JPS6210593Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an abnormal combustion detection device that detects an abnormal combustion state in which a burner intermittently burns due to lack of oxygen for combustion.

FIG. 1 shows a conventional flame detection circuit used to detect a burner flame. In FIG. 1, 1 is a resistor R1 and a flame detector.
A flame detection section consisting of a series circuit of Cds elements (Cds), 2 a smoothing circuit consisting of a resistor R2 and a capacitor C1 for smoothing the output signal from the flame detection section 1, 3 a smoothing circuit consisting of resistors R3, R4 and a comparator U1
This is a level detection circuit consisting of.

When a Cds element (Cds) receives light from a flame,
As its characteristic is that the resistance value decreases rapidly,
A is the connection point between resistor R1 and Cds element (Cds)
The potential at the point drops rapidly. The detection signal obtained as this voltage drop passes through a filter circuit 2 for absorbing level fluctuations caused by flame fluctuations, and is input to one input terminal of the comparator U1. A reference voltage set by resistors R3 and R4 is applied to the other input terminal of the comparator U1, so that the output of the comparator U1 is low if there is no detection signal from the flame detection section 1. level, but it is inverted to H level when a detection signal is received, and flame detection is performed based on this level change. Flame detection is performed in almost the same way when a PDS element or a flame rod type flame detector is used instead of a CDS element (Cds).

Conventional flame detectors with such a configuration can detect the presence or absence of flame relatively reliably, but abnormal combustion conditions may occur in which the flame intermittently grows larger when there is a lack of oxygen for combustion. However, if the flame is large, the output of the smoothing circuit 2 will exceed the set value, so the output of the comparator U1 will be at the same H level as normal flame detection, making it impossible to detect an abnormal state.

The object of this invention is to provide an abnormal combustion detection device that can reliably detect abnormal intermittent combustion conditions.

Next, an embodiment of this invention will be described with reference to the drawings. In FIG. 2, 11 is a flame detection unit that generates a flame detection signal only when a flame is present, 12 is a filter circuit that passes only components within a predetermined frequency band of the flame detection signal, and 13 is a filter circuit of the filter circuit 12. Integrating circuit that smoothes the output, 1
Reference numeral 4 denotes a level detection circuit that outputs a detection output when the output of the integration circuit 13 is equal to or higher than a predetermined reference level.

FIG. 3 shows a specific circuit configuration. The flame detection circuit 11 is similar to the conventional one shown in FIG.
Although it consists of a series circuit of a resistor R11 and a Cds element (Cds), a Pds element or a flame rod type can also be used. A filter circuit 12 that receives the flame detection signal from the flame detection section 1
are resistors R12 to R17, capacitors C11 and C
12 and an operational amplifier U11. Capacitor C1
The impedance of the circuit consisting of 1 and resistor R12 is Z1, capacitor C12 and resistor R16,
If the impedance of the circuit consisting of R17 is Z2, the amplification degree of the operational amplifier U11 is determined by Z2/Z1, and the value of Z1 becomes larger as the frequency becomes lower.
The value of Z2 becomes larger as the frequency becomes higher. Therefore, the filter circuit 12 acts as a bandpass filter that passes only signals within a predetermined frequency bandwidth. The passing frequency bandwidth of this filter circuit 12 is determined by the frequency range of the detection signal of the flame detector 11 (generally confirmed to be around 1 Hz), which corresponds to the period of intermittent combustion that occurs due to a lack of combustion air, etc. ) in advance. The output of this filter circuit 12 is then supplied to the next integrating circuit 13.

Integrating circuit 13 includes resistors R18, R19 and capacitor C13, integrates the output of filter circuit 12, and provides the integrated value to level detecting circuit 14. This level detection circuit 14 has a comparator U12 that compares the terminal voltage of the capacitor C13 with a predetermined reference voltage divided by resistors R20 and R21.
When the output of No. 2 reaches the H level, it is recognized as abnormal combustion, and measures such as cutting off the fuel supply are taken.

In the abnormal combustion device configured in this way,
When there is no flame, the flame detector 11 does not output a detection signal, so no detection output is output from the comparator U12. Further, in the case of normal continuous combustion, the detection signal from the flame detection section 11 is almost a direct current, and the frequency of pulsation due to small flame fluctuations is high, so no output appears on the output side of the filter circuit 12. Therefore, the output of comparator U12 also does not change. However, when abnormal combustion as described above occurs, the frequency component of approximately 1 Hz in the detection signal from the flame detection section 11 increases rapidly, and this frequency component passes through the filter circuit 12 and is integrated by the integration circuit 13. Afterwards, comparator U12 is inverted.

As described above, according to this invention, it is possible to accurately detect when abnormal intermittent combustion occurs due to lack of combustion oxygen, etc. In comparison, safety is significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional flame detection device, FIG. 2 is a block diagram showing the configuration of an abnormal combustion detection device according to an embodiment of the present invention, and FIG. 3 is a specific circuit diagram thereof. 11...flame detection section, 12...filter circuit,
13...Integrator circuit, 14...Level detection circuit,
Cds...Cds element, U11...Operational amplifier, U1
2...Comparator.

Claims (1)

[Scope of utility model registration request] a flame detection circuit that generates a detection signal only while a flame is present; and a filter circuit that passes only the detection signal having a frequency in a predetermined frequency bandwidth corresponding to the flashing cycle of the flame during abnormal intermittent combustion. and a level detection circuit that compares the output of the filter circuit with a predetermined reference level and outputs a detection output when the output is equal to or higher than the reference level.