JP2753896B2 - Pressure vibration detection element - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure vibration detecting element such as a condenser microphone and a ceramic microphone.

[Prior Art] A conventional condenser microphone having a cylindrical case with a bottom has an air flow passage or a small hole formed on the open side and the bottom side of the case so that air inside and outside the case flows sufficiently. The capacitance was changed to convert the pressure fluctuation into an electric signal.

In addition, in the condenser microphone of Primo ICEM-EM-121, the bottom side has an air hole as before, but the open side is through a plurality of ring-shaped insulating spacers,
The electret film forming the pressure-receiving surface and its counter electrode are sandwiched over the entire peripheral portion on the open side, and a slight gap is formed between the ring-shaped insulating spacer and the electret film and between the ring-shaped insulating spacer and the counter electrode. In some cases, only air was flowing through the gap.

3 to 5 show prior art examples, in which (2) is a case provided with a lead wire hole (2a) at the bottom, and (3) is a FET transistor (4). Is mounted on the circuit board, and a lead wire (not shown) is drawn from the circuit board (3) through the hole (2a) of the case (2).
Is drawn out.

(5) is a space holding / supporting member on a cylinder having upper and lower openings, and a plurality of ring-shaped insulating spacers (7) are provided between the upper end surface (5a) and the bent end portion (2b) of the case (2). )
The peripheral edge of the electret film (6a) forming the pressure receiving surface and the opposing electrode (6b) is sandwiched entirely. Therefore, as shown in FIG. 4, the condenser microphone (1) is provided between the bent portion (2b) of the case (2) and the ring-shaped insulating spacer (7), between the ring-shaped insulating spacer (7) and the electret film (6a).
Between the ring-shaped insulating spacer (7) and the counter electrode (6b)
A small gap (10) is formed in some places, such as between the outside and the outside, and the air trapped in the space formed inside the condenser microphone (1) flows through the gap (10) so as to leak, The electret film (6a) bends due to the pressure fluctuations generated in the above, causing the capacitance formed between the electret film (6a) and the counter electrode (6b) to change, thereby converting the pressure fluctuations into electric signals. Further, as shown in FIG. 5, each member (2), (3),
(5) When a gap (10) is generated between them and a pressure fluctuation occurs outside, air in the space formed inside the condenser microphone (1) flows through the hole (2a) of the case (2). I do. One lead terminal (4a) of the FET transistor (4) is always electrically connected to the opposite electrode (6b) of the electret film (6a).

[Problems to be Solved by the Invention] However, since this type of condenser microphone has been developed for acoustic use, the frequency characteristics of the lower frequency are measured only up to about 20 Hz that can be heard by human ears. In addition, there is no guarantee as a product in the catalog at present, 20Hz or less, for example, 0, Hz, 1H
It cannot be used in a very low frequency region such as z in terms of performance and its structure.

In addition, motor noise generated from the equipment installed around,
In order to prevent mechanical noise such as vibration noise from being absorbed from the small holes or the like, there is known a condenser microphone that seals the back and peripheral sides of a case (for example, Japanese Utility Model Publication No. 56-5471).
1, No. 56-45264).

However, these also have a gap between the cord insertion hole and the cord, and the open side forms an air flow passage like the conventional product, so it cannot be said that they are necessarily sealed, so the low frequency characteristics are also low. It was 20, 30-50Hz or more, the same as the product.

Then, the inventor measured the frequency characteristics of the condenser microphone (1) which is not listed as a catalog value (not actually measured) using a measuring device made by the inventor himself. 1Hz ~ 1 as shown
An anti-resonance characteristic (a portion having a V-shaped characteristic) occurs during 0 Hz, and it is understood that the device does not have a characteristic as a measurement sensor in a low frequency region. Originally, it was experimentally proved that physical phenomena such as the movement of a human having a slow movement characteristic of about 0.1 to 10 Hz cannot be detected using pressure fluctuation.

Means for Solving the Problems Accordingly, the present inventor has proposed the above-mentioned Primo ICEM-EM-121.
By completely sealing the bottom side of the condenser microphone, it is possible to measure up to extremely low frequency range such as 0, 1 Hz, Hz, etc., and based on that development, we propose the pressure vibration detection element of the present invention. In the configuration, a pressure-vibration detecting element provided with a circuit for detecting pressure in a bottomed cylindrical case having one end opened, via a plurality of ring-shaped insulating spacers on the open side of the case, The electret film forming the pressure-receiving surface and the opposing electrode are sandwiched over the entire peripheral portion on the open side to substantially block the air inside and outside on the open side of the case. In order to completely prevent the flow of air, a sealant is applied to seal the hole of the lead wire formed in the bottom of the case from the outside of the case.

[Operation] As described above, air flows through the open side between the ring-shaped insulating spacer and the electret film, and the small gap between the ring-shaped insulating spacer and the counter electrode, thereby completely closing the bottom side. And low frequency characteristics such as 0, 1 Hz, and 1 Hz, which could not be detected conventionally.

[Embodiment] The configuration of this embodiment will be described with reference to FIG. 1, but the description of components having the same configuration or equivalent portions as those described in FIGS. 3 to 5 will be omitted, and different portions will be described. Will be described only.

In this figure, the difference from FIG. 3 to FIG. 5 is that the hole (2a) of the case (2) in FIG.
The point (4) is completely sealed to prevent air from flowing inside and outside the case (2).

That is, the sealant (14) blocks the lead wire drawing hole (2a) of the case (2) from the outside, and completely prevents the flow of air inside and outside the case (2). As a result, frequency characteristics similar to those of the above embodiment are obtained as shown in FIG.

According to the above configuration, the frequency characteristic in the low frequency region of the condenser microphone (1) has been improved to around 0.1 Hz by eliminating the anti-resonance.
Shown in the figure.

[Effects of the Invention] As described above, the present invention has a fine air flow path on the open side of a bottomed cylindrical case having one end opened, and a lead wire drawing hole on the bottom side of the case. By completely enclosing and completely eliminating the gap, 0.1%, which is much lower than the limit of 20 to 30 Hz in the conventional condenser microphone,
There is an effect that a change in pressure fluctuation at an extremely low frequency of 10 Hz can be detected.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view of a main part of an embodiment according to the present invention, FIG. 2 is a frequency characteristic diagram of the embodiment shown in FIG. 1, FIG. 3 is an explanatory sectional view of a conventional condenser microphone, FIG. 5 is a cross-sectional view of a principal part for explaining an air leakage path of the condenser microphone shown in FIG. 3, and FIG. 6 is a frequency characteristic diagram of the condenser microphone shown in FIG. DESCRIPTION OF SYMBOLS 1 ... Condenser microphone 2 ... Case, 2a ... Hole 3 ... Circuit board 4, FET transistor 6a ... Electret film 6b ... Counter electrode, 7 ... Ring-shaped insulating spacer 14 ... Sealant

Claims (1)

(57) [Claims] 1. A pressure vibration detecting element having a circuit for detecting pressure in a bottomed cylindrical case having one end opened, wherein a plurality of ring-shaped insulating spacers are provided on the open side of the case. The electret film forming the pressure receiving surface and the opposing electrode are sandwiched over the entire peripheral portion on the open side to substantially block the air inside and outside on the open side of the case. A pressure-vibration detection element characterized in that a sealant for sealing a hole of a lead wire formed in the bottom of the case from the outside of the case is applied in order to completely prevent the flow of air inside and outside of the case.