EP2369855B1

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Info

Publication number: EP2369855B1
Application number: EP11162045.6A
Authority: EP
Inventors: Yi Tsung Cheng; Fang Ching Lee; Chih Chao Hsieh
Original assignee: HTC Corp
Current assignee: HTC Corp
Priority date: 2008-10-31
Filing date: 2009-09-02
Publication date: 2014-05-07
Anticipated expiration: 2029-09-02
Also published as: JP5054749B2; EP2369855A3; TW201018252A; EP2369855A2; EP2182737A1; JP2010109979A; TWI454156B; EP2182737B1

Description

The invention relates to a portable electronic device with an electro-acoustic transducer, and more particularly, to a portable electronic device with an electret electro-acoustic transducer.
Loudspeakers are a kind of device to make sound. The principle of making sound for the loudspeakers is to move the diaphragms thereof by electrical signals to push the air. Nowadays, the loudspeakers have been broadly used in electronic devices with the function of making sound, such as mobile phones, personal digital assistants (PDAs) and laptop computers.
One of the common loudspeakers is so-called dynamic loudspeaker. The principle of making sound for the dynamic loudspeaker is to drive a current through the voice coil to produce a magnet field. This magnetic field causes the voice coil to react to the magnetic field from a permanent magnet fixed to the frame of the loudspeaker thereby moving the diaphragm attached with the voice coil. Although such dynamic loudspeaker can provide very good quality of sound, the loudspeaker has a considerable thickness because its sound chamber is large. When such dynamic loudspeakers are used in the above-mentioned portable electronic devices, the thickness of these electronic devices cannot be reduced.
EP 1722 596 A1 discloses an electret condenser microphone includes: a substrate in which an opening is formed; an electret condenser connected to one face of the substrate so as to close the opening and having an acoustic hole and a cavity; a drive circuit element connected to the one face of the substrate; and a case mounted over the substrate so as to cover the electret condenser and the drive circuit element . Electric contact is established at a joint part between the electret condenser and the substrate. The acoustic hole communicates with an external space through the opening. The cavity and an internal region of the case serve as a back air chamber for the electret condenser.
US 20041170291 is directed to a mobile device with improved acoustic porting. The mobile device includes a housing that has at least one sound hole, a transducer for converting an electrical signal into an acoustical signal, and a grommet that engages the housing and the transducer to form an interior cavity. A passage acoustically couples the interior cavity with the interior of the housing. The transducer emits sound into the interior cavity. The sound travels from the interior cavity through the passage into the interior of the housing and then to the user's ear via the sound hole(s) in the housing. The passage may be any channel, tube, passageway, or pathway that allows an acoustical signal to travel from the interior cavity to the interior of the housing.; The transducer may also emit sound into the interior of the housing that mixes with the sound traveling from the interior cavity through the passage into the interior of the housing.
It is an object of the invention to provice a portable electronic device with an electret electro-acoustic transducer wherein the electret electro-acoustic transducer of the portable electronic devices has a greatly smaller thickness than the traditional dynamic loudspeakers.
For this purpose, the portable electronic device of the invention comprises the features of claim 1.
Preferred embodiments are characterized in the sub-claims.
The portable electret electro-acoustic transducer of the portable electronic devices has a greatly smaller thickness than the traditional dynamic loudspeakers, and, therefore, the available space inside the electronic device can be increased.
Embodiments of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.

FIG. 1: is a perspective view of the electronic device of the present invention.
FIG. 2a: is a cross-sectional view of the electronic device with an electro-acoustic transducer, wherein the back cover is separated from the body of the electronic device.
FIG. 2b: is a cross-sectional view of the electronic device with an electro-acoustic transducer, wherein the back cover is attached to the body of the electronic device.
FIG. 3a: is a cross-sectional view of the electronic device with an electro-acoustic transducer, wherein the back cover is separated from the body of the electronic device.
FIG. 3b: is a cross-sectional view of the electronic device with an electro-acoustic transducer, wherein the back cover is attached to the body of the electronic device.
FIG, 4a: is a cross-sectional view of the electronic device with an electro-acoustic transducer, wherein the back cover is separated from the body of the electronic device.
FIG. 4b: is a cross-sectional view of the electronic device with an electro-acoustic transducer, wherein the back cover is attached to the body of the electronic device.
FIG. 5a: is a cross-sectional view of the electronic device with an electro-acoustic transducer according to an embodiment of the present invention, wherein the back cover is separated from the body of the electronic device.
FIG. 5b: is a cross-sectional view of the electronic device with an electro-acoustic transducer according to the embodiment of the present invention, wherein the back cover is attached to the body of the electronic device.

Referring toFIGS.1,2a and 2b, theelectronic device 100 with an electro-acoustic transducer includes ahousing 110 having a plurality ofopenings 114 penetrating between theinner surface 112 and theouter surface 118 thereof. An electro-acoustic transducer 180 is disposed on theinner surface 112 of thehousing 110. The electro-acoustic transducer 180 includes anelectret diaphragm 120 positioned on theinner surface 112 of thehousing 110. In addition, theelectret diaphragm 120 includes afilm body 122 and anelectrode layer 124 formed on the lower surface of thefilm body 122. Thefilm body 122 is made of dielectric material and has static charges. Thefilm body 122 has a thickness of 7 to 25 µm and theelectrode layer 124 has a thickness of 0.05 to 1 µm. Aconductive plate 140 functioning as an electrode is stacked on the upper surface of thefilm body 122 and has a plurality ofopenings 142 corresponding to theopenings 114. Theconductive plate 140 has a thickness of 0.1 to 1 mm, and an aperture ratio of theopenings 142 on theconductive plate 140 is greater than 20%. Furthermore, at least onespacer 150 is disposed between theelectret diaphragm 120 and theconductive plate 140 to keep a predetermined distance between theelectret diaphragm 120 and theconductive plate 140. Thespacer 150 is spaced 5 to 20 mm apart from each other and has a height of 100 to 400 µm.
In order to make thefilm body 122 carry static charges, thefilm body 122 originally without static charges carried thereon is required to be subjected to a polarizing process. For example, a corona charging process can be used to polarize thefilm body 122 to generate static charges therein and thereon after theelectrode layer 124 is formed on thefilm body 122. The material suitable for thefilm body 122 can be fluorinated ethylene propylene (FEP), Polytetrafluoroethene (PTFE), Polyvinylidene Fluoride (PVDF), silicon dioxide (SiO2) or other fluoride polymers. Furthermore, the edge of theelectret diaphragm 120 is required to be fixed to prevent theelectret diaphragm 120 from movement. To have the electro-acoustic transducer 180 of the present embodiment work, electrical signals having the same phase and opposite phase with the original sound signal, i.e. differential signals have to be applied to theconductive plate 140 andelectrode layer 124, respectively so that theelectret diaphragm 120 is subject to the Coulomb forces from theconductive plate 140 andelectrode layer 124 to bring about a push-pull effect. The push-pull effect will cause theelectret diaphragm 120 to vibrate in accordance with the electrical signals. The vibration of theelectret diaphragm 120 pushes the air to make sounds. The sounds can travel through theopenings 114 to the outside of thehousing 110 thereby a user can hear the sounds.
In addition, since the sounds made by theelectret diaphragm 120 can also travel through theopenings 142 of theconductive plate 140 and be bounced back by the elements above theconductive plate 140, the upper surface of theconductive plate 140 is spaced a predetermined distance, said more that 1 mm apart from the elements above theconductive plate 140 to prevent the echo from degrading the performance of the electro-acoustic transducer 180. Alternatively, asound absorbing layer 160 made of, such as glass fiber, sponge or non-woven can be attached to the upper surface of theconductive plate 140 to absorb the sounds traveling through theopenings 142. Thesound absorbing layer 160 has a thickness of 1 to 5 mm. Moreover, at least onespacer 170 with a thickness of 30 to 50 µm and corresponding to thespacer 150 is positioned between theelectrode layer 124 and theinner surface 112 of thehousing 110 to keep theelectrode layer 124 from contact with thehousing 110. Furthermore, thespacer 150 can be made of adhesive material, such as double-sided tape to attach theconductive plate 140 andfilm body 122 together.
Referring toFIGS. 1,3a and 3b, theelectronic device 200 with an electro-acoustic transducer has all the elements of theelectronic device 100, that is, thehousing 110 and theelectret diaphragm 120,conductive plate 140,spacers 150, 170 and soundabsorbing layer 160 of the electro-acoustic transducer 180. In addition to the above elements, the electro-acoustic transducer 280 of theelectronic device 200 further includes aconductive plate 240 functioning as an electrode that is stacked on theconductive plate 140 and has a plurality ofopenings 242 corresponding to theopenings 142 of theconductive plate 140. Theconductive plate 240 has a thickness of 0.1 to 1 mm. Anisolation layer 290 made of porous air-permeable membrane has a thickness of 20 to 200 µm and is disposed between theconductive plates 140 and 240. In addition, anelectret diaphragm 220 is positioned on theconductive plate 240 and includes afilm body 222 and anelectrode layer 224 formed on the upper surface of thefilm body 222, wherein thesound absorbing layer 160 is attached to theelectrode layer 224. Thefilm body 222 is made of dielectric material and has static charges. Thefilm body 222 has a thickness of 7 to 25 µm and theelectrode layer 224 has a thickness of 0.05 to 1 µm. Furthermore, at least onespacer 250 made of, such as adhesive material and corresponding to thespacer 150 is disposed between theelectret diaphragm 220 and theconductive plate 240 to keep a predetermined distance between theelectret diaphragm 220 and theconductive plate 240. Thespacer 250 has a height of 100 to 400 µm.
Similarly, thefilm body 222 originally without static charges carried thereon is also required to be polarized in order to generate static charges therein and thereon. The material suitable for thefilm body 222 can be FEP, PTFE, PVDF, silicon dioxide or other fluoride polymers. Furthermore, the edge of theelectret diaphragm 220 is also required to be fixed to prevent theelectret diaphragm 220 from movement. To have the electro-acoustic transducer 280 of the present embodiment work, a first electrical signal having the same phase with the original sound signal have to be applied to theconductive plate 140 and theelectrode layer 224 and a second electrical signal having opposite phase with the original sound signal is applied to theelectrode layer 124 and theconductive plate 240. In this manner, theelectret diaphragms 120 and 220 will be subject to the Coulomb forces from theconductive plates 140, 240 andelectrode layers 124, 224 to vibrate and make sounds in accordance with the first and second electrical signals. The sounds made by theelectret diaphragm 220 can travel through theisolation layer 290 andopenings 114 to the outside of thehousing 110. The electro-acoustic transducer 280 with double electret diaphragms can make double (3dB) sounds than the electro-acoustic transducer 180 with only a single electret diaphragm.
Referring toFIGS. 1,4a and 4b, theelectronic device 300 with an electro-acoustic transducer includes ahousing 110 and an electro-acoustic transducer 380 disposed on theinner surface 112 of thehousing 110. The electro-acoustic transducer 380 includes aconductive plate 340 functioning as an electrode disposed on theinner surface 112 of thehousing 110. Theconductive plate 340 has a plurality ofopenings 342 corresponding to theopenings 114. Anelectret diaphragm 320 is stacked on theconductive plate 340 and includes afilm body 322 and anelectrode layer 324 formed on the upper surface of thefilm body 322. Thefilm body 322 is made of dielectric material and has static charges. Thefilm body 322 has a thickness of 7 to 25 µm and theelectrode layer 324 has a thickness of 0.05 to 1 µm, In addition, at least onespacer 350 made of, such as adhesive material is disposed between theelectret diaphragm 320 and theconductive plate 340 to keep a predetermined distance between theelectret diaphragm 320 and theconductive plate 340. Thespacer 350 is spaced 5 to 20 mm apart from each other and has a height of 100 to 400 µm. Moreover, at least onespacer 370 made of, such as adhesive material and corresponding to thespacer 350 is positioned between theconductive plate 340 and theinner surface 112 of thehousing 110 to keep theconductive plate 340 from contact with thehousing 110. Thespacer 370 has a thickness of 30 to 50 µm. Furthermore, asound absorbing layer 360 is attached to theelectrode layer 324 to prevent the echo from degrading the performance of the electro-acoustic transducer 380.
Similarly, thefilm body 322 originally without static charges carried thereon is also required to be polarized in order to generate static charges therein and thereon. The material suitable for thefilm body 322 can be FEP, PTFE, PVDF, silicon dioxide or other fluoride polymers. Furthermore, the edge of theelectret diaphragm 320 is also required to be fixed to prevent theelectret diaphragm 320 from movement. To have the electro-acoustic transducer 380 of the present embodiment work, an electrical signal has to be applied to theconductive plate 340 andelectrode layer 324 thereby theelectret diaphragm 320 can vibrate to make sounds in accordance with the electrical signal.
Referring toFIGS. 1,5a and 5b, theelectronic device 400 with an electro-acoustic transducer according to an embodiment of the present invention is substantially the same as theelectronic device 300 ofFIG. 4, where identical reference numerals have been used when designating substantially identically elements that are common to the figures. Any further illustrations of the identical elements are omitted herein. The difference between them is in that the electro-acoustic transducer 480 of theelectronic device 400 includes aconductive layer 440 coated on theinner surface 112 of thehousing 110 to replace theconductive plate 340 and does not have thespacer 370. Similarly, to have the electro-acoustic transducer 480 of the present embodiment work, an electrical signal has to be applied to theconductive layer 440 andelectrode layer 324 thereby theelectret diaphragm 320 can vibrate to make sounds in accordance with the electrical signal.
The electro-acoustic transducers 180, 280, 380 and 480 of theelectronic devices 100, 200, 300 and 400 are disposed on thehousing 110 and thehousing 110 can be a front cover, side cover or back cover of theelectronic devices 100, 200, 300 and 400. It will be appreciated that the electro-acoustic transducers 180, 280, 380 and 480 have to be electrically connected to other elements, such as circuit boards in theelectronic devices 100, 200, 300 and 400 in order to work. Referring back toFIGS. 2a, 2b,3a, 3b,4a, 4b,5a and 5b, when the electro-acoustic transducers 180, 280, 380 and 480 are mounted on a detachable back covers 110,electrical terminals 116a are disposed on theinner surfaces 112 of the back covers 110 to electrically connect to theconductive plates 140, 340 andconductive layer 440, and theelectrical terminals 116b disposed on theinner surfaces 112 of the back covers 110 are electrically connected to the electrode layers 124 and 324. In addition, theelectrical terminals 119a and 119b disposed on theinner surface 112 of theback cover 110 of theelectronic device 200 are electrically connected to theconductive plate 240 andelectrode layer 224 of the electro-acoustic transducer 280, respectively. As shown inFIGS. 2b,3b,4b and5b, when theback cover 110 are attached to the body of theelectronic devices 100, 200, 300 and 400, theelectrical terminals 116a and 116b are respectively brought into electrical contact with theelectrical terminals 197a and 197b on thecircuit boards 195 of theelectronic devices 100, 200, 300 and 400, and theelectrical terminals 119a and 119b (shown inFIG. 3b) are respectively brought into electrical contact with theelectrical terminals 198a and 198b on thecircuit board 195 of theelectronic device 200. In this way, the electrical signals can be applied to theconductive plates 140, 240, 340,conductive layer 440 andelectrode layers 124, 224, 324 thereby theelectret diaphragms 120, 220, 320 can vibrate to make sounds in accordance with the electrical signals.
According to the present invention, the spacers of the electro-acoustic transducers can be discrete spacers. However, it should be understood that the above discrete spacers can be replaced with the sheets formed with a plurality of openings thereon.
The electronic devices of the present invention can be portable electronic devices, such as mobile phones, personal digital assistants (PDAs) or laptop computers. Since the electro-acoustic transducers of the electronic devices according to the present invention have a greatly smaller thickness than the traditional dynamic loudspeakers, the available space inside the electronic device can be increased. In addition, the electro-acoustic transducers of the electronic devices according to the present invention can be mounted on the back covers. Therefore, the thickness of the electronic devices can be further reduced and the available space inside the electronic device can also be further increased. Moreover, since the electret surfaces of the electret diaphragms of the electro-acoustic transducers according to the first and second embodiments of the present invention face the insides of the electronic devices, the electret surfaces therefore get rid of the contamination of the dust and moisture to avoid the malfunction of the electret diaphragms.
Although a preferred embodiment of the invention has been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope of the invention as disclosed in the accompanying claims.

Claims

A portable electronic device, which is a mobile phone, a personal digital assistant (PDA) or a laptop computer, comprising:
a housing (110) having an inner surface (112), an outer surface (118) and a plurality of openings (114) penetrating between the inner surface (112) and the outer surface (118) thereof;
a circuit board (195); and
an electro-acoustic transducer (480) disposed on the inner surface (112) of the housing (110) and electrically connected to the circuit board (195), comprising:
a conductive layer (440) coated on the inner surface (112) of the housing (110);
an electret diaphragm (320) adapted to make sounds in accordance with an electrical signal, the electret diaphragm (320) being stacked on the conductive layer (440) and having a film body (322) and an electrode layer (324), wherein the film body (322) has static charges and the electrode layer (324) is formed on the film body (322); and
at least one spacer (350) disposed between the electret diaphragm (320) and the conductive layer (440) to keep a predetermined distance between the electret diaphragm (320) and the conductive layer (440),
the device further comprising:
a first electrical terminal (116a) and a second electrical terminal (116b) disposed on the inner surface (112) of the housing (110) for electrically connecting the electrical signal to the electrode layer (324) of the electret diaphragm (320) and the conductive layer (440), respectively;
a third electrical terminal (197a) and a fourth electrical terminal (197b) on the circuit board (195), wherein the first electrical terminal (116a) and the second electrical terminal (116b) are respectively electrically coupled with the third electrical terminal (197a) and the fourth electrical terminal (197b) whereby the electrical signal is applied to the electrode layer (324) of the electret diaphragm (320) and the conductive layer (440).
The portable electronic device as claimed in claim 1, wherein the electro-acoustic transducer (480) further comprises a sound absorbing layer (360) attached to the electrode layer (324) of the electret diaphragm (320).
The portable electronic device as claimed in claim 1, wherein the at least one spacer (350) is made of adhesive material.
The portable electronic device as claimed in claim 1, wherein the electrode layer (324) of the electret diaphragm (320) and the conductive layer (440) are electrically connected to the electrical signal.