] In one embodiment of the method, the coil is compressed along its length inside a press die before filling the coil with metal powder to minimize the gap between two adjacent turns. In this way, the volume of the gap that may occur between two adjacent turns is minimized. The compression can be performed, for example, using additional components of the press tool.

[0015] In helical coil embodiments, the inside of each turn can extend to the inner contour of the coil and thus be in direct contact with the teeth. As a result, the coil is a single-layer coil with no turns arranged one above the other when viewed from the inside out. Furthermore, the cross section can vary from turn to turn in a helical coil to improve the fill factor of the installation space, depending on the application.

[0016] In another embodiment, the coil tooth module is heat-treated after pressing the metal powder. In this way, residual stresses within the compacted teeth resulting from the pressing operation are reduced or eliminated. In this process, the coil tooth module can be treated at temperatures between 500°C and 800°C for 15 to 30 minutes under protective gas, air, or a reducing atmosphere.

[0017] In another embodiment, the metal powder on which the coil is then placed is introduced into the press die before the coil is inserted into the press die. After filling the interior space of the coil, the already introduced powder is compacted following pressing to form the tooth root, which, due to the particles used, forms a form fit with the teeth placed in the interior space of the coil, so that the teeth and tooth root are firmly and permanently joined to each other. Instead of producing the tooth root during pressing of the metal powder, it can be inserted into the press die only after the tooth root has been previously produced. Powder particles are then added to the interior space of the coil and then compacted. In another alternative, the powder introduced into the press die for the tooth root is first pressed and given the shape of the tooth root. Only afterwards is the coil introduced and filled.

[0018] In another embodiment, the metal powder completely fills the interior space of the coil. Optionally, the metal powder completely covers the top surface of the coil, so that the tooth tips are formed during pressing of the coil tooth module. In another embodiment, the outer contour of the coil or the outer side surface of the coil remains uncovered by the metal powder that forms the teeth.

[0019] In embodiments that include a tooth root or tooth tip, the press die can be shaped to define the tooth root or tooth tip shape. The tooth root or tooth tip shape can be selected in the process so that an extension or recess is present that allows for a form fit with the rotor or stator of the electric machine. In these examples, the coil tooth module can be inserted into and secured to the stator or rotor.

[0020] In another embodiment, the prefabricated coil is shaped such that, in the longitudinal direction, the teeth engage the backside of at least one turn. In this way, a form-fit connection can be established between the coil and the teeth. For example, the thickness and width of one turn of the coil can be varied so that the outer contour of the coil extends evenly across all turns, and the width of one turn in the transverse direction is reduced to form an undercut at two abutting turns.

[0021] The above-described embodiments can be combined with each other in any way, unless the embodiments are described as alternatives to each other.

[0022] The methods described herein can be used to manufacture coil-tooth modules that establish very good contact between the teeth and the coil and that can well fill the available installation space in the electric machine. In contrast to the prior art, in many embodiments of coil-tooth modules according to the present invention, a potting compound can be dispensed between the coil and the teeth.

[0023] Compared to coil tooth modules according to the prior art, the coil tooth module presented herein has a larger contact surface between the coil and the teeth, since the bulk powder first fills the cavities and, if necessary, the gaps in the internal space, and is subsequently compacted by a pressing operation.

[0024] Commercially available materials such as aluminum or copper may be used as the coil material. Furthermore, the coil may be coated with an insulating layer. Ferrite particles or iron particles coated with an insulating layer (for example, in an SMC) may be used as the metal powder. Pure iron, iron silicon, iron nickel, or iron cobalt particles coated with an electrically insulating layer are suitable for an SMC. Ferrite can also be used as the substrate for an SMC.

[0025] Further embodiments can be derived from the following exemplary embodiments. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 2 is a diagram illustrating an example of a coil. [Figure 2A] FIG. 1 is a detailed view showing the inner contour of the coil mentioned above. [Figure 2B] FIG. 1 is a detailed view showing the inner contour of the coil mentioned above. [Figure 3A]10A-10C are schematic diagrams showing individual intermediate products during the manufacture of a coil tooth module. [Figure 3B] 10A-10C are schematic diagrams showing individual intermediate products during the manufacture of a coil tooth module. [Figure 3C] 10A-10C are schematic diagrams showing individual intermediate products during the manufacture of a coil tooth module. [Figure 4A] 10A-10C illustrate alternative stages during the manufacture of the coil tine module. [Figure 4B] 10A-10C illustrate alternative stages during the manufacture of the coil tine module. [Figure 4C] 10A-10C illustrate alternative stages during the manufacture of the coil tine module. [Figure 5A] 10A-10C illustrate alternative exemplary embodiments for manufacturing a coil tine module. [Figure 5B] 10A-10C illustrate alternative exemplary embodiments for manufacturing a coil tine module. [Figure 5C] 10A-10C illustrate alternative exemplary embodiments for manufacturing a coil tine module. [Figure 5D] 10A-10C illustrate alternative exemplary embodiments for manufacturing a coil tine module. [Figure 6A] FIG. 1 is a schematic diagram of a coil tine module. [Figure 6B] FIG. 1 is a schematic diagram of a coil tine module. [Figure 7] 1 is a schematic flowchart of a manufacturing method. DETAILED DESCRIPTION OF THE INVENTION

[0027] 1 shows a coil 1 that can be used in the coil tooth module or method of manufacturing thereof described herein. A detailed description of the coil can be found, for example, in EP 2 387 135 A2, the entire disclosure of which is incorporated herein by reference. The coil 1 can be, for example, cast or molded.

[0028] Coil 1 has a plurality of windings 3 and has a helical design. The windings 3 delimit an internal space 5 that extends from the lowermost winding 7 along the longitudinal direction 9 to the uppermost winding 11. In this example, the cross-section 13 that is delimited by the respective edges of the windings protruding towards the internal space and extends in a direction transverse to the longitudinal direction 9 is substantially constant over the height H of the coil. The cross-section is delimited by the inner contour of the internal space of the coil and has a substantially rectangular design with a width B and a length L. The windings of the coil have a band shape and similarly have a width b_S and a height h_S. In this example, the width and height of the windings are constant over the entire length of the coil, but in individual exemplary embodiments, the windings can have deviating widths b_S and heights h_S. The outer contour of the coil is delimited by its four side surfaces 15, as well as the upper and lower surfaces. The lowermost winding forms the lower surface 17 and the uppermost winding forms the upper surface 19. The cross-section of the coil that is variable along the windings can be configured, for example, such that the lowermost winding has a narrower width b_S1 and a greater height h_S1, the width b_S increases towards the top, and the height h_S decreases towards the top, such that, for example, the uppermost winding has a width b_S2>b_S1 and a height h_S2<h_S1. Since the inner contour is rectangular and constant over the longitudinal direction, the outer contour extends in the shape of a truncated pyramid. Such a configuration is shown, by way of example, in FIGS. 2A or 2B.

[0029] The helical coil illustrated herein is shaped such that the inner edge of each winding can abut against a tooth introduced into the internal space. If the coil were simply placed on top of an existing tooth, as described in the prior art, cavities would occur due to the need to reduce the dimensions of the tooth, which would adversely affect the thermal and magnetic properties of the coil-tooth module. In the coil-tooth module described herein, cavities are avoided in that the teeth are made by pressing bulk powder disposed within the internal space of the coil.

[0030] 2A and 2B show longitudinal cross sections through the coil 1. FIG. 2A shows multiple turns extending along the longitudinal direction and defining an interior space 5. The inner edge 21 of the coil turns may have a manufacturing-related radius or chamfer, which may further reduce contact between the inner edge 21 and the teeth. Additionally, the turns are bent 23 by a radius of curvature 25, which also makes contact with the prefabricated teeth more difficult. As can be seen from FIG. 2A, a gap 27 is created between two turns along the longitudinal direction. When the coil is pressed against one another along the longitudinal direction, the two turns can directly abut, with the radius or chamfer creating a gap 29. Filling of the interior space 5 with bulk powder can occur both in the relaxed state of the coil (FIG. 2A) and in the compressed state of the coil (FIG. 2B).

[0031] 3A, 3B, and 3C, a method for manufacturing a coil tooth module according to the present disclosure is described. In a simple exemplary embodiment of the method, the coil 31 is first placed on a press tool 33, which includes a lower press die 35 in which the coil 31 is held. SMC particles made of iron coated with a non-conductive layer are then injected into the interior space 37 of the coil 31 using a further tool until the powder, i.e., the particles, fill the entire interior space of the coil (FIG. 3A). To ensure a good, void-free filling, the powder can be excited to flow, for example, by vibrating or shaking the press die 35. In this way, the powder fills the interior space, including potential gaps, in a substantially void-free manner. In the subsequent pressing process, the SMC particles are plastically deformed and engage with each other, i.e., form-fitted, to form continuous teeth that directly abut the inner contour of the coil along the entire longitudinal direction 39, with the unpressed powder protruding from the interior space in this case. For this purpose, the powder is compacted by the upper plunger 41 of the press tool 33 (FIG. 3B). The pressure exerted between the press die and the plunger amounts to several hundred MPa in this process. The press die 35 is shown with a one-piece design, but it can also have a multi-piece design, in which, for example, the part 43 of the press die located directly below the teeth can be moved separately.

[0032] FIG. 3C shows a schematic diagram of a coil tooth module manufactured using this process. In addition to the coil 31, the teeth 45 pressed into the coil are visible. The manufacturing process ensures that the teeth 45 directly contact the coil's entire length and fill the gap between the two turns (see FIG. 2B). The large contact surface between the coil 31 and the teeth 45 ensures a good thermal connection between the two elements, ensuring heat dissipation during subsequent operation of the coil tooth module. Depending on the size of the gap, the teeth engage at least part of the inner contour of the coil from the backside, so that the teeth are also bonded to the coil in a form-fit manner. After the powder is pressed, a heat treatment can be performed, during which any residual pressure introduced into the teeth by the pressing operation can be reduced or eliminated. In this exemplary embodiment, the teeth 45 extend only within the inner contour of the coil; tooth material is not applied to the outer surface of the coil. This is also achieved by pressing the coil turns together, preventing the metal powder disposed within the inner contour from escaping between the turns to the outer side of the coil.

[0033] Another exemplary method for manufacturing a coil tooth module is described with reference to FIGS. 4A, 4B, and 4C. The press mold and the coil tooth module are shown in a longitudinal cross section along plane AA (see FIG. 1). In this manufacturing variant, a press tool is used that includes a press mold 47 with a bottom 49 and side walls 51. The side walls are spaced apart so that they mimic the outer contour or outer side of a pre-fabricated coil, so that the coil essentially fits into the press mold. In this example, the press mold is also shown as a single piece, but the bottom and side walls can be separately movable relative to each other, allowing the press mold to be adapted to different coils. In this example, metal powder, such as the coated iron described above, is first filled into the bottom of the press mold 47, forming a closing surface 52 that will later form the plate-like tooth base of the coil tooth module when pressed. To ensure as homogeneous a distribution as possible, the powder in the press mold is shaken to remove potential cavities from the area that will later become the tooth base. After the closing surface 52 is provided, the coil 53 is placed on the closing surface 52 and separated laterally by side walls 51. Because the coil windings have variable cross sections, the press die 47 has the shape of a four-sided truncated pyramid. Before the powder is filled into the internal space 55, the coil 53 can be compressed along its length so that no or only small gaps remain between the individual windings. In this way, the installation space required for the coil tooth module in the electric machine is kept small. The filling of the internal space 55 is also carried out while shaking the press die 47 to avoid cavities (FIG. 4A). After the internal space 55 is completely filled, the closing surface 57 is then poured onto the top winding, which, like the closing surface 52, forms a plate-like tooth tip as soon as the powder is pressed into it. After pressing (using a plunger, not shown), the coil tooth module is formed with dumbbell-shaped teeth, including a tooth root, a tooth axis, and a tooth tip. The tooth root and tooth tip are each dimensioned to terminate at or extend transversely beyond the adjacent outer contour of the coil, and a coil-tooth module thus produced is shown in Figure 4C.The coil tooth module 61 comprises teeth 63 with tooth bases 65, tooth shafts 67 and tooth tips 69, and the coil 53 completely surrounds the tooth shafts 67 and is held in a form-fit manner by the tooth bases 65 and tooth tips 69. The coil tooth module shown here is characterized, among other things, in that the teeth 63 are manufactured in one piece and engage with the tooth tips 69 and tooth bases 65 on the rear side of the coil 53 in the longitudinal direction 71.

[0034] In another exemplary embodiment of the manufacturing method illustrated with reference to FIGS. 5A, 5B, 5C, and 5D, the tooth root is first pre-pressed, in contrast to the example of FIGS. 4A, 4B, and 4C. For this purpose, SMC powder is first filled into a press mold 73 for the tooth root and then pressed. In this example, the tooth root 75 is designed as a plate 77 with an axial extension 79. The extension 79 is dimensioned to fit the inner contour of the coil of the coil tooth module. Afterwards (or after heat treatment), the tooth root is pressed into a press mold 81, a coil 83 is placed on top of the tooth root, and the internal space 85 of the coil 83 is filled with the same SMC powder that produced the tooth root (see FIG. 5A). The powder fills the entire internal space of the coil 83 and also forms a closing surface 86 on the coil 83, forming both the tooth root and the tooth tip during the pressing operation (see FIG. 5B). During pressing with the plunger 84, on the one hand, the SMC powder is pressed to form the tooth shank and tooth tip, and on the other hand, the tooth shank is integrally bonded or cryowelded to the prefabricated tooth root. A coil tooth module 87 thus produced is shown in FIG. 5C. Another embodiment is shown in FIG. 5D. This embodiment differs from the embodiment of FIG. 5C in that the plunger is designed differently and thus produces a tooth tip 90 including a dovetail guide 92. Because the plunger includes an undercut, the SMC powder can be filled into the plunger, for example, by lightly placing it on the tooth tip through its dovetail opening. The tooth is then compacted, including the dovetail guide. The dovetail guide can be inserted, for example, into a corresponding recess in the electric motor, thereby making excellent use of available installation space and simplifying the installation of the coil tooth module 94. In this example, the dovetail guide is located at the tooth tip, but the coil tooth module could also have a different guide including an undercut. As an alternative, the coil tooth module could include a recess corresponding to the guide including the undercut, such as the dovetail guide. The coil tooth modules can thus be inserted onto corresponding guides of the electric motor.

[0035] FIG. 6A shows a three-dimensional top view of a coil tooth module manufactured using one of the methods described above. The coil tooth module 100 comprises a coil 102 with a variable winding cross section, varying from bottom to top. A plate-shaped tooth tip 104 is located below the bottom winding, and a similarly plate-shaped tooth root 105 is placed above the top winding. The tooth shanks connecting the tooth tip and tooth root to each other are not visible in this view. The entire tooth, which is manufactured in one or two manufacturing stages as described above, are particularly well bonded to the coil in the area of ​​the inner contour. This is illustrated in FIG. 6B, which shows a cross section of the coil along section plane BB in the area of ​​the inner edge. The inner edges of the windings 106, 108, and 110 are slightly rounded, resulting in gaps 112 and 114 between the windings. These gaps are then filled by the tooth shanks 116, as the SMC powder was able to enter the gaps. Only afterwards was the tooth shaft compressed, allowing a particularly large contact surface between the tooth and the coil.

[0036] Additionally, further undercuts or recesses can be provided in the tooth root surface visible in Figure 6A, which can be used later to mount the coil tooth module in the electric machine. Furthermore, during the manufacture of the coil tooth module, or by means of drilling, cooling channels can be introduced into the teeth, through which a cooling medium can later be passed to the electric machine.

[0037] 7 again shows the steps of the manufacturing method in a schematic manner. First, in an optional step, SMC powder is filled into the press mold to form a closed surface (step 120). Then, a pre-formed coil is inserted into the press mold (step 140). The interior space of the coil is filled with SMC powder, optionally with shaking to eliminate small cavities (step 160). Then, a closed surface of powder is provided that forms the tooth tips (step 180). The entire system is then pressed under high pressure (step 200) and subsequently heat-treated (step 220). The coil tooth module can then be supplied for use or further processed.

Claims

1. 1. A method for manufacturing a coil tine module, comprising: a) providing a pre-fabricated helical coil, the helical coil having a plurality of turns defining an interior space extending longitudinally from a bottom turn to a top turn, the helical coil being a single-layer coil with no turns disposed one above the other when viewed from the inside out of the helical coil, the outer contour of the helical coil extending in the shape of a frustum of a pyramid, the inner contour of the interior space of the helical coil having a substantially rectangular shape in a plane perpendicular to the longitudinal direction, the helical coil having been formed into that shape by a printing or casting process; b) inserting the helical coil into a press die, the press die surrounding the pre-formed helical coil at an outer surface of the helical coil; c) filling the interior space defined by the helical coil with metal powder; d) pressing the metal powder to form teeth that directly abut the helical coil, the pressed metal powder filling not only the inner contour of the helical coil but also gaps between adjacent turns of the plurality of turns; A method comprising:

2. The method of claim 1 , wherein the turns of the helical coil have a band shape, the turns having widths and heights that vary along the longitudinal direction.

3. 3. The method of claim 2, wherein the bottom turn has a width b_S1 and a height h_S1, the width increasing along the longitudinal direction and the height decreasing along the longitudinal direction, such that the top turn has a width b_S2>b_S1 and a height h_S2<h_S1.

4. 4. A method according to any one of claims 1 to 3, wherein after the pressing operation to form the teeth there is a form fit between the particles of the metal powder pressed to form the teeth.

5. 5. The method of claim 1, wherein the helical coil has a cross-sectional shape that varies from turn to turn of the helical coil.

6. The method of claim 1 , wherein the helical coil is compressed longitudinally within the press die.

7. A method described in any one of claims 1 to 6, wherein the inner edge of each of the multiple turns of the helical coil is rounded, and the pressed metal powder fills the gaps between the inner edges of adjacent turns.

8. 8. The method according to claim 1, wherein the coil tooth modules are heat treated after the metal powder is pressed.

9. 9. The method according to claim 1, wherein a powder material for forming a tooth base or a pre-fabricated tooth base is introduced into the press mold before the helical coil is inserted into the press mold.

10. 10. The method of claim 1, wherein the metal powder filling the internal space completely fills the internal space, thereby forming a tooth tip during pressing.

11. 11. The method of claim 1, wherein the teeth engage the backside of at least one coil portion.

12. 1. A coil tooth module comprising: a helical coil; and teeth disposed within an inner contour of the helical coil, the teeth abutting the helical coil and having pressed metal powder, the helical coil having a plurality of turns defining an interior space extending longitudinally from a bottom turn to a top turn, the helical coil being a single-layer coil with no turns disposed one above the other when viewed from the inside out of the helical coil, the outer contour of the helical coil extending in the shape of a frustum of a pyramid, the inner contour of the interior space of the helical coil having a substantially rectangular shape in a plane perpendicular to the longitudinal direction, the helical coil being formed into this shape using a printed or cast coil, the pressed metal powder filling not only the inner contour of the helical coil but also gaps between adjacent turns of the plurality of turns.

13. The coil tine module of claim 12 wherein there is a form fit between particles of the metal powder pressed to form the tines.

14. The coil tooth module according to claim 12 or 13, wherein the helical coil comprises an electrically conductive material and the metal powder is a soft magnetic material or a soft magnetic alloy.

15. A coil tooth module described in any one of claims 12 to 14, wherein the inner edge of each of the multiple turns of the helical coil is rounded, and the pressed metal powder fills the gaps between the inner edges of adjacent turns.

16. A coil tine module manufactured according to any one of claims 1 to 11.

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