JP7183894B2 - gas water heater - Google Patents

Description

The present invention relates to a gas water heater equipped with a sensor for detecting oxygen concentration.

Gas water heaters are designed to optimize combustion by detecting the oxygen concentration of combustion gas with an oxygen sensor such as an A/F sensor and adjusting the amount of gas supplied based on the detection results. There is (for example, see Patent Document 1).

JP-A-1-98818

The oxygen sensor described above needs to have the sensor element at an appropriate temperature (for example, 750° C.) in order to properly exhibit its performance. In other words, in order to improve the certainty of the detection result of the oxygen sensor and suitably realize optimization of combustion, it is necessary to raise the temperature of the sensor element.

Here, in the gas water heater, the temperature of the sensor element of the oxygen sensor may rise due to the heat of the combustion gas. However, considering the fact that the combustion gas is cooled by heat exchange between the combustion gas and the water passing through the hot water supply pipe or the water stored in the hot water tank, the temperature rise caused by the combustion gas may vary depending on the placement of the oxygen sensor. There is a concern that the temperature effect will not be exhibited well. In other words, in raising the temperature of the sensor element by the combustion gas, it is assumed that the restriction on the arrangement of the oxygen sensor becomes stronger. Although it is preferable that the detection by the oxygen sensor is performed in a state where there is little unevenness in the components of the combustion gas, it is not preferable that the restriction regarding the arrangement of the oxygen sensor becomes strong. Thus, in the configuration in which the temperature of the sensor element is raised by the combustion gas, there is still room for improvement in terms of increasing the degree of freedom in arranging the oxygen sensor.

The present invention has been made in view of the above problems, and its main object is to improve the degree of freedom in arranging the oxygen sensor in a structure in which the temperature of the sensor element of the oxygen sensor that detects the oxygen concentration is raised by combustion gas. To provide a gas water heater capable of

Means for solving the above problems will be described below.

The first means is
an exhaust passage for discharging combustion gas generated in the combustion chamber from the combustion chamber;
an oxygen sensor disposed in the exhaust passage for detecting the oxygen concentration of the combustion gas;
a combustion control unit that controls a combustion state in the combustion chamber based on the oxygen concentration detected by the oxygen sensor;
A gas water heater that generates hot water by heat exchange between combustion gas passing through the exhaust passage and water for hot water supply,
a supply passage which is provided separately from the exhaust passage and is configured so as to be able to raise the temperature of the sensor element of the oxygen sensor by supplying part of the combustion gas generated in the combustion chamber to the oxygen sensor; prepared,
The supply passage supplies the oxygen sensor from the combustion chamber through the supply passage to the oxygen sensor as compared with the amount of decrease in the temperature of the combustion gas that decreases while reaching the oxygen sensor from the combustion chamber through the exhaust passage. The amount of decrease in the temperature of the combustion gas, which decreases until the temperature is reached, is configured to be smaller.

According to the above configuration, the temperature of the oxygen sensor (sensor element) can be raised by supplying the oxygen sensor through the supply passage with the combustion gas having a higher temperature than the heat-exchanged combustion gas. By reducing the dependence on the combustion gas passing through the exhaust passage in this way, the temperature of the sensor element can be raised even if the oxygen sensor is arranged in the downstream portion of the exhaust passage (position where the combustion gas having undergone heat exchange passes). becomes possible. As a result, the degree of freedom in arranging the oxygen sensor can be favorably improved.

In addition, since the temperature raising effect of the combustion gas can be effectively exhibited, even if another temperature raising means such as an electric heater is used together, the power consumption of the temperature raising means can be suppressed while the oxygen sensor can be used. , the degree of freedom of arrangement can be preferably improved.

In the second means, the passage length of the supply passage is shorter than the passage length of the exhaust passage from the combustion chamber to the location where the oxygen sensor is arranged.

As shown in the above configuration, by making the passage length (total length) of the supply passage shorter than the passage length from the combustion chamber to the location where the oxygen sensor is arranged in the exhaust passage, the temperature of the combustion gas used to raise the temperature of the oxygen sensor Decrease can be suppressed. Further, shortening the overall length of the supply passage is advantageous in terms of rapidly supplying the combustion gas to the oxygen sensor and improving the responsiveness to temperature rise.

For example, even if a supply passage is arranged in the heat exchange area (heat exchange section) for the purpose of space saving, the amount of temperature decrease of the combustion gas passing through the supply passage is the same as the amount of temperature decrease of the combustion gas passing through the exhaust passage. can be made smaller. With such a configuration, it is not necessary to arrange the supply passage so as to actively bypass the area for heat exchange, and it is possible to suitably suppress the increase in size of the gas water heater.

In the third means, the supply passage has a higher thermal insulation than the exhaust passage.

As shown in the above configuration, since the supply passage has a higher thermal insulation than the exhaust passage, it is possible to suppress a decrease in the temperature of the combustion gas used to raise the temperature of the oxygen sensor.

For example, even if a supply passage is arranged in the heat exchange area (heat exchange section) for the purpose of space saving, the amount of temperature decrease of the combustion gas passing through the supply passage is the same as the amount of temperature decrease of the combustion gas passing through the exhaust passage. can be made smaller. With such a configuration, there is no need to arrange the supply passage so as to actively bypass the heat exchange area, and it is possible to suitably suppress the increase in size of the gas water heater.

In the fourth means, at least part of the supply passage is arranged in a heat exchange area where hot water is generated by heat exchange between combustion gas passing through the exhaust passage and water for supplying hot water. there is

If the supply passage is arranged in the heat exchange area on the premise of the second means or the third means, the amount of temperature reduction of the combustion gas passing through the supply passage is equal to the temperature reduction of the combustion gas passing through the exhaust passage. It can be small compared to quantity. Therefore, it is not necessary to arrange the supply passage so as to actively bypass the heat exchange area, and it is possible to suitably suppress the increase in size of the gas water heater.

In the fifth means, the supply passage is arranged outside a heat exchange area where hot water is generated by heat exchange between combustion gas passing through the exhaust passage and water for supplying hot water.

According to the above configuration, the temperature of the oxygen sensor can be preferably raised by supplying the oxygen sensor with the combustion gas that does not undergo heat exchange with the hot water supply water.

In the sixth means, the passage area of the supply passage is smaller than the passage area of the exhaust passage.

According to the above configuration, it is possible to suppress an increase in the flow rate of the combustion gas passing through the supply passage, and to secure the flow rate of the combustion gas in the exhaust passage for heat exchange. According to such a configuration, it is possible to prevent the temperature raising function of the oxygen sensor using the supply passage from hindering the improvement of the hot water generation efficiency of the water heater.

In the seventh means, a valve provided in the supply passage and capable of switching between an open state that allows passage of the combustion gas in the supply passage and a closed state that disallows passage of the combustion gas; and a control unit that performs opening/closing control.

According to the above configuration, by opening and closing the valve provided in the supply passage, it is possible to supply the combustion gas to the oxygen sensor or to stop the supply according to the operating conditions of the gas water heater. . As a result, it is possible to prevent the temperature raising function of the oxygen sensor using the supply passage from hindering the improvement of the hot water generation efficiency of the water heater.

In the eighth means, the oxygen sensor is provided with an electric heater for heating the sensor element,
The control unit places the valve in the open state and the heater in the non-energized state when boiling of water is started, and closes the valve on the basis that a predetermined switching condition is satisfied after the boiling of water is started. In addition, the heater is switched to an energized state.

Electric heaters require a large amount of power at low temperatures. If the capacity of the power supply is set assuming such a large amount of power, the size of the power supply unit becomes large. This is unfavorable in promoting miniaturization of the electrical configuration of, for example, a water heater. In addition, the configuration in which the combustion gas is always supplied through the supply passage may be disadvantageous in terms of improving the hot water generation efficiency. In the eighth means, heating by combustion gas is performed at the start of boiling water, and the valve is closed when a predetermined switching condition is satisfied.

For example, when the temperature of the oxygen sensor exceeds the reference temperature, the heat source may be switched assuming that the "predetermined switching condition" is met. A configuration may be adopted in which the heat source is switched as the "predetermined switching condition" when the time has elapsed.

In the ninth means, the oxygen sensor is provided with an electric heater for heating the sensor element,
An acquisition unit that acquires by detecting or estimating the temperature of the sensor element when boiling water is started,
The control unit has a determination unit that determines whether the temperature of the sensor element has reached a predetermined temperature based on the acquisition result of the acquisition unit when boiling water is started, and the determination unit determines whether the temperature reaches the predetermined temperature. When it is determined that the temperature has not reached the predetermined temperature, the valve is set to the open state and the heater is not energized, and when it is determined that the predetermined temperature has been reached, the valve is set to the closed state and the heater is energized. It is configured.

According to the above configuration, it is determined whether the temperature of the sensor element has reached a predetermined temperature when boiling water is started. Heating is performed by combustion gas, and when a predetermined temperature is reached, the valve is closed, the heater is energized, and heating is performed by electricity. can be suitably realized.

According to the tenth means, the outlet of the supply passage is connected to the middle position of the exhaust passage.

If the combustion gas flowing out of the supply passage is arranged to pass through the exhaust passage as described above, the combustion gas from the supply passage can be subjected to heat exchange after the temperature of the oxygen sensor is raised. In this way, by including the relatively high-temperature combustion gas for raising the temperature of the oxygen sensor in the target of heat exchange, it is possible to suitably suppress the decrease in the hot water generation efficiency caused by the temperature raising function using the supply passage.

According to the eleventh means, the outlet of the supply passage is connected to a portion of the exhaust passage that is in the vicinity of the location where the sensor is arranged.

According to the above configuration, it is possible to prevent the hot combustion gas flowing out from the supply passage from being mixed with the cold combustion gas passing through the exhaust passage. Therefore, it is possible to efficiently raise the temperature of the oxygen sensor.

According to the twelfth means, the oxygen sensor has a cover portion that covers the sensor element from the exhaust passage side, and the cover portion is formed with a through hole through which combustion gas can pass. , the outlet of the supply passage is arranged at a position deviated from a position directly below the cover portion.

According to the above configuration, it is possible to prevent water droplets falling from the oxygen sensor from entering the outlet of the supply passage and being blown to the oxygen sensor side by the combustion gas blown out from the supply passage. This is preferable for preventing the water droplets from passing through the through-holes of the cover portion and adhering to the sensor element.

According to the thirteenth means, the outlet of the supply passage is disposed upstream of the oxygen sensor in the flow direction of the combustion gas in the exhaust passage.

According to the thirteenth means, the combustion gas discharged from the supply passage moves to the oxygen sensor side together with the combustion gas flowing through the exhaust passage. If the combustion gas discharged from the supply passage does not interfere with the flow in the exhaust passage in this way, there is no need to increase the flow velocity of the combustion gas discharged from the supply passage to the exhaust passage. Reducing the flow velocity when discharged is advantageous in reducing the amount of combustion gas passing through the supply passage and suppressing a decrease in hot water generation efficiency.

Schematic diagram of a gas water heater. Schematic of a heat exchange part. FIG. 3 is a partially enlarged view of FIG. 2 showing an A/F sensor and its surroundings; 4 is a flowchart showing a temperature raising valve opening/closing process executed by a control unit; The schematic which shows the mode of temperature rise. Schematic diagram showing a difference in power consumption. Schematic which shows the modification of a supply pipe. Schematic which shows the modification of a supply pipe.

An embodiment will be described below with reference to the drawings. This embodiment is embodied as a hot water storage type gas water heater.

As shown in FIG. 1, the gas water heater 10 is provided with a hot water storage tank 21 for storing hot water. The hot water storage tank 21 is provided with a partition part 27 for vertically partitioning the inside of the hot water storage tank 21, and the combustion chamber 25 is below the partition part 27 and the hot water storage room 26 is above the partition part 27.例文帳に追加A water supply pipe 22 is connected to the lower portion of the hot water storage chamber 26 , and water is supplied from the tap through this water supply pipe 22 . A hot water supply pipe 23 connecting a faucet of a bath or the like and the hot water storage chamber 26 is connected to the upper part of the hot water storage chamber 26 , and hot water is supplied through the hot water supply pipe 23 .

An intake pipe 31 is connected to the combustion chamber 25 , and a blower 32 is arranged in the intake pipe 31 . The blower 32 is subject to drive control by the controller 71 and operates based on a drive signal from the controller 71 . External air is supplied to the combustion chamber 25 through the intake pipe 31 by operating the blower 32 . A nozzle 34 of a gas supply pipe 33 is connected to an intermediate position of the intake pipe 31 . A control valve 35 is provided in the gas supply pipe 33 , and the amount of gas supplied to the intake pipe 31 is adjusted by driving and controlling the control valve 35 by the control unit 71 .

The combustion chamber 25 is provided with a burner 36 and an ignition plug 37 for burning combustion air, which is a mixture of gas and air supplied to the combustion chamber 25 through the intake pipe 31 . Combustion gas generated in the combustion chamber 25 is discharged from the combustion chamber 25 through an exhaust pipe 41 (corresponding to an “exhaust passage”) connected to the combustion chamber 25 . The exhaust pipe 41 is arranged to pass through the hot water storage chamber 26 and is in contact with the water stored in the hot water storage chamber 26 . While the combustion gas is discharged through the exhaust pipe 41 , heat is exchanged between the combustion gas and water through the exhaust pipe 41 . This heat exchange heats the water in the hot water storage tank 21 to generate hot water. In this embodiment, the hot water storage chamber 26 corresponds to the "heat exchange area".

As shown in FIG. 2, the exhaust pipe 41 is folded back several times, and meanders left and right inside the hot water storage chamber 26 . This is a device for suppressing the moving speed of the combustion gas passing through the exhaust pipe 41 while increasing the passage length of the exhaust pipe 41 (the length from the inlet 42 to the outlet 43). FIG. 2 illustrates a case where the exhaust pipe 41 meanders left and right. A specific shape is arbitrary. For example, it can meander vertically or spirally.

The exhaust pipe 41 protrudes upward from the ceiling of the hot water storage tank 21, and an outlet 43 of the exhaust pipe 41 is formed in this projecting portion. An A/F sensor 61 (corresponding to an "oxygen sensor") for detecting the oxygen concentration of the combustion gas passing through the exhaust pipe 41 is arranged in a portion of the exhaust pipe 41 located in the hot water storage chamber 26 and close to the outlet 43. is set. The A/F sensor 61 is connected to the control section 71 , and the control section 71 controls the gas injection amount and the like based on the detection information from the A/F sensor 61 . This is intended to improve combustion efficiency. In order to improve the combustion efficiency using the A/F sensor 61, it is technically preferable to place the A/F sensor 61 away from the combustion chamber 25 and perform detection in a state where there is little unevenness in the components of the combustion gas. it makes sense.

Here, the structure of the A/F sensor 61 will be described with reference to FIG. The A/F sensor 61 has a sensor element 63 and a housing 62 that accommodates the sensor element 63. The housing 62 is fixed to the exhaust pipe 41 so as to protrude into the exhaust pipe 41. . A plurality of through-holes are formed in the housing 62 , and a guide portion 65 is provided for guiding combustion gas flowing into the housing 62 through the through-holes to the sensor element 63 .

In order for the A/F sensor 61 to exhibit its detection performance correctly, the sensor element 63 needs to be at an appropriate temperature (for example, 750°C). In other words, in order to improve the certainty of the detection result of the A/F sensor 61 and optimize the combustion, it is necessary to raise the temperature of the sensor element 63 to the appropriate temperature. In consideration of such circumstances, the A/F sensor 61 is provided with an electric heater 64 for raising the temperature of the sensor element 63 . The electric heater 64 is in contact with the sensor element 63, and the temperature of the sensor element 63 rises as the temperature of the electric heater 64 rises. The electric heater 64 is also connected to the control unit 71, and the control unit 71 switches between the energized state and the non-energized state. This makes it possible to raise the temperature of the sensor element 63 or maintain it at an appropriate temperature. Incidentally, the electric heater 64 and the sensor element 63 are in contact with each other through an intermediate layer, and when the temperature of the sensor element 63 rises, the temperature of the electric heater 64 also rises accordingly.

However, due to its characteristics, the electric heater 64 requires a large amount of electric power at low temperatures. If the capacity of the power supply is set assuming such a large amount of power, the size of the power supply unit becomes large. This is unfavorable in promoting miniaturization of the electrical configuration of, for example, gas water heaters. On the other hand, although the temperature of the sensor element 63 may rise due to the combustion gas passing through the exhaust pipe 41, a sufficient temperature rise cannot be expected from the heat-exchanged combustion gas. One of the features of the present embodiment is that it is devised to eliminate such various inconveniences. The device will be described below with reference to FIGS. 2 and 3. FIG.

As shown in FIG. 2, the gas water heater 10 includes, in addition to the exhaust pipe 41, a supply pipe 51 (a "supply passage") that supplies combustion gas generated in the combustion chamber 25 to the A/F sensor 61. equivalent) is provided. The inlet 52 of the supply pipe 51 is provided in the partition portion 27 like the inlet 42 of the exhaust pipe 41 and extends longitudinally from the inlet 52 . An outlet 53 of the supply pipe 51 is connected to a position in the exhaust pipe 41 near the A/F sensor 61 . Specifically, the outlet 53 is arranged at a position downstream and below the A/F sensor 61 in the flow path of the exhaust pipe 41, and the tip portion of the A/F sensor 61 is positioned on the extension thereof. (See Figure 3).

The combustion gas blown out from the outlet 53 of the supply pipe 51 into the exhaust pipe 41 traverses the inside of the exhaust pipe 41 toward the A/F sensor 61 and is supplied to the sensor element 63 through the guide portion 65. It will happen.

In addition, in the gas water heater 10 shown in the present embodiment, air may be taken in through the exhaust pipe 41 (so-called purging), and water may adhere to the A/F sensor 61 at this time. In the present embodiment, the outlet 53 is arranged at a position away from directly below the A/F sensor 61. Therefore, even if the water droplets fall, the water droplets will not adhere to the outlet 53. no. As a result, it is possible to prevent the outlet 53 from being clogged with water droplets and the water droplets from flying to the A/F sensor 61 when the combustion gas is blown out.

The supply pipe 51 has higher heat insulation than the exhaust pipe 41 . In other words, the supply pipe 51 has a lower thermal conductivity (heat exchange coefficient) than the exhaust pipe 41 . In other words, while the exhaust pipe 41 is configured to facilitate heat exchange with the water in the hot water storage chamber 26, the supply pipe 51 is configured to prevent heat exchange with the water in the hot water storage chamber 26. there is This prevents the supplied combustion gas from cooling while passing through the hot water storage chamber 26 .

Further, the supply pipe 51 is configured to have a total length shorter than the passage length from the inlet 42 to the A/F sensor 61 in the exhaust pipe 41 . As a result, the combustion gas passing through the supply pipe 51 can be quickly delivered to the A/F sensor 61 . In particular, the supply pipe 51 has a straight structure in which most of the supply pipe 51 including the inlet 52 extends upward, and is not provided with a fold like the exhaust pipe 41 . As a result, the flow of the combustion gas flowing into the supply pipe 51 through the inlet 52 is made smoother.

With these measures, compared to the amount of temperature decrease of the combustion gas that decreases while it reaches the A/F sensor 61 from the combustion chamber 25 through the exhaust pipe 41, the A/F from the combustion chamber 25 through the supply pipe 51 The amount of decrease in the temperature of the combustion gas, which decreases before being supplied to the sensor 61, is smaller. That is, the temperature of the combustion gas supplied to the A/F sensor 61 through the supply pipe 51 is differentiated so as to be higher than the temperature of the combustion gas that reaches the position of the A/F sensor 61 through the exhaust pipe 41. ing. In particular, when the temperature of the water in the hot water storage chamber 26 is low, that is, immediately after the gas water heater 10 starts producing hot water, the above-described difference becomes significant.

In addition, the inner diameter of the supply pipe 51 is smaller than the inner diameter of the exhaust pipe 41, so that excessively large amount of combustion gas flows into the supply pipe 51 side, thereby suppressing the deterioration of hot water production efficiency.

A valve 55 is provided in the supply pipe 51 (more specifically, near the inlet 52). The valve 55 can be switched between an open state that allows combustion gas to flow into the supply pipe 51 and a closed state that prevents it. The valve 55 is connected to the control unit 71, and the control unit 71 executes drive control processing of the valve 55 (heating valve opening/closing control processing). This process is a process executed by the control unit 71 as part of regular processing. Hereinafter, the temperature raising valve opening/closing control process will be described with reference to FIG.

In the temperature raising valve opening/closing control process, first, in step S101, it is determined whether or not the temperature raising valve 55 is open. If it is in the open state, an affirmative determination is made in step S101 and the process proceeds to step S102. In step S102, it is determined whether or not it is time to start boiling water. If a negative determination is made in step S102, the main opening/closing control process is terminated. If an affirmative determination is made in step S102, the process proceeds to step S103.

In step S103, it is determined whether the temperature of the A/F sensor 61 (specifically, the sensor element 63) is lower than the reference temperature based on the detection information from the temperature sensor 68 (see FIG. 3) attached to the A/F sensor 61. judge. In the present embodiment, the reference temperature is set at 750° C., which is an appropriate temperature for properly exhibiting the detection performance of the A/F sensor. When an affirmative determination is made in step S103, the process proceeds to step S104, and after switching the valve 55 to the open state, the present opening/closing control process ends. By executing this switching process, the combustion gas generated in the combustion chamber 25 is supplied to the A/F sensor 61 through the supply pipe 51, and the temperature of the A/F sensor 61 is raised by the combustion gas. (See FIG. 5(a)). Note that while the temperature is being raised by the combustion gas using the supply pipe 51, the temperature is not raised by the electric heater 64.

Returning to the description of step S101, if the valve 55 is open, an affirmative determination is made in step S101, and the process proceeds to step S105. In step S105, it is determined whether or not the temperature of the A/F sensor 61 (specifically, the sensor element 63) has reached the reference temperature. If the temperature has not reached the reference temperature, a negative determination is made in step S105, and the main opening/closing control process ends. If the temperature has reached the reference temperature, the process proceeds to step S106, and the valve 55 for raising the temperature is switched to the closed state. This completes the temperature rise by the combustion gas using the supply pipe 51 (see FIG. 5(b)). Note that the valve 55 is also switched to the closed state when the boiling of the water ends.

In the following step S107, the temperature rise mode using the electric heater 64 is entered. In other words, after reaching the reference temperature, the temperature is maintained by the electric heater 64 . Here, when boiling water is repeated in a short span such as when a large amount of hot water is used at once, there is a possibility that the temperature of the A/F sensor 61 has reached the reference temperature even at the timing when boiling water is started. There is In such a case, a negative determination is made in step S103, and the process of step S107 is executed so that the electric heater 64 is used without raising the temperature by the combustion gas using the supply pipe 51. Switch to heating mode.

According to the embodiment detailed above, the following excellent effects can be obtained.

The temperature of the sensor element 63 can be raised by supplying the A/F sensor 61 through the supply pipe 51 with the combustion gas having a higher temperature than the heat-exchanged combustion gas. In this way, by reducing dependence on the combustion gas passing through the exhaust pipe 41 for the temperature rise of the sensor element 63, for example, the A/F sensor is located downstream of the exhaust pipe 41 (the position where the combustion gas having undergone heat exchange passes). Even if 61 is arranged, it is possible to sufficiently raise the temperature of the sensor element 63 .

Power consumption by the electric heater 64 can be suppressed by making good use of the temperature raising effect of the combustion gas. Specifically, as shown in the comparative example of FIG. 6A, when the electric heater 64 is at a low temperature, the electric resistance of the electric heater 64 is small and a large current (for example, 10 A) flows. This tendency is particularly noticeable in cold regions. When a large amount of current flows, power consumption increases, and if an attempt is made to cope with such a large amount of power, the size of the power supply section (AC-DC converter) will also increase. Here, after the A/F sensor 61 has warmed up to the reference temperature, it is sufficient to maintain the temperature instead of raising the temperature. At this time, the temperature of the electric heater 64 placed in contact with the sensor element 63 also rises, and the electric resistance of the electric heater 64 increases. As a result, the power consumed by the electric heater 64 is greatly reduced. In this embodiment, as shown in FIG. 6(b), when the temperature reaches the reference temperature, the mode shifts to the temperature raising mode by the electric heater 64, so there is no need to consider the part where the power consumption becomes excessively large. This suppresses an increase in the size of the power supply unit.

Note that switching the temperature rising mode to the temperature rising mode using the electric heater 64 after reaching the reference temperature has technical significance in that the temperature control stability of the sensor element 63 can be improved.

By making the passage length (total length) of the supply pipe 51 shorter than the passage length from the combustion chamber 25 to the A/F sensor 61 in the exhaust pipe 41, the temperature decrease of the combustion gas used to raise the temperature of the A/F sensor 61 can be suppressed. can be suppressed. Further, shortening the overall length of the supply pipe 51 is advantageous in terms of rapidly supplying the combustion gas to the A/F sensor 61 and improving the responsiveness of temperature rise.

The supply pipe 51 shown in this embodiment has higher heat insulation than the exhaust pipe 41 . Therefore, even if the supply pipe 51 is arranged in the hot water storage chamber 26 which is the heat exchange area for the purpose of space saving, the amount of temperature decrease of the combustion gas passing through the supply pipe 51 is equal to that of the combustion gas passing through the exhaust pipe 41. It can be smaller than the amount of temperature drop. Therefore, it is not necessary to arrange the supply pipe 51 so as to positively bypass the hot water storage chamber 26, and it is possible to suitably suppress an increase in the size of the gas water heater.

By opening and closing a valve 55 provided in the supply pipe 51, it is possible to supply combustion gas to the A/F sensor 61 or stop the supply in accordance with the operating conditions of the gas water heater 10. . If the supply pipe 51 is used under such limited conditions, the temperature raising function of the A/F sensor 61 using the supply pipe 51 can improve the efficiency of hot water generation in the gas water heater 10. can be suppressed.

If the combustion gas flowing out from the supply pipe 51 is arranged to pass through the exhaust pipe 41, the combustion gas from the supply pipe 51 can be subjected to heat exchange after the temperature of the A/F sensor 61 is raised. In this way, by including the relatively high-temperature combustion gas for raising the temperature of the A/F sensor 61 in the target of heat exchange, it is possible to reduce the efficiency of hot water generation due to the temperature raising function using the supply pipe 51. can be suppressed to

An outlet 53 (blowout port) of the supply pipe 51 is connected to a portion of the exhaust pipe 41 near the location where the A/F sensor 61 is arranged. With such a configuration, it is possible to prevent the hot combustion gas flowing out of the supply pipe 51 from being mixed with the cold combustion gas passing through the exhaust pipe 41 . Therefore, the temperature of the A/F sensor 61 can be efficiently raised.

<Other embodiments>
In the above embodiment, the following three configurations are applied to the gas water heater so that the heat exchange rate of the combustion gas passing through the supply pipe 51 is lower than that of the combustion gas passing through the exhaust pipe 41. . That is, (1) the total length of the supply pipe 51 is made shorter than the length of the path from the inlet 42 of the exhaust pipe 41 to the A/F sensor 61, and (2) the thermal conductivity of the supply pipe 51 is equal to the thermal conductivity of the exhaust pipe 41. (3) The supply pipe 51 is mainly vertically oriented and the exhaust pipe 41 is mainly horizontally oriented so that the flow velocity of the supply pipe 51 is higher than the flow velocity of the exhaust pipe 41 . If the heat exchange rate of the combustion gas passing through the supply pipe 51 can be made lower than the heat exchange rate of the combustion gas passing through the exhaust pipe 41, it is not necessary to apply all of these three configurations.

- In the above-described embodiment, the entire supply pipe 51 is configured to pass through the hot water storage chamber 26 (corresponding to the "heat exchange area"), but the present invention is not limited to this. In order to suppress the temperature drop when passing through the hot water storage chamber 26, as shown in FIG. can also be arranged.

- In the above-described embodiment, the configuration is such that switching between the temperature raising mode by the electric heater 64 and the temperature raising mode by the combustion gas is performed, but the present invention is not limited to this. It is also possible to omit the electric heater 64 and employ a configuration in which the supply pipe 51 constantly raises the temperature. In this case, after the temperature of the A/F sensor 61 reaches the reference temperature, it is assumed that the amount of combustion gas that needs to be supplied from the supply pipe 51 will decrease. Therefore, after reaching the reference temperature, it is preferable to reduce the flow rate of the combustion gas passing through (inflowing) the supply pipe 51 by adjusting the throttle amount of the valve 55 .

In the above embodiment, the outlet 53 of the supply pipe 51 is located downstream of the A/F sensor 61 in the flow direction of the exhaust pipe 41. It is also possible to dispose at a position upstream of the A/F sensor 61 in the direction of the flow path. For example, as shown in FIG. 8, the outlet 53B of the supply pipe 51B may be disposed on the side of the A/F sensor 61, and the combustion gas blown out from the outlet 53B may traverse the central portion of the exhaust pipe 41. It is preferable to have a configuration in which the air is sprayed onto the A/F sensor 61 without any air. With such a configuration, it is possible to multiply the flow of combustion gas flowing in the exhaust pipe 41 and deliver the combustion gas for raising the temperature to the A/F sensor 61 . As a result, even if the flow velocity of the combustion gas passing through the outlet 53B is low, the combustion gas can reach the A/F sensor 61, so that the amount of combustion gas for raising the temperature can be reduced. This is preferable for improving the hot water production efficiency in the gas water heater 10 .

In the above-described embodiment, the outlet 53 of the supply pipe 51 is connected to the exhaust pipe 41, and the combustion gas for raising the temperature is supplied to the A/F sensor 61 through the flow path in the exhaust pipe 41. , the position of the outlet 53 of the supply pipe 51 is arbitrary as long as the temperature of the A/F sensor 61 can be increased. For example, it is possible to configure the supply to the A/F sensor 61 so as not to pass through the flow path in the exhaust pipe 41 .

- In the above embodiment, the inner diameter of the supply pipe 51 is made smaller than the inner diameter of the exhaust pipe 41, but it is not limited to this. The inner diameter of the supply pipe 51 may be the same as the inner diameter of the exhaust pipe 41 or may be larger than the inner diameter of the exhaust pipe 41 .

- In the above embodiment, the reference temperature is 750°C, but the reference temperature may be lower than 750°C (for example, 740°C) or higher than 750°C ( e.g. 760°C). Further, the reference temperature may not be fixed, but may be changed according to the temperature of the combustion gas. For example, if the temperature of the combustion gas changes around 500°C without exceeding 750°C due to the use environment, the type of fuel, etc., the reference temperature should be changed from 750°C to 500°C.

・In the above embodiment, the heat source for raising the temperature is switched when the temperature of the A/F sensor 61 exceeds the reference temperature. may be configured to switch the heat source for raising the temperature when the time elapses. This reference time is desirably determined based on the time required for the temperature of the A/F sensor 61 to reach the reference temperature after the temperature rise is started. For example, the required time is mapped in advance according to the relationship between the measured values of the hot water temperature and amount of hot water in the hot water storage chamber 26 and the set values of the target hot water temperature and target hot water amount set by the user. It is preferable to use a configuration in which one of these required times is selected by the user.

- In the above embodiment, the case where the A/F sensor 61 is used as the "oxygen sensor" was exemplified, but instead of the A/F sensor 61, an O2 concentration sensor may be used. The performance of the O2 concentration sensor can be correctly exhibited by raising the temperature to about 600°C. Therefore, when using an O2 concentration sensor, it is preferable to set the reference temperature to about 600°C.

- In the above embodiment, the temperature of the A/F sensor 61 is raised by the combustion gas passing through the supply pipe 51 at the start of boiling water, but the present invention is not limited to this. For example, when the gas water heater 10 is activated (initial activation), it is possible to adopt a configuration in which the temperature of the A/F sensor 61 is raised by combustion gas.

- The heat of the combustion gas passing through the exhaust pipe 41 may be used for preheating (preheating) water.

- The application target of the temperature increasing structure of the A/F sensor 61 using the supply pipe 51 is not limited to the hot water storage type gas water heater. A similar configuration can also be applied to an instantaneous water heater type gas water heater.

- In the above embodiment, the temperature sensor 68 measures the temperature of the A/F sensor 61. However, it is also possible to estimate the temperature from the resistance value of the resistor that constitutes the A/F sensor.

10 Gas water heater 25 Combustion chamber 26 Hot water storage chamber (heat exchange area) 41 Exhaust pipe (exhaust passage) 51 Supply pipe (supply passage) 53 Air outlet (exit) 55 Control Valve (valve) 61... A/F sensor (oxygen sensor) 62... Housing (cover part) 63... Sensor element 64... Electric heater (heater) 68... Temperature sensor (acquisition part) 71... Control part (combustion control unit).

Claims (15)

an exhaust passage for discharging combustion gas generated in the combustion chamber from the combustion chamber;
an oxygen sensor disposed in the exhaust passage for detecting the oxygen concentration of the combustion gas;
a combustion control unit that controls a combustion state in the combustion chamber based on the oxygen concentration detected by the oxygen sensor;
A gas water heater that generates hot water by heat exchange between combustion gas passing through the exhaust passage and water for hot water supply,
a supply passage which is provided separately from the exhaust passage and is configured so as to be able to raise the temperature of the sensor element of the oxygen sensor by supplying part of the combustion gas generated in the combustion chamber to the oxygen sensor; prepared,
The supply passage supplies the oxygen sensor from the combustion chamber through the supply passage to the oxygen sensor as compared with the amount of decrease in the temperature of the combustion gas that decreases while reaching the oxygen sensor from the combustion chamber through the exhaust passage. It is configured so that the amount of decrease in the temperature of the combustion gas that decreases until the
The gas water heater, wherein the length of the supply passage is shorter than the length of the exhaust passage from the combustion chamber to the position where the oxygen sensor is arranged. 2. The gas water heater according to claim 1 , wherein said supply passage has higher thermal insulation than said exhaust passage. an exhaust passage for discharging combustion gas generated in the combustion chamber from the combustion chamber;
an oxygen sensor disposed in the exhaust passage for detecting the oxygen concentration of the combustion gas;
a combustion control unit that controls a combustion state in the combustion chamber based on the oxygen concentration detected by the oxygen sensor;
with
A gas water heater that generates hot water by heat exchange between combustion gas passing through the exhaust passage and water for hot water supply,
a supply passage which is provided separately from the exhaust passage and is configured so as to be able to raise the temperature of the sensor element of the oxygen sensor by supplying part of the combustion gas generated in the combustion chamber to the oxygen sensor; prepared,
The supply passage supplies the oxygen sensor from the combustion chamber through the supply passage to the oxygen sensor as compared with the amount of decrease in the temperature of the combustion gas that decreases while reaching the oxygen sensor from the combustion chamber through the exhaust passage. It is configured so that the amount of decrease in the temperature of the combustion gas that decreases until the
The gas water heater, wherein the supply passage has higher thermal insulation than the exhaust passage . At least a portion of the supply passage is disposed in a heat exchange area where hot water is generated by heat exchange between combustion gas passing through the exhaust passage and water for supplying hot water. Item 4. The gas water heater according to any one of items 3 . The supply passage according to any one of claims 1 to 3, wherein the supply passage is arranged outside a heat exchange area where hot water is generated by heat exchange between combustion gas passing through the exhaust passage and water for supplying hot water. Gas water heater as described. an exhaust passage for discharging combustion gas generated in the combustion chamber from the combustion chamber;
an oxygen sensor disposed in the exhaust passage for detecting the oxygen concentration of the combustion gas;
a combustion control unit that controls a combustion state in the combustion chamber based on the oxygen concentration detected by the oxygen sensor;
with
A gas water heater that generates hot water by heat exchange between combustion gas passing through the exhaust passage and water for hot water supply,
a supply passage that is provided separately from the exhaust passage and configured to be able to raise the temperature of the sensor element of the oxygen sensor by supplying part of the combustion gas generated in the combustion chamber to the oxygen sensor; prepared,
The supply passage supplies the oxygen sensor from the combustion chamber through the supply passage to the oxygen sensor as compared with the amount of decrease in the temperature of the combustion gas that decreases while reaching the oxygen sensor from the combustion chamber through the exhaust passage. It is configured so that the amount of decrease in the temperature of the combustion gas that decreases until the
The gas water heater, wherein the supply passage is disposed outside a heat exchange area where hot water is generated by heat exchange between combustion gas passing through the exhaust passage and water for hot water supply. The gas water heater according to any one of claims 1 to 6 , wherein the flow passage area of the supply passage is smaller than the flow passage area of the exhaust passage. a valve provided in the supply passage and capable of switching between an open state that allows passage of the combustion gas in the supply passage and a closed state that disallows passage of the combustion gas;
8. The gas water heater according to any one of claims 1 to 7 , further comprising a control section that controls opening and closing of the valve. an exhaust passage for discharging combustion gas generated in the combustion chamber from the combustion chamber;
an oxygen sensor disposed in the exhaust passage and detecting the oxygen concentration of the combustion gas;
a combustion control unit that controls the combustion state in the combustion chamber based on the oxygen concentration detected by the oxygen sensor;
with
A gas water heater that generates hot water by heat exchange between combustion gas passing through the exhaust passage and water for hot water supply,
a supply passage that is provided separately from the exhaust passage and configured to be able to raise the temperature of the sensor element of the oxygen sensor by supplying part of the combustion gas generated in the combustion chamber to the oxygen sensor; prepared,
The supply passage supplies the oxygen sensor from the combustion chamber through the supply passage to the oxygen sensor as compared with the amount of decrease in the temperature of the combustion gas that decreases while it reaches the oxygen sensor from the combustion chamber through the exhaust passage. It is configured so that the amount of decrease in the temperature of the combustion gas that decreases until the
a valve provided in the supply passage and capable of switching between an open state that allows passage of the combustion gas in the supply passage and a closed state that disallows passage of the combustion gas;
a control unit that controls opening and closing of the valve;
gas water heater. The oxygen sensor is provided with an electric heater for heating the sensor element,
The control unit places the valve in the open state and the heater in the non-energized state when boiling of water is started, and closes the valve on the basis that a predetermined switching condition is satisfied after the boiling of water is started. 10. The gas water heater according to claim 8 or 9, wherein the heater is switched to an energized state. The oxygen sensor is provided with an electric heater for heating the sensor element,
An acquisition unit that acquires by detecting or estimating the temperature of the sensor element when boiling water is started,
The control unit has a determination unit that determines whether the temperature of the sensor element has reached a predetermined temperature based on the acquisition result of the acquisition unit when boiling water is started, and the determination unit determines whether the temperature reaches the predetermined temperature. When it is determined that the temperature has not reached the predetermined temperature, the valve is set to the open state and the heater is not energized, and when it is determined that the predetermined temperature has been reached, the valve is set to the closed state and the heater is energized. 10. The gas water heater according to claim 8 or 9 , wherein 12. The gas water heater according to any one of claims 1 to 11 , wherein an outlet of said supply passage is connected to an intermediate position of said exhaust passage. 13. The gas water heater according to any one of claims 1 to 12 , wherein the outlet of the supply passage is connected to a portion of the exhaust passage that is located around a location where the sensor is arranged. The oxygen sensor has a cover portion that covers the sensor element from the exhaust passage side,
A through hole through which combustion gas can pass is formed in the cover,
14. The gas water heater according to claim 13 , wherein an outlet of said supply passage is arranged at a position separated from a position directly below said cover portion. 15. The gas water heater according to claim 14 , wherein the outlet of the supply passage is disposed upstream of the oxygen sensor in the flow direction of the combustion gas in the exhaust passage.

Images