JP6815225B2 - Combustion device - Google Patents

Description

The present invention relates to a combustion device including a combustion fan that supplies combustion air to a burner arranged in a combustion chamber.

In a combustion device equipped with a combustion fan that supplies combustion air to a burner arranged in a combustion chamber, such as a combustion device mounted on a gas water heater, the rotation speed (rotation speed) of the combustion fan is basically basically. It is controlled to the target rotation speed determined according to the target heat amount (target combustion amount) of the burner.

In this type of combustion device, the air supply / exhaust passage (air supply passage or exhaust passage) communicating with the combustion chamber is partially clogged (clogging due to foreign matter such as dust), or the air supply / exhaust passage is connected from the outside (atmospheric side). Due to the influence of outside wind such as the acting gust, the actual air volume of the combustion fan (and thus the actual supply amount of combustion air to the burner) decreases even if the rotation speed of the combustion fan is constant. Occurs.

In addition, the internal pressure of the combustion chamber may increase due to the influence of gusts acting on the air supply / exhaust passage. In this case, especially when the amount of heat of the burner is relatively small (a state close to the minimum value), a phenomenon that the flow rate of the fuel ejected from the burner decreases may occur.

For this reason, conventionally, as seen in Patent Document 1, for example, a proportional valve that detects the degree of blockage of the air supply / exhaust path and defines the rotation speed of the combustion fan and the amount of fuel supplied to the burner according to the degree of blockage. A technique for variably controlling the current is known.

In the present specification, the degree of blockage of the air supply / exhaust passage is the degree of obstructing the flow of airflow in the air supply / exhaust passage by the combustion fan (flow of airflow from the air supply passage side to the exhaust passage side via the combustion chamber). Means. In this case, the degree of blockage changes not only by the degree of clogging of the air supply / exhaust passage but also by the influence of the outside wind acting on the air supply / exhaust passage.

Japanese Unexamined Patent Publication No. 2008-256271

By the way, the area of combination of the calorific value (combustion amount) of the burner that can perform the combustion operation of the burner satisfactorily without causing misfire and the air volume (combustion air supply amount) of the combustion fan (burner combustion operation). The region that can be performed with a suitable air-fuel ratio. Hereinafter, it may be referred to as an appropriate combustible region) tends to become narrower as the amount of heat of the burner is smaller.

Further, in particular, when the burning operation of the burner is performed with the minimum amount of heat within the variable range of the amount of heat of the burner or a heat amount close to it, combustion is caused by the influence of an outside wind such as a gust of wind acting on the air supply / exhaust path. When the internal pressure of the chamber increases, the flow rate of fuel ejected from the burner tends to decrease. As a result, the actual amount of heat generated by the burning operation of the burner is further reduced, so that the appropriate combustible region is further narrowed.

Therefore, in such a situation, in response to the detection of an increase in the degree of blockage of the air supply / exhaust path due to a gust of wind or the like, the control as seen in Patent Document 1 (combustion fan rotation speed correction control or burner) When the correction control of the fuel supply amount to the burner is performed, the actual combustion state of the burner tends to deviate from the above-mentioned proper combustible region. As a result, misfire of the burner or poor combustion is likely to occur.

The present invention has been made in view of the above background, and a good combustion operation of the burner is performed even in a situation where an outside wind such as a gust of wind acts on the air supply / exhaust path during the combustion operation of the burner with a small amount of heat. It is an object of the present invention to provide a combustion device capable of providing a combustion device.

In order to achieve the above object, the combustion apparatus of the present invention provides a burner arranged in a combustion chamber, an air supply / exhaust passage communicating with the combustion chamber, and an air supply passage of the air supply / exhaust passages to the burner. A combustion fan that supplies combustion air through the burner, a fuel adjustment valve that adjusts the amount of fuel supplied to the burner, and a target calorific value of the burner can be variably set within a predetermined variable range during combustion operation of the burner. It is a combustion device provided with a combustion operation control unit that is set and controls the rotation speed of the combustion fan and the fuel adjustment valve according to the target calorific value.
A blockage detection unit that detects the blockage of the air supply / exhaust passage,
During the combustion operation of the burner, the higher the degree of blockage detected, the larger the lower limit of heat quantity, which is the lower limit of the variable range of the target heat quantity, so that the variable range of the target heat quantity is increased according to the degree of blockage. shall be the basic configuration in that it comprises a heat lower limit adjusting unit that adjusts a.

According to this, during the combustion operation of the burner in a situation where the target heat amount is set to the lower limit value of the heat amount or a heat amount close to the lower limit value, the degree of blockage is affected by the outside wind acting on the air supply / exhaust path. When the degree of blockage detected by the detection unit increases, the lower limit of the amount of heat increases, so that the combustion operation control unit is set to increase the target amount of heat as a result.

Therefore, when the degree of closure increases, the internal pressure of the combustion chamber increases and the flow rate of fuel ejected from the burner decreases (in other words, the actual amount of heat of the burner becomes smaller than the target amount of heat). Even if there is, the actual calorific value of the burner can be restored to a calorific value range in which the proper combustible region does not become too narrow. As a result, the burner can be burned so as not to cause misfire or poor combustion.

Therefore, according to the present invention, it is possible to perform good combustion operation of the burner even in a situation where an outside wind such as a gust acts on the air supply / exhaust path during the combustion operation of the burner with a small amount of heat. That is, it is possible to improve the wind resistance performance during the combustion operation of the burner with a small amount of heat.

In the first aspect of the present invention having the above basic configuration, the combustion operation control unit increases the rotation speed of the combustion fan corresponding to each value of the target heat quantity as the detected degree of blockage increases. It is configured to control the rotational speed.

Further , the combustion operation control unit and the calorific value lower limit adjusting unit increase the number of revolutions of the combustion fan and the calorific value lower limit, respectively, according to the detected increase in the degree of blockage during the combustion operation of the burner. After increasing the number of rotations of the combustion fan, at least in the initial stage immediately after the start of the increase control process, the lower limit of the amount of heat is made to reach a value corresponding to the degree of blockage after the increase. It is possible to realize the value earlier than reaching the value corresponding to the degree of blockage , and during the period in which the lower limit of heat quantity is increased, the rotation of the combustion fan is performed in parallel with the increase of the lower limit value of heat quantity. It is characterized in that it is configured to increase the number of revolutions of the combustion fan and the lower limit of the amount of heat, respectively, in an increasing pattern for increasing the number ( first invention).

In the first invention, "the initial stage immediately after the start of the increase control process" specifically means the rotation speed of the combustion fan and the lower limit of the amount of heat according to the detected increase in the degree of blockage. After starting the control process to increase each, the lower limit of the amount of heat increases to a value corresponding to the degree of blockage after the increase, and the rotation speed of the combustion fan increases to a value corresponding to the degree of blockage after the increase. It means the period on the starting side of a certain point in the middle of the period until both things are completed.

Further, the "increasing pattern" means a change pattern of the rotation speed of the combustion fan and the lower limit of the amount of heat, respectively, with time.

Here, when the target calorific value is set to or close to the calorific value lower limit value and the combustion operation of the burner is performed, the control process for increasing the rotation speed of the combustion fan and the calorific value lower limit value, respectively. At the start, the range of air volume of the combustion fan belonging to the proper combustible range is small. Therefore, in the initial stage immediately after the start of the increase control process, tentatively, the lower limit of the amount of heat is set to the degree of blockage after the increase, so that the rotation speed of the combustion fan reaches a value corresponding to the degree of blockage after the increase. In an increase pattern that can be realized earlier than reaching the corresponding value, if the number of revolutions of the combustion fan and the lower limit of the amount of heat are increased, respectively, the initial stage immediately after the start of the control process for the increase. The increase in the air volume of the combustion fan in the above is too large, and the actual air-fuel ratio state of the burner may deviate to the air-rich side from the air-fuel ratio in the proper combustion range, resulting in misfire of the burner or poor combustion. is there.

Therefore, in the first invention, the combustion operation control unit and the calorific value lower limit adjusting unit are configured as described above. According to this, since the increase in the lower limit of the amount of heat proceeds at an early stage, the target amount of heat immediately before the start of the control process for the increase is set to the lower limit of the amount of heat or a value close to the lower limit of the amount of heat, and the combustion operation of the burner is performed. If so, the proper combustible range is expanded at an early stage . Further, in the period for increasing the lower limit of the amount of heat, the rotation speed of the combustion fan increases in parallel with the increase of the lower limit of the amount of heat.

As a result, the number of rotations of the combustion fan and the said The control process for increasing each of the lower limit values of the calorific value can be executed so that the actual air-fuel ratio state of the burner does not deviate from the air-fuel ratio in the appropriate combustible range. As a result, a good burning state of the burner can be maintained.

Further, in the second aspect of the present invention having the above basic configuration , the combustion operation control unit determines the number of rotations of the combustion fan corresponding to each value of the target heat amount, the higher the detected degree of closure, the higher the degree of closure. It is configured to control to a higher rotation speed, and further , the combustion operation control unit and the calorific value lower limit adjusting unit respond to a decrease in the degree of blockage detected during the combustion operation of the burner. When the control process for reducing the number of revolutions of the combustion fan and the lower limit of the calorific value is executed, at least in the initial stage immediately after the start of the control process for the decrease, the number of revolutions of the combustion fan corresponds to the degree of closure after the decrease. It is possible to reach the value earlier than reaching the value corresponding to the degree of closure after the reduction of the lower limit of the amount of heat , and during the period in which the lower limit of the amount of heat is reduced, the said a decrease pattern in parallel with the decrease in the amount of heat the lower limit value to reduce the rotational speed of the combustion fan, is characterized in that it is configured to reduce each of said heat lower limit the rotational speed of the combustion fan ( Second invention).

In the second invention, "the initial stage immediately after the start of the reduction control process" specifically refers to the rotation speed of the combustion fan and the lower limit of the amount of heat according to the detected decrease in the degree of blockage. After starting the control process to reduce each, the lower limit of the amount of heat decreases to a value corresponding to the degree of blockage after the decrease, and the rotation speed of the combustion fan decreases to the value corresponding to the degree of blockage after the decrease. It means the period on the starting side of a certain point in the middle of the period until both things are completed.

Further, the "decrease pattern" means a change pattern over time in each decrease of the rotation speed of the combustion fan and the lower limit value of the amount of heat.

Here, at the start of the control process for reducing the rotation speed of the combustion fan and the lower limit of the calorific value, the air-fuel ratio state of the burner is usually the air-fuel ratio state on the air-rich side within the proper combustible range. .. Therefore, if the target calorific value immediately before the start of the reduction control process is limited to the calorific value lower limit value and the combustion operation of the burner is performed, in the initial stage immediately after the start of the reduction control process, tentatively. It is possible to reach the lower limit of the amount of heat to a value corresponding to the degree of blockage after the decrease, earlier than to reach the value corresponding to the degree of blockage after the decrease of the number of revolutions of the combustion fan. When the number of revolutions of the combustion fan and the lower limit of the calorific value are each reduced in the decrease pattern, the decrease in the calorific value of the burner at the initial stage immediately after the start of the control process of the decrease is too large, and the burner is actually empty. There is a risk that the fuel ratio state deviates to the air-rich side from the air-fuel ratio in the proper combustible range, resulting in misfire of the burner or poor combustion.

Therefore, in the second invention, the combustion operation control unit and the calorific value lower limit adjusting unit are configured as described above. According to this, since the decrease in the rotation speed of the combustion fan progresses at an early stage, the bias of the air-fuel ratio state of the burner toward the air-rich side is eliminated at an early stage . Further, in the period for reducing the lower limit of the amount of heat, the rotation speed of the combustion fan decreases in parallel with the decrease of the lower limit of the amount of heat.

As a result, the rotation speed of the combustion fan and the lower limit of the amount of heat are each corresponding to the decrease in the degree of closure in the state where the target amount of heat is limited to the lower limit of the amount of heat and the combustion operation of the burner is being performed. The control process for reducing the air-fuel ratio can be performed so that the actual air-fuel ratio state of the burner does not deviate from the air-fuel ratio in the proper combustible range. As a result, a good burning state of the burner can be maintained.

In the first and second inventions, the blockage detection unit may be configured to further have a function of detecting the blockage of the air supply / exhaust passage before ignition of the burner. In this case, when the degree of blockage detected before the ignition of the burner is equal to or higher than a predetermined value, the calorific value lower limit adjusting unit determines the degree of blockage detected before the ignition. It is preferable that the burner is configured to determine the lower limit of the amount of heat at the start of the combustion operation ( third invention).

According to this, when it is detected that the degree of blockage is relatively high (the degree of blockage is equal to or higher than the predetermined value) before the burner is ignited, the lower limit of the amount of heat is set to the degree of blockage. The burner combustion operation is started with the value set to a larger value than when it is low. That is, from the start of the burning operation of the burner, the burning operation of the burner is performed while the target heat amount is set in the range of the lower limit value of the amount of heat larger than the case where the degree of closure is low.

For this reason, even if an outside wind that causes the air supply / exhaust passage to have a relatively high degree of obstruction (a state in which the degree of obstruction is equal to or higher than a predetermined value) is continuously blown before the burner is ignited, misfire or combustion It is possible to realize the combustion operation of the burner with high reliability in a good combustion state without causing defects.

The figure which shows the structure of the main body part of the water heater which comprises the combustion apparatus of one Embodiment of this invention. The flowchart which shows the operation control processing by the control device shown in FIG. The figure for demonstrating the blockage degree detection process of STEP 1 or 7 of FIG. 4A and 4B are diagrams for explaining the control process in STEP 10 of FIG. The figure for demonstrating the control process in STEP 9 of FIG. 6A and 6B are diagrams for explaining the operation related to the combustion operation of the burner when the degree of occlusion is increased. 7A and 7B are diagrams for explaining the operation related to the combustion operation of the burner when the degree of occlusion is reduced. 8A and 8B are diagrams for explaining other embodiments.

An embodiment of the present invention will be described below with reference to FIGS. 1 to 7. With reference to FIG. 1, the combustion device of the present embodiment is, for example, a combustion device provided in the water heater A. The water heater A includes a water heater main body 1 installed outdoors.

The water heater main body 1 includes a combustion device 2 in its casing 1a (hereinafter referred to as a main body case 1a). The combustion device 2 includes a combustion casing 3, a burner 4 arranged in a combustion chamber 3a which is an internal space of the combustion casing 3, and combustion air (outside air) of the burner 4 from the external space of the main body case 1a to the combustion chamber 3a. The air supply passage 10a for introducing the combustion, the exhaust passage 10b for deriving the combustion exhaust gas from the combustion chamber 3a to the external space of the main body case 1a, and the combustion air (outside air) are supplied to the burner 4 through the air supply passage 10a. A combustion fan 11 is provided.

In the present embodiment, the burner 4 is a gas burner that burns fuel gas, and is arranged in the lower part of the combustion chamber 3a. In the present embodiment, the burner 4 is composed of a first burner 4a and a second burner 4b having different combustion areas.

In order to supply fuel gas to the burner 4, the main gas supply path 5 shared by the first burner 4a and the second burner 4b is introduced into the main body case 1a from the outside. The upstream side of the main gas supply path 5 is connected to a gas supply source pipe (not shown) outside the main body case 1a.

The main gas supply path 5 is branched into a first sub gas supply path 6a for the first burner 4a and a second sub gas supply path 6b for the second burner 4b inside the main body case 1a. Then, these first secondary gas supply passages 6a and second secondary gas supply passages 6b are introduced into the combustion chamber 3a so as to be able to supply fuel gas to each of the first burner 4a and the second burner 4b, respectively. There is.

In the main gas supply path 5, a main valve 7 composed of a solenoid valve that opens and closes the main gas supply path 5 and a proportional valve 8 as a fuel adjustment valve for adjusting the supply amount (flow rate) of fuel gas to the burner 4 are provided. It is being mediated. Further, switching valves 9a and 9b configured by solenoid valves for opening and closing each of the first sub gas supply path 6a and the second sub gas supply path 6b are interposed.

Therefore, by switching the combination of the open / closed states of the switching valves 9a and 9b with the main valve 7 opened, the burner to be supplied with the fuel gas (the burner for performing the combustion operation) is changed to the first burner. It is possible to switch to either one or both of 4a and the second burner 4b.

Further, by controlling the energizing current of the proportional valve 8 during the combustion operation of the burner 4 (during the combustion operation of one or both of the first burner 4a and the second burner 4b), the amount of fuel gas supplied to the burner 4 is controlled. However, the flow rate is controlled according to the energizing current of the proportional valve 8. This makes it possible to variably control the amount of heat generated by the combustion operation of the burner 4 (the amount of combustion of the burner 4).

The burner 4 may be a burner having a single combustion area. In that case, the switching valves 9a and 9b are unnecessary.

The combustion chamber 3a communicates with the air supply passage 10a at the lower part of the combustion housing 3 and communicates with the exhaust passage 10b at the upper part of the combustion housing 3. The upstream side (inlet side) of the air supply passage 10a and the downstream side (outlet side) of the exhaust passage 10b are opened in the external space (in the atmosphere) of the main body case 1a, respectively. A combustion fan 11 is interposed in the air supply passage 10a. The combustion fan 11 is rotationally driven by an electric motor 11a, and by the rotational drive, combustion air (outside air) is sucked into the supply air passage 10a from the upstream side, and the sucked combustion air is further sucked into the supply air passage 10a. It operates so as to be sent into the combustion chamber 3a from the downstream side of the.

As a result, combustion air is supplied to the burner 4 in the combustion chamber 3a via the air supply passage 10a. Then, the amount of combustion air supplied to the burner 4 can be variably controlled by variably controlling the rotation speed (rotation speed) of the combustion fan 11 by energizing the electric motor 11a (hereinafter referred to as the fan motor 11a). It is possible to control.

In the following description, the entire supply / exhaust passage 10a and the exhaust passage 10b may be collectively referred to as the supply / exhaust passage 10.

The water heater main body 1 further includes a configuration for passing water. Specifically, in the combustion chamber 3a, a heat exchanger 21 heated by the combustion heat of the burner 4 is arranged above the burner 4. Then, a water passage 22 is arranged via the heat exchanger 21.

The water passage 22 has a water supply channel 23 introduced from the outside inside the main body case 1a and a hot water outlet 24 led out from the inside of the main body case 1a, and the water supply channel 23 is the water passage 21a of the heat exchanger 21. It is connected to the hot water channel 24 via.

The upstream side of the water supply channel 23 is connected to a water supply source pipe (not shown) outside the main body case 1a, and the downstream side of the hot water supply channel 24 is a hot water supply port such as a curan (not shown) arranged in a kitchen, a washroom, a bathroom, or the like. Connected to.

A bypass path 25 is connected in parallel to the water passage 21a of the heat exchanger 21 inside the main body case 1a. The bypass passage 25 is branched from the water supply passage 23 on the upstream side of the heat exchanger 21 and joins the hot water passage 24 on the downstream side of the heat exchanger 21. Therefore, it is possible to allow a part of the water flowing from the upstream side of the water supply channel 23 to pass through the hot water supply path 24 via the bypass path 25 without passing through the heat exchanger 21.

Then, for example, at the upstream end of the bypass passage 25 (branch point from the water supply passage 23), the ratio of the water flow rate of the water passage 21a of the heat exchanger 21 to the water flow rate of the bypass passage 25 (hereinafter, bypass). A bypass ratio adjusting valve 26 for adjusting the ratio) is interposed. The bypass ratio adjusting valve 26 is composed of, for example, an electric three-way valve or the like.

Further, the water supply channel 23 is provided with an electric water amount adjusting valve 27 for adjusting the water flow rate (hereinafter referred to as water supply flow rate) of the water supply channel 23 and a water amount sensor 28 for detecting the water supply flow rate. ing. Further, the hot water passage 24 is equipped with temperature sensors 29 and 30 that detect the temperature of hot water at a portion on the downstream side of the confluence portion of the bypass path 25 and a portion on the upstream side of the confluence portion, respectively.

In other words, the temperature detected by the temperature sensor 29 is the temperature of the hot water supplied to the hot water supply port on the downstream side of the hot water outlet 24, that is, the hot water supply temperature, and the temperature detected by the temperature sensor 30 is, in other words, heat. It is the temperature of the hot water discharged from the exchanger 21.

The main body case 1a is further provided with a control device 40 that controls the operation of the water heater A. The control device 40 is composed of one or more electronic circuit units including a CPU, RAM, ROM, an interface circuit, and the like (not shown).

The control device 40 includes operation data of the remote controller 50 for operating the water heater A (data indicating the on / off operation of the operation switch, data indicating the target hot water supply temperature, etc.) and each of the data provided in the water heater A. The detection signal of the sensor is input.

The remote controller 50 is installed in an indoor kitchen, bathroom, or the like, and can communicate with the control device 40 by wire or wirelessly.

The detection signals include the detection signals of the water amount sensor 28 and the temperature sensors 29 and 30, the detection signal of the rotation speed of the combustion fan 11, the detection signal of the energizing current of the fan motor 11a, and the like.

Then, the control device 40 has a blockage degree detection unit 41 that detects the blockage degree of the air supply / exhaust passage 10 and a combustion operation control that controls the combustion operation of the burner 4 as functions realized by the implemented program or hardware configuration. It has a part 42 and.

Although details will be described later, in the present embodiment, the blockage degree detection unit 41 uses the detection value of the energizing current of the fan motor 11a and the detection value (or target value) of the rotation speed (rotation speed) of the combustion fan 11. Then, an index value indicating the degree of blockage of the air supply / exhaust passage 10 (hereinafter referred to as the degree of blockage index value Rma2) is calculated.

In this embodiment, the blockage index value Rma2 is Rma2 = 1 in a state where the air supply / exhaust passage 10 is not blocked (the degree of blockage is zero or close to zero), and the air supply / exhaust passage 10 is blocked. It is an index value determined to increase to a value larger than "1" as the degree increases.

In addition, "a state in which the air supply / exhaust passage 10 is not blocked" means that the air supply / exhaust passage 10 is clogged with foreign matter such as dust, or an outside wind acts on the air supply / exhaust passage 10. , There is no factor that hinders the normal ventilation of the air supply / exhaust passage 10 due to the operation of the combustion fan 11.

Further, the combustion operation control unit 42 controls the fuel supply to the burner 4 via the main valve 7, the proportional valve 8, and the switching valves 9a and 9b, and controls the operation of the combustion fan 11 via the fan motor 11a. By performing the above, the combustion operation of the burner 4 is controlled.

In this case, the combustion operation control unit 42 functions as a calorific value lower limit adjusting unit 43 that adjusts the lower limit of the variable range of the calorific value (target calorific value) generated by the combustion operation of the burner 4 according to the blockage degree index value Rma2. including. Then, the combustion operation control unit 42 determines the target calorific value of the burner 4 within a variable range between the lower limit value of the calorific value determined by the calorific value lower limit value adjusting unit 43 and the predetermined upper limit value, and determines the target calorific value. The combustion operation of the burner 4 is controlled according to the amount of heat and the blockage degree index value Rma2.

Next, the operation of the water heater A of the present embodiment will be described together with the details of the processing of the control device 40. When a request for hot water supply operation of the water heater A occurs, the control device 40 controls the operation of the combustion device 2 as shown in the flowchart of FIG.

Here, in the present embodiment, the control device 40 monitors the presence or absence of water flow in the water passage 22 at a predetermined flow rate or more based on the detection signal of the water amount sensor 28 in a state where the operation switch of the remote controller 50 is turned on. To do. Then, when the control device 40 detects water flow of a predetermined flow rate or more, it assumes that a request for performing the combustion operation of the burner 4 has occurred, and controls the operation of the combustion device 2 as shown in the flowchart of FIG.

In this operation control, first, in STEP 1, the control device 40 operates the combustion fan 11 in order to pre-purge the combustion chamber 3a, and also executes the blockage degree detection process by the blockage degree detection unit 41.

In this case, the control device 40 controls the fan motor 11a by the combustion operation control unit 42 so that the combustion fan 11 is operated at a predetermined pre-purge rotation speed (hereinafter referred to as pre-purge rotation speed) for a certain period of time. .. As a result, ventilation is performed from the air supply passage 10a via the combustion chamber 3a and the exhaust passage 10b, and the combustion chamber 3a is pre-purged.

Further, the blockage degree detection process in STEP 1 is executed as follows in the present embodiment.

When the degree of blockage of the air supply / exhaust path 10 increases due to the progress of partial clogging of the air supply / exhaust path 10 or the influence of the outside wind acting on the air supply / exhaust path 10, the air volume at each rotation speed of the combustion fan 11 decreases. Therefore, the energizing current of the fan motor 11a (hereinafter referred to as the fan current) at each rotation speed of the combustion fan 11 is determined when the air supply / exhaust passage 10 is not blocked (degree of blockage). Is less than (if is zero). Then, the fan current at each rotation speed of the combustion fan 11 decreases as the degree of blockage of the air supply / exhaust passage 10 increases.

In the present embodiment, the blockage degree detection unit 41 executes a process of detecting the blockage degree of the air supply / exhaust passage 10 (a process of determining the blockage degree index value Rma2) by utilizing such a phenomenon.

In the blockage degree detection process in STEP 1, the blockage degree detection unit 41 detects the fan current and the rotation speed of the combustion fan 11 (hereinafter referred to as the fan rotation speed) during the observation period of a predetermined time width during the execution of pre-purge. The average value of the fan current detection values during the observation period (hereinafter referred to as the fan current average value Ix) and the average value of the fan rotation speed detection values (hereinafter referred to as the fan rotation speed average value) are sequentially acquired. Nx) and is calculated.

Since the fan rotation speed is controlled to a constant pre-purge rotation speed during execution of pre-purge, the average fan rotation speed Nx matches or substantially matches the set value (target value) of the pre-purge rotation speed. Therefore, in STEP 1, the calculation process of the average fan speed Nx may be omitted.

Then, the blockage degree detection unit 41 uses the fan current average value Ix and the fan rotation speed average value Nx (or the set value of the pre-purge rotation speed) in the above observation period to indicate the blockage degree of the air supply / exhaust passage 10. The degree index value Rma2 is determined.

In this case, when the fan current average value Ix is a current value within a predetermined range in which the degree of blockage of the air supply / exhaust passage 10 is zero or can be regarded as close to zero, for example, FIG. Current on line Lc1 when the value of fan rotation speed matches the average value of fan rotation speed Nx (or the set value of pre-purge rotation speed) within the range between lines Lc1 and Lc2 of the two-point chain line. When the current value is within the range between the value Ic1 (Nx) and the current value Ic2 (Nx) on the line Lc2), the value of the blockage index value Rma2 is set to "1".

The solid line L0 between the lines Lc1 and Lc2 shown in FIG. 3 is a line showing a standard correlation between the fan speed and the fan current when the air supply / exhaust passage 10 is not blocked (hereinafter, none). It is called the blockage line L0).

The line Lc2 on the upper limit side of the predetermined range is determined in advance so that the current value on the line Lc2 at each value of the fan rotation speed is slightly larger than the current value on the non-blocking line L0. The line Lc1 on the lower limit side of the predetermined range is set so that the current value on the line Lc1 at each value of the fan rotation speed is slightly smaller than the current value on the non-blocking line L0. It is a predetermined line.

In STEP1, the blockage degree detection unit 41 sets the current values Ic1 (Nx) and Ic2 (Nx) on the lines Lc1 and Lc2 corresponding to the average fan speed Nx (or the set value of the pre-purge speed). Obtained using a map or calculation formula created in advance so as to represent the functional characteristics of each of the lines Lc1 and Lc2 (functional characteristics of the fan current with respect to the fan rotation speed).

The current values on the lines Lc1 and Lc2 corresponding to the set values of the pre-purge rotation speed are stored in the memory of the control device 40 in advance, and these current values are stored in the current values Ic1 (Nx). It may be read from the memory as Ic2 (Nx).

Then, when the fan current average value Ix is a current value within the range between the current values Ic1 (Nx) and Ic2 (Nx), the blockage degree detection unit 41 sets the value of the blockage degree index value Rma2. Let it be "1".

When the fan current average value Ix deviates from the range between the current values Ic1 (Nx) and Ic2 (Nx), the blockage degree detection unit 41 is blocked by the following equation (1). Calculate the degree index value Rma2.

Rma2 = {(Ia-Ib) / (Ix-Ib) -1} x α + 1 …… (1)

Α used in the calculation of the equation (1) is, for example, a positive constant value of "1" or less. Further, each of Ia and Ib is a parameter determined as a function value of the fan rotation speed according to the average fan rotation speed Nx (or the set value of the pre-purge rotation speed). Hereinafter, Ia is referred to as a reference current value, and Ib is referred to as an auxiliary current value.

In the present embodiment, when the calculated fan current average value Ix in the blockage degree detection process of STEP1 is a current value smaller than the lower limit side line Lc1 of the lines Lc1 and Lc2 (Ix <Ic1 (Nx)). In this case), the blockage degree detection unit 41 uses the current value Ic1 (Nx) on the line Lc1 as the reference current value Ia to execute the arithmetic processing of the equation (1).

When the calculated fan current average value Ix is a current value larger than the upper limit side line Lc2 of the lines Lc1 and Lc2 (when Ix> Ic2 (Nx)), the reference current value Using the current value Ic2 (Nx) on the line Lc2 as Ia, the arithmetic processing of the equation (1) is executed.

Further, the auxiliary current value Ib is a current value whose functional characteristics with respect to the fan rotation speed are predetermined, for example, as shown by the line Lb in FIG. Then, when the blockage degree detection unit 41 executes the arithmetic processing of the equation (1) in STEP 1, the fan rotation speed average value Nx (the fan rotation speed average value Nx () is based on a map or an arithmetic formula created in advance so as to represent the functional characteristics of the line Lb. Alternatively, the auxiliary current value Ib (Nx) corresponding to the set value of the pre-purge rotation speed) is obtained, and the arithmetic processing of the equation (1) is executed using the obtained auxiliary current value Ib (Nx).

The auxiliary current value Ib corresponding to the set value of the pre-purge rotation speed is stored in the memory of the control device 40 in advance, and the auxiliary current value Ib is used for the arithmetic processing of the equation (1) in STEP1. It may be read from memory as the value of.

In the present embodiment, the blockage degree detection unit 41 determines the blockage degree index value Rma2 as described above during the execution of pre-purge in STEP1. The degree of blockage index value Rma2 determined in this way is "1" when the degree of blockage of the air supply / exhaust passage 10 is zero or is close to zero, and is larger than "1" when the degree of blockage increases. The value increases as the degree of obstruction increases.

For example, when the fan current average value Ix is the value illustrated in FIG. 3, the current value Ic1 (Nx) on the line Lc1 is the reference current value Ia, and the current value Ib (Nx) on the line Lb is the auxiliary current. Using it as the value Ib, the degree of blockage index value Rma2 is calculated by the arithmetic processing of the above equation (1). In this case, the degree of obstruction index value Rma2 is a value between "1.1" and "1.2".

Here, the line L11 in FIG. 3 is a line exemplifying the relationship between the fan speed and the fan current at the degree of closure at which Rma2 = 1.1, and the line L12 is at the degree of closure at which Rma2 = 1.2. This line illustrates the relationship between the fan speed and the fan current.

In addition, when a gust of wind enters from the inlet side of the air supply passage 10a, the load of the combustion fan 11 may temporarily increase, and the fan current may temporarily increase. In such a case, the degree of obstruction index value Rma2 calculated by the above formula (1) can be smaller than "1".

Supplementally, in the present embodiment, the blockage degree index value Rma2 is an index that can be used as a target value of the fan rotation speed or a correction coefficient for correcting the lower limit value of the variable range of the calorific value (combustion amount) of the burner 4. Since it is a value, the degree of obstruction index value Rma2 is calculated by an arithmetic expression such as the above equation (1).

However, the degree of blockage index value Rma2 may basically be a parameter having a characteristic of monotonically changing (monotonically increasing or monotonically decreasing) according to the degree of blockage of the air supply / exhaust passage 10, and is determined by a process different from the above. It may be an index value. For example, the value obtained by subtracting "1" from the value calculated by the equation (1), or the value calculated by the equation (1) with the auxiliary current value Ib as a constant value or zero, is set in the air supply / exhaust path 10. It may be obtained as an index value indicating the degree of obstruction.

Further, for example, the actual air volume of the air supply / exhaust passage 10, the actual internal pressure of the combustion chamber 3a, and the like are detected by using appropriate sensors, and these detected values are used as an index indicating the degree of blockage of the air supply / exhaust passage 10. It is also possible to get a value.

Returning to the explanation of the flowchart of FIG. 2, the control device 40 then determines whether the blockage degree index value Rma2 obtained in STEP 1 as described above is larger than a predetermined upper limit value (for example, 1.22). The process of determining whether or not to perform is executed in STEP2.

Here, in a situation where the determination result of STEP 2 is affirmative, the degree of obstruction of the air supply / exhaust passage 10 (particularly, the degree of obstruction caused by clogging of the air supply / exhaust passage 10 due to foreign matter such as dust) becomes too high, and the burner 4 It is predicted that it will be difficult to perform normal combustion operation.

Therefore, when the determination result of STEP2 becomes affirmative (when Rma2> the upper limit value), the control device 40 can operate the water heater A by blocking the air supply / exhaust passage 10 in STEP13. A blockage notification output, which is a notification output indicating that the system cannot be used, is generated. As the blockage notification output, for example, a visual notification output by a display of the remote controller 50 or the like, or an auditory notification output by a voice or an alarm sound can be adopted.

Further, the control device 40 stops the operation of the water heater A in STEP 14. In this case, the operation of the combustion fan 11 is stopped without starting the combustion operation of the burner 4.

When the determination result of STEP2 is negative (when Rma2 ≤ upper limit value), the controller 40 then sets the degree of obstruction index value Rma2 to be smaller than a predetermined value (for example, 1.1) in STEP3. Judge whether or not.

The situation where the judgment result of STEP 3 is negative is particularly when the calorific value (combustion amount) of the burner 4 is small (when the calorific value of the burner 4 is the lower limit value of the variable range or a calorific value close to it). The burner 4 misfires when it is affected by a temporary gust or the like acting on the road 10, or when the fan rotation speed is corrected according to the change in the blockage degree index value Rma2 due to the gust or the like. Alternatively, it is a situation in which poor combustion is likely to occur.

Therefore, when the determination result of STEP 3 is negative (when Rma2 ≧ predetermined value), the control device 40 adjusts (corrects) the lower limit value of the variable range of the calorific value of the burner 4 in STEP 5. As the value of the correction coefficient RQmin (hereinafter referred to as the calorific value lower limit correction coefficient RQmin), the blockage index value Rma2 (in other words, the blockage of the air supply / exhaust passage 10 before ignition of the burner 4) determined in STEP 1 during the pre-purge operation Set the blockage degree index value Rma2) indicating the degree.

Further, when the determination result of STEP3 is affirmative (when Rma2 <predetermined value), the control device 40 sets "1" as the value of the calorific value lower limit correction coefficient RQmin in STEP4.

In this embodiment, the processes of STEP 3 to 5 are the processes executed by the calorific value lower limit adjusting unit 43. Further, the details of the process of adjusting (correcting) the lower limit value of the variable range of the heat amount of the burner 4 by the heat amount lower limit value adjusting unit 43 will be described later.

Next, in STEP 6, the control device 40 controls the ignition of the burner 4 by the combustion operation control unit 42. In this ignition control process, the combustion operation control unit 42 controls the fan motor 11a so as to operate the combustion fan 11 at a predetermined rotation speed for ignition. At the same time, the combustion operation control unit 42 drives the igniter (not shown) and supplies the fuel gas of a predetermined flow rate to one (or both) of the first burner 4a and the second burner 4b. And one (or both) of the proportional valve 8 and the switching valves 9a and 9b are controlled. As a result, the burner 4 is ignited and the combustion operation of the burner 4 is started.

After that, the control device 40 repeats the loop processing of STEPs 7 to 12 during the combustion operation of the burner 4.

In STEP 7, the control device 40 executes the blockage degree detection process by the blockage degree detection unit 41. The method of the blockage degree detection process in STEP 7 is the same as the blockage degree detection process in STEP1.

However, the blockage degree detection process in STEP 7 is a predetermined time shorter than the time width of the observation period for acquiring the detection value of the fan current used for calculating the fan current average value Ix during the execution of the pre-purge in STEP 1. It is a process that is repeatedly executed in a cycle of width (for example, 1 second) (the cycle is a cycle of repeating the loop process of STEP7 to 12).

Further, during the combustion operation of the burner 4, the fan rotation speed is appropriately changed according to the amount of heat of the burner 4. Therefore, in the blockage degree detection process in STEP 7 in each cycle period, the fan rotation speed average in each cycle period. The value Nx is calculated.

If it can be considered that the fan rotation speed in each cycle period is kept constant or almost constant, the fan rotation speed in each cycle period is replaced with the fan rotation speed average value Nx in each cycle period. It is also possible to use the target value of.

The blockage degree detection process in STEP 7 is the same as the blockage degree detection process in STEP 1 except for the above items. That is, when the fan current average value Ix in each cycle period is a current value within the range between the lines Lc1 and Lc2, the blockage degree index value Rma2 is set to "1". When the average fan current Ix in each cycle deviates from the range between the lines Lc1 and Lc2, the blockage index value Rma2 is calculated by the above equation (1).

In the loop processing, the control device 40 sequentially determines in STEP 8 whether or not the blockage degree index value Rma2 determined in STEP 7 is larger than "1". When the determination result of STEP 8 is negative (when Rma2 ≦ 1), the control device 40 normally performs combustion control in STEP 10 by the combustion operation control unit 42.

This normal combustion control is a control process for performing the combustion operation of the burner 4 assuming that the air supply / exhaust passage 10 is not blocked. In this normal combustion control, the control device 40 first determines the target heat amount (target value of the combustion amount) of the burner 4 within a predetermined variable range.

Specifically, in the present embodiment, the combustion operation control unit 42 makes the hot water supply temperature detected by the temperature sensor 29 match or substantially match the target hot water supply temperature set by the remote control 50. Based on the detection signals of 29, 30 and the water amount sensor 28, the target heat amount of the burner 4, the control target value of the bypass ratio adjusting valve 26 (for example, the target value of the bypass ratio), and the control target value of the water amount adjusting valve 27. (For example, the target value of the water supply flow rate) is determined sequentially.

In this case, the target calorific value of the burner 4 is determined within a predetermined variable range (within the range between the minimum calorific value Qmin_a and the maximum calorific value Qmax of the rated design determined in advance in the specifications of the water heater A). ..

Then, the combustion operation control unit 42 controls the fan motor 11a and the proportional valve 8 according to the determined target heat quantity. Specifically, the combustion operation control unit 42 can supply the burner 4 with the combustion amount air and fuel gas of the required flow rate for achieving the target heat amount without the air supply / exhaust passage 10 being blocked. The target value of the fan rotation speed and the target value of the energizing current of the proportional valve 8 (hereinafter referred to as the proportional valve current) are determined.

In this case, the target value of the fan rotation speed is determined by a map or a calculation formula created in advance so that the relationship between the heat quantity of the burner 4 and the fan rotation speed becomes, for example, the correlation shown in the graph of FIG. 4A. Determined according to the target calorific value. Further, the target value of the proportional valve current is, for example, the fan rotation according to a map or an arithmetic formula created in advance so that the relationship between the fan rotation speed and the proportional valve current becomes the correlation shown in the graph of FIG. 4B. It is determined according to the detected value or the target value of the number.

Here, the graphs of FIGS. 4A and 4B show the minimum calorific value Qmin_a and the maximum calorific value Qmax shown in FIG. 4A within a predetermined calorific value variable range in a state where the air supply / exhaust passage 10 is not blocked (Rma2 = 1). It is a graph showing the interrelationship between the calorific value of the burner 4, the fan rotation speed, and the proportional valve current, which is necessary for satisfactorily performing the combustion operation of the burner 4 with an arbitrary calorific value (within the range between).

The target value of the proportional valve current may be determined directly (without using the value of the fan speed) according to the target amount of heat.

In the normal combustion control of STEP 10, the combustion operation control unit 42 matches or substantially matches the actual fan rotation speed with the target value of the fan rotation speed determined as described above, so that the energizing current (fan current) of the fan motor 11a is matched. Is feedback-controlled, and the proportional valve current of the target value determined as described above is energized in the proportional valve 8. As a result, the burner 4 is supplied with combustion air and fuel gas having a flow rate corresponding to the target calorific value. As a result, the combustion operation of the burner 4 at the target calorific value is realized.

Further, the combustion operation control unit 42 controls the bypass ratio adjusting valve 26 and the water amount adjusting valve 27 according to their respective control target values. As a result, the hot water supply temperature of the hot water supplied from the hot water outlet 24 to the hot water supply port is controlled to match or substantially match the target hot water supply temperature.

It should be noted that during the combustion operation of the burner 4, after the judgment result of STEP8 becomes positive, immediately after the judgment result of STEP8 becomes negative (that is, the degree of blockage index value Rma2 is larger than "1"). Therefore, immediately after the value drops to "1" or less), the fan rotation speed is corrected and the lower limit of the variable range of the calorific value of the burner 4 is temporarily corrected. This will be described later.

Supplementally, in the normal combustion control of STEP 10 when the degree of blockage index value Rma2 determined in STEP 7 is smaller than "1", the target value of the fan rotation speed determined according to the target heat amount of the burner 4 as described above is set. , The fan motor 11a may be controlled according to the correction in the decreasing direction according to the blockage degree index value Rma2 and the corrected target value.

When the determination result of STEP 8 is affirmative (when Rma2> 1), the control device 40 controls the combustion of the burner 4 in STEP 9 by the combustion operation control unit 42. The combustion control of STEP 9 is a control process including correction control of the fan rotation speed and correction control of the lower limit value of the variable range of the calorific value of the burner 4.

In the combustion control of STEP 9 (hereinafter referred to as combustion control with correction), the combustion operation control unit 42 has a fan rotation correction coefficient Rma, which is a correction coefficient for correcting the fan rotation speed, and a lower limit of the variable range of the calorific value of the burner 4. The calorific value lower limit correction coefficient RQmin, which is a correction coefficient for correcting the value, is sequentially calculated.

In this case, the combustion operation control unit 42 sets each of the fan rotation correction coefficient Rma and the calorific value lower limit correction coefficient RQmin to the blockage degree index value Rma2 with the blockage degree index value Rma2 sequentially determined in STEP 7 as a target value. The fan rotation correction coefficient Rma and the calorific value lower limit correction coefficient RQmin are calculated so as to approach each other at the rate of change (a predetermined increase or decrease per unit time).

However, as in the case immediately after the blockage degree index value Rma2 increases from a certain value due to the influence of the outside wind acting on the air supply / exhaust passage 10, the fan rotation correction coefficient Rma and the calorific value lower limit correction coefficient RQmin are set to the blockage degree. In a situation where the value smaller than the index value Rma2 is increased toward the degree of blockage index value Rma2, the combustion operation control unit 42 sets the calorific value lower limit correction coefficient RQmin to be relatively larger than the fan rotation correction coefficient Rma. Each of the fan rotation correction coefficient Rma and the calorific value lower limit correction coefficient RQmin is calculated so as to approach the blockage degree index value Rma2 at the increase rate (increase amount per unit time).

Further, as in the case immediately after the blockage index value Rma2 decreases from a certain value, the fan rotation correction coefficient Rma and the calorific value lower limit correction coefficient RQmin are changed from a value larger than the blockage index value Rma2 to a blockage index value Rma2. In the situation of decreasing toward, the combustion operation control unit 42 sets the fan rotation correction coefficient Rma at a decrease rate (decrease amount per unit time) relatively larger than the heat amount lower limit correction coefficient RQmin, and the degree of blockage. Each of the fan rotation correction coefficient Rma and the calorific value lower limit correction coefficient RQmin is calculated so as to approach the index value Rma2.

Specifically, the combustion operation control unit 42 has the following equation (2a) in a predetermined update cycle (update cycle of t seconds) according to the magnitude relationship between the calorific value lower limit correction coefficient RQmin and the blockage degree index value Rma2. ) Or (2b), the calorific value lower limit correction coefficient RQmin is calculated.

When the state where Rma2> RQmin continues for t seconds RQmin (after update) = RQmin (before update) + R1up …… (2a)
When the state where Rma2 <RQmin continues for t seconds RQmin (after update) = RQmin (before update) -R1down …… (2b)

The above R1up and R1down are positive constant values predetermined as parameters that define the amount of increase in the calorific value lower limit correction coefficient RQmin per unit time and the amount of decrease per unit time, respectively.

When the value of the calorific value lower limit correction coefficient RQmin after the update of the equation (2a) is RQmin> Rma2, or when the value of the calorific value lower limit correction coefficient RQmin after the update of the equation (2b) is RQmin < When it becomes Rma2, the value of the updated calorific value lower limit correction coefficient RQmin is set to a value corresponding to Rma2.

Further, when Rma2> RQmin or Rma2 <RQmin does not continue for t seconds, that is, within the time of t seconds, Rma2 ≤ RQmin from the state where the blockage index value Rma2 becomes Rma2> RQmin. When the state changes to, or when the state changes from the state where Rma2 <RQmin to the state where Rma2 ≧ RQmin, the value of the calorific value lower limit correction coefficient RQmin after the update is maintained at the same value as before the update. To.

Further, as the initial value of the calorific value lower limit correction coefficient RQmin at the start of the combustion operation of the burner 4 (immediately after ignition), the blockage degree index value Rma2 set in STEP 4 or 5 is used after the pre-purge operation.

Further, the combustion operation control unit 42 has the following equation (3a) or (3b) in a predetermined update cycle (update cycle of t seconds) according to the magnitude relationship between the fan rotation correction coefficient Rma and the blockage degree index value Rma2. ) Is used to calculate the fan rotation correction coefficient Rma.

When the state where Rma2> Rma continues for t seconds Rma (after update) = Rma (before update) + R2up …… (3a)
When the state where Rma2 <Rma continues for t seconds Rma (after update) = Rma (before update) -R2down …… (3b)

The R2up and R2down are positive constant values defined in advance as parameters that specify the amount of increase in the fan rotation correction coefficient Rma per unit time and the amount of decrease per unit time, respectively.

When the value of the fan rotation correction coefficient Rma after updating the equation (3a) is Rma> Rma2, or when the value of the fan rotation correction coefficient Rma after updating the equation (3a) is Rma <Rma2. In each case, the value of the updated fan rotation correction coefficient Rma is set to a value that matches Rma2.

Further, when Rma2> Rma or Rma2 <Rma does not continue for t seconds, that is, within the time of t seconds, the degree of obstruction index value Rma2 becomes Rma2> Rma, and then Rma2 ≤ Rma. When the state changes to, or when the state changes from the state where Rma2 <Rma to the state where Rma2 ≧ Rma, the value of the fan rotation correction coefficient Rma after the update is maintained at the same value as before the update. ..

Further, as the initial value of the fan rotation correction coefficient Rma at the start of the combustion operation of the burner 4 (immediately after ignition), for example, the value of the blockage degree index value Rma2 determined in STEP 1 during the execution of pre-purge is used. Alternatively, for example, the value of the fan rotation correction coefficient Rma immediately before the end of the previous combustion operation of the burner 4 can be used as the initial value of the fan rotation correction coefficient Rma.

Here, in the present embodiment, the parameter R1up of the above equation (2a) that defines the amount of increase in the calorific value lower limit correction coefficient RQmin per unit time defines the amount of increase in the fan rotation correction coefficient Rma per unit time. The value is set to be larger than the parameter R2up in the equation (3a). That is, R1up> R2up.

Further, the parameter R1down of the above equation (2b) that defines the amount of decrease of the calorific value lower limit correction coefficient RQmin per unit time is the parameter of the above equation (3b) that defines the amount of decrease of the fan rotation correction coefficient Rma per unit time. It is set to a value smaller than R2down. That is, R2down> R1down.

Therefore, in a situation where the fan rotation correction coefficient Rma and the heat quantity lower limit correction coefficient RQmin are increased toward the blockage index value Rma2, the heat quantity lower limit correction coefficient RQmin is relatively larger than the fan rotation correction coefficient Rma. Each of the fan rotation correction coefficient Rma and the heat quantity lower limit correction coefficient RQmin is updated so as to approach the blockage degree index value Rma2 at the increasing speed.

Further, in a situation where the fan rotation correction coefficient Rma and the calorific value lower limit correction coefficient RQmin are decreased toward the blockage degree index value Rma2, the fan rotation correction coefficient Rma is relatively larger than the calorific value lower limit value correction coefficient RQmin. Each of the fan rotation correction coefficient Rma and the heat quantity lower limit correction coefficient RQmin is updated so as to approach the blockage degree index value Rma2 at the decreasing rate.

Then, in the situation where the blockage degree index value Rma2 is maintained constant, the fan rotation correction coefficient Rma and the heat quantity lower limit value correction coefficient RQmin are finally maintained at the same values as the blockage degree index value Rma2.

For example, referring to FIG. 5, when the degree of blockage index value Rma2 increases from the value Rma2_a to Rma2_b at time t1 as shown by the broken line graph, the fan rotation correction coefficient Rma is shown by the solid line graph. , The values of the fan rotation correction coefficient Rma and the calorific value lower limit correction coefficient RQmin are updated so as to increase from Rma2_a to Rma2_b at a speed relatively slower than the calorific value lower limit correction coefficient RQmin.

Further, when the degree of blockage index value Rma2 decreases from the value Rma2_b to Rma2_a at time t2 as shown by the graph of the broken line in FIG. 5, the calorific value lower limit correction coefficient RQmin decreases from the value Rma2_a to the fan rotation as shown by the solid line graph. The values of the fan rotation correction coefficient Rma and the calorific value lower limit correction coefficient RQmin are updated so as to decrease from Rma2_b to Rma2_a at a speed relatively slower than the correction coefficient Rma.

Note that FIG. 5 shows a graph of changes over time in the fan rotation correction coefficient Rma and the calorific value lower limit correction coefficient RQmin, with the update cycle t of the fan rotation correction coefficient Rma and the calorific value lower limit correction coefficient RQmin being sufficiently short. ..

In the combustion control with correction in STEP 9, the combustion operation control unit 42 further corrects the lower limit value of the variable range of the calorific value of the burner 4 by using the calorific value lower limit value correction coefficient RQmin determined as described above (the lower limit value). Is corrected from the rated minimum calorific value Qmin_a). Then, the combustion operation control unit 42 determines the target heat amount of the burner 4 within a variable range between the corrected lower limit value and the predetermined maximum heat amount Qmax.

In this case, the combustion operation control unit 42 corrects the lower limit value Qmin of the variable range of the calorific value of the burner 4 by, for example, the following equation (4). Hereinafter, the lower limit value after the correction of the variable range of the calorific value of the burner 4 calculated by the equation (4) is referred to as the calorific value lower limit correction value Qmin.

Qmin = {(Qmin_b−Qmin_a) / (Rmax-1)} × (RQmin-1) ＋ Qmin_a …… (4)

Qmin_a is the rated minimum calorific value of the burner 4 (= lower limit of calorific value lower limit correction value Qmin), Qmin_b is the upper limit value of calorific value lower limit correction value Qmin (predetermined set value), and Rmax is the calorific value lower limit correction value Qmin. Is the value of the blockage degree index value Rma2 (predetermined set value) when is consistent with the upper limit value Qmin_b.

When the variable range of the heat rating of the burner 4 is, for example, the range of Qmin_a to Qmax shown in FIG. 4A, the value shown in FIG. 4A is adopted as the upper limit value Qmin_b of the heat quantity lower limit correction value Qmin. Can be done. Further, as the value of Rmax, for example, "1.2" or the like can be adopted.

By calculating the heat quantity lower limit correction value Qmin as described above, the value of the heat quantity lower limit correction value Qmin becomes Qmin_a according to the value of the heat quantity lower limit correction coefficient RQmin (so that it increases as the value of RQmin increases). It will be determined variably with Qmin_b (see FIG. 4A).

Then, the combustion operation control unit 42 controls the combustion operation of the burner 4 by using the fan rotation correction coefficient Rma determined as described above and the calorific value lower limit correction value Qmin.

Specifically, the combustion operation control unit 42 limits the variable range of the calorific value of the burner 4 to the range between the calorific value lower limit correction value Qmin and the maximum calorific value Qmax, and then, as in the case of the normal combustion control, The target heat amount of the burner 4, the control target value of the bypass ratio adjusting valve 26, and the control target value of the water amount adjusting valve 27 are sequentially determined so that the hot water supply temperature matches or substantially matches the target hot water supply temperature.

Then, the combustion operation control unit 42 controls the fan motor 11a and the proportional valve 8 according to the target heat amount of the burner 4 determined as described above. Specifically, the combustion operation control unit 42 determines to have a correlation exemplified in FIG. 4A with respect to the target value of the fan rotation speed determined according to the target heat amount as in the normal control. The target value for controlling the fan rotation speed is determined by using the value of the fan rotation speed as the reference target value and correcting the reference target value. In this case, the target value for controlling the fan rotation speed is determined by multiplying the reference target value according to the target heat quantity by the fan rotation correction coefficient Rma.

From the value of the target heat quantity of the burner 4 and the value of the fan rotation correction coefficient Rma, for example, it is possible to determine the target value for controlling the fan rotation speed by using a map or the like created in advance.

Further, the combustion operation control unit 42 illustrates in FIG. 4B according to the target value of the fan rotation speed based on the above reference, or according to the value obtained by dividing the detected value of the fan rotation speed by the fan rotation correction coefficient Rma. The target value of the proportional valve current is determined based on the correlation. The target value of the proportional valve current may be determined directly (without using the value of the fan rotation speed) according to the target amount of heat of the burner 4.

In the combustion control with correction in STEP 9, the combustion operation control unit 42 makes the actual fan rotation speed match or almost match the target value for controlling the fan rotation speed (corrected target value) determined as described above. , The energization current (fan current) of the fan motor 11a is feedback-controlled, and the proportional valve current of the target value determined as described above is energized to the proportional valve 8. As a result, the burner 4 is supplied with combustion air and fuel gas at a flow rate corresponding to the target heat amount so as to prevent a decrease in the supply amount of combustion air due to an increase in the degree of blockage of the air supply / exhaust passage 10. To. As a result, the combustion operation of the burner 4 at the target calorific value is properly realized.

Further, the combustion operation control unit 42 controls the bypass ratio adjusting valve 26 and the water amount adjusting valve 27 according to their respective control target values, as in the case of the normal combustion control. As a result, the hot water supply temperature of the hot water supplied from the hot water outlet 24 to the hot water supply port is controlled to match or substantially match the target hot water supply temperature.

Supplementally, during the combustion operation of the burner 4, the degree of blockage index value Rma2 is "1" or less after the judgment result of STEP 8 is temporarily positive due to the influence of a gust acting on the air supply / exhaust passage 10. In some cases, the value decreases and the determination result of STEP 8 becomes negative. In the normal combustion control of STEP 10 in such a case, the combustion operation control unit 42 has the correction of STEP 9 until the fan rotation correction coefficient Rma calculated by the above equation (4b) decreases to "1.0" or less. Similar to the combustion control, the fan rotation speed is corrected according to the fan rotation correction coefficient Rma.

Further, the combustion operation control unit 42 has the same calorific value lower limit correction coefficient as the combustion control with correction in STEP 9 until the calorific value lower limit correction coefficient RQmin calculated by the above equation (3b) decreases to "1" or less. The process of changing the calorific value lower limit correction value Qmin according to RQmin (reducing it to the rated minimum calorific value Qmin_a) is executed.

In the loop processing, the control device 40 is used for fan correction in which the value of the fan rotation correction coefficient Rma is predetermined as the upper limit of the allowable limit for correcting the fan rotation speed, following the control processing of STEP 9 or 10. In STEP 11, it is determined whether or not the value is larger than the upper limit value (for example, 1.2).

When the determination result of STEP 11 is affirmative (when Rma> the upper limit value for fan correction), the control device 40 performs the determination device 40 in the STEP 13 as in the case where the determination result of the STEP 2 is affirmative. Generates a blockage notification output.

Further, the control device 40 stops the operation of the water heater A in STEP 14. In this case, the control device 40 extinguishes the burner 4 and further stops the operation of the combustion fan 11 by controlling the closing of the main valve 7 (cutting off the fuel supply to the burner 4). As a result, the combustion operation of the burner 4 is forcibly stopped.

On the other hand, if the determination result of STEP 11 is negative, the control device 40 further determines in STEP 12 whether or not there is a request to stop the hot water supply operation of the water heater A.

Here, when the amount of water detected by the water amount sensor 28 drops below a predetermined value (that is, when the amount of water flowing through the water passage 22 becomes zero or minute), the determination result of STEP 12 becomes affirmative. In this case, the control device 40 stops the hot water supply operation of the water heater A in STEP 14. In this STEP 14, the control device 40 extinguishes the burner 4 and further stops the operation of the combustion fan 11 as in the case where the determination result of the STEP 11 becomes affirmative.

If the determination result of STEP 12 is negative (when there is no request to stop the hot water supply operation of the water heater A), the control device 40 repeats the loop process from STEP 7.

In the present embodiment, the operation control of the combustion device 2 of the water heater A is performed as described above. In such a water heater A, particularly when the combustion operation of the burner 4 is performed with a small amount of heat (specifically, the amount of heat within the range between the lower limit value Qmin_a of the calorific value lower limit correction value Qmin and the upper limit value Qmin_b of the burner 4 The following effects can be achieved when the combustion operation is performed).

For example, during the combustion operation of the burner 4 by the normal combustion control of STEP 10 (during the combustion operation of the burner 4 in the state where the air supply / exhaust passage 10 is not blocked), the target heat amount of the burner 4 is the rated minimum heat amount Qmin_a (=). While limited to the lower limit of the calorific value lower limit correction value Qmin), the degree of blockage of the air supply / exhaust path 10 temporarily increases due to the influence of outside wind such as a gust of wind acting on the air supply / exhaust path 10, and the degree of blockage is said to be the degree of blockage. It is assumed that the index value Rma2 temporarily increases from "1" to a value larger than that.

In this case, the calorific value lower limit correction coefficient RQmin is used to correct the calorific value lower limit correction value Qmin (correction in the increasing direction), so that the calorific value lower limit correction value Qmin becomes the blockage degree index value immediately before the increase, as shown in FIG. 6A. From the calorific value lower limit correction value Qmin1 (here, Qmin1 = Qmin_a) corresponding to Rma2, the calorific value lower limit correction value Qmin2 corresponding to the increased blockage index value Rma2 (specifically, the calorific value lower limit correction coefficient RQmin is increased. It increases to the calorific value lower limit correction value Qmin2) when the blockage index value Rma2 is reached. Along with this, the target calorific value of the burner 4 increases from Qmin1 (= Qmin_a) to Qmin2.

Further, the target value of the fan rotation speed is an increase in the reference target value of the fan rotation speed due to an increase in the target heat amount of the burner 4, and a correction of the reference target value by the fan rotation correction coefficient Rma (correction in the increasing direction). As a result, it increases from N1 to N2 as shown in FIG. 6A. N1 is a target value determined corresponding to the target heat amount (= Qmin1 = Qmin_a) of the burner 4 in the state immediately before the increase of the blockage degree index value Rma2 (the value of the fan rotation speed corresponding to Qmin_a in FIG. 4A). , N2 is the reference target value of the fan rotation speed when the target heat quantity of the burner 4 increases to Qmin2 (the value of the fan rotation speed on the solid line L1 shown in FIG. 6A), and the blockage degree index value after the increase. It is a value corrected by Rma2 (> 1).

The solid line L1 in FIG. 6A is the target value of the burner 4 and the target value of the fan rotation speed (the target value of the reference) when the air supply / exhaust path 10 is not blocked (when Rma2 = 1). The line showing the relationship (the line having the same characteristics as that shown in FIG. 4) and the broken line L2 are the target heat amount of the burner 4 in the degree of blockage of the air supply / exhaust passage 10 corresponding to the increased degree of blockage index value Rma2. A line showing the relationship with the target value of the fan rotation speed (specifically, the target value of the fan rotation speed at each value of the target heat quantity becomes the reference target value on the line L1 and the blockage degree index value Rma2 (>) after the increase. It is a line) that is a value obtained by multiplying 1).

Here, since the calorific value lower limit correction coefficient RQmin and the fan rotation correction coefficient Rma are sequentially updated at different speeds of change as described above, the target value of the fan rotation speed corresponds to the blockage degree index value Rma2 after the increase. Before reaching the target value N2, the calorific value lower limit correction value Qmin (and thus the target calorific value of the burner 4) reaches the value Qmin2 corresponding to the increased blockage index value Rma2.

Therefore, as shown by the line AL1 with an arrow in FIG. 6A, the set of the target heat amount of the burner 4 and the target value of the fan rotation speed has a target heat amount of Qmin2 from the point P1 immediately before the increase of the blockage degree index value Rma2. After reaching the point P2, the target value of the fan rotation speed changes so as to reach the point P3 at N2.

When the set of the target heat amount of the burner 4 and the target value of the fan rotation speed is changed in this way, the set of the actual heat amount generated by the burning operation of the burner 4 and the actual air volume of the combustion fan 11 is For example, it changes from point P4 to point P5 in the manner illustrated by the line AL2 with an arrow in FIG. 6B.

At point P4 (starting point of line AL2), in detail, just before the increase of the degree of blockage index value Rma2, the action of the outside wind (outside wind that temporarily increases the degree of blockage of the supply / exhaust passage 10) acts on the air supply / exhaust passage 10. It is a point showing the set of the actual heat amount of the burner 4 and the actual air volume of the combustion fan 11 at the time of starting, and P5 (the end point of the line AL2) is the target heat amount of the burner 4 and the target of the fan rotation speed. The value indicates a set of the actual amount of heat of the burner 4 and the actual amount of air of the combustion fan 11 when the Qmin2 and N2 are reached, respectively.

Here, when an outside wind such as a gust that increases the degree of blockage acts on the air supply / exhaust passage 10, the air volume of the combustion fan 11 tends to decrease and the internal pressure of the combustion chamber 3a tends to increase. As a result, in particular, the flow rate of the fuel gas ejected from the burner 4 in a state where the amount of heat is small tends to decrease.

Therefore, the actual calorific value Q4 of the burner 4 at the point P4 tends to be smaller than the calorific value lower limit correction value Qmin1 (= Qmin_a), which is the target calorific value of the burner 4 immediately before the increase of the blockage index value Rma2. Therefore, in FIG. 6B, the actual heat amount Q4 of the burner 4 at the point P4 is set to be smaller than Qmin_a.

Further, the actual air volume of the burner 4 at the point P4 (the air volume when the target value of the fan rotation speed is N1) is the degree of blockage of the air supply / exhaust path 10 due to the outside wind acting on the air supply / exhaust path 10. Due to the increase, the air volume is lower than that before the start of the action of the outside wind.

On the other hand, the region of the combination of the calorific value of the burner 4 and the air volume of the combustion fan 11 (a calorific value smaller than Qmin_a) capable of performing the combustion operation of the burner 4 at an appropriate air-fuel ratio without causing a misfire or a combustion failure of the burner 4. The region (including the region) is the region between the lines L4 and L5 shown in FIG. 6B. The solid line L3 is a line showing the relationship between the amount of heat of the burner 4 and the amount of air of the combustion fan 11 that can perform the combustion operation of the burner 4 at the optimum or substantially the optimum air-fuel ratio.

In the region between the lines L4 and L5 (hereinafter referred to as the proper combustible region), as shown in the figure, the smaller the actual amount of heat of the burner 4, the narrower the range of the proper air volume. Therefore, at the time immediately before the increase of the blockage index value Rma2 (during the combustion operation of the burner 4 at the point P4), the fan rotates so as to increase the air volume without increasing the actual heat amount of the burner 4 so much. When the number is increased, the set of the actual amount of heat of the burner 4 and the actual amount of air of the combustion fan 11 is the line on the upper limit side from the proper combustible region, as illustrated by the two-dot chain line AL3 in FIG. 6B, for example. It is easy to deviate to the upper region of L5.

However, in the present embodiment, since the set of the target heat quantity of the burner 4 and the target value of the fan rotation speed is changed in the manner shown by the line AL1 of FIG. 6A, the actual heat quantity of the burner 4 and the actual combustion fan 11 are changed. As shown by the line AL2 in FIG. 6B, the actual amount of heat of the burner 4 rapidly increases toward the amount of heat at the point P5 at the initial stage of the change, while the actual amount of heat at the initial stage is increased. The amount of change (increase amount) of is limited to a part of the total amount of change in air volume from points P4 to P5.

Therefore, the amount of change in air volume at the initial stage of the change in the set of the actual amount of heat and the amount of air can be suppressed to a small amount of change, and the actual amount of heat has increased to some extent (and within the proper combustible region). The amount of change in air volume when the range of air volume belonging to is expanded to a relatively wider range than the range corresponding to the amount of heat at point P4) can be made a large amount of change.

As a result, the set of the actual amount of heat of the burner 4 and the actual amount of air of the combustion fan 11 is maintained within the proper combustible region (while the combustion state of the burner 4 is kept in a good state), and the amount of heat and the amount of heat are maintained. The set of air volume can be changed.

Next, for example, as described above (as shown in FIG. 6A), the calorific value lower limit correction value Qmin is increased from the Qmin1 (= Qmin_a) to Qmin2 (and thus, the target calorific value of the burner 4 is increased from Qmin1 (= Qmin_a)). (Increase to Qmin2), and after increasing the target value of the fan speed from N1 to N2, the outside wind such as a gust stops acting on the air supply / exhaust passage 10, and the blockage of the air supply / exhaust passage 10 is resolved. Imagine that.

In this case, since the degree of blockage index value Rma2 decreases, the calorific value lower limit correction value Qmin is corrected (correction in the decreasing direction) by the calorific value lower limit correction coefficient RQmin. Therefore, as shown in FIG. 7A, the calorific value lower limit correction value Qmin corresponds to the blockage index value Rma2 immediately before the decrease (the blockage index value Rma2 when the air supply / exhaust passage 10 is exposed to the outside wind). It decreases from the value Qmin2 to the calorific value lower limit correction value Qmin1 (= Qmin_a) corresponding to the decrease index value Rma2 (here, "1"). Along with this, the target calorific value of the burner 4 decreases from Qmin2 to Qmin1 (= Qmin_a).

Further, the target value of the fan rotation speed is the correction of the reference target value by the fan rotation correction coefficient Rma (correction in the decreasing direction) and the decrease of the reference target value of the fan rotation speed due to the decrease of the target heat amount of the burner 4. As a result, it decreases from N2 to N1 as shown in FIG. 7A. The lines L1 and L2 in FIG. 7A are the same lines as those shown in FIG. 6A.

Here, since the calorific value lower limit correction coefficient RQmin and the fan rotation correction coefficient Rma are sequentially updated at different rates of change as described above, the calorific value lower limit correction value Qmin (by extension, the target calorific value of the burner 4) is reduced. Before the calorific value lower limit correction value Qmin1 (= Qmin_a) corresponding to the blockage index value Rma2 is reached, the target value of the fan speed is the target on the line L1 corresponding to the blockage index value Rma2 (= 1) after the decrease. The value (in FIG. 7A, the target value (> N1) of the fan rotation speed at the point P12) is reached.

Therefore, the set of the target heat amount of the burner 4 and the target value of the fan rotation speed is the fan rotation speed from the point P11 immediately before the decrease of the blockage degree index value Rma2 as shown by the line AL4 with an arrow in FIG. 7A. After reaching the point P12 where the target value becomes the value (> N1) on the line L1, the line L1 reaches the point P13 where the target heat quantity and the fan speed of the burner 4 become Qmin1 (= Qmin_a) and N1, respectively. It changes along with.

When the set of the target heat amount of the burner 4 and the target value of the fan rotation speed is changed in this way, the set of the actual heat amount generated by the burning operation of the burner 4 and the actual air volume of the combustion fan 11 is For example, it changes from point P14 to point P15 in the manner illustrated by the line AL5 with an arrow in FIG. 7B.

The point P14 (starting point of the line AL5) is, specifically, the actual burner 4 at the time when the action of the outside air (outside wind that temporarily increases the degree of blockage of the air supply / exhaust path 10) on the air supply / exhaust path 10 is stopped. It is a point showing a set of the amount of heat and the actual amount of air of the combustion fan 11, and at P15 (the end point of the line AL5), the target amount of heat of the burner 4 and the target value of the fan rotation speed are set to Qmin1 and N1, respectively. It is a point showing a set of the actual heat amount of the burner 4 at the time of reaching and the actual air amount of the combustion fan 11.

Here, when the action of the outside air on the air supply / exhaust passage 10 is stopped, the blockage of the air supply / exhaust passage 10 is cleared at the time of the stop, so that the air volume of the combustion fan 11 increases. Therefore, the actual air volume of the combustion fan 11 at the point P14 becomes an air volume close to the line L5 on the upper limit side of the proper combustible region.

In such a state, if the actual calorific value of the burner 4 is reduced without significantly reducing the actual air volume of the combustion fan 11, the combination of the actual calorific value of the burner 4 and the actual air volume of the combustion fan 11 However, as illustrated by the alternate long and short dash line line AL6 in FIG. 7B, the region tends to deviate from the proper combustible region to the region above the upper limit line L5.

However, in the present embodiment, since the set of the target heat quantity of the burner 4 and the target value of the fan rotation speed is changed in the manner shown by the line AL4 of FIG. 7A, the actual heat quantity of the burner 4 and the actual combustion fan 11 are changed. As shown by the line AL5 in FIG. 7B, the actual air volume of the combustion fan 11 rapidly decreases toward the air volume on the line L3 (or an air volume close to it) at the initial stage of the change. On the other hand, the actual amount of change (decrease) in the amount of heat of the burner 4 at the initial stage is limited to the amount of change in a part of the total amount of change in the amount of heat from points P14 to P15.

Therefore, the amount of change in the amount of heat (decrease) at the initial stage of the change in the set of the actual amount of heat and the amount of air can be suppressed to a small amount of change, and the actual amount of air is reduced to some extent (and by extension, actually). The amount of change in the amount of heat at the stage where the amount of air in the above becomes the amount of air near the center between the line L5 on the upper limit side and the line L4 on the lower limit side of the proper combustible region) can be made a large amount of change.

As a result, the set of the actual amount of heat of the burner 4 and the actual amount of air of the combustion fan 11 is maintained within the proper combustible region (while the combustion state of the burner 4 is kept in a good state), and the amount of heat and the amount of heat are maintained. The set of air volume can be changed.

In the above description, the air supply / exhaust passage 10 is temporarily affected by an outside wind such as a gust when the air supply / exhaust passage 10 is not blocked (Rma2 = 1). The case where the degree of blockage of the air supply / exhaust passage 10 is temporarily increased has been described with reference to FIGS. 6A to 7B as an example. However, for example, when the air supply / exhaust passage 10 is clogged to some extent due to foreign matter such as dust, the degree of blockage of the air supply / exhaust passage 10 temporarily increases due to the action of outside wind on the air supply / exhaust passage 10. In this case, the same effect as described above can be obtained.

Supplementally, in the present embodiment, even in a state where the calorific value of the burner 4 is relatively large (for example, a state in which the target calorific value is set to be equal to or higher than the upper limit value Qmin_b of the calorific value lower limit correction value Qmin), due to the influence of an outside wind such as a gust. When the degree of blockage of the air supply / exhaust passage 10 increases or decreases (when the degree of blockage index value Rma2 increases or decreases), the calorific value lower limit correction value Qmin is corrected according to the calorific value lower limit correction coefficient RQmin in the same manner as described above. , The target value of the fan rotation speed is corrected according to the fan rotation correction coefficient Rma.

However, in a situation where the calorific value of the burner 4 is maintained above the upper limit value Qmin_b of the calorific value lower limit correction value Qmin, the correction of the calorific value lower limit correction value Qmin does not affect the target calorific value of the burner 4. Therefore, in such a situation, the correction process (update process) of the calorific value lower limit correction value Qmin may be omitted.

According to the present embodiment described above, not only the combustion operation of the burner 4 is performed with a relatively large amount of heat, but also the combustion operation of the burner 4 is performed with a small amount of heat (the target heat amount of the burner 4 is set). , The heat quantity is limited to the lower limit correction value Qmin, or the heat quantity is set to be close to the lower limit correction value Qmin), but the degree of blockage of the air supply / exhaust passage 10 is temporarily due to the influence of outside wind such as a gust of wind. When the number of burners is increased or decreased, good combustion operation of the burner 4 can be continued without causing a misfire of the burner 4.

Further, in the present embodiment, when the blockage degree index value Rma2 obtained in STEP 1 during the pre-purge operation before ignition of the burner 4 is equal to or higher than a predetermined value (when the determination result of STEP 3 is negative), the burner 4 is used. As the initial value of the calorific value lower limit correction coefficient RQmin (the value at the start of the combustion operation of the burner 4) in the combustion operation after ignition, the blockage degree index value Rma2 (> 1) obtained in STEP 1 is used.

For this reason, when the burner 4 is ignited in a situation where the outside wind is continuously blowing so that the degree of blockage of the air supply / exhaust passage 10 is relatively high (a state in which the determination result of STEP 3 is negative). The combustion operation of the burner 4 is started in a state where the calorific value lower limit correction value Qmin is set to a value larger than the rated minimum calorific value Qmin_a. Therefore, even if the above-mentioned outside wind acts on the air supply / exhaust passage 10 near the start of the combustion operation of the burner 4, misfire or poor combustion of the burner 4 may occur immediately after the start of the combustion operation of the burner 4. It can be effectively prevented.

The present invention is not limited to the embodiment of the above embodiment. For example, the heat quantity lower limit correction value Qmin and the target value of the fan speed are increased according to the increase in the degree of blockage of the air supply / exhaust passage 10 (the increase in the degree of blockage index value Rma2), or the air supply / exhaust passage 10 is blocked. The mode in which each of the calorific value lower limit correction value Qmin and the target value of the fan rotation speed is reduced according to the decrease in the degree (decrease in the blockage degree index value Rma2) may be different from the mode described in the above embodiment.

Specifically, when the degree of blockage is increased, the calorific value lower limit correction value Qmin and the target value of the fan rotation speed may be increased by a pattern as illustrated by the line AL7 with an arrow in FIG. 8A, for example. In this example, in the initial period in which the calorific value lower limit correction value Qmin and the target value of the fan speed are increased, the calorific value lower limit correction value Qmin is approached relatively quickly toward the value Qmin2 corresponding to the degree of blockage after the increase. On the other hand, the target value of the fan rotation speed is increased so as to approach the value N2 corresponding to the degree of blockage after the increase relatively gently. Then, after the calorific value lower limit correction value Qmin approaches the value Qmin2 corresponding to the degree of obstruction after the increase to some extent, the speed at which the calorific value lower limit correction value Qmin approaches the value Qmin2 corresponding to the degree of obstruction after the increase is reduced. At the same time, the speed at which the target value of the fan rotation speed approaches the value N2 corresponding to the degree of blockage after the increase is increased.

Further, in the initial period in which the calorific value lower limit correction value Qmin is increased, the fan rotation correction coefficient Rma is maintained at the value immediately before the increase in the degree of blockage without increasing, and the calorific value lower limit correction value Qmin approaches Qmin2 to some extent. After that, by increasing the fan rotation correction coefficient Rma, it is possible to increase the calorific value lower limit correction value Qmin and the target value of the fan rotation speed in the pattern illustrated by the line AL8 with an arrow in FIG. 8A. is there.

Further, when the degree of blockage is reduced, for example, the target values of the calorific value lower limit correction value Qmin and the fan rotation speed may be reduced by a pattern as illustrated by the line AL9 with an arrow in FIG. 8B. In this example, in the initial period in which the calorific value lower limit correction value Qmin and the target value of the fan rotation speed are decreased, the target value of the fan rotation speed is approached relatively quickly toward the value N1 corresponding to the degree of blockage of the decrease. On the other hand, the calorific value lower limit correction value Qmin is reduced so as to approach the value Qmin1 corresponding to the degree of blockage after the reduction relatively gently. Then, after the target value of the fan rotation speed approaches the value N1 corresponding to the degree of blockage after the decrease to some extent, the speed at which the target value of the fan rotation speed approaches the value N1 corresponding to the degree of blockage after the decrease. Is reduced, and the speed at which the calorific value lower limit correction value Qmin is brought closer to the value Qmin1 corresponding to the degree of obstruction after the increase is increased.

Further, in the initial period in which the target value of the fan rotation speed is decreased, the calorific value lower limit correction coefficient RQmin is maintained at the value immediately before the increase in the degree of blockage without decreasing, and the target value of the fan rotation speed is maintained to some extent. By reducing the calorific value lower limit correction coefficient RQmin after approaching N1, the calorific value lower limit correction value Qmin and the target values of the fan rotation speed are reduced in the pattern illustrated by the line AL10 with an arrow in FIG. 8B. It is also possible.

Further, in the above-described embodiment, the combustion device 2 provided in the water heater A has been described. However, the combustion device of the present invention is not limited to the combustion device 2 provided in the water heater A, and may be, for example, a combustion device provided in the FF type hot air heater. Further, the combustion device of the present invention is not limited to a combustion device that burns fuel gas, and may be a combustion device that vaporizes and burns liquid fuel such as kerosene.

2 ... Combustion device, 3a ... Combustion chamber, 4 ... Burner, 8 ... Proportional valve (fuel adjustment valve), 10a ... Air supply path, 10b ... Exhaust path, 11 ... Combustion fan, 41 ... Occlusion degree detection unit, 42 ... Combustion Operation control unit, 43 ... Calorific value lower limit adjustment unit.

Claims (3)

To the burner arranged in the combustion chamber, the air supply / exhaust passage communicating with the combustion chamber, the combustion fan for supplying the combustion air to the burner through the air supply passage of the air supply / exhaust passages, and the burner. A fuel regulating valve that adjusts the fuel supply amount, and during the combustion operation of the burner, the target heat amount of the burner is variably set within a predetermined variable range, and the rotation speed of the combustion fan is set according to the target heat amount. A combustion device including a combustion operation control unit that controls the fuel adjustment valve.
A blockage detection unit that detects the blockage of the air supply / exhaust passage,
During the combustion operation of the burner, the higher the degree of blockage detected, the larger the lower limit of heat quantity, which is the lower limit of the variable range of the target heat quantity, so that the variable range of the target heat quantity is increased according to the degree of blockage. and a heat lower limit adjusting unit that adjusts a
The combustion operation control unit is configured to control the rotation speed of the combustion fan corresponding to each value of the target calorific value to a higher rotation speed as the detected degree of closure increases.
Further, the combustion operation control unit and the calorific value lower limit adjusting unit increase the number of revolutions of the combustion fan and the calorific value lower limit, respectively, according to the detected increase in the degree of blockage during the combustion operation of the burner. After increasing the number of revolutions of the combustion fan, at least in the initial stage immediately after the start of the increase control process, the lower limit of the amount of heat is made to reach a value corresponding to the degree of closure after the increase. It is possible to realize the value earlier than reaching the value corresponding to the degree of blockage, and in the period in which the lower limit of the amount of heat is increased, the number of rotations of the combustion fan is increased in parallel with the increase of the lower limit of the amount of heat. A combustion apparatus characterized in that the number of revolutions of the combustion fan and the lower limit of the amount of heat are each increased in an increase pattern for increasing the amount of heat . To the burner arranged in the combustion chamber, the air supply / exhaust passage communicating with the combustion chamber, the combustion fan for supplying the combustion air to the burner through the air supply passage of the air supply / exhaust passages, and the burner. A fuel regulating valve that adjusts the fuel supply amount, and during the combustion operation of the burner, the target heat amount of the burner is variably set within a predetermined variable range, and the rotation speed of the combustion fan is set according to the target heat amount. A combustion device including a combustion operation control unit that controls the fuel adjustment valve.
A blockage detection unit that detects the blockage of the air supply / exhaust passage,
During the combustion operation of the burner, the higher the degree of blockage detected, the larger the lower limit of heat quantity, which is the lower limit of the variable range of the target heat quantity, so that the variable range of the target heat quantity is increased according to the degree of blockage. and a heat lower limit adjusting unit that adjusts a
The combustion operation control unit is configured to control the rotation speed of the combustion fan corresponding to each value of the target calorific value to a higher rotation speed as the detected degree of closure increases.
Further, the combustion operation control unit and the calorific value lower limit adjusting unit reduce the number of revolutions of the combustion fan and the calorific value lower limit, respectively, according to the detected decrease in the degree of blockage during the combustion operation of the burner. When executing the control process for causing the combustion, at least in the initial stage immediately after the start of the control process for the decrease, the lower limit of the calorific value is reduced so that the rotation speed of the combustion fan reaches a value corresponding to the degree of blockage after the decrease. It is possible to realize the value earlier than reaching the value corresponding to the degree of blockage, and during the period in which the lower limit of the amount of heat is decreased, the number of rotations of the combustion fan is in parallel with the decrease of the lower limit of the amount of heat. A combustion apparatus characterized in that the number of revolutions of the combustion fan and the lower limit of the amount of heat are each reduced in a reduction pattern for reducing the amount of heat . In the combustion apparatus according to claim 1 or 2 .
The blockage degree detection unit further has a function of detecting the blockage degree of the air supply / exhaust passage before ignition of the burner.
When the degree of blockage detected before the ignition of the burner is equal to or higher than a predetermined value, the calorific value lower limit adjusting unit of the burner according to the degree of blockage detected before the ignition. A combustion apparatus characterized in that it is configured to determine the lower limit value of the calorific value at the start of a combustion operation.