Loudspeaker with improved thermal load capacity

Abstract

The present invention relates to a loudspeaker (1; 1; 1) with a loudspeaker housing (2; 2), a basket (3) held in the loudspeaker housing (2; 2) and bearing a permanent magnet (9), a coil (91) arranged in a constant magnetic field generated by the permanent magnet (9) and connected with a diaphragm (5), and at least one heat pipe (10) with a heating zone (Z1) and cooling zone (Z3), wherein the heating zone (Z1) is arranged on the permanent magnet (9), and the cooling zone (Z3) on the loudspeaker housing (2; 2). The present invention further relates to the use of such a loudspeaker for actively extinguishing or influencing sound waves, and a noise control system (100) for exhaust systems of a vehicle powered by an internal combustion engine with such a loudspeaker (1; 1, 1).

Claims

1. A loudspeaker comprising: a loudspeaker housing; a basket held in the loudspeaker housing and bearing a permanent magnet; a coil arranged in a constant magnetic field generated by the permanent magnet and connected with a diaphragm; and at least one heat pipe with a heating zone and cooling zone wherein the heating zone is arranged on the permanent magnet, and the cooling zone is arranged on the loudspeaker housing; wherein the at least one heat pipe is permanently and rigidly connected to the permanent magnet; and wherein the at least one heat pipe is displaceably connected with the loudspeaker housing at the cooling zone.

2. The loudspeaker according to claim 1, wherein the at least one heat pipe comprises: a tubular, hermetically sealed volume enclosed by a wall; capillaries accommodated inside the volume; and a working medium accommodated inside the volume, which fills the volume in smaller part in liquid state, and in larger part in gaseous state.

3. The loudspeaker according to claim 2, wherein the wall of the at least one heat pipe is made out of metal.

4. The loudspeaker according to claim 2, wherein the capillaries of the at least one heat pipe take the form of at least one of plastic tubules and metal tubules and a fabric and a braiding.

5. The loudspeaker according to claim 2, wherein the working medium accommodated inside the volume of the at least one heat pipe is selected from (CH.sub.3)OH, (CH.sub.3)CO, NH.sub.3, H.sub.2O and C.sub.6H.sub.6.

6. The loudspeaker according to claim 1, wherein the exterior side of the loudspeaker housing comprises cooling ribs in the area where the at least one heat pipe is arranged.

7. The loudspeaker according to claim 1, wherein at least one of the cooling zone and the heating zone of the at least one heat pipe comprises a block consisting of a material whose thermal conductivity is at least 100 W/(m*K); and the cooling zone respectively heating zone of the at least one heat pipe is arranged on the permanent magnet respectively loudspeaker housing indirectly by way of the block.

8. The loudspeaker according to claim 1, wherein the loudspeaker housing is made out of plastic, and the area of the loudspeaker housing where the cooling zone of the at least one heat pipe is located, comprises a sealed or injected body with a thermal conductivity measuring at least 100 W/(m*K).

9. The loudspeaker according to claim 1, wherein the permanent magnet has at least one borehole, in which the heating zone of the at least one heat pipe is arranged, wherein the coil surrounds the borehole at least in sections.

10. The loudspeaker according to claim 1, wherein the loudspeaker is sealed against outside influences.

11. A loudspeaker comprising: a loudspeaker housing; a basket held in the loudspeaker housing and bearing a permanent magnet; a coil arranged in a constant magnetic field generated by the permanent magnet and connected with a diaphragm; and at least one heat pipe with a heating zone and cooling zone, wherein the heating zone is arranged on the permanent magnet, and the cooling zone on the loudspeaker housing; wherein the loudspeaker housing is made out of plastic, and the area of the loudspeaker housing where the cooling zone of the at least one heat pipe is located, comprises a sealed or injected body with a thermal conductivity measuring at least 100 W/(m*K); wherein the loudspeaker is sealed against outside influences; and wherein the exterior side of the loudspeaker housing comprises cooling ribs in the area where the at least one heat pipe is arranged.

12. The loudspeaker according to claim 11, wherein the heat pipe comprises: a tubular, hermetically sealed volume enclosed by a wall made out of metal; capillaries accommodated inside the volume, wherein the capillaries take the form of at least one of plastic tubules and metal tubules and a fabric and a braiding; and a working medium accommodated inside the volume, which fills the volume in smaller part in liquid state, and in larger part in gaseous state, wherein the working medium accommodated inside the volume of the at least one heat pipe is selected from (CH.sub.3)OH, (CH.sub.3)CO, NH.sub.3, H.sub.2O and C.sub.6H.sub.6.

13. The loudspeaker according to claim 11, wherein the at least one heat pipe is permanently and rigidly connected to the permanent magnet.

14. The loudspeaker according to claim 13, wherein the at least one heat pipe is detachably or displaceably connected with the loudspeaker housing at its cooling zone.

15. The loudspeaker according to claim 14, wherein at least one of the cooling zone and heating zone of the at least one heat pipe comprises a block consisting of a material whose thermal conductivity is at least 100 W/(m*K); and the cooling zone respectively heating zone of the at least one heat pipe is arranged on the permanent magnet respectively loudspeaker housing indirectly by way of the block.

16. The loudspeaker according to claim 14, wherein the permanent magnet has at least one borehole, in which the heating zone of the at least one heat pipe is arranged, wherein the coil surrounds the borehole at least in sections.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The foregoing as well as other advantageous features of the disclosure will be more apparent from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Not all possible embodiments may necessarily contain each and every, or any, of the advantages identified herein. It is noted that the invention is not limited to the examples in the described exemplary embodiments, but is rather defined by the scope of the attached claims. The following description of exemplary embodiments of the invention refers to the attached figures, in which

(2) FIG. 1A is a schematic cross sectional view of a loudspeaker according to a first embodiment;

(3) FIG. 1B is a view of the heat pipe according to the first embodiment from FIG. 1A along viewing direction B;

(4) FIG. 1C is a schematic cross sectional view through a heat pipe of the first embodiment from FIG. 1A;

(5) FIG. 2 is a schematic cross sectional view of a loudspeaker according to a second embodiment;

(6) FIG. 3 is a schematic cross sectional view of a loudspeaker according to a third embodiment;

(7) FIG. 4 is a schematic view of components of an active noise control system for exhaust systems of a vehicle powered by an internal combustion engine; and

(8) FIG. 5 is a block diagram of the active noise control system from FIG. 4.

(9) In the exemplary embodiments described below, components that are alike in function and structure are designated as far as possible by alike reference numerals. Therefore, to understand the features of the individual components of a specific embodiment, the descriptions of other embodiments and of the summary of the disclosure should be referred to.

(10) In the following, reference is made to FIGS. 1A, 1B and 1C in describing a loudspeaker according to a first embodiment of the present invention.

(11) The loudspeaker marked overall with reference number 1 comprises a loudspeaker housing 2 made out of plastic, which can be joined by connecting flanges 21 with ducts 101 of an exhaust system of an active noise control system 100. The loudspeaker housing 2 holds a sheet metal basket 3, which carries a permanent magnet 9. The basket 3 has the overall shape of a truncated cone. The basket 3 carries a plastic diaphragm 5a via a surround 4 made from flexible plastic. The diaphragm 5 has the overall shape of a truncated cone. A dust cap 6 and bobbin 7 are secured to the top surface of the truncated cone formed by the diaphragm 5. The end of the bobbin 7 averted from the diaphragm 5 is arranged in an annular gap 91 provided in the permanent magnet 9, and carries a voice coil 71. As a result, this coil 17 is located in a constant magnetic field generated by the permanent magnet 9. It is noted that the width of the annular gap 91 on the figure is greatly exaggerated. The bobbin 7 is centred relative to the annular gap 91 by means of a centring spider 8. The centring spider 8 consists of springs radially stretched between the bobbin 7 and basket 3. In the embodiment shown, the basket 3, surround 4, diaphragm 5, dust cap 6, bobbin 7 and permanent magnet 9 are rotationally symmetrical bodies with the same axis of symmetry.

(12) Three heat pipes 10 each having a heating zone Z1 and cooling zone Z3 are arranged on the permanent magnet 9 on the side averted from the basket 3. The heating zones Z1 of the heat pipes 10 are embedded in a massive aluminium block 11. The aluminium block 11 is adhesively bonded face to face and thus over its whole surface facing the permanent magnet 9 with the permanent magnet 9. The cooling zones Z3 of the heat pipes 10 are guided in grooves, which are provided in another massive aluminium block 12. The aluminium block 12 penetrates the wall of the loudspeaker housing 2, and its side averted from the heat pipes 10 contains cooling ribs. This is shown best in FIG. 1B, which depicts the heat pipes 10 along the viewing direction B on FIG. 1A.

(13) As is evident from FIG. 1A, the cooling ribs of the aluminium block 12 are exposed to air L guided via an air duct.

(14) The function and exact structure of the heat pipes 10 of FIGS. 1A and 1B will be described below by referring to FIG. 1C. FIG. 1C shows a schematic cross sectional view through one heat pipe 10 from FIG. 1A, wherein the heat pipe 10 is not yet bent, but rather extends along a straight line.

(15) The overall cylindrical heat pipe 10 has a wall 13 made out of metal, which provides for a tubular, hermetically sealed volume inside the heat pipe. The wall 13 is lined with a layer of metal braiding 14 on the inside of the heat pipe, which metal braiding 14 provides capillaries. The metal braiding 14 is saturated with a working medium, in this case (CH.sub.3)OH. The remaining inner volume of the heat pipe is filled partially with evaporated (CH.sub.3)OH and partially with argon, wherein the argon serves only to set the pressure inside the heat pipe 10, and hence the boiling point of the (CH.sub.3)OH.

(16) If energy in the form of heat is supplied to the wall 13 of the heat pipe 10 in a heating zone Z1, the (CH.sub.3)OH located in the metal braiding 14 evaporates into the free interior volume of the heat pipe 10. At the same time, the capillary force causes liquid (CH.sub.3)OH to be fed to the metal braiding 14 located in the heating zone Z1. If energy in the form of heat is simultaneously removed from the wall 13 of the heat pipe 10 in a cooling zone Z3, the gaseous (CH.sub.3)OH again condenses, and saturates the metal braiding 14 located in the cooling zone Z3. At the same time, new, gaseous (CH.sub.3)OH flows into the area of the cooling zone Z3. The flow of liquid (CH.sub.3)OH is denoted on the figure by arrows 15, while the flow of gaseous (CH.sub.3)OH is denoted on the figure by arrows 16. The heating zone Z1 is also referred to as an evaporation zone, and the cooling zone Z3 is also referred to as a condensation zone. The area Z2 between heating zone Z1 and cooling zone Z3 is also known as adiabatic transport zone.

(17) An advantage of arranging the cooling zone Z3 above the heating zone Z1 of the heat pipe 10 as shown in the first embodiment is that the return flow of working medium in the heat pipe 10 is assisted by gravity. For this reason, usage of a metal braiding that provides capillaries is only optional.

(18) A second embodiment of the loudspeaker 1 according to the invention will be described below, drawing reference to FIG. 2. Since this embodiment is very similar to the first embodiment described above, the following will focus only on differences, with reference otherwise being made to the aforesaid.

(19) The second embodiment differs from the first embodiment described above in that the cooling zone Z3 of the heat pipe 10 is located below the heating zone Z1. As a consequence, transporting back the working medium provided in the heat pipe 10 absolutely requires that corresponding capillaries be arranged in the heat pipe 10. In this second embodiment, the working medium is NH.sub.3, and the capillaries are provided by plastic tubules located in the heat pipe 10.

(20) The second embodiment shown on FIG. 2 further differs from the first embodiment described above in that the material 12 that accommodates the cooling zone Z3 of the heat pipe and forms the cooling ribs on the exterior side of the loudspeaker housing 2 is identical to the material forming the loudspeaker housing 2. As opposed to the first embodiment described above, the heat pipes 10 in this embodiment are fixedly joined with the loudspeaker housing 2 in the cooling zone Z3, and in the heating zone Z1 are guided in grooves provided in a copper block adhesively bonded with the permanent magnet 9. A thermal conductance paste is also provided in the grooves to support thermal conduction.

(21) While an annular gap is also arranged in the permanent magnet 9 and the bobbin 7 also carries a voice coil 17 situated in the annular gap in the embodiment on FIG. 2, the annular gap and coil are not shown, other than in FIG. 1A.

(22) A third embodiment of the loudspeaker 1 according to the invention will be described below, drawing reference to FIG. 3. Since this embodiment is very similar to the first and second embodiments described above, the following will focus only on differences, with reference otherwise being made to the aforesaid.

(23) The third embodiment shown on FIG. 3 differs from the first and second embodiments described above in that only two heat pipes 10 are provided, which are directly held in boreholes in the area of their heating zones Z1, which boreholes are provided in the permanent magnet 9 inside of the annular gap 91 accommodating the coil 71. As a consequence, the heat is transferred from the permanent magnet 9 to the heat pipe 10 directly. In the area of their cooling zone Z3, the heat pipes 10 penetrate through the loudspeaker housing 2, and in so doing themselves directly form cooling elements, which are arranged on the exterior side of the loudspeaker housing 2.

(24) Finally, reference is made to FIGS. 4 and 5 in describing the use of a loudspeaker according to the invention for actively extinguishing or influencing sound waves in an active noise control system for exhaust systems of a vehicle powered by an internal combustion engine.

(25) Since the loudspeaker has the structure described in the first embodiment except for a deviating shape for the loudspeaker housing 2, the following will focus only on the special features of the active noise control system.

(26) The active noise control system 100 comprises an antinoise controller 102, which in order to exchange control or measuring signals is electrically connected with the engine controller of an internal combustion engine 103 with an error microphone 104 situated in a duct 101 of an exhaust system of the active noise control system 100, as well as with the loudspeaker 1. As a function of an operating state of the internal combustion engine 103 acquired by the engine controller of the internal combustion engine 103, the antinoise controller 102 calculates control signals, which are fed to the loudspeaker 1 so as to generate antinoise, which extinguishes airborne noise guided in the duct 101 at least partially. The control signal can be further regulated by using signals output by the error microphone 104, so that airborne noise is emitted at a reduced sound pressure at the tailpipe 105 of the exhaust system. The loudspeaker 1 is mounted in the underbody of a motor vehicle in such a way as to be additionally cooled by an airstream as shown in FIG. 1A.

(27) It is be emphasized that the exemplary embodiments described above are only examples, and not intended to limit the scope of protection provided by the claims.