Combustion device

Abstract

A combustion device is provided. A controller (8) accumulates the combustion time of a burner and stores the combustion accumulation time (Ta). The controller (8) sets a first lower limit value (A) and a second lower limit value (B) higher than the first lower limit value (A) as lower limit values of the air excess ratio of the mixture gas at the time of the re-ignition operation of an ignition mechanism (32) when the combustion accumulation time (Ta) is less than a prescribed set time and when the combustion accumulation time (Ta) is equal to or greater than the set time, respectively, which are lower than the initial value of the air excess ratio.

Description

Technical Field

[0001] This invention relates to a combustion apparatus as described below, comprising: a burner disposed in a combustion chamber for burning a mixture of combustion air and fuel gas; a fan for supplying combustion air to the burner; a gas supply line for supplying fuel gas to the burner; a proportional valve disposed in the gas supply line; an ignition mechanism for igniting the burner; an ignition monitoring mechanism for monitoring the ignition of the burner; and a controller for controlling the fan, the proportional valve, and the ignition mechanism. Background Technology

[0002] Conventionally, combustion devices of this type have been configured such that: in the controller, an air excess rate suitable for burner ignition is preset as an initial value for the gas mixture; when a combustion instruction to ignite the gas mixture in the burner is issued, the controller adjusts the amount of combustion air and fuel gas to bring the air excess rate of the gas mixture to the initial value; if the burner fails to ignite even when the ignition mechanism performs an ignition action, the air excess rate of the gas mixture is gradually reduced from the initial value, while the ignition mechanism repeatedly performs a re-ignition action (see, for example, Patent Document 1).

[0003] For example, in the case of a newly installed combustion device, if air remains in the gas supply line and is not fully replaced by fuel gas, the excess air ratio of the gas mixture supplied to the burner is higher than the initial value. This results in a situation where the burner cannot ignite even when the ignition mechanism performs an ignition operation. To address this issue, according to the combustion device disclosed in Patent Document 1, the following countermeasures can be taken: the controller reduces the excess air ratio of the gas mixture in stages from the initial value, while the ignition mechanism repeatedly performs re-ignition operations.

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 6-221547 Summary of the Invention

[0006] However, even if the actual excess air ratio of the gas mixture supplied to the burner is the initial value, there are occasional situations where the burner fails to ignite due to unforeseen factors such as ignition failure of the ignition electrode. In such cases, the controller of the combustion device disclosed in Patent Document 1 incorrectly judges that the excess air ratio of the gas mixture is higher than the initial value, and thus reduces the excess air ratio. Consequently, the actual excess air ratio of the gas mixture supplied to the burner is excessively reduced. With such an excessively reduced excess air ratio, if the ignition mechanism performs a re-ignition operation to ignite the burner, it may cause adverse conditions such as explosion or poor combustion resulting in carbon monoxide gas.

[0007] In view of the above-mentioned problems, the present invention aims to provide a combustion device that can easily achieve ignition of the burner by appropriately adjusting the excess air ratio of the mixed gas actually supplied to the burner, and can suppress adverse conditions such as explosion or poor combustion during the re-ignition action of the ignition mechanism.

[0008] To address the aforementioned problems, the combustion apparatus of the present invention comprises: a burner disposed in a combustion chamber and for burning a mixture of combustion air and fuel gas; a fan for supplying combustion air to the burner; a fuel gas supply line for supplying fuel gas to the burner; a proportional valve disposed in the fuel gas supply line; an ignition mechanism for igniting the burner; an ignition monitoring mechanism for monitoring the ignition of the burner; and a controller for controlling the fan, the proportional valve, and the ignition mechanism, wherein the controller is configured to pre-set an air excess ratio suitable for burner ignition as an initial value, and the controller is configured to adjust the amount of combustion air and the amount of fuel gas when instructed to burn in the burner. The controller is configured to reduce the excess air ratio of the gas mixture to an initial value. Even if the ignition mechanism fails to ignite the burner, the excess air ratio of the gas mixture is reduced in stages from the initial value. Simultaneously, the ignition mechanism repeatedly performs re-ignition actions. The controller accumulates and stores the combustion time of the burner. It sets a first lower limit and a second lower limit as the lower limits for the reduction of the excess air ratio of the gas mixture from the initial value when the ignition mechanism performs re-ignition actions. The first lower limit is defined as the value when the accumulated combustion time is less than a predetermined set time, and the second lower limit is defined as the value when the accumulated combustion time is greater than the predetermined set time and is higher than the first lower limit.

[0009] According to the present invention, if the cumulative combustion time is less than a predetermined set time, it is presumed that the gas mixture with an actual excess air ratio higher than the initial value is supplied to the burner due to residual air in the gas supply circuit, thus preventing the burner from igniting. In this case, the controller reduces the excess air ratio of the gas mixture in stages from the initial value based on a first lower limit, repeatedly executing the re-ignition operation of the ignition mechanism. Therefore, as in the past, ignition of the burner is easily achieved. Furthermore, if the cumulative combustion time is greater than or equal to a predetermined set time, it is presumed that the gas supply circuit has been replaced by the gas mixture. In this case, the controller reduces the excess air ratio of the gas mixture in stages from the initial value based on a second lower limit, repeatedly executing the re-ignition operation of the ignition mechanism. Therefore, it is not necessary to reduce the excess air ratio of the gas mixture to the required level; during the re-ignition operation of the ignition mechanism, adverse conditions such as explosions or poor combustion leading to carbon monoxide gas can be suppressed.

[0010] Furthermore, the excess air ratio of the gas mixture can be broadly categorized into two types: an initial value suitable for burner ignition, and a value that decreases during re-ignition. The former is a pre-set value in the controller, estimated based on factors such as the type of fuel gas, burner combustion characteristics, and fan air supply capacity. The latter, while potentially using measured values, can also be an estimated value similar to the initial value. The combustion air supplied to the burner is correlated with the fan speed; additionally, it is well known that the combustion gas quantity is correlated with the proportional valve current. Therefore, the excess air ratio of the gas mixture decreasing during re-ignition does not necessarily need to be a measured value; it can be estimated based on the fan speed and proportional valve current. Thus, the aforementioned two types of excess air ratios can be replaced by estimated values.

[0011] In this invention, the controller is preferably configured to progressively reduce the excess air ratio of the gas mixture during re-ignition by progressively increasing the amount of fuel gas supplied to the burner, starting from the initial value. Alternatively, this progressive reduction of the excess air ratio during re-ignition can also be achieved by decreasing the amount of combustion air. While the specific methods for increasing the amount of fuel gas or decreasing the amount of combustion air may vary in complexity depending on the controller's operation, five possible modes can be considered.

[0012] • Mode 1

[0013] The amount of air used for combustion is kept constant by a specified amount, while the amount of fuel gas is increased.

[0014] Mode 2

[0015] Increasing the amount of air used for combustion, while simultaneously increasing the amount of fuel gas, results in a decrease in the excess air ratio of the gas mixture.

[0016] Mode 3

[0017] Reduce the amount of air used for combustion while increasing the amount of fuel gas.

[0018] • Mode 4

[0019] The amount of fuel gas is kept constant by a specified amount, and the amount of air used for combustion is reduced.

[0020] Mode 5

[0021] Reducing the amount of fuel gas consumed also reduces the amount of air used for combustion, resulting in a lower excess air ratio in the gas mixture.

[0022] By progressively increasing the amount of fuel gas supplied to the burner, the excess air ratio of the mixture during reignition is gradually reduced from its initial value. This aligns with modes 1, 2, and 3. However, compared to modes 4 and 5, this method increases the amount of fuel gas flowing towards the burner in the fuel supply path. Consequently, the air remaining in the fuel supply path is replaced by fuel gas earlier, leading to earlier burner ignition.

[0023] Furthermore, in this invention, it is preferable that the controller is configured to: count the number of repetitions of the re-ignition action of the ignition mechanism; if the burner fails to ignite even after a predetermined number of repetitions, an ignition error is determined, the combustion instruction is canceled, and an alarm is issued regarding the ignition error; the controller stores the excess air ratio of the gas mixture at the time of the re-ignition action of the ignition mechanism performed shortly before the ignition error is determined; and when combustion is re-instructed after the ignition error determination, the cancellation of the combustion instruction, and the ignition error alarm is issued, if the elapsed time from the time of the ignition error determination or the time of the ignition error alarm being lifted to the time of the re-instruction of combustion is within a predetermined elapsed time, the controller adjusts the excess air ratio of the gas mixture at the time of the ignition action of the ignition mechanism to be below or equal to the stored excess air ratio. Therefore, if the elapsed time from the determination of an ignition error or the clearing of the ignition error alarm to the re-indication of combustion is within a predetermined elapsed time, it is presumed that the initial combustion indication and the re-indication of combustion are issued consecutively. Thus, the excess air ratio of the gas mixture at the time of the re-indication of combustion can be lower than the initial value. Therefore, the excess air ratio of the gas mixture can be gradually reduced towards the first or second lower limit value as early as possible, thereby facilitating burner ignition. Furthermore, if the excess air ratio of the gas mixture at the time of the re-indication of combustion is lower than the excess air ratio of the gas mixture stored at the time of the re-ignition action of the ignition mechanism performed shortly before the ignition error was determined, the reduction of the excess air ratio of the gas mixture can be further promoted, thus further facilitating burner ignition. For example, one can imagine the following situation: if the predetermined number of re-ignition actions of the ignition mechanism, set as the number of repetitions, does not reach the first or second lower limit value, and the number of repetitions of the ignition mechanism's re-ignition actions reaches the predetermined number, the controller determines that an ignition error has occurred. In this case, adjusting the excess air ratio of the mixture during the re-indication of combustion as described above will help the burner ignite earlier.

[0024] Furthermore, the controller preferably includes a combustion accumulation time clearing mechanism to clear the stored combustion accumulation time. Here, after a predetermined combustion accumulation time has elapsed since the combustion device was installed, situations may occur where, due to refilling of the gas cylinder or renewal of the gas supply line, air may remain in the gas supply line, resulting in an excess air ratio in the gas mixture actually supplied to the burner exceeding the initial value. In such cases, the combustion accumulation time clearing mechanism can clear the combustion accumulation time stored in the controller. As a result, the lower limit of the excess air ratio of the gas mixture, which decreases in stages from the initial value when the ignition mechanism performs a re-ignition operation, is updated from the second lower limit value back to the first lower limit value. Therefore, similar to the case of a new combustion device installation, burner ignition is easily achieved. Attached Figure Description

[0025] Figure 1 This diagram shows a heat source for hot water supply, which is one embodiment of the combustion apparatus of the present invention.

[0026] Figure 2 express Figure 1 The flowchart shown is a first mode of control performed by the controller of the hot water supply heat source machine.

[0027] Figure 3 A flowchart illustrating a second mode of control performed by the controller included in the combustion apparatus of the present invention.

[0028] Explanation of symbols in attached drawings

[0029] 1…combustion device; 2a…combustion chamber; 3…burner; 32…igniter (ignition mechanism); 33…flame rod (ignition monitoring mechanism); 5…fan; 7…gas supply line; 72…proportional valve; 8…controller; 81…combustion accumulation time clearing mechanism; Ta…combustion accumulation time; A…first lower limit; B…second lower limit; Te…the elapsed time from the time of ignition error judgment or the time of ignition error alarm notification clearance to the time of combustion re-indication. Detailed Implementation

[0030] Reference Figure 1This section describes the general outline of a hot water supply heat source unit 1a, which is an embodiment of the combustion device 1 of the present invention. The hot water supply heat source unit 1a includes a combustion chamber 2a surrounded by a combustion housing 2. A burner 3 is disposed at the lower part of the combustion chamber 2a. The burner 3 has a first section 31 consisting of five unit burners 3a arranged side-by-side, and a second section 32 consisting of ten unit burners 3a arranged side-by-side. Furthermore, an ignition electrode 31 facing the first section 31 of the burner 3 is provided in the combustion chamber 2a, and an igniter 32, serving as an ignition mechanism, is also provided. This igniter 32 is a high-voltage external source that applies a high voltage to the ignition electrode 31. The igniter 32 performs an ignition operation by being energized, and the first section 31 is ignited by a spark generated by the ignition electrode 31. Additionally, a flame rod 33, serving as a fire detection mechanism for monitoring the ignition of the burner 3, is provided in the combustion chamber 2a.

[0031] A heat exchanger 4 for supplying hot water to the object being heated is disposed at the upper part of the combustion chamber 2a. Additionally, a fan 5 for supplying combustion air to the burner 3 is connected to the lower surface of the combustion shell 2. The combustion air supplied by the fan 5 includes primary air directly supplied to the unit burner 3a and secondary air supplied to the vicinity of the flame opening of the unit burner 3a from the lower part of the combustion chamber 2a. The combustion gases from the burner 3 heat the water from the upstream water supply pipe 4a of the heat exchanger 4, and the heated water, having reached a predetermined set temperature, is discharged from the downstream hot water discharge pipe 4b of the heat exchanger 4. The combustion gases, after passing through the heat exchanger 4, are then discharged to the outside of the combustion chamber 2a through the exhaust passage 6 connected to the upper surface of the combustion shell 2.

[0032] The gas supply path 7, which supplies fuel gas to the burner 3, includes a main valve 71, which is an electromagnetically operated valve, and a proportional valve 72 located downstream of the main valve 71. Furthermore, the portion of the gas supply path 7 downstream of the proportional valve 72 is divided into a first branch path 7a connected to the first part 31 of the burner 3, and a second branch path 7b connected to the second part 32 of the burner 3. The first branch path 7a and the second branch path 7b are respectively equipped with a first capacity switching valve 73a and a second capacity switching valve 73b, both electromagnetically operated. By opening and closing the first capacity switching valve 73a and the second capacity switching valve 73b, fuel gas is supplied to either the first part 31 of the burner 3, or both the first part 31 and the second part 32. Thus, the combustion capacity of the burner 3 can be switched between two stages. Additionally, when the igniter 32 performs ignition, a mixture of fuel gas and combustion air is supplied to the burner 3.

[0033] In addition, the hot water supply heat source unit 1a is equipped with a controller 8, which controls the fan 5, main valve 71, proportional valve 72, first capacity switching valve 73a, second capacity switching valve 73b, and igniter 32. The controller 8 is composed of a microprocessor equipped with a CPU, ROM, RAM, A / D converter, interface, etc. The flame rod 33 is connected to the controller 8.

[0034] Reference Figure 2 ,illustrate Figure 1 The controller 8 shown is performing the first mode of control. Furthermore, the term "air excess ratio of the mixture" refers to the actual amount of combustion air supplied relative to the amount of air in the mixture. Figure 1 The excess air ratio of the mixture is the theoretical amount of combustion air required for the combustion of fuel gas by the burner 3 shown. While the excess air ratio of this mixture can be measured as described above, it is well known that the amount of combustion air supplied to the burner 3 is related to the rotational speed of the fan 5. Furthermore, it is well known that the amount of fuel gas supplied to the burner 3 is also related to the proportional valve current energized by the proportional valve 72. Therefore, the excess air ratio of the mixture can be estimated using the rotational speed of the fan 5 and the proportional valve current energized by the proportional valve 72. Thus, in this embodiment, the "excess air ratio of the mixture" that decreases in stages from its initial value during the re-ignition operation described later is not a measured value, but an estimated value. Furthermore, the initial value of the excess air ratio of the mixed gas suitable for the ignition of the burner 3, set by the controller 8, is an estimated value of the excess air ratio suitable for the ignition of the burner 3, which takes into account the type of fuel gas, the combustion characteristics of the burner 3, the air supply capacity of the fan 5, etc. This estimated value corresponds to the excess air ratio of the mixed gas required when the hot water supply heat source machine 1a is always used and thus repeatedly performs combustion.

[0035] In the control of controller 8 described below, the speed of fan 5 during ignition is kept constant at a predetermined speed, and the proportional valve current is increased in stages. This increases the amount of fuel gas in the mixture in stages, relatively reducing the amount of air in the mixture and thus lowering the excess air ratio. Furthermore, the proportional valve current value corresponding to the increased amount of fuel gas is stored in controller 8. As described above, the excess air ratio of the mixture is represented by the proportional valve current value.

[0036] When instructed to ignite in burner 3, as described later, controller 8 stops the timer and determines whether the elapsed time Te, calculated from the time of the ignition error determination, is within a predetermined elapsed time (e.g., 30-60 seconds) preset by controller 8 (STEP1). Here, the ignition instruction is performed by instructing the hot water supply heater 1a to ignite (operation ON) via a remote control connected to controller 8, and by opening a hot water supply tap or other faucet at the end of the hot water outlet pipe 4b. If the elapsed time Te is within the predetermined elapsed time, when the ignition instruction is repeated multiple times, the increased fuel gas quantity stored in the control performed according to the previous ignition instruction, and described later at the time of the re-ignition action of igniter 32 performed shortly before the ignition error was determined, i.e., the corresponding proportional valve current value, is read (STEP2). On the other hand, when the hot water supply heat source 1a is set up and combustion is indicated for the first time, since there is no combustion indication before this combustion indication, in STEP2, the above proportional valve current value is replaced by the proportional valve current value corresponding to the initial value of the excess air ratio of the mixed gas that is preset in the controller 8 and suitable for the ignition of the burner 3.

[0037] Next, the following pre-purge process (STEP3) is performed: the fan 5 is driven to supply air into the combustion chamber 2a, thereby expelling the mixture remaining in the combustion chamber 2a through the exhaust passage 6 to the outside. Afterward, the fan 5 is kept at a constant speed according to a predetermined speed, and the main valve 71 and the first capacity switching valve 73a are energized and opened, while the proportional valve 72 is simultaneously energized and opened, supplying the mixture of combustion air and fuel gas to the first section 31 of the burner 3. In the case of the initial ignition operation, the proportional valve current value of the proportional valve 72 at this time is the value corresponding to the initial value of the excess air ratio of the mixture. On the other hand, in the case of the re-ignition operation described later, if the elapsed time Te is within a predetermined elapsed time, the proportional valve current value of the proportional valve 72 at this time is the proportional valve current value corresponding to the increased fuel gas quantity at the time of the re-ignition operation performed shortly before the ignition error was determined. Furthermore, if the elapsed time Te exceeds the specified elapsed time, the proportional valve current value of the proportional valve 72 at this time is the value corresponding to the initial value of the excess air ratio of the mixed gas. Next, the igniter 32 is energized to initiate the ignition action, and a spark is generated using the ignition electrode 31 (STEP4). Moreover, based on the presence or absence of ignition monitoring of the flame rod 33, it is determined whether the first part 31 of the burner 3 has been ignited (STEP5). If the first part 31 of the burner 3 has been ignited, the timer is started to measure the combustion time. This combustion time is measured every time combustion is indicated, and the controller 8 accumulates the measured combustion time and stores and updates the accumulated combustion time Ta (STEP6). In addition, if the first part 31 of the burner 3 has been ignited by the re-ignition action, the stored proportional valve current value corresponding to the increased fuel gas quantity at the time of the re-ignition action before ignition is cleared (STEP7). During the initial combustion indication, the amount of fuel gas is the amount of fuel gas corresponding to the initial value of the excess air ratio of the mixed gas preset in the controller 8. Therefore, even when STEP 7 is executed, the amount of fuel gas does not change. Moreover, the second capacity switching valve 73b is opened, and the flame is transferred to the second part 32 of the burner 3, etc., to switch the combustion capacity.

[0038] Subsequently, controller 8 determines whether combustion has been instructed to stop (STEP8). If combustion has not been instructed to stop, STEP5 to STEP8 are executed repeatedly. If combustion has been instructed to stop, the timer is stopped, and the number of repetitions of the re-ignition action stored and updated by the counter is cleared as described later (STEP9). At this time, the power supply to igniter 32 is stopped, and either the first capacity switching valve 73a, or either the first capacity switching valve 73a or the second capacity switching valve 73b, the proportional valve 72, and the main valve 71 are closed. At the same time, fan 5 is stopped, and combustion ends. Furthermore, standby is maintained until combustion is re-instructed. When the remote control instructs the hot water supply heater 1a to stop combustion (operation OFF), or when the hot water supply valve is closed and water supply stops, a combustion stop instruction is given simultaneously.

[0039] On the other hand, even if the igniter 32 is energized in STEP 4 to initiate ignition and a spark is generated using the ignition electrode 31, and the first part 31 of the burner 3 fails to ignite in STEP 5, the controller 8 temporarily closes the first switching valve 73a, the proportional valve 72, and the main valve 71, and stops the fan 5. Additionally, the ignition action of the igniter 32 is also stopped. Afterwards, the controller 8 determines whether the number of re-ignition actions stored and updated by the counter is the set predetermined number (STEP 10). Here, the re-ignition action is the action of the igniter 32 performing the ignition action again. When the igniter 32 performs the re-ignition action, the controller 8 reopens the closed main valve 71, the proportional valve 72, and the first switching valve 73a, and restarts the fan 5. If the number of re-ignition actions performed by the igniter 32 is less than a predetermined number, the controller 8 determines whether the cumulative combustion time Ta stored and updated in STEP 6 is less than a preset time (STEP 11). Furthermore, if the first part 31 of the burner 3 fails to ignite upon initial combustion indication, the cumulative combustion time Ta is zero since combustion time is not measured, and it is determined to be less than the preset time.

[0040] STEP 11 involves the following determination: The lower limit for reducing the excess air ratio of the gas mixture from its initial value differs depending on whether the hot water supply heat source 1a has been set up recently or has already undergone repeated combustion in the burner 3. Therefore, the excess air ratio of the gas mixture is adjusted appropriately. When the hot water supply heat source 1a is initially activated, air is present in the gas supply path 7. Therefore, even if the excess air ratio of the gas mixture is adjusted to its initial value and the gas mixture is supplied to the first part 31 of the burner 3 during the ignition operation in STEP 4, the actual excess air ratio of the gas mixture supplied to the first part 31 of the burner 3 will be higher due to the air present in the gas supply path 7. Therefore, to ensure combustion of the gas mixture in the burner 3, the excess air ratio needs to be sufficiently reduced. Furthermore, when combustion has already occurred repeatedly in the burner 3, the gas supply path 7 is replaced by fuel gas. Therefore, it is necessary to suppress the decrease in the excess air rate of the mixed gas supplied to the first part 31 of the burner 3 so as not to cause adverse situations such as explosion or generation of carbon monoxide gas at the burner 3.

[0041] Therefore, the controller 8 is set with two lower limits for the excess air ratio of the gas mixture, which are lower than the initial value when reducing the excess air ratio. One lower limit is A, corresponding to a state shortly after the hot water supply heat source 1a is set. The other is B, corresponding to a state where combustion has been repeated multiple times after the hot water supply heat source 1a is set. The second lower limit B is set higher than the first lower limit A (A < B). However, the first lower limit A is also a value presumed to be unlikely to cause an explosion at the burner 3 or the generation of carbon monoxide gas. Furthermore, the controller 8 selects the first lower limit A (STEP12) if it determines that the cumulative combustion time Ta in STEP11 is less than the set time. Alternatively, it selects the second lower limit B (STEP13) if it determines that the cumulative combustion time Ta is greater than the set time.

[0042] The reduction of the excess air ratio of the gas mixture controlled by controller 8 from its initial value, as described above, is achieved by maintaining a constant fan speed at a predetermined speed and progressively increasing the proportional valve current, thereby progressively increasing the fuel gas quantity and relatively reducing the amount of air in the gas mixture. Specifically, at STEP 4, the reduction in the excess air ratio of the gas mixture from its initial value to either the first lower limit A or the second lower limit B, as set by controller 8, is calculated equally based on a predetermined number of repetitions of the re-ignition action. The increase in the proportional valve current corresponding to the reduction in the excess air ratio of the gas mixture for each re-ignition action is set in controller 8. Alternatively, after the re-ignition action has been repeated a predetermined number of times, gradually increasing the reduction in the excess air ratio to the first lower limit A or the second lower limit B, the increase in the proportional valve current for each subsequent repetition is set in controller 8. Furthermore, controller 8 increases the proportional valve current each time it performs a re-ignition action at a specified time interval.

[0043] Furthermore, the controller 8 determines whether the current air excess rate of the gas mixture is higher than the first lower limit A or the second lower limit B, that is, whether the current proportional valve current value is lower than the proportional valve current value corresponding to the first lower limit A or the second lower limit B (STEP 14). If the current air excess rate of the gas mixture is higher than the first lower limit A or the second lower limit B, the controller 8 determines the increase in the proportional valve current by increasing the amount of fuel gas when the igniter 32 performs the re-ignition action (STEP 15). On the other hand, in STEP 14, if the current air excess rate of the gas mixture is lower than the first lower limit A or the second lower limit B, the controller 8 maintains the air excess rate of the gas mixture by keeping the current proportional valve current value unchanged. By doing so, even if the current air excess rate of the gas mixture is lower than the first lower limit A or the second lower limit B due to some factor, adverse situations such as explosion or poor combustion of carbon monoxide gas can be further suppressed. Next, controller 8 stores and updates the proportional valve current value corresponding to the fuel gas quantity determined in STEP 14 (STEP 16), and causes the counter to count and store the number of re-ignition actions (STEP 17). Afterward, it returns to STEP 3, drives fan 5 for pre-cleaning, and then opens main valve 71, proportional valve 72, and first capacity switching valve 73a to energize proportional valve 12 with the proportional valve current value stored and updated in STEP 16, reducing the excess air ratio of the mixture. Furthermore, igniter 32 performs a re-ignition action (STEP 4), and determines whether the first part 31 of burner 3 is ignited (STEP 5). If the first part 31 of burner 3 fails to ignite even after re-ignition, controller 8 repeatedly executes STEP 10 to STEP 17 and STEP 3 to STEP 5. In addition, in this case, the proportional valve current value stored in STEP16 and the number of re-ignition cycles stored in STEP17 are gradually updated when the re-ignition operation is performed.

[0044] If the burner 3 is ignited through the re-ignition action described above, the controller 8 stores and updates the combustion accumulation time Ta as described above (STEP 6). Next, the stored proportional valve current value corresponding to the increased fuel gas quantity at the time of the re-ignition action before ignition is cleared (STEP 7). On the other hand, if the first part 31 of the burner 3 fails to ignite even after repeated re-ignition actions of a predetermined number of times, the controller 8 determines that an ignition error has occurred, cancels the combustion indication, and issues an alarm for the ignition error (STEP 18). At this time, the first switching valve 73a, the proportional valve 72, and the main valve 71 are closed, and the fan 5 is stopped. In addition, the timer is started to measure the elapsed time Te from the time the ignition error was determined (STEP 19). The measured elapsed time Te is stored in the controller 8 and is gradually updated. Subsequently, controller 8 determines whether the ignition error alarm has been cleared (STEP 20). If it has been cleared, it proceeds to STEP 9 to clear the stored number of re-ignition attempts. Alternatively, the ignition error alarm can be cleared via remote control or by shutting off the hot water supply.

[0045] Furthermore, when the controller 8 is instructed to ignite again after the ignition error alarm has been cleared, as described above, it stops the timer at STEP 1 and again checks whether the elapsed time Te is within the prescribed elapsed time. If it is within the prescribed elapsed time, it is presumed that the re-instruction of combustion is a continuous instruction with the previous combustion instruction. Therefore, the controller 8 reads the stored proportional valve current value corresponding to the increased fuel gas quantity at the time of the re-ignition operation performed shortly before the ignition error was determined (STEP 2). At this time, the timer is reset. On the other hand, if the elapsed time Te exceeds the prescribed elapsed time, the proportional valve current value is cleared (STEP 21), and the timer is reset, performing the same control as when combustion was initially indicated, as described above. That is, when combustion is indicated again after the elapsed time Te exceeds the prescribed time, it is presumed that the re-instruction of combustion is a new combustion instruction unrelated to the previous combustion instruction; therefore, the excess air ratio of the mixture at the time the igniter 32 performs the ignition operation returns to its initial value.

[0046] Reference Figure 3 This describes a second mode of control performed by the controller 8 included in the combustion device 1 of the present invention. Figure 3 The controller 8 shown controls and Figure 2 The differences in the controls shown are as follows: Firstly, the control mechanism is omitted. Figure 2STEP1, STEP2, STEP19, and STEP21 are shown. Additionally, STEP22 is added between STEP20 and STEP9. In STEP22, the stored proportional valve current value corresponding to the increased fuel gas quantity during the re-ignition operation of the igniter 32 performed shortly before the ignition error was determined is cleared. That is, after determining whether an alarm clearance instruction is received (STEP20), the following steps are performed. Figure 2 STEP21 is shown. Thus... Figure 3 The control performed by the controller 8 shown is generally applicable to situations where the number of re-ignition actions required until the first part 31 of the burner 3 is ignited is less than the number of re-ignition cycles required. Figure 1 The hot water supply heat source unit 1a shown also includes, for example, a heating heat source unit and other combustion devices 1.

[0047] Moreover, including Figure 1 The controller 8 of the combustion device 1, including the hot water supply heat source 1a shown, is as follows: Figure 1 As shown, it can be cleared in Figure 2 and Figure 3 The combustion accumulation time clearing mechanism 81, which stores the combustion accumulation time Ta in STEP6, is shown. The fuel accumulation time clearing mechanism 81 can also be set in the remote control when the remote control is connected to the controller 8.

[0048] In such a combustion device 1, if the cumulative combustion time Ta is less than a predetermined set time, it is presumed that the gas mixture with an actual excess air ratio higher than the initial value due to residual air in the gas supply path 7 is supplied to the first part 31 of the burner 3, thus preventing the first part 31 of the burner 3 from igniting. In this case, the controller 8 reduces the excess air ratio of the gas mixture in stages from the initial value based on the first lower limit value A. Furthermore, the re-ignition operation of the igniter 32, which serves as the ignition mechanism, is repeatedly executed. Therefore, as before, the ignition of the first part 31 of the burner 3 is easily achieved. In addition, if the cumulative combustion time Ta is greater than or equal to the predetermined set time, it is presumed that the gas supply path 7 has been replaced by the gas mixture. In this case, the controller 8 reduces the excess air ratio of the gas mixture in stages from the initial value based on the second lower limit value B, and the re-ignition operation of the igniter 32 is repeatedly executed. Therefore, it is not necessary to reduce the excess air ratio of the gas mixture to the required level. When the igniter 32 performs the reignition action, it can suppress adverse situations such as explosion or poor combustion of carbon monoxide gas.

[0049] Furthermore, the controller 8 reduces the excess air ratio of the mixture from its initial value during the re-ignition operation of the igniter 32 by progressively increasing the amount of fuel gas supplied to the first part 31 of the burner 3. This progressive reduction of the excess air ratio of the mixture from its initial value during the re-ignition operation of the igniter 32 can also be achieved by progressively decreasing the amount of combustion air supplied to the first part 31 of the burner 3. While the specific methods for increasing the amount of fuel gas or decreasing the amount of combustion air may vary in complexity under the control of the controller 8, the following five modes can be imagined.

[0050] • Mode 1

[0051] The amount of air used for combustion is kept constant by a specified amount, while the amount of fuel gas is increased.

[0052] Mode 2

[0053] Increasing the amount of air used for combustion, while simultaneously increasing the amount of fuel gas, results in a decrease in the excess air ratio of the gas mixture.

[0054] Mode 3

[0055] Reduce the amount of air used for combustion while increasing the amount of fuel gas.

[0056] • Mode 4

[0057] The amount of fuel gas is kept constant by a specified amount, and the amount of air used for combustion is reduced.

[0058] Mode 5

[0059] Reducing the amount of fuel gas consumed also reduces the amount of air used for combustion, resulting in a decrease in the excess air ratio of the gas mixture.

[0060] By progressively increasing the amount of fuel gas supplied to the first part 31 of the burner 3, the excess air ratio of the mixture during the re-ignition operation of the igniter 32 is progressively reduced from its initial value, which conforms to Modes 1, 2, and 3 described above. By doing so, compared to Modes 4 and 5 described above, the amount of fuel gas passing through the fuel supply path 7 towards the first part 31 of the burner 3 is increased, thus the air remaining in the fuel supply path 7 can be replaced by fuel gas earlier. Therefore, ignition of the first part 31 of the burner 3 can be achieved earlier. Furthermore, as long as the amount of combustion air supplied to the first part 31 of the burner 3 is kept constant or increased at a predetermined speed as in the above embodiments, and the fuel gas quantity is progressively increased by increasing the proportional valve current to reduce the excess air ratio of the mixture (Modes 1 and 2 described above), it is not necessary to reduce the amount of combustion air, thereby maintaining the wind resistance performance of the combustion device 1 effectively.

[0061] Furthermore, if the elapsed time Te from the time of ignition error determination or the time of ignition error alarm clearance to the time of combustion re-indication is within a predetermined elapsed time, it is presumed that the initial combustion indication and the combustion re-indication are issued consecutively. Therefore, the excess air ratio of the gas mixture at the time of combustion re-indication and the excess air ratio of the gas mixture at the time of initial combustion indication can be lower than the initial value. As a result, the excess air ratio of the gas mixture can be reduced in stages towards the first lower limit value A or the second lower limit value B as early as possible, thereby facilitating the ignition of the first part 31 of the burner 3. In addition, if the excess air ratio of the gas mixture at the time of combustion re-indication is lower than the excess air ratio of the gas mixture stored at the time of the re-ignition operation of the igniter 32 performed shortly before the ignition error was determined, the reduction of the excess air ratio of the gas mixture will be further promoted, thus further facilitating the ignition of the first part 31 of the burner 3. For example, consider the following scenario: if the predetermined number of re-ignition cycles of igniter 32 is not reached (either the first lower limit A or the second lower limit B), and the re-ignition cycle of igniter 32 becomes the predetermined number, the controller 8 will determine that an ignition error has occurred. In this case, adjusting the excess air ratio of the gas mixture at the time of combustion re-indication, as described above, will facilitate earlier ignition of the first part 31 of burner 3. On the other hand, if the elapsed time Te from the time of ignition error determination or the time of ignition error alarm clearance to the time of combustion re-indication exceeds the predetermined elapsed time, it is presumed that the initial combustion indication and the combustion re-indication are intermittent and independent indications. Therefore, the excess air ratio of the gas mixture at the time of combustion re-indication can be returned to the initial value, and the ignition operation can be restarted. This ensures the safety of the ignition operation.

[0062] Furthermore, after the combustion device 1 has been installed and a predetermined combustion accumulation time Ta has elapsed, due to refilling of the gas cylinder or updating of the gas supply line 7, sometimes the excess air ratio of the gas mixture actually supplied to the first part 31 of the burner 3 may be higher than the initial value because air may remain in the gas supply line 7. In this case, the combustion accumulation time clearing mechanism 81 can clear the combustion accumulation time Ta stored in the controller 8. As a result, the lower limit of the excess air ratio of the gas mixture, which decreases in stages from the initial value when the igniter 32 performs a re-ignition operation, is updated from the second lower limit B back to the first lower limit A. Therefore, similar to the case of a new installation of the combustion device 1, ignition of the first part 31 of the burner 3 can be easily achieved.

[0063] While embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above. For example, the configuration of the burner 3, or the configuration of the gas supply passage 7 associated with the burner 3, can have various forms. Furthermore, in order to adjust the amount of fuel gas, if a variable throttling orifice with a changeable orifice diameter is provided in the gas supply passage 7, the controller 8 controls the variable throttling orifice. By keeping the fan 5 at a constant speed at a predetermined speed and gradually increasing the orifice diameter of the variable throttling orifice, the amount of fuel gas is increased, thereby gradually reducing the excess air ratio of the mixture from an initial value. In this case, the orifice diameters of the variable throttling orifice corresponding to the first lower limit value A and the second lower limit value B, respectively, are set in the controller 8. The controller 8 stores and updates the orifice diameters of the variable throttling orifice corresponding to the increased amount of fuel gas.

[0064] Furthermore, as described above, by progressively reducing the amount of combustion air supplied to the first part 31 of the burner 3, the excess air ratio of the gas mixture can be progressively reduced from an initial value. In this case, the amount of fuel gas supplied to the burner 3 is kept constant at a predetermined amount, and the speed of the fan 5 is reduced, thereby reducing the amount of combustion air (mode 4 described above). Thus, when the amount of combustion air is reduced and the excess air ratio of the gas mixture is reduced, the speed of the fan 5 corresponding to the first lower limit value A and the second lower limit value B, respectively, is set in the controller 8. The controller 8 stores and updates the speed of the fan 5 corresponding to the reduced amount of combustion air.

[0065] That is, as a method to reduce the excess air ratio of the mixed gas supplied to the first part 31 of the burner 3 in stages, any appropriate mode can be selected from the above five modes 1 to 5, as long as it can reduce the excess air ratio of the mixed gas supplied to the first part 31 of the burner 3.

[0066] In addition, Figure 2 In the control performed by the controller 8 shown, STEP 19 may not be between STEP 18 and STEP 20, but rather inserted between STEP 20 and STEP 9. In this case, when the ignition error alarm is cleared, the timer starts, and the elapsed time Te stored in the controller 8 can be the elapsed time from when the ignition error alarm is cleared to when combustion is re-indicated. Furthermore, the elapsed time that serves as the criterion for STEP 1 can be changed to a factor related to the elapsed time from when the ignition error alarm is cleared to when combustion is re-indicated.

[0067] Furthermore, when an ignition error is detected or combustion is initiated again after a predetermined time has elapsed following the clearing of the ignition error alarm, the excess air ratio of the gas mixture at the time of ignition by the igniter 32 is not only the excess air ratio stored by the controller 8 during the re-ignition operation of the igniter 32 performed shortly before the ignition error was detected, but can also be a value smaller than that. Examples of excess air ratios in this case include: a value lower than the aforementioned excess air ratio stored by the controller 8 that occurs during the second re-ignition operation and does not reach the first lower limit A or the second lower limit B.

Claims

1. A combustion apparatus comprising: a burner disposed in a combustion chamber for burning a mixture of combustion air and fuel gas; a fan for supplying combustion air to the burner; a fuel gas supply line for supplying fuel gas to the burner; a proportional valve disposed in the fuel gas supply line; an ignition mechanism for igniting the burner; an ignition monitoring mechanism for monitoring the ignition of the burner; and a controller for controlling the fan, the proportional valve, and the ignition mechanism. The controller is pre-set with an air excess ratio suitable for burner ignition as the initial value. The controller is configured to: when instructed to burn in the burner, adjust the amount of combustion air and fuel gas to achieve an initial excess air ratio in the mixture; if the burner fails to ignite even when the ignition mechanism is activated, progressively reduce the excess air ratio from the initial value while repeatedly re-igniting the mixture. Its features are, The controller accumulates and stores the combustion time of the burner. The controller sets a first lower limit value and a second lower limit value respectively to serve as the lower limit value of the excess air ratio of the gas mixture that is reduced from the initial value when the ignition mechanism performs a re-ignition action. The first lower limit value is the value when the cumulative combustion time is less than a predetermined set time, and the second lower limit value is the value that is higher than the first lower limit value when the cumulative combustion time is greater than the predetermined set time.

2. The combustion device according to claim 1, characterized in that, The controller is configured to progressively reduce the excess air ratio of the gas mixture when the ignition mechanism performs a re-ignition operation by progressively increasing the amount of fuel gas supplied to the burner, starting from the initial value.

3. The combustion device according to claim 1 or 2, characterized in that, The controller is configured to: count the number of re-ignition actions of the ignition mechanism; if the burner fails to ignite even after a predetermined number of repetitions, an ignition error is determined, the combustion indication is canceled, and an alarm is issued to indicate the ignition error. The controller stores the excess air ratio of the gas mixture at the time of the re-ignition action of the ignition mechanism shortly before the ignition error is determined. After the ignition error is determined, the combustion indication is cancelled, and the ignition error alarm is issued, and combustion is re-indicated after the ignition error alarm is lifted, if the elapsed time from the time of the ignition error determination or the time of the ignition error alarm being lifted to the time of the re-indication of combustion is within a predetermined elapsed time, the controller adjusts the excess air ratio of the gas mixture at the time of the ignition action of the ignition mechanism to be below the stored excess air ratio.

4. The combustion device according to claim 1 or 2, characterized in that, The controller includes a combustion accumulation time clearing mechanism for clearing the stored combustion accumulation time.

5. The combustion device according to claim 3, characterized in that, The controller includes a combustion accumulation time clearing mechanism for clearing the stored combustion accumulation time.

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