Electrotechnical coil, method for producing same, and electromagnet or electric machine comprising at least one such coil

Abstract

The invention relates to an electrotechnical coil, to a method for producing same, and to an electromagnet or an electric machine comprising at least one such coil. The aim of the invention is to produce and use an electrotechnical coil for achieving an increased slot fill factor reliably and easily in a reproducible and economical manner. This is achieved in that the method according to the invention has the steps: step A: casting an electrotechnical coil with at least one winding which runs about a coil axis; and step B: shaping the coil, thereby changing the cross-section Q, Q′ of the at least one winding, such that the centroid FS, FS′ of the cross-section Q, Q′ of the at least one winding is displaced at least partly in the radial direction R relative to the coil axis A.

Claims

1. A method for producing an electrotechnical coil, comprising the following steps: Step A: casting a coil with at least one winding which runs about a coil axis; Step B: shaping the coil, thereby changing a cross-section of the at least one winding, such that a center of area of the cross-section of the at least one winding is displaced at least partly in a radial direction relative to the coil axis.

2. The method according to claim 1, wherein Step A comprises at least one of the following sub-steps: Step A1: providing a reusable negative mold, by embedding a positive model in an embedding medium; Step A2: casting a coil material into the negative mold, preferably supported by a gravitation and/or pressure, preferably when the negative mold is subjected to negative pressure and/or in a protective gas atmosphere, particularly preferably in precision casting, centrifugal casting, vacuum casting or low-pressure casting; Step A3: curing the cast coil material in the negative mold to form the coil; Step A4: removing the coil from the negative mold; Step A5: cleaning the coil; Step A6: soft annealing the coil; and Step A7: electrically insulating the at least one winding of the coil, by immersing the coil in insulation varnish or by coating or sheathing the coil with an insulation layer.

3. The method according to claim 2, wherein the embedding medium is sand or of metallic material, and wherein the positive model is removed again after an impression in the embedding medium or remains as a lost mold in the embedding medium.

4. The method according to claim 1, wherein Step B comprises at least one of the following sub-steps: Step B1: providing a multi-part shaping tool which, in a composite state, forms a cavity for receiving the coil, wherein the cavity is matched to an inner contour and/or an outer contour of the coil, wherein a punch forms an upper part of the shaping tool and/or a die forms a lower part of the shaping tool; Step B2: arranging the coil in the shaping tool in such a way that the coil bears radially on an inside and/or radially on an outside against the shaping tool, wherein the coil bears radially on an inside against the punch and/or bears radially on an outside against the die; Step B3: moving at least two parts of the multi-part shaping tool relative to one another along the coil axis while reducing a volume of the cavity, wherein the punch enters the die along the coil axis; Step B4: shaping the coil by compressing the coil along the coil axis, wherein windings of the coil are pressed against one another starting radially on the inside, so that the coil material is displaced outwards in the radial direction with respect to the coil axis; Step B5: changing the cross-section of the at least one winding so that an angle which the upper side and/or the lower side of the cross-section encloses with a plane intersecting the coil axis perpendicularly changes and/or decreases by between 1° and 5° with respect to a non-deformed state; Step B6: cutting off a sprue of the coil; Step B7: forming at least one connection region for an electrical contacting of the coil by embossing; Step B8: calibrating the coil to a final contour, wherein the shaping tool calibrates the coil radially on the inside and/or radially on the outside and/or at the upper and/or lower axial end with respect to the coil axis, wherein the punch calibrates the coil radially on the inside and/or at the upper axial end and/or the die calibrates the coil radially on the outside and/or at the lower axial end; and Step B9: electrically insulating the at least one winding of the coil by immersing the coil in an insulation varnish or by coating or by sheathing the coil with an insulation layer.

5. The method according to claim 4, wherein the cross-section of the at least one winding of the coil cast in Step A tapers inwards or outwards in the radial direction with respect to the coil axis.

6. The method according to claim 5, wherein the cross-section of the at least one winding of the coil cast in Step A is isosceles polygonal and/or conical and/or trapezoidal.

7. The method according to claim 4, wherein the inner contour and/or the outer contour of the coil obtained after Step A and/or after Step B corresponds/correspond to a lateral surface of a cylinder, cuboid, truncated cone or truncated pyramid.

8. The method according to claim 4, wherein the center of area of the cross-section of the at least one winding is displaced in Step B in the radial direction inwards or outwards with respect to the coil axis.

9. The method according to claim 4, wherein the coil material is displaced so that gaps between the windings of the coil are reduced or eliminated, and wherein Step B5 occurs during Step B4.

10. The method according to claim 1, wherein an angle which an upper side and/or a lower side of the cross-section of the at least one winding of the coil cast in Step A encloses with a plane intersecting the coil axis perpendicularly is between 1° and 5°.

11. The method according to claim 1, wherein the electrotechnical coil is shaped in Step B so as to occupy at least 95% of a volume of a body having the same inner and outer contour.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic sectional view of a cast and cured electrotechnical coil with four windings and constant pitch, the cross-sections of the windings tapering outwards in the radial direction with respect to the coil axis and being in the form of isosceles trapezes.

(2) FIG. 2 shows a schematic view of a two-part press tool with a rotationally symmetric punch as upper part and a rotationally symmetric die as lower part.

(3) FIG. 3 shows a schematic view of an electrotechnical coil arranged in the press tool and supported radially on the inside and radially on the outside by the press tool in the state prior to shaping, the pitch of the coil being neglected for representation purposes.

(4) FIG. 4 shows a schematic view of the electrotechnical coil arranged in the press tool and supported radially on the inside and radially on the outside in the state after shaping, the cross-sections of the windings being designed to be substantially rectangular and the pitch of the coil being neglected for representation purposes.

(5) FIG. 5 shows, in a schematic view, the change in the cross-section of the winding caused by shaping the coil, starting from the shape of an isosceles trapeze (continuous contour line) into a rectangular shape (dashed contour line), as well as the associated displacement of the center of area of the cross-section of the winding in the radial direction outwards with respect to the coil axis.

DETAILED DESCRIPTION

(6) The preferred embodiment of the present invention is described in detail below using the attached figures. The person skilled in the art understands that the features described in connection with the embodiment do not have to be realized in their entirety in order to realize the claimed invention, but can also be realized independently of each other in other configurations. In particular, some of the features described in the embodiment may be omitted or other features may be added.

(7) In preparation for the casting of the coil 1 in step A, the final geometry of the electrotechnical coil 1 is designed, for example using CAD. Depending on the concrete application, the number, radius, pitch, cross-sectional shape and cross-sectional area of the windings of the coil are determined and the coil geometry is defined in the installation state depending on the available installation space. It goes without saying that the number, radii, pitch, cross-sectional shape and cross-sectional area of the windings of the coil can be changed at will, as long as this does not contradict the teaching claimed. The described embodiment refers to a method for the production of an electrotechnical coil 1 with four windings running around the coil axis A.

(8) On the basis of the final geometry, the casting geometry of the electrotechnical coil 1 is designed with simulated reversal of the shaping process carried out in step B and in consideration of demolding chamfers and material shrinkage. The distance between the windings of the coil 1 is defined by the feasible shaping degree, the technical casting requirements and the type of insulation application.

(9) In step A1 of the production process, a reusable negative mold is provided. For this purpose, a positive model is embedded in an embedding medium such as sand or metallic material or bulk material, the positive model being removed again after leaving its imprint in the embedding medium or remaining as a lost mold in the embedding medium.

(10) The casting of the coil material into the negative mold in step A2 is carried out supported by gravitation and preferably pressure, e.g. under a protective gas atmosphere, while the negative mold may be subjected to negative pressure. The coil 1 according to the invention can be produced in particular in precision casting, centrifugal casting, vacuum casting or low-pressure casting.

(11) After curing of the cast coil material in the negative mold (step A3), the cured and cooled coil 1 is removed from the negative mold (step A4), freed of any residues of the embedding medium and cleaned (step A5) and, if necessary, soft annealed in preparation for the subsequent shaping in step B (step A6).

(12) The electrical insulation of the windings of the coil 1 (step A7) can optionally be carried out before or after the coil 1 has been shaped in step B and is achieved, for example, by immersing the coil 1 in insulation varnish, e.g. in the CVD or PVD process, or by coating or sheathing it with an insulation layer.

(13) A schematic sectional view of an exemplary electrotechnical coil 1, which was produced in casting technology in the sequence of steps A1 to A7/A8, is shown in FIG. 1. The sectional view shown there runs along the coil axis A or in a plane which encloses the coil axis A. In the view shown in FIG. 1, the coil 1 comprises a cylindrical inner and outer contour and a total of four windings with a constant cross-sectional shape, wherein the pitch or distance of the windings from each other along the coil axis A is reduced to a minimum in conformity with the technical casting possibilities. The cross-section Q of each winding tapers outwards in the radial direction with respect to the coil axis A and is in the form of an isosceles trapeze, the parallel base sides of which are aligned parallel to the coil axis A and the inner angles of which respectively have the same size on the same parallel base side.

(14) FIG. 5 shows in a continuous contour line the cross-sectional shape Q of a winding of the coil 1 before the shaping process carried out in step B. For example, the angle α which the upper side and the lower side of the cross section Q of the winding of the coil 1 cast in step A enclose with a plane E intersecting the coil axis A perpendicularly is for instance 1.5° and corresponds to the demolding chamfers of the winding. With respect to a winding axis that defines the center of the smallest rectangle into which the cross-section Q of the winding fits, the center of area FS of the non-deformed cross-section Q of the winding is offset radially inwards in the direction of the coil axis A.

(15) The shaping carried out in step B changes the cross-section Q′ of the windings of the coil 1 in such a way that the center of area FS' of the changed cross-section Q′ is displaced with respect to the coil axis A in radial direction relative to the center of area FS of the unchanged cross-section Q.

(16) In step B1, a two-part shaping tool 2, 3 shown schematically in FIG. 2 with a rotationally symmetric punch 2 as upper part and a rotationally symmetric die 3 as lower part is provided for this purpose. The punch 2 and the die 3 in an assembled state form a cavity matched to the inner and outer contours of the coil 1 for receiving the coil 1.

(17) When the coil 1 is arranged in the cavity of the shaping tool 2, 3 (step B2), the punch 2 is located radially on the inside and the die 3 is located radially on the outside on the coil 1. This condition is shown schematically in FIG. 3.

(18) Starting from the schematic state shown in FIG. 3, the punch 2 is moved along the coil axis A in step B3, thereby reducing the volume of the cavity, and enters the die 3.

(19) The plastic shaping of the coil 1 is carried out in steps B4 and B5 by compressing the coil 1 along the coil axis A. The punch 2 immerses from above into the die 3 and flattens the conical areas of the windings of the coil 1. The windings of the coil 1 are pressed against each other starting radially on the inside, so that the coil material is displaced outwards in the radial direction R with respect to the coil axis A until the gaps between the windings are reduced or eliminated. During the shaping process, the cross-section Q, Q′ of the windings is changed so that the angle α which the upper and lower sides of the cross-section Q, Q′ respectively enclose with a plane E intersecting the coil axis A perpendicularly is reduced to 0° or reduced by 1.5 compared to the non-deformed state. This change in the cross-section Q, Q′ of the winding causes the center of area FS, FS' of the cross-section Q, Q′ to be shifted in the radial direction R with respect to the coil axis A. The R.sub.FS′ radius of the center of area FS' after shaping is greater than the R.sub.FS radius of the center of area before shaping. The deformed cross-section Q′ of the winding of the coil 1 after step B is shown in FIG. 5 in a dashed line. The shaping carried out in step B compresses the coil 1 in such a way that it occupies at least 95% of the volume of a body with the same inner and outer contour.

(20) In the course of shaping, for example, a sprue of the coil 1 can be cut off in a step B6 and/or a connection area for electrical contacting of the coil 1 can for instance be formed by embossing in a step B7.

(21) In step B8, for example, the coil 1 is calibrated to the final contour by the punch 2 forming the coil 1 radially on the inside and at the upper axial end into the final contour, while the die 3 forms the coil 1 radially on the outside and at the lower axial end into the final contour. During calibration, surface irregularities are smoothed out.

(22) If not already carried out before, the electrical insulation of the windings of the coil 1 is carried out in step B9.

(23) The effects and advantages of the invention can be summarized as follows:

(24) The most important advantage is the economic efficiency of manufacturing shaping coils with low use of production equipment. In addition, there are the following advantages:

(25) The use of reusable tools is possible during the technical casting production of the preform since rather large demolding chamfers can be used

(26) This result in maximum productivity due to continuous production sequence

(27) Improvement of the surface quality for subsequent coating

(28) Reduction of residual porosities in the casting coil

(29) Increasing the groove filling factor

(30) Additional improvement of the heat dissipation path

(31) Reduction of the minimum possible winding thickness compared to casting the coil in final contour

(32) Setting of narrow geometric tolerances

(33) High process stability

(34) Combination with other process steps such as cutting off the sprue system

(35) Combination with embossing/forming processes of the connection areas for electrical contacting

(36) The invention also applies to coated materials, where a subsequent insulation step is not necessary.

(37) The preform is produced by primary forming. By using ground samples (destructive material testing) on winding cross-sections, it can be proven whether a coil or its preform has been produced by shaping.

(38) Proof of the technical casting production of the preform can be established on the basis of distinctive and always occurring defects (pores, oxides, possibly also quenching structure on the surface) in the casting structure.

(39) The field of application of the invention regards coils for electric motors which are mass-produced. Since electric drives and generators show a steadily increasing sales volume and a constantly increasing penetration of the different industries, all areas of automotive engineering, mechanical engineering, shipping, aviation as well as consumer areas are included.

LIST OF REFERENCE SIGNS

(40) 1 coil 2 punch 3 die angle between upper/lower side of the cross-section and plane perpendicular to the coil axis A coil axis E plane perpendicular to the coil axis FS center of area (before shaping) FS' center of area (after shaping) Q cross-section of the winding (before shaping) Q′ cross section of the winding (after shaping) R radial direction R.sub.FS radius of the center of area (before shaping) R.sub.FS′ radius of the center of area (after shaping)