Inductive communication coil design

Abstract

A coil is produced by winding a wire that is clad with an electrical insulation so as to form a coil bundle of successive windings. The coil bundle has at least one first winding formed by a first end section of the wire and at least one second winding formed by a second end section of the wire. A portion of the electrical insulation of the at least one first winding is removed to expose a portion of the first end section of the wire for forming a first electrical contact of the coil, and a portion of the electrical insulation of the at least one second winding is removed to expose a portion of the second end section of the wire for forming said second electrical contact of the coil. There is also described a coil.

Claims

1. A method for producing a coil, the method comprising: winding a wire clad with an electrical insulation so as to form a coil bundle formed of successive windings, the coil bundle including at least one first winding formed by a first end section of the wire and at least one second winding formed by a second end section of the wire; removing at least a portion of the electrical insulation of the at least one first winding to expose a portion of the first end section of the wire for forming a first electrical contact of the coil; and removing at least a portion of the electrical insulation of the at least one second winding to expose a portion of the second end section of the wire for forming a second electrical contact of the coil.

2. The method according to claim 1, wherein: the coil bundle comprises a plurality of successive first windings formed by the first end section of the wire; and the step of removing at least a portion of the electrical insulation of the at least one first winding comprises removing at least a portion of the electrical insulation of one or of several first windings to expose a portion of the first end section of the wire for forming the first electrical contact of the coil; and/or the coil bundle comprises a plurality of successive second windings formed by the second end section of the wire; and the step of removing at least a portion of the electrical insulation of the at least one second winding comprises removing at least a portion of the electrical insulation of one or of several second windings to expose a portion of the second end section of the wire for forming the second electrical contact of the coil.

3. The method according to claim 2, wherein: the first windings form a plurality of layers arranged on top of one another in a radial direction of the coil bundle, wherein each layer comprises a plurality of adjacent windings arranged side by side in an axial direction of the coil bundle, and wherein the first windings only extend over a part of a length of the coil bundle in the axial direction of the coil bundle and only extend over a part of a width of the coil bundle in the radial direction of the coil bundle; and/or the second windings form a plurality of layers arranged on top of one another in the radial direction of the coil bundle, wherein each layer comprises a plurality of adjacent windings arranged side by side in the axial direction of the coil bundle, and wherein the second windings only extend over a part of the length of the coil bundle in the axial direction of the coil bundle and only extend over a part of the width of the coil bundle in the radial direction of the coil bundle.

4. The method according to claim 2, wherein the first windings form a region of an outer surface of the coil bundle, and/or wherein the second windings form a region of the outer surface of the coil bundle.

5. The method according to claim 2, wherein the second windings encompass the first windings.

6. The method according to claim 2, wherein the first windings face the second windings in an axial direction of the coil bundle.

7. The method according to claim 6, wherein the first windings and the second windings each form a protrusion of the coil bundle, which protrusions protrude in opposite directions from the coil bundle.

8. The method according to claim 7, wherein the protrusions project in a radial direction of the coil bundle.

9. The method according to claim 1, which comprises winding the wire on a bobbin.

10. The method according to claim 9, wherein the bobbin comprises fastening elements for holding the at least one first winding and the at least one second winding.

11. The method according to claim 10, wherein: the bobbin comprises an annular wall member extending along an axis, the annular wall member is formed with a first and a second circumferential edge extending around the axis; the fastening elements for holding the at least one first winding are two first recesses formed into the first circumferential edge and two first recesses formed into the second circumferential edge; the first end section of the wire is wound into the four first recesses to form the at least one first winding; and the fastening elements for holding the at least one second winding are two second recesses formed into the first circumferential edge and two further second recesses formed into the second circumferential edge of the annular member; and the second end section of the wire is wound into the four second recesses to form said at least one second winding.

12. The method according to claim 11, wherein the at least one first winding is connected to the at least one second winding via intermediary windings that are wound about the axis of the annular wall member onto the annular wall member after winding of the at least one first winding and before winding of the at least one second winding.

13. The method according to claim 11, wherein the at least one first winding is wound about a winding axis that is different from the axis of the annular wall member and/or wherein the at least one second winding is wound about a winding axis that is different from the axis of the annular wall member.

14. The method according to claim 13, wherein the winding axis of the at least one first winding and the winding axis of the at least one second winding extend perpendicular to the axis of the annular wall member.

15. The method according to claim 1, which comprises embedding the coil bundle into an electrically insulating material.

16. The method according to claim 15, wherein: the step of removing a portion of the electrical insulation of the at least one first winding also comprises removing a portion of the insulating material so as to expose the portion of the first end section of the wire for forming the first electrical contact of the coil; and/or the step of removing a portion of the electrical insulation of the at least one second winding also comprises removing a portion of the insulating material so as to expose the portion of the second end section of the wire for forming the second electrical contact of the coil.

17. The method according to claim 1, which comprises forming the coil bundle by winding the wire on a core of an arbor, the arbor further comprising two opposing plates connected by the core, and, after the coil bundle has been formed, removing the coil bundle from the arbor.

18. The method according to claim 17, wherein the arbor is formed with at least one recess for receiving the first windings so that the first windings form a protrusion of the coil bundle upon winding the wire into the recess.

19. The method according to claim 1, which comprises forming the coil bundle by winding the wire on a core of an arbor, the arbor further comprising two opposing plates connected by the core, and, after the coil bundle has been formed, removing the coil bundle from the arbor, and wherein: the first windings form a plurality of layers arranged on top of one another in a radial direction of the coil bundle, wherein each layer comprises a plurality of adjacent windings arranged side by side in an axial direction of the coil bundle, and wherein the first windings only extend over a part of a length of the coil bundle in the axial direction of the coil bundle and only extend over a part of a width of the coil bundle in the radial direction of the coil bundle; the second windings form a plurality of layers arranged on top of one another in the radial direction of the coil bundle, wherein each layer comprises a plurality of adjacent windings arranged side by side in the axial direction of the coil bundle, and wherein the second windings only extend over a part of the length of the coil bundle in the axial direction of the coil bundle and only extend over a part of the width of the coil bundle in the radial direction of the coil bundle; the first windings form a region of an outer surface of the coil bundle, and/or wherein the second windings form a region of the outer surface of the coil bundle; and the first windings face the second windings in an axial direction of the coil bundle.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) FIG. 1 shows a way of winding a wire from a spool onto an arbor for forming a coil bundle;

(2) FIG. 2 shows a schematic view of a coil bundle wound on a bobbin of a coil according to the present invention;

(3) FIG. 3 shows the coil bundle and bobbin as shown in FIG. 2 arranged in a mold for embedding the coil bundle in an electrically insulating material;

(4) FIG. 4 shows a top view of the mold shown in FIG. 3 and of a coil bundle/bobbin arranged therein;

(5) FIG. 5 shows the coil bundle and bobbin embedded in said insulating material using the mold shown in FIG. 4;

(6) FIG. 6 shows the finished coil after removing of a portion of the insulating material and electrical insulation of the first and second windings of the coil bundle for forming electrical contacts of the coil;

(7) FIG. 7 shows the coil according to FIG. 6 with its electrical contacts soldered to a printed circuit board;

(8) FIG. 8 shows three different cross-sections of air-core coil bundles as well as a corresponding regions in which the electrical insulation of the respective coil bundle is to be ablated in order to electrically contact the coil bundle;

(9) FIG. 9 shows a cross section of a coil bundle in order to indicate difficulties occurring when ablating electrical insulation of wire sections, which ablation may cause an inter-layer short of the coil bundle thus rendering a significant number of windings useless concerning operation of the coil;

(10) FIG. 10 shows a cross section of a coil according to the present invention wherein first and second windings of the coil bundle are generated such that ablation of portions of electrical insulation of first and second windings can be conducted with a low risk of rendering a high number of windings useless concerning operation of the coil due to short circuits; and

(11) FIG. 11 shows a cross-section of another embodiment of a coil according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(12) Referring now once more to the figures of the drawing in detail and, particularly, to FIG. 2 thereof, there is shown a coil bundle 2 arranged on a bobbin 3 of a coil 1 according to the present invention. For manufacturing such a coil 1, a wire 10 that comprises an electrical insulation 11 is wound (here, e.g., on a bobbin 3) so as to form a coil bundle 2 comprised of successive windings 100.

(13) For winding of the coil bundle 2, the bobbin 3 can be placed on an arbor 4 that is rotated about a rotation axis z′ (e.g. similar to FIG. 1) to wind the wire 10 on the bobbin 3. After winding of the wire 10 onto the bobbin 3, the bobbin 3 can be removed from the arbor 4.

(14) The coil bundle 2 comprises at least one first winding 101 (here a plurality of first windings 101) formed by a first end section 10a of the wire 10 and at least one second winding 102 (here a plurality of second windings 102) formed by a second end section 10b of the wire 10. A portion 11a of the electrical insulation 11 of the first windings 101 is removed so as to expose a portion of the first end section 10a of the wire 10 for forming a first electrical contact 111 of the coil 1 (cf. FIG. 6). Likewise, a portion 11b of the electrical insulation 11 of the second windings 102 is removed so as to expose a portion of the second end section 10b of the wire 10 for forming a second electrical contact 112 of the coil 1 (cf. also FIG. 6). Ways of forming the electrical contacts 111, 112 will be described in more detail below.

(15) The first windings 101 are retained by four first recesses 30 that are formed into opposing circumferential edges 3a, 3b of the annular (e.g. tubular) wall member 3d, which forms bobbin 3. Particularly, two first recesses 30 are formed into the first edge 3a and two further first recesses 30 are formed into the second edge 3b so that the four recesses 30 are located on the corners of a virtual rectangle. The first end section 10a of the wire 30 is wound into these first recesses 30 so that several successive first windings 101 are generated that will later be used for forming a first electrical contact 111 of the coil 1. After winding of the first windings 101, a plurality of intermediary windings 103 is wound in a peripheral direction of the bobbin 3 onto the bobbin 3. These intermediary windings 103 surround the axis z of the annular wall member 3d/bobbin 3. After winding of these intermediary windings 103, a plurality of second windings 102 is generated. Also here, the second windings 102 are retained by four second recesses 31 that are formed into the two edges 3a, 3b of the wall member 3d. Particularly, again, two second recesses 31 are formed into the first edge 3a and two further second recesses 31 are formed into the second edge 3b so that the four second recesses 30 are located on the corners of a virtual rectangle. The second end section 10b of the wire 10 is now wound into these second recesses 31 so that several successive second windings 102 are generated that will later be used for forming a second electrical contact 112 of the coil 1.

(16) Further, the successive first windings 101 are wound about a winding axis w that particularly aligns with the winding axis w′ of the second windings 102, wherein both winding axes w, w′ particularly run perpendicular to said axis z of the annular wall member 3d, which axis z of the annular wall member 3d is the winding axis of those intermediary windings 103 that connect the first windings 101 to the second windings 102.

(17) Preferably, the coil bundle 2 comprising the bobbin 3, the first and second windings 101, 102 as well as the further connecting/intermediary windings 103 is overmolded with an electrically insulating material 7 (cf. FIG. 5) by placing the coil bundle 2 into the cavity 6a of a mold 6 as shown in FIGS. 3 and 4. The cavity 6a is then filled with the material 7 so as to form a coil bundle 2 embedded in the material 7, as shown in FIG. 5.

(18) In order to provide electrical contacts 111, 112 of the coil 11 connected to the first and second end section 10a, 10b of the wire 10, a portion 7a, 7b of said material 7 as well as an adjacent portion 11a, 11b of the electrical insulation 11 of the wire 10 is removed (e.g. by laser ablation or some other suitable technique) so as to expose a region 111 of the first end section 10a of the wire 10 (i.e. of the first windings 101) as well as a region 112 of the second end section 10b of the wire 10 (i.e., of the second windings 102), which regions 111, 112 form contacts 111, 112 for electrically contacting the windings of the coil bundle 2 (cf. FIG. 6).

(19) Particularly, electrically insulating material 11a, 11b, 7a, 7b is removed from a face side of the coil 1, so that said electrical contacts 111, 112 are arranged on a face side 1a of the coil 1 that extends perpendicular to the axis z of the bobbin 3/coil bundle 2.

(20) Particularly, said contacts 111, 112 may be coated (particularly plated) with an electrically conducting material, e.g. a soldering material (e.g. Sn), that may be used in a subsequent (e.g. automated) soldering process in which the coil 1 is soldered with its contacts 111, 112 to a printed circuit board 8 as shown in FIG. 7.

(21) The way in which the first and second windings 101, 102 are arranged with respect to the connecting further windings 103 of the coil 1 guaranties that the removal of insulating material/electrical insulation of the wire 10 at end sections 10a and 10b merely affects the first and second windings 101, 102 thus possible short-circuits upon contacting contacts 111 and 112 (e.g. by soldering or during ablation) are limited to the first and second windings and do not affect the successive windings 103 wound in the peripheral direction of the bobbin 3 which are responsible for achieving the desired electrical properties of the coil 1.

(22) Further embodiments of the present invention are shown in FIGS. 10 and 11.

(23) In this regard, FIG. 8 shows several generic cross sections of coil bundles 2 comprising windings 100 of a wire 10 and proposed window termination locations 11a, 11b, i.e. regions, where electrical insulation 11 of the wire 10 is to be removed in order to expose the wire 10 for forming two electrical contacts of the respective coil bundle 2 for electrically contacting the respective coil bundle 2.

(24) Due to the large variability in the inside and outside surface of the coil bundle, top and bottom respectively, it is apparent that wire sections from multiple layers of the coil bundle 2 could potentially be ablated and subsequently shorted to each other. When an inter-layer short develops; all the turns within their respective layers located between the two wires form a shorted loop and cease to contribute to the operation of the coil 2 as shown in FIG. 9. Additionally, this shorted loop can have a parasitic effect on the coil inductance further reducing its communication distance.

(25) Current winding processes have a margin of error that leads to inconsistencies in the exact position of wires within a layer. The result is that gaps are formed within the coil bundle 2 which allow wires to slip between layers. The use of insulation removal processes, such as laser ablation stripping, can also penetrate through these gaps and thereby reach inner layers in the coil. However, these inconsistencies typically do not expose wires more than two layers deep from either side with the infrequent third layer being exposed to possible ablation.

(26) Thus, by optimizing the way layers are placed during the winding process through the use of buffer turns, the impact of inter-layer shorting can be strongly mitigated. As shown in FIG. 10 such a coil 1 can be manufactured using a winding arbor 4 that consists of two plates 4a, 4b to guide the wire 10 and a core 4a that the wire 10 wraps around. During the winding process the arbor 4 spins around the cores axis z′ as a wire guide shifts between the two plates 4a, 4b laying the wire 10 in layers on the surface of the core 4a.

(27) Buffer turns, here denoted as first windings 101 and second windings 102, are used to create concentrated layers of wire 10 below desired window ablation locations by traversing a predefined portion of the winding arbor 4 at the start and end of the winding process rather than the arbor's 4 entire width.

(28) By containing the initial and final turns, i.e. the first windings 101 and the second windings 102, where the respective window/contact 111, 112 will be created, the total number of shorted turns generated by an inter-layer short can be drastically reduced.

(29) One exemplary buffer winding technique, shown in FIG. 10, is the so-called 2i-buffer coil.

(30) In this configuration the winder lays wire 10 through a set progression of steps 1, 2, 3, 4, and 5. By doing so, the first windings 101 (initial turns) and the second windings 102 (final turns) are concentrated in coplanar corners of the coil bundle 2. In other words, the second windings 102 encompass the first windings 101.

(31) Thus, an inter-layer short occurring within these corners, up to three layers deep, is contained to the size of the buffer. One advantage of the 2i buffer configuration is the use of steps 2 and 4 to preserve the geometry of the coil bundle 2. Here, after having formed the first windings 101 out of the first end section 10 of the wire 10, which first windings 101 only extend in the axial direction z of the coil bundle 2 over a part A of the length of the coil bundle 2 in the axial direction z, as well as merely over a part B of the width D of the coil bundle 2 in the radial direction R of the coil bundle 2, first intermediary windings 100a are laid down which fill up the neighboring space in the axial direction z, followed by second intermediary windings 100b formed in step 3 which extend over the entire axial length L of the coil bundle 2. Finally, after having formed third intermediary windings 100c in step 4, the concentrated second windings 102 are formed out of the second end section 10b of the wire 10 in step 5.

(32) The size of the respective buffer (first/second windings 101, 102) can be easily manipulated to accommodate the maximum error of the ablation technique.

(33) Furthermore, in the case that no inter-layer shorts are developed, the remaining insulated portion of the first and second windings 101, 102 remains a part of the functional coil 1.

(34) An alternate buffer winding technique is the T-buffer coil, shown in FIG. 11. This configuration shares the advantages of the 2i-buffer configuration, such as its protective layering, adaptable buffer size, and recycling of un-shorted buffer turns (first and second windings 101, 102) into the operational coil 1. This winding technique may use an arbor 4 with plates 4b, 4c connected by a core 4a that includes a recess 4d, here adjacent plate 4b.

(35) By laying the first windings 101 into this recess 4d this inside buffer section 101 can be made to protrude from the surface of the final coil bundle 2. Similarly, the final turns 102, i.e. the second windings 102, can be concentrated at the top of the coil bundle 2 at the opposite surface of the coil bundle 2 forming a similar proud buffer on the outside coil bundle face. An electrical contact 111 for contacting the first windings 101 can then be manufactured by removing a corresponding portion 11a of the electrical insulation of the first end section 10a of the wire 10 to expose a corresponding portion of the wire 10. Likewise a further electrical contact 112 for contacting the second windings 102 can then be manufactured by removing a corresponding portion 11b of the electrical insulation 11 of the second end section 10b of the wire 10 to expose a corresponding portion of the wire 10. By creating protruding buffer zones mechanical window generation techniques become more feasible (e.g. grinding or powder blasting).

(36) Embedding supplementary buffer turns, here first and second windings 101, 102 into coils 1 is both quick and inexpensive to implement through existing machinery. Furthermore, by mitigating the impact of inter-layer shorting rather than preventing its occurrence, the method according to the present invention promises strong reliability with flexible methods of application.

(37) It will be apparent to those skilled in the art that numerous modifications and variations of the described examples and embodiments are possible in light of the above teaching. The disclosed examples and embodiments are presented for purposes of illustration only. Other alternate embodiments may include some or all of the features disclosed herein. Therefore, it is the intent to cover all such modifications and alternate embodiments as may come within the true scope of this invention.