WO2009038246A1

WO2009038246A1 - Ultra slim type acoustic transducer

Info

Publication number: WO2009038246A1
Application number: PCT/KR2007/005297
Authority: WO
Inventors: Seung-Kiu Jeong; Nam-Jin Jeung; Seung-Tae Kim
Original assignee: Em-Tech. Co., Ltd.
Priority date: 2007-09-19
Filing date: 2007-10-26
Publication date: 2009-03-26

Abstract

The present invention discloses a ultra slim type acoustic transducer which is reduced in thickness, wherein a magnetic closed circuit is constituted for acoustic transduction. The ultra slim type acoustic transducer includes a first magnet which is a vertical magnet (110), and a second magnet which is a horizontal magnet (120), and further includes a central yoke (130) coupled to a lower portion of the first magnet, and an outer yoke (140) coupled to a side surface of the second magnet (120) and also coupled to the central yoke (130), for defining an air gap with the first magnet. A part of a coil portion (150) is inserted into the air gap. The ultra slim type acoustic transducer includes a diaphragm (160) with the coil portion (150) mounted thereon, a protector (200) for protecting the diaphragm (160), and a frame (100) for supporting at least the outer yoke (140) and the protector (200).

Description

ULTRA SLIM TYPE ACOUSTIC TRANSDUCER

Technical Field

[1] The present invention relates to a ultra slim type acoustic transducer, and more particularly, to a ultra slim type acoustic transducer which is reduced in thickness, wherein a magnetic closed circuit is constituted for acoustic transduction. Background Art

[2] Generally, a speaker converts electrical energy into mechanical energy by a coil portion existing in an air gap according to Fleming's left hand rule stating that force is exerted on a conductor through which a current flows when the conductor is placed in a magnetic field. That is, when a current signal including a variety of frequencies is applied to a voice coil, the voice coil generates mechanical energy according to a current intensity and a frequency level. Therefore, a diaphragm attached to the coil portion is vibrated to subsequently generate a sound pressure of audible intensity.

[3] A magnetic circuit of the speaker is designed so that a magnetic flux can be interlinked with the coil portion existing in the air gap at a right angle by using a magnet (permanent magnet) and a top plate (or an upper plate) in a yoke made of ferrous metal. The coil portion is attached to the diaphragm, for generating exciting force in an up-down direction by an input signal. Accordingly, the diaphragm attached to and restricted by a frame is vibrated to generate a sound pressure. The diaphragm has various shapes of waves so as to obtain an excellent response characteristic and remove a buckling phenomenon in the up-down vibration. The shape of the diaphragm becomes a design variable greatly affecting a frequency characteristic.

[4] Fig. 1 is a cross-sectional view illustrating a conventional ultra slim type acoustic transducer, and Fig. 2 is a configuration view illustrating a magnetic closed circuit of the conventional ultra slim type acoustic transducer.

[5] Referring to Fig. 1, the conventional ultra slim type acoustic transducer includes a frame 1, a yoke 2 inserted and mounted in the frame 1, an inner ring magnet 3 and an outer ring magnet 4 for transferring magnetic force to the yoke 2 or receiving magnetic force from the yoke 2, magnetization directions of the inner ring magnet 3 and the outer ring magnet 4 being vertical directions so that the magnetic force can be transferred from the inner ring magnet 3 and the outer ring magnet 4 perpendicularly to a coil portion 7, the coil portion 7 partially inserted into an air gap between the inner ring magnet 3 and an inner ring top plate 5 and the outer ring magnet 4 and an outer ring top plate 6 for preventing leakage of a magnetic flux and perpendicularly transferring the magnetic flux to the coil portion 7, a diaphragm 8 with the coil portion 7 attached thereto, a protector 9 for protecting the diaphragm 8, and a sound emitting hole 10 formed in the protector 9.

[6] As illustrated in Figs. 1 and 2, the inner ring magnet 3 and the outer ring magnet 4 are magnetized on the yoke 2 in a vertical direction to transfer the magnetic force to the coil portion 7 at a right angle, and the inner ring top plate 5 and the outer ring top plate 6 are successively stacked on the magnets 3 and 4. The inner ring magnet 3 and the outer ring magnet 4 have opposite polarities N or S.

[7] The diaphragm 8 is coupled to a coupling projection upwardly formed at an upper rim of a horizontal surface of the frame 1. Electrical signals corresponding to sound or voice to be played back are applied to both ends of the coil portion 7 annularly wound up. The coil portion 7 is attached to a bottom surface of the diaphragm 8, reaching the space between the inner ring magnet 3 and the outer ring magnet 4. The protector 9 made of metal is coupled to the frame 1 at the upper portion of the diaphragm 8 so as to secure an up-down vibration motion space of the diaphragm 8 and protect the diaphragm 8.

[8] In the conventional ultra slim type acoustic transducer described above, when AC electrical signals corresponding to sound or voice to be played back are applied to both ends of the coil portion 7, the yoke 2, the magnets 3 and 4, and the top plates 5 and 6 constitute a magnetic closed circuit. The magnetic flux is interlinked with the coil portion 7, and the diaphragm 8 with the coil portion 7 attached thereto is vibrated with the coil portion 7 to subsequently generate a sound pressure of audible intensity.

[9] Ifcwever, as the conventional ultra slim type acoustic transducer has a lot of components, the stacked structure and the magnetic circuit thereof are thick, which increases the unit cost of production. If the inner ring magnet 3, the outer ring magnet 4, and the inner ring top plate 5 and the outer ring top plate 6 stacked on the magnets 3 and 4 are removed to reduce the thickness of the conventional ultra slim type acoustic transducer, the sound pressure falls due to reduction of the magnetic flux interlinked with the coil portion 7, which degrades the performance and reliability of the conventional ultra slim type acoustic transducer. Disclosure of Invention Technical Problem

[10] Accordingly, the present invention is conceived to solve the foregoing problems in the prior art. An object of the present invention is to provide a ultra slim type acoustic transducer which can minimize a vertical direction size by reducing components.

[11] Another object of the present invention is to provide a ultra slim type acoustic transducer which can prevent reduction of magnetic flux interlinkage by increasing a volume of a magnet. Technical Solution

[12] In order to achieve the above-described objects, a ultra slim type acoustic transducer includes a first magnet which is a vertical magnet, and a second magnet which is a horizontal magnet formed with a predetermined air gap from the first magnet, a central yoke being coupled to a lower portion of the first magnet, an outer yoke being coupled to a side surface of the second magnet and also coupled to the central yoke. The ultra slim type acoustic transducer further includes a coil portion at least partially inserted into the air gap, a diaphragm with the coil portion mounted thereon, a protector for protecting the diaphragm, and a frame for supporting at least the outer yoke and the protector.

[13] A first magnetic path is formed in the air gap between the first magnet and the second magnet, and a second magnetic path is formed in the central yoke and the outer yoke between the second magnet and the first magnet, a magnetic closed circuit being constituted by the first and second magnets, the central yoke and the outer yoke.

[14] In another aspect of the present invention, a ultra slim type acoustic transducer includes: a yoke provided with a central portion, and an outer circumference portion defining spaces symmetrical around the central portion; a first magnet which is a vertical magnet coupled to an upper part of the central portion; a second magnet which is a horizontal magnet defining an air gap with the first magnet in the space and being coupled to an inner surface of the outer circumference portion; a coil portion partially inserted into the air gap; a diaphragm with the coil portion mounted thereon; a protector for protecting the diaphragm; and a frame for supporting at least the yoke and the protector.

[15] A first magnetic path is formed in the air gap between the second magnet in the space and the first magnet, and a second magnetic path is formed in the central portion and the outer circumference portion between the first magnet and the second magnet, a magnetic closed circuit being constituted by the first and second magnets and the yoke.

[16] In yet another aspect of the present invention, a ultra slim type acoustic transd-cer includes: a first magnetic path formed between a first magnet and a second magnet having a magnetization direction perpendicular to that of the first magnet and defining an air gap with the first magnet; a coil portion at least partially inserted into the air gap; a diaphragm with the coil portion mounted thereon; and a second magnetic path formed by a path forming portion between the second magnet and the first magnet, a magnetic closed circuit being constituted by the first magnet, the first magnetic path, the second magnet and the second magnetic path.

Advantageous Effects [17] According to the present invention, the ultra slim type acoustic transducer can amplify an output level of playback sound or voice by maximizing the volumes of the first and second magnets, by decreasing lengths of short axis portions of the first and second magnets and increasing lengths of long axis portions thereof. [18] In addition, according to the present invention, the ultra slim type acoustic transducer can attain high sound quality with a minimim number of components.

Brief Description of the Drawings [19] Fig. 1 is a cross-sectional view illustrating a conventional ultra slim type acoustic transducer;

[20] Fig. 2 is a configuration view illustrating a magnetic closed circuit of the conventional ultra slim type acoustic transducer; [21] Fig. 3 is an exploded perspective view illustrating a ultra slim type acoustic transducer according to a first embodiment of the present invention; [22] Fig. 4 is an inner assembly view illustrating a part of the ultra slim type acoustic transducer according to the first embodiment of the present invention; [23] Fig. 5 is a short axis cross-sectional view illustrating the ultra slim type acoustic transducer according to the first embodiment of the present invention; [24] Fig. 6 is a long axis cross-sectional view illustrating the ultra slim type acoustic transducer according to the first embodiment of the present invention; [25] Fig. 7 is a configuration view illustrating a part of a magnetic closed circuit of the ultra slim type acoustic transducer according to the first embodiment of the present invention; [26] Fig. 8 is a front perspective view illustrating the ultra slim type acoustic transducer according to the first embodiment of the present invention; [27] Fig. 9 is a rear perspective view illustrating the ultra slim type acoustic transducer according to the first embodiment of the present invention; [28] Fig. 10 is a perspective view illustrating a part of a ultra slim type acoustic transducer according to a second embodiment of the present invention; [29] Fig. 11 is a perspective view illustrating a part of a ultra slim type acoustic transducer according to a third embodiment of the present invention;

[30] Fig. 12 is a cross-sectional view illustrating a part of the ultra slim type acoustic transducer according to the third embodiment of the present invention; and

[31] Fig. 13 is a perspective view illustrating a part of a ultra slim type acoustic transducer according to a fourth embodiment of the present invention. Best Mode for Carrying Out the Invention

[32] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[33] Fig. 3 is an exploded perspective view illustrating a ultra slim type acoustic transducer according to a first embodiment of the present invention, and Fig. 4 is an inner assembly view illustrating a part of the ultra slim type acoustic transducer according to the first embodiment of the present invention.

[34] As illustrated in Figs. 3 and 4, the ultra slim type acoustic transducer according to the first embodiment of the present invention includes a frame 100, a first magnet 110, a second magnet 120, a central yoke 130, an outer yoke 140, a coil portion 150, a diaphragm 160, a terminal 170 and a protector 200. In Fig. 4, A-A' indicates a long axis of the ultra slim type acoustic transducer, and B-B' indicates a short axis thereof.

[35] The first magnet 110 for transferring magnetic force through a sound emitting hole

201 is fixedly adhered to an upper portion of the central yoke 130. The central yoke 130 with the first magnet 110 fixedly mounted thereon is coupled to a lower portion of the outer yoke 140 inserted into the frame 100. Two second magnets 120 are provided at both sides of the first magnet 110. Each second magnet 120 is fixedly mounted on an inner surface of the outer yoke 140, defining a predetermined air gap 101 with the first magnet 110.

[36] A part of the coil portion 150 is inserted into the air gap 101 between the first magnet 110 and the second magnet 120. The diaphragm 160 coupled to the coil portion 150 is fixed by the protector 200 and the frame 100, and the terminal 170 is inserted and mounted in the frame 100.

[37] When an electrical signal is inputted, the first magnet 110 and the second magnets

120 generate a magnetic field. The coil portion 150 repeats motion due to the magnetic field generated by the magnets 110 and 120, so that the attraction and repulsion repeatedly occur. The diaphragm 160 is vibrated with the vibration of the coil portion 150 to subsequently generate a sound pressure. The terminal 170 provides electrical connections to the components, the protector 200 protects the diaphragm 160 from an external impact, and the frame 100 supports the outer yoke 140 or the terminal 170 and the protector 200, keeping an up-down vibration space of the diaphragm 160.

[38] Fig. 5 is a short axis cross-sectional view illustrating the ultra slim type acoustic transducer according to the first embodiment of the present invention, Fig. 6 is a long axis cross-sectional view illustrating the ultra slim type acoustic transducer according to the first embodiment of the present invention, and Fig. 7 is a configuration view illustrating a part of a magnetic closed circuit of the ultra slim type acoustic transducer according to the first embodiment of the present invention. Particularly, Fig. 5 is a cross-sectional view taken along line A-A' Gong axis) of Fig. 4, and Fig. 6 is a cross- sectional view taken along line B-B' (short axis) of Fig. 4.

[39] Referring to Figs. 5, 6 and 7, the second magnets 120 closely adhered to the inner surface of the outer yoke 140 inserted into the frame 100 are magnetized in a horizontal direction with N or S polarity. The first magnet 110 coupled to the upper portion of the central yoke 130 is magnetized in a vertical direction, and has a polarity perpendicularly symmetrical to that of the second magnets 120, namely, S or N polarity.

[40] The magnetic flux interlinkage is facilitated by decreasing short axis lengths of the first magnet 110 and the second magnets 120 and increasing long axis lengths thereof. In addition, the first and second magnets 110 and 120 are placed to be level with each other. As a result, the ultra slim type acoustic transducer according to the present invention minimizes the vertical direction size by simplifying the components without reducing the magnetic flux interlinkage.

[41] The magnetic closed circuit of the ultra slim type acoustic transducer is constituted by the first and second magnets 110 and 120, the central yoke 130 and the outer yoke 140. A magnetic closed circuit in which the second magnets 120 have N polarity and the first magnet 110 has S polarity is composed of a first magnetic path connected from the second magnet 120 which is a horizontal magnet to the top surface of the first magnet 110 which is a vertical magnet via the air gap 101, the coil portion 150 positioned in the sound emitting hole 201 being interlinked with a magnetic flux, and a second magnetic path connected from the first magnet 110 to the second magnet 120 via the central yoke 130 and the outer yoke 140 coupled to the central yoke 130.

[42] A magnetic closed circuit in which the first magnet 110 has N polarity and the second magnets 120 have S polarity is composed of a first magnetic path connected from the upper portion of the first magnet 110 to the second magnet 120 via the air gap 101, and a second magnetic path connected from the second magnet 120 to the first magnet 110 via the outer yoke 140_..

[43] In more detail, when the second magnets 120 have N polarity and the first magnet

110 has S polarity, as seen on the short axis surface, the left parts of the second magnets 120 which are horizontal magnets have S polarity, the right parts thereof have N polarity, the lower part of the first magnet 110 which is a vertical magnet perpendicularly symmetrical to the second magnets 120 has N polarity, and the upper part thereof has S polarity. Therefore, a magnetic flux moves from the left to right side in the second magnets 120, and from the top to bottom in the first magnet 110.

[44] In the first magnetic path, the magnetic flux flows from N polarity formed at the right part of the second magnet 120 to S polarity formed at the top surface of the first magnet 110 via the air gap 101. In the second magnetic path, the magnetic flux flows from S polarity formed at the upper part of the first magnet 110 to N polarity formed at the lower part thereof, passes through the central yoke 130 fixedly coupled to the first magnet 110 and the outer yoke 140, and flows into S polarity formed at the left part of the second magnet 120. The first and second magnetic paths constitute the magnetic closed circuit. In this magnetic closed circuit, the magnetic force is interlinked even with a curved part 152 of the coil portion 150 which is relatively weak, so that a magnetic flux density is uniform.

[45] Fig. 8 is a front perspective view illustrating the ultra slim type acoustic transdcer according to the first embodiment of the present invention, and Fig. 9 is a rear perspective view illustrating the ultra slim type acoustic transducer according to the first embodiment of the present invention.

[46] As shown in Figs. 8 and 9, the second magnets (120; refer to Fig. 4) are coupled in a pair to the inner surface of the outer yoke (140; refer to Fig. 4) inserted into the frame 100. The central yoke 130 fixedly coupled to the first magnet 110 to be spaced apart from the second magnets (120; refer to Fig. 4) by the air gap 101 is fixedly coupled to the bottom surface of the outer yoke (140; refer to Fig. 4). The air gap 101 of predetermined size existing between the central yoke 130 completely adhered to the bottom surface of the outer yoke (140; refer to Fig. 4) and the second magnets (120; refer to Fig. 4) serves as an insertion space of the coil portion (150; refer to Fig. 5) and a rear sound emitting hole. The protector 200 made of metal secures the vibration motion space of the diaphragm 160 and protects the other components including the frame 100.

[47] In the following description, same drawing reference numerals are used for the same elements as those of the first embodiment of the present invention. [48] Fig. 10 is a perspective view illustrating a part of a ultra slim type acoustic transducer according to a second embodiment of the present invention. A first magnet 110 magnetized in a vertical direction is attached to a central yoke 130, and a pair of second magnets 120 magnetized in a horizontal direction are attached to an inner surface of an outer yoke 140 inserted into a frame (100; refer to Fig. 4). The central yoke 130 with the first magnet 110 mounted thereon is attached and coupled to a lower portion of the outer yoke 140. The above and other components of the second embodiment are identical to those of the first embodiment except a top plate 190 further provided at an upper portion of the first magnet 110.

[49] The top plate 190 contains a magnetic material to transfer magnetic force to a coil portion (150; refer to Fig. 5). The top plate 190 is formed in the same shape as that of the top surface of the first magnet 110 to prevent external transfer of the magnetic force. Meanwhile, the horizontal area of the ultra slim type acoustic transducer does not change. As the top plate 190 is formed in a space between a diaphragm and the first magnet 110, the ultra slim type acoustic transducer can improve the magnetic flux interlinkage without increasing the vertical direction size.

[50] In the second embodiment, a magnetic closed circuit in which the second magnets

120 have N polarity and the first magnet 110 has S polarity will be explained. As seen on a short axis surface, the left parts of the second magnets 120 have S polarity, the right parts thereof have N polarity, the upper part of the first magnet 110 has S polarity, and the lower part thereof has N polarity.

[51] Accordingly, in a first magnetic path, when interlinked with the coil portion 150, a magnetic flux flows from N polarity formed at the right part of the second magnet 120 to S polarity of the first magnet 110 and the top plate 190 formed on the first magnet 110 via the air gap 101. In a second magnetic path, the magnetic flux starts from the top plate 190, flows from S polarity formed at the upper part of the first magnet 110 to N polarity formed at the lower part thereof, passes through the central yoke 130 and the outer yoke 140, and flows into S polarity formed at the left part of the second magnet 120. The first and second magnetic paths constitute the magnetic closed circuit. In this magnetic closed circuit, the magnetic force is interlinked even with a curved part 152 of the coil portion 150 which is relatively weak, so that a magnetic flux density is uniform.

[52] Fig. 11 is a perspective view illustrating a part of a ultra slim type acoustic transducer according to a third embodiment of the present invention, and Fig. 12 is a cross-sectional view illustrating a part of the ultra slim type acoustic transducer according to the third embodiment of the present invention.

[53] Fig. 12 is a cross-sectional view seen in C direction of Fig. 11. Components and coupling methods of the ultra slim type acoustic transducer of the third embodiment are identical to those of the first embodiment except a height of a first magnet 110. Concretely, the top surface of the first magnet 110 is positioned lower than top surfaces of second magnets 120.

[54] In the third embodiment, a magnetic closed circuit in which the second magnets

120 have N polarity and the first magnet 110 has S polarity will be explained. The left parts of the second magnets 120 have S polarity, the right parts thereof have N polarity, the upper part of the first magnet 110 has S polarity, and the lower part thereof has N polarity.

[55] Therefore, in a first magnetic path, when interlinked with a coil portion 150, a magnetic flux flows from N polarity formed at the right part of the second magnet 120 to S polarity formed at the upper part of the first magnet 110 via an air gap 101. As the upper part of the first magnet 110 is positioned relatively low, the magnetic flux flow is facilitated in the first magnetic path. In a second magnetic path, the magnetic flux flows from S polarity formed at the upper part of the first magnet 110 to N polarity formed at the lower part thereof, passes through a central yoke 130 and an outer yoke 140, and flows into S polarity formed at the left part of the second magnet 120. The first and second magnetic paths constitute the magnetic closed circuit. In this magnetic closed circuit, the magnetic force is interlinked even with a curved part 152 of the coil portion 150 which is relatively weak, so that a magnetic flux density is uniform.

[56] Fig. 13 is a perspective view illustrating a part of a ultra slim type acoustic transducer according to a fourth embodiment of the present invention. The ultra slim type acoustic transducer according to the fourth embodiment includes a frame 100, a first magnet 110, a second magnet 120, a yoke 130, a coil portion 150, a diaphragm 160, a terminal 170 and a protector 200.

[57] The yoke 130 is divided into a central portion 132 and an outer circumference portion 133. An upper portion of the central portion 132 fixedly couples to the first magnet 110, and the outer circumference portion 133 defines spaces 134 symmetrical around the central portion 132. The second magnet 120 is coupled in a pair to an inner surface of the outer circumference portion 133 in the spaces 134. The other components and coupling methods are identical to those of the first embodiment.

[58] In the fourth embodiment, a magnetic closed circuit in which the second magnets

[59] In a first magnetic path, a magnetic flux flows from N polarity formed at the right part of the second magnet 120 in the space 134 to S polarity formed at the upper part of the first magnet 110 via an air gap 101. In a second magnetic path, the magnetic flux flows from S polarity formed at the upper part of the first magnet 110 to N polarity formed at the lower part thereof, passes through the central portion 132 and the outer circumference portion 133 of the yoke 130, and flows into S polarity formed at the left part of the second magnet 120. This procedure is repeated. In this magnetic closed circuit, the magnetic force is interlinked even with a curved part 152 of the coil portion 150 which is relatively weak, so that a magnetic flux density is uniform.

[60] In a fifth embodiment of the present invention, a magnetic closed circuit is constituted by a first magnet, second magnets and a path forming portion. Components and coupling methods of the fifth embodiment are identical to those of the first embodiment except the path forming portion. The fifth embodiment will be described in detail without a drawing.

[61] In the fifth embodiment, a first magnetic path is formed in an air gap (101 ; refer to

Fig. 7) between a second magnet (120; refer to Fig. 7) and a first magnet (110; refer to Fig. 7), and a second magnetic path is formed by a path forming portion (not shown) connecting the first magnet (110; refer to Fig. 7) to the second magnet (120; refer to Fig. 7). The first and second magnetic paths constitute a magnetic closed circuit. In the magnetic closed circuit, magnetic force is interlinked even with a curved part (152; refer to Fig. 7) of a coil portion (150; refer to Fig. 7) which is relatively weak, so that a magnetic flux density is uniform. Industrial Applicability

[62] According to the present invention, in the ultra slim type acoustic transducer, the first magnet 110 which is a vertical magnet, the second magnets 120 which are horizontal magnets, the central yoke 130 and the outer yoke 140 constitute the magnetic closed circuit. As the volumes of the horizontal surfaces of the first and second magnets 110 and 120 are maximized, the output level of the playback sound or voice is amplified, but the whole number of components is reάced. Therefore, the ultra slim type acoustic transducer can attain high sound quality with a minimim number of components. In the prior art, the magnetic flux is transferred to the coil portion 150 at a right angle. According to the present invention, the outer yoke 140 and the central yoke 130 are provided to uniformize the magnetic flux density. [63] Although the preferred embodiments of the present invention have been described, it is understood that the present invention should not be limited to these preferred embodiments but various changes and modifications can be made by one skilled in the art within the spirit and scope of the present invention as hereinafter claimed.

Claims

[1] A ultra slim type acoustic transducer, comprising: a first magnet which is a vertical magnet; a second magnet which is a horizontal magnet formed with a predetermined air gap from the first magnet; a central yoke coupled to a lower portion of the first magnet; an outer yoke coupled to a side surface of the second magnet and also coupled to the central yoke; a coil portion at least partially inserted into the air gap; a diaphragm with the coil portion mounted thereon; a protector for protecting the diaphragm; and a frame for supporting at least the outer yoke and the protector.

[2] The ultra slim type acoustic transducer of claim 1, wherein a first magnetic path is formed in the air gap between the first magnet and the second magnet, and a second magnetic path is formed in the central yoke and the outer yoke between the second magnet and the first magnet, a magnetic closed circuit being constituted by the first and second magnets, the central yoke and the outer yoke.

[3] The ultra slim type acoustic transducer of claim 2, wherein the first magnetic path is formed between the second magnet and the first magnet.

[4] The ultra slim type acoustic transducer of claim 1, wherein the second magnet is formed in a pair on both side surfaces of the first magnet.

[5] The ultra slim type acoustic transducer of any one of claims 1 to 4, wherein a top plate is provided at an upper portion of the first magnet.

[6] The ultra slim type acoustic transducer of claim 5, wherein the first magnetic path is formed between the second magnet and the top plate.

[7] The ultra slim type acoustic transducer of any one of claims 1 to 4, wherein the top surface of the first magnet is positioned lower than the top surface of the second magnet.

[8] A ultra slim type acoustic transducer, comprising: a yoke provided with a central portion, and an outer circumference portion defining spaces symmetrical around the central portion; a first magnet which is a vertical magnet coupled to an upper part of the central portion; a second magnet which is a horizontal magnet defining an air gap with the first magnet in the space and being coupled to an inner surface of the outer circumference portion; a coil portion partially inserted into the air gap; a diaphragm with the coil portion mounted thereon; a protector for protecting the diaphragm; and a frame for supporting at least the yoke and the protector.

[9] The ultra slim type acoustic transducer of claim 8, wherein a first magnetic path is formed in the air gap between the second magnet in the space and the first magnet, and a second magnetic path is formed in the central portion and the outer circumference portion between the first magnet and the second magnet, a magnetic closed circuit being constituted by the first and second magnets and the yoke.

[10] The ultra slim type acoustic transducer of claim 9, wherein the first magnetic path is formed between the second magnet in the space and the first magnet.

[11] The ultra slim type acoustic transducer of claim 8, wherein the second magnet is formed in a pair on both side surfaces of the first magnet.

[12] The ultra slim type acoustic transducer of any one of claims 8 to 11, wherein a top plate is provided at an upper portion of the first magnet.

[13] The ultra slim type acoustic transducer of claim 12, wherein the first magnetic path is formed between the second magnet in the space and the top plate.

[14] A ultra slim type acoustic transducer, comprising: a first magnetic path formed between a first magnet and a second magnet having a magnetization direction perpendicular to that of the first magnet and defining an air gap with the first magnet; a coil portion at least partially inserted into the air gap; a diaphragm with the coil portion mounted thereon; and a second magnetic path formed by a path forming portion between the second magnet and the first magnet, a magnetic closed circuit being constituted by the first magnet, the first magnetic path, the second magnet and the second magnetic path.

[15] The ultra slim type acoustic transducer of claim 14, wherein the first magnet is a vertical magnet and the second magnet is a horizontal magnet.

[16] The ultra slim type acoustic transducer of claim 14, wherein the path forming portion is connected between the first and second magnets.

[17] The ultra slim type acoustic transducer of any one of claims 14 to 16, wherein the first magnetic path is formed between the second magnet and the first magnet. [18] The ultra slim type acoustic transducer of any one of claims 14 to 16, wherein a top plate is provided at an upper portion of the first magnet. [19] The ultra slim type acoustic transducer of claim 18, wherein the first magnetic path is formed between the second magnet and the top plate. [20] The ultra slim type acoustic transducer of claim 14, wherein the second magnet is formed in a pair at both sides of the first magnet.