JPH02128298A - Detector - Google Patents

Abstract

PURPOSE:To automatically detect the clogging of an insectrepelling net by providing a detecting means to detect the change of the resonance frequency of a detecting room and sensing the status of an opening from the detected output of this detecting means. CONSTITUTION:Openings 4 for guiding smoke to the inside of a detecting room 1 are provided around the detecting room 1, and these openings 4 are covered with an insectrepelling net 5. A sound emitting hole 7 is drilled on the internal ceiling surface of the detecting room 1, a disk-shaped sounding body 8 is fitted from the rear face of the internal ceiling surface so that the sounding body 8 can block this sound emitting hole 7, and this sounding body 8 is sounded by a driving circuit. Since the driving circuit easily starts resonance when the resonance frequency of this sounding body 8 coincides with the resonance frequency of the detecting room 1, the clogging of the insectrepelling net 5 can be detected by detecting the change of the oscillation current of the driving circuit after arbitrarily setting oscillation conditions. Thus, the clogging of the insectrepelling net 5 can be automatically detected.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a detector for detecting smoke, gas, etc. in the environment, and in particular a detector that can automatically confirm the normality of the detection function. Regarding.

``Prior Art'' In the above-mentioned detectors, it is best to detect smoke or gas ``7, which is the object to be detected, by flowing it into the detection chamber through an opening. In order to prevent dust or insects other than the object to be detected from entering the sensor and interfering with the detection function, a fine mesh insect repellent wIf!: is provided at the opening.

[Problems to be Solved by the Invention] However, although installing an insect repellent net as described above is certainly effective in preventing the invasion of insects, etc., the net becomes clogged due to the adhesion of dust, etc. The inflow of the object to be detected into the room may be obstructed, resulting in a decline in the scissoring function. Conventionally, when the detection function deteriorates, we visually check to see if the insect screen is clogged, and if it is, we clean or replace the insect screen. However, this visual confirmation of clogging requires that the insect screen be at least visible, which is quite a troublesome task.

Therefore, it would be good if the clogging could be detected automatically without any manual effort, but conventionally there was no means for automatically detecting the clogging.

Means for Solving the 1N Problem] Therefore, the detector according to the present invention is provided with a detection means for detecting a change in the resonant frequency of the detection chamber, and the state of the opening is detected from the detection output of this detection means. The present invention solves the above problems and provides means for automatically detecting clogging.

[Operation] The resonant frequency of the detection chamber having the opening can be determined from the Helmholtz equation. That is, assuming that the acoustic capacitance determined mainly by the volume of the detection chamber is C1 and the inertance determined mainly by the area of the opening and the thickness of the detection chamber wall is M, resonance occurs due to this acoustic capacitance and inertance, and its resonant frequency f is expressed by the following formula. Represented by

Therefore, if the mesh of the insect screen covering the opening becomes clogged, the area of the opening will equivalently become smaller, which will change the inertance, which in turn will cause a change in the resonant frequency.

Therefore, by detecting a change in the resonance frequency of the detection chamber, the condition of the opening can be indirectly detected.

[Embodiment] An embodiment of the detector according to the present invention will be described based on the drawings.

This invention can be applied to almost all types of detectors having a detection chamber, but this embodiment applies to smoke flowing into the detection chamber. Scattered light smoke detection detects the presence of smoke by detecting the scattered light caused by the smoke. An example of application to the deaf is shown.

That is, a light source 2 and a light receiver 3 are installed on the internal ceiling surface of the detection chamber 1.
The light receiver 3 is arranged so that the light from the light source 2 is not directly incident thereon. An opening 4 for introducing the metal into the filling chamber is provided around the detection chamber 1, and this opening 4 is covered with an insect repellent 11115. The entire detection chamber 1 is covered with an outer cover 6.

In the scattered light type smoke detector configured as described above, the smoke that flows into the detection chamber 1 through the insect screen 5 and the opening 4 is
Scatter the light from the light source 2. By detecting this scattered light with the light receiver 3, the presence of smoke is detected.

A sound emitting hole 7 is bored in the internal ceiling of the detection chamber 1.
A disc-shaped sounding body 8 is attached so as to close the sound emitting hole 7 from the back side. This sounding body 8 is formed by pasting a piezoelectric ceramic 10 on a metal plate 9, and is generated by a drive circuit. The specific configuration of the drive circuit is, as shown in the circuit diagram of FIG.
It is a self-oscillating circuit that is a modification of the common emitter Hartley oscillator consisting of a .14.

When the resonance frequency of the sounding body 8 driven by this drive circuit matches the resonance frequency of the detection chamber 1, the drive circuit easily starts oscillating. This oscillation can be achieved by appropriately setting the oscillation conditions by adjusting the voltage supplied to the drive circuit, etc.
It stops under the influence of the change in the resonance frequency of the detection chamber 1.

Whether the drive circuit is oscillating or not can be easily detected by detecting the current flowing to the drive circuit. Normally, this '8 flow increases significantly when oscillation starts compared to before the start. However, by setting the oscillation conditions appropriately and detecting the change in the oscillation current of the drive circuit, it is possible to detect that the insect screen has become clogged.

-1- In the embodiment described above, when the insect screen becomes clogged, the oscillation or stop is assumed, but depending on the setting of the oscillation conditions, it is also possible to make the oscillation start when the insect screen becomes clogged. It is possible. Furthermore, since keeping the drive circuit operating all the time increases power consumption, it is preferable to operate it only when it is necessary to check whether the insect screen is clogged.

Furthermore, the mounting position of the sounding body 8 is not limited to the internal ceiling surface of the detection chamber 1, and can be determined at any position inside the detection chamber based on the arrangement relationship with other Ris equipped with the detector. .

In the embodiment F, the opening of the detection chamber is covered with an insect screen, but the present invention can also be applied to an instrument in which the detection chamber itself is made of a net.

[Effects of the Invention] As described above, the detector according to the present invention is provided with a detection means for detecting a change in the resonant frequency of the detection chamber, and the condition of the opening is detected from the detection output of this detection means. , clogging can be detected automatically without the need for one person to use the furnace.

Therefore, clogging detection can be performed automatically or constantly or periodically, and the reliability of the detector can be improved.

[Brief explanation of the drawing]

The drawings show an embodiment of a detector having a function detection device according to the present invention, and FIG. 1 is a longitudinal sectional view thereof, and FIG. 2 is a circuit diagram of a drive circuit.

Claims (2)

[Claims] (1) In a detector that detects a detection object such as smoke or gas flowing into a detection chamber from the outside through the opening, a detection means for detecting a change in the resonant frequency of the detection chamber. A detector is provided with a detection means, and detects the condition of the opening from the detection output of the detection means. (2) The detector according to item 1, wherein the detection means comprises a sounding body provided in a detection chamber and a drive circuit for driving the sounding body.