JP2005175553A - Flat acoustic apparatus and composite information display apparatus mounted with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flat acoustic apparatus having an excellent acoustic characteristic by suppressing the split vibration of a diaphragm. <P>SOLUTION: The flat acoustic apparatus includes a transparent diaphragm provided with a vibration drive body to be installed in front of the recognition side of a display screen of a rectangular shape in an information display apparatus by leaving an interval from the display screen. The transparent diaphragm is formed to be nearly an elliptic shape or circular shape whose diameter is greater than the length of the longer side of the rectangular shape of the display screen, and the vibration drive body is placed in a crescent segment region not overlapping the display screen. The vibration drive body is a piezoelectric vibrator whose piezoelectric member is located to one side or both sides of the diaphragm and shaped to be a crescent shape equal to the segment region of the transparent diaphragm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention vibrates a transparent diaphragm with a configuration in which a vibration diaphragm is placed on the transparent diaphragm and a transparent diaphragm disposed on the front side of the viewing side of a rectangular display screen in an information display device. The present invention relates to a planar acoustic device that emits sound and a composite information display device equipped with the same.

  In recent years, display screen technology and image processing technology in information display devices have been rapidly advanced, and as a result, higher functionality and multi-functionality have been demanded in acoustic devices mounted on information display devices. Yes. In particular, the above requirements for information display devices for entertainment are significant. In such a background, instead of the conventional information display device in which the acoustic device is arranged at a different location from the display screen, a planar acoustic device having a configuration in which a transparent diaphragm is disposed on the front side of the viewing side of the display screen is mounted. The composite information display device that has been used is attracting attention.

As described above, the flat acoustic device is a device that induces vibration in the transparent diaphragm by means such as arranging a vibration driver on the transparent diaphragm disposed in front of the viewing side of the display screen. It is a device that can produce acoustic effects. In the compound information display device equipped with this flat-type sound device, sound can be heard directly from the screen on which the image is projected, realizing a close sense of unity between image and sound that was impossible with conventional information display devices. (For example, refer to Patent Document 1).
Furthermore, in this flat acoustic device, the diaphragm can be vibrated over a wide area as large as or larger than that of the display screen, so that the sound pressure characteristics particularly in the low sound region can be improved.

Hereinafter, a conventional flat acoustic device and a composite information display device equipped with the same will be described with reference to FIGS. FIG. 5 is a perspective view showing an example of a conventional composite information display device in which a general information display device 10 is provided with a detachable planar acoustic device 18.
The planar acoustic device 18 includes a transparent diaphragm 11, vibration drivers 12a to 12d, an outer frame 13, a mounting bracket 14 for an information display device, a connector 15, and a coated electric wire 16 for inputting an acoustic signal. Yes. The transparent diaphragm 11 is fixed to the outer frame 13, and is attached to a portion that does not overlap the display screen 17 of the information display device 10 in a form in which the vibration driving body indicated by reference numerals 12 a to 12 d is built in the outer frame. ing. By inputting an electroacoustic signal to the vibration drivers 12a to 12d, the vibration of the transparent diaphragm 11 is induced, and a desired sound can be emitted forward. Details of this operation will be described in detail later. The flat acoustic device 18 is normally used in a form attached to the information display device 10.

  As shown in FIG. 6, the vibration driver 12 a includes a magnet 20, a coil 21, a magnetic circuit unit such as a movable inner yoke 22 and an outer yoke 23 around which the coil is wound, and a sub diaphragm 24. It has the same operating principle as a normal electromagnetic type acoustic device. Since the movable inner yoke 22 is fixed to the transparent diaphragm 11 via the sub diaphragm 24, the acoustic vibration of the movable inner yoke 22 caused by the input of the electroacoustic signal is transparent as it is via the sub diaphragm 24. Propagated to the diaphragm 11.

  Further, since the transparent diaphragm 11 is supported and fixed so that the peripheral portion thereof is fitted to the inner side wall of the outer frame 13 via the elastic adhesive 25, the transparent diaphragm 11 is caused by acoustic vibration propagated from the auxiliary diaphragm 24. The bending vibration of the entire transparent diaphragm 11 is induced. The sound effect that the sound is directly emitted from the screen is obtained by radiating the sound field vibration generated from the bending vibration into the space.

JP 2001-189978 A (5th page, FIG. 1-2)

  However, in the conventional planar acoustic device as shown in FIG. 5, the rectangular transparent diaphragm 11 as shown in FIG. 7 is generally used, and a large number of divisions resulting from the rectangular shape are used. The appearance of vibration causes a problem of deterioration in acoustic characteristics.

  This divided vibration is a phenomenon in which each part of the diaphragm oscillates with a non-uniform phase at a specific natural frequency when the diaphragm, which is an elastic body, vibrates. It is a phenomenon often seen in the sound range. Before and after the frequency that induces this divided vibration, the conversion efficiency from the electroacoustic signal to the acoustic vibration in the diaphragm changes greatly, and as a result, the sound pressure frequency characteristic is changed in the vicinity of the specific natural frequency described above. It brings about significant undulations.

FIG. 8A is a diagram showing the sound pressure frequency characteristics of a rectangular diaphragm in the planar acoustic device shown in the background art. In this drawing, the horizontal axis represents frequency and the vertical axis represents sound pressure. Indicates the level.
In general, the rectangular transparent diaphragm 11 used in the flat acoustic device shown in the background art has a large number of natural frequencies that induce the divided vibration. For example, FIG. As shown, the flatness of the sound pressure frequency characteristic particularly in the high sound range is lost, and the acoustic characteristic is significantly deteriorated.

  Further, in the case of an acoustic device that obtains an acoustic effect by bending vibration of the transparent diaphragm 11, in order to improve acoustic characteristics, it is required to have a vibration mode in which the maximum amplitude is obtained at the center of the diaphragm. However, in the electromagnetic vibration drive body 12 as in the background art, it is necessary to control the degree of amplitude at each part of the transparent diaphragm 11 by optimizing the mounting position and the number of the vibration driving bodies 12. It takes very complicated work to obtain.

  Further, in the electromagnetic vibration driving body, in order to obtain a sufficient amplitude of the transparent diaphragm 11, avoiding an increase in the size of the vibration driving body 12 itself, such as increasing the number of turns of the coil 21 or enlarging the magnet 20. The increase in electromagnetic noise caused by the increase in size causes an adverse effect on the information display device.

  An object of the present invention is to solve the above-mentioned problems, and to provide a flat acoustic device capable of obtaining good acoustic characteristics and reducing electromagnetic noise.

  In order to achieve the above object, the acoustic device of the present invention employs the following configuration.

  A planar acoustic device according to the present invention is a planar acoustic device having a transparent diaphragm provided with a vibration driver for disposing separately on the front side of the viewing side of a rectangular display screen in an information display device. The shape of the diaphragm is at least an elliptical shape with a major axis diameter larger than the long side of the rectangular shape of the display screen, or a substantially circular shape with a larger diameter, so that the vibration drive body does not overlap the display screen. It is characterized by being placed in the section area of

    The planar acoustic device according to the present invention is configured to vibrate and drive the transparent diaphragm as a substantially elliptical shape having a larger major axis diameter or a substantially circular shape having a larger diameter than the long side of the rectangular shape of the display screen. It is characterized in that the body is placed on a half-moon shaped segment area that does not overlap the display screen.

The planar acoustic device according to the present invention is characterized in that the shape of the transparent diaphragm is a substantially elliptical shape or a drum shape in which two opposite sides from a substantially circular substrate are cut out in a straight line.

  The planar acoustic device according to the present invention is characterized in that the vibration driver is a piezoelectric vibrator in which a piezoelectric material is disposed on one side or both sides of a transparent diaphragm.

  The planar acoustic device according to the present invention is characterized in that the shape of the piezoelectric vibrator is the same half-moon shape as that of the cut edge region.

  A composite information display device equipped with a planar acoustic device according to the present invention includes a planar acoustic device and an information display device having a display screen, and the display screen can be visually recognized in the peripheral portion of the transparent diaphragm of the planar acoustic device. Thus, the outer frame is attached to an outer frame provided with an opening, and the outer frame is detachable from the information display device.

  In the flat acoustic device according to the present invention, the sound pressure frequency characteristics generated due to the divided vibrations are remarkably improved by improving the shape of the transparent diaphragm spaced apart on the front side of the display screen in the information display device. Not only can undulations be suppressed and the acoustic characteristics can be improved, but the acoustic characteristics can be further improved by improving the shape and components of the vibration driver, and the effects of electromagnetic noise can be nullified and the structure of the device The simplification of can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, about the same member as each member shown by background art, it demonstrates using a same sign.

  As shown in FIG. 1, the flat acoustic device according to the present invention has a transparent diaphragm 1 fixed to an outer frame 13 and vibration drivers 12a to 12d mounted on portions of the transparent diaphragm 1 that do not overlap the display screen. However, in the planar acoustic device of the present invention, the shape of the transparent diaphragm 1 is substantially elliptical. It has a certain feature.

  The transparent diaphragm 1 has an area sufficient to cover the display screen of the information display device, as shown by a rectangular broken line, and a peripheral portion of the transparent diaphragm 1 has an elastic adhesive (not shown) attached to the inner side wall of the outer frame 13. It is being fixed so that it may be supported. In addition, the vibration drivers 12a to 12d are attached to predetermined locations in the half-moon shaped segment region 2 that does not overlap the display screen.

  When the vibration is driven by using the substantially elliptical transparent diaphragm 1 having such a peripheral portion supported and fixed as a transparent vibration body in which vibration is induced by the vibration driver 12, the transparent diaphragm is used. Can have a vibration mode close to a circular diaphragm.

  In general, in the case of a circular diaphragm, compared to a rectangular diaphragm, due to the simplicity of its vibration mode, the natural frequency that causes split vibration is reduced, and the acoustic vibration from the electroacoustic signal in the vicinity of the frequency is reduced. The undulation of the conversion efficiency is reduced, and good acoustic characteristics can be obtained. Further, this effect does not appear only in a perfect circular shape, but also appears in a shape in which the shape of the diaphragm is closer to a circular shape, for example, a substantially elliptical shape, as shown in FIG. 8B. Sound pressure frequency characteristics with less undulations can be obtained.

FIG. 8A is a diagram showing the acoustic characteristics of the rectangular diaphragm used in the planar acoustic device shown in the background art, and FIG. 8B is used for the planar acoustic device of the present invention. It is drawing which shows the acoustic characteristic which the substantially ellipse-shaped diaphragm which had it has. The horizontal axis in both drawings indicates the frequency, and the vertical axis indicates the sound pressure level.
As is apparent from this drawing, in the flat acoustic device using the rectangular diaphragm, the flatness of the sound pressure frequency characteristic in the high sound range is lost as shown in FIG. In contrast, it can be seen that the characteristics of the planar acoustic device of the present invention using the substantially elliptical diaphragm are clearly improved in the high sound range compared to the background art.
Note that the correlation between the shape of the diaphragm and the sound pressure frequency characteristic varies slightly depending on the vibration driving method and the material of the diaphragm, and is not necessarily shown in FIG.

  When strictly discussing the grounds for the effects described above, it is necessary to calculate a wave equation of elastic body vibration to obtain a vibration solution, and to compare the correlation between the vibration frequency and the vibration mode. Regarding such a vibration solution, since it becomes a quite complicated special function even in a simple case, it is very difficult to clarify the above-mentioned basis. However, in consideration of the fact that many acoustic devices designed to suppress divided vibrations and improve acoustic characteristics use a diaphragm having a circular shape or a shape closer to a circular shape instead of a rectangular shape. The basis for this is easily understood.

  Therefore, the substantially elliptical transparent diaphragm 1 according to the present invention has a vibration mode close to that of a circular diaphragm, and thus causes divided vibration compared to the rectangular transparent diaphragm 11 in the background art. While the natural frequency decreases, the undulation of the sound pressure frequency characteristic in the vicinity of the frequency is suppressed, and as a result, the acoustic characteristic can be improved.

In the first embodiment, the transparent diaphragm 1 has a substantially elliptical shape, and at least the long axis thereof is larger than the long side of the rectangular display screen. In order to suppress this, the shape of the transparent diaphragm 1 may be circular, and the above-described divided vibration may be suppressed.
Further, the transparent diaphragm 1 may have a substantially elliptical shape or a circular shape so that the transparent diaphragm 1 overlaps a part of the display screen so that the space of the display screen can be effectively used. Absent.

  FIG. 2 is a perspective view showing a second embodiment of the present invention. Instead of the substantially elliptical transparent diaphragm 1 described in the first embodiment, two opposing sides are curved, and the other two opposing sides. Is a so-called drum-shaped transparent diaphragm 3 having a linear shape. As described above, even when the periphery of the diaphragm is partially circularly curved, the above-described improvement in acoustic characteristics appears to some extent, although not as much as an elliptical shape or a circular shape. Furthermore, since this structure reduces the area of a transparent diaphragm compared with the structure shown in Example 1, it can contribute to the area reduction of acoustic apparatus itself including the outer frame 13. FIG.

  FIG. 3 shows an embodiment in which the piezoelectric vibrators 4a and 4b having the same half-moon shape as the previously described section region are attached to the transparent diaphragm 1 as a vibration drive instead of the conventional electromagnetic vibration drive. The member configuration is shown in a perspective view. FIG. 4 shows a sectional view of the piezoelectric vibrator portion.

  The piezoelectric vibrator 4a is formed by adhering a piezoelectric material 5 having thin electrodes formed on both main surfaces of a ceramic plate having a piezoelectric effect to one side or both sides of a vibration plate 6. By applying an electroacoustic signal to this electrode, bending vibration can be generated in the entire piezoelectric vibrator. In the drawing, an example in which the piezoelectric material 5 is arranged on one side of the diaphragm 6 is shown.

The piezoelectric vibrator 4 a is strongly bonded to the transparent diaphragm 1, and the half-moon-shaped arc side is fitted to the outer frame 13 together with the peripheral portion of the transparent diaphragm 1 via the elastic adhesive 25. The support is fixed. In such a member configuration, when an acoustoelectric signal is applied to the piezoelectric vibrator 4a, bending vibration in the left-right direction in FIG. 4 of the piezoelectric vibrator 4a with the fixed portion as a fulcrum is induced. The induced vibration is directly propagated to the flexural vibration of the transparent diaphragm 1, and the sound field vibration generated by the flexural vibration is radiated into the space, thereby obtaining an acoustic effect.

  Since the amplitude of the bending vibration in the left-right direction in the piezoelectric vibrator 4a is substantially proportional to the length y of the piezoelectric vibrator in the up-down direction in FIG. 4, the half-moon shaped piezoelectric vibrator 4a described above is used as a vibration driver. As a result, the amplitude of the flexural vibration in the transparent diaphragm 1 can be increased from the end portion indicated by the alternate long and short dash line 7 toward the center portion indicated by the alternate long and short dash line 8 in FIG. This effect eliminates the need for troublesome work such as optimizing the mounting position and number required for the electromagnetic vibration drive body, and easily obtains a vibration mode in which the maximum amplitude is obtained at the center of the diaphragm. Therefore, the acoustic characteristics can be improved.

  Furthermore, when the piezoelectric vibrator vibration drive as described above is used, the structure of the acoustic device itself can be remarkably simplified as compared with the electromagnetic vibration drive body in the background art, and the information display device main body due to electromagnetic noise can be used. The negative effects of can be nullified.

It is a perspective view which shows the structure of the planar acoustic device in this invention. (Example 1) In the planar acoustic device of the present invention, it is a perspective view showing the shape of another transparent diaphragm. (Example 2) It is a perspective view which shows the structure of the planar acoustic device in this invention. Example 3 It is sectional drawing which shows the structural example of the vibration drive body in the planar acoustic apparatus of this invention. It is a perspective view which shows the structure of the planar acoustic apparatus in background art. It is sectional drawing which shows the structural example of the vibration drive body in the planar acoustic device of background art. It is a perspective view which shows the structural example of the planar acoustic apparatus in background art. It is a figure which shows the sound pressure frequency characteristic which a rectangular-shaped diaphragm has in the planar acoustic apparatus of background art. It is a figure which shows the sound pressure frequency characteristic which the substantially elliptical diaphragm has in the planar acoustic apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transparent diaphragm 2 Section area | region 4 Piezoelectric vibrator 5 Piezoelectric material 6 Diaphragm 10 Information display apparatus 12 Vibration drive body 13 Outer frame 14 Mounting bracket 15 Connector 16 Covered electric wire

Claims (5)

In a flat acoustic device having a transparent diaphragm provided with a vibration driver for disposing at a front side of the viewing side of a rectangular display screen in an information display device,
The shape of the transparent diaphragm is at least a substantially elliptical shape with a major axis diameter larger than a long side of the rectangular shape of the display screen, or a substantially circular shape with a larger diameter. A flat acoustic apparatus, which is placed on a half-moon-shaped section region that does not overlap with the flat-shaped acoustic device.   2. The flat acoustic device according to claim 1, wherein the transparent diaphragm has a drum shape in which two sides facing each other from the substantially elliptical or substantially circular substrate are cut into a straight line. .   The planar acoustic device according to claim 1, wherein the vibration driver is a piezoelectric vibrator in which a piezoelectric material is disposed on one side or both sides of the transparent diaphragm.   The planar acoustic device according to claim 3, wherein a shape of the piezoelectric vibrator is a half-moon shape that is the same as the cut edge region. A flat acoustic device according to any one of claims 1 to 4 and an information display device having a display screen,
An outer frame provided with an opening so that the display screen can be visually recognized is attached to a peripheral portion of the transparent diaphragm of the flat acoustic device, and the outer frame is detachable from the information display device. A composite information display device characterized by

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