JPH11241821A - Combustion condition detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate malfunction in the case of checking a trouble by providing an enough allowance against noise. SOLUTION: A changeover switch 5 switches a setting circuit 7a of a first reference voltage, employable as a deciding reference in a flame detecting circuit 3, into a setting circuit 7b of a second reference voltage, having a level non-available normally, temporarily during combustion. In this case, when the flame detecting circuit 3 has decided that 'flame exists', an abnormality checking circuit 4C judges that the flame detecting circuit 3 is faulty whereby a main control unit 4A flashes an abnormality informing lamp 6 and closes a solenoid valve V.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a combustion state detecting device for detecting a combustion state.

[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 outflow of raw gas due to extinction. Since the state of the flame is detected based on the thermoelectromotive force of the thermocouple, the flame detection circuit for detecting the flame must always operate normally in order to ensure the safety of the combustion equipment. Therefore, recently, in order to cope with the abnormality of the flame detection circuit, the flame detection circuit is provided in duplicate in parallel, and it is determined that "flame exists" only when both of them determine "flame exists". Therefore, even if one of them fails and becomes "flame present", if the other is determined to be "no flame", the gas passage of the combustion equipment is closed by "no flame" to ensure safety. .

However, when such a double flame detection circuit is provided, there is a problem that the component cost is increased. Also, if one of the flame detection circuits fails while judging that there is “flame present”, it cannot be used as it is and cannot cope with the failure of the other flame detection circuit, and it cannot be said that proper safety control is being achieved. Was.

To cope with such a problem, Japanese Patent Laid-Open No.
In −215327, the input of the thermocouple output to the flame detection circuit is temporarily cut off during combustion, and when the flame detection circuit determines “flame present” at this time, it is determined that the flame detection circuit is faulty. A flame detector that blinks an abnormality notification lamp and closes a solenoid valve is shown. For example, when the reference voltage of the flame detection circuit is set to 5 mv and the output voltage of the thermocouple is 7 mv in a normal combustion state, the input to the flame detection circuit is temporarily switched to 0 mv, and the flame detection circuit If "no flame" is determined, the flame detection circuit is determined to be normal, and if "flame is determined", the flame detection circuit is determined to be abnormal.
Therefore, with this flame detection device, it is possible to check the failure of the flame detection unit itself during combustion, thereby improving the safety of the combustion device, and eliminating the need to provide a double flame detection circuit, thereby reducing costs. Can be achieved.

[0005]

However, in such a combustion state detecting device, there is a problem that the voltage difference to be temporarily switched is too small and there is no margin for noise. For example, when the normal output voltage value is 7 mv and the input to the flame detection circuit is temporarily switched to 0 mv, 7 mv
Can not be taken. Originally, the output voltage of the thermocouple is small, so that even if the output voltage of the thermocouple is cut off, the voltage difference at the time of switching cannot be made large, and it is difficult to reliably lower the voltage below the reference voltage due to the influence of noise. (When a switch is provided to ground the output side of the thermocouple to lower the voltage to a predetermined level, it is difficult to reliably lower the voltage below the reference voltage due to the contact resistance of the switch.) When performing a failure check, there is a risk of malfunction. Therefore, it is an object of the present invention to provide a combustion state detecting device that solves the above-mentioned problems and provides a margin for noise so that malfunction does not occur at the time of a failure check.

[0006]

According to a first aspect of the present invention, there is provided a combustion state detecting apparatus for changing one of an electric resistance value, an output voltage value and an output current value in accordance with a combustion state. A combustion state detector that compares a value detected by the sensor with a reference value, and determines whether normal combustion or abnormal combustion based on the magnitude of the comparison.
A reference value switching unit that temporarily switches to a second reference value that is a level determined to be abnormal combustion if the combustion state detection unit is normal; a switching control unit that operates the reference value switching unit at arbitrary intervals; An abnormality detection unit that determines that the combustion state detection unit is abnormal when the combustion state detection unit determines that normal combustion is performed despite switching to the second reference value. I do.

According to a second aspect of the present invention, there is provided a combustion state detecting apparatus, comprising: a thermocouple which is heated by a flame to generate a thermoelectromotive force; A flame detection unit that determines that there is a flame when the value is larger than the reference voltage value and determines that there is no flame when the value is smaller, and sets the reference voltage value to a second reference voltage value that is a large level that the thermocouple cannot output. A reference voltage switching unit that temporarily switches, a switching control unit that operates the reference voltage switching unit at an arbitrary interval, and the flame detection unit determines that there is a flame despite switching to the second reference voltage value. In this case, the gist of the invention is to include an abnormality detection unit that determines that the flame detection unit is abnormal.

In the combustion state detecting device according to the first aspect of the present invention having the above-described structure, the combustion state detecting section determines whether a normal state or an abnormal state based on a judgment whether the value detected by the sensor is larger or smaller than a reference value. Is determined, the following operation is performed to determine the abnormality of the combustion state detection unit. That is, the reference value serving as the determination reference is temporarily switched to the second reference value at which the combustion state detection unit pseudo-determines abnormal combustion. At this time, if the combustion state detection unit determines that the combustion is normal, despite switching to the second reference value for determining the abnormal combustion, the abnormality detection unit determines that the combustion state detection unit is abnormal. . Since the second reference value can be set arbitrarily, the difference between the first reference value and the second reference value can be set large. Therefore, a margin can be given to noise, and malfunction can be prevented at the time of a failure check of the combustion state detection unit.

Further, the present invention having the above-mentioned structure has a second aspect.
In the described combustion state detection device, the flame detection unit determines the state of the flame based on the thermoelectromotive force generated by the thermocouple, but performs the following operation to determine the abnormality of the flame detection unit. That is, the reference voltage value serving as a criterion is temporarily switched to a large-level second reference value that cannot be output by the thermocouple so that the flame detection unit simulates abnormal combustion. At this time, if the flame detector is normal, it is determined that there is no flame. However, if it is determined that there is flame, the abnormality detector determines that the flame detector is abnormal. Since the second reference value can be set arbitrarily, the difference between the first reference value and the second reference value can be set large.

[0010]

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 a burner B to generate a thermoelectromotive force, an amplifier circuit 9 for amplifying an output voltage of the thermocouple 2, and comparing the amplified output voltage with a reference voltage. And a flame detection circuit 3 (in this embodiment, a comparator for comparing the amplified output voltage with a reference voltage) is used to determine whether or not there is a flame in the burner B. A microcomputer 4 (hereinafter, simply referred to as a microcomputer) that controls an electromagnetic valve V provided in the flow path and checks an abnormality of the flame detection circuit 3 is provided. Further, a changeover switch 5 for switching the reference voltage of the flame detection circuit 3 from the first reference voltage to the second reference voltage is provided. The changeover switch 5 temporarily switches the detection reference level of the flame detection circuit 3 using a 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). 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 to be 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 interruption timing is reached and "YES" is determined in step 10, a switching signal is output to the changeover switch 5. That is, the changeover switch 5 temporarily switches the connection from the first reference voltage setting circuit 7a serving as a criterion for determining the presence or absence of a flame to the second reference voltage setting circuit 7b having a large level that cannot be normally output by the thermocouple 2 (S1).
2) (for example, switch for only 0.1 second). And
It is determined whether or not the output of the flame detection circuit 3 at this time is "no flame", and it is determined whether or not the flame detection circuit 3 has a determination capability based on the reference voltage value. (S13). Actually, the flame detection circuit 3
Is determined based on whether the output is H (high level) or L (low level). If the flame detection circuit 3 is normal, step 1
According to 2, since the reference voltage is switched to a level that cannot be normally set, it should be determined that there is no flame.
When it is determined that "flame exists", an abnormality process is performed as an abnormality of the flame detection circuit 3 (S14). In this abnormal processing,
The electromagnetic valve V provided in the gas flow path 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,
Since it is normal, the processing shifts to the processing from step 10 again.

In the reference voltage switched in step 12, for example, the first reference voltage is set to 0.5 V and the second reference voltage is set to 0.5 V.
The reference voltage is set to 1v. And the output voltage is 7m
v, the amplifying circuit 9 amplifies the thermoelectromotive force to 0.7 V, and the changeover switch 5 sets the reference voltage of the flame detecting circuit 3 to the first voltage.
The reference voltage (0.5 v) is temporarily switched to the second reference voltage (1 v), and the flame detection circuit 3 determines the magnitude of the amplified voltage (0.7 v) based on the second reference voltage (1 v). . In this case, when the flame detection circuit 3 determines that there is no flame, the microcomputer 4 determines that the flame detection circuit 3 is normal, and when it determines that there is a flame, the microcomputer 4 determines that the flame detection circuit 3 is abnormal.

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). If the output of the flame detection circuit 3 is "no flame", it is determined that a misfire has occurred and the outflow of raw gas is prevented. Therefore, the solenoid valve V is closed and 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 reference voltage of the flame detection circuit 3 is temporarily switched to the second reference voltage, and the output of the flame detection circuit 3 at that time is examined. Thus, the abnormality detection of the flame detection circuit 3 itself can be performed during the combustion. Further, since the second reference voltage can be set as large as the power supply allows, the difference between the first reference voltage and the second reference voltage can be set large, and a margin can be provided for noise. Therefore, there is no need to worry about malfunction due to noise during a failure check.

Further, by providing an amplifying circuit for amplifying the output voltage, not only the abnormality check based on the second reference voltage setting circuit 7b, but also the judgment based on the first reference voltage setting circuit 7a as a criterion for judging the presence or absence of a flame. Sometimes, even if it receives noise after amplification, its effect can be ignored. Further, since the output voltage is amplified, it is not necessary to increase the accuracy of the comparator that compares the output voltage with the reference voltage.

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 the present embodiment, the thermocouple 2 that is heated by the burner B to generate a thermoelectromotive force, and the flame detection circuit 3 that determines the presence or absence of the flame of the burner B according to the output voltage of the thermocouple 2 are provided. However, as shown in FIG. 2, the primary thermocouple 2a is heated by the combustion flame of the burner B and outputs a thermoelectromotive force, and is heated by the exhaust heat from the exhaust clogging detection opening provided in the combustion chamber 10 to generate heat. A secondary thermocouple 8 that outputs an electromotive force is provided, and the primary thermocouple 2a and the secondary thermocouple 8 are connected in series with opposite polarities to form an output voltage of a combined electromotive force, thereby generating an oxygen-deficient atmosphere or a combustion chamber. An incomplete combustion prevention circuit for judging the state of exhaust gas clogging downstream of 10 may be used.

Alternatively, a combustion state detecting circuit may be provided which has a sensor for changing the electric resistance value according to the oxygen concentration, the carbon monoxide concentration or the carbon dioxide concentration, and detects the combustion state based on the electric resistance value.

The burner B may be provided with a flame rod for detecting a combustion flame, and a combustion state detection circuit for detecting a combustion state based on the current value.

The thermocouple 2 is not limited to being heated by the combustion flame of the burner B to generate a thermoelectromotive force.
The thermocouple 2 may be heated by a sensing burner flame that detects incomplete combustion before the combustion of the fuel becomes incomplete combustion.

[0023]

As described in detail above, claim 1 of the present invention
According to the described combustion state detection device, it is possible to perform a failure check on whether or not the combustion state detection unit has a determination ability based on a reference value. In addition, there is an excellent effect that no malfunction is caused to noise detected at the time of a failure check.

Further, according to the combustion state detecting device of the second aspect of the present invention, a failure check of the flame detecting section itself can be performed, and the same effect can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a schematic configuration diagram of a combustion state detection device as another embodiment.

FIG. 3 is a flowchart showing 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 (2)

[Claims] 1. A sensor for changing any one of an electric resistance value, an output voltage value, and an output current value according to a combustion state,
A combustion state detection unit that compares a value detected by the sensor with a reference value and determines whether the combustion is normal or abnormal based on the magnitude determination; and A reference value switching unit that temporarily switches to a second reference value that is a level determined to be combustion, a switching control unit that operates the reference value switching unit at an arbitrary interval, and a control unit that switches to the second reference value. Irrespective of the above, when the combustion state detecting section determines that the combustion is normal, an abnormal state detecting section which determines that the combustion state detecting section is abnormal is provided. 2. A thermocouple that is heated by a flame to generate a thermoelectromotive force. The thermocouple generates an electromotive force when the output voltage value of the thermoelectromotive force is greater than a reference voltage value. A flame detection unit that determines that there is no; a reference voltage switching unit that temporarily switches the reference voltage value to a second reference voltage value that is a large level that the thermocouple cannot output; A switching control unit to be operated; 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 despite switching to the second reference voltage value. A combustion state detection device characterized by the above-mentioned.