JPH1183004A - Combustion apparatus and firing control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combustion apparatus of reducing an ignition sound upon firing in timing not intended by an operator. SOLUTION: A firing condition set section 52 includes as firing modes to fire a burner 12 an ordinary firing mode, and a static sound firing mode where an air fuel ratio is set higher than the ordinary firing mode, and uses the static sound firing mode as the firing mode to fire the burner 12 excepting a case where firing is performed at once in response to operation of an operator. A firing sound is reduced by setting the air fuel ratio higher, and hence a user is prevented from becoming uneasy and uncomfortable even when the firing is performed in timing not intended by the user.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion apparatus having a burner and an ignition device, and an ignition control method for controlling ignition conditions of the burner.

[0002]

2. Description of the Related Art In recent years, in order to further improve the comfort of a conventionally used combustion device such as a water heater,
There is a type provided with a function of keeping the temperature of the hot water in the heat exchanger within a predetermined temperature range in a state where there is no flow of water so that hot water of almost the set temperature is discharged from the beginning of hot water supply. In such a water heater, the temperature of the hot water in the heat exchanger is usually monitored by a temperature sensor, and when the temperature of the hot water falls below the allowable lower limit temperature, the burner is left unopened for a short time of about 2 seconds, for example. It burns for a long time to keep the hot water temperature within the target temperature range.

A so-called one-can-two-channel water heater having a bath reheating function has a hot water supply channel and a reheating channel for a bath which are guided to a common heat exchanger and heated by a burner. In such a water heater, when the burner is burned, both the water in the hot water supply channel and the water in the reheating channel are heated, so that when reheating the bath, the hot water in the hot water supply channel boils. Combustion is performed intermittently so as not to be performed.

[0004] In these combustion devices, ignition in all cases, such as ignition for keeping heat and ignition for reheating a bath, in addition to the case of tapping, is fixed in advance as a value at which no explosion occurs and non-ignition hardly occurs. The air-fuel ratio is determined.

[0005]

The ignition at the time of keeping the hot water in the heat exchanger in preparation for the next hot water supply and the ignition at the time of reheating a bath with a one-can, two-channel water heater are performed by water. The operation is not performed in response to an operation from the operator as in the case of opening the tap and tapping water, but is performed autonomously by the device itself determining the ignition timing based on predetermined conditions. In addition, the ignition for the heat retention function and the reheating is performed repeatedly and intermittently.

Therefore, if the ignition is performed at a timing unintended by the operator at a relatively small air-fuel ratio fixedly set in advance as a value at which non-ignition hardly occurs, the ignition sound becomes loud and the user is uneasy. They can make you feel uncomfortable.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the prior art, and provides a combustion apparatus capable of reducing the ignition sound of ignition performed at a timing not intended by the operator. It is intended to be.

[0008]

The gist of the present invention to achieve the above object lies in the following inventions. [1] In a combustion device provided with a burner (12) and an ignition device (15), an ignition condition setting means (52) for setting an air-fuel ratio when igniting the burner (12) is provided,
The ignition condition setting means (52) includes a normal ignition mode and a silent ignition mode in which an air-fuel ratio at the time of ignition is set higher than the normal ignition mode as an ignition mode for igniting the burner (12). A combustion apparatus characterized in that an ignition mode for igniting the burner (12) is set to the silent ignition mode except when the ignition is performed immediately according to the following.

[2] Burner without water flow (12)
Is burned to control the temperature of the hot water in the heat exchanger (13) in the predetermined temperature range in preparation for the next hot water supply. A heat retention control means (51) and the burner (1);
2) an ignition condition setting means (52) for setting an air-fuel ratio at the time of igniting, wherein the ignition condition setting means (52) comprises:
An ignition mode for igniting the burner (12) includes a normal ignition mode and a silent ignition mode in which an air-fuel ratio at the time of ignition is set higher than the normal ignition mode.
(1) A combustion device wherein the ignition mode for igniting the burner (12) in a state where there is no water flow is set to the silent ignition mode.

[3] The ignition condition setting means (52)
When non-ignition occurs in the ignition in the silent ignition mode, the air-fuel ratio for the next ignition in the silent ignition mode is lower than the current air-fuel ratio in which the non-ignition occurred [1] or [2]. ] The combustion device according to [1].

[4] The ignition condition setting means (52)
When non-ignition occurs in the ignition in the silent ignition mode, the air-fuel ratio for the next ignition in the silent ignition mode is reduced as much as the air-fuel ratio in the normal ignition mode [1], The combustion device according to [2] or [3].

[5] A silent initial air-fuel ratio storage means (53) for storing an initial value of the air-fuel ratio when the ignition is performed in the silent ignition mode is provided, and the initial value of the air-fuel ratio stored therein is stored in the silent ignition mode. The combustion apparatus according to [3] or [4], wherein the air-fuel ratio at the time of ignition is updated by lowering the air-fuel ratio in (3).

[6] Burner (12) and ignition device (1)
5) The ignition control method for controlling the ignition conditions of the combustion device comprising: a normal ignition mode as an ignition mode for igniting the burner (12); and a silent ignition mode in which the air-fuel ratio at the time of ignition is set higher than this. Wherein the ignition mode for igniting the burner (12) is set to the silent ignition mode except when the burner (12) is ignited immediately in response to an operation by an operator.

The present invention operates as follows. The ignition condition setting means (52) includes a normal ignition mode and a silent ignition mode in which the air-fuel ratio at the time of ignition is set higher than the normal ignition mode as an ignition mode for igniting the burner (12). Accordingly, the ignition mode for igniting the burner (12) is set to the silent ignition mode unless the ignition is performed immediately.

For example, in the case of a one-can-two-channel water heater with a bath kettle, if the operator taps the water tap to open the tap, the ignition is performed in the normal ignition mode. On the other hand, in the case of intermittent repetitive ignition at a timing not intended by the operator, such as reheating of a bath, the burner (12) is ignited in the silent ignition mode. Since the air-fuel ratio at the time of ignition in the silent ignition mode is set to a higher value than that in the normal ignition mode, the concentration of the combustion gas is low and the ignition is performed with a relatively small ignition sound. As described above, since the ignition sound at the time of ignition at a timing not intended by the operator is reduced, it is possible to prevent the user from feeling uneasy or giving a discomfort.

Further, the burner (12) is provided without water flow.
For burning the burner (12) in a state where there is no flow of water in a combustion apparatus having a function of burning water and keeping the temperature of the hot water in the heat exchanger (13) within a predetermined temperature range in preparation for the next hot water supply. Set the ignition mode to silent ignition mode. Ignition for keeping the hot water in the heat exchanger (13) within a predetermined temperature range in preparation for the next hot water supply is performed autonomously by the device itself in accordance with the drop in the hot water temperature, and therefore, ignition is performed at a timing not intended by the user. And frequently at relatively short intervals. Therefore, by performing such an ignition in the silent ignition mode, the user does not feel uneasy or feel uncomfortable due to the frequently generated ignition sound.

The ignition condition setting means (52) determines the air-fuel ratio for the next ignition in the silent ignition mode from the current air-fuel ratio in which the non-ignition has occurred when the ignition in the silent ignition mode fails. Set to a lower value. The air-fuel ratio in the normal ignition mode is set to a value that does not cause an explosion at the time of ignition and hardly causes misfire, but since the air-fuel ratio in the silent ignition mode is set higher than the air-fuel ratio in the normal ignition mode, Misfire easily occurs.

Therefore, when misfiring occurs during ignition in the silent ignition mode, the air-fuel ratio is gradually lowered, so that misfiring can be prevented from occurring repeatedly. In addition, by setting the limit at the time of lowering the air-fuel ratio in the silent ignition mode to the air-fuel ratio of the normal ignition mode, explosion does not occur and safety can be ensured.

Further, there is provided a silent initial air-fuel ratio storage means (53) for storing an initial value of the air-fuel ratio when the ignition is performed in the silent ignition mode, and the initial value of the air-fuel ratio stored in the storage unit is stored in the silent ignition mode. The air-fuel ratio is updated with the value of the air-fuel ratio at the time of ignition by lowering the air-fuel ratio. As a result, it is possible to prevent non-ignition from occurring each time ignition is started in the silent ignition mode.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Each drawing shows an embodiment of the present invention. Water heater 10 as combustion device according to the present invention
Has a function of supplying hot water into the faucet or the bathtub 40, a function of reheating the hot water in the bathtub, and a function of pouring unheated water into the bathtub through the reheating path 31. In addition, the burner is burned for 1 to 2 seconds every few minutes without opening to keep the remaining water in the heat exchanger within a predetermined target temperature range so that hot water of the set temperature is discharged immediately after opening. It has a heat retention function.

As shown in FIG. 1, the water heater 10 includes a combustion chamber 11. A burner 12 is provided below the combustion chamber 11, and heat from the burner 12 is provided above the combustion chamber 11. Heat exchangers 13 for transmitting water and the like are arranged. The heat exchanger 13 has both a hot water supply pipe 21 for flowing hot water and a reheating circulating pipe 31 for circulating water in the bathtub for reheating. The heat from the burner 12 is transferred to both pipes 2
It has a function of transmitting heat to the fluid in the first and 31 and heating.

A fixed bypass is provided between a water supply side flow path 21a connected to the inlet of the heat exchanger 13 of the hot water supply pipe 21 and a water discharge side flow path 21b connected to the output side of the heat exchanger 13. Path 22 and bypass path 2 with flow control valve 23 interposed
4 are connected. In the hot water heated by the heat exchanger 13,
The feed water is mixed through the fixed bypass passage 22 and the bypass passage 24, and the bypass ratio can be controlled by the flow control valve 23. In addition, hot water supply pipe 2
A flow control valve 25 for controlling the total flow rate of hot water and the bypass ratio is provided on the side of the first hot water-side flow path 21b.

In the vicinity of the inlet and outlet of the hot water supply pipe 21, flow sensors 26a and 26b for detecting the presence or absence of water flow and the amount of water flow are provided. In addition, a water input thermistor 27 for detecting the temperature of the water supply is provided near the inlet of the hot water supply pipe 21, and a heat exchange thermistor for measuring the temperature of the heated water is provided near the outlet of the heat exchanger 13. Further, near the outlet of the hot water supply pipe 21, a tapping thermistor 29 for detecting tapping temperature is attached. Further, a water pipe thermistor 28a is provided at the U vent portion of the hot water supply fin pipe of the heat exchanger 13.

The recirculating pipe 31 for reheating includes a bath return pipe section 31a for returning water in the bathtub 40 to the heat exchanger 13, and a bath pipe section 31b for sending hot water heated by the heat exchanger 13 to the bathtub 40. It is composed of Bath return pipe part 3
In the middle of 1a, a circulation pump 32 and a bath return pipe section 31
A bath running water switch 33 for detecting the presence or absence of water flow in a is provided. A bath temperature thermistor 34 for detecting the temperature of hot water flowing from the bathtub 40 is attached near the bath water switch 33.

A tapping-side flow path 21b of the hot-water supply pipe 21;
The bath return pipe portion 31a is connected by a pouring pipe 36 provided with a pouring electromagnetic valve 35, and supplies the water heated by the heat exchanger 13 or the water that is not heated without igniting the burner 12 to the bath. Bathtub 40 through pouring pipe 36
It can be poured into.

The supply and exhaust are forcibly performed by blowing supply air from below the combustion chamber 11 by the combustion fan 14, and the exhaust is discharged from the upper part of the combustion chamber 11. In the vicinity of the burner 12, an ignition device 15 is provided.
Is provided. The combustion gas supplied to the burner 12 is
On / off control is performed by the gas solenoid valve 16, the original gas solenoid valve 17, and the gas switching valve 18. Further, the amount of combustion gas supplied to the burner 12 is adjusted by a gas proportional valve 19.

The water heater 10 includes a control unit 50 that controls the operation of the water heater 10 such as the combustion control of the burner 12,
An operation unit 60 including a bath remote controller and a main remote controller is provided. The control unit 50 includes a heat retention control unit 51 that performs combustion control for keeping the hot water in the heat exchanger 13 within a predetermined temperature range in a state where no water flows, and an ignition that sets an air-fuel ratio when the burner 12 is ignited. A condition setting unit 52 and a silent initial air-fuel ratio storage unit 53 for storing an initial value of the air-fuel ratio in the silent ignition mode are provided. The ignition condition setting unit 52 adjusts the air-fuel ratio according to the number of rotations of the combustion fan 14 and / or the amount of combustion gas supplied to the burner 12 by the gas proportional valve 19 and the amount of combustion gas supplied to the burner 12. It has become.

Although not explicitly shown in FIG. 1, the controller 50 includes various solenoid valves such as the combustion fan 14, the gas proportional valve 19, and the like.
Flow control valves 23, 25, flow sensors 26a, 26b,
Various electrical components in the water heater 10 such as a water input thermistor 27, a heat exchange thermistor 28, a water pipe thermistor 28a, and a hot water thermistor 29 are connected. Note that the control unit 50
It is composed of circuits mainly including a PU (central processing unit), a ROM (read only memory), a RAM (random access memory) and the like.

Next, the operation will be described. FIG. 2 shows the water heater 10.
Shows the flow of the operation performed when the burner 12 is ignited. The ignition condition setting unit 52 included in the control unit 50 determines whether the current ignition is an instant ignition in response to a user operation or an autonomous ignition other than this (step S101). Here, the autonomous ignition refers to ignition for performing reheating of a bath or ignition for keeping the hot water of the heat exchanger 13 in a predetermined temperature range in a state where there is no flow of water. It does not include one that immediately ignites in response to a user operation, such as ignition when tapping water in response to a tapping operation.

If the current ignition is the above-described autonomous ignition (step S101; Y), the air-fuel ratio at the time of ignition is set to the silent initial air-fuel ratio (step S102). This value is the initial value of the air-fuel ratio when the ignition is performed in the silent ignition mode, and is stored in the silent initial air-fuel ratio storage unit 53.
On the other hand, when the current ignition is not the autonomous ignition such as the ignition based on tapping according to the opening (Step S101; N), the normal air-fuel ratio in the normal ignition mode is set to a predetermined normal air-fuel ratio (Step S103).

FIG. 3 shows the relationship between the air-fuel ratio determined by the gas amount and the fan air amount and the ignition state. The air-fuel ratio is a value obtained by dividing the amount of air supplied by the combustion fan 14 (fan air volume) by the amount of gas supplied to the burner 12. For example, even if the fan air volume is the same, the air-fuel ratio decreases as the gas amount increases, and the air-fuel ratio increases as the gas amount increases. Conversely, even if the gas amount is the same, the air-fuel ratio decreases as the fan air flow decreases, and the air-fuel ratio increases as the fan air flow increases.

As shown in FIG. 3, when the air-fuel ratio falls below a predetermined lower limit, an explosion ignition region 71 where an explosion occurs at the time of ignition.
become. When the air-fuel ratio is equal to or higher than the predetermined upper limit, the non-ignition region 72 is not ignited or hardly ignited. The ignition sound becomes larger as it approaches the explosion ignition area 71 and becomes smaller as it approaches the non-ignition area 72. Normal air-fuel ratio 73
Is set substantially at the center between the explosion ignition region 71 and the non-ignition region 72, and the silent air-fuel ratio 74 is set higher than the normal air-fuel ratio 73 and close to the non-ignition region 72.

In the figure, a normal air-fuel ratio 73 and a silent air-fuel ratio 74 are shown.
Represents a range in which the actual air-fuel ratio is expected to fluctuate with respect to the set value of the air-fuel ratio. A vertical arrow 75 passing through the center of the circle indicates a range in which the amount of gas supplied to the burner 12 varies depending on the accuracy of the gas proportional valve 19 and the like. A horizontal arrow 76 indicates a range in which the amount of air varies due to headwind or suction from the exhaust stack, characteristics of the combustion fan 14, or the like.

When the set value of the air-fuel ratio is the normal air-fuel ratio 73, it is possible to ignite almost certainly and ignite without causing an explosion even if the gas amount and the air amount vary. On the other hand, when the air-fuel ratio is set to the silent air-fuel ratio 74, if the variation in the gas amount or the like is large, the actual air-fuel ratio may enter the non-ignition region 72 and cause non-ignition.

If the current ignition is autonomous ignition, the ignition operation is performed at the silent air-fuel ratio described above (step S10).
4). After the ignition operation, the presence or absence of ignition is detected by a flame rod or the like (step S105), and when non-ignition occurs due to a variation in air volume or the like (step S105;
N), the air-fuel ratio is gradually lowered with the normal air-fuel ratio as the air-fuel ratio in the normal ignition mode as a limit, and the ignition is attempted again (step S106; N, step S107). When ignition is confirmed (Step S105; Y), the current air-fuel ratio is set as the silent initial air-fuel ratio, and the content stored in the silent initial air-fuel ratio storage unit 53 is updated to the value (Step S10).
8).

Thus, the next time the ignition operation is performed in the silent ignition mode, the ignition is performed from the air-fuel ratio which succeeded in the ignition this time, so that the possibility of occurrence of the non-ignition from the first time can be reduced. If ignition does not occur even when the air-fuel ratio is lowered to the normal air-fuel ratio, re-ignition is attempted up to a preset upper limit number of times.
109; Y), considering the safety, end the ignition processing.

If the current ignition is not the autonomous ignition, the normal air-fuel ratio is set (step S103) and the ignition operation is performed (step S110). If misfire has occurred (step S111; N), re-ignition is attempted up to a predetermined upper limit number of times (step S112; N). If ignition still does not occur (step S112; Y), an error display or the like is performed. (Step S113) The process ends. The reason for displaying an error only when the auto-ignition is not auto-ignited and finally becomes non-ignited is that this ignition was performed directly in response to the user's operation such as opening, so it is considered that there is an abnormality. This is to notify the user who is operating. In the case of the autonomous ignition, the ignition is not based on the operation of the user, and if an error is displayed, the user is rather uneasy. Therefore, the error is not displayed.

FIGS. 4 to 6 show various modes for lowering the air-fuel ratio when misfiring occurs in the silent ignition mode. In each figure, a mark 81 represents the values of the gas amount and the fan air flow when igniting in the silent ignition mode, and a mark 82 represents the values of the gas amount and the fan air flow when igniting in the normal ignition mode. . The air-fuel ratio may be determined by any one of the modes shown in FIGS.

In FIG. 4, when lowering the air-fuel ratio, the amount of gas supplied to the burner 12 is increased while maintaining the fan airflow at a constant value. Since the change in the amount of gas supplied to the burner 12 has better responsiveness than the change in the rotation speed of the combustion fan 14, the air-fuel ratio can be rapidly reduced. However, if misfiring occurs again, the pre-purge time until the next ignition becomes longer due to the higher gas concentration.

FIG. 5 shows that the air-fuel ratio is lowered by lowering the fan airflow while keeping the amount of gas supplied to the burner 12 constant. The amount of combustion per one time for keeping the hot water of the heat exchanger 13 warm without flowing water is very small in a short time of about 1 to 2 seconds. Therefore, if the amount of gas at the time of ignition is increased in order to lower the air-fuel ratio, the amount of combustion per operation cannot be controlled accurately. However, by lowering the air-fuel ratio by the fan air flow while keeping the gas amount constant, Can be accurately controlled.

Further, since the air-fuel ratio is changed by lowering the fan rotation speed, the first fan ignition at the initial silent air-fuel ratio in the next silent ignition mode is performed in a short time because the required fan rotation speed is low. Can be ignited. FIG.
As shown in (2), both the gas amount and the fan air amount may be changed to lower the air-fuel ratio.

As described above, the two ignition modes, the silent ignition mode and the normal ignition mode, are provided, and when the burner 12 is ignited at a timing not intended by the user, the air-fuel ratio is set higher than in the case of performing the normal ignition. Therefore, the ignition sound at the time of ignition at a timing not intended by the user can be reduced while the normal ignition is reliably performed, and the user does not feel uneasy or uncomfortable.

Further, when misfiring occurs during ignition in the silent ignition mode, the air-fuel ratio is gradually lowered and re-ignition is attempted, so that no misfiring is left, or no misfiring is repeated forever. . Further, since the air-fuel ratio is reduced with the air-fuel ratio in normal ignition as a limit, explosion does not occur and safety can be ensured. In addition, since the air-fuel ratio at the time of ignition in the silent ignition mode is updated as the initial value of the air-fuel ratio at the time of ignition in the silent ignition mode next time, occurrence of non-ignition can be reduced from the next time.

In the embodiment described above, the ignition for keeping the hot water in the heat exchanger in a state where hot water is not supplied and the ignition for performing the reheating of the bath with the one-can-two-channel water heater are set to the silent ignition mode. However, if the ignition is performed at a timing determined on the water heater 10 side irrespective of the user's will, except for the case where the ignition is performed immediately according to the operation from the operator, However, the invention is not limited to ignition for reheating.

Further, in the embodiment, the error is not displayed even if the ignition is not finally performed by the autonomous ignition.
Even in the case of autonomous ignition, an error display may be performed in a situation where it is estimated that there is an abnormality in the ignition device or the like.

[0046]

According to the combustion apparatus of the present invention, when the apparatus side autonomously ignites the burner 12 at a timing not intended by the user, the air-fuel ratio is set higher than in the case of performing normal ignition. It is possible to reduce ignition noise when ignition is performed at a timing not intended by the user while reliably performing normal ignition, and it is possible to prevent the user from feeling uneasy or uncomfortable.

Further, when misfire occurs due to ignition at a high air-fuel ratio, the air-fuel ratio is gradually lowered and ignition is attempted again.
There is no such thing as being left unignited or igniting forever. Further, since the air-fuel ratio is reduced with the air-fuel ratio in normal ignition as a limit, explosion does not occur and safety can be ensured. In addition, since the air-fuel ratio at the time of ignition in the silent ignition mode is updated to the initial value of the air-fuel ratio at the time of ignition in the silent ignition mode next time, occurrence of non-ignition in the ignition in the silent ignition mode from the next time onward is reduced. Can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating an outline of a configuration of a combustion device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a flow of an operation performed by the combustion device according to the embodiment of the present invention at the time of ignition.

FIG. 3 is an explanatory diagram showing a relationship between an air-fuel ratio determined by a gas amount and a fan air amount and an ignition state.

FIG. 4 is an explanatory diagram showing a manner in which the amount of gas supplied to a burner is increased while the fan airflow is kept at a constant value when the air-fuel ratio is lowered.

FIG. 5 is an explanatory diagram showing a manner in which the amount of gas supplied to the burner when the air-fuel ratio is lowered is kept at a constant value and the fan airflow is reduced.

FIG. 6 is an explanatory diagram showing a state where both the fan air volume and the gas volume supplied to the burner are changed when lowering the air-fuel ratio.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Water heater 12 ... Burner 13 ... Heat exchanger 14 ... Combustion fan 15 ... Ignition device 19 ... Gas proportional valve 26a, 26b ... Flow sensor 50 ... Control part 51 ... Heat retention control part 52 ... Ignition condition setting part 53 ... Silent Initial air-fuel ratio storage unit 73: Normal air-fuel ratio 74: Silent air-fuel ratio

Claims (6)

[Claims] 1. A combustion apparatus comprising a burner and an ignition device, comprising: an ignition condition setting means for setting an air-fuel ratio when the burner is ignited, wherein the ignition condition setting means comprises an ignition when the burner is ignited. The mode includes a normal ignition mode and a silent ignition mode in which the air-fuel ratio at the time of ignition is set higher than this, and an ignition mode for igniting the burner except when the ignition is performed immediately according to an operation from an operator. Is set in the silent ignition mode. 2. A combustion apparatus having a function of burning a burner in a state where there is no water flow and keeping a temperature of a hot water in a heat exchanger within a predetermined temperature range in preparation for the next hot water supply. The ignition condition setting means includes a heat retention control means for controlling burner combustion, and an ignition condition setting means for setting an air-fuel ratio when the burner is ignited. A mode and a silent ignition mode in which the air-fuel ratio at the time of ignition is set higher than this mode, wherein the heat retention control means sets the silent mode to the silent mode when the burner is ignited without water flow. A combustion device characterized by the following. 3. The ignition condition setting means, when misfire occurs in the silent ignition mode, determines the air-fuel ratio at the next ignition in the silent ignition mode from the current air-fuel ratio at which the misfire occurred. 3. The combustion device according to claim 1, wherein the combustion device is lowered. 4. The ignition condition setting means determines the air-fuel ratio in the next silent ignition mode when misfire occurs in the silent ignition mode, and determines the air-fuel ratio in the normal ignition mode. 3. The method according to claim 1, wherein the lower limit is set.
Or the combustion device according to 3. 5. A silent initial air-fuel ratio storage means for storing an initial value of an air-fuel ratio when ignition is performed in the silent ignition mode, and stores the initial value of the air-fuel ratio stored in the silent air-fuel ratio in the silent ignition mode. The combustion device according to claim 3 or 4, wherein the value is updated with the value of the air-fuel ratio at the time of ignition by lowering. 6. An ignition control method for controlling an ignition condition of a combustion device having a burner and an ignition device, wherein a normal ignition mode is set as an ignition mode for igniting the burner and an air-fuel ratio at the time of ignition is set higher than the normal ignition mode. An ignition mode for igniting the burner, except when the burner is ignited immediately in response to an operation from an operator, wherein the ignition mode is set to the silent ignition mode.