Abstract
The invention relates to a coil-tooth module and to a method for the production thereof. A prefabricated coil is filled with a metallic powder, and this powder is subsequently pressed to form a tooth, so that a coil-tooth module is created, in which the tooth directly abuts the coil.
Claims
1. A method for producing a coil-tooth module, the method comprising: inserting a helical coil into a press mold; filling an inner contour delimited by the coil with a metallic powder; and pressing the metallic powder to form a tooth that directly abuts the coil.
2. The method according to claim 1, wherein, after pressing the metallic powder to form a tooth, a form fit is present between at least two particles of the metallic powder that is pressed to form the tooth.
3. The method according to claim 1, wherein a cross-sectional surface of the inner contour of the helical coil changes along a longitudinal direction of an interior space of the press mold.
4. The method according to claim 1, wherein the press mold encloses the helical coil at an outer surface thereof.
5. The method according to claim 1, wherein the helical coil is compressed in the press mold along a longitudinal direction.
6. The method according to claim 1, wherein the pressed metallic powder further fills an interstice between different coils sections of the helical coil.
7. The method according to claim 1, wherein the coil-tooth module is subjected to heat treatment after the metallic powder has been pressed.
8. The method according to claim 1, wherein a powder material for forming a tooth root, or a prefabricated tooth root is introduced into the press mold prior to inserting the helical coil into the press mold.
9. A method according to claim 1, wherein the metallic powder completely fills the inner contour, and covers a top side of the helical coil, so that a tooth tip is formed during the pressing of the metallic powder.
10. The method according to claim 1, wherein the tooth engages behind at least one coil section of the helical coil.
11. A coil-tooth module, comprising: a helical coil: and a tooth arranged in an inner contour of the coil, wherein the tooth abuts the coil and comprises a pressed metallic powder.
12. The coil-tooth module according to claim 11, wherein a form fit exists between particles of the metallic powder that is pressed to form the tooth.
13. The coil-tooth module according to claim 11, wherein the coil comprises an electrically conductive material.
14. (canceled)
15. The coil tooth module according to claim 13, wherein the electrically conductive material is at least one of: aluminum, copper, or an alloy thereof.
16. The coil tooth module according to claim 13, wherein the metallic powder is a soft magnetic material or a soft magnetic alloy.
17. A method for producing a coil-tooth module, the method comprising: inserting a helical coil into a press mold; filling an inner contour delimited by the coil with a metallic powder; filling an interstice between at least two different sections of the helical coil with the metallic powder; pressing the metallic powder to form a tooth that directly abuts the coil; and subjecting the coil-tooth module to a heat treatment.
18. The method of claim 17, wherein after pressing the metallic powder to form a tooth, a form fit is present between at least two particles of the metallic powder that is pressed to form the tooth.
19. The method of claim 17, wherein a cross-sectional surface of the inner contour of the helical coil changes along a longitudinal direction of an interior space of the press mold.
20. The method of claim 17, wherein the press mold encloses the helical coil at an outer surface thereof.
21. The method of claim 17, wherein the helical coil is compressed in the press mold along a longitudinal direction, wherein a powder material for forming a tooth root, or a prefabricated tooth root is introduced into the press mold prior to inserting the helical coil into the press mold, and wherein the metallic powder completely fills the inner contour and covers a top side of the helical coil so that a tooth tip is formed during the pressing of the metallic powder.
Description
[0026] In the drawings:
[0027] FIG. 1 shows an example of a coil;
[0028] FIG. 2 show multiple detailed views of the inner contour of the above coil;
[0029] FIG. 3 show a schematic illustration of individual intermediate products during the production of a coil-tooth module;
[0030] FIG. 4 show an illustration of alternative steps during the production of a coil-tooth module;
[0031] FIG. 5 show an alternative exemplary embodiment for the production of a coil-tooth module;
[0032] FIG. 6 show a schematic view of a coil-tooth module;
[0033] FIG. 7 shows a schematic flow chart for a production method.
[0034] FIG. 1 shows a coil 1, which can be used in the coil-tooth module described here or the production method thereof. A detailed description of the coil can be found in EP 2 387 135 A2, for example, the entire disclosure of which is hereby included in this application by reference. The coil 1 can be cast or formed, for example.
[0035] The coil 1 has a plurality of turns 3 and has a helical design. The turns 3 delimit an interior space 5, which extends from the lowermost turn 7, along a longitudinal direction 9, to the uppermost turn 11. In the present example, the cross-sectional surface 13 that is delimited by the respective edge of a turn protruding toward the interior space and extends transversely to the longitudinal direction 9 is substantially constant across the height H of the coil. The cross-sectional surface is delimited by the inner contour of the interior space of the coil and has a substantially rectangular design, having a width B and a length L. The turns of the coil have a band shape and likewise have a width b_S and a height h_S. In the present example, the width and the height of the turns are constant across the entire length of the coil, however the turns can have a deviating width b_S and height h_S in individual exemplary embodiments. The outer contour of the coil is delimited by the four lateral surfaces 15 thereof and an upper and a lower surface. The lowermost turn forms the lower surface 17, and the uppermost turn forms the upper surface 19. A cross-section of a coil which is variable along the turns can, for example, be configured in such a way that the lowermost turn has a lower width b_S1 and a greater height h_S1, and the width b_S increases toward the top, and the height h_S decreases toward the top, so that the uppermost turn, for example, has a width b_S2>b_S1 and a height h_S2<h_S1. The inner contour remains rectangular and constant across the longitudinal direction, so that the outer contour extends in the shape of a frustum of a pyramid. Such a configuration is shown by way of example in FIG. 2A or 2B.
[0036] The helical coil shown here is shaped in such a way that the inner edge of each turn could abut a tooth to be introduced into the interior space. If the coil, as is described in the prior art, is merely put onto an existing tooth, cavities arise due to the required undersized dimension of the tooth, which negatively impact the thermal and magnetic properties of the coil-tooth module. The coil-tooth module described here avoids the cavities in that the tooth is pressed from bulk powder disposed in the interior space of the coil.
[0037] FIG. 2 show longitudinal sections through the coil 1. FIG. 2A shows a plurality of turns that extend along the longitudinal direction and delimit the interior space 5. The inner edges 21 of the turns of the coil have manufacturing-related roundings or chamfers, which can further reduce the contact between the inner edge 21 and a tooth. In addition, a radius of curvature 25, which likewise makes contact with a prefabricated tooth more difficult, results in the bends 23 of a turn. It is furthermore apparent from FIG. 2A that a gap 27 arises along the longitudinal direction between two turns. If the coil is pressed together along the longitudinal direction, two turns can directly abut, and interstices 29 arise due to the roundings or chamfers. The filling of the interior space 5 with bulk powder can take place both in the relaxed state of the coil (FIG. 2A) or in the compressed state of the coil (FIG. 2B).
[0038] Based on FIG. 3, the production method of a coil-tooth module according to the present description is described. In a simple exemplary embodiment of the method, the coil 31 is initially arranged on a press tool 33, wherein the press tool comprises a lower press mold 35 in which the coil 31 is held. Thereafter, SMC particles made of iron, which was coated with a non-conducting layer, is poured into the interior space 37 of the coil 31 by means of a further tool until the powder, or the particles, fills or fill the entire interior space of the coil. (FIG. 3A). To enable a good, cavity-free filling, the powder can, for example, be excited to flow by vibration or shaking of the press mold 35. In this way, the powder fills the interior space, including potential interstices, in a substantially cavity-free manner. The unpressed powder will protrude from the interior space in this case, since the SMC particles are plastically deformed in the subsequent pressing process and become engaged with one another, that is, are joined in a form-fit manner, to form a contiguous tooth, which directly abuts the inner contour of the coil across the entire longitudinal direction 39. For this purpose, the powder is compacted with an upper plunger 41 of the press tool 33 (FIG. 3B). The pressure applied between the press mold and the plunger is several hundred MPa in the process. Even though the press mold 35 is shown in a one-piece design, it may also have a multi-piece design, wherein, for example, the portion 43 of the press mold located directly beneath the tooth can be moved separately.
[0039] FIG. 3C schematically shows a coil-tooth module produced by means of the process. In addition to the coil 31 mentioned above, the tooth 45 pressed inside the coil is now visible. Due to the manufacturing process, the tooth 45 directly abuts the turns across the entire longitudinal direction of the coil, and the interstices (see FIG. 2B) between two turns are filled. The large contact surface between the coil 31 and the tooth 45 ensures a good thermal connection of the two elements, and thermal heat dissipation of the coil-tooth module is ensured during later operation. Depending on the size of the interstices, the tooth engages behind at least in portions of the inner contour of the coil so that the tooth is also joined to the coil in a form-fit manner. After the powder has been pressed, a heat treatment can be carried out, during which the residual stresses introduced into the tooth due to the pressing operation can be reduced or decreased. In the present exemplary embodiment, the tooth 45 extends exclusively within the inner contour of the coil, and the tooth material is not applied to the outer surfaces of the coil. This is also achieved since the turns of the coil can be pressed against one another so that the metal powder disposed inside the inner contour cannot find its way between the turns to the outer lateral surfaces of the coil.
[0040] Another exemplary production method of a coil-tooth module is to be described based on FIG. 4. The press mold and the coil-tooth module are shown in a longitudinal sectional view along plane A-A (see FIG. 1). In this production variant, a press tool comprising a press mold 47, including a bottom 49 and lateral walls 51, is used. The lateral walls are spaced apart in such a way that they emulate the outer contour or the outer lateral surfaces of the prefabricated coil, so that the coil is substantially fitted into the press mold. Even though the press mold is also shown in one piece in this example, the bottom and the lateral walls can be separately movable with respect to each other, so that the press mold can be adapted to different coils. In this example, initially a metallic powder, such as the aforementioned coated iron, is filled into the bottom of the press mold 47 and forms a closed surface 52, which forms a plate-shaped tooth root of the coil-tooth module later in the pressed state. To achieve a distribution as homogeneous as possible, the powder in the press mold is shaken, so that potential cavities are shaken from what will later be the tooth root. After the closed surface 52 has been provided, the coil 53 is placed onto the closed surface 52 and laterally delimited by the lateral walls 51. The press mold 47 has the shape of a four-sided frustum of a pyramid since the turns of the coil have a variable cross-section. Prior to the interior space 55 being filled with powder, the coil 53 can be compressed along the longitudinal direction so that no gap, or merely a small gap, remains between the individual turns. In this way, the required installation space in the electrical machine needed by the coil-tooth module is kept small. The filling of the interior space 55 is likewise carried out while shaking the press mold 47 to avoid cavities (FIG. 4A). The interior space 55 is filled completely, and afterwards a closed surface 57 is poured onto the uppermost turn, which, similarly to the closed surface 52, forms a plate-shaped tooth tip as soon as the powder has been pressed. After pressing (by means of a plunger, which is not shown), a coil-tooth module is thus formed, which comprises a dumbbell-shaped tooth including a tooth root, a tooth stem and a tooth tip. The tooth root and the tooth tip are each dimensioned in such a way that they end with the adjoining outer contour of the coil or protrude beyond thereof transversely to the longitudinal direction. An accordingly produced coil-tooth module is shown in FIG. 4C. The coil-tooth module 61 comprises a tooth 63 including a tooth root 65, a tooth stem 67, and a tooth tip 69, wherein the coil 53 completely encloses the tooth stem 67 and is held in a form-fit manner by the tooth root 65 and the tooth tip 69. The coil-tooth module shown here is characterized, among other things, in that the tooth 63 is produced in one piece and engages behind the coil 53 with the tooth tip 69 and the tooth root 65 in the longitudinal direction 71.
[0041] In another exemplary embodiment of a production method, which is illustrated based on FIG. 5, the tooth root, in contrast to the example of FIG. 4, is initially prepressed. For this purpose, initially an SMC powder is filled into a press mold 73 for a tooth root and then pressed. In the present example, the tooth root 75 is designed as a plate 77 having a stem-like extension 79. The extension 79 is dimensioned to fit into the inner contour of the coil of the coil-tooth module. Thereafter (or after heat treatment), the tooth root is put into a press mold 81, the coil 83 is put onto the tooth root, and the interior space 85 of the coil 83 is filled with the same SMC powder of which the tooth root was produced (see FIG. 5A). The powder fills the entire interior space of the coil 83 and additionally forms a closed surface 86 on the coil 83 to form both a tooth stem and a tooth tip during the pressing operation (see FIG. 5B). During the pressing by means of the plunger 84, on the one hand the SMC powder is pressed to form a tooth stem and a tooth tip and, on the other hand, the tooth stem is integrally joined or cold-welded to the prefabricated tooth root. The so-produced coil-tooth module 87 is shown in FIG. 5C. Another embodiment is shown in FIG. 5D. The embodiment differs from the embodiment of FIG. 5C in that the plunger is designed differently, and thus produces a tooth tip 90 which includes a dovetail guide 92. Since the plunger includes an undercut, the SMC powder can, for example, be filled into the plunger, which is placed lightly onto the tooth tip, via the dovetail opening thereof. The tooth, including the dovetail guide, is then compacted. The dovetail guide can, for example, be inserted into a corresponding recess of an electric motor, so that the available installation space is utilized very well, and the mounting of the coil-tooth module 94 is simple. Even though a dovetail guide is arranged at the tooth tip in the present example, the coil-tooth module can also have a different guide including an undercut. As an alternative, the coil-tooth module can also include a recess that corresponds to a guide including an undercut, such as a dovetail guide. The coil-tooth module can then be inserted onto a corresponding guide of the electric motor.
[0042] FIG. 6A shows a three-dimensional top view onto a coil-tooth module produced by means of one of the above-described methods. The coil-tooth module 100 comprises a coil 102 having a variable turn cross-section, which changes from the bottom to the top. The plate-shaped tooth tip 104 is arranged beneath the lowermost turn, and the tooth root 105, which is likewise plate-shaped, is situated above the uppermost turn. In this illustration, the tooth stem, which connects the tooth tip and the tooth root to one another, is not visible. The entire tooth, as mentioned above, was produced in one or two manufacturing steps and is coupled particularly well to the coil in the region of the inner contour. This is illustrated based on FIG. 6B, which shows a section of the cut surface B-B in the region of an inner edge of the coil. The inner edges of the turns 106, 108 and 110 are slightly rounded, so that interstices 112 and 114 arise between the turns. These interstices are likewise filled by the tooth stem 116 since the SMC powder was able to enter the interstices. Only then the tooth stem was compacted, and the particularly large contact surface between the tooth and the coil made possible.
[0043] In addition, further undercuts or recesses can be disposed on the surface of the tooth root visible in FIG. 6A, which can be used to later attach the coil-tooth module in an electrical machine. Furthermore, a cooling channel can be introduced into the tooth during the production of the coil-tooth module or by means of boring, through which a cooling medium can later flow in the electrical machine.
[0044] FIG. 7 is to schematically address the steps of the production method again. First, in an optional step, SMC powder is filled into a press mold and forms a closed surface (step 120). Thereafter, a prefabricated coil is inserted into the press mold (step 140). The interior space of the coil is filled with SMC powder, wherein the filling takes place with optional shaking, so that small cavities are eliminated (step 160). Thereafter, a closed powder surface for forming a tooth tip is provided (step 180). The entire system is then pressed under high pressure (step 200) and subsequently subjected to heat treatment (step 220). The coil-tooth module can then be supplied to its use or be further processed.
