COIL

Abstract

Coil, preferably for driving a loudspeaker, comprising a printed circuit board and at least two windings formed as conductors, wherein the conductors have different widths.

Claims

1. A coil, comprising a printed circuit board (10), and at least two windings formed as conductors (30), wherein the conductors (30) have different widths.

2. Coil according to claim 1, characterized in that the widths of the conductors (30) are selected in such a way that the force factor of the coil is linearised in a magnetic field.

3. Coil according to claim 1, characterized in that a plurality of conductors (30) is provided, whereby the widths of the conductors vary unevenly from a coil centre (32) outwardly.

4. Coil according to claim 3, characterized in that the widths of the conductors (30) are smaller at an inner region than at a central region, the inner region being arranged closer to the coil centre (32) than the central region.

5. Coil according to claim 3, characterized in that the widths of the conductors (30) are smaller at an outer region than at a central region, the central region being arranged closer to the coil centre (32) than the outer region.

6. Coil according to claim 1, characterized in that several layers of printed circuit boards (30) are provided.

7. Coil according to claim 1, characterized in in that the widths of the conductors (30) are selected in such a way that, in a magnetic field, a range of the deflection of the coil in which the quotient of a force factor and a force factor at a zero deflection deviates from the value 1 at most by a predetermined relative deviation is greater than in the case of a coil with constant widths of the conductors.

8. Use of a coil according to claim 1 for a loudspeaker.

9. Procedure of producing a coil according to claim 1, in which at least two windings of different widths in the form of conductors (30) are applied to a printed circuit board (10).

10. Procedure according to claim 9, characterized in that a computer-aided optimisation method is used to calculate the widths of the conductors (30).

11. Coil according to claim 1, characterized in that the coil is designed for driving a loudspeaker.

12. Use of a coil according to claim 1 for a planar loudspeaker.

13. Procedure according to claim 10, characterized in that the widths are optimised by linearizing a force factor of the coil in a magnetic field.

Description

[0075] The invention is described below by way of example with reference to the drawings. The following is shown:

[0076] FIG. 1 a perspective view of one design of a coil in a magnet device according to the invention,

[0077] FIG. 2 a sectional view of the design according to FIG. 1,

[0078] FIG. 3 a top view of a design of a coil according to the invention,

[0079] FIG. 4 a sectional view of a design of a coil according to the invention,

[0080] FIG. 5 a diagram showing the normalised integral of the current density over the width and depth,

[0081] FIG. 6 a diagram showing the force factor.

[0082] First of all, it should be noted that the designs shown are of a purely exemplary nature. Individual features can be realised not only in the combination shown, but also in a stand-alone position or in other technically sensible combinations. For example, the features of one design can be combined as desired with features of another design.

[0083] If a figure contains a reference sign that is not explained in the directly associated descriptive text, reference is made to the corresponding previous and/or subsequent explanations in the figure description. Thus, the same reference signs are used for identical and/or comparable components in the figures and these are not explained again.

[0084] FIG. 1 shows a coil with a printed circuit board 10, which is arranged in a gap between two magnet units 12, 14 of a magnet device 16.

[0085] Each magnet unit 12, 14 comprises a magnet 18, 20, e.g. bar magnets, and two pole pieces 22, 24, 26, 28, e.g. steel bars. For example, the magnets 18, 20 may comprise a neodymium alloy.

[0086] The coil together with the magnet device 16 forms a drive unit, for example for driving the sound panel of a loudspeaker.

[0087] When electricity flows through the coil, it is deflected in the magnetic field due to the Lorentz force. In this way, for example, a sound panel can be set in vibration.

[0088] FIG. 2 shows a corresponding sectional view in which the magnetic flow lines are drawn.

[0089] The magnets 18, 20 are aligned in such a way that circular magnetic flow lines result. The magnetic field strengths add up.

[0090] The pole pieces 22, 24, 26, 28 are arranged in such a way that the magnetic flow lines are concentrated in the gap in which the coil is located. The coil is only made of two parts for illustrative purposes. In fact, it is one-piece.

[0091] FIG. 3 shows a coil with a printed circuit board 10 and a large number of conductors 30.

[0092] Conductors 30, which are located in an inner area near the coil centre 32, have a smaller width than conductors 30, which are located in a central area.

[0093] The central area is followed from the inside to the outside by an outer area in which the conductors 30 again have a smaller width than the conductors 30 in the central area.

[0094] The conductors 30 can be V-shaped at lateral deflection areas 34, for example. The two legs can enclose an angle of 120°, for example. The corner areas can preferably be rounded to create a smooth transition.

[0095] The outer end of the conductors 30 may be connected to an amplifier. An applied electric current thus flows from the outside to the inside. The inner end of the conductors 30 can in turn lead to another layer. Preferably, several layers of coils are provided.

[0096] FIG. 4 shows a cross-section of an arrangement with several layers. The different colours represent the different directions of current.

[0097] The layers can be connected in parallel or in series. In particular, the conductors 30 of a layer are connected in series.

[0098] The widths of the conductors 30 can be different in the layers, at least partially.

[0099] FIG. 5 shows the integral of the current density over the width and depth for a coil with an optimised current density OS. The z-axis represents the height z of the coil in mm, while the s-axis corresponds to the normalised electric current

[00003]$\frac{{\int }_{x,y}.Math.\stackrel{.fwdarw.}{J}\left(z\right).Math.\mathrm{dxdy}}{\max \left({\int }_{x,y}.Math.\stackrel{.fwdarw.}{J}\left(z\right).Math.\mathrm{dxdy}\right)}.$

[0100] The centre of the coil was chosen as the origin of the Cartesian coordinate system. This is also the point of symmetry of the system.

[0101] The integral of the current density over the width and depth is the sum of the currents per height of all conductor cross-sections.

[0102] This is calculated from the integral of the current density over the x and y dimensions.

[0103] Only the z-axis can be considered here, as the magnetic flow density changes only minimally across the width of the coil and/or printed circuit board. Furthermore, the conductors are predominantly aligned perpendicular to the magnetic flow density over the depth. Compared to the corner areas, the conductors are very long, so that the corner areas can be neglected. There are therefore no changes over the length.

[0104] For positive values of the normalised current density, the result is approximately a U-shape. Accordingly, for negative values of the normalised current density, the result is approximately an inverted U-shape.

[0105] For comparison, the integral of the current density over the width and depth is shown for a coil with a constant current density KS, whereby the current density between the individual conductors is neglected.

[0106] In FIG. 6 the normalised force factor

[00004]$\frac{\mathrm{Bl}}{\mathrm{Bl}\left(D=0\right)}$

is plotted along the k-axis against the coil deflection D in mm.

[0107] In a coil with an optimised current density OS, the normalised force factor is almost constant at 1 over a wide range, which is a significant improvement compared to a coil with a constant current density KS.

[0108] The range in the z-direction, in which the deviation is only a maximum of 10%, can extend from −5 mm to 5 mm, for example, in a coil with optimised current density OS according to the invention. In a conventional coil with constant current density KS, the corresponding range can be significantly smaller and extend, for example, only from −3 mm to 3 mm.

LIST OF REFERENCE SIGNS

[0109] 10 printed circuit board [0110] 12, 14 magnet unit [0111] 16 magnet device [0112] 18, 20 magnet [0113] 22, 24, 26, 28 pole piece [0114] 30 conductor [0115] 32 coil centre [0116] 34 deflection area [0117] OS optimised current density [0118] KS constant current density [0119] z z-axis [0120] s s-axis [0121] k k-axis [0122] D coil deflection