JPS648879B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flame detection device using ultraviolet rays, and more particularly to a power-saving discharge element drive circuit for a discharge type fire detector.

Recently, various types of fire detectors have been proposed that use smoke, light, or heat generated when a fire occurs to detect and notify the occurrence of a fire at an early stage. Visible light detection elements, PbS,
There are various photodetectors that utilize infrared detection elements such as InSb or ultraviolet detection elements such as ZnS.

This invention was developed for the purpose of preventing fires through early warning by detecting minute amounts of ultraviolet light emitted from flames using discharge elements among these photodetectors.

Therefore, in the present invention, the discharge element is made by having two electrodes, an anode and a cathode, facing each other, filled with gas, and sealed with quartz glass, etc., which allows ultraviolet rays to pass through. An ultraviolet detection tube containing an ultraviolet detection element such as ZnS, which irradiates light and facilitates discharge, is used.The detection circuit including such an ultraviolet detection tube is as simple as possible and uses as few parts as possible to detect ultraviolet rays. It uses an operating circuit that increases efficiency, reduces power consumption, and operates efficiently, and uses a delay circuit gate circuit counter as the operating circuit to stabilize the circuit as an ultraviolet detection device.

That is, the present invention includes a pulse generating circuit, a circuit that boosts the generated pulse, a circuit that rectifies and charges the boosted voltage, and a circuit that detects ultraviolet rays contained in the flame by being in a state before being driven by the charging voltage. It is characterized by comprising an ultraviolet detection tube that starts discharge, and a counter circuit that digitally converts the voltage generated by the discharge, shapes the waveform, opens a gate of a gate circuit, counts, and takes out an alarm output when a certain amount is reached. It is something.

This invention will be explained with reference to the circuit configuration diagram of an embodiment shown in FIG. 1 is a relaxation oscillation circuit used as a pulse generation circuit, which is a combination of NPN transistor Tr ₁ and PNP transistor Tr _2. Transistor Tr ₁
The base of the transistor Tr 1 is connected to the junction A of the resistor R ₁ and the capacitor C _1. The emitter of the transistor Tr ₁ is connected to the transistor Tr _2.
A capacitor _C2 is connected between the collector of the transistor _Tr1 and the base of the transistor _Tr2, respectively, and the collector of the transistor _Tr2 is grounded. Further, the primary winding Ta of the step-up autotransformer T is inserted between one end of the resistor _R1 and the collector of the transistor _Tr1 . Next, one end of the secondary winding Tb of the transformer T is applied to one end of the capacitor C ₃ through the diode D ₁ .
Charge capacitor _C3 with the boosted voltage,
It is used as a discharge power source for the ultraviolet light generating tube 2. For this purpose, a resistor R ₄ is inserted between the junction of the diode D ₁ and the capacitor C ₃ and one electrode (anode) of the ultraviolet generator tube 2, and the other electrode (cathode) of the ultraviolet generator tube 2 is Resistance R from the drawer part ₅
The output is then given to the waveform shaping circuit 3a of the counter 3.

Next, the base of the transistor Tr ₂ is connected to one end of a resistor R ₃ through a resistor R ₂ and further connected to the gate circuit 3d of the counter 3 through a diode D ₂ from this junction point. In addition, resistor R ₅ , capacitor C ₃ , resistor R ₃ , and one end of capacitor C ₁ are all grounded.

The operation of the device of the present invention will be explained based on the above wiring connections.

First, in relaxation oscillator circuit 1, the NPN transistor
By combining Tr ₁ and PNP transistor Tr ₂ and choosing a battery as the device power supply, the device is configured to reduce power consumption as much as possible, is less susceptible to load effects, consumes less power, and operates stably at low cost. Ru. First, when the DC power is turned on, the connection point A between the resistor R ₁ and the base of the transistor Tr ₁ is at 0 potential, and the transistors Tr ₁ and Tr ₂ are off.

Next, the capacitor _C1 is charged by the DC power supply voltage (battery) through the resistor _R1 , the potential at point A rises, transistor _Tr1 is turned on (saturated), and the potential at point B of the collector of transistor _Tr1 is The base potential of the transistor Tr ₂ also drops via the capacitor C ₂ , and the transistor Tr ₂ is turned on. When the transistors Tr ₁ and Tr ₂ are turned on, the charge in the capacitor C ₁ is rapidly released through these two transistors, and the potential at point A returns to the original 0 potential, turning off the transistors Tr ₁ and Tr ₂ one after another. do. By repeating the above operations, a relaxation pulse voltage of about one time per second is obtained from point B as the output of the relaxation transmitting circuit 1, as shown in FIG. 2B. Figure 2 A is A
The waveform of the points is shown. The pulses obtained in this way are applied to the primary winding Ta of the step-up transformer T and induced to the secondary side, and the step-up voltage generated in the secondary winding Tb is rectified by the diode _D1 . Capacitor _C2 is charged. On the other hand, part or all of the ultraviolet inspection tube 2 set in the device is exposed to the outside air, and when a fire occurs nearby, the ultraviolet rays contained in the flame hit the tube and are stimulated, causing the inside of the tube to be stimulated. As the resistance decreases, discharge finally begins with the help of the charging voltage of the capacitor _C3 , and a voltage drop corresponding to the discharge of the ultraviolet detection tube 2 is taken out as a detection voltage across the resistor _R5 . As long as the flame continues to hit the ultraviolet detection tube 2, the above-mentioned capacitor C ₃
The discharging and charging of is repeated, and when the capacitor _C3 finishes discharging, the ultraviolet detection tube 2 also stops, and the capacitor _C3, which is charged again with the voltage boosted from the pulse voltage from the relaxation oscillation circuit 1, reaches a predetermined voltage. The operation of reaching the operating voltage of the ultraviolet detection tube 2 and starting the discharge of the capacitor C3 is repeated, and each time the ultraviolet detection tube ₂ discharges, a voltage is generated from the resistor _R5 , which is applied to the counter circuit 3. It is counted as follows. The counter circuit 3 first has an analog-to-digital conversion circuit 3a that converts the voltage across the resistor _R5 into a digital signal for counting.
After converting it to a digital signal of 0, the waveform/shaping circuit 3c performs waveform/shaping with a width of approximately 200 m/s.At this time, in order to prevent the counter from malfunctioning,
Via one-shot multivibrator 3b, approx.
A time delay of 4 seconds is applied.

Furthermore, when the ultraviolet detection tube 2 is discharged, it recedes, making it difficult to stop the discharge completely, and once it is discharged, it takes a considerable amount of time to start discharging again due to the presence of the capacitor C ₃ and the ultraviolet detection tube 2. As a result, the output discharge waveform is poor, and the discharge is also caused by static electricity, and even a single discharge in such a case may cause an alarm to be issued immediately, making it unstable. Therefore, stabilization is achieved by shaping the waveform and combining two or three successive pulses into one for a short period of time, so that any number of pulses within 200 m/s are counted as one pulse. After a time delay of about 4 seconds, the one-shot multivibrator 3b outputs an output to the gate circuit 3d, which opens the gate and performs sampling for about 11 seconds. Therefore, about 11 seconds
During the sampling time of , the pulses whose waveforms have been shaped by the waveform shaping circuit 3c are counted by the counter 3e, and when the set arbitrary count number is reached, the alarm circuit 4 is activated, assuming that the flame is continuously generated. It generates an alarm output. Furthermore, alarm circuit 4
It includes a delay flip-flop and a multivibrator to give an alarm of about 15 seconds, that is, a blink of about 200 ms, which can cause an LED display or an electronic buzzer to sound. A part of the output of the gate circuit 3d is connected to the dividing point G, which divides the resistance between the base and ground of the transistor Tr ₂ into the resistances R ₂ and R ₃ via the diode D ₂ connected to the cathode side. By connecting the cathode side of the diode _D2 to L level, the potential at the dividing point G becomes close to 0, and the time constant is set by the capacitor _C2 and the resistor _R2.
The oscillation period becomes faster and the cathode side of diode _D2 is set to H level.
The time constant is configured by C ₂ R ₂ + R ₃ to slow down the oscillation period, and a control signal is given to point G to increase the detection efficiency of ultraviolet rays while the gate is open, thereby changing the discharge frequency of the discharge element. The oscillation period is controlled by the difference. In addition, in order to stabilize the circuit, prevent false alarms, and enable complete operation, a large amount of pulses are detected from continuously burning fires, self-discharge from ultraviolet detection tubes, and sporadic occurrences due to natural radioactivity or static electricity. The counter circuit 3 is configured with a one-shot multivibrator 3b, a gate circuit 3d, and a counter 3e in order to identify a small amount of pulsed discharge output.As a result, power consumption is reduced compared to conventional fire detectors. It enables the use of commercially available dry batteries, dramatically expanding the range of applications.

As described above, according to the present invention, ultraviolet rays contained in flames are quickly detected using an ultraviolet detection tube and its operating circuit, so that it is very effective as a small and lightweight fire detector.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram of an embodiment of the device of the present invention, and FIG. 2 is a normal waveform diagram at point A and point B of the multivibrator 1. In the figure, 1 is a multivibrator circuit, 2 is an ultraviolet detection tube, 3 is a counter circuit, 3a is an analog-to-digital conversion circuit, 3b is a one-shot multivibrator, 3c is a waveform shaping circuit, 3d is a gate circuit, and 3e is a counter. , 4 are alarm circuits, D ₁ and D ₂ are diodes, Tr ₁ and Tr ₂ are transistors, R ₁ to R ₅ are resistors, and C ₁ , C ₂ and C ₃ are capacitors.

Claims (1)

[Scope of Claims] 1. A pulse generating circuit, a circuit that boosts the generated pulse, a circuit that rectifies and charges the boosted voltage, and a circuit that detects ultraviolet rays contained in a flame that is brought into a state on the verge of being driven by the charging voltage. The ultraviolet detector tube starts discharging when
A flame detection device using ultraviolet rays, comprising a counter circuit that outputs an alarm output when a certain amount is reached. 2. The flame detection device using ultraviolet rays according to claim 1, wherein a time delay circuit is interposed in the waveform shaping. 3. The invention according to claim 1, further comprising an oscillation cycle control circuit which applies an oscillation cycle control signal to the pulse generation circuit by transmitting the discharge output of the ultraviolet detection tube through a time delay circuit to open the gate circuit. Flame detection device using ultraviolet light. 4. The flame detection device using ultraviolet rays according to claim 1, wherein the pulse generation circuit uses a relaxation oscillation circuit including one NPN transistor and one PNP transistor.