JPS60244197A - Electroacoustic transducer - Google Patents

Abstract

PURPOSE:To obtain a satisfactory reproduction sound by providing a holding frame at the outer periphery of a diaphragm on a holding member of an electrode and holding only the outer periphery of the diaphragm. CONSTITUTION:Electrodes 3a-3c are fitted in and held in recessed parts 11a- 11c provided in accordance with shapes of said electrodes 3a-3c on the surface of an insulating material 11, and insulated each other by an insulating part 12. On the other hand, a diaphragm 1 is disposed oppose to the electrodes 3a-3c, and only its outer periphery is fixed and held by a holding frame 13. As a result, vibrations are given to respective parts of the diaphragm 1 corresponding to the electrodes 3a-3c, and the entire transducer vibrates, using these vibrations as a total sum. A frequency characteristic of each unit of the transducer retains the prescribed level difference in an overall band, and a normal reproduction sound can be obtained in all frequency bands.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an electroacoustic transducer that directly inputs a PCM (pulse code modified 1Pl) signal and converts it into an analog acoustic signal.

[Prior art]

The conversion methods of the electroacoustic transducer as described above include electrodynamic type, electrostatic type, piezoelectric type, and electromagnetic type.

In addition, as a method for driving the entire converter, (1) using a plurality of units with the same performance and weighted PC
There are those that are driven by the M signal, (2) those that weight the converter itself by changing the driving force and area of the diaphragm, and (3) those that combine the above (11 and (21)).

Figures 1 and 2 are rTHE BELL SYSTEM
学ECHNICAL JOURNAL.

Novjmber 1980. page 1693-1
This is an electrostatic type 4-pin converter using an electret or foil as a diaphragm described in 719J, and the driving method is the above-mentioned method (21). Figure 1 is a front view, Figure 2 The figures are cross-sectional views, and in each figure, 1 is a disk-shaped diaphragm made of electret foil, 2 is a fixing plate 3a having protrusions 2a, 2b, and 2c that are acoustically transparent and fix the diaphragm 1.

Reference numerals 3b and 3c are ring-shaped or circular electrodes arranged concentrically, and are fixed to and held by an insulating material 4 as a holding member, and protrusions 4a of the insulating material 4.

4b and 4c, respectively. The diaphragm 1, the fixed plate 2, and the insulating material 4 provided with the electrodes 3a, 3b, and 3c are housed in a fixed ring 5, and an acoustic low-pass filter 6 is provided on the front surface. The diaphragm 1 has protrusions 2a, 2b, 2c on the fixed plate 2 and protrusions 4a, 4b on the insulating material 4.

It has fixing parts 7a, 7b, 7c supported by 4c,
As a result, the diaphragm l is divided into la, lb, and Ic. Here, the diaphragms 1a and lb.

Weighting is performed by setting the mutual area ratio of 1c to 2. Note that a digital signal is applied to the electrodes 3a, 3b, and 3c through input terminals 8a, 8b, and 8c, respectively, and the most significant bit (MSB) of the digital signal is switched to 1E or -E by a polarity changeover switch 9. and each input terminal 8a.

8b and 8c, and the lower 3 pins are applied to input terminal 8 in order.
It is applied to a, 8b, and 8c. The electroacoustic transducer includes diaphragms 1a, lb, and Ic and electrodes 3a facing them.
, 3b, 3c and input terminals 8a, 8b, 8c are the knees 1-7 and 10a, respectively.

10b and 10c, each unit 10a.

10b and '10c constitute one electroacoustic transducer. In such a configuration, when a PCM signal is applied to the units 10a, 10b, and IOc corresponding to each bit, a pulse amplitude modulated sound pressure is generated from the converter.

In the multi-Unit type converter as mentioned above,
The individual units lOa that make up it.

10b, the IOC must simultaneously generate a sound pressure proportional to its area. To do this, the level difference corresponding to the area must be ignored for each unit 10a, .

It is desirable that the output sound pressure frequency characteristics (hereinafter referred to as f characteristics) of 10b and 10c are the same. However, in a converter in which the diaphragm 1 is fixed concentrically as in the conventional example, the divided diaphragms la, lb, and lc have different shapes and areas.
1 (lb.

The trends regarding the f characteristics of 10C are different.

Next, the above characteristic trends will be explained using FIG. 3 (a) to (il). The time waveform (impulse response) of the output sound pressure when each unit is driven independently, (e) and (i) also show the f characteristic. The characteristics of the acoustic conversion unit are shown, and (f) to (il show the characteristics of an actual unit such as the conventional example described above. In the figure, the horizontal axis T represents time, F represents frequency, and the vertical axis represents The i-numbered bell and La represent the sound pressure level.

In addition, A, AI, B, and Bt represent each characteristic, and subscripts a,
b, c are Uniso of the conventional example) 10a.

10b and 10c. If each unit is ideal, each unit will output impulse response waveforms Aa, Ab, and Ac similar to the input signal shown in ta+ in the same figure, as shown in Figure 3 cby to (d), and The amplitude (sound pressure level La) changes by a factor of two. In order to obtain such a waveform, the f-characteristics Ba, Bb, and Bc of each unit must be constant over the entire frequency band, with a level difference of 6 dB each, as shown in FIG. 2(e).

However, the unit 10a shown in the conventional example.

The f characteristics of the diaphragms 10b and 10c tend to be as shown in FIG.
Fixed part fixed by 2b, 2c, protrusions 4a, 4b, 4c? 'a, 7b, and 7G, so the reproduction band of low and high frequencies is limited.The smaller the area of the diaphragm, the more the reproduction band shifts toward higher frequencies. In the region, resonance between the diaphragms occurs and the sound pressure level La
The center diaphragm IC and the outer diaphragm 1a fluctuate.

This is due to the fact that the fixing conditions for lb are different. For this reason, in Fig. 3(f) to Th), the impulse response waveform is
a, Alb, and Ale, and due to continued small level fluctuations, a normal sound pressure level could not be obtained, and as a result, the f characteristic changed to low frequency,
In the high frequency range, it becomes impossible to maintain a level difference of 6 dB each.

[Summary of the invention]

The present invention eliminates the above drawbacks by providing a holding member that holds an electrode with a holding frame that holds the outer periphery of the diaphragm so that only the outer periphery of the diaphragm is held by the holding frame. This will be explained in detail using .

[Embodiments of the invention]

FIG. 4 is a sectional view showing an embodiment of the electroacoustic transducer according to the present invention, and the same parts as in FIG. In the figure, electrodes 3a, 3b, 3c
The above electrode 3a is placed on the surface of the insulating material 11 as a holding member,
Recesses 11a, l provided corresponding to the shapes of 3b, 3c
lb and llc are fitted and held, and are insulated from each other by the insulating portion 12 of the insulating material 11. On the other hand, diaphragm 1
is a holding frame 1 which is disposed facing the electrodes 3a, 3b, '3c and protrudes from the outer periphery of the insulating material 11 to the front surface.
3, only the outer periphery is fixed and held.

In this way, in this embodiment, the fixing plate 2 and the protrusions 4a, 4b, 4c of the insulating material 4, which have the protrusions 2a, 2b, 2c in the conventional example, are not provided, and the fixing portions 4a, 4b, 4c are not provided. a, 7b, 7c are eliminated and the diaphragm 1 is held only by the holding frame 13, and the diaphragm 1 corresponding to each electrode 3a, 3b, 3c is
Vibration is applied to each part of the body, and the sum of these vibrations causes the whole body to vibrate. As a result, the f characteristics of each unit of the converter become as shown in FIG. 5, and a predetermined level difference can be maintained over almost the entire band. Therefore, normal reproduced sound can be obtained in almost the entire frequency band.

In the above embodiment, vibration +7i 1 and electrode 3
has described a case in which a circular electrode 3 is used, and the electrode 3 is in the form of an area-proportional ring, but the electrode 3 is not limited to these. Alternatively, a circular or rectangular diaphragm may be used, as shown in Fig. 6 (a).
It is also possible to provide an electrode 3 divided into equal areas by an insulating part 12 as shown in (bl) and use the driving method 1 described at the beginning.Also, in the above embodiment, an electrostatic type Although the transducer described above has been described, a transducer using a membrane-shaped diaphragm such as a piezoelectric type may also be used.

By the way, in the above description, an electroacoustic transducer that directly inputs a PCM signal and converts it into an analog acoustic signal was described, but the present invention is applicable to an ordinary multi-channel transducer that configures a plurality of units on at least one diaphragm. Needless to say, the present invention can be applied to speakers of way speaker devices.

〔Effect of the invention〕

As explained above, according to the electroacoustic transducer according to the present invention, the holding member that holds the electrode is provided with a holding frame that holds the outer circumference of the diaphragm, and the holding frame holds only the outer circumference of the diaphragm. , so you can get good playback sound.

[Brief explanation of drawings]

1 and 2 are a front view and a sectional view showing an example of a conventional electroacoustic transducer, FIG. 3 is a characteristic diagram for explaining the operation of the conventional example, and FIG. 4 is an embodiment of the present invention. FIG. 5 is a sectional view showing an example, FIG. 5 is a characteristic diagram showing the operation of the above embodiment, and FIGS. 6 and 7 are configuration diagrams of electrodes showing other embodiments of the present invention. 1... Vibration plate, 3... Electrode, 11... Insulating material, 1
2... Insulating section, 13... Holding frame. Note that the same reference numerals are used for the same or corresponding parts in the figures. Agent: Masu Oiwa A (and 2 others) Figure 4 Figure 5 Figure 6 Figure 7 Procedural amendment (Owned in 1985, 3 A6 To the Commissioner of the Japan Patent Office 1, Indication of the case Patent application 1982- No. 099-976 2, Name of the invention Electro-acoustic transducer 3, Representative Hitoshi Katayama of the person making the amendment Section 5, Detailed explanation of the invention subject to the amendment 6. Contents of the amendment + 11 Specification page 6 In the 5th line, "resonance between the plates" is corrected to "resonance of the plate body".

Claims (1)

[Claims] An electroacoustic transducer comprising a diaphragm, a plurality of electrodes facing the diaphragm and to which a digital signal is supplied for each bit, and a holding member that holds the electrodes,
An electroacoustic transducer characterized in that the holding member is provided with a holding frame that holds the outer periphery of the diaphragm so that only the outer periphery of the diaphragm is held.