COMBUSTION DEVICE AND HOT WATER DEVICE INCLUDING SAME

Abstract

A combustion device includes a fan; a premixing device capable of generating an air-fuel mixture by driving the fan; and an ignition device capable of ignition operation for the air-fuel mixture in a combustion chamber. The premixing device includes a flapper capable of opening and closing a part of a gas flow path and has a larger opening degree when the drive speed of the fan is high speed than low speed. The ignition operation for the air-fuel mixture by the ignition device is a standard ignition operation in principle, executed in a first drive speed range of the fan in which the flapper is in an open state, and exceptionally a non-standard ignition operation, executed in a second drive speed range of the fan in which the flapper is in a closed state in the case where the air-fuel mixture is not ignited by the standard ignition operation.

Claims

1. A combustion device, comprising: a variable-speed fan; a premixing device having a gas flow path through which air flows internally by driving of the variable-speed fan, and a fuel gas outlet communicating with the gas flow path, in which fuel gas flows out from the fuel gas outlet into the gas flow path by negative pressure when the air flows through the gas flow path, and capable of generating an air-fuel mixture of the air and the fuel gas; a combustion chamber positioned on an exhaust side of the variable-speed fan so as to receive supply of the air-fuel mixture, and for combusting the air-fuel mixture; and an ignition device capable of ignition operation for the air-fuel mixture in the combustion chamber, wherein the premixing device includes a flapper capable of opening and closing a part of the gas flow path, and an opening degree of the flapper is larger in a case of a drive speed of the variable-speed fan being high speed than in a case of being low speed, and the ignition operation for the air-fuel mixture by the ignition device is configured as: a standard ignition operation in principle, which is executed in a first drive speed range of the variable-speed fan in which the flapper is in an open state, and exceptionally a non-standard ignition operation, which is executed in a second drive speed range of the variable-speed fan in which the flapper is in a closed state in a case where the air-fuel mixture is not ignited by the standard ignition operation.

2. The combustion device according to claim 1, wherein the non-standard ignition operation is configured to be executed in a state where the drive speed of the variable-speed fan is set to a highest speed range of the second drive speed range.

3. The combustion device according to claim 1, wherein the first drive speed range includes a specific speed range in which the flapper is in a partially open state, and the standard ignition operation is configured to be executed in a state where the drive speed of the variable-speed fan is set to a highest speed range of the specific speed range, or a speed range equal to or higher than the highest speed range.

4. The combustion device according to claim 1, wherein in a case where the ignition operation for the air-fuel mixture is executed, the standard ignition operation is executed a number of times equal to or less than a predetermined first upper-limit number of times until the air-fuel mixture is ignited, and in a case where the air-fuel mixture is not ignited regardless of the standard ignition operation being executed the first upper-limit number of times, the non-standard ignition operation is executed thereafter.

5. The combustion device according to claim 4, wherein in a case where the standard ignition operation is executed a plurality of times repeatedly, the drive speed of the variable-speed fan gradually increases.

6. The combustion device according to claim 1, wherein in a case where the air-fuel mixture is not ignited regardless of the non-standard ignition operation being executed repeatedly for a predetermined second upper-limit number of times, it is determined that an abnormality has occurred, and no ignition operations continuously executed thereafter.

7. The combustion device according to claim 1, wherein in a case where the standard ignition operation and/or the non-standard ignition operation is executed repeatedly, an interval period is secured, and during the interval period, the variable-speed fan is driven at a higher speed than a drive speed during the standard ignition operation and the non-standard ignition operation, and a scavenging process of the combustion chamber is executed.

8. The combustion device according to claim 1, comprising: a setting part capable of selecting and setting a specific ignition operation mode as the ignition operation for the air-fuel mixture, wherein in a case where the specific ignition operation mode is set in the setting part, the standard ignition operation is omitted in executing the ignition operation for the air-fuel mixture and the non-standard ignition operation is executed.

9. A hot water device, comprising: a combustion device; and a heat exchanger capable of heating hot water using combustion gas generated by the combustion device, wherein the combustion device according to claim 1 is configured as the combustion device.

10. A hot water device, comprising: a combustion device; and a heat exchanger capable of heating hot water using combustion gas generated by the combustion device, wherein the combustion device according to claim 2 is configured as the combustion device.

11. A hot water device, comprising: a combustion device; and a heat exchanger capable of heating hot water using combustion gas generated by the combustion device, wherein the combustion device according to claim 3 is configured as the combustion device.

12. A hot water device, comprising: a combustion device; and a heat exchanger capable of heating hot water using combustion gas generated by the combustion device, wherein the combustion device according to claim 4 is configured as the combustion device.

13. A hot water device, comprising: a combustion device; and a heat exchanger capable of heating hot water using combustion gas generated by the combustion device, wherein the combustion device according to claim 5 is configured as the combustion device.

14. A hot water device, comprising: a combustion device; and a heat exchanger capable of heating hot water using combustion gas generated by the combustion device, wherein the combustion device according to claim 6 is configured as the combustion device.

15. A hot water device, comprising: a combustion device; and a heat exchanger capable of heating hot water using combustion gas generated by the combustion device, wherein the combustion device according to claim 7 is configured as the combustion device.

16. A hot water device, comprising: a combustion device; and a heat exchanger capable of heating hot water using combustion gas generated by the combustion device, wherein the combustion device according to claim 8 is configured as the combustion device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1 is a schematic explanatory diagram illustrating an example of a hot water device including a combustion device according to the disclosure.

[0018] FIG. 2 is an external perspective diagram of a premixing device of the combustion device illustrated in FIG. 1.

[0019] FIG. 3 is an exploded perspective diagram of FIG. 2.

[0020] FIG. 4A is a cross-sectional diagram of the premixing device illustrated in FIG. 2 in a flapper closed state, FIG. 4B is a cross-sectional diagram at a position different from FIG. 4A, and FIG. 4C is a cross-sectional diagram taken along line IVc-IVc of FIG. 4B.

[0021] FIG. 5A is a cross-sectional diagram of the premixing device illustrated in FIG. 2 in a flapper fully open state, and FIG. 5B is a cross-sectional diagram at a position different from FIG. 5A.

[0022] FIG. 6A is a plan diagram of a premixing flow path forming member of the premixing device illustrated in FIG. 2, FIG. 6B is an enlarged diagram of a main portion thereof, and FIG. 6C is a plan cross-sectional diagram of FIG. 6A.

[0023] FIG. 7 is a graph illustrating an example of a relationship between a drive speed of a fan of the combustion device illustrated in FIG. 1 and CO.sub.2 concentration in combustion gas.

[0024] FIG. 8 is a flowchart illustrating an example of an operation procedure executed in a hot water device including the combustion device illustrated in FIG. 1.

[0025] (a) to (c) of FIG. 9 are time charts illustrating an example of a control mode relating to an ignition device, a fan, and abnormality determination in the combustion device illustrated in FIG. 1.

[0026] (a) to (c) of FIG. 10 are time charts illustrating another example of a control mode relating to an ignition device, a fan, and abnormality determination in the combustion device illustrated in FIG. 1.

[0027] FIG. 11 is a flowchart illustrating another example of an operation procedure executed in a hot water device including the combustion device illustrated in FIG. 1.

[0028] FIG. 12 is a schematic explanatory diagram illustrating another example of a hot water device including a combustion device according to the disclosure.

DESCRIPTION OF THE EMBODIMENTS

[0029] A combustion device provided by a first aspect of the disclosure includes a variable-speed fan; a premixing device having a gas flow path through which air flows internally by driving of the fan, and a fuel gas outlet communicating with the gas flow path, in which fuel gas flows out from the fuel gas outlet into the gas flow path by negative pressure when the air flows through the gas flow path, and capable of generating an air-fuel mixture of the air and the fuel gas; a combustion chamber positioned on an exhaust side of the fan so as to receive supply of the air-fuel mixture, and for combusting the air-fuel mixture, and an ignition device capable of ignition operation for the air-fuel mixture in the combustion chamber. The premixing device includes a flapper capable of opening and closing a part of the gas flow path, and an opening degree of the flapper is larger in a case of a drive speed of the fan being high speed than in a case of being low speed. The ignition operation for the air-fuel mixture by the ignition device is configured as: a standard ignition operation in principle, which is executed in a first drive speed range of the fan in which the flapper is in an open state, and exceptionally a non-standard ignition operation, which is executed in a second drive speed range of the fan in which the flapper is in a closed state in a case where the air-fuel mixture is not ignited by the standard ignition operation.

[0030] According to such a configuration, the following effects are obtained.

[0031] That is, the ignition operation for the air-fuel mixture by the ignition device is, in principle, a standard ignition operation executed in a first drive speed range of the fan in which the flapper is in an open state. During the standard ignition operation, a large amount of air may be made to flow through the gas flow path of the premixing device, and a large amount of air-fuel mixture may be generated by mixing fuel gas in an amount commensurate with the air amount with the air. Thus, by causing ignition of the air-fuel mixture by the standard ignition operation, it becomes possible to immediately realize drive combustion with large combustion power in the combustion chamber. As a result, in the case where the combustion device according to the disclosure is used for hot water heating applications of hot water supply devices, for example, it has the advantage of being able to heat hot water very quickly up to a predetermined hot water supply temperature.

[0032] On the other hand, in the case where ignition of the air-fuel mixture by the aforementioned standard ignition operation fails, as an exceptional ignition operation, a non-standard ignition operation executed in a second drive speed range of the fan in which the flapper is in a closed state is executed. During the non-standard ignition operation, air does not flow through a part of the gas flow path, and an air-fuel mixture is generated by mixing fuel gas with a small amount of air flowing through other portions.

[0033] Thus, by making the air-fuel mixture in a fuel-rich state, the ignitability of the air-fuel mixture can be improved. Even in the case where emergency gas, which is a mixture of approximately 50% each of LP gas and air, for example, is used as the fuel gas, it can be suitably handled.

[0034] According to the disclosure, the standard ignition operation and the non-standard ignition operation have a difference in whether the flapper of the premixing device is in an open state or a closed state. Thus, unlike Patent Document 2 which merely changes the rotation speed of the fan, in the standard ignition operation and the non-standard ignition operation, the mixing ratio of air and fuel gas and the generation amount of the entire air-fuel mixture are clearly different, and it is possible to accurately achieve securing excellent combustion response performance by the standard ignition operation and significant improvement of ignition performance by the non-standard ignition operation.

[0035] In the disclosure, preferably, the non-standard ignition operation is configured to be executed in a state where the drive speed of the fan is set to a highest speed range of the second drive speed range.

[0036] According to such a configuration, the following effects are obtained.

[0037] That is, in the case where the fan is in the second drive speed range, a part of the gas flow path is in a closed state by the flapper, so an air-fuel mixture of fuel gas and air is generated only in other portions of the gas flow path. Under such circumstances, in response to the fan being set to the highest speed range of the second drive speed range and negative pressure in the other portions of the gas flow path is strengthened, the fuel gas outflow amount to the portions increases. Thus, it becomes more preferable for making the air-fuel mixture fuel-rich and enhancing the ignition performance during the non-standard ignition operation.

[0038] In the disclosure, preferably, the first drive speed range includes a specific speed range in which the flapper is in a partially open state, and the standard ignition operation is configured to be executed in a state where the drive speed of the fan is set to a highest speed range of the specific speed range, or a speed range equal to or higher than the highest speed range.

[0039] According to such a configuration, the standard ignition operation is executed in a situation where the flapper is in a partially open state with a large opening degree close to fully open, or in a situation where the flapper is in a fully open state. That is, the standard ignition operation is not executed in a situation where the opening degree of the flapper is small. Thus, the standard ignition operation becomes an ignition operation that may be clearly distinguished from the non-standard ignition operation, and this becomes more preferable for improving combustion response performance by the standard ignition operation.

[0040] In the disclosure, preferably, in a case where the ignition operation for the air-fuel mixture is executed, the standard ignition operation is executed a number of times equal to or less than a predetermined first upper-limit number of times until the air-fuel mixture is ignited, and in a case where the air-fuel mixture is not ignited regardless of the standard ignition operation being executed the first upper-limit number of times, the non-standard ignition operation is executed thereafter.

[0041] According to such a configuration, the procedure of the ignition operation for the air-fuel mixture can be made rational.

[0042] In the disclosure, preferably, in a case where the standard ignition operation is executed a plurality of times repeatedly, the drive speed of the fan gradually increases.

[0043] According to such a configuration, the following effects are obtained.

[0044] That is, in the case where the standard ignition operation is executed a plurality of times repeatedly, wind blowing from outside continuously occurs in the combustion chamber and its downstream portion, and there may be cases where the air-fuel mixture is not ignited due to this. In contrast, according to the configuration, since the drive speed of the fan is gradually increased, it becomes excellent in the effect of canceling out the aforementioned wind blowing. Thus, it is more preferable for eliminating the difficulty in igniting the air-fuel mixture due to wind blowing.

[0045] In the disclosure, preferably, in a case where the air-fuel mixture is not ignited regardless of the non-standard ignition operation being executed repeatedly for a predetermined second upper-limit number of times, it is determined that an abnormality has occurred, and no ignition operation is continuously executed thereafter.

[0046] According to such a configuration, the safety of the combustion device can be ensured.

[0047] In the disclosure, preferably, in a case where the standard ignition operation and/or the non-standard ignition operation is executed repeatedly, an interval period is secured, and during the interval period, the fan is driven at a higher speed than a drive speed during the standard ignition operation and the non-standard ignition operation, and a scavenging process of the combustion chamber is executed.

[0048] According to such a configuration, during the interval period in the case where the standard ignition operation and/or the non-standard ignition operation is executed a plurality of times repeatedly, a scavenging process of the combustion chamber is executed in a state where the drive speed of the fan is increased higher than during the standard ignition operation or during the non-standard ignition operation. According to the scavenging process, since unburned gas and the like are eliminated from the combustion chamber, it is more preferable for improving ignitability.

[0049] In the disclosure, preferably, a setting part capable of selecting and setting a specific ignition operation mode as the ignition operation for the air-fuel mixture is provided, and in a case where the specific ignition operation mode is set in the setting part, the standard ignition operation is omitted in executing the ignition operation for the air-fuel mixture and the non-standard ignition operation is executed.

[0050] According to such a configuration, the following effects are obtained.

[0051] That is, in the case where it is known in advance that fuel gas with poor ignitability, such as emergency gas mixed with approximately 50% each of LP gas and air, is to be used as the fuel gas, the specific ignition operation mode is set using the setting part. Accordingly, during execution of the ignition operation for the fuel gas, execution of the standard ignition operation is omitted and the non-standard ignition operation with excellent ignitability is immediately executed, making it possible to complete ignition of the fuel gas in a short time.

[0052] A hot water device provided by a second aspect of the disclosure includes a combustion device; and a heat exchanger capable of heating hot water using combustion gas generated by the combustion device, in which the combustion device provided by the first aspect of the disclosure is configured as the combustion device.

[0053] According to such a configuration, the same effects as described for the combustion device provided by the first aspect of the disclosure are obtained.

[0054] Other features and advantages of the disclosure will become more apparent from the following description of embodiments of the disclosure made with reference to the accompanying drawings.

[0055] Hereinafter, preferred embodiments of the disclosure will be specifically described with reference to the drawings.

[0056] A hot water device WH illustrated in FIG. 1 is a hot water supply device, and includes a combustion device C, a heat exchanger 11, a hot water supply piping part B, and a control part 6, each disposed within an exterior case 19.

[0057] The combustion device C includes a premixing device A, a variable-speed fan 1, a combustion chamber 29 provided with a burner part 2, a can body 10 that forms the combustion device C internally, an ignition device (ignition plug) 22 provided in the combustion chamber 29, and a flame detection sensor (flame rod) 23.

[0058] Details of the premixing device A will be described later, but an air-fuel mixture of air and fuel gas is generated using this premixing device A, and the air-fuel mixture is supplied to the combustion chamber 29 via the fan 1. The burner part 2 provided in the combustion chamber 29 includes a porous plate 21 having a plurality of ventilation holes 20 (flame holes). The air-fuel mixture passes through the plurality of ventilation holes 20 and is ignited by the ignition device 22 below the porous plate 21 to combust. Combustion gas from the combustion acts on the heat exchanger 11, and hot water passing through the heat exchanger 11 is heated. The heat exchanger 11 includes primary and secondary heat exchange parts 11A and 11B for sensible heat recovery and latent heat recovery, but the disclosure is not limited thereto, and may be configured to include only the heat exchange part 11A for sensible heat recovery, for example. Reference numerals 11a and 11b respectively indicate an inlet part and an outlet part for hot water of the heat exchanger 11. After passing through the heat exchanger 11, the combustion gas passes through an exhaust duct part 10a of the can body 10 and is exhausted to the outside as exhaust gas from an exhaust port 10b at its terminal end.

[0059] The hot water supply piping part B includes an inlet water path 70 for sending hot water entering to an external water inlet 73 from outside to the heat exchanger 11, a hot water outlet path 71 for guiding hot water discharged from the heat exchanger 11 to a hot water outlet port 74, a bypass path 72, and a flow path switching valve V3. The bypass path 72 serves to adjust the hot water outlet temperature by guiding part of the non-heated hot water flowing through the inlet water path 70 to an intermediate portion Pa of the hot water outlet path 71 and mixing it with the heated hot water. Hot water supply to a desired hot water supply destination is possible from the hot water outlet port 74. The inlet water path 70 is provided with a flow rate sensor Sa for determining whether or not the hot water flow rate of the heat exchanger 11 is equal to or higher than a predetermined minimum operating flow rate (MOQ-ON).

[0060] As well illustrated in FIG. 2 to FIG. 6C, the premixing device A includes a device main part A0, a flapper 5 assembled to the device main part A0, and flow path adjustment members 82A and 82B.

[0061] In the figures, the x and y directions are directions that intersect with each other, and both are directions that intersect with an air flow direction (upward) in a gas flow path 3 to be described later.

[0062] The device main part A0 includes a premixing flow path forming member 4 and a pipe joint part 9.

[0063] The premixing flow path forming member 4 includes a tubular part 49 that forms a venturi-shaped gas flow path 3 inside, a mounting flange part 48 connected in series to an upper end of the tubular part 49, a base part 44, and a fuel gas flow path 8.

[0064] The pipe joint part 9 is a portion to which a gas pipe 99 (refer to FIG. 1) is connected and which receives supply of fuel gas. The pipe joint part 9 includes a tubular part 94 that forms a hollow part inside serving as a starting end part of the fuel gas flow path 8, and a mounting flange part 95 connected in series to a base end part of the tubular part 94.

[0065] The base part 44 is a portion where the pipe joint part 9 is mounted, and has a pedestal shape or similar shape integrally provided on an outer peripheral surface part of the tubular part 49, and includes a flange part 44a corresponding to the flange part 95 of the pipe joint part 9. The mounting of the pipe joint part 9 to the base part 44 is achieved by bringing the flange parts 95 and 44a into opposing contact and fastening them using screw members 90 such as small screws.

[0066] As illustrated in FIG. 1, the premixing device A has the pipe joint part 9 connected to the gas pipe 99, and receives supply of fuel gas from an unillustrated fuel gas supply source via a main valve (opening/closing valve) V2 and a pressure equalizing valve (zero governor) V1. On the other hand, the premixing device A is directly or indirectly connected to an intake side of the fan 1 using the flange part 48. In response to the fan 1 being driven, external air flows into the premixing flow path forming member 4 (the gas flow path 3 inside the tubular part 49). Due to negative pressure action generated by the air flow, fuel gas flows out from first and second fuel gas outlets 80a and 80b to be described later, and an air-fuel mixture of the fuel gas and the air is generated. The air-fuel mixture is supplied to the combustion chamber 29 via the fan 1.

[0067] As well illustrated in FIG. 4B and FIG. 5B, the gas flow path 3 is provided with a partition wall part 40 extending in an up-down height direction along the air flow direction. As a result, a part of the gas flow path 3 is partitioned into first and second flow paths 3a and 3b arranged in the y direction with the partition wall part 40 interposed therebetween.

[0068] As well illustrated in FIG. 4A to FIG. 6C, the first and second flow paths 3a and 3b are provided with first and second blade parts 41a and 41b (hatched pattern portions in FIG. 6A and FIG. 6C). Among the first and second blade parts 41a and 41b, the first and second fuel gas outlets 80a and 80b are provided in upward opening shapes on upper surface parts facing downstream in the air flow direction.

[0069] The first and second blade parts 41a and 41b extend in the y direction so as to cross the first and second flow paths 3a and 3b respectively in the horizontal direction, and their one end parts are connected to a peripheral wall inner surface part of the gas flow path 3 (an inner surface part of a peripheral wall part of the tubular part 49), and their other end parts are connected to each other with the partition wall part 40 interposed therebetween.

[0070] A part of the first flow path 3a is divided into a pair of regions 3a' that sandwich the first blade part 41a in the x direction, as well illustrated in FIG. 6A to FIG. 6C. A part of the second flow path 3b is divided into a pair of regions 3b' that sandwich the second blade part 41b in the x direction.

[0071] The fuel gas flow path 8 is a flow path whose starting end part is inside the tubular part 94 of the pipe joint part 9 and whose terminal end part is the first and second fuel gas outlets 80a and 80b. The intermediate portion of the fuel gas flow path 8 is configured using flow path adjustment members 82A and 82B. The flow path adjustment members 82A and 82B are mounted in a state of being sandwiched between the pipe joint part 9 and the base part 44, and an inner portion of the flow path adjustment member 82A communicates with an upstream portion of the fuel gas flow path 8 through an opening part 82c. The flow path adjustment member 82B has two opening parts 82a and 82b, and starting from the opening parts 82a and 82b, the fuel gas flow path 8 branches into first and second fuel gas flow paths 8a and 8b. By determining the size of the opening areas of the opening parts 82a and 82b, the respective flow path resistances of the first and second fuel gas flow paths 8a and 8b may be individually controlled. The first and second fuel gas flow paths 8a and 8b are formed inside the base part 44 and inside the first and second blade parts 41a and 41b.

[0072] The fuel gas supplied to the pipe joint part 9 is guided to the first and second fuel gas outlets 80a and 80b via the first and second opening parts 82a and 82b of the flow path adjustment member 82B and the first and second fuel gas flow paths 8a and 8b.

[0073] In the lower part and upper part inside the tubular part 49, an air inlet part 3c and an air outlet part 3d are formed that communicate with the first and second flow paths 3a and 3b. In response to the fan 1 being driven, external air may flow into the air inlet part 3c and then branch and flow into the first and second flow paths 3a and 3b. Due to negative pressure action generated by air flow in the first and second flow paths 3a and 3b, fuel gas flows out from the first and second fuel gas outlets 80a and 80b, and an air-fuel mixture of air and fuel gas is generated. The air-fuel mixture flows out from the air outlet part 3d to the outside of the tubular part 49 (to the intake port side of the fan 1).

[0074] The flapper 5, as illustrated in FIG. 4 to FIG. 6, is capable of opening and closing the first flow path 3a (pair of regions 3a') and also capable of opening and closing the first fuel gas outlet 80a simultaneously. The first flow path 3a corresponds to a part of the gas flow path in the disclosure. The flapper 5 is, for example, a resin molded product, with its base end part supported by a support part 52 using a shaft body 61, and is capable of swinging in the up-down height direction around its center line CL. The shaft body 61, as well illustrated in FIG. 3, is a portion supported by a pair of auxiliary members 60 having support holes 60a. The pair of auxiliary members 60 are mounted to a step part 43 separately provided in the first flow path 3a using screw members 92 and the like.

[0075] The flapper 5 swings with its own weight as a downward force and the air flow progressing upward through the first flow path 3a as an upward force, and in the case of the gas flow path 3 having a small air flow rate, the opening degree becomes smaller than in the case of having a large air flow rate. In the case of the air flow rate being small, the flapper 5 becomes in a horizontally laid closed state due to its own weight, and in response to the air flow rate increasing, it becomes in an open state lifted by the upward air flow. The open state of the flapper 5 includes not only the fully open state but also a partially open state. A pair of fins 55 are appropriately protruded on the flapper 5, positioned to sandwich the first blade part 41a in the case of the flapper 5 being in the closed state.

[0076] The control part 6 is configured using a microcomputer and the like, executes operation control and data processing of each part of the hot water device WH, and also executes drive speed control (rotation control) of the fan 1 during execution of hot water supply operation. However, the specific details will be described later with reference to FIG. 7 to FIG. 10 and the like.

[0077] A remote control 5A installed in a kitchen or bathroom is communicatively connected to the control part 6. This remote control 5A includes a display part 50 capable of displaying various data, a plurality of operation switches 51, and an acoustic generation device (not illustrated) and the like. By configuring the remote control 5A, it is possible to execute settings such as target hot water supply temperature and a specific ignition operation mode to be described later, error notification using voice or image display, and the like.

[0078] FIG. 7 illustrates an example of the relationship between the drive speed of the fan 1 of the combustion device C of this embodiment and the CO.sub.2 concentration in combustion gas.

[0079] As illustrated in the figure, the drive speed range of the fan 1 on the horizontal axis is divided into a second drive speed range SR2 in which the flapper 5 of the premixing device A is in a closed state (fully closed state), and a first drive speed range SR1 which is a higher speed range than the second drive speed range SR2 and in which the flapper 5 is in an open state. The low-speed side speed range of the first drive speed range SR1 is a specific speed range SR1a in which the flapper 5 is in a partially open state, and a higher speed range SR1b than that is a speed range in which the flapper 5 is in a fully open state.

[0080] On the other hand, the CO.sub.2 concentration in combustion gas on the vertical axis corresponds to the ease of combustion of the air-fuel mixture, and it may be determined that the higher the concentration, the better the ignitability.

[0081] As illustrated by line L in FIG. 7, in the process of gradually increasing the drive speed of the fan 1 from a low speed range, in the second drive speed range SR2, the higher the drive speed, the higher the CO.sub.2 concentration becomes. This is because in the case of the drive speed of the fan 1 being too low, the negative pressure generated in the gas flow path 3 is weak and fuel gas outflow to the gas flow path 3 is not promoted, whereas in the case of the drive speed becoming high, such a situation is resolved and fuel gas outflow is promoted. The CO.sub.2 concentration reaches a peak at the location indicated by reference numeral Na in FIG. 7, that is, at the speed at a boundary between the second drive speed range SR2 and the first drive speed range SR1 (the speed immediately before the flapper 5 changes from the closed state to the open state).

[0082] In the case of the drive speed of the fan 1 transitioning from the second drive speed range SR2 to the specific speed range SR1a of the first drive speed range SR1, the CO.sub.2 concentration gradually decreases as the drive speed of the fan 1 becomes higher, and in an intermediate range of the specific speed range SR1a and the higher speed range than that, the CO.sub.2 concentration becomes steady.

[0083] Next, an example of operation control in the hot water device WH including the combustion device C and its operation will be described with reference to the flowchart of FIG. 8.

[0084] In the case where a terminal (not illustrated) of the hot water supply destination of the hot water device WH is opened and the hot water flow rate of the heat exchanger 11 detected by the flow rate sensor Sa becomes equal to or higher than a predetermined minimum operating flow rate, and the need to drive combustion of the burner part 2 arises, the control part 6 starts driving of the fan 1 (S1: YES, S2). Moreover, the control part 6 sets the drive speed of the fan 1 to a predetermined speed SPa which is the first drive speed range SR1, and sets the main valve V2 for fuel gas supply to the opened state so as to supply fuel gas to the premixing device A (S3). As a result, in the premixing device A, an air-fuel mixture of fuel gas and air is generated. The speed SPa of the fan 1 is, for example, as illustrated in FIG. 7, set to a speed in the highest speed range within the specific speed range SR1a of the first drive speed range SR1, or a speed higher than that. Under such conditions, an ignition operation (standard ignition operation) in which the ignition device 22 is turned on is executed (S4).

[0085] In the case of the aforementioned standard ignition operation causing ignition of the air-fuel mixture and the flame of combustion being detected by the control part 6 via the flame detection sensor 23, drive combustion control of the burner part 2 (such as control of combustion power) is executed thereafter (S5: YES, S6).

[0086] In the aforementioned standard ignition operation, the drive speed of the fan 1 is the speed SPa, and in the premixing device A, the flapper 5 is in an open state as illustrated in FIG. 5. Thus, air flows through both the first and second flow paths 3a, 3b, and fuel gas flowing out from both the first and second fuel gas outlets 80a, 80b is mixed with this air. For this reason, a large amount of air-fuel mixture with an air-fuel ratio suitable for normal drive combustion of the burner part 2 may be generated and supplied to the burner part 2. Thus, in the case of causing ignition of the air-fuel mixture by the aforementioned standard ignition operation, drive combustion in a state with large combustion power can be immediately realized, which is preferable for shortening the time until heating hot water to a target hot water supply temperature. Such an operation enables, for example, in the case of attempting to immediately restart a second hot water supply operation after completing one hot water supply operation, the second hot water supply temperature to be quickly restored to the original hot water supply temperature, which is useful for suppressing so-called undershoot of hot water temperature. Moreover, scavenging during an interval period described later is also useful for suppressing undershoot.

[0087] The drive combustion control of the burner part 2 ends at the stage where the hot water flow rate of the heat exchanger 11 becomes less than a predetermined minimum operating flow rate due to the terminal at the hot water supply destination being closed, and it becomes necessary to stop the drive combustion of the burner part 2 (S7: YES). In this case, after the main valve V2 of the fuel gas is closed, scavenging (post-purge) is executed (S8, S9). Here, scavenging is a process of removing unburned gas and exhaust gas from the combustion chamber 29 to the outside via the exhaust duct part 10a by performing air blowing from the fan 1 to the combustion chamber 29.

[0088] Different from the above, in the case where it is determined that there is no ignition of the air-fuel mixture in step S5, the main valve V2 for fuel gas is set to a closed state, and a predetermined interval period is secured (S5: NO, S10). Moreover, during this interval period, scavenging is executed (S11). This scavenging is efficiently performed in a state where the fan 1 is increased to a speed higher than the speed SPa during standard ignition operation, and removal of unburned gas and the like from the combustion chamber 29 is appropriately performed.

[0089] In response to the aforementioned interval period timing out, the control part 6 determines whether or not the execution number of times of the aforementioned standard ignition operation has reached a predetermined first upper-limit number of times (for example, 6 times) (S12: YES, S13). In the case of not reaching the first upper-limit number of times (S13: NO), the process returns to the previous steps S3, S4 to execute the standard ignition operation again, and in the case of ignition of the air-fuel mixture occurring (S5: YES), the series of steps S6 to S9 described above are executed.

[0090] Different from this, in the case of no ignition of the air-fuel mixture (S5: NO), the previous steps S10 to S13 are executed again. In this way, the operation control such as the standard ignition operation and the scavenging during the interval period thereafter ends in the case of ignition of the air-fuel mixture occurring, but otherwise is repeatedly executed up to the first upper-limit number of times.

[0091] On the other hand, in the case of the execution number of times of the standard ignition operation reaching the first upper-limit number of times without ignition of the air-fuel mixture, a non-standard ignition operation is executed thereafter (S13: YES, S14, S15). The non-standard ignition operation corresponds to an exceptional ignition operation relative to the standard ignition operation that is executed in principle, and in the non-standard ignition operation, the drive speed of the fan 1 is set to a predetermined speed SPb in the second drive speed range SR2, and after the main valve V2 of the fuel gas is set to an open state, the ignition device is turned on. Here, the speed SPb of the fan 1 is the speed in the highest speed range of the second drive speed range SR2, and more preferably, is the speed at the boundary between the second drive speed range SR2 and the first drive speed range SR1 indicated by reference numeral Na in FIG. 7 (the speed immediately before the flapper 5 changes from the closed state to the open state).

[0092] According to the aforementioned non-standard ignition operation, in the premixing device A, the flapper 5 is in the closed state as illustrated in FIG. 4A to FIG. 4C, and among the first and second flow paths 3a, 3b, air flows only through the second flow path 3b, and the air is mixed with the fuel gas flowing out from the second fuel gas outlet 80b, such that a fuel-rich air-fuel mixture with good combustibility (ignitability) is generated and supplied to the burner part 2. The drive speed of the fan 1 is set to speed SPb, and as illustrated in FIG. 7, is set so as to obtain an air-fuel mixture with the highest CO.sub.2 concentration, which is even more preferable in terms of improving combustibility (ignitability) of the air-fuel mixture. Thus, even in the case of no ignition of the air-fuel mixture by the previous standard ignition operation, it is possible to considerably increase the possibility of ignition of the air-fuel mixture by executing the non-standard ignition operation.

[0093] In the case of ignition of the air-fuel mixture by execution of the non-standard ignition operation (S16: YES), the process thereafter moves to the series of steps S6 to S9 described above.

[0094] Different from the above, in step S16, in the case where it is determined that there is no ignition of the air-fuel mixture, whether or not the execution number of times of the non-standard ignition operation has reached a predetermined second upper-limit number of times (for example, three times) is determined in the control part 6 (S16: NO, S17). In the case of the execution number of times of the non-standard ignition operation not reaching the second upper-limit number of times, a non-standard ignition operation is executed again thereafter, but as a prerequisite, the main valve V2 for fuel gas is set to a closed state and a predetermined interval period is secured (S17: NO, S20). Moreover, during the interval period, scavenging is executed with the fan 1 increased to a speed higher than the aforementioned speeds SPa and SPb (S21). In response to the aforementioned interval period timing out, the non-standard ignition operation is re-executed (S22: YES, S14 to S15). In the case of ignition of the air-fuel mixture by the re-execution of the non-standard ignition operation (S16: YES), the process thereafter moves to the series of steps S6 to S9 described above.

[0095] On the other hand, in the case of no ignition of the air-fuel mixture even by re-execution of the non-standard ignition operation, the previous steps S20 to S15 are further executed. Here, in the case of the execution number of times of the non-standard ignition operation reaching the second upper-limit number of times without ignition of the air-fuel mixture being achieved, the control part 6 determines that an abnormality has occurred in the combustion device C or the hot water device WH, and generates an alarm by sound generation and screen display using the remote control or the like (S17: YES, S18). Moreover, at that time, the main valve V2 for fuel gas is set to a closed state, and this closed state is continued, and execution of a new ignition operation thereafter is set to a prohibited state (S18). The fan 1 continues to be driven in an increased speed state, and scavenging is executed for a predetermined time (S19).

[0096] FIG. 9 illustrates an example of a control mode relating to abnormality determination of the ignition device 22, fan 1, and control part 6 in the case of no ignition of the air-fuel mixture being achieved at all among the aforementioned operation procedures executed in the combustion device C.

[0097] In the same figure, the ignition operations indicated by reference numerals N1 to N6 are standard ignition operations executed with the fan 1 set to speed SPa. In contrast, the ignition operations indicated by reference numerals N7 to N9 are non-standard ignition operations executed with the fan 1 set to speed SPb (in the same figure, speed lower than speed SPa by SP). In the case of no ignition of the air-fuel mixture at the end point (time ta) of the non-standard ignition operation of reference numeral N9, the control part 6 determines that there is an abnormality at that point.

[0098] In the control mode illustrated in FIG. 9, predetermined operation control including three ignition operations N1 to N3, N4 to N6, and N7 to N9 respectively is grouped as groups G (G1 to G3), and basic operation control of the ignition device 22 and the fan 1 is standardized and repeated. According to such a configuration, it is preferable for achieving simplification of control software and accurate operation control of each part.

[0099] The combustion device C and hot water device WH of this embodiment may also be configured to execute control as illustrated in FIG. 10 instead of FIG. 9.

[0100] That is, in FIG. 10, in the case of standard ignition operations N1 to N6 being executed sequentially, the drive speed of the fan 1 during these operations is gradually increased by appropriate speed increments 1 to 5 respectively (in the previous FIG. 9, the drive speed of the fan 1 during execution of standard ignition operations N1 to N6 is constant at speed SPa).

[0101] According to the control illustrated in FIG. 10, the following effects are obtained.

[0102] That is, in the case of wind blowing from outside into the exhaust port 10b of the exhaust duct part 10a during execution of standard ignition operation, and this continuing to occur, there may be cases where ignition of the air-fuel mixture is not achieved no matter how many times the standard ignition operation is repeated. In contrast, according to the control illustrated in FIG. 10, since the drive speed of the fan 1 is gradually increased each time the standard ignition operation is repeated, an effect of canceling out the aforementioned wind blowing is obtained, and it becomes possible to improve the ignitability of the air-fuel mixture.

[0103] The combustion device C and hot water device WH of this embodiment may also be configured to execute operation control as illustrated in FIG. 11 instead of the series of operation control illustrated in FIG. 8, which will be described below.

[0104] In FIG. 11, steps S1 and S2 are the same as in FIG. 8. In the next step S2a, the control part 6 determines whether or not a specific ignition operation mode is selected and set as the operation mode of the combustion device C. Here, the specific ignition operation mode is a mode that is set in cases where it is known in advance that emergency gas, which is a mixture of approximately 50% each of LP gas and air, for example, is to be used as the fuel gas, and is a mode for omitting standard ignition operation and immediately executing non-standard ignition operation. This mode may be set by a user operating the operation switch 51 of the remote control 5A, for example. The operation switch 51 corresponds to an example of the setting part in the disclosure, but the mode may also be set by means other than the operation switch 51.

[0105] In the case of the aforementioned specific ignition operation mode not being set (S2a: NO), the process thereafter moves to step S3, and the normal series of operation control described with reference to FIG. 8 is executed. In contrast, in the case of the specific ignition operation mode being set (S2a: YES), the process thereafter immediately moves to step S14 of FIG. 8, standard ignition operation is not executed, and non-standard ignition operation is immediately executed.

[0106] According to the aforementioned operation control, in the case where it is known in advance that emergency gas that is difficult to ignite is to be used as the fuel gas, standard ignition operation is prevented from being wastefully executed for this emergency gas, and non-standard ignition operation is immediately executed. Thus, the time required for ignition of the emergency gas can be shortened, and combustion driving of the burner part 2 may be started early.

[0107] FIG. 12 illustrates another embodiment of the disclosure. Note that elements that are the same as or similar to the aforementioned embodiment are given the same reference numerals as the aforementioned embodiment, and duplicate descriptions are omitted.

[0108] A hot water device WHa in FIG. 12 may be configured as a heat source device for hot water heating in addition to general hot water supply function.

[0109] The hot water supply piping part Ba of the hot water device WHa is connected by piping to hot water heating equipment (not illustrated), and has a return port 76a and an outgoing port 76b for sending and receiving hot water for heating (antifreeze is also applicable) to and from the hot water heating equipment. In addition, a pump P, an additional heat exchanger HE, and a flow path switching valve V4 are connected by piping to the heat exchanger 11, and a hot water circulation path 75 is configured that enables circulation of hot water sent to the heat exchanger 11 by the pump P and heated through the additional heat exchanger HE. In the hot water device WHa, hot water for heating that enters the return port 76a by driving of the pump P may be sent to the heat exchanger 11 for heating, then guided to the outgoing port 76b via the flow path switching valve V4, and returned to the hot water heating equipment. The general hot water supply function is realized by a configuration in which hot water that enters the water inlet 73 is sent to the additional heat exchanger HE for heating before reaching the hot water outlet port 74.

[0110] As understood from this embodiment, the hot water device according to the disclosure is not limited to general hot water supply use, but may also be configured for hot water heating use. Of course, it may also be for bath hot water supply use (for bath reheating use).

[0111] The disclosure is not limited to the content of the above-described embodiments. The specific configurations of each part of the combustion device according to the disclosure and the hot water device including the same may be variously changed in design within the intended scope of the disclosure.

[0112] The fan only needs to be variable in speed, and its specific type does not matter.

[0113] The premixing device includes a gas flow path through which air flows internally by driving of the fan, a fuel gas outlet that discharges fuel gas by negative pressure in the case of air flowing through the gas flow path, and a flapper that opens and closes a part of the gas flow path, but the specific shapes, sizes, materials, etc. of these respective parts are also not limited.

[0114] The specific values of the first and second upper-limit number of times are also not limited, and for example, each may be set to one time.

[0115] As types of fuel gas, natural gas and LP gas are given as representative examples, but the disclosure is not limited thereto, and various types of fuel gas may be applied, such as the above-described emergency gas (for example, a mixture of approximately 50% each of LP gas and air).

[0116] The combustion device according to the disclosure is not limited to hot water supply device use, and may also be a combustion device for other uses such as heating or incineration. Moreover, the combustion device is not limited to a type that advances combustion gas downward, but may also be a type that advances combustion gas upward, for example.