CN221103560U - Loudspeaker - Google Patents

Abstract

The present application provides a speaker, comprising: the back electrode plate assembly comprises two back electrode plates, each back electrode plate comprises a conductive electrode plate and an electret material layer which are combined, and the two conductive electrode plates are arranged close to each other; the two support frames are respectively arranged at the outer sides of the two electret material layers, and through holes are formed in the support frames; the two vibrating diaphragms are respectively arranged at the outer sides of the two supporting frames, and each vibrating diaphragm comprises an elastic film and a conductive layer which are arranged in a fitting way; the two electret material layers are respectively stored with the same kind of charges, and the two conductive layers are respectively used for inputting two alternating current electric signals with equal size and opposite phases; or the two electret material layers respectively store different charges, and the two conductive layers are respectively used for inputting two alternating current electric signals with equal magnitude and same phase. The loudspeaker provided by the application has the advantages of simple structure, high sensitivity and excellent performance.

Description

Loudspeaker

Technical Field

The application relates to the technical field of sound production devices, in particular to a loudspeaker.

Background

The speaker is widely used as an electronic product for converting an electric signal into a sound signal in various electronic products such as a mobile phone, an earphone, a television, a computer, and the like. Compared with a moving coil electromagnetic loudspeaker, the electrostatic loudspeaker relies on attraction or repulsion of electric field force to the vibrating diaphragm to drive the vibrating diaphragm to vibrate to make sound. The electrostatic loudspeaker does not need complex structures such as an electromagnet, a coil and the like, and is light and thin in structure and excellent in frequency response, transient response and the like.

At present, the existing electrostatic loudspeaker mostly provides alternating voltage for two polar plates through a step-up transformer, direct current bias voltage is applied to the vibrating diaphragm, and the vibrating diaphragm is pushed to push and pull to reciprocate at the balance position under the action of electric field force, so that air is pushed to make sound.

Because the electric field force acting on the diaphragm is in direct proportion to the magnitude of the DC bias voltage, a very high DC voltage, such as about 500V, is needed, which obviously increases the complexity and difficulty of the system and also affects the production cost and application popularization of the product.

The electrostatic loudspeaker adopting the electret structure can well solve the problems, the complexity and the production cost of the traditional electrostatic loudspeaker can be reduced, but the electret electrostatic loudspeaker in the prior art still has the problems of low sensitivity, high distortion and the like.

Disclosure of Invention

Based on the above, the application provides a speaker to improve at least one of the problems of complex structure, low sensitivity, high distortion and the like in the prior art.

In order to achieve the above object, the technical solution of the embodiment of the present application is as follows:

an embodiment of the present application provides a speaker including:

The back electrode plate assembly comprises two back electrode plates, each back electrode plate comprises a conductive electrode plate and an electret material layer which are combined, and the two conductive electrode plates are arranged close to each other;

The two support frames are respectively arranged at the outer sides of the two electret material layers, and through holes are formed in the support frames;

the two vibrating diaphragms are respectively arranged at the outer sides of the two supporting frames, and each vibrating diaphragm comprises an elastic film and a conductive layer which are arranged in a fitting way;

The two electret material layers are respectively stored with the same kind of charges, and the two conductive layers are respectively used for inputting two alternating current electric signals with equal size and opposite phases; or the two electret material layers respectively store different charges, and the two conductive layers are respectively used for inputting two alternating current electric signals with equal magnitude and same phase.

In one embodiment, the back electrode plate assembly is provided with a plurality of through holes, and a damping net is arranged between the two conductive electrode plates and used for shielding the through holes.

In one embodiment, the damping net is made of metal, the thickness of the damping net ranges from 0.03mm to 3mm, and the mesh number of the damping net ranges from 100 meshes to 1000 meshes.

In one embodiment, the back plate has a thickness in the range of 0.05mm to 3mm and the electret material layer has a thickness in the range of 1 μm to 100 μm.

In one embodiment, the conductive layers are each disposed toward a side proximate to the back plate assembly.

In one embodiment, the surfaces of the two conductive layers are respectively provided with a plurality of peak portions.

In one embodiment, the height of the spikes is no greater than 0.5mm.

In one embodiment, the elastic membrane has a thickness of no more than 10 μm and/or the spacing between each of the diaphragms and the backplate assembly ranges from 0.05mm to 3mm.

In one embodiment, the two diaphragms are symmetrically disposed on both sides of the back plate assembly.

In one embodiment, the speaker further includes a support pad, and a plurality of support pads are respectively disposed between the back plate assembly and each of the diaphragms.

In one embodiment, the support frame includes an insulating portion and a conducting portion that are disposed in combination, the conducting portion is disposed in conducting relation with the conductive layer, and the two insulating portions are disposed adjacent to the back plate assembly respectively.

In one embodiment, the loudspeaker further comprises protection components respectively arranged at the outer sides of the two diaphragms, wherein the protection components respectively comprise a buffer pad, a cover body and a protection layer which are sequentially overlapped; the buffer cushion is arranged towards one side close to the vibrating diaphragm; holes matched with the through holes are respectively formed in the buffer cushion and the cover body.

The application has at least the following beneficial effects: the back electrode plate assembly of the loudspeaker provided by the embodiment of the application comprises two back electrode plates, and the two sides of the back electrode plate assembly are respectively provided with a supporting frame and a vibrating diaphragm in sequence. By storing charges in the electret material layer of the back electrode plate, direct-current voltage exists in the electret material layer, so that an external power amplifier or circuit is not needed to provide bias voltage for an electrostatic field, and the complexity of a loudspeaker structure is reduced. The two back polar plates arranged in a back direction can double the direct current voltage, and meanwhile, the driving force of the vibrating diaphragm is more symmetrical, so that the output frequency curve of the loudspeaker is optimized and the distortion is reduced. The two back electrode plates are stored with the same kind of charges, and the two diaphragms apply alternating current signals with opposite phases, so that the two diaphragms always keep synchronous motion when vibrating, and the distortion of output sound pressure is further reduced, so that a lossless high-quality audio signal is output.

Drawings

Fig. 1 is a schematic diagram of the overall structure of a speaker according to an embodiment of the present application.

Fig. 2 is an exploded view of the speaker of fig. 1.

Fig. 3 is a schematic cross-sectional view of a back plate assembly according to an embodiment of the application.

Fig. 4 is a schematic cross-sectional view of a back plate assembly according to another embodiment of the present application.

Fig. 5 is a schematic cross-sectional view of an assembled back plate assembly and a support frame according to an embodiment of the application.

Fig. 6 is a schematic cross-sectional view of the assembled diaphragm, backplate assembly and support frame according to an embodiment of the present application.

Fig. 7 is a schematic cross-sectional structure of the speaker of fig. 1.

Fig. 8 is a schematic diagram illustrating a stress situation of a diaphragm of a speaker according to an embodiment of the application.

Fig. 9 is a frequency response curve of a speaker according to an embodiment of the application.

The meaning of the various reference numerals in the drawings is as follows:

1. A protective assembly; 11. a protective layer; 12. a cover body; 13. a cushion pad;

2. a vibrating diaphragm; 21. an elastic film; 22. a conductive layer;

3. a support frame; 31. an input pin; 32. a conduction part; 33. an insulating part; 331. a positioning groove;

4. A back-plate assembly; 40. a back plate; 41. a conductive plate; 42. a layer of electret material; 43. a through hole; 44. damping net.

Detailed Description

The technical scheme of the application is further elaborated below by referring to the drawings in the specification and the specific embodiments.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the implementations of the application. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.

In the description of the present application, it should be understood that the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like indicate orientations or positional relationships based on the orientation or positional relationships shown in the drawings, merely to facilitate describing the present application and simplify the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present application. In the description of the present application, unless otherwise indicated, the meaning of "a plurality" is two or more.

In the description of the present application, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present application will be understood in specific cases by those of ordinary skill in the art.

Referring to fig. 1 and 2, a speaker according to an embodiment of the present application includes a back plate assembly 4, two support frames 3, and two diaphragms 2.

As shown in fig. 3, the back plate assembly 4 includes two back plates 40, each back plate 40 including one conductive plate 41 and one electret material layer 42, respectively, in a conforming arrangement. The two conductive plates 41 are disposed close to each other, i.e., the two back plates 40 are disposed back to back, the two conductive plates 41 are disposed close to each other, the two electret material layers 42 are disposed away from each other, and the same kind of charge or different kinds of charge are stored in the two electret material layers 42. When the two electret material layers 42 respectively store the same kind of charges, the two conductive layers 22 are respectively used for connecting two equal-magnitude and opposite-phase alternating current signals. When the electret material layers 42 store different charges, the two conductive layers 22 are used for respectively connecting two ac electric signals with equal magnitude and same phase. Specifically, in the present embodiment, a certain number of through holes 43 are formed in the back plate assembly 4, that is, through holes 43 are correspondingly formed in the back plate 40 and the electret material layer 42, respectively. The through holes 43 can function to adjust air compliance (air elasticity or hardness) and acoustic damping. By polarizing electret material layer 42, a certain amount of charge is stored in electret material layer 42. For example, negative high voltage polarization is performed on the two electret material layers 42 respectively by negative high voltage of-11 KV, so that stable negative charges are stored in each electret material layer 42 respectively. Of course, positive high voltage polarization may be used to store positive charges in each electret material layer 42, but negative charges are generally more stable than positive charges, so negative high voltage polarization is preferred. It is also possible to polarize one electret material layer 42 at a positive high voltage and to polarize the other electret material layer 42 at a negative high voltage so that the two electret material layers 42 store different charges, respectively. The two polarized conductive plates 41 are arranged back to back, through holes 43 on the conductive plates 41 are aligned, and the two polarized electret material layers 42 are respectively arranged towards the outer sides (near the diaphragm 2). The electret material layer 42 is usually made of PTFE (polytetrafluoroethylene) or an electret material such as FEP (fluorinated ethylene propylene copolymer or perfluoroethylene propylene copolymer). The conductive plate 41 is made of a conductive material, such as stainless steel sheet metal, nickel-plated copper sheet metal, or other surface-conductive material. The thickness of the back plate 40 in this embodiment is typically between 0.05mm and 3mm, wherein the electret material layer 42 is between 1 μm and 100 μm, the back plate 40 is preferably between 0.1mm and 0.3mm, and the electret material layer 42 is preferably between 20 μm and 50 μm. Products in this thickness range are easier to process and store more charge, resulting in a greater driving force for the electric field. The electret material layer 42 may be made of, for example, PTFE (polytetrafluoroethylene) material, and the thickness of the PTFE material is preferably 20 μm to 50 μm.

As shown in fig. 4, in some embodiments, the back plate assembly 4 may further include a damping mesh 44, where the damping mesh 44 may be disposed between the two conductive plates 41, and the damping mesh 44 is used to block the through holes 43 on the back plate 40 to adjust the compliance and acoustic damping of the air. The damping net 44 may be made of metal, preferably stainless steel, and the thickness of the damping net 44 is 0.03 mm-3 mm, and the mesh number of the damping net 44 is 100 mesh-1000 mesh. By selecting the damping nets 44 with different thicknesses and meshes, the vibration damping of the vibrating diaphragm 2 can be adjusted, so that the vibrating diaphragm 2 is easy to vibrate and cannot excessively vibrate during vibration, the effect of adjusting the frequency response curve (valley cutting and peak filling, and the frequency response curve is flatter) of the sound pressure output of the product on the basis of not influencing the sound pressure output is achieved, and the expected design result is achieved.

As shown in fig. 2 and 5, the support frame 3 of the present embodiment includes an insulating portion 33 and a conducting portion 32 that are disposed in combination, the conducting portion 32 is disposed in conduction with the conductive layer 22, and the two insulating portions 33 are disposed near the back plate assembly 4, respectively. The two insulating parts 33 are respectively provided with a positioning groove 331 at one side close to the back electrode plate 40, the positioning grooves 331 are used for installing the back electrode plates 40, and the two back electrode plates 40 are respectively installed in the corresponding positioning grooves 331. During installation, the positioning groove 331 of one supporting frame 3 can be placed upwards, the back electrode plate assembly 4 is placed in the positioning frame, the positioning groove 331 of the other supporting frame 3 is placed downwards, and the back electrode plate assembly 4 is buckled, so that the outer contours of the two supporting frames 3 are aligned. After installation, the electret material layers 42 of the two back-electrode plates 40 are arranged close to the corresponding support frames 3, respectively. To facilitate the input connection of external electrical signals, protruding input pins 31 may be provided at the edges of the two conducting portions 32, respectively. The two supporting frames 3 have a certain mechanical strength, and the supporting frames 3 in this embodiment adopt an FR-4 epoxy glass cloth board (i.e. a substrate of a PCB printed circuit board) of a copper-clad plate, that is, the insulating portion 33 is an epoxy glass cloth board, and the conducting portion 32 is a copper-clad plate material. After the support frames 3 are machined, they are formed into a desired shape, for example, a plurality of screw through holes 43 may be provided correspondingly, and the two support frames 3 and the back plate assembly 4 interposed therebetween may be fixed by a connecting member such as a bolt. The supporting frame 3 may be made of other materials, so long as the insulating portion 33 meets the insulating requirement and the conducting portion 32 meets the conductive requirement, and the specific choice of metal or non-metal material is not required.

As shown in fig. 6, two diaphragms 2 are respectively disposed outside the two support frames 3, and each diaphragm 2 includes an elastic film 21 and a conductive layer 22 that are bonded to each other. The elastic film 21 of the diaphragm 2 may be a thin film having a certain elasticity, and the smaller the thickness thereof, the better the product performance. In the present embodiment, a PPS (polyphenylene sulfide) film of 2 μm is used, but it is needless to say that other materials may be used, for example, a film such as PET (polyethylene terephthalate) film. For better performance, it is required that the thickness is not more than 10 μm. The diaphragm 2 can be manufactured, for example, by stretching the elastic film 21 flat, fixing the elastic film 21 by a jig, providing the elastic film 21 with a certain tension, and vacuum plating the elastic film 21 with the tension in a vacuum furnace to form a conductive layer 22 on the surface thereof, wherein the conductive layer 22 may be made of nickel, for example. The conductive layer 22 may be formed on the surface of the elastic film 21 by surface coating or other methods, and the material of the conductive layer 22 may be carbon powder, graphene, or the like. The diaphragm 2 is preferably a thin film with the thickness smaller than 2 μm, the thickness of the film is very thin, the vibration quality is very small, the transient response of the output sound pressure of the product is better, and the frequency response range of a high-frequency band is higher, for example, the frequency response range can reach more than 36 KHZ. The conductive layer 22 side of the prepared diaphragm 2 is disposed toward the conductive portion 32 of the support frame 3, and the conductive layer 22 and the conductive portion 32 are in good contact. Two ac electric signals with equal magnitude and opposite phases can be respectively input to the conductive layers 22 of the two diaphragms 2 through the two input pins 31, so that an electrostatic field is formed between the two diaphragms 2. The distance between each diaphragm 2 and the corresponding back plate 40 (i.e. the back plate 40 closest to each diaphragm 2 is the corresponding back plate 40) is determined by the thickness of the partial structure of the corresponding support frame 3, which is also the vibration space of the diaphragm 2. The smaller the distance between the diaphragm 2 and the back plate 40, the higher the sound pressure output by the product, but the more easily the diaphragm 2 is adsorbed to the back plate 40, which is likely to cause poor performance. On the other hand, the larger the distance between the diaphragm 2 and the back plate 40 is, the smaller the sound pressure output by the product is, but the less likely the film is to be absorbed, so that the distance between the diaphragm 2 and the back plate 40 is preferably set to 0.05mm to 3mm, more preferably 0.1mm to 1 mm.

Positioning the conductive layer 22 toward the side proximate the backplate assembly 4 can reduce the spacing between the conductive layer 22 and the backplate 40, and in other embodiments, the conductive layer 22 may alternatively be positioned away from the backplate assembly 4.

In some embodiments, a number of peaks (not shown) may also be provided on the surface of the conductive layer 22 of the diaphragm 2, requiring that the height of the peaks be no more than 0.5mm. The peak portion can be manufactured, for example, by placing the base material of the elastic film 21 on a gas-permeable steel mold having micro holes on the surface, and applying a high temperature and high pressure treatment to the base material, so that an elastic film 21 having many irregular fine peak protrusions on the surface is obtained, then flattening the elastic film 21, applying a tension to the elastic film by a jig and fixing the elastic film, and placing the elastic film in a vacuum furnace to vacuum-plate a conductive layer 22, so that the conductive layer 22 also has many irregular fine peak protrusions to form the peak portion. When an alternating electric field is applied to the conductive layer 22, these irregular fine spike projections enhance the average electrostatic field strength applied to the diaphragm 2 according to the enhanced characteristics of the electrostatic field at the edges of the conductor (e.g., to a certain extent, i.e., tip discharge, i.e., charge collection toward the tip, and enhancement of the tip electric field), thereby enhancing the driving electric field force to the diaphragm 2 and further enhancing the output sound pressure of the electrostatic speaker. The peak portions may be produced, for example, by roughening the conductive layer 22 attached to the surface of the elastic film 21 while keeping the substrate constant, so that the conductive layer 22 may have many irregular fine peak projections, and the same effect may be obtained. The specific manner of manufacturing the peak portion is not limited.

The two back plates 40 are arranged back-to-back, i.e. the plates are brought together and the electret material layer 42 is arranged towards the outside, the through holes 43 of the two back plates 40 being aligned so that air can pass through freely. The two diaphragms 2 are respectively located at two sides of the back plate 40 and are parallel to the surface of the back plate 40, and a certain interval is formed between the two diaphragms and the back plate 40, and preferably, the conductive layers 22 of the two diaphragms 2 are respectively located near the back plate 40. It is also possible to arrange the spacing between the two diaphragms 2 and the back-plate 40 equally or symmetrically with respect to the central plane of the two back-plate assemblies 4. The supporting frame 3 is used for fixing the back electrode plate assembly 4 and the two diaphragms 2, and simultaneously provides vibration space for the two diaphragms 2, the conducting part 32 of the supporting frame 3 is provided with an input pin 31, and the input pin 31 can be used for connecting an input signal to the conductive layer 22 of the diaphragms 2. Preferably, the two back-plates 40 are arranged mirror-symmetrically with respect to the two diaphragms 2 about the geometric symmetry center of the back-plate assembly 4.

The distance between the two diaphragms 2 and the back electrode plate 40, namely the vibration space of the diaphragms 2 is determined by the local structure thickness of the support frame 3, so that the requirements on the assembly process are simplified in design, and the complete symmetry of the vibration space of the two diaphragms 2 is ensured.

When the two electret material layers 42 store the same kind of charges, for example, both store negative charges or both store positive charges, respectively, two audio voltages of equal magnitude and opposite phases are applied to the two input pins 31, respectively, so as to form an electric field for driving the diaphragm 2 to vibrate. When two electret material layers 42 respectively store different charges, such as one stores positive charges and the other stores negative charges, two audio voltages with equal magnitude and same phase are required to be applied to two input pins 31 respectively, and an audio voltage with opposite phase to the audio voltage input by the vibrating diaphragm 2 is input to the conductive plate 41 of the back plate 40 corresponding to the vibrating diaphragm 2, that is, when one vibrating diaphragm 2 inputs +v, the conductive plate 41 corresponding to the vibrating diaphragm is input to-V, the other vibrating diaphragm 2 inputs +v, and the conductive plate 41 corresponding to the vibrating diaphragm is input to-V; when one diaphragm 2 is input with-V, the corresponding conductive electrode plate 41 is input with +V, the other diaphragm 2 is input with-V, and the corresponding conductive electrode plate 41 is input with +V.

In this embodiment, the PTFE film is used to store charges and is placed on the stationary backplate 40, and the thin PPS or PET film which is easy to drive is used as the main material of the diaphragm 2 and is symmetrically placed on two sides of the backplate assembly 4, so as to form PUSH-PULL symmetrical driving.

The larger the spacing between the diaphragm 2 and the backplate 40, the higher the signal voltage required to achieve the same acoustic pressure output, which increases the complexity of the power amplifier or circuitry. On the contrary, the smaller the distance between the diaphragm 2 and the back plate 40, the lower the signal voltage required for obtaining the same sound pressure output, but the risk of film suction is increased, namely, the diaphragm 2 cannot vibrate freely due to the fact that the electrostatic force adsorbs the diaphragm 2 to the back plate 40, so that the output sound pressure of a product is reduced sharply. Based on the above-mentioned problems, a support pad (not shown) may be added to the speaker, so that a proper distance between the diaphragm 2 and the back plate 40 is maintained, and the risk of sucking the diaphragm 2 is reduced. The support pad is arranged between the back electrode plate 40 and the corresponding vibrating diaphragm 2, the number of the support pads can be multiple, and the support pads are discretely distributed along the surface of the vibrating diaphragm 2, one end of each support pad can be fixedly connected with the back electrode plate 40, the other end of each support pad is fixedly connected with the vibrating diaphragm 2, or only one end of each support pad can be fixedly connected with the back electrode plate 40. The support pad may be a soft rubber pad, such as a silica gel pad, etc., and the support pad may be a column, and the cross-section of the support pad may be a geometric shape such as a circle, a cross, a square, a triangle, etc., which is not particularly limited. The thickness of the support pad is similar to the distance between the vibrating diaphragm 2 and the back electrode plate 40, so that the space distance between the vibrating diaphragm 2 and the back electrode plate 40 can be supported, and the risk of film suction failure under high voltage or close distance is avoided.

As shown in fig. 2 and 7, the speaker of the present embodiment may further include protection components 1 disposed outside the two diaphragms 2, respectively, where the protection components 1 include a cushion pad 13, a cover 12, and a protection layer 11 sequentially stacked. The cushion pad 13 is arranged towards one side close to the vibrating diaphragm 2, and holes matched with the through holes are respectively arranged on the cushion pad 13 and the cover body 12.

Specifically, the cushion pad 13 may be made of a soft material having elasticity such as rubber, silicone rubber, or the like. The cover body 12 and the protective layer 11 can protect and fix the components inside, so as to avoid the influence of foreign matters on the hearing of the loudspeaker or the damage of the components such as the vibrating diaphragm 2. The protective layer 11 may be made of a breathable or acoustically transparent material, such as a dust screen. During installation, a buffer pad 13 is respectively placed on the outer sides of the two diaphragms 2, and then a cover body 12 and a protective layer 11 are placed on the buffer pad 13, so that the outer contour and the holes of the protective component 1 are aligned with the outer contour and the through holes of the supporting frame 3. After the assembly is completed, all components can be fixedly connected through connecting pieces such as bolts, so that all layers of structures of the loudspeaker are tightly combined together, and the layers are attached to each other to form a complete loudspeaker product.

As shown in fig. 8, the working principle of the speaker of the present embodiment is as follows (taking as an example that two electret material layers 42 respectively store negative charges, and two conductive layers 22 respectively input two ac electric signals with equal magnitudes and opposite phases):

The surfaces of the two vibrating diaphragms 2 are respectively provided with a conductive layer 22, the two vibrating diaphragms 2 are placed at a certain distance, two back-to-back placed back electrode plates 40 are placed in the middle of the two vibrating diaphragms 2, and a certain distance is reserved between the two vibrating diaphragms 2 and the two back electrode plates 40. The electret material layers 42 of the back-plates 40 have been polarized so that a certain electrostatic charge Q is stored in the electret material layers 42 of the two back-plates 40, which electrostatic charge generates an electrostatic field between the two diaphragms 2, as in the present embodiment a negative electrostatic charge is polarized. When two alternating electric signals with opposite external phases are respectively applied to the two input pins 31, the alternating electric signals are respectively input to the conductive layers 22 of the two diaphragms 2 through the two input pins 31. Assuming that the polarities of the electric fields of the two alternating electric signals with opposite phases are positive at the top and negative at the bottom (in the direction shown in the drawing), at this moment, the polarities of the electric fields on the upper diaphragm 2 are positive, and are attracted by the negative charges stored in the back plate 40 and are pulled downward, so that the upper diaphragm 2 is displaced from top to bottom, i.e., moves toward the back plate 40. The polarity of the electric field on the lower diaphragm 2 is negative and is repelled by the negative charge stored in the back plate 40 and is pushed downward, so that the lower diaphragm 2 is displaced from top to bottom, i.e. moves away from the back plate 40. If the polarity of the electric field applied to the two diaphragms 2 is reversed, as is positive and negative, the upper diaphragm 2 is moved upward by an upward repulsive force, i.e., toward a direction away from the back plate 40, and the lower diaphragm 2 is moved upward by an upward attractive force, i.e., toward a direction toward the back plate 40. Therefore, the upper vibrating diaphragm 2 and the lower vibrating diaphragm 2 can generate reciprocating synchronous vibration under the action of alternating audio signals, so that air on two sides is pushed to make sound.

Specifically, in one embodiment, specific parameters are as follows: the thickness of the back electrode plate 40 is 0.3mm, the polarization potential is-200V, and the amplitude of the alternating audio signal is 450V; the thickness of the diaphragm 2 is 2 μm, the material of the elastic film 21 of the diaphragm 2 is PPS film, the surface tension is 110 (relative value), and the surface of the elastic film 21 is plated with nickel to form a conductive layer 22; the spacing between the back plate 40 and the diaphragm 2 is 0.5mm, and the aperture ratio of the back plate assembly 4 is 15%. The frequency response curve of the loudspeaker at this time is shown in fig. 9, the sound pressure level of the loudspeaker at the frequency of 2KHz is 91dBSPL, and compared with the traditional moving coil loudspeaker, the loudspeaker can perfectly replace the application of the moving coil loudspeaker in the corresponding scene.

According to the capacitor formula c=q/U (C is a capacitance value formed by the back plate and the diaphragm, Q is an electric charge amount stored after the electret material layer of the back plate resides, U is a voltage value between the back plate and the conductive layer of the diaphragm), so that the two back plates are stuck together back to back, the electret material layers face outwards, and when charges are stored in the electret material layers in a polarized manner, each electret material layer storing the charges has a direct current voltage, and the voltage value u=q/C is equivalent to a direct current voltage, so that the loudspeaker of the embodiment no longer needs an external power amplifier or circuit to provide the bias voltage Vpol for the loudspeaker. Meanwhile, the two back electrode plates are arranged back to back, the direct current voltage is doubled, the electret material layers are outwards arranged, the distance between the electret material layers and the vibrating diaphragm is minimized, the electric field force acting on the vibrating diaphragm is higher (the distance between the direct current voltage and the vibrating diaphragm is smaller, the electric field force acting on the vibrating diaphragm is larger), and the output sound pressure of the loudspeaker is larger. Compared with the design of a single back plate, the design of two back-to-back plates not only doubles the direct current voltage, but also is more symmetrical to the driving force of the vibrating diaphragm, thereby achieving the effects of optimizing the output frequency curve of the loudspeaker and reducing distortion.

In this embodiment, the alternating electric signals applied to the two diaphragms are equal in magnitude and opposite in phase; simultaneously, the two vibrating diaphragms and the back electrode plate are symmetrically arranged about the geometric center of the back electrode plate assembly, so that when the vibrating diaphragms vibrate, the upper vibrating diaphragm is far away from the back electrode plate due to repulsive force when attractive force is close to the back electrode plate. At this time, the nonlinear generated when the attractive force of the upper diaphragm is close to the back plate and the nonlinear generated when the repulsive force of the lower diaphragm is far away from the back plate are offset, and the mirror symmetry arrangement can greatly reduce the distortion of the output sound pressure of the loudspeaker, so that the theoretical distortion of the loudspeaker is towards zero, and a lossless high-quality audio signal is output.

In the loudspeaker of this embodiment, the elastic films of the two diaphragms are outside (for example, the PPS film layer is outside), and the elastic films of the two diaphragms and the support frame together form a sealed space region, and this sealed space region can play a role in sealing and protecting the materials disposed therein. For example, the chance of static charge stored on the back plate coming into contact with moisture in the air can be reduced, thereby avoiding decay in the amount of charge. And the high-temperature high-humidity oxidation and the like of the conductive layer and the back electrode plate on the vibrating diaphragm can be reduced, so that the stability and the reliability of the long-time operation of the loudspeaker are improved.

The thickness of the back electrode plate is between 0.05mm and 3mm, the elastic membrane of the vibrating membrane is a thin membrane such as PPS or PET with the thickness smaller than 10 mu m, the distance between the vibrating membrane and the back electrode plate is between 0.05mm and 3mm, and the total thickness of the loudspeaker is smaller than 5mm, so that the back electrode plate is ultrathin in design and can meet the application scene with the requirement of ultrathin products, such as a ceiling of an automobile. Meanwhile, the weight of the loudspeaker is very light, and the requirements of application scenes with light requirements, such as new energy automobiles and the like, can be met.

The loudspeaker has the advantages of simple structure, light and thin design, simple assembly process, no rare metals such as rare earth, low cost, high product stability and excellent performance.

Compared with a common electrostatic loudspeaker which needs direct-current bias voltage driving, the loudspeaker replaces the externally applied direct-current bias voltage with the voltage generated by electret static charge, thereby reducing the complexity of a driving system and the complexity of product design.

It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.

The foregoing is merely illustrative of the present application, and the present application is not limited thereto, and any person skilled in the art will readily recognize that variations or substitutions are within the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims (10)

1. A loudspeaker, comprising:

The back electrode plate assembly comprises two back electrode plates, each back electrode plate comprises a conductive electrode plate and an electret material layer which are combined, and the two conductive electrode plates are arranged close to each other;

The two support frames are respectively arranged at the outer sides of the two electret material layers, and through holes are formed in the support frames;

the two vibrating diaphragms are respectively arranged at the outer sides of the two supporting frames, and each vibrating diaphragm comprises an elastic film and a conductive layer which are arranged in a fitting way;

The two electret material layers are respectively stored with the same kind of charges, and the two conductive layers are respectively used for inputting two alternating current electric signals with equal size and opposite phases; or the two electret material layers respectively store different charges, and the two conductive layers are respectively used for inputting two alternating current electric signals with equal magnitude and same phase.

2. The loudspeaker of claim 1, wherein the back plate assembly has a plurality of through holes, and a damping net is disposed between the two conductive plates, and the damping net is used for shielding the through holes.

3. A loudspeaker according to claim 2, wherein the damping mesh comprises metal, the damping mesh has a thickness in the range of 0.03mm to 3mm, and the mesh size of the damping mesh is 100 mesh to 1000 mesh.

4. The loudspeaker of claim 1, wherein the back plate has a thickness in the range of 0.05mm to 3mm and the electret material layer has a thickness in the range of 1 μm to 100 μm.

5. The loudspeaker of claim 1, wherein the conductive layers are each disposed toward a side proximate the backplate assembly.

6. A loudspeaker according to claim 1, wherein the surfaces of the two conductive layers are provided with a plurality of peaks, respectively, the height of the peaks being no greater than 0.5mm.

7. The loudspeaker of claim 1, wherein the elastic membrane has a thickness of no more than 10 μm and/or the diaphragm is spaced from the backplate assembly by a distance in the range of 0.05mm to 3mm.

8. The loudspeaker of claim 1, wherein two of the diaphragms are symmetrically disposed on either side of the backplate assembly.

9. The loudspeaker of claim 1, further comprising a support pad, a plurality of the support pads being disposed between the backplate assembly and each of the diaphragms, respectively.

10. The loudspeaker of claim 1, wherein the support frame includes an insulating portion and a conductive portion disposed in combination, the conductive portion being disposed in conductive communication with the conductive layer, the two insulating portions being disposed proximate the backplate assembly, respectively.