JP2010206509A - Electromagnetic transducer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electromagnetic transducer whose depth is further reduced and in which the lower register can be played back with a flat diaphragm. <P>SOLUTION: The electromagnetic transducer includes: a yoke 23 made of a bar-shaped magnetic substance; a bar-shaped magnet 20 disposed to have a prescribed gap 25 between the magnet 20 and the yoke 23; a bar-shaped driving member 4, with a conductor pattern 15 formed on its surface, inserted into the gap 25; a plate-shaped diaphragm 10 fixed in the driving member 4; and a frame 30 for supporting the diaphragm 10. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electromagnetic transducer that includes a flat diaphragm driven by a rod-shaped magnetic circuit and reproduces sound from an audio signal.

Televisions that employ a flat panel display (FPD) are capable of being wall-mounted as a result of an increase in screen size and depth, and a reduction in installation space. Especially in televisions with a reduced depth, conventional cone-type speakers (hereinafter referred to as electromagnetic transducers) are too deep and cannot be incorporated into the TV housing, limiting the placement of electromagnetic transducers. Is coming out.
A conventional general cone type electromagnetic transducer includes, for example, a vibration system, a magnetic circuit, and a frame. The vibration system is formed by winding a diaphragm, a cap provided at the center of the diaphragm, an edge that supports the outer periphery of the diaphragm, and a conductor such as a metal wire around the cylinder, and is coupled to the inner periphery of the diaphragm. The voice coil is composed of a spider that supports the outer peripheral surface of the voice coil.
The magnetic circuit is composed of a magnet, a plate, and a pole piece. In addition, the frame supports and fixes the edges of the vibration system and the outer periphery of the spider, and is fixed to the magnetic circuit. The power supply terminal and lead wires extending from the terminal to the voice coil are fixed to the frame.

  The operation of the above electromagnetic transducer is as follows. When an audio input signal is given to the terminal, it is supplied to the voice coil via the lead wire. In the conductor portion of the voice coil existing in the magnetic gap of the magnetic circuit, a driving force is generated by the signal based on the Fleming left-hand rule and vibrates. That is, the conductor portion of the voice coil vibrates by generating a driving force in the vertical direction, and generates sound waves from the vibration system coupled to the voice coil.

In the conventional electromagnetic transducer described above, the depth of the vibration system of the cone-shaped diaphragm having the depth and the cylindrical voice coil coupled to the diaphragm is required.
In addition, a magnetic circuit composed of a magnet, a plate, and a pole piece also requires a depth, and an electromagnetic transducer constituted by these has inevitably a large depth. For example, even a small-diameter full-band electromagnetic transducer used on a television has a depth of about 5 cm.

  Various flat plate type electromagnetic transducers and planar type electromagnetic transducers have been proposed for electromagnetic transducers having such depths, and some have been commercialized (see Non-Patent Document 1). According to Non-Patent Document 1, as a general structure of the flat electromagnetic transducer, the diaphragm is composed of a flat flat diaphragm, a voice coil, and a conventional magnetic circuit. On the other hand, as a planar electromagnetic transducer, a diaphragm made by printing a conductor corresponding to a voice coil of a cone electromagnetic transducer on a thin sheet is driven by a magnetic circuit of a magnetic circuit in which a bar magnet is arranged. There is a transducer.

Supervised by Tamon Saeki, “Speaker & Enclosure Encyclopedia”, Seibundo Shinkosha, May 1999

  However, the above-described conventional flat electromagnetic transducer has a structure that requires a voice coil and a magnetic circuit that has the same structure as the conventional electromagnetic transducer, and thus it is difficult to reduce the depth. Further, the conventional gummazone type electromagnetic transducer is suitable for a thin TV because it is flat and has a small depth, but there is a problem that the vibration displacement of the diaphragm cannot be increased and it is not suitable for low sound reproduction.

  The present invention has been made to solve the above-described problems, and has an object to provide an electromagnetic transducer that can reproduce a low frequency range with a simple configuration, a smaller depth, and a flat diaphragm. To do.

  The electromagnetic transducer according to the present invention includes a yoke made of a rod-shaped magnetic body, a rod-shaped magnet disposed so as to have a predetermined gap with the yoke, and a rod-shaped drive having a conductor pattern formed on the surface and inserted into the gap It comprises a member, a flat diaphragm fixed to the drive member, and a frame that supports the diaphragm.

  According to the electromagnetic transducer according to the present invention, the drive member formed with the conductor pattern is inserted into the gap between the bar-shaped yoke and the bar-shaped magnet, thereby reducing the depth with a simple configuration, A flat sound pressure characteristic can be obtained. As a result, it is possible to obtain an electromagnetic transducer that is thinner and can be reproduced down to the low sound range.

It is a schematic perspective view which shows the whole electromagnetic converter which concerns on Embodiment 1 of this invention. It is the AA line (a) longitudinal cross-sectional view of FIG. 1 which shows the structure of the electromagnetic transducer of Embodiment 1, (b) It is a partial detailed perspective view. 3 is a perspective view illustrating a structure of a drive member of the electromagnetic transducer according to Embodiment 1. FIG. It is (a), (b) schematic perspective view which shows the other example of the electromagnetic transducer of Embodiment 1. FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Embodiment 1 FIG.
FIG. 1 is a schematic perspective view showing the entire electromagnetic transducer according to the present embodiment.
2A and 2B are diagrams illustrating a configuration of the electromagnetic transducer, in which FIG. 2A is a cross-sectional view taken along the line AA in FIG. 1, and FIG. 2B is a detailed perspective view illustrating a partially enlarged view of FIG. FIG.
FIG. 3 is a perspective view showing the structure of the drive member.

  The electromagnetic transducer 1 is roughly divided into a vibration system 2 and a magnetic circuit 3, and the vibration system 2 and the magnetic circuit 3 are supported and configured by a frame 30 as a support member. As shown in FIG. 1, the electromagnetic transducer 1 according to the first embodiment includes a vibration system 2 and two magnetic circuits 3 arranged in parallel in a rod shape.

The vibration system 2 includes a vibration plate 10, an edge 12 that supports the vibration plate 10, and a driving member 4.
The diaphragm 10 is a rectangular flat plate made of a lightweight material, and an edge 12 is bonded to the outer periphery thereof. The edge 12 has a semi-roll cross section, the inner periphery is bonded to the diaphragm 10, and the outer periphery is bonded to the outer periphery. The frame 30 is fixed by adhesion.
The driving member 4 includes a base material 14 and a conductor pattern 15 formed on the surface of the base material 14. The shape of the drive member 4 is a rod shape whose cross section is formed in a U-shape (hereinafter referred to as a cross-sectional U shape), and one surface of the drive member 4 is bonded and fixed to the back surface of the diaphragm 10. The detailed structure of the drive member 4 will be described later.

The magnetic circuit 3 includes a magnet 20 and a yoke 23. The magnet 20 is a bar-shaped permanent magnet having a rectangular cross section, and is magnetized in the width direction of the cross section. The yoke 23 is made of a bar-shaped magnetic body having a U-shaped cross section, and the magnetic field lines are efficiently tied by inducing the magnetic flux of the magnet 20. It is acting like that. The magnet 20 is disposed on the inside of the U-shaped cross section of the yoke 23, and a certain gap is provided as a magnetic gap (hereinafter referred to as a gap) 25 between the inner wall of the U-shaped cross section of the yoke 23 and the magnet 20. Opposite sides having a U-shaped cross section of the drive member 4 are inserted into the gap 25.
Note that the interval of the gap 25 formed between the magnet 20 and the yoke 23 is set as appropriate. By setting the interval small, the magnetic flux density in the gap 25 can be increased. A strong magnetic path can be formed within a height range of 20.

  The magnetic circuit 3 is in the shape of a long and narrow bar having a substantially rectangular cross section and large in the length direction, and the drive member 4 facing it has the same length. The lengths of the magnetic circuit 3 and the driving member 4 are close to one side of the diaphragm 10.

Here, the structure and manufacturing method of the drive member 4 will be described.
As shown in FIG. 3, the drive member 4 is a sheet-like member in which a conductor pattern 15 is formed on a base material 14. The conductor pattern 15 is formed in a spiral shape on both surfaces or one surface of the substrate 14, and terminals 16 are formed at both ends of the conductor pattern 15 to receive signals from the outside.
The base material 14 is made of, for example, a flat sheet of polymer resin or engineering plastic, and is formed to have sufficient thickness and strength so as to be sufficiently self-supporting. The conductor pattern 15 is made of, for example, a foil material such as copper or aluminum, and is bonded onto the surface of the base material 14. The foil material bonded onto the base material 14 is processed so as to leave a predetermined pattern by etching or the like in the same manner as the FPC (Flexible Printed Circuits) manufacturing method.
The drive member 4 manufactured in this way is formed by being bent into a U-shaped cross section by thermoforming or the like.

  The operation of the electromagnetic transducer 1 will be described. When a signal is applied to the conductor pattern 15 of the drive member 4 from a control unit (not shown), the electromagnetic transducer 1 causes a current to flow along the conductor pattern 15, and the direction in which this current flows is orthogonal to the magnetic field generated by the permanent magnet. Therefore, in accordance with Fleming's left-hand rule, a driving force is generated in the drive member 4 in the vertical direction in the cross-sectional height direction, and the diaphragm 10 coupled to the drive member 4 vibrates up and down to generate sound.

As described above, according to the electromagnetic transducer according to the first embodiment of the present invention, a large driving force can be obtained because of the structure using the magnetic field having a high magnetic flux density in the narrow magnetic gap 25, and the reproduced sound pressure level. A highly efficient electromagnetic transducer can be realized.
In addition, since the driving force can be made uniform by distributing a plurality of magnetic circuits 3, a flat sound pressure frequency characteristic with little fluctuation can be obtained.

  Furthermore, as shown in FIG. 1 or FIG. 2, the electromagnetic transducer 1 that supports the vibration system 2 having the planar diaphragm 10 as a main member and the rod-like magnetic circuit 3 with a thin frame 30 can be configured. At the same time, it is possible to obtain a very thin electromagnetic transducer with a small number of parts and a simple structure.

  In the description, the edge 12 has been described as having an outer periphery bonded and fixed to the frame 30. However, the present invention is not limited to this, and the edge 12 may be directly fixed to a television housing as necessary. Good.

  Further, in general, the diaphragm 10 often generates a divided vibration that is a natural resonance in the middle and high range, and in order to realize a wide reproduction band by pushing this divided vibration to the high range, it is shown in FIG. Thus, it is desirable that the number of magnetic circuits 3 be two (or more than three). That is, by using a plurality of pieces, the splitting vibration is suppressed so that the driving force is dispersed and the driving force is evenly transmitted to the diaphragm, thereby realizing a wide band.

  Moreover, in the electromagnetic transducer of Embodiment 1, although the structure which drives to the rectangular diaphragm 10 with two sets of magnetic circuits 3 was shown, this invention is applicable to the electromagnetic transducer of another form. As an example, a diaphragm 10 having a large aspect ratio is driven by a single magnetic circuit 3 as shown in FIG. 4A, or two acute-angled triangular diaphragms 10 are used as shown in FIG. Various combinations such as a mode of driving with a set of magnetic circuits 3 are conceivable.

Further, the drive member 4 in the above embodiment has a U-shaped structure as described above, but the end of the drive member 4 is used as a base in order to suppress deformation caused by the drive force and to maintain structural strength. The side surface may be formed by closing with the material 14 (or its equivalent). That is, the drive member 4 may have a box shape structure.

Further, since the plate-like diaphragm 10 is structurally weak, it is desirable to use a three-layer structure such as a honeycomb structure with a rigid component material itself, or a thick plate, such as a foam material or an infinite number of materials. It is also possible to use a lightweight material such as a microbubble structure with a hollow sphere bound thereto.

  Further, as shown in FIG. 1 or FIG. 2, the planar diaphragm 10 has a structure that is supported only by the edge 12 and is driven by the driving member 4. However, when the vibration system 2 becomes heavy, the edge 12 is loosened or driven. Sometimes rolling occurs. As a countermeasure, a means for supporting the central portion or the peripheral portion of the diaphragm 10 or a structure in which a spider is joined to the drive member 4 and supported in the same manner as a spider of a conventional electromagnetic transducer may be adopted.

  Further, in FIG. 1, FIG. 4A, and FIG. 4B, the frame 30 is omitted for easy explanation.

  DESCRIPTION OF SYMBOLS 1 Electromagnetic transducer, 2 Vibration system, 3 Magnetic circuit, 4 Driving member, 10 Diaphragm, 12 Edge, 14 Base material, 15 Conductor pattern, 16 Terminal, 20 Magnet, 23 York, 25 Magnetic gap (gap), 30 frame .

Claims (3)

A yoke made of a rod-shaped magnetic material;
A rod-shaped magnet arranged to have a predetermined gap with the yoke;
A rod-shaped drive member having a conductor pattern formed on the surface and inserted into the gap;
A flat diaphragm fixed to the driving member;
An electromagnetic transducer comprising a frame that supports the diaphragm.   The electromagnetic transducer according to claim 1, comprising a plurality of the yoke, the magnet, and the driving member. The yoke has a U-shaped cross section,
The magnet is disposed so as to have a predetermined gap inside the U-shape of the yoke,
2. The electromagnetic transducer according to claim 1, wherein the drive member has a U-shaped cross section, and opposite sides of the formed U-shape are inserted into the gap.

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