Combustion apparatus

A combustion apparatus (1) has a burner (11) configured to burn combustion gas, a heat exchanger (12) disposed below the burner (11), and a combustion fan (13) configured to supply air for combustion, wherein the combustion apparatus performs post-purge operation in which the combustion fan (13) is activated for a predetermined period of time after combustion operation of the burner (11) stops, and intermittent blower operation in which activation and deactivation of the combustion fan (13) is repeated a plurality of times at predetermined intervals after the post-purge operation ends.

FIELD OF THE INVENTION

The present invention relates to a combustion apparatus. Especially, the present invention relates to the combustion apparatus configured such that a burner is disposed above a heat exchanger and combustion exhaust gas generated by the burner is supplied to the heat exchanger from above.

BACKGROUND ART

In a conventional combustion apparatus such as a water heater and a heat source device for a room heater, post-purge operation is performed in which a combustion fan is continuously activated to discharge combustion exhaust gas inside a housing to the outside for a predetermined period of time even after combustion operation of a burner stops.

In this kind of the combustion apparatus, during the combustion operation, strong acid drain is generated by condensing moisture in the combustion exhaust gas on a surface of the heat exchanger. Thus, the drain may evaporate into vapor again depending on a temperature around the heat exchanger or an amount of the drain.

In a so-called upward combustion type combustion apparatus configured such that the burner is disposed below the heat exchanger and the combustion exhaust gas generated by the burner is supplied to the heat exchanger from a bottom to a top, after the post-purge operation ends, the vapor generated around the heat exchanger ascends inside the housing, and continues to flow to an exhaust port on an upper side. Therefore, the vapor imparts no negative affect on other components. However, in a so-called downward combustion type combustion apparatus configured such that the burner is disposed above the heat exchanger and the combustion exhaust gas generated by the burner is supplied to the heat exchanger from above, after the post-purge operation ends, the vapor flows back upward inside the housing. As a result, components such as the combustion fan and a pre-mixing device provided upstream of the burner may be corroded.

In light of the above-described problem, it can also be considered to prolong the post-purge operation until evaporation of the drain ends. However, if the post-purge operation is continued for a long time, water inside the heat exchanger is excessively cooled. As a result, there is a possibility that a time lag from resume of the combustion operation to supply of hot water at a desired temperature to a hot water supplying terminal becomes longer, or that under a cold environment, the water freezes inside the heat exchanger, which leads to a defect of hot water supply. Further, there is a problem that power consumption and noise increase, insomuch as the combustion fan continues to activate for a long time.

PRIOR ARTS

SUMMARY OF THE INVENTION

The present invention has been made to solve the problems described above, and an object of the present invention is to enhance hot water resupply performance and to reduce power consumption and noise during operation in a combustion apparatus such as a water heater and a heat source device for a room heater.

According to one aspect of the present invention, there is provided a combustion apparatus comprising:

a housing accommodating a burner configured to burn combustion gas and a heat exchanger configured to recover heat in combustion exhaust gas generated by the burner to heat water supplied from a water supply source;

a combustion fan configured to supply air for combustion of the burner into the housing,

the heat exchanger being disposed below the burner inside the housing, and

the combustion exhaust gas from the burner being supplied to the heat exchanger from above;

a post-purge operation-executing section configured to activate the combustion fan for a predetermined period of time after combustion operation of the burner stops; and

an intermittent blower operation-executing section configured to repeat activation and deactivation of the combustion fan a plurality of times at predetermined intervals after the post-purge operation ends.

According to the present invention, since water inside the heat exchanger is not excessively cooled during a period until combustion operation is resumed next, it not only can make shorter a time lag till hot water at a predetermined temperature is supplied to the hot water supplying terminal, but can prevent freezing of the water inside the heat exchanger. Thus, hot water resupply performance is enhanced. Moreover, since the activation time of the combustion fan is shortened, power consumption and noise during operation are reduced.

Other objects, features and advantages of the present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings.

DESCRIPTION OF EMBODIMENTS

Hereinafter, referring to drawings, a combustion apparatus according to an embodiment of the present invention will be described in detail.

As shown inFIG. 1, the combustion apparatus according to the embodiment of the present invention is a water heater1that heats water supplied into a heat exchanger12from a water supply pipe L1with combustion exhaust gas generated by a burner11, and supplies it to a hot-water supplying terminal P such as a faucet or a shower through a hot-water supply pipe L2.

Inside an exterior case10of the water heater1, a substantially rectangular box shaped housing20accommodating the burner11and the heat exchanger12is provided. The exterior case10is provided with an air inlet port101to take air outside the apparatus into the exterior case10and an exhaust port102to discharge the air and the combustion exhaust gas inside the housing20to an outside of the apparatus.

The housing20is configured by a lower-side opening box shaped combustion chamber21forming an upper portion of the housing20, and an upper-side opening box shaped heat exchange chamber22forming a lower portion of the housing20. To an air leading-out port221provided in a lower area of the heat exchange chamber22is connected the exhaust port102through an exhaust passage23.

In the combustion chamber21, the burner11configured to burn combustion gas supplied from a gas pipe L3to generate the combustion exhaust gas is incorporated. On the other hand, in the heat exchange chamber22, the heat exchanger12configured to recover heat in the combustion exhaust gas generated by the burner11to heat the water supplied from the water supply pipe L1is incorporated.

An air introduction port211provided in an upper portion of the combustion chamber21is continuously connected to a combustion fan13for taking, as the air for combustion of the burner11, the air outside the apparatus into the exterior case10from the air inlet port101and sending it into the combustion chamber21. Moreover, a suction port131of the combustion fan13is continuously connected to a pre-mixing device14for mixing the air taken into the exterior case10from the air inlet port101and the combustion gas supplied from the gas pipe L3. Furthermore, the air introduction port211of the combustion chamber21is provided with a check valve15configured to prevent the air and the combustion exhaust gas inside the housing20from flowing back to a combustion fan13side, that is, on an upstream side.

Inside the exterior case10of the above-described water heater1, a supply-exhaust path from the air inlet port101to the exhaust port102through the housing20is defined. The premixing device14, the combustion fan13, the check valve15, the burner11, and the heat exchanger12are arranged in this order from an upstream side of the supply-exhaust path. Accordingly, when the combustion fan13is activated, the air outside the apparatus is taken into an internal space of the exterior case10from the air inlet port101. The taken air is then introduced into the combustion chamber21through the pre-mixing device14, and further, sequentially passes through setting parts of the burner11and the heat exchanger12to be discharged outside from the exhaust port102.

The burner11has a plurality of flame ports (not shown) in a lower surface, and ejects a mixture gas of the combustion gas and the air mixed in the pre-mixing device14downward from the flame ports to burn the same. That is, the burner11is configured such a manner that the lower surface becomes a combustion surface.

The heat exchanger12is configured by the plurality of plate shaped heat transfer fins120provided vertically, and arranged side horizontally by side in an upper space of the heat exchange chamber22, first heat transfer tubes121inserted into the respective heat transfer fins120, and arranged in a plurality of rows vertically and in parallel substantially horizontally in the upper space of the heat exchange chamber22, and second heat transfer tubes122arranged in a plurality of rows vertically and in parallel substantially horizontally in a lower space of the heat exchange chamber22. In this heat exchanger12, after sensible heat in the combustion gas introduced from the combustion chamber21into the heat exchange chamber22is recovered by the first heat transfer tubes121, sensible heat and latent heat in the combustion gas are further recovered by the second heat transfer tubes122.

Tube ends of the first heat transfer tubes121are connected to each other by coupling headers not shown to configure one sensible heat exchanging pipe line12A meandering in the upper space of the heat exchange chamber22. Tube ends of the second heat transfer tubes122are similarly connected to each other by coupling headers not shown to configure one latent heat exchanging pipe line12B meandering in the lower space of the heat exchange chamber22.

An inlet-side tube end of the latent heat exchanging pipe line12B connects to the water supply pipe L1through a water inlet pipe line26, and an outlet-side tube end of the latent heat exchanging pipe line12B connects to an inlet-side tube end of the sensible heat exchanging pipe line12A. Moreover, an outlet-side tube end of the sensible heat exchanging pipe line12A connects to the hot-water supply pipe L2through a hot water outlet pipe line27. Accordingly, the water supplied from the water supply pipe L1into the water inlet pipe line26sequentially flows through the latent heat exchanging pipe line12B and the sensible heat exchanging pipe line12A, and then, is led out from the hot water outlet pipe line27to the hot-water supply pipe L2.

The water inlet pipe line26is provided with a flow sensor16for detecting a water supply amount to the heat exchanger12. On the other hand, the hot water outlet pipe line27is provided with a heat exchanger temperature sensor17for detecting a hot water temperature from the sensible heat exchanging pipe line12A.

When the heat exchanger12recovers the sensible heat and the latent heat in the combustion exhaust gas, strong acid drain, which is generated by condensing moisture in the combustion exhaust gas on surfaces of the heat transfer fins120, the first heat transfer tubes121, and the second heat transfer tubes122, drops on a bottom portion of the heat exchange chamber22. The dropping drain is collected and neutralized in a drain neutralizer18coupled to the bottom portion of the heat exchange chamber22.

In the exterior case10, a control circuit3configured to control operation of the whole water heater1is incorporated. The control circuit3is connected to an ignition electrode (not shown) of the burner11, a fan motor130of the combustion fan13, a mixing valve (not shown) of the pre-mixing device14, the flow sensor16, and the heat exchanger temperature sensor17via electric lines.

Although not shown, the control circuit3has circuit configurations of a combustion control section configured to perform ignition, extinction, and adjustment of a combustion amount of the burner11, a supply-exhaust control section configured to perform activation, deactivation, and adjustment of a rotational speed of the combustion fan13, a water supply-determining section configured to determine whether or not the water supply to the hot water supplying terminal P is performed on the basis of a water amount detected by the flow sensor16, a heat exchanger temperature-determining section configured to determine a temperature of the heat exchanger12(hereinafter, refer to as a “heat exchanger temperature”) T1on the basis of a temperature detected by the heat exchanger temperature sensor17, a clock section configured to measure an activation time and a deactivation time of the combustion fan13, and a memory configured to store a set activation time, a set deactivation time, and a number of activation of the combustion fan13during intermittent blower operation, and so on.

Furthermore, the control circuit3of the water heater1according to the first embodiment has circuit configurations of a combustion operation-executing section configured to execute the combustion operation in which when the water supply to the hot water supplying terminal P is started, the combustion fan13is activated to supply the mixture gas to the burner11and the burner11is ignited, and when the water supply to the hot water supplying terminal P is stopped, the supply of the combustion gas to the burner11is cut off and the burner11is extinguished, a post-purge operation-executing section configured to further activate the combustion fan13for a predetermined period of time after the combustion operation of the burner11is stopped, an intermittent blower operation-executing section configured to repeat the activation and the deactivation of the combustion fan13a plurality of times at predetermined intervals after the post-purge operation ends, a blowing stop operation-executing section configured to stop the intermittent blower operation at a time point when the heat exchanger temperature T1becomes lower than a reference temperature Ts during the intermittent blower operation, a first blowing interval-setting section configured to set the deactivation time of the combustion fan13during the intermittent blower operation in accordance with the number of activation of the combustion fan13, and a first blowing amount-setting section configured to set the activation time and the rotational speed of the combustion fan13during the intermittent blower operation in accordance with the number of activation of the combustion fan13, and so on.

FIG. 2is a flowchart showing control operation after the combustion operation of the water heater1according to the first embodiment of the present invention stops. In the water heater1, although not shown, when the water amount detected by the flow sensor16becomes a predetermined value or higher, the control circuit3determines whether the water supply to the hot water supplying terminal P is started, activates the combustion fan13to supply the mixture gas to the burner11, and ignites the burner11. Moreover, when the water amount detected by the flow sensor16becomes lower than the predetermined value, the control circuit3determines whether the water supply to the hot water supplying terminal P is stopped, cuts off the supply of the mixture gas to the burner11, and extinguishes the burner11.

When the water supply to the hot water supplying terminal P is stopped during the combustion operation and the burner11is extinguished, the post-purge operation is performed in which the combustion fan13is further continuously activated at a predetermined purge rotational speed Mp (here, 200 Hz) for a predetermined period of time Ap (here, 180 seconds) from that point of time. This allows the air outside the apparatus to be taken into the housing20, and allows the combustion exhaust gas remaining inside the housing20to be discharged to the outside of the apparatus (ST101).

If the post-purge operation makes the heat exchanger temperature T1lower than the reference temperature Ts (here, 30 degrees Celsius), it is hard for the drain adhering to a surface of the heat exchanger12to become vapor. Therefore, the intermittent blower operation is not performed, and a number of activation C1of the combustion fan13stored in the memory is reset to “0”. Moreover, the water heater1returns to a standby state for waiting for resume of the water supply to the hot water supplying terminal P (ST102to ST103).

On the other hand, if the heat exchanger temperature T1is the reference temperature Ts or higher at a time point when the post-purge operation ends (Yes in the step of ST102), the drain adhering to the surface of the heat exchanger12easily becomes the vapor. Therefore, if a functional defect such as jamming of foreign objects, a failure, and the like occurs in the check valve15, there is a possibility that the vapor flows back from the heat exchange chamber22to the upstream side of the combustion chamber21. Accordingly, the intermittent blower operation is performed in which the activation and the deactivation of the combustion fan13are repeated a plurality of times at the predetermined intervals. Specifically, if in the intermittent blower operation, the number of activation C1of the combustion fan13is “0”, the control circuit3activates the combustion fan13for a first set activation time A1(here, 180 seconds) and at a first set rotational speed M1(here, 250 Hz), and subsequently, deactivates the combustion fan13for a first set deactivation time B1(here, 500 seconds). Moreover, the control circuit3adds “1” to the stored number of activation C1of the combustion fan13, and causes the memory to store the new C1(ST104to ST107).

Again, the determination as to whether or not the heat exchanger temperature T1is the reference temperature Ts or higher is performed. As a result, if the heat exchanger temperature T1is the reference temperature Ts or higher (Yes in the step of ST102), and the number of activation C1is “1” (No in the step of ST104), the control circuit3activates the combustion fan13for a second set activation time A2(here, 140 seconds) shorter than the first set activation time A1and at a second set rotational speed M2(here, 230 Hz) lower than the first set rotational speed M1, and subsequently, deactivates the combustion fan13for a second set deactivation time B2(here, 700 seconds) longer than the first set deactivation time B1. Moreover, the control circuit3adds “1” to the stored number of activation C1of the combustion fan13, and causes the memory to store the new C1. That is, the control circuit3sets the activation time of the combustion fan13to be shorter, the rotational speed to be lower, and the deactivation time to be longer by one level than the step of reference on/off operation in ST105to ST106to cause the combustion fan13to perform on/off operation (ST108to ST110, ST107).

Subsequently, again, the determination as to whether or not the heat exchanger temperature T1is the reference temperature Ts or higher is performed. As a result, if the heat exchanger temperature T1is the reference temperature

Ts or higher (Yes in the step of ST102), and the number of activation C1is neither “0” nor “1” (No in both steps of ST104and ST108), the control circuit3activates the combustion fan13for a third set activation time A3(here, 100 seconds) shorter than the second set activation time A2and at a third set rotational speed M3(here, 200 Hz) lower than the second set rotational speed M2, and subsequently, deactivates the combustion fan13for a third set deactivation time B3(here, 900 seconds) longer than the second set deactivation time B2. It is then determined whether or not the heat exchanger temperature T1is the reference temperature Ts or higher. That is, the control circuit3sets the activation time of the combustion fan13to be shorter, the rotational speed to be lower, and the deactivation time to be longer by one level than the step of on/off operation in ST109to ST110to cause the combustion fan13to perform on/off operation (ST111to ST112).

If the heat exchanger temperature T1is lower than the reference temperature Ts (No in the step of ST102) during the intermittent blower operation is performed as described above, it is determined whether evaporation of the drain ends, the number of activation C1of the combustion fan13stored in the memory is reset to “0”, and the intermittent blower operation ends (ST103).

InFIG. 3, a dashed line41indicates temperature change of the heat exchanger temperature T1in the intermittent blower operation, a thick solid line42indicates humidity change inside the housing20in the intermittent blower operation, and a thin solid line in a lower portion indicates the on/off operation of the combustion fan13. Therefore,FIG. 3shows a relationship between the on/off operation of the combustion fan13and the heat exchanger temperature T1and a relationship between the on/off operation of the combustion fan13and the humidity inside the housing20. Although units of the dashed line41and the thick solid line42are different because they indicate the temperature and the humidity, respectively, numerical value ranges are common, and thus, a single vertical axis is used. As shown inFIG. 3, the temperature (the heat exchanger temperature) T1of the heat exchanger12gradually decreases during the intermittent blower operation. On the other hand, the humidity inside the housing20gradually decreases while repeating rising and falling in accordance with the activation and the deactivation of the combustion fan13. Moreover, when the heat exchanger temperature T1decreases up to a temperature close to the reference temperature Ts (30 degrees Celsius), the humidity hardly rises even in a case where the combustion fan13is deactivated.

In this manner, according to the water heater1of the first embodiment, since the vapor generated around the heat exchanger12after the end of the post-purge operation is discharged to the outside through the intermittent blower operation, the water inside the heat exchanger12is not excessively cooled. This not only can make shorter a time lag till hot water at a predetermined temperature is supplied to the hot water supplying terminal P, but can prevent freezing of the water inside the heat exchanger12. Thus, hot water resupply performance is enhanced. Moreover, since the activation time of the combustion fan13required for backflow prevention of the vapor is shortened, power consumption and noise during the intermittent blower operation are reduced.

In addition, according to the water heater1, when the heat exchanger temperature T1becomes lower than the reference temperature Ts during execution of the intermittent blower operation, the intermittent blower operation is stopped to stop the blowing into the housing20thereafter. Accordingly, it is harder to cool the water inside the heat exchanger12. This not only can make further shorter the time lag, but can prevent freezing of the water inside the heat exchanger12securely. Thus, the hot water resupply performance is further enhanced. Moreover, since the activation time of the combustion fan13required for the backflow prevention of the vapor is further shortened, the power consumption and the noise during the intermittent blower operation are significantly reduced.

Moreover, after the end of the post-purge operation, an amount and an ascending speed of the vapor generated around the heat exchanger12are decreased, as the temperature of the heat exchanger12becomes lower. On the other hand, in the water heater1, during the intermittent blower operation, the deactivation time of the combustion fan13is set to gradually become longer than that at an initial deactivation in accordance with the number of activation of the combustion fan13. That is, since every time the activation and the deactivation of the combustion fan13are repeated, the deactivation time becomes longer, it is harder to cool the water inside the heat exchanger12. This not only can make further shorter the time lag, but can prevent freezing of the water inside the heat exchanger12securely. Thus, the hot water resupply performance is further enhanced. Moreover, since the activation time of the combustion fan13required for the backflow prevention of the vapor is further shortened, the power consumption and the noise during the intermittent blower operation are significantly reduced.

Furthermore, in the water heater1, during the intermittent blower operation, the activation time of the combustion fan13is set to gradually become shorter than that at initial activation, and the rotational speed of the combustion fan13is set to gradually become lower than that at the initial activation, in accordance with the number of activation of the combustion fan13. That is, since every time the activation and the deactivation of the combustion fan13are repeated, the activation time becomes shorter, and the rotational speed becomes lower, it is harder to cool the water inside the heat exchanger12. This not only can make further shorter the time lag, but can prevent freezing of the water inside the heat exchanger12securely. Thus, the hot water resupply performance is further enhanced. Moreover, since the activation time of the combustion fan13during the intermittent blower operation is further shortened, the power consumption and the noise during the intermittent blower operation are significantly reduced.

A water heater1according to a second embodiment of the present invention further includes, in addition to the function of the first embodiment, a function of setting the deactivation time of the combustion fan13in the intermittent blower operation to be longer, the activation time therein to be shorter, and the rotational speed therein to be lower as the heat exchanger temperature T1becomes lower. Particularly, the control circuit3further has, as circuit configurations, a second blowing interval-setting section configured to set the deactivation time of the combustion fan13during the intermittent blower operation in accordance with the heat exchanger temperature T1, and a second blowing amount-setting section configured to set the activation time and the rotational speed of the combustion fan13during the intermittent blower operation in accordance with the heat exchanger temperature T1. Meanwhile, since a basic configuration of the water heater1in the second embodiment to a fourth embodiment of the present invention is the same as that of the first embodiment, only a different configuration will be described.

FIGS. 4 and 5are flowcharts showing control operation after the combustion operation of the water heater1according to the second embodiment of the present invention stops.

When the water supply to the hot water supplying terminal P is stopped during the combustion operation and the burner11is extinguished, the post-purge operation is performed as in the first embodiment. As a result, if the heat exchanger temperature T1becomes lower than the reference temperature Ts, the intermittent blower operation is not performed, and numbers of activation C1, C2, C3of the combustion fan13in respective predetermined temperature conditions, which are stored in the memory, are reset to “0”. Moreover, the water heater1returns to the standby state for waiting for the resume of the water supply to the hot water supplying terminal P (ST201to ST203).

On the other hand, at the time point when the post-purge operation ends, if the heat exchanger temperature T1is the reference temperature Ts or higher (Yes in the step of ST202), the drain adhering to the surface of the heat exchanger12easily becomes the vapor. Therefore, the intermittent blower operation is performed in which the activation and the deactivation of the combustion fan13are repeated a plurality of times at the predetermined intervals. Specifically, if the heat exchanger temperature T1is the reference temperature Ts or higher, it is further determined whether or not the heat exchanger temperature T1is a first determination temperature Ta (here, 70 degrees Celsius) or higher (ST204).

If the heat exchanger temperature T1is the first determination temperature Ta or higher (Yes in the step of ST204), the amount of the vapor generated from the heat exchanger12is relatively large. Therefore, as in the steps from ST104to ST112in the first embodiment, the intermittent blower operation is performed while making the activation time of the combustion fan13shorter, the rotational speed lower, and the deactivation time longer in accordance with the increase in the number of activation (a first number of activation) C1of the combustion fan13in a first temperature condition (ST205to ST213).

If the heat exchanger temperature T1becomes lower than the first determination temperature Ta during the intermittent blower operation, or at the time point when the post-purge operation ends (No in the step of ST204), it is further determined whether or not the heat exchanger temperature T1is a second determination temperature Tb (here, 50 degrees Celsius) or higher (ST214).

If the heat exchanger temperature T1is the second determination temperature Tb or higher (Yes in the step of ST214), and the number of activation (a second number of activation) C2of the combustion fan13in a second temperature condition is “0” (Yes in the step of ST215), the control circuit3activates the combustion fan13for a fourth set activation time A4(here, 90 seconds) shorter than the third set activation time A3and at a fourth set rotational speed M4(here, 180 Hz) lower than the third set rotational speed M3, and subsequently, deactivates the combustion fan13for a fourth set deactivation time B4(here, 1000 seconds) longer than the third set deactivation time B3. Moreover, the control circuit3adds “1” to the stored second number of activation C2, and causes the memory to store the new C2. That is, the control circuit3sets the activation time of the combustion fan13to be shorter, the rotational speed to be lower, and the deactivation time to be longer by one level than the step of on/off operation in ST212to ST213in the first temperature condition to cause the combustion fan13to perform on/off operation (ST215to ST218).

Again, the determination as to whether or not the heat exchanger temperature T1is the reference temperature Ts or higher is performed. As a result, if the heat exchanger temperature T1is the reference temperature Ts or higher (Yes in the step of ST202), but is lower than the first determination temperature Ta, and the second determination temperature Tb or higher (No in the step of ST204and Yes in the step of ST214), and if the second number of activation C2is “1” (No in the step of ST215and Yes in the step of ST219), the control circuit3activates the combustion fan13for a fifth set activation time A5(here, 70 seconds) shorter than the fourth set activation time A4and at a fifth set rotational speed M5(here, 160 Hz) lower than the fourth set rotational speed M4, and subsequently, deactivates the combustion fan13for a fifth set deactivation time B5(here, 1200 seconds) longer than the fourth set deactivation time B4. Moreover, the control circuit3adds “1” to the stored second number of activation C2to cause the memory to store the new C2(ST219to ST221, ST218).

Subsequently, again, the determination as to whether or not the heat exchanger temperature T1is the reference temperature Ts or higher is performed. As a result, if the heat exchanger temperature T1is the reference temperature Ts or higher (Yes in the step of ST202), but is lower than the first determination temperature Ta, and the second determination temperature Tb or higher (No in the step of ST204and Yes in the step of ST214), and if the second number of activation C2is neither “0” nor “1” (No in both steps of ST215and ST219), the control circuit3activates the combustion fan13for a sixth set activation time A6(here, 50 seconds) shorter than the fifth set activation time A5and at a sixth set rotational speed M6(here, 140 Hz) lower than the fifth set rotational speed M5, and subsequently, deactivates the combustion fan13for a sixth set deactivation time B6(here, 1400 seconds) longer than the fifth set deactivation time B5(ST222to ST223). The determination as to whether or not the heat exchanger temperature T1is the reference temperature Ts or higher is then performed.

If the heat exchanger temperature T1becomes lower than the second determination temperature Tb during the intermittent blower operation, or at the time point when the post-purge operation ends (No in the step of ST214), and the number of activation (a third number of activation) C3of the combustion fan13in a third temperature condition is “0” (Yes in the step of ST224), the control circuit3activates the combustion fan13for a seventh set activation time A7(here, 40 seconds) shorter than the sixth set activation time A6and at a seventh set rotational speed M7(here, 130 Hz) lower than the sixth set rotational speed M6, and subsequently, deactivates the combustion fan13for a seventh set deactivation time B7(here, 1600 seconds) longer than the sixth set deactivation time B6. Moreover, the control circuit3adds “1” to the stored third number of activation C3to cause the memory to store the new C3. That is, the control circuit3sets the activation time of the combustion fan13to be shorter, the rotational speed to be lower, and the deactivation time to be longer by one level than the step of on/off operation in ST222to ST223in the second temperature condition to cause the combustion fan13to perform on/off operation (ST225to ST227).

Subsequently, again, the determination as to whether or not the heat exchanger temperature T1is the reference temperature Ts or higher is performed. As a result, if the heat exchanger temperature T1is the reference temperature Ts or higher (Yes in the step of ST202), but is lower than the second determination temperature Tb (No in both steps of ST204and ST214), and if the third number of activation C3is “1” (No in the step of ST224and Yes in the step of ST228), the control circuit3activates the combustion fan13for a eighth set activation time A8(here, 30 seconds) shorter than the seventh set activation time A7and at a eighth set rotational speed M8(here, 100 Hz) lower than the seventh set rotational speed M7, and subsequently, deactivates the combustion fan13for a eighth set deactivation time B8(here, 1800 seconds) longer than the seventh set deactivation time B7. Moreover, the control circuit3adds “1” to the stored third number of activation C3to cause the memory to store the new C3(ST228to ST230, ST227).

Subsequently, again, the determination as to whether or not the heat exchanger temperature T1is the reference temperature Ts or higher is performed. As a result, if the heat exchanger temperature T1is the reference temperature Ts or higher (Yes in the step of ST202), but is lower than the second determination temperature Tb (No in both steps of ST204and ST214), and if the third number of activation C3is neither “0” nor “1” (No in both steps of ST224and ST228), the control circuit3activates the combustion fan13for a ninth set activation time A9(here, 20 seconds) shorter than the eighth set activation time A8and at a ninth set rotational speed M9(here, 70 Hz) lower than the eighth set rotational speed M8, and subsequently, deactivates the combustion fan13for a ninth set deactivation time B9(here, 2000 seconds) longer than the eighth set deactivation time B8(ST231to ST232). The determination as to whether or not the heat exchanger temperature T1is the reference temperature Ts or higher is then performed.

According to the second embodiment, since as the temperature of the heat exchanger12becomes lower, the deactivation time of the combustion fan13during the intermittent blower operation becomes the longer, the activation time becomes the shorter, and the rotational speed becomes the lower, the excessive cooling of the water inside the heat exchanger12can more surely be prevented. This not only can make further shorter the time lag, but can prevent freezing of the water inside the heat exchanger12securely. Thus, the hot water resupply performance is further enhanced. Moreover, since the activation time of the combustion fan13is further shortened, the power consumption and the noise during the intermittent blower operation are significantly reduced.

According to the second embodiment, as the temperature of the heat exchanger12becomes lower, the deactivation time of the combustion fan13during the intermittent blower operation is set to be longer, the activation time is set to be shorter, and the rotational speed is set to be lower. The water heater1according to the third embodiment further includes, in addition to the function of the first embodiment, a function of setting the deactivation time of the combustion fan13in the intermittent blower operation to be longer, the activation time therein to be shorter, and the rotational speed therein to be lower as a combustion time F1of the burner11during the combustion operation becomes shorter. Particularly, the control circuit3further has, as circuit configurations, a clock section configured to measure the combustion time F1of the burner11during the combustion operation, a third blowing interval-setting section configured to set the deactivation time of the combustion fan13during the intermittent blower operation in accordance with the combustion time F1instead of the heat exchanger temperature T1, and a third blowing amount-setting section configured to set the activation time and the rotational speed of the combustion fan13during the intermittent blower operation in accordance with the combustion time F1instead of the heat exchanger temperature T1.

FIGS. 6 and 7are flowcharts showing control operation after the combustion operation of the water heater1according to the third embodiment of the present invention stops. In the water heater1, although not shown, measurement of the combustion time F1is performed from the time point when the water supply to the hot water supplying terminal P is started and the burner11is ignited to the time point when the water supply to the hot water supplying terminal P is stopped and the burner11is extinguished.

When the water supply to the hot water supplying terminal P is stopped during the combustion operation and the burner11is extinguished, the post-purge operation is performed as in the second embodiment. As a result, if the heat exchanger temperature T1becomes lower than the reference temperature Ts, the intermittent blower operation is not performed, and numbers of activation C1, C2, C3of the combustion fan13in respective predetermined combustion conditions, which are stored in the memory, are reset to “0”. Moreover, the water heater1returns to the standby state for waiting for the resume of the water supply to the hot water supplying terminal P (ST301to ST303).

On the other hand, at the time point when the post-purge operation ends, if the heat exchanger temperature T1is the reference temperature Ts or higher (Yes in the step of ST302), the drain adhering to the surface of the heat exchanger12easily becomes the vapor. Therefore, the intermittent blower operation is performed in which the activation and the deactivation of the combustion fan13are repeated a plurality of times at the predetermined intervals. Specifically, if the heat exchanger temperature T1is the reference temperature Ts or higher, it is further determined whether or not the combustion time F1is a first determination time Fa (here, 10 minutes) or longer (ST304).

If the combustion time F1is the first determination time Fa or longer (Yes in the step of ST304), the amount of the drain adhering to the surface of the heat exchanger12is relatively large and the amount of the vapor generated therefrom is relatively large. Therefore, as in the steps from ST205to ST213in the second embodiment, the intermittent blower operation is performed while making the activation time of the combustion fan13shorter, the rotational speed lower, and the deactivation time longer in accordance with the increase in the number of activation (a first number of activation) C1of the combustion fan13in a first combustion condition (ST305to ST313).

On the other hand, if the combustion time F1is less than the first determination time Fa (No in the step ST304), but is a second determination time Fb (here, 5 minutes) or longer (Yes in the step ST314), which is less than the first determination time Fa, as in the steps from ST215to ST223in the second embodiment, the control circuit3sets the activation time of the combustion fan13to be shorter, the rotational speed to be lower, and the deactivation time to be longer by one level than the step of on/off operation in ST312to ST313to cause the combustion fan13to perform on/off operation. That is, the intermittent blower operation is performed while making the activation time of the combustion fan13shorter, the rotational speed lower, and the deactivation time longer in accordance with the increase in the number of activation (a second number of activation) C2of the combustion fan13in a second combustion condition (ST315to ST323).

Further, if the combustion time F1is less than the second determination time Fb (No in the step ST314), as in the steps from ST224to ST232in the second embodiment, the control circuit3sets the activation time of the combustion fan13to be shorter, the rotational speed to be lower, and the deactivation time to be longer by one level than the step of on/off operation in ST322to ST323to cause the combustion fan13to perform on/off operation. That is, the intermittent blower operation is performed while making the activation time of the combustion fan13shorter, the rotational speed lower, and the deactivation time longer in accordance with the increase in the number of activation (a third number of activation) C3of the combustion fan13in a third combustion condition (ST324to ST332).

According to the third embodiment, as the combustion time F1of the burner11during the combustion operation becomes shorter, the deactivation time of the combustion fan13during the intermittent blower operation becomes the longer, the activation time becomes the shorter, and the rotational speed becomes the lower. Thus, as the water heater1according to the second embodiment, the hot water resupply performance is further enhanced. Moreover, the power consumption and the noise during the intermittent blower operation are significantly reduced.

According to the third embodiment, as the combustion time F1of the burner11during the combustion operation becomes shorter, the deactivation time of the combustion fan13during the intermittent blower operation is set to be longer, the activation time is set to be shorter, and the rotational speed is set to be lower. The water heater1according to a fourth embodiment further includes, in addition to the function of the first embodiment, a function of setting the deactivation time of the combustion fan13in the intermittent blower operation to be longer, the activation time therein to be shorter, and the rotational speed therein to be lower as an integrated combustion heat amount Q1of the burner11for a predetermined period of time before end of the combustion operation becomes lower. Particularly, the control circuit3further has, as circuit configurations, a combustion heat amount-calculating section configured to calculate the integrated combustion heat amount Q1for a time period from a predetermined time before the end of the combustion operation to the end of the combustion operation, a fourth blowing interval-setting section configured to set the deactivation time of the combustion fan13during the intermittent blower operation in accordance with the integrated combustion heat amount Q1instead of the combustion time F1, and a fourth blowing amount-setting section configured to set the activation time and the rotational speed of the combustion fan13during the intermittent blower operation in accordance with the integrated combustion heat amount Q1instead of the combustion time F1.

FIGS. 8 and 9are flowcharts showing control operation after the combustion operation of the water heater1according to the fourth embodiment of the present invention stops. In the water heater1, although not shown, when the water supply to the hot water supplying terminal P is started and the burner11is ignited, a combustion heat amount per unit of time is calculated, and when the burner is extinguished, the integrated combustion heat amount Q1of the burner11for the predetermined period of time (here, 10 minutes) before the extinction is calculated.

When the water supply to the hot water supplying terminal P is stopped during the combustion operation and the burner11is extinguished, the post-purge operation is performed as in the third embodiment. As a result, if the heat exchanger temperature T1becomes lower than the reference temperature Ts, the intermittent blower operation is not performed, and numbers of activation C1, C2, C3of the combustion fan13in respective predetermined combustion conditions, which are stored in the memory, are reset to “0”. Moreover, the water heater1returns to the standby state for waiting for the resume of the water supply to the hot water supplying terminal P (ST401to ST403).

On the other hand, at the time point when the post-purge operation ends, if the heat exchanger temperature T1is the reference temperature Ts or higher (Yes in the step of ST402), the drain adhering to the surface of the heat exchanger12easily becomes the vapor. Therefore, the intermittent blower operation is performed in which the activation and the deactivation of the combustion fan13are repeated a plurality of times at the predetermined intervals. Specifically, if the heat exchanger temperature T1is the reference temperature Ts or higher, it is further determined whether or not the integrated combustion heat amount Q1at the time point when the end of the combustion operation is a first determination heat amount Qa (here, 34.9 kW) or higher (ST404).

If the integrated combustion heat amount Q1is the first determination heat amount Qa or higher (Yes in the step of ST404), the amount of the drain adhering to the surface of the heat exchanger12is relatively large and the amount of the vapor generated therefrom is relatively large. Therefore, as in the steps from ST305to ST313in the third embodiment, the intermittent blower operation is performed while making the activation time of the combustion fan13shorter, the rotational speed lower, and the deactivation time longer in accordance with the increase in the number of activation (a first number of activation) C1of the combustion fan13in a first combustion condition (ST405to ST413).

On the other hand, if the integrated combustion heat amount Q1is lower than the first determination heat amount Qa (No in the step ST404), but is a second determination heat amount Qb (here, 11.6 kW) or higher (Yes in the step ST414), which is lower than the first determination heat amount Qa, as in the steps from ST315to ST323in the third embodiment, the control circuit3sets the activation time of the combustion fan13to be shorter, the rotational speed to be lower, and the deactivation time to be longer by one level than the step of on/off operation in ST412to ST413to cause the combustion fan13to perform on/off operation. That is, the intermittent blower operation is performed while making the activation time of the combustion fan13shorter, the rotational speed lower, and the deactivation time longer in accordance with the increase in the number of activation (a second number of activation) C2of the combustion fan13in a second combustion condition (ST415to ST423).

Further, if the integrated combustion heat amount Q1is lower than the second determination heat amount Qb (No in the step ST414), as in the steps from ST324to ST332in the third embodiment, the control circuit3sets the activation time of the combustion fan13to be shorter, the rotational speed to be lower, and the deactivation time to be longer by one level than the step of on/off operation in ST422to ST423to cause the combustion fan13to perform on/off operation. That is, the intermittent blower operation is performed while making the activation time of the combustion fan13shorter, the rotational speed lower, and the deactivation time longer in accordance with the increase in the number of activation (a third number of activation) C3of the combustion fan13in a third combustion condition (ST424to ST432).

According to the fourth embodiment, as the integrated combustion heat amount Q1of the burner11for the predetermined period of time before the end of the combustion operation becomes lower, the deactivation time of the combustion fan13during the intermittent blower operation becomes the longer, the activation time becomes the shorter, and the rotational speed becomes the lower. Thus, as the water heater1according to the third embodiment, the hot water resupply performance is further enhanced. Moreover, the power consumption and the noise during the intermittent blower operation are significantly reduced.

In the above-described embodiments, after the post-purge operation ends, if the heat exchanger temperature T1is the reference temperature Ts or higher, the intermittent blower operation is continuously started. However, the intermittent blower operation may be started after a predetermined standby time (e.g., 180 seconds) has passed since the post-purge operation ended. Moreover, in this case, the above-described standby time may be set to be larger, as the heat exchanger temperature T1at the end time of post-purge operation is lower, as the combustion time F1of the burner11during the combustion operation is shorter, or as the integrated combustion heat amount Q1of the burner11is lower. Since this further shortens the activation time of the combustion fan13, the power consumption and the noise during the intermittent blower operation can be reduced more.

Moreover, according to each of the above-described embodiments, in the intermittent blower operation, every time the activation and the deactivation of the combustion fan13are repeated, the activation time of the combustion fan13is set to be shorter, the rotational speed is set to be lower, and the deactivation time is set to be longer. However, every time the activation and the deactivation of the combustion fan13are repeated, at least one of the deactivation time, the rotational speed, and the activation time of the combustion fan13may be changed.

Moreover, in each of the embodiments, the temperature of the heat exchanger12is detected from the temperature of the hot water outlet pipe line27(a hot water outlet temperature). However, the temperature of the heat exchanger12may be detected from a temperature such as a surface temperature of the heat transfer fin120, a temperature around an outlet side of the sensible heat exchanging pipe line12A, a temperature around an outlet side of the latent heat exchanging pipe line12B, a surface temperature of a peripheral wall of the heat exchange chamber22, and the like

The present invention can be also applied to a water heater without the check valve15at the air introduction port211of the combustion chamber21. Moreover, the present invention is not limited to a combustion apparatus only having a hot-water supply function, and can be applied to a combustion apparatus having a bathwater reheating function. Moreover, the present invention can be applied to a heat source device for a room heater circulating hot water to a hot water heating terminal, a heat source device of a storage type water heater, or a heat source device only having a sensible heat exchanger.

As described in detail, the present invention is summarized as follows.

According to one aspect of the present invention, there is provided a combustion apparatus comprising:

a housing accommodating a burner configured to burn combustion gas and a heat exchanger configured to recover heat in combustion exhaust gas generated by the burner to heat water supplied from a water supply source;

a combustion fan configured to supply air for combustion of the burner into the housing,

the heat exchanger being disposed below the burner inside the housing, and

the combustion exhaust gas from the burner being supplied to the heat exchanger from above;

a post-purge operation-executing section configured to activate the combustion fan for a predetermined period of time after combustion operation of the burner stops; and

an intermittent blower operation-executing section configured to repeat activation and deactivation of the combustion fan a plurality of times at predetermined intervals after the post-purge operation ends.

In the downward combustion type combustion apparatus, after the post-purge operation ends, the vapor generated around the heat exchanger ascends inside the housing slowly. Therefore, as the above-described intermittent blower operation, even if the combustion fan is deactivated for a certain period of time after the combustion fan is activated, the vapor hardly reaches to an upstream side of the burner in a short time. Further, since the combustion fan is deactivated at the predetermined intervals, the excessive cooling of the water inside the heat exchanger can be prevented. This not only can make shorter the time lag till the hot water at the predetermined temperature is supplied to the hot water supplying terminal, but can prevent freezing of the water inside the heat exchanger. Moreover, since the activation time of the combustion fan required for the backflow prevention of the vapor is shortened, the power consumption and the noise during the intermittent blower operation are reduced.

Preferably, the combustion apparatus further comprises,

a blowing stop operation-executing section configured to stop the intermittent blower operation when a temperature of the heat exchanger becomes lower than a predetermined reference temperature in the intermittent blower operation.

As the temperature of the heat exchanger becomes lower, the amount of the vapor generated around the heat exchanger is decreased. Thus, according to the combustion apparatus described above, when the temperature of the heat exchanger becomes lower than the predetermined reference temperature in the intermittent blower operation, the intermittent blower operation is stopped to stop blowing into the housing thereafter. Thereby, the excessive cooling of the water inside the heat exchanger can more surely be prevented. Thus, it not only can make further shorter the time lag till the hot water at the predetermined temperature is supplied to the hot water supplying terminal, but can prevent freezing of the water inside the heat exchanger securely. Moreover, since the activation time of the combustion fan is further shortened, the power consumption and the noise during the intermittent blower operation are significantly reduced.

Preferably, the combustion apparatus further comprises,

a first blowing interval-setting section configured to set a deactivation time of the combustion fan to be gradually longer than that at initial deactivation in the intermittent blower operation.

After the end of the post-purge operation, the amount and the ascending speed of the vapor generated around the heat exchanger are decreased, as the temperature of the heat exchanger becomes lower. On the other hand, in the combustion apparatus described above, since every time the activation and the deactivation of the combustion fan are repeated, the deactivation time of the combustion fan is set to be longer, the excessive cooling of the water inside the heat exchanger can more surely be prevented. Thus, according to the combustion apparatus, it not only can make further shorter the time lag till the hot water at the predetermined temperature is supplied to the hot water supplying terminal, but can prevent freezing of the water inside the heat exchanger securely. Moreover, since the activation time of the combustion fan is further shortened, the power consumption and the noise during the intermittent blower operation are significantly reduced.

Preferably, the combustion apparatus further comprises,

a first blowing amount-setting section configured to set an activation time of the combustion fan to be gradually shorter than that at initial activation, and/or to set a rotational speed of the combustion fan to be gradually lower than that at the initial activation in the intermittent blower operation.

After the end of the post-purge operation, the amount and the ascending speed of the vapor generated around the heat exchanger are decreased, as the temperature of the heat exchanger becomes lower. On the other hand, in the combustion apparatus described above, since every time the activation and the deactivation of the combustion fan are repeated, the activation time of the combustion fan is set to be shorter and/or the rotational speed of the combustion fan is set to be lower, the excessive cooling of the water inside the heat exchanger can more surely be prevented. Thus, according to the combustion apparatus, it not only can make further shorter the time lag till the hot water at the predetermined temperature is supplied to the hot water supplying terminal, but can prevent freezing of the water inside the heat exchanger securely. Moreover, since an amount of the activation of the combustion fan becomes lower, the power consumption and the noise during the intermittent blower operation are significantly reduced.

Preferably, the combustion apparatus further comprises,

at least one of a second blowing interval-setting section configured to set the deactivation time of the combustion fan to be longer as the temperature of the heat exchanger is lower, and a second blowing amount-setting section configured to set the activation time of the combustion fan to be shorter and/or to set the rotational speed of the combustion fan to be lower as the temperature of the heat exchanger is lower, in the intermittent blower operation.

After the end of the post-purge operation, the amount and the ascending speed of the vapor generated around the heat exchanger are decreased, as the temperature of the heat exchanger becomes lower. On the other hand, in the combustion apparatus described above, since as the temperature of the heat exchanger is lower, at least one of a longer deactivation time of the combustion fan, a shorter activation time of the combustion fan, and a lower rotational speed of the combustion fan is set, the excessive cooling of the water inside the heat exchanger can more surely be prevented. Thus, according to the combustion apparatus, it not only can make further shorter the time lag till the hot water at the predetermined temperature is supplied to the hot water supplying terminal, but can prevent freezing of the water inside the heat exchanger securely. Moreover, since the amount of the activation of the combustion fan becomes lower, the power consumption and the noise during the intermittent blower operation are significantly reduced.

Preferably, the combustion apparatus further comprises,

at least one of a third blowing interval-setting section configured to set the deactivation time of the combustion fan to be longer as a combustion time of the burner during the combustion operation is shorter, and a third blowing amount-setting section configured to set the activation time of the combustion fan to be shorter and/or to set the rotational speed of the combustion fan to be lower as the combustion time of the burner during the combustion operation is shorter, in the intermittent blower operation.

As the combustion time of the burner during the combustion operation is shorter, the amount of the drain generated on the surface of the heat exchanger is decreased. Thus, after the end of the post-purge operation, the amount and the ascending speed of the vapor generated around the heat exchanger are decreased in accordance with the combustion condition. On the other hand, in the combustion apparatus described above, since as the combustion time of the burner during the combustion operation is shorter, at least one of the longer deactivation time of the combustion fan, the shorter activation time of the combustion fan, and the lower rotational speed of the combustion fan is set, the excessive cooling of the water inside the heat exchanger can more surely be prevented. This not only can make further shorter the time lag till the hot water at the predetermined temperature is supplied to the hot water supplying terminal, but can prevent freezing of the water inside the heat exchanger securely. Moreover, since the amount of the activation of the combustion fan is further shortened, the power consumption and the noise during the intermittent blower operation are significantly reduced.

Preferably, the combustion apparatus further comprises,

at least one of a fourth blowing interval-setting section configured to set the deactivation time of the combustion fan to be longer as an integrated combustion heat amount of the burner during the combustion operation is lower, and a fourth blowing amount-setting section configured to set the activation time of the combustion fan to be shorter and/or to set the rotational speed of the combustion fan to be lower as the integrated combustion heat amount of the burner during the combustion operation is lower, in the intermittent blower operation.

As the integrated combustion heat amount of the burner during the combustion operation is lower, the amount of the drain generated on the surface of the heat exchanger is decreased. Thus, after the end of the post-purge operation, the amount and the ascending speed of the vapor generated around the heat exchanger are decreased in accordance with the combustion condition. On the other hand, in the combustion apparatus described above, since as the integrated combustion heat amount of the burner during the combustion operation is lower, at least one of the longer deactivation time of the combustion fan, the shorter activation time of the combustion fan, and the lower rotational speed of the combustion fan is set, the excessive cooling of the water inside the heat exchanger can more surely be prevented. This not only can make further shorter the time lag till the hot water at the predetermined temperature is supplied to the hot water supplying terminal, but can prevent freezing of the water inside the heat exchanger securely. Moreover, since the amount of the activation of the combustion fan is further shortened, the power consumption and the noise during the intermittent blower operation are significantly reduced.

INDUSTRIAL APPLICABILITY

According to the present invention, a water heater excellent in superior hot water resupply performance, having low power consumption and low noise during operation can be provided.