JPH02143151A - Fire sensor - Google Patents

Abstract

PURPOSE:To reduce the thickness of the device and to utilize the electromotive voltage of a piezoelectric element itself and eliminate the need for a voltage source by composing the sensor of the piezoelectric element which generates the electromotive voltage by abrupt temperature variation and an alarm which generates an alarm with the signal sound of the element or control means which stops equipment. CONSTITUTION:The fire sensor main body consists of the piezoelectric element 1, a resistance 2, a buzzer 3 as the alarm, the equipment 4, and the control means 5. In a temperature stable state of T deg.C, surface charges and floating charges are in an electrically neutral state in consideration of the surface loads of the element 1 and floating loads in air before and after the abrupt temperature variation is caused and no current flows even when the resistance 2 is connected outside. When, however, the abrupt temperature variation (T+DELTAT) deg.C is caused, charges nearby the surface of the element 1 can not follow up the variation and charges are unbalanced to make a current flow through the resistance 2, so that the alarm 3 sounds.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a security-related sensor for preventing fires and the like.

BACKGROUND OF THE INVENTION Conventionally, this type of fire sensor has been configured to use a bimetal contact type as a heat detection element as shown in FIG. 6, or to use pressure on a diaphragm due to geothermal expansion to generate an alarm or stop the equipment.

Heat detection element 9, bimetal 10, lead wire 11 on wall surface 8
is configured and installed. The device is configured to stop when the contacts open due to heat.

Problems to be Solved by the Invention In the above-mentioned configuration, the bimetal contact type or diaphragm configuration has the problem that the sensor itself is very large and would spoil the aesthetic appearance if installed on a wall or the like.

Means for Solving the Problems In order to solve the above problems, the fire sensor of the present invention uses a piezoelectric element.

Function The above configuration has the function of generating an electromotive voltage when a sudden temperature change is applied to both ends of the piezoelectric element.

EXAMPLE Hereinafter, an example of the present invention will be described based on the accompanying drawings.

FIG. 1 is a block diagram of the main body of an embodiment of the present invention. 1 is a piezoelectric element, 2 is a resistor, 3 is a buzzer which is an alarm, 4 is a device, and 5 is a control means.

FIG. 2 is a diagram showing the surface charge of the piezoelectric element 1 and the state of floating 'tlT1 charges in the air before and after a sudden temperature change is applied.

In a stable temperature state of T'C, the surface charges of the piezoelectric element 1 and the floating charges in the air are in an electrically neutral state, and no current flows even if the resistor 2 is connected externally.

However, when a sudden temperature change is applied, charges near the element surface cannot follow the temperature change, resulting in charge imbalance. Therefore, when the resistor 2 is connected externally, an instantaneous current flows, and a voltage is generated across the resistor and observed. The observed waveform diagram is shown in Figure 3.

FIG. 4 is a frequency spectrum diagram before and after applying a sudden temperature change.

A is a spectrum diagram before a sudden temperature change is applied, and C is a spectrum diagram after it is applied.

From this figure, a voltage difference of about 100 times or more can be observed before and after a sudden temperature change is applied in the 0 to 10 Hz band. A is several mV, and C is 2 to 3 ■. By configuring a filter for this frequency band and inputting it to the control means 5, the presence or absence of a fire can be determined from the voltage generated by the piezoelectric element 1. This causes the alarm 3 to sound or the device 4 to be shut off.

FIG. 5 is a diagram showing the piezoelectric element 1 installed on a ceiling wall in a house. 6 is a metal plate, and 7 is a holding jig that supports the metal plate. Note that the piezoelectric element 1 is bonded to a metal plate with an adhesive.

Effect of the invention As described above, the present invention provides the following effects.

(1) The piezoelectric element has a very simple structure and can be installed very compactly on a ceiling wall without taking up much space, without detracting from the aesthetics.

(2) Since the electromotive force of the piezoelectric element itself is used, there is no need for a special voltage source, and the construction is easy as only two lead wires are required from the installation location.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the main body configuration of a fire sensor according to an embodiment of the present invention, Fig. 2 is a diagram showing the charge state of the piezoelectric element of the fire sensor, and Fig. 3 is a diagram of observed waveforms of the piezoelectric element of the fire sensor. , 4th
The figure is a spectral waveform diagram of the piezoelectric element of the same fire sensor.
The figure is a sectional view of the installed fire sensor, and FIG. 6 is a block diagram of the main body of the conventional fire sensor. 1...Piezoelectric element, 3...Alarm, 4.
...Equipment, 5...Control means. Name of agent: Patent attorney Shigetaka Awano (1 person) too

Claims (1)

[Claims] A fire sensor that has a piezoelectric element that generates an electromotive force due to a sudden temperature change, and an alarm that emits an alarm sound or a control means that stops equipment based on a signal from the piezoelectric element.