Patent Application
20150312660
a. Technical Field
The present invention generally relates to acoustic transducers, including membranes for acoustic transducers.
b. Background Art
Acoustic membranes (i.e., membranes for electro-acoustic transducers, including speakers and microphones) may be designed and manufactured to optimize numerous characteristics. First, membranes should meet chosen acoustic criteria to ensure acceptable sound reproduction over a desired frequency range. Second, membranes should function well over a range of temperatures, as the membrane and its environment may rise in temperature as a result of transducer operation. Third, membranes should have acceptable fatigue behavior (e.g., acceptable level of reduction in the sound reproduction capabilities of the membrane over time) to enable a long lifetime of the transducer.
Acoustic membranes with more than one layer have been used in the past. Such membranes generally have a symmetric layer arrangement to enable equal movement and stiffness of the membrane in both directions of excursion of the membrane. For example, one known arrangement using a five-layer arrangement, where the outside layers are made from the same thermoplastic material, and an inner most layer serves as a carrier layer, with layers of an adhesive between the inner carrier layer and the outer layers. With five different layers, the costs and production time of such membranes can be high. Another example of a known arrangement includes a central layer of acrylate material as an adhesive with layers of the same thermoplastic material on both sides of the central layer. To ensure good acoustic performance, a high quality thermoplastic material is used for the outside layers. There is a need, however, for a multi-layer compound acoustic membrane that achieves similar or better acoustic performance as existing examples at a lower cost.
The present disclosure provides, among other things, a multi-layer membrane for an acoustic transducer that may provide improved sound reproduction, thermal stability, and a long life time at a reduced cost relative to known multi-layer membrane configurations. In an embodiment, such a membrane may comprise a first layer comprising a first material, a second layer disposed on the first layer, the second layer comprising a second material that is different from the first material, and a third layer disposed on the second layer, the third layer comprising a third material that is different from the first material and the second material. The third layer may be configured to be coupled with a moveable coil. The first material may be a polyaryletherketone (PAEK), such as polyether ether ketone (PEEK), the second material may be acrylate, and the third material may be polyetherimide (PEI) or polycarbonate (PC).
An embodiment of a method of manufacturing an acoustic transducer may comprise providing a first membrane layer, the first membrane layer comprising a first thermoplastic material, disposing a second membrane layer on the first membrane layer, and disposing a third membrane layer on the second membrane layer, the third membrane layer comprising a second thermoplastic material that is different from the first thermoplastic material, the second thermoplastic material being more chemically reactive than the first thermoplastic material.
An embodiment of an acoustic transducer may comprise a moveable electromagnetic coil and a membrane. The membrane may comprise a first layer comprising a first material, a second layer disposed on the first layer, the second layer comprising a second material that is different from the first material, and a third layer disposed on the second layer, the third layer comprising a third material that is different from the first material and the second material. The third layer may be coupled with the coil. The third material may be PEI or PC.
Referring to the drawings, wherein like reference numerals refer to the same or similar features in the various views,
The transducer 10 may find use, for example only, as a part of a microphone and/or speaker, in an embodiment, in any appropriate application. For example, the transducer 10 may find use in a cell phone or other portable device, in an embodiment.
The membrane 18 may have a circular, rectangular, or other shape, depending on the desired shape and properties of the transducer 10. The membrane 18 and coil 16 may be generally disposed around an axis A, and the membrane 18 may generally include three radial portions, in an embodiment. The membrane may include a central radial portion 20, a transition radial portion 22, and an outer radial portion 24. The transition portion 22 may be coupled with the moveable electromagnetic coil 16, in an embodiment, and the outer portion 24 may include a dome structure and may be coupled with a portion of the housing 12.
Ideally, the pressure wave produced by the membrane 18 would perfectly reproduce the signal characteristics of the signal input to the coil 16 across a wide range of frequencies, over a wide range of temperatures, and over a long life time of the transducer. Furthermore, particularly in micro-transducer embodiments (e.g., cell phone speakers and microphones), it may be desirable to reduce the excursion of the membrane 18 to allow for the size of the transducer 10 to be decreased. As a result, goals for the membrane 18 may include accurate sound reproduction, a large temperature tolerance, and a long life time, with minimal membrane excursion. In an embodiment, a multi-layer membrane may be used in the transducer 10, with different layers of the membrane providing different ones of the above-noted desired characteristics.
As noted above, a middle layer 28 consisting of acrylate may be used due to the excellent damping properties of acrylate in the typical frequency range of acoustic transducers (e.g., sounds in the human-audible frequency range). The damping properties of acrylate may reduce the excursion of the membrane 182, thereby permitting the transducer assembly to be reduced in size relative to a membrane having a larger excursion. The acrylate may be or may include, for example, an acrylate adhesive. Instead of or in addition to acrylate, a silicon adhesive may be used.
PEEK (or another PAEK material) may be used for one or more outer layers (e.g., the first layer 32) because of its good fatigue behavior. PEEK may have a crystalline structure (i.e., may be arranged in an ordered pattern at the atomic or molecular level—such atomic or molecular level structure may be referred to herein as crystallinity), may have a glass transition temperature of about one hundred and forty-one degrees Celsius (141° C.), and may be an anisotropic material. In an embodiment, instead of or in addition to PEEK, a material having some or all of the same material properties as PEEK (such as, for example, another PAEK material) may be used in the first layer 32 of the membrane 182.
PEI may be used for one or more outer layers (e.g., the third layer 34) because of its excellent gluing behavior and relatively low cost. That is, a membrane 182 consisting of layers 32, 28, 34 of PEEK, acrylate, and PEI may be lower in cost and easier to couple with a coil in a transducer than a membrane consisting of layers of PEEK, acrylate, and PEEK. PEI may have an amorphous crystallinity (i.e., an irregular order at the atomic or molecular level), may have a glass transition temperature of about two hundred and seventeen degrees Celsius (217° C.), and may be an isotropic material. PEI may provide improved gluing behavior (e.g., relative to a PAEK material) because PEI may be more chemically reactive than PAEK materials, in embodiments. In an embodiment, instead of or in addition to PEI, a material having some or all of the material properties as PEI (such as, for example, PC, PAR, PET or PEN) may be used in the third layer of the membrane.
The method 40 may further include a step 44 that includes disposing a second membrane layer comprising a second material that is different from the first material on the first membrane layer. The second membrane layer may comprise an acrylate material, in an embodiment.
The method 40 may further include a step 46 that includes disposing a third membrane layer comprising a third material that is different from the first and second materials on the second membrane layer. The third membrane layer may comprise a thermoplastic material that is different from the thermoplastic material used for the first membrane layer. For example, the third membrane layer may be or may include a PEI material or a TPE material having at least some of the same material properties as PEI (such as, for example, PC, PAR, PET or PEN).
The method 40 may further include a step 48 that includes processing the membrane layers to form the layers into a single membrane structure having a desired three-dimensional form. In an embodiment, the three-dimensional form of the membrane may include a central portion, transition portion, and outer portion as illustrated for the membrane 18 in
A first thermoforming process that may be used in the processing step is a stamping process. In an embodiment, a stamping process may include the use of a closed air cylinder to apply air pressure to form the membrane.
A second thermoforming process that may be used in the processing step is a drawing process. In an embodiment, a drawing process may include the application of air pressure to form the membrane.
Referring again to
The method 40 may further include a step 52 that includes coupling the membrane with a portion of the housing of the transducer. Coupling the membrane with the housing may include coupling the membrane with the housing with an adhesive (i.e., gluing the membrane to the housing), in an embodiment. In an embodiment, the third layer of the membrane (which may comprise, e.g., PEI, PC, PAR, PET or PEN) may be coupled with the housing.
It should be noted that numerous additions and alterations may be made to the method as explicitly illustrated and described without departing from the scope and spirit of the instant disclosure. For example, although certain steps of the method have been illustrated and described in a particular order, that order is not limiting except as explicitly set forth in the claims or as required by logic. Furthermore, additional steps may be performed in the method to complete the manufacture of a transducer, such as forming the membrane layers individually, forming the housing of the transducer, etc., which steps are within the ability and knowledge of a person of skill in the art.
Various embodiments are described herein to various apparatuses, systems, and/or methods. Numerous specific details are set forth to provide a thorough understanding of the overall structure, function, manufacture, and use of the embodiments as described in the specification and illustrated in the accompanying drawings. It will be understood by those skilled in the art, however, that the embodiments may be practiced without such specific details. In other instances, well-known operations, components, and elements have not been described in detail so as not to obscure the embodiments described in the specification. Those of ordinary skill in the art will understand that the embodiments described and illustrated herein are non-limiting examples, and thus it can be appreciated that the specific structural and functional details disclosed herein may be representative and do not necessarily limit the scope of the embodiments, the scope of which is defined solely by the appended claims.
Reference throughout the specification to “various embodiments,” “some embodiments,” “one embodiment,” or “an embodiment”, or the like, means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases “in various embodiments,” “in some embodiments,” “in one embodiment,” or “in an embodiment”, or the like, in places throughout the specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. Thus, the particular features, structures, or characteristics illustrated or described in connection with one embodiment may be combined, in whole or in part, with the features structures, or characteristics of one or more other embodiments without limitation given that such combination is not illogical or non-functional.
Although numerous embodiments of this invention have been described above with a certain degree of particularity, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this disclosure. All directional references (e.g., plus, minus, upper, lower, upward, downward, left, right, leftward, rightward, top, bottom, above, below, vertical, horizontal, clockwise, and counterclockwise) are only used for identification purposes to aid the reader's understanding of the present disclosure, and do not create limitations, particularly as to the position, orientation, or use of the any aspect of the disclosure. As used herein, the phrased “configured to,” “configured for,” and similar phrases indicate that the subject device, apparatus, or system is designed and/or constructed (e.g., through appropriate hardware, software, and/or components) to fulfill one or more specific object purposes, not that the subject device, apparatus, or system is merely capable of performing the object purpose. Joinder references (e.g., attached, coupled, connected, and the like) are to be construed broadly and may include intermediate members between a connection of elements and relative movement between elements. As such, joinder references do not necessarily infer that two elements are directly connected and in fixed relation to each other. It is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative only and not limiting. Changes in detail or structure may be made without departing from the spirit of the invention as defined in the appended claims.
Any patent, publication, or other disclosure material, in whole or in part, that is said to be incorporated by reference herein is incorporated herein only to the extent that the incorporated materials does not conflict with existing definitions, statements, or other disclosure material set forth in this disclosure. As such, and to the extent necessary, the disclosure as explicitly set forth herein supersedes any conflicting material incorporated herein by reference. Any material, or portion thereof, that is said to be incorporated by reference herein, but which conflicts with existing definitions, statements, or other disclosure material set forth herein will only be incorporated to the extent that no conflict arises between that incorporated material and the existing disclosure material.
This application claims the benefit of priority to U.S. provisional application No. 61/985,837, filed Apr. 29, 2014, which is hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61985837 | Apr 2014 | US |
