Micro planar speaker

A micro speaker includes a planar diaphragm, spacers respectively disposed at one side surface of the planar diaphragm, an upper plate and a lower plate, one or more magnets and a circuit board. The planar diaphragm includes a vibrating diaphragm and a coil conductor. The coil conductor is stretched and bonded onto the vibrating diaphragm via an adhesive layer on the upper side surface of the planar diaphragm; the coil conductor is electrically connected to the circuit board. The speaker in this present invention can get a diameter of 15 mm or less, and a height is 5 mm or less.

FIELD OF THE INVENTION

The present invention relates to the field of sound elements or equipments, and especially for a micro planar speaker.

BACKGROUND OF THE INVENTION

A vibrating diaphragm of a traditional speaker includes the coil conductor made of aluminum foil, and has a large diameter, thus has a large area, and a size of the vibrating diaphragm is 20 mm×20 mm or more. Further, the vibrating diaphragm usually adopts a double-ended magnetic structure, which increases the thickness of the speaker. Such planar speakers have large sizes and volumes, most are suitable for headphones or flat supra-aural headphones, but not suitable for insert earphones, mobile phones, or tablet computers, yet cannot be widely used.

Therefore, an improved micro speaker is desired which overcomes the disadvantages of the prior art.

SUMMARY OF THE INVENTION

A main object of the present invention is to provide a micro planar speaker, to solve the problem of the existing speaker with a large size and volume.

to obtain the above object, a micro planar speaker in accordance with the present invention comprises: a planar diaphragm with an upper side surface and an opposite lower side surface; an upper and a lower spacers respectively disposed at the upper side surface and the lower side surface of the planar diaphragm, and each defining a cavity so as to form a magnetic gap at the side surface of the planar diaphragm; an upper plate and a lower plate respectively disposed on top of the upper spacer and below the lower spacer; one or more magnets; and a circuit board. The planar diaphragm comprises a vibrating diaphragm and one or more coil conductor; the coil conductor is stretched and bonded onto the vibrating diaphragm via an adhesive layer on one side surface of the planar diaphragm; opposite ends of one coil conductor respectively form a positive electrode and a negative electrode to electrically connect with the circuit board.

Preferably, a layout or pattern of the coil conductor is adapted to the magnets, and comprises one or more voice coils via the coil conductor winding; each voice coil corresponds to one magnet to form one sound unit; the magnet is arranged above or below the corresponding voice coil; and the coil conductor is a continuous conductive line.

Preferably, the layout or pattern of the coil conductor depends on a size of the speaker, and also depends on shape, number, arrays and arrangement the magnets; each voice coil includes one loop or sets of parallel loops of the conductive line, and defines a space inside the loop or loops.

Preferably, the loop or loops have one side thereof open to communicate with the space, whereby each loop is unclosed and is open at the same side; each loop is adapted to an outer contour of the corresponding magnet below or upon, and is arranged around the corresponding magnet; and the corresponding magnet is aligned to the voice coil.

Preferably, a first loop of conductive line in the voice coil is the most inner loop and encloses the space; one end of the coil conductor continuously winds to form all first loops of all voice coils one by one, and further winds outer parallel loops sequentially; the most outer loops finally extends to the other opposite end of the coil conductor; the loops in of the same voice coil are spaced each other, and are equally spaced.

Preferably, the voice coil has a dimension larger than the magnet; the magnets keep all N poles oriented towards the coil conductor or all S poles oriented towards the coil conductor; the voice coil is in a shape of a letter U according to one or more bar magnets, or the voice coil has unclosed regular shape or unclosed irregular shape according to the magnets with regular shape or irregular shape.

Preferably, the positive electrode and negative electrode at opposite ends of the coil conductor are arranged opposite to each other at an edge of the planar diaphragm, and each has an enlarged electric area for facilitating electric connection with the circuit board; and the positive electrode and negative electrode of the coil conductor are arranged on the upper side surface of the planar diaphragm.

Preferably, the upper and lower plates are made of magnetically conductive material; perforations through each plate are provided to allow air and sound waves to pass through, and are communicated with the cavity in the spacer at the same side surface of the planar diaphragm; and each plate has flat top and bottom surfaces.

Preferably, the speaker further comprises a magnet support; the magnet support defines a center cavity therethrough which is communicated with the cavity in the spacer at the same side surface of the planar diaphragm to allow air and sound waves to pass through; and the magnets are parallel arranged in the center cavity with a space therebetween and being communicated with and aligned to the perforation in the plate; the magnet support is mounted between the upper plate and the upper spacer; the magnet support has its top surface bonded to a lower surface of the upper plate to form a whole piece for an easy assembly.

Preferably, the positive electrode and negative electrode of the coil connector are electrically connected to the circuit board each by an elastic conductor; the circuit board has a pair of electric contacts for electrically connecting with the positive electrode and negative electrode.

Preferably, the pair of electric contacts is set on a rear surface of the circuit board; a positive terminal and a negative terminal are set on a top surface of the circuit board and used for electric connection with a sound equipment in which the speaker is mounted; the positive terminal and negative terminal are respectively electrically connected with the electric contacts; the circuit board is set on top of the upper plate.

Preferably, a plated-through hole is defined in each electric contact as so to form electric conductivity in the plated-through hole; the positive terminal and negative terminal are respectively electrically connected with one plated-through hole via electric lines on the top surface of the circuit board and thus electrically connect with the pair of electric contacts on the rear surface of the circuit board.

Preferably, the positive terminal and negative terminal are configured as soldering points for soldering connection; the positive terminal and negative terminal are treated via gold-plating or immersion-gold process so as to improve electric conductivity; the positive terminal and negative terminal each has an enlarged electric area for facilitating electric connection.

Preferably, the electric contacts are respectively aligned to and face the positive electrode and negative electrode of the coil conductor on the planar diaphragm; opposite ends of each elastic conductor are respectively resisted against one electric contact on the rear surface of the circuit board and one of the positive and negative electrodes of the coil conductor on the planar diaphragm.

Preferably, the elastic conductor is a compressible spring; the upper plate, and/or magnet support and/or the upper spacer respectively define through holding holes for holding the spring therein; one set of through holding holes are aligned each other to form one accommodating space for holding one spring and located between one electric contact and the positive electrode; the other set of through holding holes are aligned each other to form the other accommodating space for holding the other spring and located between the other electric contact and the negative electrode.

Preferably, an insulating ring is further set around the spring; the micro planar speaker further comprises a damper on its top and a dustproof net at its bottom; the damper is made of a breathable member.

Preferably, the circuit board defines through perforations communicated with the cavity in the upper spacer to allow air and sound waves to pass through; the circuit board, upper plate, magnet support, upper spacer, planar diaphragm, lower spacer, and lower plate are fastened together successively; a fastener is passed through a plurality of aligned holes disposed in the circuit board, upper plate, magnet assembly, upper spacer, planar diaphragm, lower spacer, and lower plate respectively for fixation.

Preferably, the micro planar speaker has a diameter of 15 mm or less, and/or a plane length and width each equal to or less than 15 mm, and/or a height is 5 mm or less; the speaker has a frequency spectrum of 20 Hz-40 KHz and 50 Hz-3 KHz, and has a sound distortion less than 1%; a total thickness of the planar diaphragm can be or less than 10 micrometers.

Preferably, the coil conductor is made from copper; the vibrating diaphragm is made from a thin film.

Preferably, wherein the coil conductor is made from annealed copper or electrolytic copper foil via etching way; and the vibrating diaphragm is made from PET film.

Other features and advantages of the invention will be apparent with reference to the following detailed description, taken together with the appended drawings, both of which are given by way of example, and not by way of limitation.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the exemplary embodiments illustrated in the drawings, and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended.

Referring toFIGS. 1-10, a micro planar speaker100provided in accordance with an embodiment of the present invention, comprises a planar diaphragm10, spacers9,19, plates5,15, magnets7mounted in a support structure8, and a circuit board3. Where an upper spacer9together with an upper plate5thereon is disposed at an upper side surface102of the planar diaphragm10, and defines a cavity90above the upper side surface102of the planar diaphragm10so as to form a magnetic gap. A lower spacer19together with a lower plate15below is disposed at an opposite lower side surface103of the planar diaphragm10, and also defines a cavity90below the lower side surface103of the planar diaphragm10so as to form another magnetic gap. At least one cavity90at the side surface102/103is inserted magnets7. In accordance with one embodiment of the present invention, the magnets7is inserted in the cavity90above the upper side surface102of the planar diaphragm10, and is mounted between the upper plate5and the upper spacer9. The circuit board3is set on top of the upper plate5. The circuit board3, upper plate5, magnet support structure8, upper spacer9, planar diaphragm10, lower spacer19, and lower plate15are fastened together successively. For example, a fastener may be passed through a plurality of aligned holes105disposed in the circuit board3, upper plate5, magnet support structure8, upper spacer9, planar diaphragm10, lower spacer19, and lower plate15respectively for fixation. In this embodiment, two screws14as fasters pass through the aligned holes105respectively disposed in the above elements and the end of each screw14is locked via a nut12. The micro planar speaker100further comprises a damper16on its top and a dustproof net13at its bottom. The damper16is made of a breathable member for further satisfying the frequency response and audio reproduction of the speaker100. Elastic connectors, such as a pair of springs4electrically connect between the circuit board3and the planar diaphragm10.

The micro planar speaker100is shaped and configured according to requirements of the sound devices which are used in, such as in a shape of square, ring, ellipse or others. The planar diaphragm10, spacers9,19, plates5,15, magnet support structure8, and circuit board3are shaped and configured according to the micro planar speaker100accordingly. Numerous alternative arrangements are also deemed suitable and include irregularly shaped micro planar speaker, and as well as the planar diaphragm10, spacers9,19, plates5,15, magnet support structure8, and circuit board3.

In accordance with the embodiment of the present invention, the planar diaphragm10, spacers9,19, plates5,15, magnet support structure8, and circuit board3are circular and are fastened together to form a circular planar speaker100.

Further referring toFIGS. 8-10, the planar diaphragm10in this embodiment comprises a vibrating diaphragm1and a coil conductor2. The coil conductor2is bonded to a top of the vibrating diaphragm1via an adhesive layer11, namely bonded to the upper side surface102of the planar diaphragm10; and opposite ends thereof form a positive electrode17and a negative electrode18on the upper side surface102. The coil conductor2is preferably made from copper, such as made from annealed copper or electrolytic copper foil. For example, the coil conductor2is made from soft copper with a thickness of 5 micrometers. The vibrating diaphragm1is made from a thin film. In a preferable embodiment, the electrolytic copper foil is coated with the adhesive layer11, and then is applied to the thin film, thereby the planar diaphragm10is obtained via laser etching. The coil conductor2with a line width of 0.06 mm can be achieved, and a minimum line width of 0.01 mm even can be achieved from soft copper via a micro-etching or laser etching way which benefits from material stability of copper. Thereby, based on such thin line width of the coil conductor2, the areas of the coil conductor2are reduced, a diameter of a circular planar diaphragm10and a circular planar speaker100can be reduced to 15 mm or less, and thus a micro speaker can be available.

Preferably, the vibrating diaphragm1is made from PET film, for example, from PET film with a thickness of 2 micrometers. PET film is such ultra thin which is beneficial for lower-frequency vibration of the speaker100and thus increases the frequency spectrum, and also can improve the audio reproduction, thereby, fuller and realer sound is available. The PET film has good toughness and high tensile strength so as to offer the diaphragm10in a stable tension, and which renders the speaker a good performance. The planar diaphragm10can be manufactured at a total thickness less than 10 micrometers, for example, the vibrating diaphragm1is used with PET film at a thickness of 2 micrometers and the adhesive layer11has a thickness of 2-3 micrometers. The lighter and thinner coil conductor2and vibrating diaphragm1of the present invention, improve the vibration and sound of the planar diaphragm10, and increase the frequency spectrum. The speaker100of the present invention has frequency spectrum of 20 Hz-40 KHz and 50 Hz-3 KHz, and has a sound distortion less than 1%.

The coil conductor2is a continuous conductive line, and forms a predefined pattern according to the magnets7via etching method from annealed copper or electrolytic copper foil. A total length and a line width of the continuous coil conductor2is determined by an impedance of the planar speaker100and a thickness of the annealed copper or electrolytic copper foil. A layout or pattern of the coil conductor2depends on the size of the micro planar speaker in the sound equipments, and also depends on the magnets7including the shape, number, arrays and arrangement of magnets7. The coil conductor2forms voice coils20each with a pattern and arrangement corresponding to one magnet7. Each voice coil20includes one loop or sets of parallel loops23of conductive lines via the coil conductor2winding, and defines a space22centrally inside the loop or loops23of the conductive line. Preferably, the loop or loops23have one side thereof open to the space22, namely, each loop23is not closed. The first loop23of conductive line in the voice coil20is the most inner loop and encloses the space22. One end of the coil conductor2continuously winds to form all first loops23of all voice coils20one by one, and further winds outer parallel loops23sequentially. The most outer loops23finally extend to the other opposite end of the coil conductor2. Loops23of the conductive line are spaced each other and preferably equally spaced. The coil conductor2forms one or more voice coils20according to the number and arrangement of the magnets7. Each voice coil20corresponds to one magnet7and together forms one sound unit, and the corresponding magnet7is arranged above or below the voice coil20preferably in a centrally parallel and aligned way. The corresponding magnet7positioned above or below the space22of the voice coil20. Each loop23of the conductive line is adapted to an outer contour of the magnet7and around the magnet7. Preferably, the voice coil20has a dimension larger than the magnet7, thus the most outer loop23of conductive line located around the outer contour of the magnet7. The same or smaller dimension of the voice coil20relative to the magnet7also can be used. The magnets7keep all N poles oriented towards the coil conductor2, or all S poles oriented towards the coil conductor2. The micro planar speaker100can comprises one or more sound unit. The sensitivity of the micro planar speaker100is proportional to the number of sound units, dimension of the magnets7, magnetic field, and the number of loops. The loops23are open at one side.

Both opposite ends of coil conductor (or conductive line)2are stretched to form the positive electrode17and negative electrode18. Both electrodes17,18are preferably arranged opposite to each other, and each has an enlarged electric area for facilitating electric connection with the circuit board3via the spring4. Further preferably, the positive electrode17and negative electrode18are located at the edge of the planar diaphragm10, on the upper side surface102, which also facilitates electric connection.

In a first embodiment as shown inFIGS. 8-10, the coil conductor2is arranged to form three voice coils20in shape of letter U aligned to three bar magnets7respectively, where the shape, number and arrangement of the voice coils20are adapted to and correspond to the magnets7. The conductor2also forms peripheral traces21along the edge of the diaphragm10for continuously winding the voices coils20. In this embodiment, each voice coil20includes but not limited to seven loops of the conductive line with top side open so as to form a shape of a letter U. Each magnet7covers above the space22, and has a width and length less than those of the coil conductor2. Each open loop23has a shape of letter U.

In a second embodiment as shown inFIG. 11, the coil conductor2is arranged to form two voice coils20each with several open and parallel loops23in a circular shape aligned to two cylindrical magnets7respectively. Each voice coil20defines a central space22. Each magnet7covers above the central space22of the coil conductor2. Opposite ends of the continuous coil conductor2extend to the positive electrode17and negative electrode18which have enlarged electric areas.

In a third embodiment as shown inFIG. 12, the coil conductor2is arranged to form one voice coil20with several parallel unclosed loops23in a square shape aligned to one square magnet7. The voice coil20defines a central space22. The magnet7covers above the central space22of the coil conductor2. The coil conductor2continuously winds to form the voice coil20and the peripheral traces21, opposite ends of the continuous coil conductor2extend to the positive electrode17and negative electrode18at the edge of the planar diaphragm10and each with an enlarged electric area.

The upper and lower spacers9,19are circular, while the shape is not limited to circular and is adapted to the shape and size of the speaker100, and each spacer9,19centrally defines the cavity90therethrough. Both spacers9,19are made from insulating material and are used to fix the planar diaphragm10and form a magnetic gap via the cavity90at both side surfaces of the planar diaphragm10. Preferably, the spacers9,19are made from fiberglass, such as fiberglass board with high mechanical strength. The planar diaphragm10is bonded between the upper and lower spacers9and19, and thus keeps planar and maintains a certain tension due to high mechanical strength of the spacers9,19, which ensures the planar diaphragm10with a stable and consistent frequency response.

The upper and lower plates5,15are circular, while the shape is not limited to circular and is adapted to the shape and size of the speaker100, and perforations51through each plate5,15are provided to allow air and sound waves to pass through. Perforations51are communicated with the cavity90. The upper and lower plates5,15are made from magnetically conductive material such as iron, metal alloy or the like, and can: (a) provide a mounting support for the magnets, (b) close the magnetic circuits between the plates5,15, and (c) provide a flat surface to further fix the diaphragm10.

Several bar magnets7can be used and aligned to the voice coils of the coil conductor2. There are three bar magnets7are used in an exemplary illustration inFIG. 5. The bar magnets7are mounted in the magnet support8. The magnet support8is circular in this embodiment, but not limited to circular according to the shape and size of the speaker100, defines a center cavity82therethrough which is communicated between the cavity90in the upper spacer9and the perforation51in the upper plate5. The bar magnets7are parallel arranged in the cavity82with a space84between the bar magnets7or between the bar magnet and inner wall of the magnet support8. The space84is communicated with and aligned to the perforation51in the upper plate5to allow air and sound waves to pass through. The inner wall of the cavity82forms fixing grooves85for mounting magnets7. Opposite ends of each bar magnet7is mounted in a pair of opposite fixing grooves85. The magnet support structure8is inserted between the upper plate5and the upper spacer9. Preferably, the magnet support structure8has its top surface bonded to the flat lower surface of the upper plate5to form a whole piece for an easy assembly. The bar magnet7also can have its top surface bonded to the flat lower surface of the upper plate5, and have bottom surfaces extended to the cavity90above the upper side surface102of the planar diaphragm10. The magnet support8is used to mount the magnets7.

FIGS. 3-5illustrate a single-ended planar-magnetic speaker100, where only one (upper) side surface of the planar diaphragm10is arranged with the magnets7. There is no magnet7set between the planar diaphragm10and the lower plate15. The coil conductor2is set only on the same side surface of the planar diaphragm10not both side surfaces. The magnets7are set above the side surface onto which the coil conductor2is stretched and bonded, and face the coil conductor2with the same poles. The single-ended planar-magnetic speaker100can reduce material cost, facilitate assembling, and make the speaker thinner and lighter.

The circuit board3in a circular shape is set on top of the upper plate5, defines through perforations37aligned to perforations51in the upper plate5to allow air and sound waves to pass through. A positive terminal31and A negative terminal32are set on a top surface35of the circuit board3and used for electric connection with the sound equipment in which the speaker100is mounted; and preferably, the positive terminal31and negative terminal32are configured as soldering points for soldering connection; and more preferably, can be treated via gold-plating or immersion-gold process so as to improve electric conductivity. There is a pair of electric contacts33are set on a rear surface36of the circuit is board3, and a plated-through hole34is defined in each contact33through the thickness of the board3via which the contact33is electrically connected with the inner wall and outer edges of the plated-through hole34. The positive terminal31and negative terminal32are respectively connected with one plated-through hole34via electric lines38on a top surface35of the board3thus electrically connect with the pair of electric contacts33on the rear surface36of the board3. The pair electric contacts33are aligned to and face the positive electrode17and negative electrode18of the planar diaphragm10. The electric lines38is formed by conductive sheet or by etching or printing process, each of which has an area to include the terminals31,32and the plated-through hole34therein so as to electrically connect.

Two springs4are used for electric connection between the board3and the planar diaphragm10. One spring4is used to electrically connect the negative electrode18of the coil conductor2to the negative terminal32of the board3, and the other spring4is used to electrically connect the positive electrode17of the coil conductor2to the positive terminal31of the board3. The spring4can be compression spring, leaf spring or spring plate or the like. Other elastic conductor can also be used to replace spring. Opposite ends of the elastic conductor are respectively and elastically resisted against the rear face36and the upper side surface102of the planar diaphragm10. In a detailed embodiment, opposite ends of one spring4are respectively resisted against one electric contact33of the board3and the positive electrode17of the coil conductor2, which forms a positive electric connection from positive electrode17to positive terminal31via the electric line38and plated-through hole34from one contact33. And opposite ends of the other spring4are respectively resisted against the other electric contact33of the board3and the negative electrode18of the coil conductor2, which forms a negative electric connection from negative electrode18to negative terminal32via the electric line38and plated-through hole34from the other contact33. More preferably, the spring4is a compressible, spiral spring. The spring4can be treated via gold-plating or immersion-gold process so as to improve electric conductivity. A reliable electric connection can be achieved in such way that the compressible spring has both ends tightly and respectively resisted against the contacts and the corresponding electrodes even during the diaphragm10vibrating.

In a preferable embodiment, the upper plate5, magnet support8and the upper spacer9respectively define through holding holes53,83,93for holding the spring4therein. One set of through holding holes53,83,93are aligned each other to form one accommodating space41for holding one spring4and located between one contact33and the positive electrode17. The other set of through holding holes53,83,93are aligned each other to form the other accommodating space42for holding the other spring4, and located between the other contact33and the negative electrode18.

More preferably, an insulating ring6such as a plastic ring, is further set in the accommodating space41,42for fixing and guiding the spring4. The insulating ring6is sleeved around the spring4, and can avoid short circuit between the spring4and the plate5/magnet support8. The magnet support8is made from electrically conductive materials, such as steel.

The damper16of a breathable member is used according to the desired frequency response of the speaker100in the sound equipment. The dustproof net13is set for preventing dust from outside into the speaker and thus affect its sound nature. The net13is made of Nylon net with 50-100 meshes, is bonded to the lower plate15to cover perforations51.

Referring toFIG. 13together, the exemplary planar speaker100has a height of 35.33 mm including the screw14and nut12, and the height of the board3, plate5,15, magnet support8, spacer9,19and the planar diaphragm10together is 25.58 mm, and the diameter of the speaker is 106.5 mm. In another example, the planar speaker100is circular with a diameter of 14.2 mm; wherein the board3, upper plate5, magnet support8and lower plate15each has a height of 0.6 mm; spacers9,19each has a height of 0.5 mm; the planar diaphragm10has a thickness of 0.01 mm, nut16has a height of 0.8 mm, the cap of the screw14has a height of 0.5 mm, whereby a micro planar speaker with a total height of 4.71 mm is achieved, which is suited for such sound equipments as in-ear headphones, mobile phones, and tablet computers. The micro planar speaker100of the present invention can get a diameter less than 15 mm and even less than 10 mm, a plane length and width each less than 15 mm and even less than 10 mm, and a height less than 5 mm.

The speaker100in accordance with the embodiment of the present invention are advantageous that the coil conductor2is made of soft copper or electrolytic copper with good material stability, can be manufactured a complicate conductive line and has a quite small area, which can increase the frequency spectrum, and thus a smaller size of the planar diaphragm10can be achieved. Further, the planar speaker100in this embodiment adopts a single-ended magnet circuit, so as to become thinner and lighter, to improve manufacturing and assembling efficiency, and also reduce the cost of manufacturing and materials. The positive and negative electrodes17,18of the coil conductor2and the positive and negative terminals31,32of the circuit board3are respectively electrically connected via compressible springs4and electric lines38on the board3to form positive and negative electric connection, the electric connection is transferred from the rear surface36to the top surface35of the board3via plated-through holes34, and preferably, the positive and negative terminals31,32of the circuit board3form soldering points, in such way to facilitate assembly and electric connection of the speaker in the sound equipment, especially facilitate electric connection by soldering, and thus improve reliability of electric connection. The micro planar speaker100of the present invention can keep a good sound quality while has a smaller size and volume, and is suitable for sound equipments such as insert earphones, mobile phones, or tablet computers which require a micro speaker.

Those skilled in the art in possession of this disclosure may now make numerous other modifications of, and departures from, the specific apparatus and techniques herein disclosed without departing from the inventive concepts. It is to be understood that the above-described embodiments and alternative arrangements are only illustrative of the application of the principles of the present invention. Thus, while the present invention has been shown in the drawings and fully described above with particularity and detail in connection with what is presently deemed to be the most practical and preferred embodiment(s) of the invention, it will be apparent to those of ordinary skill in the art that numerous modifications can be made without departing from the principles and concepts set forth herein within the spirit and scope of the invention. The disclosure set forth above is not intended to be limiting of the scope of the invention, which is defined by the appended claims.