JP2003042444A - Water heater - Google Patents

Abstract

(57) [Problem] To provide a water heater A capable of constantly maintaining a burner 1 in an optimum combustion state. A water heater (A) includes a burner (1) that is supplied with a gas (15) through a gas pipe (14) provided with a flow control valve (13) and burns, and a blower (1) that supplies combustion air to the burner (1).
1, a heat exchanger 12 through which water 121 passes, and a gas pipe 14
Mass flow sensor 2 for detecting the flow rate of gas 15 passing through
1, a hot water temperature sensor 22 for detecting hot water temperature, a water supply amount sensor 23, a hot water temperature sensor 24, a hot water temperature setting device 26, and a target gas supply amount necessary for burning at a target combustion amount. , The flow control valve 1 so that the gas supply amount detected by the mass flow sensor 21 becomes the target gas supply amount.
A combustion controller 3 for controlling the opening degree of the fuel gas 3 and an air-fuel ratio sensor 25 for detecting the air-fuel ratio of the combustion exhaust gas. The air-fuel ratio detected by the air-fuel ratio sensor 25 is a predetermined air-fuel ratio at which the burner 1 performs stable combustion. Thus, the combustion controller 3 performs feedback control of the amount of electricity (= the amount of air blow) of the blower 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water heater such as a household water heater and a hot water heater.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG.
01, a burner 105 that burns when gas 104 is supplied through a gas pipe 103 provided with a flow rate control valve 102, a blower 106 that supplies combustion air to the burner 105, and an exhaust port 107. Combustion cylinder 10 connected
Heat exchanger 109, which is arranged on the upper part of 1, through which water 108 passes
Based on the outlet temperature sensor 110 for detecting the outlet temperature of the outlet side of the heat exchanger 109, the flame temperature sensor 111 for detecting the flame temperature of the burner 105, and the sensor outputs of the outlet temperature sensor 110 and the flame temperature sensor 111. The combustion controller 112 determines the combustion state, and the combustion controller 112 maintains the opening temperature of the flow rate adjusting valve 102 and the rotation speed of the blower 106 so that the outlet temperature is maintained at the target outlet temperature and the flame temperature becomes a predetermined temperature. There is known a water heater 100 that controls

[0003]

The above-mentioned conventional water heater 10
0 has the following problems. -It takes time to judge the result of increasing or decreasing the combustion air supplied to the burner 105. For example, when the rotation speed of the blower 106 is once increased from the initial value by a predetermined value to increase the combustion air amount, the combustion controller 112 is based on the output of each sensor.
Determines whether the combustion state is improved (it takes time), and if the combustion state is not improved, the blower 10
Control is performed to reduce the combustion air amount by decreasing the rotation speed of 6 from the initial value by a predetermined value. Therefore, CO and the like are continuously emitted from the exhaust port 107 until the combustion state is improved.

When the air-fuel ratio shifts due to secular change or disturbance (decrease in wind or oxygen concentration, etc.), the combustion state deteriorates.・ Misfire judgment and ignition judgment cannot be performed accurately.

When constructing a water heater, since the length of the exhaust duct is different, it is necessary to strictly determine the standard of the exhaust pipe to be attached in order to eliminate the difference in ventilation resistance.

An object of the present invention is to provide a water heater capable of maintaining the burner in an optimum combustion state at all times.

[0007]

[Means for Solving the Problems] [Claim 1] A water heater is provided in a combustion cylinder, and a burner is provided to burn gas fuel supplied through a gas fuel supply passage provided with a flow rate adjusting valve. A blower that supplies combustion air to the burner, a heat exchanger that is arranged above the combustion cylinder that is connected to the exhaust port, and through which water passes, and a hot water temperature sensor that detects the hot water temperature at the outlet side of this heat exchanger. A flame temperature sensor for detecting the flame temperature in the combustion cylinder, an air-fuel ratio sensor installed in the combustion exhaust gas passage for detecting the air-fuel ratio of the combustion exhaust gas, and a combustion controller.

The combustion controller determines the combustion state of the burner based on the outputs of the hot water temperature sensor and the flame temperature sensor so that the hot water temperature is maintained at the target hot water temperature and the flame temperature becomes a predetermined temperature. , Controls the opening of the flow rate adjustment valve and the blow rate of the blower. Then, when the combustion controller detects that the air-fuel ratio detected by the air-fuel ratio sensor is out of the predetermined air-fuel ratio at which the burner stably burns, while maintaining the opening of the flow rate adjusting valve at that time,
The air flow rate of the blower is controlled so that the air-fuel ratio becomes a predetermined air-fuel ratio.

Thus, in the water heater, the burner is always maintained in the optimum combustion state. Also, even if the ventilation resistance of the exhaust duct is different due to the difference in the length of the exhaust duct, the combustion controller controls the amount of air blown by the blower to autonomously control the air-fuel ratio to the predetermined air-fuel ratio. Therefore, it is not necessary to strictly determine the standard of the exhaust pipe to be installed when constructing the water heater.

[Claim 2] The water heater is arranged in the combustion cylinder, burner is burned by the gas fuel is supplied through a gas fuel supply passage provided with a flow rate adjusting valve, and combustion air for the burner. A heat exchanger for passing water, a gas fuel flow rate sensor for detecting the flow rate of the gaseous fuel passing through the gaseous fuel supply passage, Hot water temperature sensor that detects the hot water temperature at the outlet side of the exchanger, water supply amount sensor that detects the amount of water flowing in the heat exchanger, hot water temperature sensor that detects the hot water temperature at the heat exchanger inlet, and hot water temperature A hot water outlet temperature setting device for setting the above, an air-fuel ratio sensor installed in the combustion exhaust gas flow passage for detecting the air-fuel ratio of the combustion exhaust gas, and a combustion controller.

The combustion controller calculates a target combustion amount at which the outlet heated water temperature reaches the target outlet heated water temperature based on the water supply amount, the outlet heated water temperature, and the water inlet temperature detected by the respective sensors, and burns at this target combustion amount. Determine the required target gaseous fuel supply. Then, the combustion controller controls the flow rate adjusting valve so that the gas fuel supply amount detected by the gas fuel flow rate sensor becomes the target gas fuel supply amount required to burn at the target combustion amount at which the tapping temperature becomes the target tapping temperature. Control the opening of. Furthermore,
The combustion controller feedback-controls the amount of air blown by the blower so that the air-fuel ratio detected by the air-fuel ratio sensor becomes a predetermined air-fuel ratio at which the burner stably burns.

As a result, the hot water heater can always maintain the burner in an optimal combustion state in a state where the hot water discharger is burned at the target amount of combustion to reach the target hot water discharge temperature.

[Claim 3] The water heater is arranged in the combustion cylinder, burner is burned by the gaseous fuel is supplied through a gaseous fuel supply passage provided with a flow rate adjusting valve, and the burner is provided with combustion air. A heat exchanger that is arranged at the upper part of the combustion cylinder that is connected to the blower that supplies the exhaust port, through which water passes, an air flow rate sensor that detects the flow rate of the combustion air that is supplied to the burner, and a heat exchanger A hot water temperature sensor that detects the hot water temperature at the outlet side, a water supply amount sensor that detects the amount of water flowing in the heat exchanger, a hot water temperature sensor that detects the hot water temperature at the heat exchanger inlet, and a hot water temperature setting A hot water outlet temperature setting device, an air-fuel ratio sensor installed in the combustion exhaust gas passage for detecting the air-fuel ratio of the combustion exhaust gas, and a combustion controller.

The combustion controller calculates a target combustion amount at which the outlet water temperature reaches the target outlet temperature based on the water supply amount, the outlet water temperature, and the inlet water temperature detected by each sensor, and when stable combustion is performed at this target combustion amount. Calculate the required air volume required for.

The combustion controller supplies the blower so that the combustion air supply amount detected by the air flow rate sensor becomes the necessary air amount required for stable combustion at the target combustion amount at which the discharge hot water temperature reaches the target discharge hot water temperature. Control the air flow rate of. Further, the combustion controller feedback-controls the opening of the flow rate adjusting valve so that the air-fuel ratio detected by the air-fuel ratio sensor becomes a predetermined air-fuel ratio at which the burner stably burns.

Since the water heater has a structure in which the opening of the flow rate adjusting valve is feedback-controlled to control the flow rate of the gaseous fuel so that the burner has a predetermined air-fuel ratio for stable combustion, the water heater is excellent in responsiveness and the burner It is possible to maintain an optimum combustion state at all times.

[Claim 4] The water heater is arranged in the combustion cylinder, burner is burned by the gas fuel is supplied through a gas fuel supply passage provided with a flow rate adjusting valve, and the burner is provided with combustion air. A heat exchanger through which water passes, a gas fuel flow rate sensor that detects the flow rate of the gaseous fuel that passes through the gaseous fuel supply passage, and a burner that is arranged above the combustion cylinder to which the exhaust port is connected. An air flow rate sensor for detecting the flow rate of combustion air supplied to the heat exchanger, a hot water temperature sensor for detecting the hot water temperature at the outlet side of the heat exchanger, a water supply amount sensor for detecting the amount of water flowing in the heat exchanger, and An inlet water temperature sensor that detects the inlet water temperature at the inlet of the exchanger, an outlet hot water temperature setting device for setting the outlet hot water temperature, and is installed in the combustion exhaust gas flow path.
An air-fuel ratio sensor for detecting the air-fuel ratio of the combustion exhaust gas and a combustion controller are provided.

The combustion controller calculates a target combustion amount at which the outlet water temperature reaches the target outlet temperature based on the water supply amount, the outlet water temperature, and the inlet water temperature detected by the respective sensors, and burns at this target combustion amount. Determine the required target gaseous fuel supply,
The required air amount required for stable combustion with this target combustion amount is calculated.

Then, the opening of the flow rate adjusting valve is controlled so that the gas fuel supply amount detected by the gas fuel flow rate sensor becomes the target gas fuel supply amount, and at the same time the combustion amount detected by the air flow rate sensor is controlled. The air flow rate of the blower is controlled so that the air supply rate becomes the required air volume. Furthermore,
The combustion controller feedback-controls the opening of the flow rate adjusting valve and the blown amount of the blower so that the air-fuel ratio detected by the air-fuel ratio sensor becomes a predetermined air-fuel ratio at which the burner stably burns. Therefore, the water heater can keep the burner in an optimum combustion state at all times with good responsiveness while maintaining the hot water outlet temperature at the target hot water temperature.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION A water heater A (corresponding to claim 2) according to a first embodiment of the present invention will be described with reference to FIG. The water heater A includes a burner 1, a blower 11, a heat exchanger 12 through which water 121 passes, a mass flow rate sensor 21 (gas fuel flow rate sensor), a hot water temperature sensor 22, a water supply amount sensor 23,
An inlet water temperature sensor 24, an air-fuel ratio sensor 25, an outlet hot water temperature setting device 26, and a combustion controller 3 are provided.

The burner 1 is arranged below the combustion cylinder 10,
The gas 15 is supplied and burned via a gas pipe 14 (gas fuel supply path) provided with a flow rate adjusting valve 13. And
The spark plug 17 is arranged so as to face above the burner 1. Further, a flame temperature sensor 18 for detecting the flame temperature and used for assisting the misfire determination is arranged so as to face the burner 1.

The blower 11 is provided at the lower end of the combustion cylinder 10 and supplies combustion air to the burner 1. Heat exchanger 12
Is provided above the combustion cylinder 10 to which the exhaust port 16 is connected, and raises the temperature of the water 121 passing by the heat of the combustion flame.

The mass flow rate sensor 21 (gas fuel flow rate sensor) is provided in the gas pipe 14 and detects the flow rate of the gas 15 passing through the gas pipe 14.

The hot water temperature sensor 22 is provided in the hot water supply pipe 122 on the outlet side of the heat exchanger 12, and detects the temperature of hot water flowing on the outlet side of the heat exchanger 12. Water supply sensor 23
Is installed in the water supply pipe 123 and detects the amount of water flowing into the heat exchanger 12.

The incoming water temperature sensor 24 is provided in the water supply pipe 123 and detects the temperature of the water flowing into the heat exchanger 12. The air-fuel ratio sensor 25 is installed in the exhaust port 16,
The air-fuel ratio of combustion exhaust gas is detected. Hot water temperature setting device 26
Is for setting the tap water temperature.

The combustion controller 3 of the water heater A operates as follows. The combustion controller 3 first sets the outlet heated water temperature to a target outlet heated water temperature based on the amount of water supplied detected by the water supply amount sensor 23, the outlet water temperature detected by the outlet water temperature sensor 22, and the inlet water temperature detected by the inlet water temperature sensor 24. Calculate the target combustion amount.

Next, the target gas supply amount required to burn at this target combustion amount is determined. And the combustion controller 3
Is the gas pipe 14 detected by the mass flow sensor 21.
The opening degree of the flow rate adjusting valve 13 is controlled so that the flow rate of the gas 15 passing through is equal to the target gas supply amount.

Further, the air-fuel ratio detected by the air-fuel ratio sensor 25 is set to a predetermined air-fuel ratio (for example, 1.
2) (see FIG. 9), the rotation speed of the blower 11 (=
The combustion controller 3 feedback-controls the blowing amount).

The water heater A of this embodiment has the following advantages. The water heater A controls the opening degree of the flow rate adjusting valve 13 so that the flow rate of the gas 15 passing through the gas pipe 14 detected by the mass flow rate sensor 21 becomes the target gas supply amount, and the air-fuel ratio sensor 25 The combustion controller 3 feedback-controls the number of revolutions of the blower 11 (= blowing amount) so that the detected air-fuel ratio becomes a predetermined air-fuel ratio (for example, 1.2) with which the burner 1 stably burns.

Therefore, the burner 1 can always be maintained in an optimum combustion state in a state where the burner 1 is burned at a target combustion amount to reach the target hot water temperature, and the exhaust port 16 for the unburned gas such as CO is discharged. Can be prevented from being released. Furthermore, the outlet heated water temperature can be accurately maintained at the target outlet heated water temperature. Also,
Even if the optimal combustion state is deviated due to secular change or disturbance (such as a decrease in wind or oxygen concentration), the optimal combustion state can be immediately restored.

Further, even if the ventilation resistance of the exhaust duct is different due to the difference in the length of the exhaust duct, the combustion controller 3 controls the rotation speed (= blown air amount) of the blower 11 so that the air-fuel ratio is increased. Is controlled autonomously so as to have a predetermined air-fuel ratio (for example, 1.2), it is not necessary to strictly determine the standard of the exhaust pipe to be attached when the water heater A is installed.

Next, a water heater B (corresponding to claim 3) according to a second embodiment of the present invention will be described with reference to FIG. The water heater B of this embodiment differs from the water heater A in the following points.

In the water heater B of this embodiment, the mass flow rate sensor 21 is not provided, but instead, the mass flow rate sensor 19 (air flow rate sensor) for detecting the flow rate of the combustion air supplied to the burner 1 is provided. It is arranged inside.

The combustion controller 3 of the water heater B operates as follows. The combustion controller 3 first sets the outlet heated water temperature to a target outlet heated water temperature based on the amount of water supplied detected by the water supply amount sensor 23, the outlet water temperature detected by the outlet water temperature sensor 22, and the inlet water temperature detected by the inlet water temperature sensor 24. Calculate the target combustion amount.

Next, the combustion controller 3 calculates the required air amount required for stable combustion at this target combustion amount. Then, the combustion controller 3 controls the number of revolutions of the blower 11 (= blowing amount) so that the air supply amount detected by the mass flow rate sensor 19 becomes the required air amount.

Further, the air-fuel ratio detected by the air-fuel ratio sensor 25 is set to a predetermined air-fuel ratio (for example, 1.
2) (see FIG. 9), the combustion controller 3 feedback-controls the opening of the flow rate adjusting valve 13.

The water heater B of this embodiment has the following advantages. In the water heater B, the number of rotations of the blower 11 (= air flow rate) so that the air flow rate in the combustion air passage detected by the mass flow rate sensor 19 (air flow rate sensor) becomes the required air amount.
Is controlled by the combustion controller 3, and the air-fuel ratio sensor 25
The combustion controller 3 feedback-controls the opening of the flow rate adjusting valve 13 so that the air-fuel ratio detected by the burner 1 becomes a predetermined air-fuel ratio at which the burner 1 stably burns (for example, 1.2).

For this reason, the burner 1 can always be maintained in an optimum combustion state in a state in which the burner 1 is burned at a target combustion amount that makes it the target hot water temperature, and the exhaust port 16 for unburned gas such as CO is discharged. Can be prevented from being released.

Further, even if the optimum combustion state is deviated due to secular change or disturbance (decrease in wind or oxygen concentration, etc.), the optimum combustion state can be immediately restored. The water heater B has a configuration in which the combustion controller 3 feedback-controls the opening of the flow rate adjusting valve 13 so that the air-fuel ratio detected by the air-fuel ratio sensor 25 becomes a predetermined air-fuel ratio. The responsiveness is better than that of the water heater A in which the combustion controller 3 feedback-controls the number (= amount of blown air) to control to a predetermined air-fuel ratio,
Even if the optimum combustion state is deviated, the optimum combustion state can be immediately restored.

Further, even if the ventilation resistance of the exhaust duct is different due to the difference in the length of the exhaust duct, the combustion controller 3 controls the opening degree of the flow rate adjusting valve 13 so that the air-fuel ratio becomes a predetermined air-fuel ratio. Since the autonomous control is performed so that the fuel ratio becomes 1.2 (for example, 1.2), when constructing the water heater B, it is not necessary to strictly determine the standard of the exhaust pipe to be attached.

Next, a water heater C (corresponding to claim 4) according to a third embodiment of the present invention will be described with reference to FIG. The water heater C of this embodiment is different from the water heater A in the following points.

In the water heater C of this embodiment, a mass flow sensor 21 for detecting the flow rate of the gas 15 passing through the gas pipe 14 is provided, and a mass flow sensor 19 for detecting the flow rate of the combustion air supplied to the burner 1. The (air flow rate sensor) is arranged in the combustion air passage. The mass flow rate sensor 21 (gas fuel flow rate sensor) is provided in the gas pipe 14 and
The flow rate of the gas 15 passing through is detected.

The combustion controller 3 of the water heater C operates as follows. The combustion controller 3 first sets the outlet heated water temperature to a target outlet heated water temperature based on the amount of water supplied detected by the water supply amount sensor 23, the outlet water temperature detected by the outlet water temperature sensor 22, and the inlet water temperature detected by the inlet water temperature sensor 24. Calculate the target combustion amount. Next, the combustion controller 3 determines the target gas supply amount necessary for combustion with this target combustion amount, and calculates the necessary air amount required for stable combustion with this target combustion amount.

The combustion controller 3 controls the opening of the flow rate adjusting valve 13 so that the gas supply amount detected by the mass flow rate sensor 21 (gas fuel flow rate sensor) becomes the target gas supply amount, and the mass flow rate sensor 19 is also provided. The blower 11 so that the air flow rate detected by the (air flow rate sensor) becomes the required air volume.
Control the number of rotations (= blown air volume).

Further, the air-fuel ratio detected by the air-fuel ratio sensor 25 is set to a predetermined air-fuel ratio (for example, 1.
2) (see FIG. 9), the combustion controller 3 feedback-controls the opening degree of the flow rate adjustment valve 13 and the rotation speed (= air flow rate) of the blower 11.

The water heater C of this embodiment has the following advantages. In the water heater C, the opening of the flow rate adjusting valve 13 and the blower 11 are adjusted so that the flow rate of the gas 15 passing through the gas pipe 14 becomes the target gas supply amount and the air supply amount to the burner 1 becomes the required air amount. The combustion speed is controlled by the combustion controller 3 and the air-fuel ratio detected by the air-fuel ratio sensor 25 is set to a predetermined air-fuel ratio (for example, 1.
2), the combustion controller 3 feedback-controls the opening degree of the flow rate adjusting valve 13 and the rotation speed (= air blowing amount) of the blower 11.

For this reason, the burner 1 can always be maintained in an optimum combustion state in a state where the burner 1 is burned at a target combustion amount so that the discharge hot water temperature reaches the target hot water discharge temperature, and the exhaust port 16 for the unburned gas such as CO is discharged. Can be prevented from being released.

Further, even if the optimum combustion state is deviated due to secular change or disturbance (decrease in wind or oxygen concentration), the optimum combustion state can be immediately returned. The water heater C has the flow rate adjusting valve 13 so that the air-fuel ratio detected by the air-fuel ratio sensor 25 becomes a predetermined air-fuel ratio (for example, 1.2) (see FIG. 9).
Since the combustion controller 3 feedback-controls the opening degree of the blower 11 and the number of revolutions of the blower 11 (= the amount of blown air), the outlet heated water temperature is accurately maintained at the target outlet heated water temperature even if the combustion state deviates from the optimum combustion state. In this state, the optimum combustion state can be immediately restored.

Further, even if the ventilation resistance of the exhaust duct differs due to the difference in the length of the exhaust duct, the opening degree of the flow rate adjusting valve 13 and the rotation speed (= blowing amount) of the blower 11 are controlled by combustion. Since the water heater 3 controls and the air-fuel ratio is autonomously controlled so that the air-fuel ratio becomes a predetermined air-fuel ratio (for example, 1.2), it is not necessary to strictly determine the standard of the exhaust pipe to be attached when the water heater C is installed.

When the air-fuel ratio is being controlled by the air-fuel ratio sensor 25, if the flow rate adjustment valve 13 is out of the set opening range or if the rotation speed of the blower 11 (= air flow rate) is out of the set range. Please send it for repair! It is also possible to give a warning display indicating that ". The operation may be continued or the breakdown may be stopped.

Next, the water heaters D, E and F (corresponding to claim 1) according to the fourth, fifth and sixth embodiments of the present invention are shown in FIG.
This will be described with reference to FIGS. 5 and 6. The water heater D of this embodiment,
E and F are different from the water heater A in the following points.

In the water heaters D, E, F of this embodiment, the mass flow sensor 21 is not provided. In the water heater D, an air-fuel ratio sensor 25 is installed inside the exhaust port 16, and the air-fuel ratio sensor 25 detects the air-fuel ratio of the combustion exhaust gas.

In the water heater E, an air-fuel ratio sensor 25 is installed inside the combustion cylinder 10 on the downstream side of the heat exchanger 12, and the air-fuel ratio sensor 25 detects the air-fuel ratio of the combustion exhaust gas. In the water heater F, an air-fuel ratio sensor 25 is installed inside the combustion cylinder 10 on the upstream side of the heat exchanger 12, and the air-fuel ratio sensor 25 detects the air-fuel ratio of the combustion exhaust gas.

The combustion controller 3 determines the combustion state of the burner 1 based on the outputs of the hot water temperature sensor 22 and the flame temperature sensor 18, and maintains the hot water temperature at the target hot water temperature set by the hot water temperature setting device 26. In addition, the opening degree of the flow rate adjusting valve 13 and the energization amount (= blowing amount) to the blower 11 are controlled so that the flame temperature becomes a predetermined temperature.

Then, it is confirmed that the air-fuel ratio detected by the air-fuel ratio sensor 25 is out of the upper and lower limits (for example, 1.2 ± 0.05) of the predetermined air-fuel ratio at which the burner 1 stably burns. 3 detects the blower 11 so that the air-fuel ratio becomes a predetermined air-fuel ratio (for example, 1.2) with the current opening of the flow rate adjusting valve 13 fixed (see FIG. 9).
Feedback control is performed on the amount of electricity supplied to the unit (= blowing amount).

The water heaters D, E, F of this embodiment have the following advantages. Hot water heaters D, E, and F are hot water temperature setting devices 26
The combustion controller 3 controls the opening degree of the flow rate adjusting valve 13 and the amount of electricity supplied to the blower 11 (= the amount of blown air) so that the discharged hot water temperature is maintained at the target hot water discharge temperature set in step 5 and the flame temperature reaches a predetermined temperature. In addition, the air-fuel ratio detected by the air-fuel ratio sensor 25 is the upper limit of the predetermined air-fuel ratio at which the burner 1 stably burns.
When it is detected that it is out of the lower limit (for example, 1.2 ± 0.05), the air-fuel ratio becomes the predetermined air-fuel ratio (for example, 1.2) with the current opening of the flow rate adjusting valve 13 fixed. As described above, the amount of electricity to the blower 11 (= the amount of blown air) is feedback-controlled.

Therefore, the burner 1 can always be maintained in an optimal combustion state in a state where the burner 1 is burned at a target combustion amount that makes the target hot water temperature, and the exhaust port 16 for the unburned gas such as CO is discharged. Can be prevented from being released.

Further, even if the optimum combustion state is deviated due to secular change or disturbance (such as a decrease in wind or oxygen concentration), the optimum combustion state can be immediately restored. In addition, water heaters D, E,
F is a state in which the current opening of the flow rate control valve 13 is fixed, and feedback control is performed on the amount of electricity supplied to the blower 11 (= blowing amount) so that the air-fuel ratio becomes a predetermined air-fuel ratio (for example, 1.2). It is a composition. Therefore, the outlet heated water temperature can be accurately maintained at the target outlet heated water temperature.

Further, even if the ventilation resistance of the exhaust duct is different due to the difference in the length of the exhaust duct, the combustion controller 3 feedback-controls the energization amount (= blowing amount) to the blower 11, Since the air-fuel ratio is autonomously controlled so that the air-fuel ratio becomes a predetermined air-fuel ratio (for example, 1.2), it is not necessary to strictly determine the standard of the exhaust pipe to be attached when the water heaters D, E, and F are installed.

The present invention includes the following embodiments in addition to the above embodiments. a. In the water heaters A to F, a characteristic curve that has been examined in advance from the non-ignition determination region (fuel rich) of the air-fuel ratio at the start of the hot water supply operation to the stable combustion region (FIG. 10)
Ignition determination may be performed based on (see). Further, based on the characteristic curve of the air-fuel ratio from stable combustion to incomplete combustion / misfire state (fuel rich), which was examined in advance (see FIG. 11), even if the air-fuel ratio control is performed, it shifts to the fuel rich region. If it does, it may be determined that it is in a misfire or incomplete combustion state. If the determination is performed based on the characteristic curve of the air-fuel ratio detected by the air-fuel ratio sensor 25, the ignition sensor (flame temperature sensor 18 etc.) and the CO sensor are unnecessary.

B. In the water heaters A to F, an expensive air-fuel ratio sensor (shown in FIG. 7) having a structure in which the heater 251 heats the sensor portion to a constant temperature may be used as the air-fuel ratio sensor 25, but the water heater has high accuracy. Since the detection of the air-fuel ratio is not required, it is possible to use an inexpensive air-fuel ratio sensor (shown in FIG. 8) having a structure in which the temperature sensor 252 is mounted and the map of the sensor output according to the temperature is adapted.

C. As the gas fuel flow rate sensor and the air flow rate sensor, a volume flow meter may be used instead of the mass flow meter.

D. In the water heaters A to F, the air-fuel ratio control by the air-fuel ratio sensor is preferably performed after a predetermined time has elapsed from ignition or after confirming once that stable combustion has been performed by another sensor.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a water heater according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a water heater according to a second embodiment of the present invention.

FIG. 3 is an explanatory diagram of a water heater according to a third embodiment of the present invention.

FIG. 4 is an explanatory view of a water heater according to a fourth embodiment of the present invention.

FIG. 5 is an explanatory view of a water heater according to a fifth embodiment of the present invention.

FIG. 6 is an explanatory view of a water heater according to a sixth embodiment of the present invention.

7A and 7B are explanatory views of an air-fuel ratio sensor having a structure in which a heater heats a sensor unit to a constant temperature.

8A and 8B are explanatory diagrams of an air-fuel ratio sensor having a structure in which a temperature sensor is mounted and a map of sensor output according to temperature is adapted.

FIG. 9 is an explanatory diagram showing how deterioration of a combustion state due to secular change or disturbance is corrected.

FIG. 10 is a graph for explaining a method of making an ignition determination based on a transition of an air-fuel ratio.

FIG. 11 is a graph for explaining a method of performing incomplete combustion / misfire determination based on a change in air-fuel ratio.

FIG. 12 is an explanatory diagram of a water heater according to a conventional technique.

[Explanation of symbols]

A, B, C, D, E, F water heater 1 burner 3 Combustion controller 10 burning body 11 blower 12 heat exchanger 13 Flow rate adjustment valve 14 gas pipe (gas fuel supply path) 15 gas (gas fuel) 16 exhaust port 18 Flame temperature sensor 19 Mass flow sensor (air flow sensor) 21 Mass flow sensor (gaseous fuel flow sensor) 22 Hot water temperature sensor 23 Water supply sensor 24 Inlet temperature sensor 25 Air-fuel ratio sensor 26 Hot water temperature setting device

Claims (4)

[Claims] 1. A burner which is disposed in a combustion cylinder and burns when a gaseous fuel is supplied through a gaseous fuel supply passage provided with a flow rate adjusting valve, a blower which supplies combustion air to the burner, and an exhaust port. A heat exchanger that is arranged above the combustion cylinder through which water passes, a hot water temperature sensor that detects the hot water temperature at the outlet side of the heat exchanger, and a flame temperature that detects the flame temperature inside the combustion cylinder. The burner combustion state is determined based on the output of the sensor, the hot water temperature sensor, and the flame temperature sensor, and the flow rate is adjusted so that the hot water temperature is maintained at the target hot water temperature and the flame temperature becomes the predetermined temperature. In a water heater including a combustion controller that controls the opening of a valve and the amount of air blown by the blower, an air-fuel ratio sensor that detects the air-fuel ratio of combustion exhaust gas is installed in the combustion exhaust gas flow path, and the air-fuel ratio sensor detects the air-fuel ratio sensor. When the combustion controller detects that the air-fuel ratio is deviated from the predetermined air-fuel ratio at which the burner stably burns, the air-fuel ratio becomes the predetermined air-fuel ratio while maintaining the opening of the flow rate adjusting valve at that time. A water heater characterized by controlling the amount of air blown by the blower. 2. A burner which is arranged in the combustion cylinder and burns when a gaseous fuel is supplied through a gaseous fuel supply passage provided with a flow rate adjusting valve, a blower which supplies combustion air to the burner, and an exhaust port. A heat exchanger that is arranged in the upper part of the combustion cylinder through which water passes, a gas fuel flow sensor that detects the flow rate of the gaseous fuel that passes through the gaseous fuel supply path, and an outlet side of the heat exchanger Hot water temperature sensor to detect the hot water temperature of the heat exchanger, water supply amount sensor to detect the amount of water flowing in the heat exchanger, water temperature sensor to detect the hot water temperature at the inlet of the heat exchanger, and to set the hot water temperature. It is necessary to calculate the target combustion amount at which the outlet hot water temperature reaches the target hot water outlet temperature based on the amount of water supplied, hot water outlet temperature, and incoming water temperature detected by each sensor Target gas fuel supply And a combustion controller that controls the opening degree of the flow rate adjusting valve so that the gas fuel supply amount detected by the gas fuel flow rate sensor becomes the target gas fuel supply amount. An air-fuel ratio sensor for detecting a fuel ratio is installed in the combustion exhaust gas flow path, and the air-fuel ratio detected by the air-fuel ratio sensor is set to a predetermined air-fuel ratio at which the burner stably burns so that the air blow rate of the blower is A water heater characterized by feedback control by a combustion controller. 3. A burner, which is arranged in the combustion cylinder and burns when a gaseous fuel is supplied through a gaseous fuel supply path provided with a flow rate adjusting valve, a blower for supplying combustion air to the burner, and an exhaust port. Is arranged in the upper part of the combustion cylinder, the heat exchanger through which water passes, an air flow rate sensor for detecting the flow rate of the combustion air supplied to the burner, and the hot water temperature at the outlet side of the heat exchanger. Hot water temperature sensor to detect, water supply amount sensor to detect the amount of water flowing in the heat exchanger, water temperature sensor to detect the water temperature at the heat exchanger inlet, hot water temperature setter to set the hot water temperature Based on the supplied water amount, hot water temperature, and hot water temperature detected by each sensor, the target combustion amount at which the hot water temperature reaches the target hot water temperature is calculated, and the required air amount required for stable combustion at this target combustion amount. Calculate the air flow rate In a water heater including a combustion controller that controls the air flow rate of the blower so that the combustion air supply rate detected by the sensor becomes the required air quantity, an air-fuel ratio sensor that detects the air-fuel ratio of the combustion exhaust gas is used as the combustion exhaust gas. The combustion controller feedback-controls the opening of the flow rate adjusting valve so that the air-fuel ratio installed in the flow path becomes a predetermined air-fuel ratio at which the burner stably burns, the air-fuel ratio detected by the air-fuel ratio sensor. Water heater characterized by. 4. A burner which is arranged in the combustion cylinder and burns when a gaseous fuel is supplied through a gaseous fuel supply passage provided with a flow rate adjusting valve, a blower which supplies combustion air to the burner, and an exhaust port. A heat exchanger that is arranged in the upper part of the combustion cylinder through which water passes, a gas fuel flow rate sensor that detects the flow rate of the gaseous fuel that passes through the gaseous fuel supply passage, and a combustion that supplies the burner. An air flow rate sensor for detecting the air flow rate, a hot water temperature sensor for detecting the hot water temperature at the outlet side of the heat exchanger, a water supply amount sensor for detecting the amount of water flowing in the heat exchanger, and a heat exchanger inlet A hot water temperature sensor that detects the hot water temperature, a hot water temperature setting device that sets the hot water temperature, and a target that the hot water temperature becomes the target hot water temperature based on the amount of hot water, the hot water temperature, and the hot water temperature detected by each sensor. Calculate the amount of combustion Out, determines the target gas fuel supply amount necessary to burn at this target combustion amount, calculates the necessary air amount required for stable combustion at this target combustion amount, and is detected by the gas fuel flow rate sensor While controlling the opening of the flow rate adjusting valve so that the gaseous fuel supply amount becomes the target gaseous fuel supply amount, the blower of the blower is adjusted so that the combustion air supply amount detected by the air flow rate sensor becomes the required air amount. In a water heater including a combustion controller that controls the air flow rate, an air-fuel ratio sensor that detects the air-fuel ratio of the combustion exhaust gas is installed in the combustion exhaust gas flow passage, and the air-fuel ratio detected by the air-fuel ratio sensor is the burner. The water heater, wherein the combustion controller feedback-controls the opening of the flow rate adjusting valve and the amount of air blown by the blower so that a predetermined air-fuel ratio for stable combustion can be obtained.