JPH10169977A - Incomplete combustion prevention apparatus for gas hot water heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an incomplete combustion prevention apparatus for gas hot water heater capable of immediate response even when environmental oxygen concentration is insufficient and even when any clogging is produced in a heat exchanger. SOLUTION: A burner controller 30 applies voltage to a flame rod 38 located in a flame produced across a flame hole 22 of a burner 20 in a normal combustion state at an upper portion of the flame hole 22, and if a detected flame current has a predetermined judgement value or lower, the controller closes a gas solenoid valve 26 for supplying fuel gas to the burner. There is provided on an inner trunk skirt 10 a return flow pipe 13 having a return pipe part 13b an upper end of which return pipe part is opened to a combustion chamber on the lower side of the heat exchange 12, and which return pipe part includes the flame rod 38 at a lower part thereof and opened to the flame hole 22. When clogging is produced in the heat exchanger, combustion waste gas at an upper portion in the combustion chamber passes through the return flow pipe 13, and is returned to the neighborhood of the flame hole 22. The return flow pipe is preferably extended downward substantially straightforwardly and comprises a body part 13a, the lower end of which is released and a return pipe part 13b branched in the course of the body part 13a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for preventing incomplete combustion used in a gas water heater in which a heat exchanger provided above an inner skirt is heated by a burner.

[0002]

2. Description of the Related Art As a device for preventing incomplete combustion of a gas water heater of this kind, for example, as disclosed in Japanese Utility Model Laid-Open Publication No. Sho 61-18358, a device is provided in a state where a combustion is normally performed above a burner port of a burner. A thermocouple is provided at a position inside the flame to be generated, and when the output voltage of the thermocouple falls below a predetermined judgment value, the gas solenoid valve for supplying fuel gas to the burner is closed, and the upper part of the inner body skirt (heat An opening is provided on the lower side of the exchanger), a secondary thermocouple faces the opening, and the thermocouple is connected to the thermocouple in a reverse characteristic. When a gas water heater is installed in a room, if the oxygen concentration in the room decreases due to continued use with insufficient ventilation, incomplete combustion will occur, causing a burner flame to lift and the base of the flame to rise. The length of the unburned gas portion of the part becomes large. As a result, in the above-described incomplete combustion prevention device, the thermocouple enters the unburned gas portion and the output voltage decreases.Therefore, the gas solenoid valve is closed to stop the supply of fuel gas to the burner, thereby causing incomplete combustion due to lack of oxygen. Preventing.

Further, if the heat exchanger provided above the inner skirt becomes clogged and the amount of combustion air becomes insufficient, incomplete combustion occurs even if the oxygen concentration in the installation environment is normal.
In this case, no lift is generated in the flame of the burner, so that the above-described in-flame thermocouple (primary thermocouple) alone cannot prevent incomplete combustion due to such a cause. In order to solve this, in addition to the primary thermocouple provided above the burner flame as described above, a secondary thermocouple facing the opening provided on the upper side wall of the inner trunk skirt from the outside is provided. The two thermocouples are connected in series with opposite polarities, and the gas solenoid valve for supplying fuel gas to the burner is closed when the combined output voltage becomes equal to or less than a predetermined determination value.

[0004] In this technique, when the heat exchanger or the like is not clogged, the combustion gas hardly flows out from the opening in the upper side wall of the inner skirt, so that the output voltage of the thermocouple is almost zero. Thus, the voltage of the thermocouple provided above the burner opening of the burner is output substantially as it is. Therefore, when the oxygen concentration in the room decreases, incomplete combustion is prevented by the same operation as described above. If the heat exchanger becomes clogged, the pressure in the upper part of the inner skirt rises and the combustion gas flows out of the opening, so the thermocouple exposed to the opening is heated and its output voltage increases, The combined output voltage is reduced by that amount, and when the output voltage falls below the determination value, the supply of the fuel gas to the burner is stopped. This also prevents incomplete combustion due to clogging of the heat exchanger and the like.

[0005]

Although the above technology satisfies a certain function, the thermocouple has a certain amount of heat capacity, so that the heating and cooling are delayed, and the response is delayed. There's a problem. In particular, the thermocouple provided above the burner opening of the burner usually also has the function of detecting misfire to the burner at the start of operation of the gas water heater, but it takes several seconds to detect misfire by the thermocouple. Since there is a time delay (for example, 10 seconds), there is a problem that the time of release of unburned gas is prolonged in the case of misfire. In order to solve this, non-ignition to the burner is also detected by detecting the flame current using a flame rod provided separately from the thermocouple, but using both the thermocouple and the flame rod is performed. However, there is a problem that the cost increases. In the above prior art, it is conceivable to replace the thermocouple provided above the burner opening with a flame rod, but the thermocouple facing the opening of the upper side wall of the inner trunk skirt in the above prior art is referred to as a frame rod. Since replacement is essentially impossible, such replacement can prevent incomplete combustion due to insufficient oxygen concentration in the room, but does not prevent incomplete combustion due to clogging of heat exchangers and the like. Can not. An object of the present invention is to solve such problems.

[0006]

According to the present invention, there is provided an apparatus for preventing incomplete combustion of a gas water heater, comprising: an inner skirt; a heat exchanger provided continuously above the inner skirt; The present invention relates to a gas water heater comprising a burner provided at a lower portion and heating water supplied through a heat exchanger by the burner. A flame rod located in the flame to be generated, and a voltage is applied to the flame rod to detect a flame current passing through the flame rod. If the flame current is equal to or less than a predetermined determination value, fuel gas is supplied to the burner. It has a burner controller for closing the gas solenoid valve, and a return pipe section for the combustion waste gas which is open at the upper end into the inner skirt below the heat exchanger and opens toward a flame port provided with a frame rod at the lower part. It is characterized in further comprising a flow tube.

[0007] If the oxygen concentration in the environment such as a room where a gas water heater is installed is insufficient and the combustion becomes incomplete, a lift is generated in the burner flame, and the length of the unburned gas portion at the base of the flame becomes large. become. As a result, if the flame rod enters the unburned gas portion, the flame current decreases immediately in response to this, and if the flame current falls below a predetermined judgment value, the burner controller closes the gas solenoid valve to supply fuel gas to the burner. Stop. When the heat exchanger is clogged, the pressure in the upper portion of the inner skirt rises, and the combustion waste gas in that portion passes from the upper end of the reflux pipe through the main body and the return pipe to the frame rod. It will be returned toward the provided flame outlet.
As a result, the amount of oxygen supplied to the vicinity of the flame outlet is reduced, so that a lift occurs in the flame in that portion. As described above, the flame current is immediately reduced in response to the lift, and when the flame current falls below a predetermined determination value, the burner controller is controlled. Closes the gas solenoid valve and stops the supply of fuel gas to the burner. If the burner is not ignited for some reason at the start of operation of the gas water heater, no flame current flows through the flame rod, so the burner controller immediately closes the gas solenoid valve and releases fuel gas to the burner. Stop supply.

The reflux pipe comprises a main body part extending substantially straight downward from the upper end thereof and having a lower end opened outside the inner trunk skirt, and a return pipe part branched from the middle of the main body part. Is preferred. When the burner is ignited, the pressure in the inner skirt increases instantaneously and the flow of the combustion waste gas returned from the return pipe increases. In this case, most of this flow is generated by the main body of the return pipe. A small amount of combustion waste gas is discharged from the lower end of the fuel tank and returned from the return pipe toward the flame outlet. Therefore, the lift of the flame due to the return of the combustion waste gas to the flame outlet at the time of ignition is slight, and the detection of ignition does not become uncertain.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The accompanying drawings show an embodiment in which the present invention is applied to a gas instantaneous water heater. As shown in FIG. 1, a heat exchanger 12 composed of heat transfer tubes 12a and fins 12b is provided above an inner skirt 10 forming a combustion chamber 14 of a gas instantaneous water heater, and a main burner is provided below. 2
0 is provided. The inlet side of the heat transfer pipe 12a is connected to a water supply pipe 15 via a preheating pipe 11 wound around the inner body skirt 10, and a hot water supply plug 17 is provided on a hot water supply pipe 16 connected to the outlet side. The water supply pipe 15 is provided with a water-side controller 18 using a diaphragm that moves a rod 18a to operate a water pressure responsive valve 28 and a water flow switch 31 described later when the amount of water supply exceeds a predetermined amount. Although not shown, the water side controller 18 has a water supply pipe 15.
There is provided a manual valve for manually adjusting the flow rate from the air to the heat exchanger 12 to adjust the tap water temperature.

[0010] As shown in FIG.
The fuel gas is supplied via a gas supply pipe 25 in which a gas solenoid valve 26, a capacity adjusting valve 27, and a water pressure responsive valve 28 are provided in series.
The gas solenoid valve 26 is controlled to be opened and closed by a current flowing from the burner controller 30 to the operating coil 26a, and the capacity adjustment valve 27 is manually adjusted to adjust the gas supply amount to the main burner 20 so that the hot water is supplied. It changes the tapping capacity of the vessel. The water pressure responsive valve 28 is a heat exchanger 1
2 is opened and closed by the rod 18a of the water-side controller 18 so as to be opened when a predetermined amount or more of water is supplied. As soon as the hydraulic valve 28 is opened, the rod 18
The cam 18b provided at a turns on the water flow switch 31.

Each burner unit 21 is made of sheet metal and has a large number of flame ports 22 arranged in two rows as shown in FIGS. 1 and 2, and each flame port 22 is partitioned by a partition plate 22a. Have been. The lower end of the heat exchanger 12 is connected to the upper end of the combustion chamber 1 through a hole formed in the side wall of the inner skirt 10.
The body portion 13a of the reflux pipe 13 opened to the upper part of the pipe 4 extends straight downward along the outside of the side wall of the inner skirt 10, and the lower end is opened to the atmosphere in the gas water heater. The return pipe portion 13b of the branched combustion waste gas passes through a notch formed in a lower portion of the inner trunk skirt 10 and opens toward a flame opening 22 that forms a flame into which the frame rod 38 is inserted. The frame rod 38 is supported by the insulator 38a so that the tip thereof has a height that enters the flame generated in the flame port 22 in a normal combustion state.

Next, an outline of the burner controller 30 will be described with reference to FIG. In this embodiment, the power source 40 is a dry battery, and the voltage monitor circuit 32, the solenoid valve drive circuit 33, the ignition circuit 34, the timer circuit 35, the constant voltage circuit 36, the frame guard circuit 37, and the safety The circuit 39 is connected. Solenoid valve drive circuit 33
Receives an input from the timer circuit 35, passes a current through the operating coil 26a to open the gas solenoid valve 26, activates the ignition circuit 34, ignites the burner 20 by the ignition plug 34a, and If the detected value of the flame current input from the circuit 37 is equal to or less than a predetermined determination value, the current to the operation coil 26a is stopped and the gas solenoid valve 26 is closed. The operating coil 26a has an adsorption coil 26b that needs to flow a large current to open the closed gas solenoid valve 26, and a holding device that only needs to flow a small current to keep the gas solenoid valve 26 once opened. The coil 26c is provided.

The frame guard circuit 37 includes a constant voltage circuit 36.
Receiving a constant voltage output from the
A predetermined voltage is applied to the solenoid valve driving circuit 33 to detect a flame current passing through the frame rod 38 and to output a signal corresponding to the detected value.
Is output to Since the flame current changes instantaneously in response to the change of the flame, the output of the signal to the solenoid valve driving circuit 33 is also performed substantially without a time delay. The frame guard circuit 37 has a replaceable gas type connector 37a in order to adjust the determination value according to the type of gas used.
Is provided. The safety circuit 39 monitors whether there is an abnormality in the operation of the frame guard circuit 37, and stops the operation of the gas water heater when an abnormality occurs. When the voltage of the power supply battery 40 falls below a predetermined limit, the voltage monitoring circuit 32 turns on the indicator light 32a to urge replacement of the battery.

Next, the operation of the above embodiment will be described.
When the hot water tap 17 is opened and the amount of water supplied through the water supply pipe 15 exceeds a predetermined amount, the water pressure switch 28 is opened and the water flow switch 31 is opened at the same time.
Is turned on, and the burner controller 30 starts operating. First, the solenoid valve driving circuit 33 is activated to operate the suction coil 26b.
A large current is passed through the valve to open the closed gas solenoid valve 26. After a predetermined time (for example, 2 seconds), the large current is released, a small current is passed through the holding coil 26c, and the gas solenoid valve 26 is continuously opened. Then, the fuel gas is supplied to the main burner 20. As soon as the water flow switch 31 is turned on, the ignition circuit 3
4 operates to generate sparks at an ignition plug 34a (not shown) provided near the flame port 22 of the burner 20, and the main burner 2
After a short period of time when the fuel gas erupting from zero ignites and combustion stabilizes, the frame guard circuit 37
After detecting the flame current passing through the ignition circuit 34, the ignition circuit 34 stops operating. If the detected flame current is equal to or less than a predetermined determination value, it is determined that the combustion state is defective due to an ignition mistake or some cause, the current to the holding coil 26c is stopped, the gas solenoid valve 26 is closed, and the main burner 20 Of the fuel gas is stopped to stop the operation of the gas water heater.

When the main burner 20 is normally ignited, the flame current passing through the frame rod 38 is equal to or greater than a predetermined judgment value, so that the gas water heater continues to operate with the gas solenoid valve 26 opened. The water supplied through the heat exchanger 12 is heated by the main burner 20 and discharged from the hot water tap 17.
When the hot-water tap 17 is closed, the water pressure switch 28 is closed, and at the same time, the water flow switch 31 is turned off, and the gas water heater stops operating. In the operating state, incomplete combustion occurs when the oxygen concentration in the air in the environment where the gas water heater is installed is reduced, or when the amount of combustion air is insufficient due to clogging of the passage of combustion air. The operation in each case will be described below.

First, the action of preventing incomplete combustion in the case where the passage of the combustion air is not clogged but the oxygen concentration in the air is reduced will be described. When the gas water heater is installed in a room, if the gas water heater is continuously used without sufficient ventilation, the oxygen concentration in the room gradually decreases and incomplete combustion occurs. This can be explained with reference to FIG. 4. When the oxygen concentration decreases, the ratio CO /
CO ₂ increases at an accelerating rate. In addition, a lift is generated in the flame generated at the flame opening 22 of the main burner 20 as the oxygen concentration decreases, and the length of the unburned gas portion generated at the base of the flame gradually increases. As a result, in the normal combustion state, the tip end of the frame rod 38 which has been in the burning flame gradually moves into the unburned gas portion, and the flame current gradually decreases as indicated by I in FIG. Frame guard circuit 37 detects the flame current I through the flame rod 38, the electromagnetic valve driving circuit 3 whose value is a predetermined judgment value I ₀ follows since the point A
3 stops the current to the holding coil 26c, closes the gas solenoid valve 26, stops the supply of the fuel gas to the main burner 20, and stops the operation of the gas water heater. This judgment value I ₀
Is, for example, 1 μA, and the value of the ratio CO / CO ₂ at that time is, for example, 0.035. Prevention of incomplete combustion in the case where the oxygen concentration in the air decreases is performed in this manner. In this case, the flow of the combustion waste gas through the reflux pipe 13 does not substantially occur.

Next, although the oxygen concentration in the air is normal,
A description will be given of the effect of preventing incomplete combustion when the fins 12b of the heat exchanger 12 provided on the upper side of the inner trunk skirt 10 are clogged with combustion products and the like, and the flow of air deteriorates and the amount of combustion air becomes insufficient. I do. As such clogging increases, the pressure in the upper part of the combustion chamber 14 formed between the inner skirt 10, the heat exchanger 12, and the main burner 20 gradually increases. In this case, even if incomplete combustion occurs due to clogging of the heat exchanger 12 or the like, the flame generated in the flame outlet 22 hardly lifts. However, in the above-described embodiment in which the reflux pipe 13 is provided, the heat exchanger 1
2, as the clogging due to combustion products and the like increases and the pressure in the upper part of the inside of the combustion chamber 14 rises, a frame rod 38 is provided from the main body 13a of the reflux pipe 13 through the return pipe 13b as shown by a solid arrow. The amount of combustion waste gas in the upper part of the combustion chamber 14 returned to the vicinity of the burned port 22 gradually increases. As a result, the oxygen concentration of the combustion air in the vicinity of the flame 22 decreases, so that the flame generated in the flame 22 gradually lifts, and the length of the unburned gas generated at the base of the flame gradually increases. . As a result, as in the case described above, the frame rod 3 in the burning flame in the normal combustion state
As the tip of 8 gradually moves into the unburned gas portion, the flame current gradually decreases. Frame guard circuit 37 detects the flame current through the flame rod 38, the electromagnetic valve drive circuit 33 if the value is a predetermined reference value I ₀ or less stops current to holding coils 26c, to the main burner 20 The supply of the fuel gas is stopped to stop the operation of the gas water heater. In this embodiment, this determination value is also 1 μA,
By adjusting the shape and size of the reflux pipe 13, particularly the shape and size of the return pipe portion 13b, it is possible to appropriately select the closing rate of the passage area of the heat exchanger 12 for stopping the operation of the gas water heater. Prevention of incomplete combustion when the heat exchanger 12 is clogged is performed in this manner.

FIG. 5 is a diagram showing the temporal change of the flame current from the start of operation in the gas water heater of the above embodiment in which the heat exchangers 12 have different closing rates. The operation when clogging occurs will be further described. When the clogging rate of the heat exchanger 12 is 0% (not clogged at all), the flame current increases rapidly if the fuel gas is ignited at the start of operation, then decreases rapidly, then increases again. Converge to the value. The flame current drops sharply after ignition because the inner skirt 10
This is because the pressure in the inside instantaneously increases and the flow of the combustion waste gas returned from the reflux pipe 13 increases, causing an instantaneous lift in the flame. In this embodiment, most of this flow is Since the amount of combustion waste gas discharged from the lower end of the main body 13a of the thirteen and returned from the return pipe portion 13b toward the flame port 22 is small, the decrease in flame current is not so large. However, by bending the lower part of the return pipe 13, the return pipe part 13 b
Is formed to return all the combustion waste gas to the flame port 22, the temporary decrease in the flame current becomes considerably large.

FIG. 5 shows the temporal change of the flame current from the start of the operation. As shown in FIG. 5, as the closing rate of the heat exchanger 12 increases, it does not change much at first, but if the closing rate becomes somewhat large. It becomes lower gradually. This is because, as described above, as the blockage rate increases, the amount of combustion waste gas returned from the return pipe portion 13b to the vicinity of the flame port 22 provided with the frame rod 38 increases, and the lift of the flame increases. Since in the example of FIG. 5 temporary lowering of the flame current when occlusion content became about 35% reaches a determination value I _0, the blockage ratio is more electromagnetic valve driving circuit 33 is a gas hot water closes the gas solenoid valve 26 Stop the operation of the boiler.

In the above embodiment, the main body 13a of the return pipe 13 extends substantially straight downward to release the lower end, and the return pipe 13b branches off halfway. Since the temporary decrease in the flame current immediately after the ignition is reduced, the detection of the ignition performed immediately after the ignition does not become unstable. However, the present invention may be implemented such that the return pipe portion 13 b is formed by bending the lower part of the reflux pipe 13 to return all the combustion waste gas to the flame port 22. In this case, the temporary decrease in the flame current immediately after ignition becomes large, but before this temporary decrease occurs (for example, for 2 seconds from the start of operation of the ignition circuit), the ignition is detected, and the incomplete combustion due to the flame current is detected. May be performed after a lapse of a considerable time (for example, one minute).

In the above embodiment, the present invention is applied to a gas water heater of a type in which the main burner is directly ignited by an ignition plug. However, the present invention relates to a system in which a main burner is ignited by a pilot burner. It is also possible to apply the present invention to a gas water heater. In this case, a frame rod may be provided in the pilot burner, and the return pipe portion 13b of the return pipe 13 may be directed to the pilot burner. Further, the present invention is not limited to the gas water heater of the pre-stop type as in the above embodiment, but can be applied to a gas water heater of the original stop type.

[0022]

As described above, according to the present invention, either incomplete combustion when the oxygen concentration in the environment such as a room is insufficient or incomplete combustion when the heat exchanger or the like is clogged is used. Immediately, the flame current decreases, and when the flame current falls below a predetermined determination value, the supply of the fuel gas to the burner is stopped. Therefore, incomplete combustion of the gas water heater can be prevented without time delay. In addition, even if the burner is not ignited, the supply of the fuel gas to the burner is immediately stopped in response to the ignition, so that the time for releasing the unburned gas in the case of non-ignition can be shortened.

Further, according to the return pipe, the main body of which is extended substantially straight downward, the lower end is released, and the return pipe is branched in the middle thereof. Since the flame lift caused by the return of the combustion waste gas to the flame opening due to the instantaneous increase of the flame is small, the detection of the ignition by the flame rod is performed stably.

[Brief description of the drawings]

FIG. 1 is a view showing an entire structure of an embodiment of a device for preventing incomplete combustion of a gas water heater according to the present invention.

FIG. 2 is an enlarged partial top view of a main part taken along line 2-2 of FIG.

FIG. 3 is a configuration diagram of a burner controller of the embodiment shown in FIG.

FIG. 4 is a diagram showing a flame current and a degree of incomplete combustion with respect to an oxygen concentration in the embodiment shown in FIG. 1;

FIG. 5 is a diagram showing a temporal change of a flame current from the start of operation in the case where the closing rates are different in the embodiment shown in FIG. 1;

[Explanation of symbols]

10: inner trunk skirt, 12: heat exchanger, 13: reflux tube,
13a: body part, 13b: return pipe part, 20: burner (main burner), 22: flame outlet, 26: gas solenoid valve, 30 ...
Burner controller, 38 ... Frame rod.

Claims (2)

[Claims] 1. An inner body skirt, a heat exchanger provided continuously above the inner body skirt, and a burner provided below the inner body skirt, and water supply passing through the heat exchanger. In the gas water heater, which is heated by the burner, a flame rod located in a flame generated in the flame port in a normal combustion state above the flame port of the burner, and a voltage is applied to the flame rod. A burner controller that closes a gas solenoid valve that supplies fuel gas to the burner if the flame current is applied and detects a flame current that passes through the flame rod and the flame current is equal to or less than a predetermined determination value. A gas pipe provided with a return pipe having a return pipe section for the combustion waste gas, which is opened at the lower side into the inner body skirt and opens toward the flame port provided with the frame rod at a lower part. Incomplete combustion prevention device for the boiler. 2. The reflux pipe comprises a main body part extending substantially straight downward from the upper end part and having a lower end opened outside the inner trunk skirt, and the return pipe part branched from the middle of the main body part. The incomplete combustion prevention device for a gas water heater according to claim 1.