JPS59160730A - Apparatus for detecting gas temperature - Google Patents

Abstract

PURPOSE:To make the temp. detection of working space, etc. effective by utilizing the antiresonance phenomenon caused by a Helmholtz type resonator and a sound interference body. CONSTITUTION:The Helmholtz type resonator 4 is contained in a case 2 of whole of the apparatus of plastic. The resonator 4 has a sound releasing hole 6 and a self-exciting type vibrator 8 is attached to the lower end surface. A sound interference body 10 consisting of metallic plate is provided opposingly to the hole 6. In this case, the position of the body 10 is set so that the vibration of the body 8 is stopped completely at the reference temp.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to acoustic phenomena, particularly anti-resonance phenomena caused by a Helmholtz-type resonant container and a sound interference body;
This invention relates to a gas temperature detection device using a gas temperature detection device.

In this specification, anti-resonance refers to a system in which a sound interference body is opposed to the sound emission hole of a Helmholtz type resonant container equipped with an oscillator, and at a specific position of the interference body or at a specific oscillation frequency. This is a phenomenon in which the oscillation of the oscillator almost completely stops and no sound is generated from the resonant container.

It has long been known that physical properties related to acoustic phenomena, such as the speed of sound, change depending on temperature. The present inventors investigated temperature detection using acoustic phenomena and discovered the following phenomenon.

An oscillator is attached to a Helmholtz-type resonant container and oscillates at a constant frequency. Next, when a sound interference body such as a metal plate is placed facing the sound emitting hole of the resonance container, the oscillation stops at a specific position and no sound is generated.

Conversely, if the position of the sound interfering body is kept constant, oscillation stops at a specific frequency and no sound is generated. If we refer to this phenomenon as anti-resonance, the range of the position and frequency of the interfering body in which anti-resonance occurs is extremely narrow, and anti-resonance is greatly affected by even the slightest change in these factors. Furthermore, if the oscillation frequency is kept constant, there is only one position of the interfering body where anti-resonance occurs. In contrast, sharp resonance does not occur no matter how the position of the interference body is changed.

The cause of anti-resonance is not clear, but
This seems to be because standing waves cannot exist due to interference between the traveling wave from the oscillator and the reflected wave from the interfering body.

Incidentally, anti-resonance is strongly influenced by temperature, and the conditions under which anti-resonance occurs change as the temperature of the gas changes. This is thought to be because the speed of sound depends on temperature. In order to maintain anti-resonance when the temperature rises, it is necessary to shift the position t of the interference body away from the sound emitting hole, or to shift the frequency of the oscillator to a higher frequency side.

The purpose of this invention is to provide a gas temperature detection device using anti-resonance, in which a sound interference body is provided opposite the sound emitting hole of a Helmholtz type resonant container equipped with an oscillator, and the gas temperature can be detected using anti-resonance. The gas temperature is detected from the change in anti-resonance conditions caused by the change.

Means for detecting changes in anti-resonance conditions include changes in the impedance of the oscillator, changes in the sound pressure of the sound from the resonant container or vessel, changes in the oscillation frequency that cause anti-resonance, and changes in the sound pressure. A change in the position of the interference body may also be used.

Each embodiment of this invention will be described below.

In Figure 1, (2) is the entire plastic case of the device, inside which is a Helmholtz-type resonance vessel (4).
to accommodate. The resonant frequency of this resonant container (4) is approximately 4.
7KHz, diameter 5mm, wall thickness 1mm sound emitting hole (6)
have. At a position two degrees away from the lower end surface of the sound emission hole (6) (hereinafter, the vertical direction is shown based on the top and bottom in the figure),
A self-oscillating type oscillator (8) with an oscillation frequency of about 4.7 KHz is attached. The oscillator (8) is mounted on a node support, and its structure is made by laminating a barium titanate piezoelectric ceramic plate on a metal plate.

Opposite the sound emitting hole (6), at intervals of about 3.5 mm, diameter 2
A sound interference body (10) made of a metal plate of 0.0 mm is provided.

Anti-resonance is greatly affected by the position of the interfering body αQ, and a change in position of about 0.1 can cause a large change.
For example, a sound pressure change of 20 dB or more occurs. Therefore, for example, the position of the interference body 00 is set so that the oscillation of the oscillator (8) completely stops at the reference temperature. Although the specific interference body α0 has been described here, it may be anything that reflects the sound from the sound emission hole (6) and causes anti-resonance; for example, the top surface of the case (2) may also be used as the interference body. You can also do that. In that case, one opening α at the top of the case (2) is closed and sound passage holes are provided in the other parts.

A sound absorbing material layer α made of foamed polyurethane or the like with a thickness of approximately 2 mm is provided on the bottom surface of the resonance container (4).
absorbs reflected sound from the bottom of the The Helmholtz-type resonant container (4) does not generate standing waves only between the upper part of the container (4) and the oscillator (8);
) and the bottom of the container (4), or between the bottom of the case (2) and the oscillator (8) if the bottom of the container (4) is too thin to be of any use as a sound reflector. This also causes standing waves. If a standing wave is generated in such a portion, anti-resonance will not occur no matter what type of interference body α0 is used. In order to polarize such standing waves, the sound absorbing effect of a sound absorbing material may be used, or the distance between the oscillator (8) and the reflecting surface may be increased, for example, to 40 mm or more in this embodiment. The sound absorbing material is not limited to the position shown here, but may be provided at any position that can absorb the standing waves below the oscillator (8). For example, if the bottom surface of the resonance container (4) is very thin and the sound reflection effect is low, it may be provided at the bottom of the case (2).

FIG. 2 shows the detection circuit of this embodiment. The main electrode (8a), the return electrode (8b), and all electrodes (8) of the oscillator (8)
c) is incorporated into a Hartley oscillator circuit with a grounded emitter. A DC blocking capacitor (
A detection resistor (RL;) is connected through C1), and the oscillation current flowing through the oscillator (8) is extracted.

A comparison circuit (C) is connected to the detection resistor (RL) via an amplifier circuit (A) and an A-D converter (F), and the output of the variable output power supply (G) is compared with the divided reference potential. .

The output terminal Q point of the comparison circuit (c) is connected to an air conditioner or a central monitoring device (not shown) to control these devices.

In addition, the comparison circuit (A) is connected to a variable output power source), and the output of the variable power source (G) is controlled by the output of the comparison circuit (C). This variable power supply member makes the first transistor 02 conductive when the output of the comparator circuit @ is positive, and directly applies the electromotive force of the battery power supply (b) to the oscillation circuit (a). Further, when the output of the comparison circuit (c) is O, the second transistor (g) is made conductive, and the voltage stabilized by the Zener diode (c) is applied to the oscillation circuit (e).

Note that although a specific embodiment has been described here, various modifications can be made to each part of the embodiment.

For example, by modifying the Helmholtz-type resonant container (4) and connecting a pipe to the sound emission hole (6), there is no interference with the tip of the pipe.
Even if the QOs are placed opposite each other, anti-resonance can be produced by selecting the diameter and length of the pad. In addition, in order to clearly notify the user, changes in the sound pressure of the sound from the resonant container (4) due to changes in anti-resonance conditions are artificially increased using a comparator circuit (a), a variable output power source (7), etc. However, instead of these, a normal fixed output power source may be used as the power source for the oscillation circuit. The oscillator (8) may be replaced with a separately excited type oscillator (g), in which case BE Pierce type oscillation using a crystal oscillator (6) shown in Figure 3 instead of the oscillation circuit. Use circuits, etc. Then, connect the output terminal (goods) to the amplifier circuit (a), and connect the terminal 06)
Connect to the output end of the variable power supply (G).

Next, the operation of this embodiment will be explained. Set the position of the interference body αQ so that anti-resonance occurs at the reference temperature, and apply a low voltage, e.g. 2V, from the variable power supply (to).
, is supplied to the oscillation circuit to cause the oscillator (8) to oscillate. At the reference temperature, due to anti-resonance, the oscillator (8
) does not oscillate, producing neither sound nor oscillating current. When the temperature changes, the oscillator (8) gradually starts to oscillate, and the sound pressure of the generated sound and the oscillation current increase. The effect of temperature change occurs almost symmetrically around the reference temperature, and both increases and decreases in temperature give ml-like effects. However, while the temperature change from the reference temperature is small, the output of the variable power supply is small, so the generated noise and oscillation current are small. If the temperature change exceeds the allowable range, the output of the comparator circuit (a) becomes positive,
The output of the variable power supply (to) increases, for example to about 12V,
The sound pressure of the generated sound increases significantly and a notification is given. Furthermore, external devices such as air conditioning equipment and central monitoring equipment are controlled by the output of the comparison circuit (1), and necessary measures are taken.

Next, FIG. 4 shows the detection results in the embodiment shown in FIGS. 1 and 2. The horizontal axis of the figure is the reference temperature, here 20°C.
It shows the temperature difference from 1. The solid line pt in the figure shows the sound pressure at a point 1 m in front of the case (2) (the ambient sound level was about 80 dB), and the dashed line p2 shows the constant voltage applied to the oscillation circuit (a). did! Indicates the sound pressure of Similarly, solid line ■1
indicates the voltage applied to the detection resistor (RL), and the dashed line v2 indicates the voltage applied to the detection resistor (RL) when a constant voltage is applied to the oscillation circuit.

As explained above, the present invention provides a gas temperature detection device using anti-resonance, which is effective for detecting temperature in living spaces such as living rooms and bathrooms, and working spaces such as mines and greenhouses. It is something. It can also be used to detect flame from an abnormal rise in gas temperature. Furthermore, if the question is whether the temperature of the gas is within a specific range and the direction of temperature change is important, it is possible to detect whether the temperature change is within an allowable range from the presence or absence of anti-resonance. If it is necessary to know the direction in which the temperature is increasing, either the lower limit temperature or the upper limit temperature may be set as the anti-resonance point.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of the embodiment, FIG. 2 is a circuit diagram of the embodiment, FIG. 3 is a main circuit diagram of a modified example, and FIG. 4 is a characteristic diagram showing detection results. αQ...interference body, (a), 0*...oscillation circuit, (c)...comparison circuit, (g)...variable output power supply. Patent applicant: Figaro Giken Co., Ltd. Representative: Ei Chiba

Claims (1)

[Claims] (1) The oscillator incorporated in the oscillation circuit is mounted in a Helmholtz-type resonance container, and a sound interference body is provided opposite the sound emission hole of the resonance container, so that the sound interference body is caused by a change in gas temperature. A gas temperature detection device configured to detect gas temperature from a change in anti-resonance conditions between the resonance vessel and the resonance vessel.