JP4078496B2 - Oxygen deficiency detection method in gas water heater - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gas water heater. Specifically, the present invention relates to a technique for preventing incomplete combustion in a gas water heater.
[0002]
[Prior art]
The gas hot water heater burns gas with a gas burner and heats water by exchanging heat between the heat of the combustion gas and water in the heat exchanger to discharge hot water. Such a gas water heater consumes oxygen in the air and burns the gas, and is designed to completely burn at a constant air-fuel ratio. Therefore, it is usually installed outdoors, and installation in a sealed environment or situation is prohibited.
[0003]
[Problems to be solved by the invention]
However, in the actual installation situation, even if the gas water heater is enclosed in a hut or installed on the outer wall of a house for the purpose of protecting the gas water heater from snow or strong winds or preventing mischief. A box-shaped enclosure may be provided around. In such a case, ventilation in the place where the gas water heater is installed becomes insufficient, so oxygen in the air for burning the gas burner of the gas water heater gradually becomes insufficient, and the gas burns incompletely. Soot accumulates in the gas burner or hot water at the set temperature is not discharged. Furthermore, when the gas water heater is installed in an unauthorized manner, there is a risk of carbon monoxide poisoning if CO gas generated due to incomplete combustion leaks into the room or room.
[0004]
The present invention has been made to solve the technical problems described above, and the object of the present invention is to perform incomplete combustion when oxygen for burning the gas is insufficient. It is providing the gas water heater provided with the function to detect.
[0005]
DISCLOSURE OF THE INVENTION
Anoxia detection method in the gas water heater according to the present invention, by burning the gas combustion unit heating the heat exchanger, a Contact Keru anoxia detection method in gas water heater for heating water passing through the heat exchanger A combustion temperature detector for measuring the combustion temperature in the gas combustion section, and a blower for supplying combustion air to the gas combustion section, and the combustion temperature is measured by the temperature detector after a predetermined time. By measuring, the step of detecting the decrease rate V of the combustion temperature of the gas combustion section (however, when the combustion temperature decreases, V <0), and the decrease rate V of the combustion temperature detected in the detection step are For the predetermined value Ve (<0) V ≦ Ve In this case, the amount of air blown by the blower is increased or decreased sequentially, and if the rate of decrease in the combustion temperature does not become V> 0 even if the amount of air flow is increased or decreased, the oxygen deficient state is maintained. And a step of forcibly stopping the combustion of the gas combustion unit when it is determined that there is a lack of oxygen in the determination step .
[0006]
When the oxygen in the gas combustion section is deficient, the temperature of the gas combustion section decreases due to incomplete combustion. However, the combustion temperature may decrease due to other causes such as a change in the combustion capacity of the gas combustion section. Therefore, if the combustion of the gas combustion unit is stopped immediately when the rate of decrease in the combustion temperature of the gas combustion unit becomes equal to or less than a predetermined value, a gas water heater that is not in an oxygen-deficient situation may be erroneously stopped.
[0007]
Therefore, the present invention does not immediately stop the combustion of the gas combustion section when the combustion temperature lowering rate falls below a predetermined value, but instead increases or decreases the amount of air blown by the blower in order to decrease the combustion temperature lowering rate. It was made to detect. At this time, if the cause of the decrease in the combustion temperature is due to a change in the gas combustion capacity, the combustion temperature of the gas combustion section can be increased by adjusting the air-fuel ratio by changing the air flow rate of the blower. On the other hand, in the case of oxygen shortage, the combustion temperature decreases even if the amount of blown air is changed due to the progress of oxygen shortage. Therefore, in the present invention, if the rate of decrease in the combustion temperature does not become V> 0 even if the blast volume is increased or decreased, it is determined that the oxygen deficient state is present and the combustion of the gas combustion unit is stopped. I made it.
[0008]
Therefore, according to the present invention, it is possible to determine the cause of non-oxygen shortage such as oxygen shortage in the gas combustion section and fluctuation of combustion capacity, and the accuracy of detection of oxygen shortage in the gas combustion section can be increased. The risk of stopping the combustion of the gas combustion section can be reduced.
[0009]
Further, in the embodiment of the present invention, in the determination step, when the decrease rate of the combustion temperature becomes V> 0 when the flow rate is increased or decreased, the flow rate of the blower is set as follows. The gas combustion part is returned to the original state and maintained in the combustion state.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
FIG. 1 is a schematic diagram showing the configuration of a gas water heater according to an embodiment of the present invention. A heat exchanger 2 is disposed in the upper part of the can body 1, a water inlet pipe 3 is connected to the water inlet side of the heat exchanger 2, and a hot water pipe 4 is connected to the outlet side of the heat exchanger 2. It is connected. The inlet pipe 3 has an incoming water temperature sensor (thermistor) 5 for detecting the temperature of the water flowing into the heat exchanger 2 and the flow rate of the water flowing into the heat exchanger 2 from the city water through the inlet pipe 3. A flow sensor 6 for detection is provided. Further, the tapping pipe 4 is provided with a tapping temperature sensor 7 for detecting the temperature of the hot water flowing out from the heat exchanger 2.
[0015]
A bypass pipe 9 is provided between the water inlet pipe 3 and the hot water outlet pipe 4 so as to bypass the heat exchanger 2, and a bypass flow rate adjusting valve 15 is provided in the bypass pipe 9. Thus, the water flowing into the inlet pipe 3 from city water or the like is distributed to the heat exchanger 2 side and the bypass pipe 9 side, and the hot water heated by the heat exchanger 2 and the water passed through the bypass pipe 9 are again. It is mixed in the tap pipe 4. A mixing temperature sensor 8 for detecting the hot and cold water mixing temperature and a flow rate control valve 16 for controlling the flow rate of the entire appliance are provided downstream of the joining position of the hot water pipe 4 and the bypass pipe 9.
[0016]
In the can 1, a gas burner 10 is installed below the heat exchanger 2. In the gas burner 10, the combustion capacity of the gas burner 10 is adjusted by switching the number of combustion tubes. A plurality of gas switching valves 11a to 11e are incorporated. Further, a gas proportional valve 13 and an original electromagnetic valve 14 are provided in the gas pipe 12 for supplying gas to the gas burner 10. A burner sensor (combustion temperature sensor) 17 such as a thermistor is provided at the gas combustion position of the gas burner 10 and directly detects the combustion temperature by heat conduction by touching the combustion flame. If such a burner sensor 17 is used, the combustion temperature of the gas burner 10 can be measured with higher accuracy than a frame rod or the like.
[0017]
A blower 18 for supplying combustion air to the gas burner 10 and burning the gas at an appropriate air-fuel ratio is provided below the gas burner 10, that is, at the bottom of the can 1. Yes.
[0018]
Therefore, in this gas water heater, when water flows in from the inlet pipe 3, the water branches into the heat exchanger 2 side and the bypass pipe 9 side, and the water passing through the heat exchanger 2 is the heat exchanger 2. The water is heated when passing through the water, mixed with the water that has passed through the bypass pipe 9 again, and discharged from a currant or the like provided at the end of the hot water discharge pipe 4.
[0019]
Further, in this gas water heater, a desired hot water temperature (set temperature Ts) can be input from a remote controller, and the controller includes a water temperature sensor 5, a hot water temperature sensor 7, a flow rate sensor 6, a mixing temperature sensor 8, and the like. Based on the detected value, the gas proportional valve 13 is subjected to feedforward (FF) control and feedback (FB) control, so that the combustion capability of the gas burner 10 is controlled so that hot water having a set temperature is discharged from a currant or the like.
[0020]
As shown in FIG. 1, the controller 19 includes an oxygen deficiency determination unit 21 and a timer 20. The timer 20 measures the elapsed time after the combustion of the gas burner 10 is started. The oxygen deficiency determination unit 21 reads the measured value (burner sensor temperature) of the burner sensor 17 every time a predetermined time elapses, calculates the rate of decrease in the combustion temperature of the gas burner 10 from the burner sensor temperature, and based on the result. The state of oxygen deficiency (hereinafter referred to as oxygen deficiency) is monitored.
[0021]
This will be specifically described with reference to FIGS. FIG. 2 shows a change in the burner sensor temperature after the start of combustion when the gas burner 10 normally burns, and FIG. 3 shows a change in the burner sensor temperature after the start of combustion in an oxygen deficient state. Immediately after the gas burner 10 starts to burn, the burner sensor temperature rises. However, when the gas burner 10 burns normally, after a certain period of time, as shown in FIG. It settles at an almost constant temperature. On the other hand, when the gas burner 10 is in an oxygen deficient state, the burner sensor temperature is lowered as shown in FIG. 3, and as the oxygen deficient state progresses, the rate of decrease in the burner sensor temperature (decreasing gradient) gradually increases. Therefore, the oxygen deficiency determination unit 21 takes in the burner sensor temperatures Tb1, Tb2, Tb3,... Every time a predetermined time t ₀ (for example, 5 seconds) elapses, and the descending speed V
ΔTb ₂₁ / t ₀ = (Tb2−Tb1) / t ₀ ,
ΔTb ₃₂ / t ₀ = (Tb3−Tb2) / t ₀ ,
...
Is calculated. When the rate of decrease V of the burner sensor temperature becomes equal to or lower than a certain value Ve (V ≦ Ve <0), it is determined that the oxygen burnout is present, and the combustion of the gas burner 10 is forcibly stopped. The monitor 22 displays an oxygen deficiency state.
[0022]
However, (1) When the initial burner temperature rises after ignition of the gas burner, (2) Immediately after the combustion capacity of the gas burner 10 is switched, (3) The rotational speed of the blower 18 changes (for example, the rotational speed changes due to correction). Immediately after, the combustion temperature of the gas burner 10 becomes unstable. In these cases, a dead time of a certain time (for example, about 1 to 3 minutes) is provided so that the burner sensor temperature is not read. Or the oxygen deficiency determination unit 21 is stopped so that the determination of oxygen deficiency is not performed.
[0023]
Further, in order to reduce the risk of erroneous determination due to disturbance such as strong winds, it is determined that there is an oxygen deficient state when the rate of decrease in the burner sensor temperature has become a certain value Ve or less for a certain number of times (for example, 3 times). May be.
[0024]
Further, in order to prevent erroneous determination due to disturbance due to typhoon or other strong wind, it is determined that there is no oxygen deficiency when the burner sensor temperature decreasing speed V is smaller than a certain value Vmax (<Ve <0). May be. That is, in this case,
V> Ve ... Normal Ve≥V> Vmax ... Oxygen deficient state Vmax≥V ... Normal (strong wind)
It is judged. In general, in the absence of oxygen due to poor ventilation, the temperature drop of the combustion temperature is slow and continues for a long time.On the other hand, if the temperature rises once during strong winds and then drops during no winds, Since the temperature rapidly decreases, the detection accuracy of the oxygen deficiency state can be increased by using such a determination formula.
[0025]
Further, the average value of the burner sensor temperature decreasing speed may be used, and it may be determined that the oxygen deficiency is present when the average value is equal to or less than a certain value Ve. In that case, the burner sensor temperature is read a plurality of times (for example, 6 times every 10 msec) within a certain time, and the highest value and the smallest value are discarded and the average value of the remaining burner sensor temperatures is used. You can also. Alternatively, in order to suppress the influence of disturbances such as strong winds, the decreasing rate of the burner sensor temperature smaller than the constant value Vmax (<Ve <0) may be replaced with Vmax and averaged.
[0026]
(Specific processing procedure)
4 and 5 show specific procedures for determining the oxygen deficiency state in the gas water heater. Hereinafter, this specific procedure will be described. When defect determination due to lack of oxygen starts (S1), it is first determined whether combustion is in progress or combustion is stopped (S2). If combustion is in progress, it is checked whether the number of hot water discharged from the gas water heater is equal to or greater than a certain number NA (for example, number 8) (S3). If it is smaller than the certain number NA, the process is terminated (S5). If the fixed number NA is greater than or equal to, it is further checked whether the variation in the tapping number is below the certain number NB (S4). If the variation in the tapping number is large, determination accuracy cannot be obtained. If so, the process ends (S5).
[0027]
If the variation in the number of hot water discharged from the gas water heater is equal to or less than a certain number NB, it is checked whether the combustion capacity of the gas burner 10 is within a certain time ta after switching the combustion capacity (S6). If the predetermined time ta has not elapsed, the determination of the lack of oxygen is not performed as described above, and the process waits until the predetermined time ta elapses.
[0028]
After the change of the combustion capacity of the gas burner 10, if it is not within a certain time ta, or if the certain time ta has elapsed, is the rotation time of the blower 18 continuously corrected and changed within a certain time tb? Check (S7). When the fixed time tb has not elapsed, the determination of the lack of oxygen is not performed as described above, and the process waits until the fixed time tb has elapsed.
[0029]
When the rotation speed of the blower 18 is not corrected and is not within the fixed time tb or when the fixed time tb has elapsed, the oxygen deficiency determination unit 21 determines whether or not the burner sensor temperature lowering speed V is equal to or less than the fixed value Ve. (S8). As this determination method, any of the above-described various methods may be used. Here, when it is determined that the burner sensor temperature lowering speed V is larger than the constant value Ve and it is not in an oxygen deficient state, the flag F in the controller 19 is set to 1 (S9), and the first step S2 is performed. Return.
[0030]
Therefore, the gas burner 10 continues to burn while the flag is kept at F = 1 while it is determined that the rate of decrease V of the burner sensor temperature is greater than the constant value Ve and is not in an oxygen deficient state.
[0031]
When combustion is continued in this way, the burner sensor temperature decreasing speed V becomes equal to or less than a certain value Ve, and if the oxygen deficiency determination unit 21 determines that the oxygen deficiency is present in step S8, the flag F is replaced with 0 ( In step S10, the normal count counter CA is cleared to 0 (S11), and the abnormal count counter CB is incremented by 1 (S12).
[0032]
After the counter CB is added, it is checked whether or not the counter CB is a predetermined value, for example, 5 or more (S13). If the counter CB is smaller than the predetermined value, the determination is terminated and the determination is started from the beginning (S14, S15). If the value of the counter CB is equal to or greater than the predetermined value, it is determined that the oxygen deficiency determination unit 21 has been in the oxygen deficient state a predetermined number of times. ) The combustion of the gas burner 10 is forcibly stopped, and the monitor 22 displays an oxygen deficient state. Thereafter, the counter CB is cleared to 0 (S17), the determination is terminated, and the determination process is repeated from the beginning (S18).
[0033]
If the gas water heater has stopped burning (NO in S2), it is determined whether the flag F is 0 or 1 (S19). If the flag is F = 1, the oxygen deficiency determination unit. Since it has not been determined that the state has been deficient in oxygen even once by 21, the counter CA for counting the normal number of times is incremented by 1 (S20), and then the flag F is set to 0 (S21). Next, it is checked whether or not the count value of the counter CA is a predetermined value, for example, 3 or more (S22). If it is equal to or less than the predetermined value, the determination is terminated and the process is repeated from the beginning (S25, S26).
[0034]
In the first process after the normal combustion stop, the counter CA is incremented by 1 as described above, and then the flag is set to F = 0. It is determined as NO, and the counter CA does not increase. If the oxygen deficiency determination unit 21 determines that there is an oxygen deficiency in step S8, the flag is set to F = 0 in step 10. Therefore, even if the combustion is stopped thereafter, NO is determined in step S19. The counter CA is not incremented.
[0035]
However, if the oxygen deficiency determination unit 21 determines in step S8 that it is in an oxygen deficient state, the counter CA for counting the normal number of times is cleared in step S11, while if the gas water heater ends combustion in a normal state, the step Since the flag is set to F = 1 in S9, the counter CA is incremented by 1 in step S20 in the first determination process after the end of combustion. Therefore, when the gas water heater ends combustion in a normal state for a predetermined number of times (for example, three times) continuously, the counter CA becomes equal to or greater than the predetermined value, the determination result in step S22 is YES, and the counter CB for counting the abnormal number of times And the counter CA for counting the normal number of times is cleared to 0 (S23, S24), the determination is finished, and the determination process is repeated from the beginning (S25, S26).
[0036]
(Second Embodiment)
FIG. 6 is a schematic view showing the configuration of a gas water heater according to another embodiment of the present invention. In this embodiment, a blower control unit 23 that controls the rotational speed of the blower 18 is provided. In FIG. 6, the same components as those in the embodiment of FIG.
[0037]
In the gas water heater of this embodiment, the oxygen deficiency determination unit 21 detects that the rate of decrease V of the burner sensor temperature has become the predetermined value Ve or less by any of the methods described in the first embodiment. After that, it is possible to determine whether it is due to oxygen deficiency or due to causes other than oxygen deficiency, such as fluctuations in the combustion capability of the gas burner 10.
[0038]
That is, in this gas water heater, when the oxygen deficiency determination unit 21 determines that the rate of decrease V of the burner sensor temperature has become equal to or less than the predetermined value Ve, the blower control unit 23 changes the rotational speed of the blower 18 to change the gas burner. The oxygen supply amount with respect to 10 is changed.
[0039]
When the decrease in the decrease rate V of the burner sensor temperature is oxygen deficiency, as shown in FIG. 7, the burner sensor temperature decreases with the progress of oxygen deficiency, regardless of whether the rotational speed of the blower 18 is increased or decreased. Keep doing.
[0040]
On the other hand, when the decrease in the rate of decrease V of the burner sensor temperature is due to, for example, a change in the combustion capability of the gas burner 10 due to, for example, a change in the gas primary pressure, the blower 18 is shown in FIG. When the number of rotations is increased or decreased, in either case, the air-fuel ratio tends to be good, and the burner sensor temperature rises.
[0041]
Accordingly, in this gas water heater, when the burner sensor temperature falls at a lowering speed V equal to or lower than the predetermined value Ve, the rotational speed of the blower 18 is increased and decreased, and the burner sensor temperature in each case is monitored. Also in this case, if the burner sensor temperature falls, it is determined that the oxygen deficiency is present, the combustion of the gas burner 10 is forcibly stopped, and the monitor 22 displays that the oxygen deficiency is present. In either case, if the burner sensor temperature starts to rise, it is determined that the cause is other than oxygen deficiency, and the rotation speed of the blower 18 is restored to continue the combustion operation of the gas water heater. .
[Brief description of the drawings]
FIG. 1 is a schematic view showing a configuration of a gas water heater according to an embodiment of the present invention.
FIG. 2 is a diagram showing a change in burner sensor temperature after the start of combustion in a normal combustion state.
FIG. 3 is a diagram showing a change in burner sensor temperature after the start of combustion in an oxygen deficient state.
FIG. 4 is a flowchart showing a procedure for oxygen deficiency detection in the above-described gas water heater.
FIG. 5 is a flowchart showing a procedure for oxygen deficiency detection in the above-described gas water heater.
FIG. 6 is a schematic view showing a configuration of a gas water heater according to another embodiment of the present invention.
FIG. 7 is a diagram showing changes in burner sensor temperature when the rotational speed of the blower is changed in an oxygen deficient state.
FIG. 8 is a diagram showing a change in the burner sensor temperature when the number of rotations of the blower is changed in a state where the burner sensor temperature is lowered due to reasons other than oxygen deficiency.
[Explanation of symbols]
10 Gas Burner 17 Burner Sensor 18 Blower 20 Timer 21 Oxygen Deficiency Determination Unit 23 Blower Control Unit

Claims (2)

By burning the gas combustion unit heating the heat exchanger, a Contact Keru anoxia detection method in gas water heater for heating water passing through the heat exchanger,
A combustion temperature detector for measuring the combustion temperature in the gas combustion unit, and a blower for supplying combustion air to the gas combustion unit,
Detecting a combustion temperature falling speed V of the gas combustion section by measuring the combustion temperature with a predetermined time interval (provided that V <0 when the combustion temperature decreases);
The combustion temperature decrease rate V detected in the detection step is less than a predetermined value Ve (<0).
V ≦ Ve
In this case, the amount of air blown by the blower is increased or decreased sequentially, and if the rate of decrease in the combustion temperature does not become V> 0 even if the amount of air flow is increased or decreased, the oxygen deficient state is maintained. A process of determining that there is,
If it is determined in the determination step that there is an oxygen deficiency, the step of forcibly stopping the combustion of the gas combustion unit;
A method for detecting oxygen deficiency in a gas water heater. In the determination step, when the air flow rate is increased or decreased and the rate of decrease in the combustion temperature becomes V> 0, the air flow rate of the blower is returned to the original and the gas combustion unit is combusted. 2. The oxygen deficiency detection method in a gas water heater according to claim 1, wherein the oxygen deficiency detection method is maintained in a state .

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