WO2005055646A1

WO2005055646A1 - Voice coil plate and plane speaker including the same

Info

Publication number: WO2005055646A1
Application number: PCT/KR2004/003154
Authority: WO
Inventors: Joung-Youl Shin; Byung-Wan Han
Original assignee: Joung-Youl Shin; Byung-Wan Han
Priority date: 2003-12-05
Filing date: 2004-12-02
Publication date: 2005-06-16

Abstract

The present invention relates to a voice coil plate for a plate type speaker and a plate type speaker using the same. The voice coil plate of the present invention comprises a coil-attaching member with a hole bored therethrough; and a voice coil wound on a front surface of the coil-attaching member and wound on a rear surface of the coil-attaching member through connection via the hole. The plate type speaker of the present invention comprises the voice coil plate. According to the present invention, it is possible to prevent power lines from being broken due to vibration of the voice coil plate, to obtain higher output power through increase in the cross sectional area of the voice coil coupled to the voice coil plate, and to easily change the size of the plate type speaker.

Description

VOICE COIL PLATE AND PLANE SPEAKER INCLUDING THE SAME

Technical Field The present invention relates to a speaker, and more particularly, to a voice coil plate for a plane speaker and a plane speaker using the same.

Background Art A speaker is a device for radiating sound by generating compression-rarefaction waves in the air through transformation of electrical signals into vibration of a diaphragm. A diaphragm included in a speaker is vibrated due to Lorentz force caused by a current flowing through a voice coil placed in a magnetic field. At this time, a low-pitched sound is generated when the diaphragm is vibrated at a low frequency, whereas a high-pitched sound is generated when the diaphragm is vibrated at a high frequency. As the amplitude increases even at a frequency, the sound gets louder due to increased sound pressure. Fig. 1 is a front view of a conventional voice coil plate for a plate type speaker and Fig. 2 is a sectional view of the conventional voice coil plate, taken along line A-A of Fig. 1. The conventional voice coil plate employed in a speaker with a planar diaphragm, which is disclosed in Korean Patent No. 10-036014 filed by and issued to this applicant, comprises a coil- attaching member 10 and a voice coil 12, as shown in Fig. 1. The coil-attaching member 10 is made of non-magnetic material. The voice coil 12 that is in a wound state is attached to the surface of the coil-attaching member 10. The voice coil 12 comprises an outer power line 14, which is an outwardly exposed, outer distal end of the voice coil wound on the surface of the coil-attaching member 10, and an inner power line 16, which is an outwardly exposed, inner distal end of the voice coil wound on the surface of the coil-attaching member 10. As shown in Fig. 2 illustrating the section of the voice coil plate 8, the voice coil 12 is wound on only one side of the voice coil plate 10. Fig. 3 is an exploded perspective view showing the structure of a conventional plate type speaker. The conventional voice coil plate 8 for a plate type speaker shown in Figs. 1 and 2 is successively bent in the form of a series of cranks, has an upper end attached to a diaphragm 20, and is inserted into an insertion groove 32 defined in a plate 30 in which permanent magnets are installed. When an electric current flows through the voice coil 12, the voice coil plate 8 vibrates in a direction perpendicular to the diaphragm 20 and the diaphragm 20 attached to the voice coil plate 8 is then vibrated to radiate acoustic waves. However, in the conventional voice coil plate 8 shown in Figs. 1 to 3, the inner power line 16 is superimposed on the voice coil 12. Accordingly, the inner power line 16 may be readily broken due to friction thereof with the voice coil 12 upon vibration of the voice coil plate or friction thereof with an inner surface of the insertion groove 32 formed in the plate 30. hi case of manufacture of a plate type speaker with a large diaphragm 20, the coil-attaching member 10 should be lengthened and thus the voice coil 12 should be wound to be elongated, which results in difficulty in the manufacture thereof. Especially, there are problems in that the voice coil 12 wound on the voice coil plate 8 may be broken during the process of bending the voice coil plate, and the elongated voice coil 12 itself may act as a resistor. Further, since the voice coil 12 is provided only one side of the coil-attaching member 10 as shown in Figs. 1 and 2, the conventional voice coil plate 8 has limitation on increase in the amount of an electric current. Thus, there is a disadvantage in that the force of vertical vibration is also limited to below a predetermined value.

Disclosure

Technical Problem The present invention is conceived to solve the aforementioned problems. An object of the present invention is to provide a voice coil plate and a plate type speaker including the same, wherein the voice coil is prevented from being broken due to friction thereof with a magnetic body. Another object of the present invention is to provide a voice coil plate and a plate type speaker including the same, wherein the amount of an electric current flowing through the voice coil is increased.

Technical Solution According to an aspect of the present invention for achieving the object, there is provided a voice coil plate, comprising a coil-attaching member with a hole bored therethrough; and a voice coil wound on a front surface of the coil-attaching member and wound on a rear surface of the coil-attaching member through connection via the hole. The voice coil may comprise a front voice coil wound on and attached to the front surface of the coil-attaching member, a rear voice coil wound on and attached to the rear surface of the coil-attaching member, and a connection means formed in the hole to connect inner distal ends of the font and rear voice coils to each other. Alternatively, the voice coil may be wound on and attached to the front surface of the coil-attaching member and successively wound on and attached to the rear surface of the coil-attaching member after passing through the hole. The voice coil may be wound in the form of a track to have two horizontal portions at upper and lower ends thereof. According to another aspect of the present invention for achieving the object, there is provided a plate type speaker comprising the aforementioned voice coil plate. According to a further aspect of the present invention for achieving the object, there is provided a plate type speaker comprising, a base frame; at least one magnetic body coupled to the base frame such that opposite polarities are provided at adjacent lateral positions and are spaced apart by a predetermined distance from each other; a diaphragm; and two or more plane voice coil plates inserted into spaces between the opposite polarities of the magnetic body and connected to the diaphragm. The magnetic body may be formed to take the shape of a comb such that respective portions of the magnetic body with the opposite polarities have protrusions and depressions in a horizontal direction, and the protrusions may be inserted into the respective depressions with a predetermined gap therebetween. Alternatively, a plurality of magnetic bodies may be arranged in parallel. In the plate type speaker, the voice coil plate may comprise the aforementioned voice coil plate according to the aspect of the present invention. The magnetic body preferably has opposite polarities at upper and lower ends thereof. At this time, the magnetic body may comprise a permanent magnet with opposite polarities at upper and lower ends thereof; an upper plate coupled to the upper end of the permanent magnet; and a lower plate coupled to the lower end of the permanent magnet and coupled to a bottom surface of the base frame. The base frame may be formed with one or more openings bored through wall surfaces thereof. Openings bored through a bottom surface of the base frame among the openings may be formed at positions corresponding to lower ends of the voice coil plates.

Brief Description of Drawings Fig. 1 is a front view of a conventional voice coil plate for a plate type speaker. Fig. 2 is a sectional view of the conventional voice coil plate, taken along line A-A of Fig. 1. Fig. 3 is an exploded perspective view showing the structure of a conventional plate type speaker. Fig. 4 is a front view of a voice coil plate with a separable voice coil according to the present invention. Fig. 5 is a sectional view of the voice coil plate, taken along line B-B of Fig. 4. Fig. 6 is a front view of a voice coil plate with an integrated voice coil according to the present invention. Fig. 7 is a sectional view of the double-sided voice coil plate, taken along line C-C of Fig. 6. Fig. 8 is an exploded perspective view of a plate type speaker according to the present invention. Fig. 9 is a sectional view of the plate type speaker according to the present invention. Fig. 10 is an exploded perspective view of a plate type speaker including a plurality of coil plates according to the present invention. Fig. 11 is a sectional view of the plate type speaker including the plurality of coil plates shown in Fig. 10. Fig. 12 illustrates how a diaphragm of the plate type speaker shown in Fig. 10 operates. Fig. 13 is a circuit diagram applied to the plate type speaker shown in Fig. 10. Fig. 14 is an exploded perspective view of a plate type speaker with the integrated voice coil plate shown in Figs. 6 and 7 according to the present invention. Fig. 15 is a sectional view of the plate type speaker shown in Fig. 14. Best Mode for Carrying out the Invention Hereinafter, a voice coil plate and a plate type speaker including the same according to the present invention will be described in detail with reference to the accompanying drawings. Fig. 4 is a front view of a voice coil plate with a separable voice coil according to the present invention, and Fig. 5 is a sectional view of the voice coil plate, taken along line B-B of Fig. 4. As shown in Figs. 4 and 5, the voice coil plate 100 of the present invention comprises a coil-attaching member 106 with a connection hole 108 bored through the center thereof, and a voice coil 110. The voice coil 110 comprises a front voice coil 102 and a rear voice coil 104, which are wound on front and rear surfaces of the coil-attaching member 106, respectively. The voice coil 110 is constructed to receive electric power through a front power line 112 formed at an outer distal end of the front voice coil 102 and a rear power line 114 formed at an outer distal end of the rear voice coil 104. Inner distal ends of the front and rear voice coils 102 and 104 are arranged close to the connection hole 108 and are electrically connected to each other by means of a connection means 109 formed in the connection hole 108. At this time, as for the connection means 109, various connection methods including soldering can be employed so far as they allow an electric current to flow through the front and rear voice coils 102 and 104. Fig. 6 is a front view of a voice coil plate with an integrated voice coil according to the present invention, and Fig. 7 is a sectional view of the double-sided voice coil plate, taken along line C-C of Fig. 6. The voice coil plate 100 integrally formed with the voice coil 110 comprises a coil-attaching member 106 with a connection hole 108 bored through the center thereof, and a single voice coil 110. Since the single voice coil 110 is wound on a front surface of the coil-attaching member 106 and then successively wound on a rear surface of the coil-attaching member 106 after passing through the connection hole, such an additional connection means 109 shown in Figs. 4 and 5 is not required. As shown in Figs. 4 to 7, since the power lines 112 and 114 are not superimposed on the voice coil 110 wound on the coil- attaching member 106 in the voice coil plate 100 of the present invention, the power lines can be prevented from being broken due to friction that may be generated during vibration. Fig. 8 is an exploded perspective view of a plate type speaker according to the present invention. As shown in Fig. 8, the plate type speaker of the present invention comprises a concave base frame 400 with an open top portion, a pair of magnetic bodies 200 coupled to the base frame 400 such that opposite polarities are alternately arranged at a predetermined interval, a diaphragm 300 in the form of a flat panel coupled to the base frame 400, and a voice coil plate 100 which is inserted into spaces between the pair of magnetic bodies 200 and has an upper end coupled to the diaphragm 300. Each of the magnetic bodies 200 comprises a permanent magnet 210 with a size insertable into the base frame 400 and with opposite polarities at upper and lower ends thereof; an upper plate 220 that is in the form of a panel made of a magnetic material and having a size capable of covering the upper end of the permanent magnet 210 and is in close contact with the upper end of the permanent magnet 210; and a lower plate 230 that is formed in the same manner as the upper plate 220 in material and size and is in close contact with the lower end of the permanent magnet 210 while being connected to the bottom surface of the base frame 400. As shown in the figure, each of the magnetic bodies 210 is formed to take the shape of a comb with horizontal protrusions and depressions. The protrusions of one of the magnetic bodies are inserted into the depressions of the other thereof. At this time, it is also preferred that at least the upper and lower plates 220 and 230 of the magnetic body be formed to take the shape of a comb. The pair of magnetic bodies 200 are inserted into the base frame 400 with the open top portion. The diaphragm 300 is bonded to a top portion of the base frame 400 by means of a bonding member 310 that is provided at an outer periphery of the diaphragm 300. At this time, the diaphragm 300 is formed to have a size insertable into the base frame 400 through the opening at the top portion of the base frame 400, and the bonding member 310 is made of a flexible material. Accordingly, the diaphragm 300 can vertically vibrate without interference with the base frame 400. The base frame 400 is formed with at least one side opening 410 bored through a sidewall thereof and at least one bottom opening 420 bored through a bottom surface thereof so that air flows inward or outward when the top opening of the base frame is hermetically closed by the diaphragm 300. If a side opening 410 or a bottom opening 420 is not formed in the base frame 400, pressure within the base frame 400 increases when the diaphragm 300, which is connected to and hermetically closes the top portion of the base frame 400, vibrates vertically. Accordingly, the diaphragm 300 cannot normally vibrate only with an electric current and a magnetic flux and is affected by the air pressure within the base frame 400. However, if side openings 410 and bottom openings 420 are formed in the base frame 400 like the embodiment shown in Fig. 8, the pressure within the base frame 400 does not vary and thus the diaphragm 300 normally vibrates only with the current and the magnetic flux. Further, the bottom opening 420 is formed in a portion of the bottom surface of the base frame 400, which corresponds to the lower end of the voice coil plate 100 when the diaphragm 300 and the voice coil plate 100 are coupled to the base frame 400. Accordingly, since there is no contact between the voice coil plate 100 and the bottom surface of the base frame 400 even though the amplitude of the vertical vibration of the diaphragm 300 becomes larger, the diaphragm 300 can normally vibrate without external interference. The aforementioned plate type speaker can be easily manufactured using FPCB and the like, and electric circuits thereof can be simply configured since only one power line from each of the front and rear voice coils 102 and 104 is exposed. Fig. 9 is a sectional view of a plate type speaker according to the present invention. As shown in Fig. 9, when the voice coil 110 is coupled to the front and rear surfaces of the voice coil plate 100, the number of windings of the voice coil 110 increases twice as large as that of a conventional plate type speaker. Accordingly, the force for upwardly moving the voice coil plate 100 increases in proportion thereto. Further, even though the structure of the voice coil 110 coupled to the voice coil plate 100 is changed, the shapes and coupling structures of the magnetic bodies 200 and the diaphragm 300 coupled to the base frame 400 are the same as a conventional plate type speaker. Thus, detailed descriptions thereof will be omitted. Fig. 10 is an exploded perspective view of a plate type speaker including a plurality of coil plates according to the present invention. As shown in Fig. 10, the plate type speaker including the plurality of coil plates according to the present invention comprises a concave base frame 400 with an open top portion, a plurality of magnetic bodies 200a-200e for generating magnetic fields, a diaphragm 300 in the form of a flat panel coupled to the base frame 400, and coil plates lOOa-lOOd coupled to a lower end surface of the diaphragm 300 to be inserted into spaces between the magnetic bodies 200a-200e. Each of the magnetic bodies 200a-200e comprises a permanent magnet 210a-210e with a size insertable into the base frame 400 and with opposite polarities at upper and lower ends thereof; an upper plate 220a-220e that is in the form of a panel made of a magnetic material and having a size capable of covering the upper end of the permanent magnet 210a-210e and is in close contact with the upper end of the permanent magnet 210a-210e; and a lower plate 230a-230e that is formed in the same manner as the upper plate 220a-220e in material and size and is in close contact with the lower end of the permanent magnet 210a-210e while being coupled to a bottom surface of the base frame 400. Accordingly, the upper plate 220a-220e will have the same polarity as the upper end of the permanent magnet 210a-210e, and the lower plate 230a-230e will have the same polarity as the lower end of the permanent magnet 210a-210e. Further, the magnetic bodies 200a-200e are juxtaposed at a predetermined interval and connected to the base frame 400 in a state where adjacent magnetic bodies are inverted with respect to each other so that the polarities at the upper and lower ends thereof alternately appear. Thus, the respective magnetic bodies 200a-200e generate attractive forces for attracting adjacent other magnetic bodies. Although the magnetic bodies 200a-200e and the coil plates lOOa-lOOd are juxtaposed in this embodiment, the arrangement of the magnetic bodies 200a-200d and the coil plates lOOa-lOOd is not limited thereto but may be changed to various arrangements. The diaphragm 300 is made in the form of a flat panel with an area that allows the diaphragm 300 to be inserted into the base frame 400. A bonding member 310, which extends outwardly parallel to an upper end surface of the diaphragm 300, is provided at an outer periphery of the diaphragm 300 so that the bonding member can be connected to the top portion of the base frame 400. At this time, the bonding member 310 is made of a flexible material such as fabric or paper so that the diaphragm 300 can vertically vibrate. Further, the diaphragm 300 is formed to have an area smaller than that of the opening defined in the top portion of the base frame 400 so that the diaphragm 300 does not interfere with the base frame 400 even though the diaphragm 300 vibrates vertically. Since the material and structure of the diaphragm 300 are the same as a diaphragm employed in a conventional plate type speaker, a detailed description thereof will be omitted. Each of voice coils HOa-llOd is wound on and attached to one side of each of the coil plates lOOa-lOOd. At this time, the voice coils HOa-l lOd are wound in the form of tracks, and the coil plates lOOa-lOOd are arranged such that upper and lower ends of the voice coils HOa-l lOd are positioned between the upper plates 220a-220e and between the lower plates 230a-230e, respectively. Accordingly, since the coil plates lOOa-lOOd shown in Fig. 10 are arranged in the form of flat panels, a possibility that the voice coils HOa-l lOd may be broken due to bending of the coil plates is avoided. Moreover, if the size of the plate type speaker is intended to increase, the plate type speaker can enlarge only by increasing the number of the coil plates lOOa-lOOd without increasing the lengths of the coil plates lOOa-lOOd. Thus, there is no limitation on enlargement of the plate type speaker. Moreover, the base frame 400 of the embodiment shown in Fig. 10 is formed with one or more side openings 410 bored through sidewalls thereof and one or more bottom openings 420 bored through the bottom surface thereof in the same manner as the base frame 400 of the embodiment shown in Fig. 8, so that air flows inward or outward even through the top opening of the base frame is hermetically closed by the diaphragm 300. Fig. 11 is a longitudinal sectional view of the plate type speaker including the plurality of coil plates shown in Fig. 10. As shown in Fig. 11, this embodiment employs the four coil plates lOOa-lOOd and the five magnetic bodies 200a-200e. The first coil plate 100a to the fourth coil plate lOOd are inserted into spaces between the first magnetic body 200a to the fifth magnetic body 200e with fine gaps therebetween without contact thereof with the magnetic bodies 200a-200e. The diaphragm 300 is coupled not to interfere with the base frame 400 and the magnetic bodies 200a-200e upon vertical vibration of the diaphragm. Further, the bottom openings 420 are formed in portions of the bottom surface of the base frame 400, which correspond to lower ends of the coil plates lOOa-lOOd when the diaphragm 300 and the coil plates lOOa-lOOd are coupled to the base frame 400. Accordingly, since there is no contact between the coil plates lOOa-lOOd and the bottom surface of the base frame 400 even though the amplitude of the vertical vibration of the diaphragm 300 becomes larger, the diaphragm 300 can normally vibrate without external interference. Fig. 12 illustrates how the diaphragm of the plate type speaker employed in the present invention operates. As shown in Fig. 12, the second magnetic body 200b is coupled to the base frame 400 in a state where the upper and lower ends of the second magnetic body are inverted such that the polarities thereof at the ends are opposite to those of the first magnetic body 200a and the third magnetic body 200c. Further, electric current flows through the first coil 110a and the second voice coil 110b in opposite directions. hi this embodiment, the first to third magnetic bodies are arranged such that the upper end of the second magnetic body 200b has S-polarity and the upper ends of the first and third magnetic bodies 200a and 200c have N-polarity. The electric current flows clockwise in the first voice coil 110a but counterclockwise in the second voice coil 110b. In addition, the fourth and fifth magnetic bodies 200d and 200e, which are not shown in Fig. 12, are arranged such that the polarities thereof at the ends are opposite to those of adjacent ones of the magnetic bodies 200a-200e. Likewise, the electric current flows through the third and fourth coils 110c and HOd in directions opposite to those of adjacent ones of the voice coils lOOa-lOOd. Accordingly, a force is exerted on the diaphragm 300 shown in Fig. 12 according to the Fleming's left-hand rule so that the diaphragm moves upwardly. The diaphragm 300 vibrates with various amplitudes and periods according to the magnitude and direction of the electric current flowing through each of the voice coils HOa-l lOd. With such vibration, sound radiates outwardly. Fig. 13 is a circuit diagram applied to the plate type speaker of the present invention. In the plate type speaker of the present invention, the first voice coil 110a and the second 110b, and the third voice coil 110c and the fourth HOd are serially connected to each other, respectively, as shown in Fig. 13. The serially connected first and second voice coils 110a and 110b are connected in parallel to the serially connected third and fourth voice coils 110c and HOd. Accordingly, in the plate type speaker of the present invention, it is possible to change the directions of the electric current flowing through the respective voice coils 110a- 11 Od by means of such a serial-parallel circuit configuration. At this time, a method of controlling the directions of the electric current flowing through the respective voice coils HOa-l lOd is not limited to the circuit configuration shown in Fig. 13 but various methods can also be applied. The number of voice coil plates 100 is not limited to a specific number but can vary according to user's selection. Even in the embodiment shown in Fig. 8, the number of voice coil plates 100 is not limited to one. Two or more voice coil plates 100 may be bent and then installed. Such modifications of the inner structure of the plate type speaker can be readily understood by those skilled in the art. Fig. 14 is an exploded perspective view of a plate type speaker with the integrated voice coil plate shown in Figs. 6 and 7 according to the present invention, and Fig. 15 is a sectional view of the plate type speaker shown in Fig. 14. When the voice coil 110 is coupled to both sides of the voice coil plate 100 as shown in Figs. 14 and 15, the cross sectional area of the voice coil 110 increases as compared with the plate type speaker shown in Figs. 10 and 11, and thus, the force for upwardly moving the voice coil plate 100 also increases. Accordingly, since the plate type speaker including the voice coil plate 100 according to the present invention can obtain higher output power as compared with a conventional plate type speaker of the same size, it is possible to miniaturize the product. Further, the structure of the voice coil 110 coupled to the voice coil plate 100 can be modified into that shown in Figs. 4 and 5. The shapes and coupling structures of the magnetic body 200 and the diaphragm 300 coupled to the base frame 400 remain same as the plate type speaker shown in Figs. 14 and 15. Meanwhile, although four voice coil plates 100 shown in Figs. 6 and 7 are employed in Figs. 14 and 15, the number of voice coil plates 100 is not limited thereto. That is, only one voice coil plate 100 maybe employed. Although the present invention has been described in detail in connection with the preferred embodiments, the scope of the present invention is not limited to the specific embodiments but should be construed based on the appended claims. Further, it will be understood by those skilled in the art that various modifications and changes can be made without departing from the scope of the present invention. For example, the plate type speaker of the present invention may include only one magnetic body. In this case, the magnetic body may be constructed in various manners such that two different polarities of the magnetic body face each other with a predetermined gap therebetween. At this time, contrary to the illustrated embodiments, the polarities are horizontally arranged only in a single row. Further, only a portion of the voice coil plate, which corresponds to one of two ends of the voice coil plate where the voice coil is horizontally formed, may be inserted between the two facing opposite polarities of the magnetic body.

Industrial Applicability In the voice coil plate and the plate type speaker including the same according to the present invention, power lines are not superimposed on a voice coil so that they are prevented from being broken due to contact thereof with a magnetic body upon vibration of a voice coil plate. Further, since the voice coil is coupled to both sides of the voice coil plate, there is an advantage in that higher output power can be obtained through increase in the cross sectional area of the voice coil inserted between the magnetic bodies. Moreover, since voice coil plates are arranged in parallel in the plate type speaker of the present invention, the size of the product can be easily changed by changing the number of voice coil plates, hi addition, since a side opening and a bottom opening are formed in a base frame of the speaker, there is an advantage in that a diaphragm can normally vibrate only with an electric current and a magnetic flux without influence of air pressure within the base frame.

Claims

1. A voice coil plate, comprising: a coil-attaching member with a hole bored therethrough; and a voice coil wound on a front surface of the coil-attaching member and wound on a rear surface of the coil-attaching member through connection via the hole.

2. The voice coil plate as claimed in claim 1, wherein the voice coil comprises a front voice coil wound on and attached to the front surface of the coil-attaching member, a rear voice coil wound on and attached to the rear surface of the coil-attaching member, and a connection means formed in the hole to connect inner distal ends of the font and rear voice coils to each other.

3. The voice coil plate as claimed in claim 1, wherein the voice coil is wound on and attached to the front surface of the coil-attaching member and successively wound on and attached to the rear surface of the coil-attaching member after passing through the hole.

4. The voice coil plate as claimed in any one of claims 1 to 3, wherein the voice coil is wound in the form of a track to have two horizontal portions at upper and lower ends thereof.

5. A plate type speaker comprising the voice coil plate according to any one of claims 1 to 3.

6. A plate type speaker, comprising: a base frame; at least one magnetic body coupled to the base frame such that opposite polarities are provided at adjacent lateral positions and are spaced apart by a predetermined distance from each other; a diaphragm; and two or more plane voice coil plates inserted into spaces between the opposite polarities of the magnetic body and connected to the diaphragm.

7. The plate type speaker as claimed in claim 6, wherein the magnetic body is formed to take the shape of a comb such that respective portions of the magnetic body with the opposite polarities have protrusions and depressions in a horizontal direction, and the protrusions are inserted into the respective depressions with a predetermined gap therebetween.

8. The plate type speaker as claimed in claim 6, wherein a plurality of magnetic bodies are arranged in parallel.

9. The plate type speaker as claimed in any one of claims 6 to 8, wherein the voice coil plate comprises the voice coil plate according to claim 1.

10. The plate type speaker as claimed in any one of claims 6 to 8, wherein the magnetic body has opposite polarities at upper and lower ends thereof.

11. The plate type speaker as claimed in claim 10, wherein the magnetic body comprises: a permanent magnet with opposite polarities at upper and lower ends thereof; an upper plate coupled to the upper end of the permanent magnet; and a lower plate coupled to the lower end of the permanent magnet and coupled to a bottom surface of the base frame.

12. The plate type speaker as claimed in any one of claims 6 to 8, wherein the base frame is formed with one or more openings bored through wall surfaces thereof.

13. The plate type speaker as claimed in claim 12, wherein openings bored through a bottom surface of the base frame among the openings are formed at positions corresponding to lower ends of the voice coil plates.