JPS59144991A - Gas leak alarm - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a gas leak alarm.

Conventional configuration and its problems In a gas leak alarm that uses a metal oxide semiconductor as a gas sensing element, when the power source is turned on after being left unenergized for a long period of time, the unnecessary components adsorbed on the sensitive body burn, as shown in Figure 1. As shown in Fig. 2, the humidity of the sensitive body increases, and the resistance value of the sensitive body falls below the alarm setting resistance value R1 as shown in Fig. 2. During the initial operating time T, which is called the initial malfunction, it is generally necessary to prevent the malfunction T. An operation prevention timer is provided so that no alarm signal is issued during this initial operation time T. However, if a long time is required for the initial operation time T in order to achieve stable operation, the gas leak alarm cannot be used during that time, causing problems in inspection work and the like.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a gas leak alarm that eliminates the above-mentioned problems and can improve workability such as inspection in a shorter initial time.

Structure of the Invention The present invention eliminates gas leakage in a short initial operation time by controlling the heater voltage to reduce the temperature of the sensitive element for a certain period of time after power is turned on, so that the resistance value of the sensitive element decreases when it comes into contact with flammable gas. Alarms can be provided.

DESCRIPTION OF THE EMBODIMENTS FIG. 3 shows the relationship between the temperature of the sensitive body and the initial operating time of 1°. As is clear from this figure, the initial operating time T can be shortened by increasing the temperature within a range that does not cause deterioration of the sensitive body.

The present invention has been made based on this point, and an embodiment of the present invention will be described based on FIG. 4.

In the figure, 1 is a DC power supply, and 2 and 3 are resistors, which determine the alarm setting level B. 4 is a sensitive body made of a metal oxide whose resistance value decreases when it comes into contact with combustible residue; 6 is a thermocouple embedded inside the sensitive body for detecting the temperature of the sensitive body; 6 is a sensor for keeping the sensitive body 4 at a predetermined temperature; The peak voltage is controlled by the heater voltage control circuit 8. 9 ( is connected to the sensitive body 4 through a resistor, and is used to change the potential at point A according to the resistance value of the sensitive body 4. 10 is a heater voltage control circuit 80 that controls the heater voltage control circuit 80 for a certain period of time after the power is turned on. A timer for adjusting the voltage; 11 is a voltage discrimination circuit that compares the potentials at point A and B and detects that the potential at point A has changed; 12 is a voltage discrimination circuit 11
The lamp buzzer drive circuit drives the lamp 13 and the buzzer 14 to warn of gas leakage based on the output of the lamp buzzer 13. Reference numeral 13 is an initial malfunction prevention timer for preventing an alarm for a certain period of time after power is turned on.

In the present invention, the voltage of the heater 6 is increased by the timer 10 for a certain period of time immediately after the sensing element 4 is activated, so that the temperature of the sensing element 4 is raised from a steady state. In this way, by burning the unnecessary components attached to the sensitive body 4 in a short time, the initial operating time T is shortened.

In addition to the effects of the invention, according to the present invention, the initial malfunction time can be shortened, and the prevention timer can also be shortened, so that the inspection time after several cycles can be shortened.

[Brief explanation of the drawing]

Figures 1 and 2 are characteristic diagrams showing the relationship between the time after power is applied to the sensitive element, the resistance value of the sensitive body, and the temperature of the sensitive body, and Figure 3 is a characteristic diagram showing the relationship between the temperature of the sensitive body and the initial operating time. Figure, 4th
The figure is a circuit diagram showing an embodiment of the present invention. 4...Sensor, 6...Heater, 8...
...Heater voltage control circuit, 10...Timer. Name of agent: Patent attorney Toshio Nakao and one other person Wk
l Figure V source input shunryo ginma (8) Figure 2 Figure 3 weak Q, soo 6o. Looking down cliff (Fig. 4)

Claims (1)

[Claims] The sensor comprises a metal oxide sensitive body whose resistance value decreases when exposed to flammable gas, a heater that maintains the sensitive body at a predetermined temperature, and a heater voltage control circuit that applies a predetermined voltage to the heater. A dregs leakage alarm, characterized in that the heater is controlled by the heater voltage control circuit in order to make the temperature of the sensitive body higher than a steady state for a certain period of time after the body is operated.