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

1-33. (canceled)

24. Membrane plate structure for generating sound waves, the membrane plate structure comprising a vibrating element a membrane plate which is coupleable to the vibrating element for generating sound waves, wherein the membrane plate comprises at least one UD layer made of fibers.

25. Membrane plate structure according to claim 24, wherein the membrane plate has a different width with respect to its length, wherein the width is shorter than the length, and wherein the fibers of the UD layer are oriented along a fiber direction having an angle between 30 and +30, in particular between 15 and +15, with respect to the width of the membrane plate.

26. Membrane plate structure according to claim 24, wherein the membrane plate is constituted by a stack of at least three layers, wherein a core layer is sandwiched by opposing two skin layers, where the skin layers are parallel unidirectional fiber reinforced plastic layers attached to the core layer, where the stack constitutes a sandwich construction.

27. Membrane plate structure according to claim 26, where the core layer of the sandwich structure is a material which is free of pores, in particular of pores having a size more than 1 m, and act as binding elements between the two skin layers.

28. Membrane plate structure according to claim 26, where the core layer of the sandwich structure is a porous material like a foam or a honeycomb.

29. Membrane plate structure according to claim 26, where the core layer is a fiber UD tape perpendicular to the direction of the fiber UD tapes of the skin layers.

30. Membrane plate structure according to claim 24, wherein the membrane plate is made of a fiber reinforced plastic, wherein the matrix material is made of in particular a thermoplastic plastic, a thermoset plastic or an elastomer plastic.

31. Membrane plate structure according to claim 24, wherein the heat deflection temperature is higher than 80 C., in particular higher than 130 C., further in particular higher than 180 C.

32. Membrane plate structure according to claim 24, wherein the membrane plate structure maintains its geometrical dimensions (change in size lower than 5%) under temperatures higher than 130 C., higher than 180 C. and higher than 220 C.

33. Membrane plate structure according to claim 24, characterized by having an area density lower than 200 g/m2, preferable lower than 160 g/m.sup.2, further in particular lower than 120 g/m.sup.2, and characterized by having a total thickness lower than in particular 500 m.

34. Membrane plate structure according to claim 24, where the fiber UD tape material is constituted by materials which are non-conductive.

35. Membrane plate structure according to claim 24, where the fiber UD tape material is constituted by carbon based fibers.

36. Membrane plate structure according to claim 24, where the UD fiber skin layer of the sandwich construction are characterized by an area density lower than 50 g/m.sup.2, better lower than 40 g/m.sup.2, at best lower than 30 g/m.sup.2 for each skin layer.

37. Membrane plate structure according to claim 24, wherein the structure forms a flat, uncurved shape extending along the plane.

38. Membrane plate structure according to claim 24, wherein the structure forms a stack having a curved extension.

39. Membrane plate structure according to claim 24, wherein the structure form has a total depth of less than , in particular 1/10, further in particular 1/20, of a largest width of the stack.

40. A micro speaker comprising a membrane plate of claim 24.

41. The micro speaker of claim 24 having a rectangular geometry.

42. Method of producing a membrane plate structure according to claim 24.

43. Method of claim 42, wherein the first skin layer, the second skin layer and the core layer are joined through an ambient temperature lamination step wherein the first skin layer and the second skin layer and the core layer, are in particular joined through a warm lamination step, and wherein the membrane plate structure is in particular made of a composite material produced by depositing a resin as core layer on the first skin layer, covering the resin with the second skin layer and curing the resin.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0056] 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.

[0057] FIG. 1 shows a schematic view of a loudspeaker comprising the membrane plate structure with aluminum as skin layer.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] FIG. 5 shows a curved design of a membrane plate structure, according to an exemplary embodiment of the present invention.

[0062] FIG. 6 shows the break-up modes simulations of the system membrane plate and coil.

[0063] 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

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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 with respect to the width direction w of the membrane plate 100. The angle may be between 30 and +300.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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 m to 300 m (Micrometer), in particular 10 m to 200 m, more in particular 30 m to 150 m.

[0074] 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.

[0075] 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.

[0076] 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 mm15 mm (millimeter) micro-speaker have been used. All the materials have a total thickness of 220 m (Micrometer) to properly compare the frequency response. Exemplary values for the exemplary materials are shown in Table 4 below:

TABLE-US-00004 TABLE 4 Bending Area Frequency Thickness Modulus Density density Factor [m] [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

[0077] 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 m (Micrometer) of aluminum skin layer.

[0078] 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 m (Micrometer) aramid UD (Unidirectional) skin layers according to an exemplary embodiment of the present invention.

[0079] 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 m (Micrometer) HM (High Modulus) Carbon UD (Unidirectional) skin according to an exemplary embodiment of the present invention.

[0080] 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.

[0081] 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

[0082] 100 membrane plate [0083] 101 first skin layer [0084] 102 second skin layer [0085] 103 core layer [0086] 104 carrier element, membrane or surround [0087] 105 coil/vibrating element [0088] 106 fiber direction [0089] 107 fibers/UD fiber reinforced tape layer(s) [0090] 107a (top) skin layers layer [0091] 107b (bottom) skin layers layer [0092] 701 representative line for TDR [0093] 702 representative line for CER [0094] 703 representative line for AXR [0095] w width [0096] angle