JP2012180991A - Gas combustion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly carry out diagnosing sequence of a fire extinction countermeasure circuit 32 even though remaining heat when gas burns at previous time remains in a thermocouple 14, in a water heater 10 in which the fire extinction countermeasure circuit 32 detects fire extinction from the thermocouple 14 and stops gas from a burner 12.SOLUTION: A gas valve 13 opens and closes a gas feeding channel 11 according to the energization of a coil 22. The fire extinction countermeasure 32 normally makes an FET 21 a conductive state. The diagnosing sequence is carried out prior to a firing sequence according to the push down of an ignition switch 38. A microcomputer 37 makes FETs 23, 29 an conductive state and a shut down state by a S3, a S4 respectively and caused a flame detecting circuit 28 to output a S5 without flame in the diagnosing sequence. The fire extinction countermeasure circuit 32 determines fire extinction from the S5 and shuts off the FET 21 by a S7 during normal operation, The FET 21 remains in the conductive state during an operation failure condition. The microcomputer 37 stops the execution of the ignition sequence when the S2 is "H".

Description

  The present invention relates to a gas combustion apparatus such as a gas water heater, and more particularly to a gas combustion apparatus that shuts off gas supply to a burner when a misfire is detected.

  In a gas combustion apparatus such as a gas water heater, when a misfire of a burner is detected, a process for closing a gas supply path to the burner is performed by a microcomputer and a misfire countermeasure circuit. Moreover, the closing process of the gas supply path at the time of misfire detection is performed by the microcomputer prior to the misfire countermeasure circuit.

  Therefore, when a malfunction occurs in the misfire handling process of the microcomputer, the misfire handling process is performed by the misfire handling circuit, so that it is immediately understood that the misfire handling process of the microcomputer has a malfunction. However, if the misfire countermeasure processing by the microcomputer is normal, the misfire countermeasure processing is performed by the microcomputer regardless of whether the misfire countermeasure circuit is normal or defective. Therefore, there is a possibility that the burner burns in a state where the malfunction of the misfire countermeasure circuit has occurred.

  Patent Document 1 discloses a gas combustion apparatus that detects a flame in a burner using a flame detection circuit, detects a misfire based on a detection signal from the flame detection circuit, and closes a gas supply path when a misfire is detected. (FIG. 1 of Patent Document 1). The gas combustion apparatus performs a diagnostic sequence for checking whether the misfire countermeasure circuit operates normally every time a combustion operation start command is issued (paragraph 0020 and FIG. 2 of Patent Document 1).

  Patent Document 2 discloses a gas combustion apparatus including a flame detection circuit that detects the presence or absence of a flame from the output of a thermocouple heated by a flame of a burner (FIG. 1 of Patent Document 2). In the gas combustion apparatus, if a switch is interposed between the thermocouple and the flame detection circuit, and the flame detection circuit outputs a flame presence when the switch is in the cut-off state, the flame detection circuit malfunctions. (FIG. 3 of Patent Document 2).

  Patent Document 3 discloses a gas combustion apparatus including a flame detection circuit that detects the presence or absence of a flame from the output of a thermocouple heated by a flame of a burner (FIG. 2 of Patent Document 3). In the gas combustion apparatus, the connection circuit between the thermocouple and the flame detection circuit can be appropriately connected to the ground by a switch, and when the switch is in a conductive state, the temperature corresponding to the 0 mV output of the thermocouple from the flame detection circuit. When a temperature different from is output, it is determined that a malfunction of the flame detection circuit has occurred, and the gas supply path is forcibly closed (paragraph 0010 of Patent Document 3).

  Patent Document 4 discloses a gas combustion device including a flame detection circuit that detects the presence or absence of a flame from the output of a thermocouple heated by a flame of a burner (FIG. 2 of Patent Document 4). The gas combustion apparatus is provided with a switch for switching the input side of the flame detection circuit to a thermocouple or a predetermined voltage generator, and when the input side of the flame detection circuit is connected to the predetermined voltage generator, the thermocouple has a predetermined voltage. If the flame detection circuit outputs a different output from the normal output of the flame detection circuit when the same voltage as that of the generator is output to the flame detection circuit, the flame detection circuit will malfunction. Therefore, the gas supply path is forcibly closed (paragraph 0009 of Patent Document 4).

JP 2004-93047 A JP-A-5-215327 Japanese Patent Laid-Open No. 9-60865 Japanese Patent Laid-Open No. 9-60866

  In the gas combustion apparatus of Patent Document 1, a thermocouple is used for flame detection, and when there is a combustion instruction in a short period after the burner gas combustion ends, residual heat remains in the thermocouple. However, since it is determined that the state is a combustion state in spite of being in the fire extinguishing state, it is difficult to diagnose whether or not the misfire countermeasure circuit properly closes the gas supply path when the misfire is detected.

  The gas combustion devices of Patent Documents 2 to 4 only diagnose whether the flame detection circuit is normal, and cannot diagnose until the misfire processing circuit provided separately from the microcomputer operates normally. .

  An object of the present invention is to provide a gas combustion apparatus capable of correctly diagnosing a misfire countermeasure circuit before ignition even in a situation where the output of the thermocouple does not indicate the actual presence or absence of flame due to residual heat of the thermocouple, etc. It is to be.

  A gas combustion apparatus according to a first aspect of the invention includes an on-off valve that opens and closes a gas supply path to a burner by a driving current, a thermocouple that is heated by a flame in the burner and generates a thermoelectromotive force from a heating temperature, and a thermoelectromotive force A flame detection circuit for sending a signal with a flame when it is above a predetermined level; first switch means interposed at one end of the on-off valve in the drive current circuit of the on-off valve; and the on-off valve in the drive current circuit The second switch means interposed on the other end side of the first switch and when the on-off valve is energized and it is determined that there is no flame by a signal from the flame detection circuit, it is determined that the burner has misfired and the first switch A misfire handling circuit for switching the means from a conducting state to a shut-off state, and an input to the misfire handling circuit is switched between a first signal based on the output of an actual thermocouple and a second signal at a fixed level indicating no flame. Third switch means and diagnostic means for executing a diagnostic sequence of the misfire countermeasure circuit prior to execution of the ignition sequence, wherein the misfire countermeasure circuit brings the first switch means into a conductive state except when a misfire is detected. In the first stage of the diagnostic sequence, the diagnostic means turns off the second switch means and checks the test voltage between the first switch means and the second switch means. If the inspection voltage indicates the cut-off state of the first switch means, the ignition sequence is suspended, and if the inspection voltage indicates the conduction state of the first switch means, the diagnosis is performed. The process proceeds to the second stage of the sequence, and in the second stage of the diagnostic sequence, the input to the misfire countermeasure circuit is the second signal by the third switch means. The inspection voltage in a state in which the second switch means is turned on is checked, and if the inspection voltage indicates the conduction state of the first switch means, the execution of the ignition sequence is suspended. To do.

  According to the first invention, in the first stage of the diagnostic sequence, it is checked whether the test voltage indicates the cutoff state of the first switch means. It is possible to appropriately diagnose whether or not the means is correctly conducting.

  Further, when the second switch means is turned on and the on-off valve is energized, the third switch means switches the input signal of the misfire countermeasure circuit to a second signal of a fixed level indicating no flame, and misfires. The coping circuit checks whether or not the first switch means is cut off against misfire. Therefore, even if the flame detector outputs an output different from the presence or absence of the actual flame due to reasons such as not having passed since the end of the previous combustion in the burner, It can be properly diagnosed whether it operates correctly.

  The gas combustion device according to a second aspect of the present invention is the gas combustion device according to the first aspect, wherein the misfire countermeasure circuit is configured such that a voltage between the on-off valve and the second switch means is cut off from a conduction state of the second switch means. If the change signal indicates a change to, it is determined that the on-off valve is de-energized, and the first switch means is switched from the shut-off state to the conductive state, and the diagnosis means is a second part of the diagnosis sequence. If the test voltage indicates that the first switch means is shut off, the process proceeds to the third stage of the diagnostic sequence. In the third stage of the diagnostic sequence, the second switch means is turned on. The inspection voltage is examined after switching from the state to the cutoff state, and if the inspection voltage indicates the cutoff state of the first switch means, the execution of the ignition sequence is suspended. To.

  If the misfire countermeasure circuit does not turn on the first switch means at the start of the ignition sequence, gas ignition will not be performed properly in the ignition sequence. According to the second aspect of the present invention, in the third stage of the diagnostic sequence, the diagnostic switch is configured so that the misfire countermeasure circuit is in the ignition sequence by switching the second switch unit from the conductive state to the cut-off state and then examining the inspection voltage. It can be diagnosed at the start whether the first switch means is in the proper conducting state.

  According to a third aspect of the present invention, there is provided the gas combustion apparatus according to the first or second aspect, wherein the misfire countermeasure circuit is configured such that the voltage between the on-off valve and the second switch means is in a conductive state. When the timer has started, the timer is started, and when the set time of the timer has elapsed, it is determined whether or not the burner has misfired based on the flame detection input, and when the misfire is detected, the first switch means is cut off from the conductive state. The diagnostic means is characterized in that the set time of the timer in the diagnostic sequence is shorter than the set time of the timer in the ignition sequence.

  In the ignition sequence, in the ignition sequence, the gas valve coil is energized at the start thereof, and a timer is used to make a misfire determination after a predetermined time has elapsed since the gas valve coil was energized. However, if the misfire handling circuit makes a misfire determination after the set time of the timer elapses, the processing time of the diagnostic sequence becomes longer. According to the third invention, the diagnostic means makes the set time of the timer in the diagnostic sequence shorter than the set time of the timer in the ignition sequence, so that the misfire handling circuit makes a misfire determination from the start of the second stage of the diagnostic sequence. The time required for the second stage can be shortened by shortening the time until the second stage.

The block diagram of the principal part of a water heater. The flowchart of a diagnostic sequence.

  The present invention is a flame detection device used in a water heater 10 that operates on battery voltage.

  In FIG. 1, S1 to S7 indicate signals related to the diagnostic sequence and the ignition sequence.

  The gas supply path 11 guides the gas to the burner 12, and the gas valve 13 opens and closes the gas supply path 11 by energizing and shutting off (non-energizing) the gas valve coil 22 via the gas supply path 11. The gas is ejected from the burner 12, and the ejected gas is ignited by an ignition electrode (not shown) to generate a flame 15. The thermocouple 14 is disposed near the burner 12 and outputs a voltage corresponding to the ambient temperature. When the flame 15 is generated, the thermocouple 14 is heated by the flame 15. The thermocouple 14 increases the output level as it is heated to a higher temperature.

  The FET 21, the gas valve coil 22 of the gas valve 13, and the FET 23 are connected in series from the DC voltage terminal 20 in that order, interposed between the DC voltage terminal 20 and the ground, and a drive current circuit for the gas valve coil 22. Configure. The FET 21 is normally in a conductive state (ON), and is switched off (OFF) by a switch OFF command S7 from the misfire countermeasure circuit 32. The response signal S2 indicates the voltage level between the FET 21 and the FET 23, thereby inputting the switching state of the FET 21 to the microcomputer 37.

  The FET 23 is switched between a conductive state and a cut-off state by a switch command S3 from the microcomputer 37. The response signal S6 indicates the voltage level between the gas valve coil 22 and the FET 23, and inputs the energization state of the gas valve coil 22 to the misfire countermeasure circuit 32 according to the switching state of the FET 23.

  The thermocouple 14 is connected to the flame detection circuit 28 via the FET 29 on one end side, and is connected to the ground on the other end side. The FET 29 is switched between a conduction state and a cutoff state by a switch command S4 from the microcomputer 37.

  When the FET 29 is in a conducting state, the flame detection circuit 28 receives the thermoelectromotive force of the thermocouple 14 at the input terminal, and determines whether the input level of the input terminal is greater or smaller than the threshold value. “(High level)” or “L” (low level) is output to the misfire countermeasure circuit 32 and the microcomputer 37 as the detection signal S5. The input terminal of the flame detection circuit 28 is pulled down to the ground level below the threshold when the FET 29 is in the cut-off state and the output of the thermocouple 14 is not input. L "is output.

  The misfire countermeasure circuit 32 outputs a switch OFF command S7 to the FET 21 based on the signals S5 and S6 and a built-in timer (not shown). The timer acceleration circuit 33 switches the set time of the built-in timer of the misfire countermeasure circuit 32 based on the self-check command S1 from the microcomputer 37. Specifically, when S1 is off, the set time of the built-in timer is set to a normal predetermined time T1 (T1> 0), and when S1 is on, the set time of the built-in timer is maintained at 0.

  The built-in timer of the misfire countermeasure circuit 32 is constituted by, for example, a CR circuit, and the time constant of the CR circuit is associated with the set time of the built-in timer. When setting the set time to 0, for example, both ends of R (resistance) of the CR circuit are short-circuited in order to set the time constant to approximately 0.

  When the user of the water heater 10 instructs the start of gas combustion in the burner 12, the user presses the operation switch 38, burns the gas in the burner 12, presses the operation switch again during combustion, and instructs the combustion stop. To do.

  Next, the process accompanying the start of the combustion operation of the water heater 10 will be described with reference to the flowchart of FIG. The water heater 10 corresponds to the gas combustion apparatus of the present invention. The gas valve 13 corresponds to the on-off valve in the present invention. The gas valve 13 is opened by energizing the gas valve coil 22. The FETs 21, 23, and 29 correspond to the first, second, and third switch means in the present invention, respectively. The microcomputer 37 includes diagnostic means in the present invention. The flame detection input of the misfire countermeasure circuit 32 in the present invention corresponds to the output of the flame detection circuit 28, and the output of the flame detection circuit 28 is based on the output of the thermocouple 14 as a flame detector when the FET 29 is in a conductive state. In addition, when the FET 29 is in the cut-off state, the level is a fixed level corresponding to the input of the flame detection circuit 28 pulled down to the ground level.

  The microcomputer 37 executes processing according to the flowchart of FIG. 2 according to a program in a ROM (not shown). In the flowchart, the processing of STEPs 40 and 41 corresponds to the first stage of the diagnostic sequence in the present invention, the processing of STEPs 42 and 43 corresponds to the second stage of the diagnostic sequence in the present invention, and the processing of STEPs 44 and 45 is the present invention. This corresponds to the third stage of the diagnostic sequence.

  The user of the water heater 10 depresses the operation switch 38 when starting combustion of gas in the burner 12. In STEP 40, as soon as an instruction to start the combustion operation is given, the process proceeds to STEP 41. In STEP 41, it is determined whether the response signal S2 is “H” or “L”. If it is “H”, the FET 21 is in a conductive state, the misfire countermeasure circuit 32 is normal, and the process goes to STEP 42. If "L", the process proceeds to R52 and executes R52.

  R52 is a routine for ending the combustion operation, and is also performed when the water heater 10 is operating normally and the user ends the combustion of the burner 12. As a result of the execution of R52 at the time of the combustion operation start instruction in the burner 12, the microcomputer 37 naturally stops executing the ignition sequence of R51.

  In the termination routine of R52, the microcomputer 37 stops power supply to the electrical elements including the misfire countermeasure circuit 32 and the DC voltage terminal 20.

  In STEP42, the microcomputer 37 turns on the self-check command S1, turns on the switch command S3, and turns off S4.

  Note that when the self-check command S1 is turned on, the timer acceleration circuit 33 sets the timer setting time of the misfire countermeasure circuit 32 to 0, and when the self-check command S1 is turned off, the timer acceleration circuit 33 causes the misfire countermeasure circuit 32 to The set time of the timer is set to T1 (T1> 0) when the ignition sequence is executed. On the other hand, when the switch command is turned on, the output destination FET is turned on, and when the switch command is turned off, the output destination FET is turned off.

  When the self-check command S1 in STEP42 is turned on, the switch command S3 is turned on, and the switch command S4 is turned off, the timer setting time of the misfire countermeasure circuit 32 in the timer acceleration circuit 33 becomes 0, and the FET 23 is switched to the conductive state. , FET 29 is switched to the cut-off state.

  The misfire countermeasure circuit 32 determines when the response signal S6 is switched from "H" to "L" as the operation start time of the built-in timer, and waits for the set time of the built-in timer to elapse from the time of switching. When the set time has elapsed, a switch OFF command S7 is output based on whether S5 is "H" or "L".

  Since the response signal S6 is switched from “H” to “L” and the setting time of the built-in timer of the misfire countermeasure circuit 32 is set to 0, almost immediately after the execution of STEP42, the misfire countermeasure circuit 32 has S5 set to “H”. Or “L”. In STEP42, since the FET 29 is switched to the cut-off state, the flame detection circuit 28 outputs "L" indicating no flame regardless of the output of the thermocouple 14.

  Thus, if it is normal, the misfire handling circuit 32 determines that a misfire has occurred immediately after the execution of STEP 42, outputs the switch OFF command S7, and turns off the FET 21. Further, if the misfire handling circuit 32 is in a malfunctioning state, the FET 21 maintains a conductive state even after STEP 42 is executed.

  In STEP43, it is determined whether the response signal S2 is "H" or "L". If it is "L", it is determined that the misfire countermeasure circuit 32 has operated normally, and the process proceeds to STEP44. If there is, proceed to R52 and execute R52.

  In STEP 44, the microcomputer 37 switches the self-check command S1 off, switches the switch command S3 off, and switches S4 on. Turning off the self-check command S1 causes the timer acceleration circuit 33 to perform processing for returning the set time of the timer of the misfire countermeasure circuit 32 from 0 to the original set time T1.

  Thus, the output of the thermocouple 14 is input to the flame detection circuit 28 via the FET 29, and the flame detection circuit 28 generates an output according to the temperature detected by the thermocouple 14.

  When the misfire countermeasure circuit 32 detects that the response signal S6 has changed from "L" to "H", the microcomputer 37 normally shuts off the FET 23, stops the switch OFF command S7, and turns off the FET 21. Switch from the shut-off state to the conducting state to prepare for the start of the ignition sequence. If the misfire countermeasure circuit 32 is in a malfunctioning state, even if S6 changes to “L” and “H”, the switch OFF command S7 remains maintained, and the FET 21 remains conductive.

  In STEP 45, it is determined whether the response signal S2 is “H” or “L”. If it is “H”, the process proceeds to R51, and if it is “L”, the process proceeds to R52 and R52 is executed. .

  In R51, the microcomputer 37 switches the switch command S3 from off to on and starts a known ignition sequence.

  The gas combustion apparatus of the present invention is not limited to the water heater 10, but can also be applied to a hot air heater and other gas combustion apparatuses.

  In the flowchart of FIG. 2, the switch command S4 is turned off in STEP42 simultaneously with the switch command S3 being turned on. However, when the response signal S2 is determined in STEP43, the switch command S3 is turned off and the switch command S4 is turned off. If it is guaranteed that the switch command S4 is off, it may be output before or after the switch command S3.

  In FIG. 1, the FET 29 is interposed between the thermocouple 14 and the input terminal of the flame detection circuit 28, but the FET 29 is between the connection circuit between the thermocouple 14 and the input terminal of the flame detection circuit 28 and the ground. You may come to intervene. Further, the FET 29 may be interposed between the flame detection circuit 28 and the misfire countermeasure circuit 32 instead of between the thermocouple 14 and the input terminal of the flame detection circuit 28.

DESCRIPTION OF SYMBOLS 10 ... Water heater (gas combustion apparatus), 11 ... Gas supply path, 12 ... Burner, 13 ... Gas valve (open / close valve), 14 ... Thermocouple, 15 ... Flame, 21 ... FET (first switch means), 23 ... FET (second switch means), 28 ... Flame detection circuit, 29 ... FET (third switch means), 32 ... Misfire countermeasure circuit 33 ... Timer acceleration circuit, 37 ... Microcomputer (diagnostic means), 38 ... Ignition switch.

Claims (3)

An on-off valve that opens and closes the gas supply path to the burner by the drive current;
A thermocouple that is heated by a flame in the burner and generates a thermoelectromotive force from the heating temperature;
A flame detection circuit that sends out a flame signal when the thermoelectromotive force is above a predetermined level;
First switch means interposed on one end side of the on-off valve in the on-off valve drive current circuit;
Second switch means interposed on the other end side of the on-off valve in the drive current circuit;
A misfire countermeasure circuit for judging that the burner has misfired and switching the first switch means from a conductive state to a shut-off state when the open / close valve is energized and it is determined that there is no flame based on a signal from the flame detection circuit; ,
Third switch means for switching the input to the misfire countermeasure circuit to a first signal based on the output of an actual thermocouple and a second signal of a fixed level indicating no flame;
Diagnostic means for performing a diagnostic sequence of the misfire countermeasure circuit prior to execution of the ignition sequence;
With
The misfire countermeasure circuit holds the first switch means in a conductive state except when a misfire is detected,
The diagnostic means includes
In the first stage of the diagnostic sequence,
The second switch means is turned off, and an inspection voltage between the first switch means and the second switch means is examined,
If the inspection voltage indicates the cut-off state of the first switch means, the execution of the ignition sequence is suspended,
If the test voltage indicates the conduction state of the first switch means, the process proceeds to the second stage of the diagnostic sequence,
In the second stage of the diagnostic sequence,
Examining the test voltage in a state where the input to the misfire countermeasure circuit is the second signal by the third switch means and the second switch means is in a conductive state;
If the inspection voltage indicates the conduction state of the first switch means, the ignition sequence is suspended. The gas combustion apparatus according to claim 1, wherein
In the misfire countermeasure circuit, if the voltage between the on-off valve and the second switch means indicates a change from the conduction state to the cutoff state of the second switch means, the on-off valve is not energized. And switching the first switch means from the cut-off state to the conductive state,
The diagnostic means includes
In the second stage of the diagnostic sequence, if the inspection voltage indicates the cutoff state of the first switch means, the process proceeds to the third stage of the diagnostic sequence,
In the third stage of the diagnostic sequence,
After switching the second switch means from the conductive state to the cut-off state, examine the inspection voltage,
If the inspection voltage indicates a cut-off state of the first switch means, the ignition sequence is suspended. The gas combustion apparatus according to claim 1 or 2,
The misfire countermeasure circuit starts a timer operation when a voltage between the on-off valve and the second switch means becomes conductive, and when a set time of the timer has elapsed. , Based on the flame detection input, the presence or absence of misfire in the burner is determined, and when the misfire is detected, the first switch means is switched from a conduction state to a cutoff state,
The gas combustion apparatus according to claim 1, wherein the diagnostic means makes the set time of the timer in the diagnostic sequence shorter than the set time of the timer in the ignition sequence.

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