Combustion device

Abstract

To provide a combustion device capable of more properly performing correction control of the number of revolutions of a fan executed when exhaust resistance of a blast exhaust passage is increased than a conventional technology.SOLUTION: An exhaust resistance determination means 70 capable of determining the degree of exhaust resistance of the blowing exhaust passage 5; The rotation speed of the fan 4 is controlled so as to be a target rotation speed corresponding to the drive combustion degree of the burner 3. The control means (7) uses, as the upper limit correction rate, the upper limit correction rate (Xmax) as a variable value corresponding to the rotational speed of the fan (4), and each time the control means (7) executes the correction control, obtains the upper limit correction rate (Xmax) corresponding to the rotational speed of the fan (4) at that time and compares the upper limit correction rate (Xmax) with the correction rate (φ).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a combustion device used, for example, as a component of an instantaneous hot water supply device. [Background technology]

[0002] A specific example of a combustion device is described in Patent Document 1. The combustion apparatus described in the document includes a burner disposed in a combustion chamber that receives a supply of combustion air from a fan, an exhaust passage that includes the combustion chamber and directs the combustion air from the fan and the combustion gas generated by the burner to the outside, an exhaust resistance determining means that can determine the degree of exhaust resistance in the exhaust passage, and a control means that controls the rotation speed of the fan (the number of rotations per unit time) to a target rotation speed that corresponds to the degree of drive combustion of the burner. Furthermore, when a specific state occurs in which the exhaust resistance is greater than the exhaust resistance in a predetermined normal state, the control means executes correction control to increase the rotation speed of the fan by a predetermined correction rate, and this correction control is configured to be executed in stages multiple times.

[0003] With this configuration, even if a large gust of wind blows into the air supply and exhaust duct, temporarily increasing the exhaust resistance of the air supply and exhaust duct, the fan rotation speed is gradually corrected, so that when the gust of wind stops and the exhaust resistance decreases, the amount of combustion air supplied to the burner is prevented from becoming excessive, thereby reducing problems such as burner misfires.

[0004] However, the above-mentioned prior art still has room for improvement, as will be described below.

[0005] In the prior art, when correction control is performed to increase the fan rotation speed by a predetermined correction rate, an upper limit correction rate is set, which is the upper limit of the correction rate, and the correction rate is set to a value that does not exceed this upper limit correction rate. However, this upper limit correction rate is set to, for example, 1.2 (120%), a constant value regardless of the fan rotation speed. In other words, even though the fan rotation speed increases each time correction control is performed, in the prior art, the upper limit correction rate is set to a constant value regardless of the fan rotation speed. However, because the higher the fan rotation speed, the more likely it is that a burner misfire will occur, the upper limit correction rate should be set to a smaller value than when the fan rotation speed is low. Therefore, the upper limit correction rate set in the prior art cannot be said to be an appropriate value that fully takes into account changes in the fan rotation speed, and there is still a risk that the correction control will cause the fan rotation speed to become excessively high. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 3029547 [Patent Document 2] Patent No. 3701602 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention was conceived in light of the above-mentioned circumstances, and its object is to provide a combustion device that can more appropriately perform correction control of the fan rotation speed, which is executed when the exhaust resistance of the air supply and exhaust passage increases, than conventional technology. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides the following technical solutions.

[0009] A combustion device provided by the present invention comprises a fan, a burner disposed in a combustion chamber that receives a supply of combustion air from the fan, an air supply and exhaust passage that includes the combustion chamber and directs the combustion air from the fan and the combustion gas generated by the burner to the outside, exhaust resistance determination means that can determine the degree of exhaust resistance of the air supply and exhaust passage, and control means that, while the burner is driven and burning, controls the rotation speed of the fan to a target rotation speed that corresponds to the degree of driving and combustion of the burner, and, when a specific state occurs in which the exhaust resistance is greater than the exhaust resistance in a predetermined normal state, executes correction control to increase the rotation speed of the fan by a correction rate that is equal to or less than a predetermined upper limit correction rate, wherein the upper limit correction rate is a variable upper limit correction rate that corresponds to the rotation speed of the fan, and the control means is configured to determine the upper limit correction rate that corresponds to the rotation speed of the fan at that time each time it executes the correction control, and compare this upper limit correction rate with the correction rate. The combustion apparatus according to the present invention can be configured as an indoor-installed combustion apparatus in which the exhaust port at the end of the air supply and exhaust passage is set to communicate with the outdoors, and the combustion apparatus main body equipped with the fan and the burner is installed indoors.

[0010] According to the above configuration, the following effects can be obtained. That is, when a specific condition occurs in which the exhaust resistance of the air supply / exhaust passage is greater than the exhaust resistance under a predetermined normal condition, correction control is performed to increase the fan rotation speed by a predetermined correction factor, thereby increasing the amount of combustion air supplied to the burner, but this correction factor is set to be equal to or less than the upper limit correction factor. Unlike Patent Document 1, the upper limit correction factor is not a constant value unrelated to the fan rotation speed, but a variable value corresponding to the fan rotation speed. Furthermore, each time correction control of the fan rotation speed is performed, an upper limit correction factor corresponding to the fan rotation speed at that time is calculated, and the correction factor is limited to or less than this upper limit correction factor. Therefore, according to the present invention, it is possible to more accurately prevent the correction factor from becoming unduly large than in the prior art and to prevent the fan rotation speed from increasing more than necessary. As a result, this is even more advantageous in preventing problems such as burner misfires due to excessive air flow to the burner.

[0011] In the present invention, preferably, when the specific state occurs during the driving and combustion of the burner, and the correction rate of the fan rotation speed required to deal with the specific state exceeds the upper limit correction rate, the driving and combustion of the burner is stopped.

[0012] With this configuration, if the exhaust resistance in the air supply and exhaust passage is too great and there is a risk of a so-called exhaust backflow abnormality, the burner combustion is stopped, thereby improving the safety of the combustion device.

[0013] In the present invention, preferably, when executing the correction control, the control means is configured to execute the correction control in succession in a plurality of steps, thereby gradually bringing the rotation speed of the fan closer to the target rotation speed, and to determine the upper limit correction factor corresponding to the rotation speed of the fan at each of the plurality of executions of the correction control, and to compare this upper limit correction factor with the correction factor.

[0014] With this configuration, when corrective control of the fan rotation speed is executed, this correction control is executed in stages over multiple times, and the fan rotation speed can be brought closer to the target rotation speed in stages. At this time, when the correction control is executed multiple times, an upper limit correction factor corresponding to the fan rotation speed at that time is calculated individually, and this upper limit correction factor is compared with the correction factor, so that the correction factor can be more appropriately prevented from becoming an unreasonably large value. As a result, even if For example, even if the exhaust resistance of the air supply and exhaust passage increases suddenly temporarily due to a sudden wind blowing into the air supply and exhaust passage, the amount of air sent from the fan to the burner is appropriately prevented from becoming excessive.

[0015] In the present invention, preferably, when the burner changes from a driven combustion state to a stopped state, the fan is configured to perform a post-purge, and if the specific state occurs during the driven combustion of the burner and the driven combustion of the burner is then stopped, the air volume of the post-purge is made larger or the air time is made longer than in the case where the driven combustion of the burner is stopped without the specific state occurring. Here, "post-purge" refers to the operation in which a fan blows air into the exhaust duct after the burner stops operating and burning, in order to forcibly expel unburned gases and exhaust gases present in the exhaust duct to the outside of the exhaust duct.

[0016] This configuration provides the following effects. In other words, if the specific condition occurs during burner combustion and then the burner combustion stops, there is a high possibility that a large amount of unburned gas and exhaust gas will remain in the air supply and exhaust passage compared to when the burner combustion stops without the specific condition occurring.In contrast, with the above configuration, in the former case, the post-purge air volume is large or the air supply time is long, so that the unburned gas and exhaust gas can be properly discharged outside the air supply and exhaust passage.

[0017] In the present invention, preferably, the post-purge in the case where the specific state occurs during the burner's operation and combustion and the burner's operation is subsequently stopped includes a first post-purge that is executed when the burner's operation and combustion is stopped because the correction rate of the fan's rotation speed exceeds the upper limit correction rate, and a second post-purge that is executed when the burner's operation and combustion is stopped without the correction rate exceeding the upper limit correction rate, and the first post-purge has a larger air volume or a longer air-blowing time than the second post-purge.

[0018] This configuration provides the following effects. That is, when the first post-purge is performed, it is considered that an abnormality in exhaust backflow in the air supply / exhaust passage or a similar phenomenon has occurred. Also, when the second post-purge is performed, it is considered that the degree of exhaust backflow or the like is smaller than when the first post-purge is performed. On the other hand, the first post-purge has a larger air supply volume or a longer air supply time than the second post-purge, so a post-purge that appropriately corresponds to the degree of the phenomenon described above is performed.

[0019] Other features and advantages of the present invention will become more apparent from the following description of the preferred embodiments of the invention, which proceeds with reference to the accompanying drawings. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is an explanatory diagram showing an example of a water heater equipped with a combustion device according to the present invention. [Figure 2] 2 is a flowchart showing an example of an operation control procedure executed in the combustion apparatus of FIG. 1. [Figure 3] 10 is a graph showing an example of the relationship between the rotation speed of a fan and an upper limit correction rate. DETAILED DESCRIPTION OF THE INVENTION

[0021] Preferred embodiments of the present invention will now be described in detail with reference to the drawings.

[0022] The combustion device C shown in Figure 1 is an indoor hot water heater WH. This is a stationary combustion device. The hot water heater WH is configured such that a heat exchanger 1 for heating hot water is housed in a boiler body 2 of a combustion device C, and hot water sent to this heat exchanger 1 is heated by the combustion device C, and this heated hot water is then discharged from the heat exchanger 1 to the desired hot water supply destination.

[0023] The combustion device C includes a burner 3 disposed within the can body 2, a fan 4 for supplying combustion air into the can body 2, an exhaust duct 6 connected to the can body 2, and a control unit .

[0024] Burner 3 is a gas burner that burns fuel gas, and is configured by combining multiple combustion tubes (burner bodies) that can burn fuel gas individually, for example. Therefore, by switching the number of combustion tubes used for combustion, the overall combustion capacity of burner 3 can be switched between four levels, for example, combustion capacity 1 to 4. Symbol V1 in Fig. 1 indicates an on-off valve that can switch on and off the supply of fuel gas to burner 3.

[0025] The fan 4 is driven by a fan motor M and is capable of supplying combustion air toward a combustion chamber 5a, which is an area in the can body 2 where the burner 3 is installed. The interior of the can body 2 (including the combustion chamber 5a) and the interior of the exhaust duct 6 form an air supply and exhaust path 5 for guiding and discharging the combustion air supplied from the fan 4 and the combustion gas generated by the burner 3 to the outdoors. The combustion device main body Ca, which includes the fan 4, burner 3, and can body 2, is installed indoors 9a, but the exhaust port 5b at the end of the exhaust duct 6 is designed to communicate with the outdoors.

[0026] The combustion device C includes, as components related to the fan 4, a rotation speed detection unit 80, a drive current detection unit 81, and a motor control unit . The motor control unit 82 is a component equivalent to a motor driver that drives and controls the fan motor M, and the rotation speed of the fan 4 is controlled by the control unit 7 via this motor control unit 82. The rotation speed detection unit 80 can detect the rotation speed of the fan 4 using a rotation sensor (not shown) that uses a Hall element or the like. The drive current detection unit 81 can detect the drive current of the fan motor M.

[0027] Control unit 7 corresponds to a specific example of the control means of the present invention, and is configured using a microcomputer or the like, and controls the operation of each part of water heater WH (including combustion device C) and processes various data. Control unit 7 also has an exhaust resistance determination unit 70 (a specific example of the exhaust resistance determination means of the present invention), and stores data Da on the upper limit correction rate, etc.

[0028] The exhaust resistance determination unit 70 is capable of determining the degree of exhaust resistance in the air supply / exhaust path 5. This exhaust resistance determination unit 70 stores basic data indicating the correlation between the target rotation speed Nt of the fan 4, which is set in normal conditions when the exhaust resistance in the air supply / exhaust path 5 is below a predetermined level, and the drive current It (target current) of the fan motor M. Even if the rotation speed of the fan 4 is constant, if the exhaust resistance in the air supply / exhaust path 5 is high, the amount of work done by the fan 4 decreases, and the actual drive current Ia of the fan motor M decreases. Based on this behavior, if a situation occurs in which the actual drive current Ia of the fan motor M is less than the drive current It (target current) in the basic data, it is determined that the exhaust resistance is higher than normal. Furthermore, the greater the difference between the drive currents Ia and It, the greater the increase in exhaust resistance is determined to be. An increase in exhaust resistance occurs, for example, when a ventilation fan (not shown) in the room 9a is operated and the room 9a becomes negative pressure, or when wind blows into the exhaust port 5b of the air supply and exhaust path 5.

[0029] The control unit 7 controls the rotation speed of the fan 4 to a target rotation speed Nt corresponding to the degree of combustion of the burner 3 while the burner 3 is being driven. However, when a specific state occurs in which the exhaust resistance of the air supply and exhaust passage 5 is greater than the exhaust resistance in a predetermined normal state, the control unit 7 controls the rotation speed of the fan 4 to a target rotation speed Nt corresponding to the degree of combustion of the burner 3. Correction control is executed to increase the rotation speed at a correction rate φ equal to or less than a predetermined upper limit correction rate Xmax, the details of which will be described later.

[0030] Next, an example of an operation control procedure executed in the combustion device C and the hot water supply device WH will be described with reference to the flowchart shown in FIG. 2, and the operation thereof will also be described.

[0031] First, when the burner 3 is being driven and burning, the fan 4 is driven and its actual rotation speed Na is controlled to be equal to the target rotation speed Nt corresponding to the degree of burning of the burner 3 (S1: YES, S2). During this control, the drive current It (target current) of the fan motor M in the basic data is compared with the actual drive current Ia at the current time (S3). If this comparison does not establish the relationship It > Ia, it is considered that there is no increase in exhaust resistance, and if the burner 3 is continuing to be driven and burning, the process returns to step S2 (S3: NO, S10: NO, S2).

[0032] In contrast to this, for example, if the terminal of the hot water supply destination is closed and the flow of hot water in the heat exchanger 1 is stopped, and the driving combustion of the burner 3 is stopped in response, a normal post-purge is performed (S10: YES, S11). Here, the definition of post-purge itself has been described above, but in this embodiment, it is the air blowing operation of fan 4 intended to forcibly exhaust unburned gas and exhaust gas present in air supply and exhaust path 5 to the outdoors. The normal post-purge executed in step S11 has a smaller air blowing volume or a shorter air blowing time than the first and second post-purges described below.

[0033] On the other hand, unlike the above-described case, if the specific state occurs during driving combustion of the fan 4, in step S3, the drive current It (target current) of the fan motor M and the actual drive current Ia at the current time have a relationship of It>Ia (S3: YES). In this case, correction control is executed to increase the rotation speed Na of the fan 4 by a predetermined correction factor φ (S4). Here, the correction control is originally performed for the purpose of setting the rotation speed Na of the fan 4 to a target rotation speed Nt that offsets the effect of increased exhaust resistance and obtains an amount of combustion air blown corresponding to the degree of drive combustion of the burner 3.

[0034] However, in this embodiment, as described below, the correction control is executed multiple times in succession so that the rotation speed Na of the fan 4 gradually approaches the final target rotation speed Nt. Furthermore, during each of the multiple executions of the correction control, an upper limit correction factor Xmax corresponding to the rotation speed Na of the fan 4 at that time is calculated, and this upper limit correction factor Xmax is compared with the correction factor φ.

[0035] Specifically, the first correction control of the fan rotation speed Na in step S4 is performed by increasing the actual drive current Ia at the current time by, for example, a predetermined number α. The correction factor φ in this case is φ=(Ia+α) / Ia. The predetermined number α is a relatively small value, such as 1% of the drive current Ia, that prevents the rotation speed Na of the fan 4 from reaching the target rotation speed Nt in a single correction control. Note that the predetermined number α can be set to a larger value, for example, as the exhaust resistance increases, and can also be a variable value rather than a constant value.

[0036] If the burner 3 continues to be driven and burned after the first correction control in step S4 is completed, an upper limit correction factor Xmax corresponding to the rotation speed Na of the fan 4 increased by the correction control is calculated (S5: YES, S6). This upper limit correction factor Xmax is the upper limit of the correction factor φ. In this combustion device C, the correction factor φ is set to a specification such that it cannot be set to a value that exceeds the upper limit correction factor Xmax. The control unit 7 stores data such as that shown in the following Table 1 as data Da for the upper limit correction rate for calculating the upper limit correction rate Xmax.

[0037] [Table 1]

[0038] The data shown in Table 1 is for the case where a negative pressure in the room 9a is, for example, -200 Pa due to the operation of a ventilation fan (not shown) for the room 9a, causing exhaust resistance in the air supply and exhaust path 5. Table 1 provides specific values ​​for the minimum rotation speed Fa (n1 to n4 rpm) and the maximum rotation speed Fb (n11 to n14 rpm) of the fan 4 when the burner 3 is at combustion capacities 1 to 4. Table 1 also provides specific values ​​for the upper limit correction factor Xmax (m1 to m4%) when the fan 4 is at the minimum rotation speed Fa, and the upper limit correction factor Xmax (m11 to m14%) when the fan 4 is at the maximum rotation speed Fb. To give an example of specific values, when the burner 3 is at combustion capacity 4, the minimum rotation speed Fa (n4) of the fan 4 is 2500 rpm, and the maximum rotation speed Fb (n14) is 4500 rpm. Furthermore, the upper limit correction rate Xmax has a value m4 of 130% when the rotation speed of the fan 4 is the minimum rotation speed Fa, and a value m4 of 115% when the rotation speed is the maximum rotation speed Fb. Specific values ​​of such data can be determined, for example, by experimentation, as optimal values ​​or preferable values ​​close to the optimal values.

[0039] The upper limit correction rate Xmax can be calculated, for example, by the following formula (1).

[0040]

number

[0041] In the right-hand side of equation (1), element F is the actual rotation speed Na of the fan 4 at the current time, and the other elements Xa, Xb, Fa, and Fb match the data shown in Table 1.

[0042] The formula (1) corresponds to the formula for line L shown in Fig. 3 (however, line L is an example of data corresponding to combustion capacity 4 of burner 3. In the cases of combustion capacities 1 to 3, the specific values ​​of Fa, Fb, Xa, and Xb differ, and therefore the start and end points and slope of line L will also differ). Instead of determining the upper limit correction factor Xmax by calculation, the control unit 7 can be configured to store data corresponding to line L in Fig. 3, for example, and determine the upper limit correction factor Xmax based on this data.

[0043] After the upper limit correction rate Xmax is calculated in step S6, this upper limit correction rate Xmax is compared with the correction rate φ for the rotation speed Na of the fan 4, and if the relationship φ>Xmax is not satisfied, the process returns to step S3, and the above-described operations from step S3 onwards are repeated. In this repeated process, the rotation speed Na of the fan 4 is further increased according to the correction control in the second step S4, so in the second step S6, the upper limit correction rate Xmax corresponding to that rotation speed Na is calculated, and then the process proceeds to the second step S7. When steps S3 to S7 are repeated multiple times, the operation control procedure becomes one of the following first to third operation patterns.

[0044] The first operating pattern is a case where step S3 returns NO (the drive current It (target current) and the actual drive current Ia at the current time are not greater than Ia) when the correction control of the fan 4 rotation speed Na is executed multiple times and the correction factor φ does not exceed the upper limit correction factor Xmax. In this first operating pattern, the rotation speed Na of the fan 4 is appropriately increased in response to an increase in exhaust resistance, preventing a shortage in the amount of combustion air supplied to the burner 3. Furthermore, since the upper limit correction factor Xmax is calculated each time the correction control is executed multiple times and the correction factor φ is within a range that does not exceed the upper limit correction factor Xmax, the rotation speed Na of the fan 4 does not become excessively high. The above-described correction control of the fan 4 is executed multiple times, and the rotation speed Na of the fan 4 gradually approaches the target rotation speed Nt. Therefore, a smaller value can be used as the correction factor φ, enabling fine-tuned correction control. It is also possible to easily prevent the correction factor φ from exceeding the upper limit correction factor Xmax. As mentioned above, if step S3 becomes NO and the burner 3 continues to be driven and burned (S10: YES), the process returns to step S2, and control is executed to return the rotation speed Na of the fan 4 to the original target rotation speed Nt.

[0045] The second operating pattern occurs when step S3 remains YES and step S7 returns YES (the correction factor φ and the upper limit correction factor Xmax of the fan 4 rotation speed Na are in a relationship of φ>Xmax) even though the correction control of the fan 4 rotation speed Na has been executed multiple times. In this case, not only is it determined that the increase in the amount of combustion air supplied is not commensurate with the increase in exhaust resistance of the air supply and exhaust passage 5, but also that an exhaust backflow abnormality has occurred. Therefore, when this second operating pattern occurs, the burner 3 is forcibly stopped from driving and burning (S7: YES, S8). This ensures that the combustion device C is appropriately protected.

[0046] After the burner 3 is forcibly stopped as described above, a first post-purge is executed (S9). In this first post-purge, the rotation speed Na of the fan 4 is increased, and the airflow rate (per unit time) of the fan 4 is increased, or the airflow time is lengthened, compared to the normal post-purge in step S11 described above. This ensures that unburned gas and exhaust gas in the air supply and exhaust path 5 are forcibly discharged outdoors in an appropriate manner.

[0047] The third pattern occurs when, despite the execution of correction control, for example, the hot water supply terminal is closed, causing the burner 3 to stop operating and burning midway (S5: NO). In this case, a second post-purge is executed after the burner 3 stops operating and burning (S12). In this second post-purge, similar to the first post-purge described above, compared to a normal post-purge, the rotation speed Na of the fan 4 is increased, the fan 4's airflow rate (per unit time) is increased, or the airflow time is lengthened. The third pattern is also premised on the occurrence of a phenomenon in which exhaust resistance is increased, and therefore the second post-purge can appropriately remove unburned gas and exhaust gas from the air supply and exhaust path 5. However, compared to the first post-purge, the second post-purge has a smaller airflow rate (per unit time) or a shorter airflow time. This prevents the fan 4 from rotating at an unnecessarily high speed or operating for an unnecessarily long time during the second post-purge. It is possible.

[0048] The present invention is not limited to the above-described embodiment, and the specific configuration of each part of the combustion device according to the present invention can be freely modified in various ways within the intended scope of the present invention.

[0049] In the above-described embodiment, the correction factor φ is set small and the correction control is executed multiple times, but the present invention is not limited to this. The correction control may be executed once to ensure an airflow rate commensurate with the increase in exhaust resistance of the air supply / exhaust passage 5, and the correction control may not be executed from the second time onwards.

[0050] The data for the upper limit correction rate Xmax shown in Table 1 and Fig. 3 above is data when the indoor temperature 9a where the combustion device C is installed is set to -200 Pa, but is not limited to this. The upper limit correction rate Xmax under conditions different from those described above may also be used. A specific value for the upper limit correction rate Xmax different from that in the above-described embodiment may also be used.

[0051] In the above-described embodiment, the magnitude of the exhaust resistance of the air supply / exhaust path 5 is determined using the driving current of the fan motor M, but the present invention is not limited to this, and it can also be determined using, for example, the driving power of the fan motor M. The combustion apparatus according to the present invention is not limited to a hot water supply apparatus combined with a heat exchanger, but can also be used as a combustion apparatus for heating or an incinerator, for example. The present invention is best suited for, but not limited to, indoor combustion devices. [Explanation of symbols]

[0052] WH water heater C. Combustion device Ca combustion device main body M Fan Motor Xmax upper limit correction factor φ correction factor 1 heat exchanger 2 can body 3 Burner 4 Fans 5. Ventilation and exhaust duct 5a Combustion chamber 5b Exhaust port 6 Exhaust duct 7 Control section (control means) 70 Exhaust resistance determination unit (exhaust resistance determination means) 9a indoor

Claims

1. With fans, a burner disposed in the combustion chamber that receives a supply of combustion air from the fan; an air supply and exhaust path including the combustion chamber and directing the combustion air from the fan and the combustion gas generated by the burner to the outside; an exhaust resistance determining means for determining the degree of exhaust resistance of the air supply / exhaust passage; a control means for controlling the rotational speed of the fan to a target rotational speed corresponding to the degree of driving and combustion of the burner during driving and combustion of the burner, and for executing correction control for increasing the rotational speed of the fan by a correction rate equal to or lower than a predetermined upper limit correction rate when a specific state occurs in which the exhaust resistance is greater than the exhaust resistance in a predetermined normal state; A combustion device comprising: As the upper limit correction rate, an upper limit correction rate as a variable value corresponding to the rotation speed of the fan is used, The combustion device is characterized in that the control means is configured to calculate the upper limit correction factor corresponding to the rotation speed of the fan at that time each time the correction control is executed, and to compare this upper limit correction factor with the correction factor.

2. The combustion device according to claim 1, The combustion device is configured such that, when the specific state occurs during driving and combustion of the burner, the driving and combustion of the burner is stopped if the correction rate of the rotation speed of the fan required to deal with the specific state exceeds the upper limit correction rate.

3. The combustion device according to claim 1, The control means is configured to, when executing the correction control, successively execute the correction control multiple times to gradually bring the rotation speed of the fan closer to the target rotation speed, and to determine the upper limit correction factor corresponding to the rotation speed of the fan at each time of executing the correction control multiple times, and compare this upper limit correction factor with the correction factor.

4. A combustion device according to any one of claims 1 to 3, When the burner transitions from a driven combustion state to a stopped state, the fan is configured to perform a post-purge; A combustion device configured such that, when the specific state occurs during the burner's combustion and the burner's combustion is subsequently stopped, the post-purge airflow volume is greater or the airflow time is longer than when the burner's combustion is stopped without the specific state occurring.

5. The combustion device according to claim 4, As the post-purging in the case where the specific state occurs during the driven combustion of the burner and the driven combustion of the burner is stopped thereafter, a first post-purge that is executed when the burner stops being driven and burning due to the correction rate of the rotation speed of the fan exceeding the upper limit correction rate, and a second post-purge that is executed when the burner stops being driven and burning without the correction rate exceeding the upper limit correction rate, A combustion device, wherein the first post-purge has a larger air blowing amount or a longer air blowing time than the second post-purge.

6. The combustion device according to claim 1, The exhaust port at the end of the air supply and exhaust path is set to communicate with the outdoors, and the fan and and a combustion device main body including the burner is configured as an indoor installation type combustion device that is installed indoors.

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