JPS60244193A - Electroacoustic transducer - Google Patents

Abstract

PURPOSE:To obtain a satisfactory sound pressure characteristic by forming a groove at a part corresponding to a boundary between respective signal electrodes in a diaphragm. CONSTITUTION:In terms of an insulating fixing plate 10 where signal electrodes 3a-3c are disposed on a surface, projections 10a-10c are provided on a part of a boundary for partitioning a surface outer edge and the electrodes 3a-3c. On the other hand, fixing parts 12a-12c of a disk-like diaphragm 11 for employing an electret film and adhered to the projections 10a-10c of the fixing plate 10, and held. Since a groove 13 is provided adjacent to the fixing parts 12a-12c at the circular edge of respective diaphragm element assemblies 11a-11c, a vibration in the peripheral part becomes free, which serves as relaxing restrictions of the vibration by the fixing parts, and a sound pressure characteristic in a low frequency band can be improved.

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 modulation) signal and converts it into an analog acoustic signal.

[Prior art]

Methods for driving the entire transducer include: +11 A method in which multiple units with the same performance are used and driven by weighted PCM signals; (2) A method in which weighting is performed by the converter itself by changing the driving force and area of the diaphragm; (3) (1) above,
There are some combinations of (2).

Figures 1 and 2 are 1 rTHE BELLSYSTE
M TECT(NICAL JOUR-NAL, NOV
EMBER1980, Pages 1693-1719'J
This is an electrostatic type 4-focus converter using an electret film as a diaphragm described in 1.The driving method is the method (2) above. Figure 1 is a sectional view, Figure 2
The figure is a front view. In each figure, 1 is a disc-shaped diaphragm using an electret membrane, 2 is a fixing plate having protrusions 2a, 2b, 2c that acoustically transmits and fixes the diaphragm 1, 3a,
3b and 3c are ring-shaped or circular signal electrodes arranged concentrically, and are fixed to and held by the insulating material 4, and protrusions 4a and 4b of the insulating material 4.

They are separated from each other by 4G. The above-mentioned diaphragm 1, fixed plate 2, and signal electrodes 3a, 3b, and 3c were provided! ! !
The edge material 4 is housed in a fixing ring 5, and an acoustic low-pass filter 6 is provided on the front side. Note that the diaphragm 1 is a protrusion 2a of the fixed plate 2.

2b, 2c and fixed portions 7a, 7b, 7c supported by projections 4a, 4b, 4c of the insulating material 4, whereby the diaphragm 1 has diaphragm bodies 1a, lb.

It is divided into IC. Here, it is the diaphragm element 1a.

Weighting is performed by setting the mutual area ratio of Ib and Ic to 2. Note that the signal electrode 3a.

3b and 3e have input terminals 8a and '8b, respectively.

A digital signal is applied through 8C, and the topmost bin (MSB) of the digital signal is switched to +E or -E by the polarity changeover switch 9 to each input terminal 8a, 8b.
, 8c, and the lower three pins are applied to the input terminal 8a in order.
, 8b, 8c. In such a configuration, P is applied to the signal electrodes 3a, 3b, 3c corresponding to each focus.
When the CM (sign) is applied, the corresponding diaphragm element 1a,
lb.

1c vibrate to generate sound waves, which are radiated through the low-pass filter 6.

However, in the above conventional example, if we pay attention to the diaphragm elements 1a, lb', and lc of the diaphragm 1, are the outer peripheral ends of the diaphragm elements 1a, lb, and lc fixed parts? a, 7b
, 7c, and the inner peripheral ends of the diaphragm elements 1a, lb located on the outer circumferential side are also fixed by fixing parts 7b, 7c. Therefore, the vibration of each of the diaphragm bodies 1a, lb, and 'Ic is limited because the peripheral ends are fixed. Particularly in low frequency bands, the influence is large and the sound pressure characteristics deteriorate.

[Summary of the invention]

The present invention eliminates the above-mentioned drawback by forming grooves on the diaphragm at portions corresponding to the boundaries between signal electrodes, and will be described in detail below using examples.

[Embodiments of the invention]

3 and 4 are simplified configuration diagrams showing one embodiment of an electroacoustic transducer according to the present invention. FIG. 3 is a front view, and FIG. 4 is a sectional view, showing a part of this embodiment which is symmetrical in the vertical and horizontal directions. Note that the same reference numerals are used for the same parts as in the conventional example, and the explanation thereof will be omitted. In each figure, 1o is a signal electrode 3a on the surface.

3b and 3c are insulating fixing plates arranged, and the fixing plate 10 has an outer peripheral edge of its surface and each signal electrode 3a, 3.
A convex portion 10a is provided at the boundary portion dividing each of the portions b and 3c.
, 10b, and 10c are provided. On the other hand, reference numeral 11 denotes a disk-shaped diaphragm using an electret membrane, and the diaphragm 11 is held by fixing parts 12a, 12b, and 12c fixed to convex parts 10a, 10b, and 10c of the fixing plate 10. The diaphragm 11 has a fixing portion 12a.

A groove 13 having a semicircular cross section is formed adjacent to 12b and 12c. Although the groove 13 is integral with the diaphragm 11, it can be easily molded from a polymeric resin such as an electret film.

The present embodiment is constructed as described above, and the grooves 13 are located at the peripheral ends of the respective diaphragm bodies 11 a, 1 l b, and 11 c, that is, at the fixing portions 12 a, 12 for fixing the diaphragm 11.
Since it is provided adjacent to b and 12c, the peripheral end can vibrate freely, and the fixed part? This functions to alleviate the vibration limitations caused by a, 7b, and 7c, and the sound pressure characteristics in the low frequency band are improved.

This will be explained with reference to FIG. The figure shows the diaphragm element 11.
It shows the individual output sound pressure frequency characteristics (hereinafter referred to as f characteristics) of a, llb, and llc, where the horizontal axis is frequency F, and the vertical axis is sound pressure level ° (dB) L. Characteristic A is the one in this example. , characteristic B
1 and 2 respectively show f characteristics in the conventional example. As shown in the figure, according to this embodiment, the f characteristic in the low frequency band is improved.

In addition, in the above embodiment, each diaphragm element 11a, l
The convex portions 10b and 10c of the plate 10 fixing the boundaries of lb and llc
Although a structure in which the diaphragm elements 11a, llb, and llc are fixed is shown in FIG. 6, a structure in which the boundaries of the diaphragm elements 11a, llb, and llc are not fixed may also be used. Furthermore, in the above embodiment, the diaphragm 11 is disc-shaped, and each diaphragm body 11a, llb, llc is formed in a concentric shape, and the groove 13
described a transducer having a semicircular cross section, but the transducer is not limited to these shapes as long as it uses a membrane-like diaphragm and has grooves integrally formed.

For example, a diaphragm having a shape such as a rectangular polygon or an ellipse may be used, and grooves having an arbitrary cross-sectional shape may be formed.

By the way, in the above embodiment, an electrostatic type transducer using an electret film and an area proportional type drive system described in (2) mentioned at the beginning were described, but a piezoelectric type etc. may also be used. The converter is not limited to the area-proportional drive method, and may be a converter that takes both of the formulas fl) and (2).

〔Effect of the invention〕

As explained above, according to the electroacoustic transducer according to the present invention, the grooves are formed in the portions of the diaphragm corresponding to the boundaries between the signal electrodes, so that the electroacoustic transducer has good sound pressure characteristics. There is an effect that can be obtained.

[Brief explanation of drawings]

1 and 2 are simplified configuration diagrams showing an example of a conventional electroacoustic transducer, and FIGS. 3 and 4 are diagrams showing the present invention. 3a, 3b,' 3cm -- Signal electrode, 1o... Fixed plate, 11... Vibration plate, 12'a, 12b. 12c...fixing part, 13...groove. Note that the same reference numerals are used for the middle part of the figure or corresponding parts.

Claims (1)

[Claims] In an electroacoustic transducer comprising at least a diaphragm and a signal electrode facing the surface of the diaphragm and to which a digital signal is supplied for each bit, a portion of the diaphragm corresponding to the boundary between each signal electrode An electroacoustic transducer characterized by forming a groove.