Combustion apparatus and hot water apparatus

A combustion apparatus includes a burner configured to produce flames, a first flame rod and a second flame rod, and a controller. The burner is configured to be controlled, by the controller, to be in a first output state, and a second output state in which output is smaller than in the first output state. The first flame rod makes contact with the flames produced at the burner in a normal combustion state. The second flame rod makes contact with the flames produced at the burner in the normal combustion state when the burner is being controlled to be in the first output state, and does not make contact with the flames produced at the burner in the normal combustion state when the burner is being controlled to be in the second output state.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a combustion apparatus and a hot water apparatus.

Description of the Background Art

Japanese Utility Model Laying-Open No. 56-149251 describes a safety device for a gas burner, which includes a burner, a first detection element, a second detection element, and a controller. The burner produces flames upward. The first detection element is arranged above the burner. The second detection element is arranged above the first detection element.

During normal combustion of the burner, the first detection element is in contact with the flames produced at the burner, whereas the second detection element is not in contact with the flames produced at the burner. During abnormal combustion (incomplete combustion) of the burner, the flames produced at the burner are extended. As a result, the flames produced at the burner and the second detection element come into contact with each other. By detecting the contact between the flames produced at the burner and the second detection element, the controller detects abnormal combustion of the burner.

The higher the degree of abnormal combustion (the lower the oxygen concentration), the further the extension of flames produced from the burner.

SUMMARY OF THE INVENTION

Even during normal combustion of a burner, flames produced at the burner are extended by increasing output of the burner. In the construction of the safety device for a gas burner described in Japanese Utility Model Laying-Open No. 56-149251, it is impossible to distinguish between the extension of flames due to increase in output of the burner and the extension of flames due to abnormal combustion of the burner, and it is thus difficult to address a problem when the burner has variable output.

The present invention was made in view of the problem with conventional techniques as described above. More specifically, the present invention aims to provide a combustion apparatus capable of detecting abnormal combustion of a burner when the burner has variable output.

A combustion apparatus according to one aspect of the present invention includes a burner configured to produce flames, a first flame rod and a second flame rod, and a controller. The burner is configured to be controlled, by the controller, to be in a first output state, and a second output state in which output is smaller than in the first output state.

The first flame rod is arranged at a position where it makes contact with the flames produced at the burner in a normal combustion state when the burner is being controlled to be in the first output state and the second output state. The second flame rod is arranged at a position where it makes contact with the flames produced at the burner in the normal combustion state when the burner is being controlled to be in the first output state, and does not make contact with the flames produced at the burner in the normal combustion state when the burner is being controlled to be in the second output state. The controller is configured to determine that the burner is in an abnormal combustion state when, with the burner being controlled to be in the second output state, it is detected that the second flame rod and the flames produced at the burner are in contact with each other.

In the combustion apparatus, the controller may be configured to determine that the burner is in the normal combustion state when, with the burner being controlled to be in the first output state, it is detected that the first flame rod and the flames produced at the burner are in contact with each other and the second flame rod and the flames produced at the burner are in contact with each other.

In the combustion apparatus, the controller may be configured to determine that the burner is in the abnormal combustion state when it is detected that the first flame rod and the flames produced at the burner are not in contact with each other.

The combustion apparatus may further include a heat exchanger having a first sidewall. In plan view, a portion of the first flame rod that is farthest from the first sidewall may be located farther from the first sidewall than a portion of the second flame rod that is farthest from the first sidewall.

In the combustion apparatus, the heat exchanger may further have a second sidewall facing the first sidewall. The burner may have a plurality of burner ports through which the flames are produced. In cross-sectional view parallel to a direction from the first sidewall toward the second sidewall, the portion of the first flame rod that is farthest from the first sidewall may be located closer to the second sidewall than a virtual line obtained by extending a central axis of one of the burner ports that is closest to the first sidewall. In cross-sectional view parallel to the direction from the first sidewall toward the second sidewall, the portion of the second flame rod that is farthest from the first sidewall may be located closer to the first sidewall than the virtual line.

The combustion apparatus may further include a heat exchanger having a first sidewall and a second sidewall facing the first sidewall, and an insulator portion having the second flame rod inserted therein. The heat exchanger may further have a shell pipe attached to a surface of the first sidewall on a side of the second sidewall. The insulator portion may be inserted in the first sidewall below the shell pipe. A portion of the second flame rod overlapping the shell pipe in plan view may be covered with the insulator portion.

A hot water apparatus according to one aspect of the present invention includes a combustion apparatus. This combustion apparatus is the combustion apparatus described above.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention will be described with reference to the drawings. The same or corresponding parts are denoted by the same reference characters in the following drawings, and redundant description is not repeated.

(General Construction of Hot Water Apparatus According to Embodiment)

In the following, a general construction of a hot water apparatus100according to the embodiment is described.

As shown inFIG. 1, hot water apparatus100includes a housing10, a combustion apparatus20, pipes40ato40g, a bypass pipe41aand a bypass pipe41b, and a bypass servo42.

Combustion apparatus20includes a burner21, an ignition plug22, a first flame rod23a(not shown inFIG. 1) and a second flame rod23b(not shown inFIG. 1), and a primary heat exchanger24. Combustion apparatus20further includes a secondary heat exchanger25, a chamber26, a fan27, a duct28, a venturi29, an orifice30, and a gas valve31.

Burner21is arranged below chamber26. Primary heat exchanger24is arranged below burner21. Ignition plug22is arranged below burner21. Ignition plug22is attached to primary heat exchanger24, for example. Secondary heat exchanger25is arranged below primary heat exchanger24.

Pipe40ahas one end from which fuel gas is supplied. Pipe40ahas the other end connected to gas valve31. Pipe40bhas one end connected to gas valve31. Pipe40bhas the other end connected to orifice30. Pipe40chas one end connected to orifice30. Pipe40chas the other end connected to venturi29.

Pipe40dhas one end connected to venturi29. Pipe40dhas the other end connected to fan27. Fan27is connected to chamber26.

Pipe40ehas one end from which water is supplied. Pipe40ehas the other end connected to secondary heat exchanger25. Pipe40fhas one end connected to secondary heat exchanger25. Pipe40fhas the other end connected to primary heat exchanger24. Pipe40ghas one end connected to primary heat exchanger24. Pipe40ghas the other end from which hot water exits.

Bypass pipe41ahas one end connected to pipe40e. Bypass pipe41ahas the other end connected to bypass servo42. Bypass pipe41bhas one end connected to bypass servo42. Bypass pipe41bhas the other end connected to pipe40g.

Gas valve31switches supply and stop of the fuel gas from pipe40a. The pressure of the fuel gas supplied to venturi29is thus regulated.

Venturi29is configured to take in air from the outside of housing10. Venturi29mixes the air taken in from the outside of housing10with the fuel gas supplied to venturi29through pipe40a, pipe40b, pipe40c, orifice30and gas valve31(the fuel gas mixed with the air is hereinafter referred to as mixed gas).

Exhaust from combustion apparatus20is discharged to the outside of housing10through duct28. Part of this exhaust, however, is taken in again through venturi29, which results in reduction in oxygen concentration in the mixed gas, causing abnormal combustion (incomplete combustion) which will be described later.

Fan27includes a fan case, an impeller arranged in the fan case, and a motor for driving the impeller to rotate. When the motor drives the impeller to rotate, fan27suctions the mixed gas produced at venturi29through pipe40c. The suctioned mixed gas is supplied to burner21through chamber26.

The mixed gas is ejected downward through burner ports21aprovided in a lower surface of burner21. The ejected mixed gas is burned by being ignited by ignition plug22, and turned into combustion gas. The combustion gas is ejected downward (i.e., toward primary heat exchanger24).

The water supplied to secondary heat exchanger25through pipe40eexchanges heat with latent heat of the combustion gas at secondary heat exchanger25, to thereby have an increased temperature. The water which has passed through secondary heat exchanger25is supplied to primary heat exchanger24through pipe40f. The water supplied to primary heat exchanger24exchanges heat with sensible heat of the combustion gas at primary heat exchanger24, to thereby have a further increased temperature. The water which has passed through primary heat exchanger24flows through pipe40g.

Part of the water flowing through pipe40eflows to bypass pipe41a. A flow rate of water flowing from bypass pipe41ato bypass pipe41bis controlled by bypass servo42. The water flowing through bypass pipe41bis mixed with the water flowing through pipe40g. That is, the temperature of the water exiting from the other end of pipe40gis adjusted by bypass servo42controlling the flow rate of the water flowing from bypass pipe41ato bypass pipe41b.

Water produced by condensation of water vapor in the combustion gas in primary heat exchanger24(this water is hereinafter referred to as drainage water) is discharged to the outside of housing10through duct28.

(Detailed Construction of Combustion Apparatus According to Embodiment)

In the following, a detailed construction of combustion apparatus20according to the embodiment is described with reference toFIGS. 2, 3 and 4. Secondary heat exchanger25, fan27, duct28, venturi29, orifice30and gas valve31are not shown inFIGS. 2 to 4. Chamber26is also not shown inFIG. 3in order to clarify an internal structure of combustion apparatus20.

Primary heat exchanger24has a first sidewall24a, a second sidewall24b, a third sidewall24c, and a fourth sidewall24d. First sidewall24aand second sidewall24bface each other in a first direction DR1. Third sidewall24cand fourth sidewall24dface each other in a second direction DR2intersecting with first direction DR1. Third sidewall24cis continuous with first sidewall24aand second sidewall24b, and fourth sidewall24dis continuous with first sidewall24aand second sidewall24b.

Primary heat exchanger24has a shell pipe24ea, a shell pipe24eband a shell pipe24ec. Shell pipe24ea, shell pipe24eband shell pipe24ecare attached along inner wall surfaces of first sidewall24a, second sidewall24band third sidewall24c.

The inner wall surface of first sidewall24arefers to a surface of first sidewall24aon a side of second sidewall24b, and the inner wall surface of second sidewall24brefers to a surface of second sidewall24bon a side of first sidewall24a. The inner wall surface of third sidewall24crefers to a surface of third sidewall24con a side of fourth sidewall24d, and the inner wall surface of fourth sidewall24drefers to a surface of fourth sidewall24don a side of third sidewall24c.

Shell pipe24ebis arranged below shell pipe24ea. Shell pipe24eaand shell pipe24ebare spaced from each other in an up-down direction. Shell pipe24ecis arranged below shell pipe24eb. Shell pipe24eband shell pipe24ecare spaced from each other in the up-down direction.

Primary heat exchanger24further has a shell pipe24edand a shell pipe24ee. Shell pipe24edand shell pipe24eeare attached to an outer wall surface of fourth sidewall24d. The outer wall surface of fourth sidewall24drefers to a surface of fourth sidewall24don a side opposite the side of third sidewall24c. Shell pipe24eeis located below shell pipe24ed. Shell pipe24edand shell pipe24eeare spaced from each other in the up-down direction.

Shell pipe24edhas one end connected to one end of shell pipe24ea. The other end of shell pipe24eais an end of shell pipe24eaon a side of a water outlet24h. Shell pipe24edhas the other end connected to one end of shell pipe24eb. Shell pipe24eehas one end connected to the other end of shell pipe24eb. Shell pipe24eehas the other end connected to one end of shell pipe24ec.

Primary heat exchanger24further has a pipe24f. Pipe24fis connected at its one end to the other end of shell pipe24ec, and is connected at its other end to a water inlet24g. A number of fins are attached to pipe24f.

Primary heat exchanger24further has water inlet24gand water outlet24h. Water inlet24gis connected to the other end of pipe24f. Water outlet24his connected to one end of pipe40g. Water inlet24gand water outlet24hare connected to each other through shell pipe24eato shell pipe24eeand pipe24f.

Chamber26has an intake port26a. The mixed gas supplied from fan27is supplied into chamber26through intake port26a. Burner21is attached below chamber26.

The lower surface of burner21is provided with the plurality of burner ports21a, as described above. The mixed gas supplied into chamber26is ejected through burner ports21a. The lower surface of burner21is curved in a downwardly convex manner in cross-sectional view along first direction DR1(cross-sectional view orthogonal to second direction DR2). A line obtained by extending a central axis of burner port21athat is closest to first sidewall24awill be referred to as a virtual line VL.

Ignition plug22is arranged below burner21, as described above. Ignition plug22is composed of a first electrode22aand a second electrode22b. First electrode22aand second electrode22beach have a tip end arranged inside combustion apparatus20, and each have the other end arranged outside combustion apparatus20.

The tip ends of first electrode22aand second electrode22bface each other. The tip ends of first electrode22aand second electrode22bare located below the lower surface of burner21. By passing a current between first electrode22aand second electrode22b, sparks are generated between the tip end of first electrode22aand the tip end of second electrode, leading to ignition of the mixed gas ejected through burner ports21a.

Ignition plug22(first electrode22aand second electrode22b) is inserted in first sidewall24a. More specifically, ignition plug22is inserted in first sidewall24abetween shell pipe24eaand shell pipe24eb.

First flame rod23ais inserted in chamber26. First flame rod23ahas a tip end arranged inside combustion apparatus20, and has the other end arranged outside combustion apparatus20. The other end of first flame rod23ais electrically connected to a controller5which will be described later.

The tip end of first flame rod23a(portion that is farthest from first sidewall24a) is located below burner21. Preferably, in cross-sectional view along first direction DR1, the tip end of first flame rod23a(portion that is farthest from first sidewall24a) is located closer to second sidewall24bthan virtual line VL. First flame rod23ais arranged at a position where it makes contact with the flames produced at burner21in a normal combustion state when burner21is being controlled to be in a first output state and a second output state which will be described later.

That burner21is in a normal combustion state means that incomplete combustion has not occurred in the fuel gas ejected through burner ports21a. That burner21is in an abnormal combustion state, on the other hand, means that incomplete combustion has occurred in the fuel gas ejected through burner ports21a. Here, the incomplete combustion means that carbon monoxide concentration in exhaust gas from the combustion apparatus is equal to or higher than the concentration that has an effect on the human body.

First flame rod23ais made of heat-resistant steel, for example. Since molecules forming the fuel gas are ionized in the flames produced at burner ports21a, the flames exhibit electrical conductivity. Thus, when first flame rod23ais in contact with the flames produced at burner ports21a, a current flows between first flame rod23aand an electrode (not shown) provided on a side of burner21. By detection of this current, it can be detected that first flame rod23aand the flames produced at burner ports21aare in contact with each other.

Second flame rod23bis inserted in first sidewall24a. More specifically, second flame rod23bis inserted in first sidewall24abetween shell pipe24eaand shell pipe24eb. Second flame rod23bhas a tip end arranged inside combustion apparatus20, and has the other end arranged outside combustion apparatus20. The other end of second flame rod23bis electrically connected to controller5which will be described later.

The tip end of second flame rod23b(portion that is farthest from first sidewall24a) is located below the tip end of first flame rod23a(portion that is farthest from first sidewall24a). As will be described later, burner21is controlled by controller5to be in the first output state, and the second output state in which the output is smaller than in the first output state (the flames produced at burner21are shorter than in the first output state). The control of the output state of burner21is performed by, for example, varying a flow rate of the mixed gas supplied to burner21.

Second flame rod23bis arranged at a position where it makes contact with the flames produced at burner21in the normal combustion state when burner21is being controlled to be in the first output state, and does not make contact with the flames produced at burner21in the normal combustion state when burner21is being controlled to be in the second output state.

In cross-sectional view along first direction DR1, the tip end of second flame rod23b(portion that is farthest from first sidewall24a) is preferably located closer to first sidewall24athan the tip end of first flame rod23a(portion that is farthest from first sidewall24a). That is, in cross-sectional view along first direction DR1, the tip end of first flame rod23a(portion that is farthest from first sidewall24a) is preferably located farther from first sidewall24athan the tip end of second flame rod23b(portion that is farthest from first sidewall24a). More specifically, in cross-sectional view along first direction DR1, the tip end of second flame rod23b(portion that is farthest from first sidewall24a) is preferably located closer to first sidewall24athan virtual line VL.

Second flame rod23bis made of heat-resistant steel, for example. When second flame rod23bis in contact with the flames produced at burner21, a current flows between second flame rod23band the electrode (not shown) provided on a side of burner21. By detection of this current, it can be detected that second flame rod23bis in contact with the flames produced at burner21.

Combustion apparatus20may further include an insulator portion6. Insulator portion6is made of an insulating material. Insulator portion6is attached to first sidewall24a. More specifically, insulator portion6is inserted in a through hole provided in first sidewall24abetween shell pipe24eaand shell pipe24eb. That is, insulator portion6and second flame rod23bare located below shell pipe24ea.

Insulator portion6has a first through hole, a second through hole and a third through hole. Second flame rod23bis inserted in the first through hole. First electrode22aand second electrode22bare inserted in the second through hole and the third through hole, respectively.

Second flame rod23bis inserted in insulator portion6in such a way that a portion of second flame rod23boverlapping shell pipe24eain plan view is covered with insulator portion6. Similarly, ignition plug22(first electrode22aand second electrode22b) is inserted in insulator portion6in such a way that a portion of ignition plug22overlapping shell pipe24eain plan view is covered with insulator portion6.

(Operation of Combustion Apparatus According to Embodiment)

In the following, the operation of combustion apparatus20according to the embodiment is described with reference toFIG. 5.

As shown inFIG. 5, fan27, first flame rod23aand second flame rod23bare connected to controller5. Controller5is composed of a microcontroller, for example.

Burner21is controlled to be in the first output state and the second output state by controller5controlling fan27. Burner21may be controlled to be in an output state different from the first output state and the second output state by controller5controlling fan27.

When burner21is being controlled to be in the second output state by controller5, and when burner21is in the normal combustion state, then first flame rod23amakes contact with the flames produced at burner21, whereas second flame rod23bdoes not make contact with the flames produced at burner21.

However, even when burner21is being controlled to be in the second output state by controller5, the flames produced at burner21and second flame rod23bmake contact with each other when burner21is in the abnormal combustion state. For this reason, controller5determines that burner21is in the abnormal combustion state when burner21is being controlled to be in the second output state, and when it is detected that second flame rod23bis in contact with the flames produced at burner21(that is, a current flowing through second flame rod23bis detected).

When burner21is being controlled to be in the first output state by controller5, second flame rod23bmakes contact with the flames produced at burner21even when burner21is in the normal combustion state. For this reason, controller5determines that burner21is in the normal combustion state when it is detected that first flame rod23ais in contact with the flames produced at burner21and the second flame rod is in contact with the flames produced at burner21(a current flowing through first flame rod23aand second flame rod23bis detected).

When burner21is in the abnormal combustion state, the base of the flames produced at burner21may be separated from the lower surface of burner21, making it impossible to detect the contact between first flame rod23aand the flames produced at burner21. For this reason, controller5determines that burner21is in the abnormal combustion state when it is detected that first flame rod23ais not in contact with the flames produced at burner21(that no current is flowing through first flame rod23a).

(Effect of Combustion Apparatus According to Embodiment)

In the following, the effect of combustion apparatus20according to the embodiment is described.

As described above, in combustion apparatus20, controller5determines whether or not burner21is in the abnormal combustion state by considering whether or not second flame rod23bis in contact with the flames produced at burner21, and the control state of burner21(whether it is in the first output state or in the second control state).

In combustion apparatus20, therefore, it is possible to distinguish between the contact of the flames produced at burner21with second flame rod23bdue to large output of burner21, and the contact of the flames produced at burner21with second flame rod23bdue to abnormal combustion of burner21. In this manner, according to combustion apparatus20, the abnormal combustion of burner21can be detected even when burner21has variable output.

In combustion apparatus20, by adjusting the distance between the tip end of first flame rod23aand the tip end of second flame rod23bin plan view, the degree of abnormal combustion of burner21that can be detected can be changed (seeFIG. 6). By positioning the tip end of second flame rod23bcloser to first sidewall24athan the tip end of first flame rod23a, therefore, it is possible to detect abnormal combustion of a degree that is difficult to detect using only first flame rod23a.

When second flame rod23bis located below shell pipe24ea, water droplets produced due to condensation on a surface of shell pipe24eamay drop to second flame rod23bfrom shell pipe24ealocated above second flame rod23b. These water droplets cause an electric leakage in second flame rod23b.

When the portion of second flame rod23boverlapping shell pipe24eain plan view is covered with insulator portion6, however, the contact between these water droplets and second flame rod23bis suppressed.

Although the embodiment of the present invention has been described as above, the embodiment described above can be modified in various manners. In addition, the scope of the present invention is not limited to the embodiment described above. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the meaning and scope equivalent to the terms of the claims.

INDUSTRIAL APPLICABILITY

The embodiment described above is applied particularly advantageously to a combustion apparatus and a hot water apparatus.

Although the embodiment of the present invention has been described, it should be understood that the embodiment disclosed herein is illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the meaning and scope equivalent to the terms of the claims.