The present disclosure relates to a combustion apparatus, and more particularly to a combustion apparatus including a gas backflow prevention valve (hereinafter, also referred to as “check valve”) in a supply and exhaust passage.
There has been known a configuration in which a combustion apparatus that burns a mixture of air and fuel such as gas includes a check valve to prevent gas backflow in a supply and exhaust passage. Japanese Patent Laying-Open No. 2018-31533 (PTL 1) describes the technique of detecting an open failure of a check valve based on an exhaust detection temperature, in a configuration including the check valve to prevent backflow of acidic water vapor around a heat exchanger.
Japanese Patent Laying-Open No. 2017-20693 (PTL 2) describes a structure of a check valve suitable for arrangement between a main body in which a burner is placed and a fan case that houses a fan that feeds a mixture of air for combustion and fuel into the burner.
According to the combustion apparatus described in PIT 1, the open failure of the check valve can be detected based on a behavior of the exhaust temperature when a fan is stopped. Specifically, whether or not the check valve is normally closed in response to a stop of the fan can be determined based on whether or not a temperature difference between the exhaust detection temperature and a room detection temperature is maintained at a value higher than a reference value.
However, the exhaust temperature changes depending on a condition of combustion by a burner, and the room temperature also changes depending on the season. Therefore, even when the check valve is normally closed, the temperature difference between the exhaust detection temperature and the room detection temperature is not caused in some cases. Therefore, erroneous detection of the open failure is concerned.
The present disclosure has been made to solve the above-described problem, and an object of the present disclosure is to enhance the accuracy of detection of an open failure of a check valve arranged in a supply and exhaust passage of a combustion apparatus.
According to an aspect of the present disclosure, a combustion apparatus includes: a combustion mechanism that burns a fuel; an air blowing fan that supplies air for combustion to the combustion mechanism; an exhaust vent; a check valve; and a controller. The exhaust vent is provided to discharge combustion gas in the combustion mechanism. The check valve is arranged in a supply and exhaust passage from the air blowing fan to the exhaust vent. The check valve is opened and closed in accordance with a relationship between a gas pressure in the supply and exhaust passage and a biasing force in a closing direction. The controller performs a failure diagnosis for detecting an open failure of the check valve when a phenomenon in which the gas pressure is lower than a predetermined normal pressure range is detected in a case where a rotation speed of the air blowing fan is within a predetermined diagnosis rotation speed region. The diagnosis rotation speed region is set within a rotation speed range of the air blowing fan in which a degree of opening of the check valve changes with an increase in a rotation speed of the air blowing fan when the check valve is normally opened and closed.
According to the present disclosure, in light of a characteristic relationship (P-Q characteristic) between a gas flow rate and the gas pressure in the rotation speed range of the air blowing fan in which the degree of opening of the check valve changes with the increase in the rotation speed of the air blowing fan, the open failure of the check valve arranged in the supply and exhaust passage of the combustion apparatus can be detected with high accuracy.
Embodiments of the present disclosure will be described in detail hereinafter with reference to the drawings, in which the same or corresponding portions are denoted by the same reference characters and description thereof will not be repeated in principle.
Referring to
Air blowing fan 11 is rotationally driven by a not-shown fan motor, to thereby supply air for combustion to burner 10. An amount of air blown from air blowing fan 11 is determined in accordance with a fan rotation speed. Heat exchanger 12 performs heat recovery from combustion gas generated by burner 10 and heats water flowing through heat exchanger 12. Thus, water heating apparatus 100a can heat water introduced through an incoming water passage and output hot water.
The combustion gas subjected to heat recovery is guided to exhaust vent 25 by exhaust passage 20 and discharged outside water heating apparatus 100a. As described above, in the combustion apparatus, a supply and exhaust passage from air blowing fan 11 to exhaust vent 25 is formed as a result of operation of air blowing fan 11 during a combustion operation by burner 10. In the combustion apparatus according to the present embodiment, check valve 30 that prevents air backflow is disposed in the supply and exhaust passage.
In the configuration example in
Referring to
Referring to
A stopper (not shown) held by a pillar-like support member is arranged on the upper surface side of check valve 30. When check valve 30 moves upward and abuts against the stopper, check valve 30 enters “open state” shown in
Until check valve 30 abuts against the stopper, check valve 30 is in an intermediate state shown in
Referring to
In a so-called common vent configuration as in
However, when there arises a so-called “open failure” in which check valve 30 is maintained in the open state though air blowing fan 11 is stopped, exhaust backflow may occur. Therefore, detection of the open failure is important in the configuration including check valve 30. When there arises a so-called “closed failure” in which check valve 30 is maintained in the closed state though air blowing fan 11 is operated, it is concerned that the combustion gas cannot be normally discharged. Therefore, it is preferable to automatically detect the closed failure, similarly to the open failure.
Referring again to
Rotation speed sensor 41 is arranged in air blowing fan 11, and current sensor 42 is arranged in a fan motor (not shown) that rotationally drives air blowing fan 11. Outputs of rotation speed sensor 41 and current sensor 42 are input to controller 50.
An amount of air required for combustion by burner 10 is proportional to an amount of fuel supplied to burner 10. Therefore, the rotation speed (hereinafter, also referred to as “fan rotation speed Nf”) of air blowing fan 11 is controlled to a target rotation speed set in accordance with the above-described amount of required air. For example, controller 50 controls the rotation speed of air blowing fan 11 by adjusting a driving voltage of the above-described fan motor such that a detection value of fan rotation speed Nf by rotation speed sensor 41 comes closer to the above-described target rotation speed. During this time, a driving current (hereinafter, also referred to as “fan current If”) of the fan motor of air blowing fan 11 is detected by current sensor 42.
As described above, fan rotation speed Nf is substantially proportional to the amount of air blown from air blowing fan 11, i.e., a flow rate (hereinafter, also referred to as “exhaust flow rate”) of the combustion gas. In addition, fan current If corresponds to a load of the fan motor, and increases and decreases in accordance with a flow path resistance in the supply and exhaust passage and the amount of air blown from air blowing fan 11.
Referring to
A characteristic line 103 indicates a P-Q characteristic when check valve 30 is maintained in the closed state (
A characteristic line 101 indicates a P-Q characteristic when check valve 30 is normal. In the normal state, check valve 30 changes from the closed state in
When exhaust flow rate Q increases and check valve 30 enters the open state in
In
As described above, exhaust flow rate Q can be indirectly detected based on fan rotation speed Nf. In addition, a state of exhaust pressure P can be indirectly detected based on fan current If. Therefore, in the combustion apparatus according to the first embodiment, the open failure and the closed failure of check valve 30 are detected based on the detection values of fan rotation speed Nf and fan current If of air blowing fan 11.
Referring to
In contrast, an Nf-If characteristic that corresponds to the P-Q characteristic at the time of the open failure (characteristic line 102 in
In addition, in the normal state, a load that increases the degree of opening of check valve 30 is applied to air blowing fan 11 (fan motor). Therefore, a rate (slope) of an increase in fan current If with respect to an increase in fan rotation speed Nf is higher in characteristic line 151 in the normal state than in characteristic line 152.
An Nf-If characteristic that corresponds to the P-Q characteristic at the time of the closed failure (characteristic line 103 in
Therefore, by setting a reference value Ifr (hereinafter, also referred to as “reference current value Ifr”) of fan current If at each fan rotation speed Nf in accordance with characteristic line 151, it is possible to equivalently distinguish between characteristic line 101 and characteristic lines 102 and 103 in
Referring to
Furthermore, determination of YES can also be made in S100 based on a condition that the elapsed time from a previous failure diagnosis or the number of times of turning on the power switch exceeds a predetermined reference value. With this, excessive execution of the failure diagnosis of check valve 30 can be avoided and periodic execution of the failure diagnosis of check valve 30 becomes possible. Alternatively, separately from turning on the power switch, determination of YES can be made in S100 whenever a certain time period elapses.
It is preferable that controller 50 forcibly makes determination of NO in S100 during the combustion operation by burner 10, even when the power switch is ON. However, the failure diagnosis can also be performed during the combustion operation by burner 10, if it does not cause any trouble in the combustion operation. While the combustion operation is not being performed, the operation condition (fan rotation speed) of air blowing fan 11 can be adjusted for the failure diagnosis, and thus, the effect of preventing erroneous failure detection in the failure diagnosis can be enhanced.
Alternatively, the failure diagnosis can be performed in response to a prescribed input operation to a not-shown remote controller of water heating apparatus 100a. When the input operation to the remote controller is detected, controller 50 can make determination of YES in S100. Thus, the failure diagnosis of check valve 30 can be performed in response to, for example, a prescribed input operation performed by an operator at the time of installation of water heating apparatus 100a and indicating that the failure diagnosis is a diagnosis at the time of installation.
When the failure diagnosis condition is satisfied (YES in S100), controller 50 operates air blowing fan 11 in S105. Thus, air blowing fan 11 is also started up during a time period other than the combustion operation by burner 10. When the failure diagnosis condition is not satisfied (NO in S100), S105 and the subsequent steps are not performed and the failure diagnosis of check valve 30 is not started up.
At the time of the failure diagnosis, in S110, controller 50 determines whether or not fan rotation speed Nf detected by rotation speed sensor 41 is within a predetermined diagnosis rotation speed region. The diagnosis rotation speed region can be predetermined within the range of Nf≤Nl shown in
When fan rotation speed Nf is within the diagnosis rotation speed region (YES in S110), controller 50 stores current fan rotation speed Nf in S120 and stores current fan current if detected by current sensor 42 in S130. In contrast, when fan rotation speed Nf is not within the diagnosis rotation speed region (NO in S110), execution of S120 and S130 is awaited.
In S140, controller 50 sets reference current value Ifr corresponding to fan rotation speed Nf stored in S120. Specifically, a characteristic relationship (Nf-Ifr characteristic) of the reference current value with respect to each fan rotation speed, which corresponds to characteristic line 151 in
Alternatively, in order to reflect a characteristic of an exhaust passage (shared gas tube 27 on the exhaust side in
In S150, controller 50 determines whether or not fan current If stored in S130 is within a normal current range including reference current value Ifr set in S140. Determination in S150 can be made based on, for example, whether or not a current difference |fr−If| between fan current If and reference current value Ifr is smaller than a predetermined determination value r. In this case, the normal current range is set at |fr−r<f<Ifr+r. When current difference |Ifr−If| is smaller than determination value r and fan current If is within the normal current range (YES in S150), it is determined in S170 that check valve 30 has “no abnormality”, and the current failure diagnosis is ended.
In contrast, when current difference |Ifr−If| is equal to or larger than determination value r (NO in S150), controller 50 determines whether or not fan current If is larger than reference current value Ifr in S160. When if is larger than Ifr (YES in S160), i.e., when fan current If is higher than the normal current range, controller 50 determines that the Nf-If characteristic is close to characteristic line 152 (
In contrast, when If is smaller than Ifr (NO in S160), controller 50 determines that the Nf-If characteristic is close to characteristic line 153 (
As to determination in S150 and S160, determination value r can also be made different between the If>Ifr side (i.e., open failure detection side) and the If<Ifr side (i.e., closed failure detection side), and the normal current range can also be set to be asymmetric with respect to reference current value Ifr. In this case, by first making determination in S160, and then, making determination in S150 using determination value r set in accordance with a result of determination in S160, determination of no abnormality (S170), detection of the open failure (S180) or detection of the closed failure (S190) can be made.
It is preferable to notify the user, the operator or the like of the failure diagnosis result of check valve 30, and particularly detection of the open failure or the closed failure in S180 or S190.
Referring to
Remote controller 200 is disposed on a wall surface of a bathroom. Remote controller 200 includes a power switch 202, operation switches 203 and 204, and a display 205. Power switch 202 and operation switches 203 and 204 can be typically implemented by a push button or a touch button. Display 205 can be implemented by, for example, a vacuum fluorescent display.
Remote controller 300 is disposed on, for example, a wall surface of a kitchen. Remote controller 300 includes a power switch 302 for turning on and off water heating apparatus 100a, an operation switch 303, and a display 305. Power switch 302 and operation switch 303 can be typically implemented by a push button or a touch button. Display 305 can be typically implemented by a liquid crystal panel.
Furthermore, each of remote controllers 200 and 300 has a not-shown communication adapter built thereinto, and thus, can be communicatively connected to a communication network (typically, the Internet) and a communication terminal through a wireless LAN router 330. For example, by using wireless LAN router 330 that establishes communication connection to Internet 350 as “network extender”, remote controllers 200 and 300 can be communicatively connected to a server 380 connected to Internet 350. As a result, remote control and remote monitoring of water heating apparatus 100a via server 380 become possible.
For example, by downloading prescribed application software into a communication terminal 400 (typically, a smartphone) communicatively connected to server 380, remote control and remote monitoring of water heating apparatus 100a from communication terminal 400 become possible. As to communication terminal 400, remote control and remote monitoring of water heating apparatus 100a can be performed from both a communication terminal 400b connected to Internet 350 using 4G communication or the like and a communication terminal 400a connected to wireless LAN router 330 using a wireless LAN.
In the configuration example in
It is to be noted that “open failure” is also caused by forgetting to place check valve 30 at the time of installation of water heating apparatus 100a. Therefore, at the time of detection of the open failure in S180, the contents of notification can also be changed based on whether or not the current failure diagnosis has been started up in response to the above-described prescribed input operation indicating that the current failure diagnosis is a diagnosis at the time of installation. Specifically, when the current failure diagnosis is a failure diagnosis at the time of installation, the contents of notification are set to seek confirmation as to whether or not placement of check valve 30 is forgotten. In the other cases, the contents of notification can be switched to provide a notification about the occurrence of the abnormality (open failure) in check valve 30. In the failure diagnosis at the time of installation, it is preferable to provide a notification by using remote controllers 200 and 300 and/or communication terminal 400, in the case of “no abnormality (S170)” as well. Furthermore, the above-described revision to the reference current characteristic in the failure diagnosis at the time of installation can also be enabled only when the operator has performed an input operation indicating confirmation that the installation is normal.
As described above, in the combustion apparatus according to the first embodiment, the accuracy of detection of the open failure of check valve 30 can be enhanced based on the P-Q characteristic in the exhaust passage, without using the exhaust temperature that depends on the situation of the combustion operation. Similarly, using the same approach based on the P-Q characteristic, the closed failure of check valve 30 can also be detected with high accuracy.
Furthermore, in the combustion apparatus according to the first embodiment, the failure diagnosis can be performed using the detection values by rotation speed sensor 41 and current sensor 42 of air blowing fan 11 that are normally arranged for control of air blowing fan 11. Therefore, arrangement of a new sensor for the failure diagnosis of check valve 30 is unnecessary, and thus, the combustion apparatus according to the first embodiment has a cost advantage.
In addition, in the combustion apparatus according to the first embodiment, the failure diagnosis can also be performed before the start of the combustion operation, unlike PTL 1 in which the presence or absence of a failure is determined based on a change in temperature situation at the end of a combustion operation. Therefore, a difference in operation condition of air blowing fan 11 caused by the combustion operation can be eliminated and erroneous detection of the abnormality of check valve 30 can be further prevented.
In the first embodiment, the failure diagnosis is performed based on the P-Q characteristic, using fan rotation speed Nf and fan current If. However, even when a pressure sensor is arranged in the exhaust passage, the similar failure diagnosis can be performed.
Comparing
Since the remaining configuration of water heating apparatus 100b according to the second embodiment is the same as that of water heating apparatus 100a according to the first embodiment, detailed description will not be repeated. In water heating apparatus 100b according to the second embodiment, the failure diagnosis of check valve 30 can be performed using the P-Q characteristic in
Referring to
In S145, controller 50 reads a reference pressure value Pr. Reference pressure value Pr is set to correspond to a constant pressure value Pt in the (b) intermediate state of characteristic line 101 in
In S155, controller 50 determines whether or not exhaust pressure Px stored in S135 is within a normal pressure range including reference pressure value Pr. For example, by comparing a pressure difference |Pr−Px| between exhaust pressure Px stored in S135 and reference pressure value Pr set in S145 with a predetermined determination value r*, it can be determined whether or not exhaust pressure Px is within the normal pressure range.
When pressure difference |Pr−Px| is smaller than determination value r* (YES in S155), it is determined that check valve 30 has “no abnormality” in S170 similar to that in
In contrast, when pressure difference |Pr−Px| is equal to or larger than determination value r* (NO in S155), controller 50 determines whether or not reference pressure value Pr is larger than exhaust pressure Px in S165. When Pr is larger than Px (YES in S165), controller 50 determines that exhaust pressure P is lower than the normal pressure range and the P-Q characteristic is close to characteristic line 102 (
In contrast, when Px is larger than Pr (NO in S165), controller 50 determines that exhaust pressure P is higher than the normal pressure range and the P-Q characteristic is close to characteristic line 103 (
Similarly to the first embodiment, as to determination in S155 and S165, determination value r* can also be made different between the Px<Pr side (i.e., open failure detection side) and the Pr<Px side (i.e., closed failure detection side), and the normal pressure range can also be set to be asymmetric with respect to reference pressure value Pr. In this case, by first making determination in S165, and then, making determination in S155 using determination value r* set in accordance with a result of determination in S165, determination of no abnormality (S170), detection of the open failure (S180) or detection of the closed failure (S190) can be made.
As described above, arrangement of pressure sensor 21 is necessary in the combustion apparatus according to the second embodiment, as compared with the first embodiment. However, the open failure of check valve 30 can be detected with high accuracy, more directly based on the P-Q characteristic in the exhaust passage. Furthermore, the closed failure of check valve 30 can also be detected with high accuracy, more directly based on the P-Q characteristic.
In addition, in the combustion apparatus according to the second embodiment, the failure diagnosis can also be performed before the start of the combustion operation, similarly to the first embodiment. Therefore, a difference in operation condition of air blowing fan 11 caused by the combustion operation can be eliminated and erroneous detection of the abnormality of check valve 30 can be further prevented.
In the first and second embodiments, description has been given of the configuration example in which check valve 30 is arranged at exhaust vent 25. However, check valve 30 can be arranged at an arbitrary position in the supply and exhaust passage from air blowing fan 11 to exhaust vent 25. In a third embodiment, a configuration of a combustion apparatus having a check valve built thereinto will be illustrated.
Referring to
Referring to
When the gas pressure generated as a result of operation of air blowing fan 11 exceeds biasing force 131, check valve 130 is opened and enters “intermediate state” in
Therefore, for the combustion apparatus according to the third embodiment as well, characteristic lines 101 to 103 (
Thus, in the combustion apparatus according to the third embodiment, the failure diagnosis of check valve 130 can be performed using fan rotation speed Nf and fan current If detected by rotation speed sensor 41 and current sensor 42, similarly to the first embodiment.
Alternatively, pressure sensor 21 similar to that in
Thus, the failure diagnosis of the check valve not driven by an actuator as described in the first and second embodiments is applicable to a check valve arranged at an arbitrary location in a supply and exhaust passage in a combustion apparatus including the configurations described in PTLs 1 and 2.
In addition, a configuration of a user interface similar to that in
It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
10 burner; 11 air blowing fan; 12 heat exchanger; 13 gas valve; 15 mixture passage; 20 exhaust passage; 21 pressure sensor, 25 exhaust vent; 27 shared gas tube (exhaust side); 28 shared gas tube (supply side); 30, 130 check valve; 31, 131 biasing force; 41 rotation speed sensor; 42 current sensor; 50 controller, 100a, 100b, 100c water heating apparatus; 101 to 103 characteristic line (P-Q); 151 to 153 characteristic line (Nf-If); 200, 300 remote controller; 202, 302 power switch; 203, 204, 303 operation switch; 205, 305 display; 210, 310 communication line; 330 LAN router; 350 Internet; 380 server; 400, 400a, 400b communication terminal; If fan current; Ifr reference current value (fan current); Nf fan rotation speed; P exhaust pressure (gas pressure); Q exhaust flow rate (gas flow rate).
Number | Date | Country | Kind |
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2018-157155 | Aug 2018 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2019/024304 | 6/19/2019 | WO |
Publishing Document | Publishing Date | Country | Kind |
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WO2020/039723 | 2/27/2020 | WO | A |
Number | Name | Date | Kind |
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4262843 | Omori | Apr 1981 | A |
20180187921 | Ojiro | Jul 2018 | A1 |
Number | Date | Country |
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2985529 | Feb 2016 | EP |
S49037379 | Apr 1974 | JP |
2004-271112 | Sep 2004 | JP |
2013-164178 | Aug 2013 | JP |
2017-020693 | Jan 2017 | JP |
2017-138012 | Aug 2017 | JP |
2018-031533 | Mar 2018 | JP |
2018138852 | Sep 2018 | JP |
Entry |
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International Search Report issued in PCT/JP2019/024304, dated Aug. 13, 2019. |
Number | Date | Country | |
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20210207803 A1 | Jul 2021 | US |