Dual coil moving magnet transducer

Patent metadata

Field	Value
Publication number	US-9173035-B2
Application number	US-201314074491-A
Country	US
Kind code	B2
Filing date	Nov 7, 2013
Priority date	Nov 7, 2013
Publication date	Oct 27, 2015
Grant date	Oct 27, 2015

Abstract

Embodiments are disclosed for driving an electromagnetic transducer via a drive unit comprising stationary coils and a moving magnet. In some embodiments, an electromagnetic transducer comprises a diaphragm configured to generate acoustic vibrations, a moving magnet affixed to the diaphragm, and a pair of fixed coils surrounding the moving magnet, the fixed coils configured to direct electrical current in opposite directions.

First claim

The invention claimed is:

1. An electromagnetic transducer, comprising:
a diaphragm configured to generate acoustic vibrations;
a moving magnet affixed to the diaphragm;
a pair of fixed coils surrounding the moving magnet, the fixed coils configured to direct electrical current in opposite directions;
a magnetic sleeve directly coupled to at least a portion of the fixed coils via a coil-facing surface of the magnetic sleeve and to a housing of the electromagnetic transducer via another surface of the magnetic sleeve, the magnetic sleeve configured to generate a restoring force to magnet movement by providing a return path for magnetic flux lines of the magnet; and
a heat sink structure in thermal contact with the pair of fixed coils via the magnetic sleeve.

2. The electromagnetic transducer of claim 1 , wherein the magnetic sleeve concentrically surrounds the magnet.

3. The electromagnetic transducer of claim 1 , wherein the housing at least partially encloses the electromagnetic transducer, and
wherein the heat sink structure is affixed to a rear surface of the housing at a rear end of the electromagnetic transducer.

4. The electromagnetic transducer of claim 3 , wherein the heat sink structure comprises a plurality of fins configured to dissipate heat generated by magnet movement.

5. The electromagnetic transducer of claim 3 , wherein the fixed coils are wound in opposite directions.

6. The electromagnetic transducer of claim 1 , wherein the fixed coils are driven by respective amplifiers, the amplifiers in reverse phase with respect to each other.

7. The electromagnetic transducer of claim 1 , wherein the housing at least partially encloses the electromagnetic transducer, and the electromagnetic transducer further comprising
a linear bearing affixed to a rear end of the housing and extending along a central axis through a bore of the magnet, the magnet undergoing induced motion along the central axis via the linear bearing upon receiving electrical signals at the fixed coils.

8. The electromagnetic transducer of claim 1 , further comprising a front pole piece and a rear pole piece respectively disposed on a front surface and a rear surface of the magnet.

9. The electromagnetic transducer of claim 1 , wherein the diaphragm extends concavely inward below a front surface of a surround, the surround affixed to the diaphragm.

10. The electromagnetic transducer of claim 1 , wherein the diaphragm extends convexly outward above a front surface of a surround, the surround affixed to the diaphragm.

11. The electromagnetic transducer of claim 1 , further comprising a coupler affixed to the diaphragm and the magnet.

12. The electromagnetic transducer of claim 1 , wherein the housing at least partially encloses the electromagnetic transducer, the housing including a contiguous rear surface interrupted by a plurality of regularly-spaced hollow portions.

13. An electromagnetic transducer, comprising:
a surround affixed to a housing;
a diaphragm affixed to the surround, the diaphragm configured to produce acoustic vibrations;
a coupler affixed to the diaphragm;
a permanent magnet affixed to the coupler, the permanent magnet having a bore aligned to a central axis;
a coil comprising a first coil portion and a second coil portion, the first and second coil portions concentrically surrounding the permanent magnet and configured to induce motion in the permanent magnet about the central axis responsive by directing electrical signals in opposite directions;
a magnetic sleeve surrounding the permanent magnet, the magnetic sleeve being interposed between and in contact with the coil via a coil-facing surface of the magnetic sleeve and an inner portion of the housing via a surface of the magnetic sleeve opposite the coil-facing surface;
a heat sink structure affixed to a rear surface of the housing and in thermal contact with the coil via the magnetic sleeve; and
a linear bearing coupled to the magnet, the linear bearing constraining induced magnet motion to a central axis of the electromagnetic transducer.

14. The electromagnetic transducer of claim 13 , wherein the first coil portion and the second coil portion are maintained in a fixed position with respect to the housing.

15. The electromagnetic transducer of claim 1 , further comprising a coupler integrally formed with the diaphragm, the integrally-formed diaphragm and coupler comprised of one of injection-molded plastic and drawn aluminum.

16. The electromagnetic transducer of claim 13 , wherein the coupler, the permanent magnet, and the first and second coil portions are positioned such that motion induced in the permanent magnet and the diaphragm generates acoustic vibrations propagating toward a front surface of the surround, the surround affixed to the diaphragm.

17. The electromagnetic transducer of claim 13 , wherein the coupler, the permanent magnet, and the first and second coil portions are positioned such that motion induced in the permanent magnet and the diaphragm generates acoustic vibrations propagating away from a front surface of the surround, the surround affixed to the diaphragm.

18. The electromagnetic transducer of claim 13 , further comprising a plurality of ribs positioned on a surface of the diaphragm, the plurality of ribs extending radially outward from the coupler to a corrugation of the surround, the diaphragm affixed to the coupler at a first end and affixed to the surround at a second end.

19. A method for driving an electromagnetic transducer, comprising:
directing electrical signals through a pair of coils in opposite directions;
inducing motion in a permanent magnet via magnetic fields produced by the directed electrical signals and the permanent magnet, the induced motion constrained to a central axis via a linear bearing, the linear bearing affixed to a rear surface of a housing;
generating, with a magnetic sleeve directly coupled to the pair of coils and a housing of the electromagnetic transducer, a restoring force to magnet movement by providing a return path for magnetic flux lines of the permanent magnet;
maintaining the pair of coils in a fixed position;
generating acoustic vibrations by imparting the induced motion to a diaphragm coupled to the permanent magnet; and
transferring heat generated in the pair of coils to the housing via the magnetic sleeve and to a heat sink via the housing.

20. The method of claim 19 , further comprising:
dissipating heat generated by the induced permanent magnet motion and heat generated in the pair of coils via the heat sink structure, the heat sink structure being affixed to the rear surface of the housing.

Assignees

• Harman Int Ind

Inventors

• Button Douglas J

Classifications

• H04R9/02 Primary

  Details · CPC title

• H04R9/025

  Magnetic circuit · CPC title

• H04R9/022

  Cooling arrangements · CPC title

• H04R11/02 Primary

  Loudspeakers · CPC title

• H04R9/063

  using a plurality of acoustic drivers (H04R1/24 and H04R1/403 take precedence) · CPC title