Electrodynamic acoustic transducer with a high density coil and production method thereof
An electrodynamic acoustic transducer, is disclosed, which comprises a frame and/or a housing, a membrane, at least one coil and a magnet system. The coil in a cross sectional view with a coil axis being part of the sectional plane comprises a plurality of conductive layers formed by an electrical conductor of the coil. The electrical conductor has a rectangular cross section in said cross sectional view, wherein a longer side of the rectangular cross section is substantially perpendicular to the loop axis. Furthermore, a method for manufacturing an electrodynamic acoustic transducer of the proposed kind is disclosed. According to this method, a stack of conductive layers is made from the electrical conductor by stacking of separate pieces of the electrical conductor and electrically connecting the stacked separate pieces and/or by folding of the electrical conductor.
1. An electrodynamic acoustic transducer, comprising:
a frame and/or a housing;
a membrane fixed to said frame or said housing;
at least one coil, which is attached to the membrane, the at least one coil being in the shape of loops running around a coil axis, the at least one coil comprising:
a plurality of conductive layers, each formed of a single piece of metallic foil, and all stacked together, the plurality of conductive layers each having a rectangular cross section in a cross sectional view with the coil axis being part of the sectional plane, the plurality of conductive layers being electrically connected to each other so as to form a single electrical conductor; and
one or more insulation layers arranged between each of the plurality of conductive layers; and
a magnet system being designed to generate a magnetic field transverse to the at least one coil in the loop section,
wherein an angle between a longer side of the rectangular cross section of each of the plurality of conductive layers and the coil axis is in a range of 80° to 100°.
2. The electrodynamic acoustic transducer according to claim 1 , characterized in that the longer side of the rectangular cross section in said cross sectional view is arranged perpendicular to the coil axis.
3. The electrodynamic acoustic transducer according to claim 1 , characterized in that the ratio between the longer side of the rectangular cross section and the shorter side of the rectangular cross section is >4.
4. The electrodynamic acoustic transducer according to claim 1 , characterized in that the thickness of each conductive layer is between 10-30 μm, measured in a direction parallel with the coil axis.
5. The electrodynamic acoustic transducer according to claim 1 , characterized in that:
the lengths of the shorter side of the rectangular cross section of the plurality of conductive layers
varies along the coil axis.
6. The electrodynamic acoustic transducer according to claim 5 , characterized in that:
the shorter sides of the rectangular cross section of the plurality of conductive layers are longer in a center region of the at least one coil than in a distant region of the at least one coil.
7. The electrodynamic acoustic transducer according to claim 1 , characterized in that at least one of the plurality of conductive layers forms an electrical connection of the coil.
8. The electrodynamic acoustic transducer according to claim 7 , characterized in that the at least one conductive layer forming the electrical connection of the coil has a thickness, measured in a direction parallel with the coil axis, that is thicker than the thickness of an adjacent conductive layer.
9. The electrodynamic acoustic transducer according to claim 1 , characterized in that at least one of the plurality of conductive layers forms an electrical connection between the coil and a non-moving terminal of the electrodynamic acoustic transducer.
10. The electrodynamic acoustic transducer according to claim 9 , characterized in that the electrical connection between the coil and a non-moving terminal is coated with a polyamide.
11. The electrodynamic acoustic transducer according to claim 1 , characterized in that a share of all conductive layers on the volume of the coil is >80%.
12. An electrodynamic acoustic transducer, comprising:
a frame and/or a housing;
a membrane fixed to said frame or said housing;
at least one coil, which is attached to the membrane, the at least one coil being in the shape of loops running around a coil axis, the at least one coil comprising:
a plurality of conductive layers of metallic foil stacked together, the plurality of conductive layers each having a rectangular cross section in a cross sectional view with the coil axis being part of the sectional plane, the plurality of conductive layers being electrically connected to each other so as to form a single electrical conductor; and
one or more insulation layers arranged between each of the plurality of conductive layers; and
a magnet system being designed to generate a magnetic field transverse to the at least one coil in the loop section,
characterized in that at least two adjoining conductive layers or loops are formed by a single piece of a metallic foil, which comprises a folding between each two conductive layers, wherein the folding is arranged in a protrusion of the coil.
13. The electrodynamic acoustic transducer according to claim 12 , characterized in that the electrical conductor in the region of the protrusion runs out of the plane of the conductive layer at least by the thickness, measured in a direction parallel with the coil axis, of the conductive layer in a section from a protrusion start to a folding line, and along a 180° bending around the folding line back into the plane of the conductive layer.
14. An electrodynamic acoustic transducer, comprising:
a frame and/or a housing;
a membrane fixed to said frame or said housing;
at least one coil, which is attached to the membrane, the at least one coil being in the shape of loops running around a coil axis, the at least one coil comprising:
a plurality of conductive layers of metallic foil stacked together, the plurality of conductive layers each having a rectangular cross section in a cross sectional view with the coil axis being part of the sectional plane, the plurality of conductive layers being electrically connected to each other so as to form a single electrical conductor; and
one or more insulation layers arranged between each of the plurality of conductive layers; and
a magnet system being designed to generate a magnetic field transverse to the at least one coil in the loop section,
characterized in that at least two adjoining conductive layers or loops are formed by a single piece of a metallic foil, which comprises a folding between each two conductive layers, and wherein:
the longer side of the rectangular cross section is enlarged in the region of the folding in relation to a section of the at least two conductive layers outside of said folding; and/or
the at least two conductive layers are made up from aluminum and are hardened and annealed in the region of the folding.
15. The electrodynamic acoustic transducer according to claim 1 , characterized in that the thickness, measured in a direction parallel with the coil axis, of each insulation layer is between 1-5 μm.
16. The electrodynamic acoustic transducer according to claim 1 , wherein the lengths of the longer side of the rectangular cross section of the plurality of conductive layers varies along the coil axis.
17. The electrodynamic acoustic transducer according to claim 16 , wherein the longer sides of the rectangular cross section of the plurality of conductive layers are shorter in a center region of the at least one coil than in a distant region of the at least one coil.
18. The electrodynamic acoustic transducer according to claim 1 ,
wherein the lengths of the shorter side of the rectangular cross section of the plurality of conductive layers varies along the coil axis, and
the lengths of the longer side of the rectangular cross section of the plurality of conductive layers varies along the coil axis.
19. The electrodynamic acoustic transducer according to claim 18 ,
wherein the shorter sides of the rectangular cross section of the plurality of conductive layers are longer in a center region of the at least one coil than in a distant region of the at least one coil, and
the longer sides of the rectangular cross section of the plurality of conductive layers are shorter in a center region of the at least one coil than in a distant region of the at least one coil.