Combustion device

Abstract

Whether the flame current is normal or not is determined by a judgment method that is tailored to the amount of gas supplied to the burner. [Solution] The setting unit 29 for setting the threshold of the water heater 1 sets the threshold based on the initial value, which is a detected value obtained by the detection unit 30 that obtains a detected value indicating the magnitude of the flame current during the initial period after combustion by the gas burner 4 has started, specific information, and the amount of gas supplied to the gas burner 4. The setting unit 29 sets the threshold so that the threshold becomes larger as the amount of gas supplied to the gas burner 4 increases, and the threshold becomes larger as the initial value increases, reflecting the degree of increase of the first relational expression F1.

Description

Technical Field

[0001] The present disclosure relates to a combustion device.

Background Art

[0002] Patent Document 1 describes a water heater. The water heater includes a heat exchanger, a burner, and a flame rod. The flame rod is located in the flame above the burner port of the burner, and a flame current passing through the flame rod is detected by applying a voltage to the flame rod. If the flame current is equal to or less than a predetermined determination value (for example, 1 μA or less), an abnormality is detected. When an abnormality is detected, a gas solenoid valve that supplies combustion gas to the burner is closed, thereby preventing incomplete combustion of gas.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] Since the value of the flame current varies depending on the gas supply amount, for example, even when the value of the flame current is small, the operation may be normal if the gas supply amount is small. Therefore, simply determining an abnormality by comparing the flame current with a fixed threshold may result in a determination of abnormality even when the device is operating normally.

[0005] One object of the present disclosure is to provide a combustion device capable of determining whether a flame current is normal by a determination method adapted to the amount of gas supplied to the burner.

Means for Solving the Problem

[0006] A combustion device according to one aspect of the present disclosure includes: a burner configured to combust gas; and A flame rod that outputs a flame current corresponding to the degree of combustion of the burner, A detection unit that acquires a detected value indicating the magnitude of the flame current output from the flame rod, A determination unit that determines whether the detected value is below a threshold, A setting unit for setting the threshold, A storage unit that stores specific information that identifies a first relational expression that associates the amount of gas supplied to the burner with the value of the flame current and determines the degree of increase such that the value of the flame current increases as the amount of gas increases. Equipped with, The setting unit sets the threshold based on the initial value, which is the detected value acquired by the detection unit during the initial period after combustion by the burner has started, the specific information, and the amount of gas supplied to the burner, in a manner that reflects the degree of increase of the first relational expression, by increasing the threshold as the amount of gas supplied to the burner increases and increasing the threshold as the initial value increases. [Effects of the Invention]

[0007] According to the technology disclosed herein, it is possible to determine whether or not the flame current is normal using a determination method that is tailored to the amount of gas supplied to the burner. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a front view illustrating the external appearance of a water heater according to the first embodiment. [Figure 2] Figure 2 is a schematic circuit diagram that conceptually illustrates the internal configuration of the water heater shown in Figure 1. [Figure 3] Figure 3 is a block diagram illustrating the schematic electrical configuration of the controller and remote controller that make up the water heater shown in Figures 1 and 2. [Figure 4] Figure 4 is a graph showing the relationship between the opening degree of the hot water gas proportional control valve and the flame current. [Figure 5] Figure 5 is a flowchart showing the processing of the control unit. [Figure 6]Figure 6 is a flowchart showing the flame current fluctuation detection process. [Figure 7] Figure 7 is a flowchart showing the flame current threshold correction process. [Figure 8] Figure 8 is a flowchart showing the anomaly detection process. [Modes for carrying out the invention]

[0009] Each of the following [1] to [4] is an example of a combustion apparatus included in this disclosure.

[0010] [1] A burner for burning gas, A burner that burns gas, A flame rod that outputs a flame current corresponding to the degree of combustion of the burner, A detection unit that acquires a detected value indicating the magnitude of the flame current output from the flame rod, A determination unit that determines whether the detected value is below a threshold, A setting unit for setting the threshold, A storage unit that stores specific information that identifies a first relational expression that associates the amount of gas supplied to the burner with the value of the flame current and determines the degree of increase such that the value of the flame current increases as the amount of gas increases. Equipped with, The setting unit sets the threshold based on the initial value, which is the detected value acquired by the detection unit during the initial period after combustion by the burner has started, the specific information, and the amount of gas supplied to the burner, reflecting the degree of increase of the first relational expression. The threshold is increased as the amount of gas supplied to the burner increases, and the threshold is increased as the initial value increases. Combustion device.

[0011] When an abnormality is determined by determining whether a detection value indicating the magnitude of a flame current is equal to or less than a threshold, if the threshold is set to a fixed value that is too high, a normal flame current reduction state caused by a small amount of supplied gas is likely to be detected as an abnormality. Conversely, if the threshold is set to a fixed value that is too low, an abnormality is unlikely to be detected even when an abnormal state in which the flame current decreases despite a large amount of gas occurs. Regarding this point, in the combustion apparatus of [1] above, the threshold can be set to reflect the degree of increase in the first relational expression, such that the larger the amount of gas supplied to the burner is, the larger the threshold becomes, and the larger the initial value (the detection value acquired by the detection unit during an initial period after the start of combustion by the burner) is, the larger the threshold becomes. In this way, the combustion apparatus can set the threshold relatively low when the amount of gas is small, and set the threshold relatively high when the amount of gas is large, so the above problem can be easily solved. Furthermore, since the setting unit can set the threshold such that the larger the initial value is, the larger the threshold becomes, it is easy to set the threshold at a level matching the level of the detection value (initial value) actually detected in the initial period.

[0012] [2] The amount of gas to the burner is determined by a magnitude proportional to the opening degree X of a valve, the first relational expression is an expression of Y=A×X+B, where the value of Y is determined when the opening degree X of the valve is determined, in the first relational expression, the predetermined slope is A, when the initial value is Y1 and the opening degree X of the valve corresponding to the amount of gas supplied to the burner is X1, the relationship of B=Y1-A×X1 is satisfied, as a second relational expression where Yth is the threshold at the opening degree X of the valve, an expression of Yth=(A×X+B)×C is defined, C is a fixed value indicating a predetermined fixed ratio, Yth is used as the threshold always or when a predetermined condition is satisfied, The combustion apparatus according to [1].

[0013] The combustion device described in [2] above can easily implement a setting that increases the threshold as the valve opening X increases. Furthermore, with this method, the threshold can be set to increase as the initial value increases.

[0014] [3] If Yth, which is determined by the formula Yth = (A × X + B) × C when the valve opening degree X is less than the upper limit, Yth is used as the threshold, If Yth, determined by the formula Yth = (A × X + B) × C when the valve opening degree X is greater than or equal to the upper limit, the upper limit is used as the threshold. The combustion apparatus described in [2].

[0015] If the threshold is set solely by Yth = (A × X + B) × C, there is a concern that the threshold will become too large if the initial value is large and the valve opening X is also large. In the combustion device described in [3] above, if Yth, which is determined by Yth = (A × X + B) × C, exceeds the upper limit, the upper limit can be used as the threshold, thus preventing the threshold from becoming larger than the upper limit.

[0016] <First Embodiment> The following description relates to the first embodiment. (Basic configuration) The water heater 1, shown in Figures 1 and 2 as an example of a combustion device, is a device that at least performs the operation of supplying water heated by heat exchangers 6 and 56 to the bathtub 60, and is configured as a bath and hot water supply system that has the function of supplying hot water to the bathtub 60 and the function of heating the water in the bathtub 60 while circulating it. The water heater 1 has the appearance shown in Figure 1. The water heater 1 has the configuration shown in Figure 2 and mainly comprises a hot water supply circuit 2 and a bathtub circuit 3. As shown in Figures 1 and 2, the water heater 1 has a housing 5, a hot water supply circuit 2 including a heat exchanger 6, and a bathtub circuit 3 having piping (drop-in pipe 70) branched from the hot water supply circuit 2. As shown in Figures 1 and 2, the hot water supply circuit 2 and the bathtub circuit 3 are housed in the housing 5 of the water heater 1.

[0017] As shown in Figure 2, the hot water supply circuit 2 includes a hot water supply water channel, a gas burner 4, a heat exchanger 6, etc. The hot water supply circuit 2 functions as a circuit that heats tap water supplied from the outside and dispenses it as hot water. The bath side circuit 3 includes a bath side water channel, a gas burner 54, a heat exchanger 56, a circulation pump 62, thermistors 64, 65, etc. The bath side circuit 3 is used for circulating heating when filling the bathtub, reheating the bathwater, etc. A hot water ignition plug 35 and a hot water flame rod 36 are provided above the gas burner 4, and a bath ignition plug 37 and a bath flame rod 38 are provided above the gas burner 54.

[0018] In the hot water supply circuit 2, the pipeline consisting of the inlet pipe 12, heat transfer pipe 8a, piping 20, heat transfer pipe 7a, and outlet pipe 10 functions as the hot water supply water passage described above. The inlet pipe 12 is the passage (pipe) through which water flows in from the water inlet 16. The outlet pipe 10 is the passage (pipe) through which hot water is sent to the hot water outlet 18. The gas burner 4 functions as a hot water supply burner and burns combustion gas to generate combustion exhaust. The burner groups 4A, 4B, and 4C that make up the gas burner 4 consist of multiple burners with different numbers from each other. Of the burner groups 4A, 4B, and 4C, burner group 4A has the most gas burners, burner group 4B has the fewest gas burners, and burner group 4C has fewer gas burners than burner group 4A but more than burner group 4B. The combustion process is divided into five stages: 1st stage is the combustion of burner group 4B, which has the fewest number of burners; 2nd stage is the combustion of burner group 4C, which has the next largest number of burners; 3rd stage is the simultaneous combustion of burner groups 4B and 4C, which have the next largest number of burners; 4th stage is the combustion of burner group 4A, which also has the next largest number of burners; and 5th stage is the combustion of all burner groups 4A to 4C, which have the largest number of burners. The controller 22 performs switching control, switching the combustion stage (also called combustion stage or combustion phase) of the gas burner 4 in five stages according to the required gas supply amount (input request amount).

[0019] The gas flow path 40 that supplies gas to the gas burner 4 is equipped with a gas source solenoid valve 42, a hot water gas proportional control valve 44, and multiple hot water switching solenoid valves 46, starting from the upstream side. The gas flow path 40 includes a main flow path 40A whose upstream end is connected to the gas supply source, and multiple branch flow paths 40B connected to the downstream end of the main flow path 40A and branching off from the main flow path 40A toward each gas burner 4.

[0020] The heat exchanger 6 functions as a hot water supply side heat exchanger 6. The heat exchanger 6 is the part that transfers heat generated by the gas burner 4 to the water passing through the hot water supply side water passage (a pipeline consisting of an inlet pipe 12, a heat transfer pipe 8a, a pipe 20, a heat transfer pipe 7a, and a hot water outlet pipe 10) to heat the water. The heat exchanger 6 is located in the middle of the hot water supply side water passage and transfers heat generated by combustion in the gas burner 4 to the water passing through the inside of the hot water supply side water passage. The heat exchanger 6 comprises a primary heat exchanger 7 and a secondary heat exchanger 8. The primary heat exchanger 7 is located upstream of the combustion exhaust path of the gas burner 4 within the hot water supply combustion chamber 90. The secondary heat exchanger 8 is located downstream of the combustion exhaust path within the hot water supply combustion chamber 90.

[0021] The heat exchanger 6 functions to recover sensible heat from the combustion exhaust using the primary heat exchanger 7, and then recover latent heat using the secondary heat exchanger 8. The primary heat exchanger 7 is equipped with heat transfer tubes 7a that serve as water passages within the primary heat exchanger 7, and transfers the heat of combustion contained in the combustion exhaust generated by the gas burner 4 to the water passing through the heat transfer tubes 7a, thereby exchanging heat by transferring sensible heat energy to the water. The secondary heat exchanger 8 is equipped with heat transfer tubes 8a that serve as water passages within the secondary heat exchanger 8, and transfers the heat of combustion from the combustion exhaust generated by the gas burner 4 after it has passed through the primary heat exchanger 7 to the water passing through the heat transfer tubes 8a, thereby exchanging heat by transferring latent heat energy to the water.

[0022] In the hot water supply circuit 2, an inlet pipe 12 is connected to the inlet of the secondary heat exchanger 8, supplying tap water. The inlet pipe 12 is equipped with an inlet thermistor 25 that detects the temperature of the water passing through the inlet pipe 12 (specifically, the water temperature at a location upstream of the heat exchanger 6 and downstream of the water inlet 16 within the water pipe) and a water flow sensor 34 that detects the amount of water flowing through the inlet pipe 12 (i.e., the amount of water flowing through the water pipe). The inlet thermistor 25 has the function of detecting the temperature of water introduced from the outside. Downstream of the inlet pipe 12, the heat transfer tubes 8a of the secondary heat exchanger 8 are connected, and further downstream, a pipe 20 is connected that connects the heat transfer tubes 8a of the secondary heat exchanger 8 and the heat transfer tubes 7a of the primary heat exchanger 7. The heat transfer tubes 7a of the primary heat exchanger 7 are connected to this piping 20, and the outlet pipe 10 is connected to the outlet of the primary heat exchanger 7 to discharge the hot water heated by the primary heat exchanger 7. Of these, the hot water supply side water passage consisting of the inlet pipe 12, heat transfer tubes 8a, piping 20, heat transfer tubes 7a, and outlet pipe 10 functions as a water passage provided in the hot water supply side circuit 2. On the other hand, the bath side water passage consisting of the drop-in pipe 70 and piping 66 functions as a second water passage provided in the bath side circuit 3. The outlet pipe 10 is equipped with an inner cylinder outlet thermistor 27 provided on the primary heat exchanger 7 (heat exchanger 6) side to detect the temperature of the water that has been heat-exchanged in the primary heat exchanger 7, and an outlet thermistor 26 provided on the hot water outlet 18 side to detect the temperature of the discharged hot water after mixing with water from the bypass pipe 14.

[0023] A bypass pipe 14 is provided as a water passage that bypasses the inlet pipe 12 and the outlet pipe 10, and is configured as a water passage different from that of the heat exchanger 6. The bypass pipe 14 is equipped with a bypass valve 32 that can transition between a closed state in which the water flow through the bypass pipe 14 is blocked and an open state in which the opening degree is increased compared to the closed state.

[0024] In the inlet pipe 12, a water flow control valve 33 is provided upstream of the branching point where the bypass pipe 14 is connected. The water flow control valve 33 is equipped with a motor whose rotation angle of the drive shaft is controlled by instructions from the controller 22, and is configured to continuously change the opening of the inlet pipe 12 between a closed state and a fully open state. In this configuration, the water flow control valve 33 functions to regulate the amount of water flowing through the water pipe from the water inlet 16 to the hot water outlet 18.

[0025] The gas flow path 40 that supplies gas to the gas burner 4 is equipped with a gas source solenoid valve 42, a hot water gas proportional control valve 44, and hot water switching solenoid valves 46, 46... for each branch pipe to each gas burner 4, from the upstream side. Below the hot water combustion chamber 90, a hot water fan 48 is provided to supply combustion air to each gas burner 4 and gas burner 54. The hot water fan 48 comprises a blade section with multiple blades, a fan motor 49 that rotates this blade section, and a rotation speed sensor 50 that detects the rotation speed of the fan 48. The fan motor 49 has a drive shaft fixed to the blade section, and the controller 22 controls the rotation of the drive shaft of the fan 48. A switching solenoid valve 53 is provided in the branch pipe from the gas pipe connected to the gas burner 54. The hot water gas proportional control valve 44 and the hot water switching solenoid valve 46 function to adjust the amount of gas supplied to the gas burner 4. A switching solenoid valve 53 is provided in the bath-side branch passage 40C, which is connected to the gas passage 40 connected to the gas burner 54 (bath-side burner).

[0026] In the bath-side circuit 3, the piping 66 includes a pipe 67 for guiding water from the bathtub 60 to the heat exchanger 56, a pipe 68 for guiding water from the heat exchanger 56 to the bathtub 60, and an intermediate pipe 69 connected to pipes 67 and 68 and passing through the heat exchanger 56. One end of the piping 66 is connected to the inside of the bathtub 60, and the other end is configured as a path for passing water that has come out of the bathtub 60 back into the bathtub 60. For example, during reheating or heating operations, the piping 66 guides water drawn from the bathtub 60 to the heat exchanger 56 via pipe 67, and the water that has passed through the heat exchanger 56 is circulated back to the bathtub 60 via pipe 68. The gas burner 54 functions as a bath-side burner, burning combustion gas to generate combustion exhaust. The heat exchanger 56 transfers the heat generated by the gas burner 54 to the water passing through a part of the bath-side water pipe (specifically, the water passing through pipe 66). The heat exchanger 56 comprises a primary heat exchanger 57 and a secondary heat exchanger 58, and functions to transfer heat generated by the gas burner 54 to water passing through the piping 66.

[0027] The piping 67 is located between the bathtub 60 and the secondary heat exchanger 58, and is equipped with a circulation pump 62 and a thermistor 64 (bath thermistor) that detects the temperature of the water passing through the piping 67. The thermistor 64 functions to detect the temperature of the water discharged from the bathtub 60 (i.e., the temperature of the water inside the bathtub 60). The circulation pump 62 is a device that circulates the water in the piping 66, and functions to draw water from the bathtub 60 side and discharge the drawn water toward the heat exchanger 56 side.

[0028] The piping 68 is positioned between the primary heat exchanger 57 and the bathtub 60. A drop-in pipe 70, branched from the hot water outlet pipe 10, is connected to the piping 68, and hot water supplied from the drop-in pipe 70 flows into the piping 68. The drop-in pipe 70 is equipped with a hot water solenoid valve 72 and a drop-in water volume sensor 74. By opening the hot water solenoid valve 72 provided on the drop-in pipe 70, it is possible to supply hot water heated in the hot water supply circuit 2 to the bathtub 60. The drop-in water volume sensor 74 has the function of detecting the amount of water supplied to the bathtub 60 via the drop-in pipe 70.

[0029] The drop-in pipe 70 is the path through which hot water flows from the hot water supply side water passage of the hot water supply side circuit 2 to the piping 66 (circulation path) of the bath side circuit 3. The drop-in pipe 70 branches off from the outlet pipe 10 and connects to piping 67, and functions to guide the water heated by the heat exchanger 6 through the hot water supply side water passage to the bathtub 60.

[0030] As shown in Figure 2, the water heater 1 is equipped with a controller 22. As shown in Figure 3, the controller 22 comprises a control unit 22A configured as a known microcomputer, a storage unit 22B configured as a known semiconductor memory, and a communication unit 22C configured as an interface for communication with the outside. The controller 22 is configured to acquire signals from various sensors provided in the hot water supply circuit 2 and the bath side circuit 3, and can control various actuators provided in the hot water supply circuit 2 and the bath side circuit 3. The controller 22 controls the operation of the gas burners 4, 54 and at least a part of the supply unit. The controller 22 is connected to the power receiving unit 23. When an external power supply is connected to the power receiving unit 23 and power can be supplied from the outside, a power signal is input to the control unit 22A. The controller 22 is also configured to communicate with an external device provided outside the water heater 1 via a communication network such as the Internet, and is configured to acquire information from the external device.

[0031] As shown in Figure 3, the multiple remote controllers 80 (hereinafter referred to as remote controls 80) are arranged in a configuration that allows them to communicate with the controller 22. In the example in Figure 3, the multiple remote controls 80 include a first remote controller 81 (hereinafter referred to as the first remote control 81) installed in the bathroom and a second remote controller 82 (hereinafter referred to as the second remote control 82) installed in a location other than the bathroom (for example, the kitchen).

[0032] As shown in Figure 3, the first remote control 81 comprises a control unit 81A configured as a known microcomputer, a display unit 81B configured as a liquid crystal display device, an operation unit 81C provided with a plurality of known switches such as push buttons, an audio output unit 81D consisting of a speaker for outputting sound, and a communication unit 81E for communicating with the controller 22 and the second remote control 82. The operation unit 81C is composed of a plurality of operation units, including an operation switch. By pressing the operation switch, it is possible to switch between an operational state and an operational stop state for the hot water supply operation. The other operation units are used for input operations to instruct the filling of the bathtub 60 with hot water (input operations to instruct automatic filling and input operations to instruct energy-saving filling), input operations to reserve filling, and input operations to switch the on / off state of additional functions.

[0033] The second remote control 82 is similar, comprising a control unit 82A configured as a known microcomputer, a display unit 82B configured as a liquid crystal display device, an operation unit 82C provided with a plurality of known switches such as push buttons, an audio output unit 82D consisting of a speaker for outputting sound, and a communication unit 82E for transmitting signals generated by the second remote control 82 to the controller 22. The second remote control 82 has the same configuration as the first remote control 81, or a simplified configuration, and can be set in the same way as the first remote control 81. The on / off states of both remote controls 80 are linked. Settings set on one remote control 80 are reflected in the other.

[0034] (Configuration for detecting anomalies) The water heater 1 is equipped with a configuration that can detect abnormalities such as incomplete combustion. Specifically, the water heater 1 includes a hot water flame rod 36 and a detection unit 30. The control unit 22A includes a setting unit 29 and a determination unit 28. The hot water flame rod 36 outputs a flame current corresponding to the degree of combustion of the gas burner 4. Specifically, when a flame is present near the hot water flame rod 36, the flame causes a current (flame current) to flow through the hot water flame rod 36, and the value of this current flowing through the hot water flame rod 36 is treated as the output value (detection value) of the hot water flame rod 36. Therefore, the greater the influence of the flame on the hot water flame rod 36, the larger the current flowing through the hot water flame rod 36, and the larger the output value (detection value). The detection unit 30 is an analog circuit mounted on a circuit board in the controller 22. The detection upper limit for flame current in the detection unit 30 can be selected from various values ​​depending on the resolution of the analog circuit, but in this embodiment, for cost reasons, the detection upper limit for flame current in the detection unit 30 is set to 40 [μA]. The flame current output from the hot water flame rod 36 is input to the detection unit 30. If a flame current exceeding 40 [μA] is input to the detection unit 30, it exceeds the detection upper limit, and the detection unit 30 corrects (converts) it to a detected value of 40 [μA]. The detected value in the detection unit 30 is converted into a digital signal and input to the control unit 22A in the controller 22. The determination unit 28 determines whether the detected value of the flame current is below a threshold when an abnormality is detected. The setting unit 29 sets the value calculated using the relational formula described later as the flame current threshold used when detecting an abnormality.

[0035] Figure 5 is a flowchart showing the processing of the control unit 22A. Below, the processing of the control unit 22A in response to the flame current output from the hot water flame rod 36 will be explained, and the processing of the control unit 22A in response to the flame current output from the bath flame rod 38 will be the same as on the hot water flame rod 36 side, so the explanation will be omitted.

[0036] In step S11, the control unit 22A detects whether water supply has started based on a signal from the water volume sensor 34. If water supply is not detected by the signal from the water volume sensor 34 (No in step S11), the process in step S11 is repeated. If the control unit detects that water supply has started based on a signal from the water volume sensor 34 (Yes in step S11), the process proceeds to step S12. In step S12, it is determined whether the system is in an ignition-ready state. An ignition-ready state can be defined as a state in which, for example, the voltage of the power supply (battery, etc.) is above a predetermined level and the gas type connector is properly connected. If it is determined that the system is not in an ignition-ready state (No in step S12), the process in steps S11 and S12 is repeated. On the other hand, if it is determined that the system is in an ignition-ready state (Yes in step S12), the process proceeds to step 13 and the ignition process begins.

[0037] In the ignition process, the control unit 22A activates an igniter (not shown) to discharge from the hot water ignition plug 35, opens the gas source solenoid valve 42 and multiple hot water switching solenoid valves 46, ignites the gas burner 4, and starts counting on the timer T1 in step S14. Next, in step S15, it is determined whether a predetermined time TA, for which the ignition operation is expected to stabilize, has elapsed. In this embodiment, the predetermined time TA is 30 seconds, but it is not limited to this and any time can be set. If the timer T1 count has not elapsed for the predetermined time TA (No in step S15), the process in step S15 is repeated. If the timer T1 count has elapsed for the predetermined time TA (Yes in step S15), the process proceeds to step S16. In step S16, flame current fluctuation detection processing is performed.

[0038] Figure 6 is a flowchart showing the flame current fluctuation detection process. In the flame current fluctuation detection process, step S21 starts counting on timer T2, and while storing the detected flame current at minute time intervals in the storage unit 22B, the process proceeds to step S22 to determine whether a predetermined time TB has elapsed. Since the transient period at the beginning of ignition may be unstable, a waiting period of a predetermined time TB is performed to allow for stabilization. In this embodiment, the predetermined time TB is set to 10 seconds, but it is not limited to this and any time can be set. If the timer T2 count has not elapsed the predetermined time TB (if No in step S22), the process in step S22 is repeated. If the timer T2 count has elapsed the predetermined time TB (if Yes in step S22), the process proceeds to step S23. Furthermore, if any of the following conditions occur before the predetermined time TB has elapsed (within 10 seconds): flame current fluctuates by 10% or more, combustion stage switching occurs, or the water heater capacity falls below the predetermined level (for a No. 10 unit, since the water heater capacity is 15,000 kcal / h or more, the thermal efficiency is considered to be less than 15,500 kcal / h), abnormality detection will be interrupted and the system can be put into a stabilization waiting state.

[0039] Figure 4 is a graph showing the relationship between the opening degree of the hot water gas proportional control valve 44 and the flame current. In step S23, the control unit 22A calculates the average value of the TB time (10 seconds) from multiple detected flame current values ​​stored in the memory unit 22B, and stores the calculated average value in the memory unit 22B as the initial value of the flame current Y1 (40 [μA] in Figure 4). In step S24, the opening degree X1 of the hot water gas proportional control valve (hereinafter referred to as "proportional valve opening degree"; 50% in Figure 4) when the initial value Y1 is set is stored, and the process proceeds to step S25. In step S25, the first relational expression F1 of the flame current is calculated. Specifically, the memory unit 22B stores identification information for identifying the first relational expression F1, and the first relational expression F1 is determined using the initial value of the flame current, the identification information, and the proportional valve opening degree, and stored in the memory unit 22B.

[0040] The identifying information for identifying the first relational equation F1 can be, for example, the slope A (slope of F1) when the first relational equation F1 is a linear equation (Y = A × X + B), as shown in Figure 4. This slope A is a slope that satisfies the specifications of the water heater 1 and is stored in the memory unit 22B beforehand. The slope of the linear equation differs depending on the type of gas, but when the specifications are determined, for example, an average slope is set. P1 in Figure 4 is plotted using the initial value of the flame current Y1 (40 [μA] in Figure 4) and the proportional valve opening X1 (50% in Figure 4) when the initial value Y1 is set. In the linear equation (Y=A×X+B), by using the pre-stored slope A, substituting the initial flame current Y1 for Y, and substituting the proportional valve opening X1 for X, the intercept B of the linear equation can be found using the equation B=Y1-A×X1. Thus, both A and B are identified as fixed values, and the first relational equation F1, expressed as Y=A×X+B, is obtained.

[0041] From this relational equation F1, the flame current when the proportional valve opening is 0% (flame current at position P2) and the flame current when the proportional valve opening is 100% (flame current at position P3) are calculated and stored in the memory unit 22B. The flame current when the proportional valve opening is 0% and the flame current when the proportional valve opening is 100% are used to calculate the second relational equation F2, which will be described later. Note that a proportional valve opening of 0% is considered to be the fully closed state, and a proportional valve opening of 100% is considered to be the fully open state.

[0042] Next, the process proceeds to step S26, and it is determined whether or not there is a region where the flame current exceeds the detection upper limit (40 [μA]) with respect to the entire region (0% to 100%) of the proportional valve opening in the first relational expression F1. If there is no region where the flame current exceeds the detection upper limit (40 [μA]) (No in step S26), the flame current fluctuation detection process is ended, and the process proceeds to the flame current threshold correction process of step S17. As shown in relational expression F0 of FIG. 4, if there is a region where the flame current exceeds the detection upper limit (40 [μA]) (Yes in step S26), the process proceeds to step S27, the first relational expression F1 is corrected such that the region of the proportional valve opening that exceeds the detection upper limit (40 [μA]) in the first relational expression F1 becomes the detection upper limit (40 [μA]), specification information for specifying the first relational expression F1 is stored in the storage unit 22B, the flame current fluctuation detection process is ended, and the process proceeds to the flame current threshold correction process of step S17. By the correction of the first relational expression F1, the opening OD of the hot water supply gas electromagnetic proportional valve satisfies the linear expression (Y=A×X+B) in the range of 0≦OD≦50[%], and becomes a constant (40[μA]) in the range of 50<OD≦100[%]. Note that when the initial value of the flame current is less than the detection upper limit (less than 40 [μA]), a value larger than the initial value serves as the upper limit of the flame current.

[0043] Figure 7 is a flowchart showing the flame current threshold correction process. In the flame current threshold correction process, in step S31, a second relational expression F2 is obtained by applying a predetermined percentage C (e.g., 70%) to the first relational expression. There are various ways to obtain the second relational expression, but for example, points R1 to R3 are plotted at a predetermined percentage (e.g., 70%) to the flame current when the proportional valve opening is 50% (flame current at position P1), when the proportional valve opening is 0% (flame current at position P2), and when the proportional valve opening is 100% (flame current at position P3), which are stored in the memory unit 22B. The second relational expression F2 is obtained as a threshold passing through points R1 to R3 and stored in the memory unit 22B, and the process proceeds to step S32. In step S32, the flame current threshold according to the second relational expression F2 at the current proportional valve opening is obtained using the second relational expression F2, the obtained threshold is set in the setting unit 29, and the process proceeds to the abnormality detection process in step S18. In Figure 4, the flame current threshold is set to 28 [μA] when the proportional valve opening is 50% and 100%.

[0044] Thus, the second relation above is a relation that determines the threshold, and if the threshold is Yth, it is determined by the formula Yth = (A × X + B) × C. However, when the valve opening is X, if Yth determined by the formula Yth = (A × X + B) × C is less than the upper limit (28 [μA] in the above example), Yth is used as the threshold, and if it is greater than or equal to the upper limit, the upper limit (28 [μA] in the above example) is used as the threshold.

[0045] Figure 8 is a flowchart showing the anomaly detection process. In the abnormality detection process, the timer T3 countdown starts in step S41 and the process proceeds to step S42. In step S42, it is determined whether the detected flame current value detected by the detection unit 30 is below a threshold. If the detected flame current value detected by the detection unit 30 is not below the threshold (No in step S42), it is determined that combustion is normal and no abnormalities such as incomplete combustion have occurred, and the abnormality detection process is terminated. If the detected flame current value detected by the detection unit 30 is below the threshold (Yes in step S42), there is a possibility that an abnormality has occurred, so in step S43, it is determined whether the timer T3 time is greater than or equal to a predetermined time TC. The predetermined time TC is set so that an abnormality is not detected if the flame current drops instantaneously even though no abnormality has occurred (cases where the flame current drops instantaneously are excluded). In this embodiment, the predetermined time TC is set to 15 seconds, but it is not limited to this, and any time can be set. If the timer T3 time is not equal to or greater than the predetermined time TC (if No in step S43), the process returns to step S42 and steps S42 and S43 are repeated. If the timer T3 time is equal to or greater than the predetermined time TC (if Yes in step S43), an abnormality is detected. When an abnormality is detected, the control unit 22A stops the gas combustion operation by the gas burner 4 and notifies the user that an abnormality such as incomplete combustion has occurred on a display unit that the user can recognize, and terminates the abnormality detection process.

[0046] The following explanation concerns an example of the effects of this configuration. A water heater 1, an example of a combustion device, comprises a gas burner 4 for burning gas, a hot water flame rod 36 that outputs a flame current corresponding to the degree of combustion of the gas burner 4, a detection unit 30 that acquires a detection value indicating the magnitude of the flame current output from the hot water flame rod 36, a determination unit 28 that determines whether the detection value is below a threshold, a setting unit 29 that sets a threshold, and a storage unit 22B that stores specific information that identifies a first relational expression F1 which associates the amount of gas supplied to the gas burner 4 with the value of the flame current and defines the degree of increase such that the flame current value increases as the amount of gas increases. The setting unit 29 sets a threshold based on an initial value which is a detection value acquired by the detection unit 30 during the initial period after combustion by the gas burner 4 has started (for example, 30 seconds + 10 seconds), specific information, and the amount of gas supplied to the gas burner 4, so that the threshold increases as the amount of gas supplied to the gas burner 4 increases, and the threshold increases as the initial value increases, reflecting the degree of increase of the first relational expression F1.

[0047] When determining an abnormality by determining whether the detected value indicating the magnitude of the flame current is below a threshold, setting the threshold to a fixed value that is too high makes it easier to detect an abnormality even in the case of a normal decrease in flame current due to a small amount of supplied gas. Conversely, setting the threshold to a fixed value that is too low makes it difficult to detect an abnormality even in the case of an abnormal condition where the flame current decreases despite a large amount of gas. In this regard, the water heater 1 described above can be configured to reflect the degree of increase of the first relational expression F1, so that the threshold becomes larger the larger the amount of gas supplied to the gas burner 4, and also so that the threshold becomes larger the larger the initial value (the detected value acquired by the detection unit 30 in the initial period after combustion by the gas burner 4 has started). In this way, the water heater 1 can set the threshold relatively low when the amount of gas is small, and relatively high when the amount of gas is large, thus easily resolving the above problem. Furthermore, since the setting unit 29 can set the threshold so that the threshold becomes larger the larger the initial value, it is easy to set the threshold at a level that matches the level of the detected value (initial value) actually detected in the initial period.

[0048] Furthermore, since the threshold is determined based on a second relational expression F2 obtained by multiplying the flame current value obtained by the first relational expression F1 by a predetermined ratio, the calculation process for the threshold can be simplified.

[0049] Furthermore, the second relational equation F2 has an upper limit set for the flame current. The detection current of the flame current detected by the detection unit 30 has an upper limit. Depending on the second relational equation F2, it is conceivable that the flame current value corresponding to the amount of gas may exceed the upper limit of the detectable current. In such cases, if the threshold set exceeds the upper limit of the detectable current, there is a problem in that an abnormality is detected even though the actual flame current value is a normal value greater than the threshold. In the above configuration, since the second relational equation F2 has an upper limit set for the flame current, highly accurate abnormality detection can be performed by setting an upper limit for the flame current according to the performance of the detection unit 30.

[0050] <Other Embodiments> This disclosure is not limited to the embodiments described above and in the drawings. For example, any combination of the features of the embodiments described above or below is possible as long as it does not contradict each other. Furthermore, any feature of the embodiments described above or below may be omitted unless explicitly stated as essential. Moreover, the embodiments described above may be modified as follows.

[0051] The combustion device is not limited to water heater 1. For example, the combustion device may be applied to an instantaneous water heater or a water heater / heating system.

[0052] It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is not limited to the embodiments disclosed herein, and is intended to include all modifications within the scope set forth in the claims or equivalents thereof. [Explanation of symbols]

[0053] 1: Water heater (combustion device) 4: Gas burner (burner) 22: Controller 22A: Control Unit 22B: Storage section 22C: Communication Department 28: Judgment section 29: Settings Section 30: Detection unit 34: Water volume sensor 35: Hot water ignition plug 36: Hot water supply frame rod 42: Gas source solenoid valve 44: Proportional control valve for hot water gas 46: Hot water supply switching solenoid valve

Claims

1. A burner that burns gas, A flame rod that outputs a flame current corresponding to the degree of combustion of the burner, A detection unit that acquires a detected value indicating the magnitude of the flame current output from the flame rod, A determination unit that determines whether the detected value is below a threshold, A setting unit for setting the threshold, A storage unit that stores specific information that identifies a first relational expression that associates the amount of gas supplied to the burner with the value of the flame current and determines the degree of increase such that the flame current value increases as the amount of gas increases. Equipped with, The setting unit sets the threshold based on the initial value, which is the detected value acquired by the detection unit during the initial period after combustion by the burner has started, the specific information, and the amount of gas supplied to the burner, reflecting the degree of increase of the first relational expression. The threshold is increased as the amount of gas supplied to the burner increases, and the threshold is increased as the initial value increases. Combustion device.

2. The amount of gas supplied to the burner is determined to be proportional to the valve opening X. The first relation is the equation Y = A × X + B, where the value of Y is determined by the opening degree X of the valve. In the first relational equation above, the predetermined slope is A, When the initial value is Y1, and the valve opening X corresponding to the amount of gas supplied to the burner is X1, then the relationship B = Y1 - A × X1 is satisfied. A second relational expression is defined as Yth = (A × X + B) × C, where Yth is the threshold value when the valve opening degree X. The aforementioned C is a fixed value representing a predetermined percentage. Yth is used as the threshold always or when predetermined conditions are met. The combustion apparatus according to claim 1.

3. If Yth, determined by the formula Yth = (A × X + B) × C when the valve opening degree X is less than the upper limit, Yth is used as the threshold value. If Yth, determined by the formula Yth = (A × X + B) × C when the valve opening degree X is greater than or equal to the upper limit, the upper limit is used as the threshold. The combustion apparatus according to claim 2.

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