JPS6162716A - Safety device of burning apparatus - Google Patents

Abstract

PURPOSE:To contrive to improve the safety by performing the steady detection of burning by a method wherein a fuel is supplied intermittently with the designated frequency to a burner and burnt, then the burning condition is detected by the alternating current component of a burning flame. CONSTITUTION:A fuel is supplied from a fuel tank 1 to a fuel supplying means 2, while the fuel supplying means 2 is provided with a fuel pump 3 which is able to supply intermittently the fuel. Thereby, the fuel is supplied intermittently to a burner 4 with a frequency (about 10-50Hz) having an extent without affecting the burning. A flame detecting sensor 5 receives a light quantity according to the burning quantity of the burner 4, the light quantity is sent to a flame detecting circuit 6 as an electrical signal. The flame detecting circuit 6 is provided with a amplifying part for amplifying the signal of the flame detecting sensor 5 and a filter part for removing the direct current component, the calibrated signal judges whether it is the normal burning or not, and the fuel supplying is controlled. The flame detecting circuit 6 judges whether it is the normal burning based on that the signal contains the alternating current component or not, accordingly, the judging is not affected by the variation of the direct current component generated by the scattering of the flame detecting sensor 5, the variation with time, the assembly tolerance error and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a safety device for a combustion apparatus that uses oil, gas, etc. as fuel, and that detects the combustion state and safely performs combustion.

BACKGROUND OF THE INVENTION In a conventional safety device for a combustion appliance of this type, fuel is sent from a fuel tank 16 to a fuel supply means 17, as shown in FIG. Then, a certain amount of fuel is supplied to the burner 18 and burned. The state of the burner flame is detected by a flame detection sensor 19, and the detection signal is sent to the flame detection circuit FIlr5. In the flame detection circuit, a flame detection signal as shown in FIG. 5 is obtained depending on the amount of combustion. The flame detection signal appears as a signal of magnitude S1 or S2 depending on the fuel supply amount. A certain threshold value T for this Sl or S2
If it is larger than H, it is normal combustion, and if it is smaller, it is a misfire!
The PI refused.

Problems to be Solved by the Invention In the conventional means, the state of the flame is determined based on the magnitude of the flame detection signal 81 or S2, and therefore the following problems arise due to disturbances. Despite the same amount of combustion, the magnitude of the flame detection signal S changes due to variations in the flame detection sensor, changes over time, and assembly errors. That is, even though the combustion is normal, the relationship between the flame detection signal S and the flame threshold value TH may result in a misfire being determined. Even though there is a misfire in correspondence, it is sometimes considered normal combustion. Furthermore, in the case of a short-circuit failure or an open failure of the flame detection sensor,
There is a danger that the flame detection signal will be at the power supply potential or ground potential, and the 03 operation will occur despite the failure.

SUMMARY OF THE INVENTION The present invention overcomes the problems of the prior art by delivering a fuel supply to the burner intermittently at a predetermined frequency, as shown in FIG. The flame detection sensor sends a signal with a frequency corresponding to the amount of combustion of the burner to the flame detection circuit. The flame detection circuit converts this signal into a signal containing only the alternating current component, excluding the direct current component.

This signal is smoothed by an integrating circuit. This voltage controls the amount of fuel supplied.

Operation With this configuration, when a fuel supply amount as shown in FIG. 2 is sent to the burner, an alternating current signal as shown in FIG. 3 appears on the flame detection circuit. Since the flame detection circuit determines whether or not combustion is normal based on whether this signal contains an AC component, it has no effect on changes in the DC component that occur due to variations in the flame detection sensor, changes over time, assembly errors, etc. It has the effect of not being affected by

EXAMPLE An example of the present invention will be described below with reference to FIG. Fuel is supplied from a fuel tank 1 to a fuel supply means 2. The fuel supply means 2 includes a fuel pump 3 that can intermittently supply fuel, and thereby intermittently supplies fuel to the burner 4 at a frequency (about 10 to 30 Hz) that does not affect combustion. The flame detection sensor 5 receives an amount of light depending on the amount of combustion of the burner 3. The amount of light is sent to the flame detection circuit 6 as an electrical signal. The flame detection circuit 6 has an amplification part that amplifies the signal from the flame detection sensor 5 and a part of a filter that removes a DC component, and uses this corrected signal to determine whether or not combustion is normal and to control fuel supply. .

FIG. 6 shows an example of a flame detection circuit. The signal from the flame detection sensor is sent to the transistor 9 and amplified. A capacitor 10 removes the DC component and converts the signal into a signal containing only AC components. The capacitor 11 smoothes this AC component signal by charging and discharging with the resistor 12. This smoothed voltage causes the transistor 13 to operate, and accordingly the relay 14 operates and the fuel/supply valve 15 is controlled. When only a constant voltage (DC component) is applied to the flame detection circuit, the DC voltage is removed by the capacitor 7, the transistor 13 is turned off, and the fuel supply valve is stopped. For example, if a flame detection sensor has a short-circuit or open failure,
Only the DC component signal becomes available, and the fuel supply valve stops. Furthermore, since it does not depend on the DC component, the flame detection sensor may vary.
There is no effect due to changes over time. Although the above description describes the basic principle of the present invention, other means may be used for the flame detection means and the flame detection circuit.

For example, if the flame detection sensor contains an AC component other than the AC component of the fuel supply means due to disturbance, the flame detection circuit may include a filter circuit that detects only the main AC component of the fuel supply means.

Effects of the Invention As described above, the safety device for combustion appliances of the present invention provides the following effects.

Fuel is intermittently sent to the burner at a predetermined frequency for combustion.
Since the combustion state is detected using the alternating current component of this flame, it has the effect of eliminating the effects of changes in the direct current component due to disturbances, and completely eliminates the effects of changes in the direct current component due to variations in the flame detection sensor, changes over time, and assembly errors. Since no combustion is detected, combustion detection can be performed reliably, improving safety. Furthermore, there are no assembly errors in the product manufacturing process, and there is no need for troublesome fine adjustments.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a safety device for a combustion appliance according to an embodiment of the present invention, Fig. 2 is a characteristic diagram showing the amount of fuel supplied to the burner, and Fig. 3 is a characteristic diagram showing the amount of fuel supplied to the burner.
4 and 4 are measurement characteristic diagrams of the flame detection signal measured using the device of the present invention, FIG. 5 is a measurement characteristic diagram of the flame detection signal measured using the conventional device, and FIG. 6 is the measurement characteristic diagram of the flame detection signal measured using the conventional device. A circuit diagram of the flame detection circuit of the device, FIG. 7 is a sectional view of a conventional safety device for a combustion appliance. 2...Fuel supply means, 3...Fuel pump, 4
...Burner, 5...Flame detection sensor, 6...
...Flame detection circuit, 7...Amplification section, 8...
Part of the filter. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Time D Figure 3 Time And Figure 4 Figure 5 Time 0 Figure 6 Figure 7

Claims (2)

[Claims] (1) It has a burner that burns fuel, a fuel supply means that intermittently supplies fuel, a flame detection sensor that detects flame, and a flame detection circuit that detects the flame state based on the signal of the flame detection sensor. A safety device for a combustion appliance, wherein the flame detection circuit includes a control circuit that supplies fuel from the fuel supply means only when a signal from the flame detection sensor has an AC signal component corresponding to an amount of fuel supplied. (2) The safety device for a combustion appliance according to claim 1, wherein the flame detection sensor is an optical sensor that reacts to flame light.