Membrane plate structure for generating sound waves

Abstract

The present invention relates to a membrane plate structure for generating sound waves, the membrane plate structure comprises a vibrating element for generating sound waves and a membrane plate which is coupleable to the vibrating element. The membrane plate has a different width with respect to its length, wherein the width is shorter than the length. The membrane plate comprises an UD layer made of fibers, wherein the fibers of the UD layer are oriented along the width of the membrane plate.

Claims

1. A membrane plate structure for generating sound waves, comprising: a vibrating element; a membrane plate coupled to the vibrating element for generating sound waves, wherein the membrane plate comprises a core layer, a first skin layer, and a second skin layer, and wherein the first skin layer and the second skin layer are located on opposing sides of the core layer; wherein the first skin layer and the second skin layer each comprise a single layer of a unidirectional fiber reinforced polymer, wherein a width of the membrane plate is shorter than a length of the membrane plate, and wherein the fibers of the unidirectional fiber reinforced polymer are oriented along a fiber direction having an angle between −30° and +30°, with respect to an axis extending across the width of the membrane plate; and wherein a thickness of the membrane plate is less than 500 μm.

2. The membrane plate structure of claim 1, wherein a fiber direction of the first skin layer is parallel to a fiber direction of the second skin layer.

3. The membrane plate structure of claim 1, wherein the core layer comprises a material which is free of pores larger than 1 μm, and wherein the core layer is structured adhere to the first skin layer and the second skin layer.

4. The membrane plate structure of claim 1, wherein the core layer comprises a foam.

5. The membrane plate structure of claim 1, wherein the core layer further comprises a unidirectional fiber tape, having a fiber direction perpendicular to the fiber direction of the skin layers.

6. The membrane plate structure according to claim 1, wherein a heat deflection temperature of the membrane plate is higher than 180° C.

7. The membrane plate structure of claim 1, wherein the membrane plate structure maintains its geometrical dimensions within 5%, up to 220° C.

8. The membrane plate structure of claim 1, wherein the membrane plate comprises an area density less than 160 g/m.sup.2.

9. The membrane plate structure of claim 1, wherein the unidirectional fiber reinforced polymer is non-conductive.

10. The membrane plate structure of claim 1, wherein the first skin layer and the second skin layer each comprise a unidirectional fiber reinforced polymer, and wherein the fiber reinforced polymer includes carbon based fibers.

11. The membrane plate structure of claim 1, wherein each of the first skin layer and the second skin layer have an area density less than 30 g/m.sup.2.

12. The membrane plate structure of claim 1, wherein the membrane plate forms a flat, uncurved shape extending along the plane.

13. The membrane plate structure of claim 1, wherein the first skin layer, the second skin layer, and the core layer form a stack having a curved extension.

14. The membrane plate structure of claim 1, wherein the membrane plate includes a thickness which is less than 1/20 of a width of the membrane plate.

15. The membrane plate structure of claim 1, wherein the vibrating element and the membrane plate at least partially define a micro speaker.

16. A membrane plate structure for generating sound waves, comprising: a vibrating element; a membrane plate operably coupled to the vibrating element, wherein the membrane plate comprises: a foam core layer sandwiched between a first skin layer and a second skin layer; wherein the first skin layer and the second skin layer each comprise a unidirectional fiber tape; wherein a thickness of the membrane plate is less than 500 μm; and wherein the membrane plate includes a width shorter than a length, wherein the first skin layer and the second skin layer further comprise a fiber reinforced polymer, and wherein a fiber direction of the first skin layer and the second skin layer are each oriented at an angle between −30° and +30° with respect to an axis extending across the width of the membrane plate.

17. The membrane plate structure of claim 16, wherein a fiber direction of the first skin layer is parallel to a fiber direction of the second skin layer, wherein the first skin layer and the second skin layer further comprise a fiber reinforced polymer.

18. The membrane plate structure of claim 17, wherein the core layer further comprises a foam.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The aspects defined above and further aspects of the present invention are apparent from the examples of embodiment to be described hereinafter and are explained with reference to the examples of embodiment. The invention will be described in more detail hereinafter with reference to examples of embodiment but to which the invention is not limited.

(2) FIG. 1 shows a schematic view of a loudspeaker comprising the membrane plate structure with aluminum as skin layer.

(3) FIG. 2 shows the coil and membrane plate of a loudspeaker comprising the membrane plate structure according to an exemplary embodiment of the present invention, wherein the fibers are oriented along the shorter (width) size of the plate.

(4) FIG. 3 shows the coil and membrane plate of a loudspeaker comprising the membrane plate structure according to an exemplary embodiment of the present invention, wherein the fibers UD skin layers are oriented along the shorter (width) size of the plate and the core layer is free of pores.

(5) FIG. 4 shows the coil and membrane plate of a loudspeaker comprising the membrane plate structure according to an exemplary embodiment of the present invention, wherein the fibers UD skin layers are oriented along the shorter (width) size of the plate and the core layer is porous.

(6) FIG. 5 shows a curved design of a membrane plate structure, according to an exemplary embodiment of the present invention.

(7) FIG. 6 shows the break-up modes simulations of the system membrane plate and coil.

(8) FIG. 7 shows a diagram illustrating sound pressure levels with respect to respective frequencies of three exemplary loudspeakers having different exemplary embodiments.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

(9) The illustrations in the drawings are schematic. It is noted that in different figures similar or identical elements are provided with the same reference signs.

(10) FIG. 1 shows a schematic view of a loudspeaker comprising a membrane plate structure. The membrane plate structure comprises a carrier element 104, a coil 105 which is coupled to the carrier element 104 and a membrane plate 100. The membrane plate 100 is supported by the carrier element 104 such that the membrane plate 100 is excitable by the coil 105 for generating sound waves.

(11) The membrane plate structure comprises a membrane plate 100 having a first skin layer 101, a second skin layer 102 and a core layer 103 which is interposed between the first skin layer 101 and the second skin layer 102.

(12) The coil 105 may be electrically excited by a control unit (not shown). The membrane plate 100 is coupled to the coil 105 such that the excited coil 105 excites the membrane plate 100 as well. The membrane plate 100 vibrates in an excited state and thereby generates acoustic sound.

(13) The first skin layer 101, the second skin layer 102 and the core layer 103 form a stack extending within a plane. In other words, the membrane plate 100 has a flat, uncurved shape extending along the plane. More specifically, the first skin layer 101, the second skin layer 102 and the core layer 103 extend along respective planes having parallel plane normals. In this specific example, the first skin layer 101 and the second skin layer 102 are made of aluminium.

(14) FIG. 2 shows an exemplary embodiment of the present invention, wherein the membrane plate structure comprises a vibrating element 105 and a membrane plate 100, which is coupleable to the vibrating element 105 for generating sound waves. The membrane plate 100 has a different width w with respect to its length, wherein the width w is shorter than the length. In particular, the width w is defined as the shortest distance between opposing edges of the membrane plate 100. The membrane plate 100 comprises an UD layer made of fibers 107, wherein the fibers of the UD layer 107 are oriented along the width w of the membrane plate 100 (indicated with fiber direction 106). The fibres may also be orientated along a further fiber direction 106′ which has an angle α with respect to the width direction w of the membrane plate 100. The angle α may be between −30° and +30°.

(15) The membrane plate 100 may consist of a matrix made of plastic or epoxy resin, in which fibers, in particular uni directional (UD) fibers 107 are integrated. UD fibres 107 extends along the fiber direction 106. The fiber direction 106 is parallel to a width w direction of the membrane plate 100. As can be taken from FIG. 2, the membrane plate 100 is formed rectangular, wherein the membrane plate 100 has a length and a with extension. The fibers 107 extends along the fiber direction 106 which is parallel to the width w direction of the membrane plate.

(16) Furthermore, it is shown in FIG. 2 that the coil 105 surrounds circumferentially the membrane plate 100. Hence, a proper control and excitation of the membrane plate 100 is possible.

(17) FIG. 3 shows a membrane structure according to an exemplary embodiment of the present invention, wherein the membrane plate 100 is formed in a sandwich design. The plate 100 comprises a first skin layer 107a and a second skin layer 107b, wherein a core layer 103 is interposed between both skin layers 101, 102. A young modulus of the core layer 103 may be lower than the young modulus of the first skin layer 101 and the second skin layer 102. The first skin layer 107a, the second skin layer 107b and/or the core layer 103 may be made of a fiber UD tape.

(18) FIG. 4 shows a further exemplary embodiment of the present invention, wherein the membrane plate 100 comprises a sandwich design according to the embodiment shown in FIG. 3. Furthermore, the core layer 103 is made of a foam material. The foam material may be a plastic material comprising pores filled with gas, such as air, wherein the pore size is for example 5 μm to 300 μm (Micrometer), in particular 10 μm to 200 μm, more in particular 30 μm to 150 μm.

(19) FIG. 5 shows an exemplary embodiment of a membrane plate structure wherein the membrane plate 100 is formed in a sandwich design. The plate 100 comprises a first skin layer 107a and a second skin layer 107b, wherein a core layer 103 is interposed between both skin layers 107a and 107b. In particular, the first skin layer 107a, the second skin layer 107b and the core layer 103 form a stack having a curved, in particular wavelike, extension. In other words, the membrane plate structure 100 comprises a curved, wavelike structure and runs not within a plane.

(20) FIG. 6 shows a simulation of a membrane plate 100 used in the simulation having a sandwich design with UD aramid fibers as skin layers 107a, 107b oriented along the longer (length) size of the membrane plate (S1) and oriented along the shorter size (width w) of the membrane plate (S2) according to the present invention. It is easy to understand that the first mode, i.e. the resonance frequency, in S1 is happening earlier than in S2, showing the beneficial effect of orienting the fibers along the shorter size of the membrane plate 100.

(21) FIG. 7 shows a diagram illustrating sound pressure levels (SPL) with respect to respective frequencies of three exemplary loudspeakers. In the shown example in FIG. 7, three materials for a standard 11 mm×15 mm (millimeter) micro-speaker have been used. All the materials have a total thickness of 220 μm (Micrometer) to properly compare the frequency response. Exemplary values for the exemplary materials are shown in Table 4 below:

(22) TABLE-US-00004 TABLE 4 Bending Area Frequency Thickness Modulus Density density Factor [μm] [Gpa] [kg/m.sup.3] [g/m.sup.2] [m.sup.2/s] CIMERA 220 24* 650 143 1.33* TDR220-30Y (UD Aramid skin layers) CIMERA 220 71* 510 112 2.61* CER220-20H (UD HM Carbon skin layers) CIMERA 220 18  620 135 1.21 AXR220-12H (Aluminum skin layers) *measured in fiber direction

(23) Line 703 is indicative for a conventional loudspeaker made of a CIMERA AXR220-12H (AXR) material, wherein the loudspeaker comprises a sandwich material with 12 μm (Micrometer) of aluminum skin layer.

(24) Line 701 is indicative for a loudspeaker according to the present invention made of CIMERA TDR220-30Y (TDR) material, wherein the loudspeaker comprises a sandwich material with 30 μm (Micrometer) aramid UD (Unidirectional) skin layers according to an exemplary embodiment of the present invention.

(25) Line 702 is indicative for a loudspeaker according to the present invention made of CIMERA CER220-20H (CER), wherein the loudspeaker comprises a sandwich material with 20 μm (Micrometer) HM (High Modulus) Carbon UD (Unidirectional) skin according to an exemplary embodiment of the present invention.

(26) A comparison of the mechanical properties of the three materials can be taken from table 4 above. As can be taken from the line 701, 702 presented in FIG. 7, TDR (CIMERA TDR220-30Y) in line 701 and AXR (CIMERA AXR220-12H) in line 703 presents very comparable mechanical and acoustic behavior, with the advantage that TDR is a non-conductive material. Instead, CER (CIMERA CER220-20H) in line 702 compared to AXR in line 703 is better performing in all the parameters with a higher break-up frequency and lower mass.

(27) It should be noted that the term “comprising” does not exclude other elements or steps and “a” or “an” does not exclude a plurality. Also elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims should not be construed as limiting the scope of the claims.

LIST OF REFERENCE SIGNS

(28) 100 membrane plate 101 first skin layer 102 second skin layer 103 core layer 104 carrier element, membrane or surround 105 coil/vibrating element 106 fiber direction 107 fibers/UD fiber reinforced tape layer(s) 107a (top) skin layers layer 107b (bottom) skin layers layer 701 representative line for TDR 702 representative line for CER 703 representative line for AXR w width α angle