JP3005356B2 - Flame detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flame detecting apparatus for detecting a flame using an electromotive force of a thermocouple.

[0002]

2. Description of the Related Art Conventionally, a safety mechanism has been incorporated in a combustion apparatus for detecting a state of a flame to prevent the extinguishing of the combustion apparatus. The state of the flame is detected based on the electromotive force of the thermocouple. That is, the state of the flame (the presence or absence of the flame, etc.) is detected by detecting the output of the thermocouple heated by the flame. By the way, in order to ensure the safety of the combustion equipment, it is necessary that the flame detection circuit for detecting the flame always operates normally. Therefore, recently, in order to cope with the abnormality of the flame detection circuit, a double flame detection circuit is provided in parallel, and it is determined that there is a flame only when both of them determine that there is a flame. Even if one of them fails and has a flame, if the other is determined to have no flame, it is determined that there is no flame and the gas passage of the combustion equipment is closed to ensure safety.

[0003]

However, when such a double flame detection circuit is provided, the component cost increases. Further, when one of the flame detection circuits is out of order, it is determined that there is a flame even though there is no flame, and it cannot be said that proper safety control is being performed. SUMMARY OF THE INVENTION It is an object of the present invention to improve the safety of combustion equipment with a simple configuration by solving the above problems and performing a self-check for a failure.

[0004]

The flame detecting device of the present invention comprises:
A thermocouple that is heated by a flame to generate an electromotive force, and a flame detection unit that receives an output of the thermocouple and determines a state of the flame,
A signal switching unit for temporarily cutting off the output of the thermocouple to the flame detection unit or lowering the output to a predetermined level, thereby giving a pseudo flameless state signal to the flame detection unit; A switching control unit for operating the unit, and an abnormality detection unit that determines that the flame detection unit is abnormal when the flame detection unit determines that there is a flame when the no-flame state signal is given. That is the gist.

[0005]

According to the flame detecting device of the present invention having the above-described structure, the flame detecting section determines the state of the flame based on the electromotive force generated by the thermocouple, but performs the following operation to determine the abnormality of the flame detecting section. I do. That is, by temporarily cutting off the output of the thermocouple to the flame detection unit by the signal switching unit or lowering the output to a predetermined level, a pseudo flameless state signal is transmitted to the flame detection unit at an arbitrary interval by the switching control unit. give. At this time, if the flame detector is normal, it is determined that there is no flame, but if it is determined that there is flame, the abnormality detector determines that the flame detector is abnormal. In this way, the abnormality detection of the flame detection unit itself is performed during the flame detection, so that the safety is high, and it is not necessary to provide the flame detection unit twice.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to further clarify the configuration and operation of the present invention described above, a preferred embodiment of the flame detecting device of the present invention will be described below. FIG. 1 is a schematic configuration diagram of a flame detection device provided in a gas combustion device (a gas stove, a water heater, or the like) as an embodiment.

The flame detecting device 1 includes a thermocouple 2 which is heated by the burner B to generate an electromotive force, and a flame detecting circuit 3 which determines whether or not the burner B has a flame according to the output voltage of the thermocouple 2. In the embodiment, a comparator that compares the output voltage of the thermocouple 2 with the set voltage is used), and the solenoid valve V provided in the gas flow path P is controlled according to the output signal of the flame detection circuit 3 and the present invention is also used. A microcomputer 4 (hereinafter, simply referred to as a microcomputer) that performs an abnormality check of the flame detection circuit 3 which is a feature of the apparatus is provided. Further, a changeover switch 5 is provided between the thermocouple 2 and the flame detection circuit 3. The changeover switch 5 temporarily cuts off the output of the thermocouple 2 to the flame detection circuit 5 using the signal output from the microcomputer 4 as a gate signal.

The microcomputer 4 comprises a CPU, a RAM, a ROM, an input / output interface, a bus connecting these components, and the like, which constitute a well-known arithmetic and logic operation circuit (not shown). The function shown in FIG. Becomes That is, a main control unit 4A for controlling gas combustion, a switching signal output circuit 4B for outputting a switching signal to the switching switch 5 at a predetermined timing, a flame detection circuit 3 and a flame based on signals from the switching signal output circuit 4B. An abnormality check circuit 4C for checking an abnormality of the detection circuit 3; Further, an abnormality notification lamp 6 (may be a buzzer) for notifying the user of an abnormality of the flame detection circuit 3 is connected to the main controller 4A via an interface (not shown).

Next, the flame detection circuit 3 executed by the microcomputer 4
Will be described with reference to the flowchart of FIG. When the control routine starts, it is first determined whether or not it is a check timing (S10), and "NO"
In the case of (1), the process shifts to a main process control routine described later (S11). That is, this control routine is interrupted at a predetermined timing with respect to the main routine, and in this embodiment, the cycle of the interrupt processing is set to 5 seconds.

When a predetermined interrupt timing is reached and "YES" is determined in step 10, a changeover signal is output to the changeover switch 5. That is, the change-over switch 5 is tilted to the ground side for a predetermined period (for example, 0.1 second), and a no-flame state signal is input to the flame detection circuit 3 (S12).
Then, it is determined whether or not the output of the flame detection circuit 3 at this time is "no flame" (S13). Actually, it is determined whether the output of the flame detection circuit 3 is H (high level) or L (low level). If the flame detection circuit 3 is normal, the output of the thermocouple 2 is cut off in step 12 and "no flame"
However, if it is determined that "flame exists", an abnormality process is performed as an abnormality of the flame detection circuit 3 (S
14). In this abnormality processing, the electromagnetic valve V provided in the gas flow path P is closed, and the abnormality notification lamp 6 blinks to notify the user of the abnormality. On the other hand, if it is determined in step 13 that there is no flame, the process returns to step 10 again because it is normal.

In the main process of step 11, as shown in FIG. 4, after performing the ignition sequence (S20), the process proceeds to the combustion sequence (S21) to execute normal combustion control. Then, it is determined whether or not a flame is detected by the flame detection circuit 3 during combustion (S22).
Is "no flame", the solenoid valve V is closed in order to prevent the outflow of raw gas as a misfire,
A misfire is notified (S23). The misfire notification is performed by, for example, sounding a buzzer (not shown) or blinking a misfire notification lamp (the abnormality notification lamp 6 may also be used). If a fire extinguishing operation is performed during combustion, the process proceeds to a fire extinguishing sequence (not shown) to stop the combustion.

As described above, according to the flame detection device 1 of the present embodiment, the output from the thermocouple 2 is temporarily cut off, and the output of the flame detection circuit 3 at that time is checked, so that the flame detection device 3 can detect during the combustion. The abnormality detection of the flame detection circuit 3 itself can be performed, and the safety of the combustion equipment can be greatly improved. Moreover,
It is not necessary to provide the flame detection circuit 3 doubly as in the related art, and the cost can be reduced. Further, since the abnormality notification lamp 6 can recognize the abnormality of the flame detection circuit 3,
Repairers do not need to search for a failed part, and maintenance becomes easier.

The embodiments of the present invention have been described above.
The present invention is not limited to these embodiments at all, and it goes without saying that the present invention can be implemented in various modes without departing from the gist of the present invention. For example, in this embodiment, the output of the thermocouple 2 is cut off by the changeover switch 5. However, as shown in FIG. 2, a changeover switch 5A that grounds the output side of the thermocouple 2 may be used. Alternatively, the output may be lower than the comparison set voltage of the flame detection circuit 3.

[0014]

As described above in detail, according to the flame detection device of the present invention, it is possible to check the failure of the flame detection unit itself during combustion, and to enhance the safety of the combustion equipment. In addition, it is not necessary to provide a double flame detection circuit as in the related art, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a flame detection device as one embodiment.

FIG. 2 is a schematic configuration diagram illustrating a modification of a changeover switch.

FIG. 3 is a flowchart illustrating an abnormality check control routine.

FIG. 4 is a flowchart illustrating a main processing control routine.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Flame detection device, 2 ... Thermocouple, 3 ... Flame detection circuit, 4 ... Microcomputer, 4A ... Main control part, 4B ... Switching signal output circuit, 4C ... Abnormality check circuit, 5 ... Switching switch.

Claims (1)

(57) [Claims] 1. A thermocouple that is heated by a flame to generate an electromotive force, a flame detection unit that receives an output of the thermocouple and determines a state of a flame, and an output of the thermocouple to the flame detection unit. A signal switching unit for temporarily disconnecting or lowering the flame to a predetermined level to simulate a flameless state signal to the flame detection unit; a switching control unit for operating the signal switching unit at an arbitrary interval; A flame detection device comprising: an abnormality detection unit that determines that the flame detection unit is abnormal when the flame detection unit determines that there is a flame when the absence state signal is given.