JP7729600B2 - water heater - Google Patents

Description

The present invention relates to a water heater.

The water heater disclosed in Patent Document 1 includes a sensor burner and a control device. In this water heater, the sensor burner has a burner plate, a cylindrical portion, and a thermocouple. The burner plate is provided with a flame port from which a mixture of fuel gas and air is ejected. The cylindrical portion extends upward toward the side from which the mixture is ejected from the flame port. The thermocouple is positioned to penetrate the cylindrical portion, and its tip, located inside the cylindrical portion, detects the temperature of the flame inside the cylindrical portion. Based on the temperature detected by the thermocouple, the control device adjusts the mixture ratio and other controls to maintain complete combustion.

JP 2009-300040 A

In a water heater like the one disclosed in Patent Document 1, if the oxygen concentration in the air-fuel mixture supplied to the cylindrical portion of the sensor burner decreases, a state (lift state) occurs in which the flame rises upward (downstream). When this lift state occurs, the electromotive force generated by the thermocouple changes. When this type of water heater experiences such a change in electromotive force, it can prevent incomplete combustion by taking appropriate control (for example, by cutting off the air-fuel mixture).

However, with conventional sensor burners, including the sensor burner disclosed in Patent Document 1, when the oxygen concentration changes to decrease, the reaction of the flame rising upward can be slow or difficult, and in such cases it can take a long time to detect the decrease in oxygen concentration.

One objective of this disclosure is to provide technology that can more quickly detect a decrease in the oxygen concentration in the mixed gas supplied to a sensor burner in a water heater.

The water heater according to the present disclosure includes:
a combustion plate having flame holes through which a mixed gas of combustion gas and air is ejected;
a cylindrical portion provided downstream and above the combustion plate, through which the mixed gas ejected from the flame hole passes;
a thermocouple disposed in the cylindrical portion and configured to detect a temperature inside the cylindrical portion;
A water heater having a sensor burner that generates a flame above the flame hole,
the burner holes include a first burner hole group having a plurality of first burner holes and a second burner hole group having a plurality of second burner holes different from the first burner holes,
The flow velocity of the mixed gas ejected from the first burner hole is greater than the flow velocity of the mixed gas ejected from the second burner hole.

The water heater according to the present disclosure includes:
a combustion plate having flame holes through which a mixed gas of combustion gas and air is ejected;
a cylindrical portion provided downstream and above the combustion plate, through which the mixed gas ejected from the flame hole passes;
a thermocouple disposed in the cylindrical portion and configured to detect a temperature inside the cylindrical portion;
A water heater equipped with a sensor burner having
the burner holes include a first burner hole group having a plurality of first burner holes and a second burner hole group having a plurality of second burner holes different from the first burner holes,
The length from the inlet to the outlet of the first burner hole is shorter than the length from the inlet to the outlet of the second burner hole.

The technology disclosed herein can more quickly detect a decrease in the oxygen concentration in the mixed gas supplied to the sensor burner in the water heater.

FIG. 1 is a schematic diagram showing an overview of a water heater according to a first embodiment. FIG. 2 is a block diagram illustrating an example of the electrical configuration of the water heater. FIG. 3 is a perspective view of the combustion plate of the sensor burner. FIG. 4 is an explanatory diagram that schematically shows the sensor burner and the flame when the oxygen concentration in the mixed gas is sufficient. FIG. 5 is an explanatory diagram schematically showing the sensor burner and the flame when the flame from the first burner port is in a lifted state. FIG. 6 is a perspective view of a combustion plate of a sensor burner having a conventional configuration. FIG. 7 is an explanatory diagram schematically showing a sensor burner and a flame when the flame from the first burner port in a conventional sensor burner is in a lifted state.

Embodiments of the present disclosure are listed and exemplified below. Note that the features [1] to [6] exemplified below may be combined in any compatible combination.

[1] A combustion plate having flame holes through which a mixed gas of combustion gas and air is ejected;
a cylindrical portion provided downstream and above the combustion plate, through which the mixed gas ejected from the flame hole passes;
a thermocouple disposed in the cylindrical portion and configured to detect a temperature inside the cylindrical portion;
A water heater having a sensor burner that generates a flame above the flame hole,
the burner holes include a first burner hole group having a plurality of first burner holes and a second burner hole group having a plurality of second burner holes different from the first burner holes,
The flow velocity of the mixed gas ejected from the first flame hole is greater than the flow velocity of the mixed gas ejected from the second flame hole.

In the water heater described in [1], if the oxygen concentration in the mixed gas supplied to the sensor burner decreases, a state (lift state) in which the flame rises upward (downstream) can occur. The first and second flame holes are configured so that the flow rate of the mixed gas ejected from the first flame hole is greater than the flow rate of the mixed gas ejected from the second flame hole. Therefore, when the oxygen concentration in the mixed gas decreases and the flame changes to rise upward (downstream), the mixed gas flows more easily toward the first flame hole, making it easier for the first flame hole to respond more quickly. Therefore, when the oxygen concentration decreases significantly, a region where the lift state is promoted with good responsiveness is partially created, allowing the temperature detected by the thermocouple to change more quickly.

[2] The water heater described in [1], wherein the length from the inlet to the outlet of the first flame hole is shorter than the length from the inlet to the outlet of the second flame hole.

The water heater described in [2] utilizes a simple structure in which the length from the inlet to the outlet of the first flame hole is relatively short, making it possible to increase the flow rate of the mixed gas ejected from the first flame hole.

[3] a combustion plate having flame holes through which a mixed gas of combustion gas and air is ejected;
a cylindrical portion provided downstream and above the combustion plate, through which the mixed gas ejected from the flame hole passes;
a thermocouple disposed in the cylindrical portion and configured to detect a temperature inside the cylindrical portion;
A water heater equipped with a sensor burner having
the burner holes include a first burner hole group having a plurality of first burner holes and a second burner hole group having a plurality of second burner holes different from the first burner holes,
The water heater, wherein the length from the inlet to the outlet of the first burner hole is shorter than the length from the inlet to the outlet of the second burner hole.

In the water heater described in [3], when the oxygen concentration in the mixed gas supplied to the sensor burner decreases, a state (lift state) occurs in which the flame rises upward (downstream). Furthermore, because the length from the inlet to the outlet of the first burner hole is shorter than the length from the inlet to the outlet of the second burner hole, the flow rate at the first burner hole is increased compared to a configuration in which the length of the first burner hole is the same as the length of the second burner hole. Therefore, when the oxygen concentration in the mixed gas decreases and the flame changes to rise upward (downstream), the mixed gas is more likely to flow into the first burner hole, making it easier for the first burner hole to respond more quickly. Therefore, when the oxygen concentration changes to decrease significantly, a region in which the lift state is promoted with good responsiveness is partially created, allowing the temperature detected by the thermocouple to change more quickly.

[4] The upper surface portion of the combustion plate includes a first upper surface portion in which the outlets of the first burner hole group are provided and a second upper surface portion in which the outlets of the second burner hole group are provided,
The water heater according to any one of [1] to [3], wherein a step is formed in which the first upper surface portion is positioned lower than the second upper surface portion.

In the water heater described in [4], the first upper surface portion where the outlets of the first group of burner holes are located is located below the second upper surface portion where the outlets of the second group of burner holes are located, making it easier to prevent the flames from the first group of burner holes from continuing with the flames from the second group of burner holes. Therefore, in this water heater, if a change occurs that causes a decrease in the oxygen concentration in the mixed gas, the flame from the first group of burner holes is more likely to lift.

[5] The first upper surface portion is provided on the center side of the upper surface portion of the combustion plate,
the second upper surface portion is provided to surround the first upper surface portion of the upper surface portion of the combustion plate,
The water heater according to [4], wherein the step is configured in a ring shape.

In the water heater described in [5], the second upper surface portion surrounding the first upper surface portion is positioned higher than the first upper surface portion, making it easier to prevent the flames from the first group of flame holes from continuing with the flames from the second group of flame holes around the entire circumference of the first upper surface portion. Furthermore, this water heater can achieve the above effect with a simple configuration in which the center of the upper surface of the combustion plate is recessed.

[6] A water heater described in any one of [1] to [5], wherein the thermocouple overlaps with the first flame hole in the thickness direction of the combustion plate.

In the water heater described in [6], the thermocouple is positioned downstream and overlapping with the first flame hole, making it more susceptible to flame exposure from the first flame hole. Therefore, when a flame lift occurs due to a decrease in the oxygen concentration in the mixed gas supplied to the tubular section, a temperature change is likely to occur quickly in the thermocouple. Therefore, this water heater can more quickly detect a decrease in the oxygen concentration in the mixed gas.

First Embodiment
In the following, a water heater 1 and the like equipped with a sensor burner 10 of the first embodiment will be described.

1. Overview of Water Heater 1 The water heater 1 is a forced combustion type combustion device that supplies primary air for the air-fuel mixture using a blower. Specifically, as shown in FIG. 1, the water heater 1 includes a main burner 3, a heat exchanger 5, a flow rate control valve 7, a blower 8, a water volume control motor 9, a sensor burner 10, and a control device 13 (see FIG. 2). The main burner 3 heats water for hot water supply (hereinafter referred to as hot water supply water) by burning gas. The hot water heated by the main burner 3 flows through the heat exchanger 5. The flow rate control valve 7 is a proportional control type adjustment valve that controls the amount of gas supplied to the main burner 3. The blower 8 supplies air for the air-fuel mixture. The water volume control motor 9 is a motor that adjusts the amount of hot water flowing through the heat exchanger 5. The control device 13 controls the flow rate control valve 7, the blower 8, and the like.

As shown in FIG. 1, the water heater 1 further includes a first on-off valve 7A, a second on-off valve 7B, and a third on-off valve 7C. The first on-off valve 7A is a solenoid valve that opens and closes the supply port for gas supplied to the water heater 1. The second on-off valve 7B is a solenoid valve that opens and closes the gas passage connecting the flow rate adjustment valve 7 and the main burner 3. These on-off valves 7A, 7B, and 7C are controlled by the control device 13. Note that the arrangement and number of on-off valves illustrated here are merely examples. For example, two solenoid valves (the second on-off valve 7B and the third on-off valve 7C) are provided downstream of the first on-off valve 7A, but the number of solenoid valves is not limited to two.

The sensor burner 10 is a burner provided to detect the combustion state of the main burner 3. Combustion is carried out in the sensor burner 10 by supplying a mixed gas (gas and a portion of primary air). The mixture ratio of the mixed gas supplied to the sensor burner 10 is different from that of the mixed gas supplied to the main burner. The sensor burner 10 generates a flame above the flame holes 23, 24 described below. In this disclosure, the up-down direction corresponds to the axial direction of the axis A1 of the combustion plate 20 (see FIG. 3) and the axial direction of the axis of the cylindrical portion 30 described below. Most or all of the outer peripheral surface of the combustion plate 20 is a cylindrical surface centered on the axis A1. In this configuration, most or all of the outer peripheral surface of the cylindrical portion 30 is a cylindrical surface centered on a predetermined axis, and the direction of this axis is the up-down direction. Note that in this configuration, the extension direction of each flame hole 23, 24 is the up-down direction. When focusing on the combustion plate 20, the upper side of the combustion plate 20 is the side where the outlets 23B, 24B are provided in the vertical direction. The upper side of the combustion plate 20 corresponds to the downstream side of the mixed gas flow. The lower side of the combustion plate 20 is the side where the inlets 23A, 24A are provided in the vertical direction. The lower side of the combustion plate 20 corresponds to the upstream side of the mixed gas flow. In the tubular portion 30, the lower side is the side where the mixed gas is introduced into the tubular portion 30, and in the example of Figure 4, this is the side where the combustion plate 20 is arranged. In the tubular portion 30, the upper side is the side where the exhaust gas flows out after combustion from the tubular portion 30.

2. Configuration of the Control Device As described above, the control device 13 controls the flow rate adjustment valve 7, the on-off valves 7A, 7B, and 7C, the blower 8, etc. As shown in Fig. 2, this control device 13 receives as input a signal indicating the flame temperature output from the sensor burner 10 (the output of a thermocouple 40, described later), and is connected to an operation panel 13A that is set and operated by the user.

The control device 13 is configured with a well-known microcomputer consisting of a CPU, ROM, RAM, etc. This control device 13 controls the flow rate adjustment valve 7, etc. according to a program pre-stored in the ROM.

When the primary air supplied to the main burner 3 or the discharge of combustion gas is stagnated, the combustion state of the main burner 3 changes, and in conjunction with this, the combustion state of the sensor burner 10 transitions to an incomplete combustion state, causing a change in the signal (electromotive force) output from the thermocouple 40.

When the control device 13 detects an incomplete combustion state based on the signal output from the thermocouple 40, it controls the flow control valve 7 and the blower 8 so that the sensor burner 10 is in a complete combustion state. Furthermore, since the sensor burner 10 is set so that its combustion state changes more significantly than the main burner 3, by monitoring the combustion state of the sensor burner 10 and maintaining the combustion state of the sensor burner 10 in a complete combustion state, it is possible to prevent incomplete combustion in the main burner 3.

3. Structure of the Sensor Burner As shown in FIGS. 3 and 4, the sensor burner 10 has a combustion plate 20, a cylindrical portion 30, and a thermocouple 40.

As shown in Figure 3, the combustion plate 20 has a disk-shaped main body 21. The combustion plate 20 is made of a material with excellent fire resistance and heat insulation properties, such as ceramics. At least a portion of the combustion plate 20 is inserted into the cylindrical portion 30.

As shown in Figure 3, the main body 21 has a groove 22. The groove 22 is recessed from one surface of the main body 21 (the downstream surface when the combustion plate 20 is assembled to the tubular portion 30 (see Figure 4)) toward the other surface (the upstream surface). The groove 22 is provided in the center (part including the center) of the one surface (the downstream surface). The groove 22 has a circular shape in a plan view. The axis of the groove 22 coincides with, for example, the axis A1 of the main body 21.

As shown in Figures 3 and 4, the main body 21 is provided with a first flame hole group 23Z and a second flame hole group 24Z. The first flame hole group 23Z has a plurality of first flame holes (main flame holes) 23. The second flame hole group 24Z has a plurality of second flame holes (sleeve flame holes) 24 that are different from the first flame holes 23. The first flame holes 23 and the second flame holes 24 correspond to examples of "flame holes" in the present disclosure. The first flame holes 23 are holes that form relatively large flames and are flame holes for generating the main flame that contributes greatly to heating. The second flame holes 24 are holes that generate sleeve flames and stabilize the flame from the first flame holes 23. The diameter of the first flame holes 23 is the same as the diameter of the second flame holes 24. The first flame holes 23 and the second flame holes 24 penetrate the main body 21 in the plate thickness direction (vertical direction). The first burner holes 23 and the second burner holes 24 are linear and extend vertically. The inlets 23A of the first burner holes 23 and 24A of the second burner holes 24 are provided on the underside 21A of the main body 21. The inlets 23A of the first burner holes 23 and 24A of the second burner holes 24 open to a mixing tube (not shown) described below. The first burner holes 23 and the second burner holes 24 eject a mixed gas of combustion gas and air.

As shown in Figures 3 and 4, the first flame holes 23 are provided in the center of the upper surface portion 21B of the main body portion 21. The first flame holes 23 are provided in the first upper surface portion P1 of the upper surface portion 21B. The first upper surface portion P1 is the bottom surface portion of the groove portion 22 (the central portion of the upper surface portion 21B). The outlets 23B of the first flame holes 23 are provided in the first upper surface portion P1. The multiple first flame holes 23 are arranged, for example, in a multi-layered ring shape on the first upper surface portion P1, centered on the axis A1 of the main body portion 21.

As shown in Figures 3 and 4, the second flame holes 24 are provided on the outer edge side of the upper surface portion 21B of the combustion plate 20. The second flame holes 24 are provided on the second upper surface portion P2 of the upper surface portion 21B. The second upper surface portion P2 is provided on the upper surface portion 21B, surrounding the first upper surface portion P1. The outlets 24B of the second flame holes 24 are provided on the second upper surface portion P2. The multiple second flame holes 24 are arranged at equal intervals on the second upper surface portion P2 in the circumferential direction centered on the axis A1 of the main body portion 21.

A step 25 is formed where the first upper surface portion P1 is positioned lower than the second upper surface portion P2. The step 25 is formed in an annular shape centered on the axis A1 of the main body portion 21.

The length from the inlet 23A to the outlet 23B of the first burner hole 23 is shorter than the length from the inlet 24A to the outlet 24B of the second burner hole 24. The length from the inlet 23A to the outlet 23B of the first burner hole 23 is the distance between the lower surface portion 21A and the first upper surface portion P1 (L1 shown in FIG. 4). The length from the inlet 24A to the outlet 24B of the second burner hole 24 is the distance between the lower surface portion 21A and the second upper surface portion P2 (L2 shown in FIG. 4). The path of the mixed gas passing through the first burner hole 23 is shorter than the path of the mixed gas passing through the second burner hole 24. Also, as described above, the diameter of the first burner hole 23 is the same as the diameter of the second burner hole 24. Therefore, the flow velocity of the mixed gas ejected from the first burner hole 23 is greater than the flow velocity of the mixed gas ejected from the second burner hole 24.

The sensor burner 10 is provided with, for example, a mixing tube (not shown). The mixing tube supplies a mixture of combustion gas and air into the cylindrical portion 30 via the combustion plate 20. A mixing space is provided inside the mixing tube in which the combustion gas and air are mixed. The combustion gas and air are introduced into the mixing tube.

As shown in Figure 4, the tubular portion 30 is cylindrical. The tubular portion 30 is made of a metal material with excellent corrosion resistance, such as stainless steel. A portion of the tubular portion 30 (the upper end portion shown in Figure 4) is located downstream and above the combustion plate 20. A portion of the combustion plate 20 (the upper end portion shown in Figure 4) is inserted into the tubular portion 30. The axial direction of the tubular portion 30 is parallel to the axial direction of the axis A1 of the main body portion 21 of the combustion plate 20. The tubular portion 30 protects the flames generated from the first flame holes 23 and the second flame holes 24. The mixed gas ejected from the first flame holes 23 and the second flame holes 24 passes through the internal space of the tubular portion 30.

As shown in Figure 4, the thermocouple 40 is exposed inside the cylindrical portion 30. The thermocouple 40 detects the temperature inside the cylindrical portion 30. The thermocouple 40 penetrates the cylindrical portion 30 in its radial direction. The thermocouple 40 detects the temperature of the flame inside the cylindrical portion 30 at its tip located inside the cylindrical portion 30.

As shown in FIG. 4, the thermocouple 40 overlaps with the first flame hole 23 in the thickness direction of the combustion plate 20 (the direction along axis A1 shown in FIG. 3). Specifically, the tip of the thermocouple 40 overlaps with the first flame hole 23 from the downstream side when viewed in the axial direction of axis A1. Because the thermocouple 40 is positioned so as to overlap with the first flame hole 23, it is easily exposed to the flame from the first flame hole 23. This makes it easier to detect temperature changes within the tubular section 30 due to a decrease in oxygen concentration, allowing for earlier detection of a decrease in the oxygen concentration in the mixed gas supplied to the tubular section 30.

4. Combustion Control of Sensor Burner When combustion is performed in the sensor burner 10, as shown in Fig. 4, the mixed gas is ejected from the first flame hole 23, generating a flame from the first flame hole 23. Also, the mixed gas is ejected from the second flame hole 24, generating a flame from the second flame hole 24. The thermocouple 40 detects the temperature inside the cylindrical portion 30 (more specifically, the temperature of the flame from the first flame hole 23).

In the sensor burner 10, when the oxygen concentration in the mixed gas supplied to the tubular portion 30 decreases, a phenomenon occurs in which the flame from the first flame hole 23 lifts (floats up) downstream, as shown in Figure 5. Therefore, the sensor burner 10 of the present disclosure is configured so that the flow velocity of the mixed gas ejected from the first flame hole 23 is greater than the flow velocity of the mixed gas ejected from the second flame hole 24, thereby making it possible to speed up the lift (floats up) of the flame from the first flame hole 23 to the downstream side relative to the lift (floats up) of the flame from the second flame hole 24 to the downstream side.

The temperature detected by the thermocouple 40 changes depending on the flame lift. For example, in the pre-flame lift state shown in Figure 4, the thermocouple 40 is located close to the relatively high-temperature outer flame F1 and far from the relatively low-temperature inner flame F2. In contrast, when the oxygen concentration in the mixed gas supplied to the tubular portion 30 begins to decrease, a flame lift state as shown by the solid line in Figure 5 quickly occurs, and as this state is further accelerated, it quickly transitions to a further lift state as shown by the two-dot chain line in Figure 5. In the lift state shown in Figure 5, the thermocouple 40 is located far from the relatively high-temperature outer flame F1 and close to the relatively low-temperature inner flame F2. Therefore, the electromotive force generated in the thermocouple 40 decreases.

The sensor burner 10 is configured with the first and second flame holes 23 and 24 so that the flow rate of the mixed gas ejected from the first flame hole 23 is greater than the flow rate of the mixed gas ejected from the second flame hole 24. Therefore, when the oxygen concentration in the mixed gas decreases and the flame changes to lift upward (downstream), more mixed gas flows toward the first flame hole 23, making it easier for the first flame hole 23 to respond more quickly. In other words, the state shown in Figure 5 is likely to occur quickly. Therefore, when the oxygen concentration changes to decrease significantly, a region is created in which the lift state is promoted with good responsiveness, allowing the temperature detected by the thermocouple 40 to change more quickly.

For example, the control device 13 controls to cut off the supply of mixed gas when the amount of decrease in electromotive force detected by the thermocouple 40 reaches a preset amount of decrease in electromotive force. This makes it possible to prevent incomplete combustion in the main burner 3. The control device 13 may also control to cut off the supply of mixed gas when the value of electromotive force detected by the thermocouple 40 falls below a preset threshold. The control device 13 may also control to cut off the supply of mixed gas when the rate of decrease in electromotive force detected by the thermocouple 40 reaches a preset rate of decrease in electromotive force.

Figures 6 and 7 are diagrams illustrating the configuration of a conventional sensor burner 210. As shown in Figures 6 and 7, the conventional combustion plate 220 does not have a configuration equivalent to the groove portion 22 of the present disclosure. The length from the inlet to the outlet of the first burner hole 223 is the same as the length from the inlet to the outlet of the second burner hole 224. Therefore, the flow velocity of the mixed gas ejected from the first burner hole 223 is approximately the same as the flow velocity of the mixed gas ejected from the second burner hole 224. Therefore, when the flame changes to rise upward (downstream) in response to a decrease in the oxygen concentration in the mixed gas, the mixed gas does not easily flow toward the first burner hole 223, and the first burner hole 223 does not tend to react more quickly. In other words, there is little difference in the inflow velocity of the mixed gas between the first burner hole 223 and the second burner hole 224, and the flame lift is generally lifted with reduced local deviation, as shown by the dashed two-dot line in Figure 7. Therefore, when the oxygen concentration changes so that it drops significantly, it is not possible to create a region in which the lift state is promoted with the same responsiveness as in the sensor burner 10 of the present disclosure, and it is difficult to change the temperature detected by the thermocouple 40 more quickly.

In the sensor burner 10 of the present disclosure, the flow velocity of the mixed gas ejected from the second flame hole 24 is slower than the flow velocity of the mixed gas ejected from the first flame hole 23, making it easier for the flame from the first flame hole 23 to be stabilized by the flame from the second flame hole 24. Therefore, in cases such as when there is only a small decrease in the oxygen concentration in the mixed gas supplied to the tubular portion 30, changes in the electromotive force of the thermocouple 40 can be suppressed, preventing the supply of mixed gas from being inadvertently cut off.

The sensor burner 10 of the present disclosure has a step 25 formed by the first upper surface P1, where the outlet 23B of the first flame hole 23 is provided, and the second upper surface P2, where the outlet 24B of the second flame hole 24 is provided. This facilitates separation of the flame from the first flame hole 23 and the flame from the second flame hole 24. Therefore, when the oxygen concentration in the mixed gas begins to decrease, the flame from the first flame hole 23 can be quickly lifted (raised). On the other hand, when the decrease in oxygen concentration in the mixed gas is within an acceptable range (a degree of decrease that does not warrant detection), the flame away from the combustion plate 20 is stabilized by the flame from the second flame hole 24 downstream of the combustion plate 20, thereby preventing inadvertent detection of a decrease in oxygen concentration. Furthermore, in this way, the flame from the first flame hole 23, which is slightly distant from the combustion plate 20, is more susceptible to a decrease in oxygen concentration than when burning close to the combustion plate 20. Therefore, if the oxygen concentration drops further and falls outside the acceptable range, the flame can be quickly lifted, allowing the drop in oxygen concentration to be detected quickly.

5. Example of Effect In the water heater 1 of the present disclosure, a state in which the flame rises upward (downstream) (lift state) can occur when the oxygen concentration in the mixed gas supplied to the sensor burner 10 decreases. The first and second flame holes 23 and 24 are configured so that the flow velocity of the mixed gas ejected from the first flame hole 23 is greater than the flow velocity of the mixed gas ejected from the second flame hole 24. Therefore, when the oxygen concentration in the mixed gas decreases and the flame changes to rise upward (downstream), the mixed gas flows more easily toward the first flame hole 23, allowing the first flame hole 23 to respond more quickly. Therefore, when the oxygen concentration decreases significantly, a region in which the lift state is promoted with good responsiveness can be partially created, allowing the temperature detected by the thermocouple 40 to change more quickly.

The water heater 1 of the present disclosure can address the problem that "when different gas components are introduced, the likelihood of a lift state occurring varies for each gas component."
For example, in the field of water heaters, lift is more likely to occur when natural gas is used than propane gas. This is due to the fact that propane gas burns faster than natural gas, making lift less likely to occur. Furthermore, in a structure like that shown in Figure 7, the difference in the degree of lift between propane and natural gas is significantly apparent. Due to this, it becomes more difficult to detect the occurrence of lift when different gases are used in a water heater with the same structure. To address this issue, the water heater 1 of this configuration provides a step 25 in the flame port group as shown in Figure 3, thereby relatively increasing the flow velocity in the first flame port group 23Z and promoting lift in the central area. Therefore, the state shown in Figure 5 is likely to occur. Furthermore, in the state shown by the two-dot chain line in Figure 5, the flow velocity at the flame base of the flame section is smaller (slower) than the flow velocity in the first flame port group 23Z, making it easier to maintain the flame. Because this state is maintained, lift is more likely to occur, and even when propane-based gas is burned, the ease with which lift occurs is similar to when natural gas-based gas is burned.

In the water heater 1 of the present disclosure, the length from the inlet 23A to the outlet 23B of the first flame hole 23 is shorter than the length from the inlet 24A to the outlet 24B of the second flame hole 24. This makes it possible to increase the flow rate of the mixed gas ejected from the first flame hole 23 by utilizing a simple structure that makes the length from the inlet 23A to the outlet 23B of the first flame hole 23 relatively short.

In the water heater 1 of the present disclosure, the first upper surface portion P1, where the outlet 23B of the first flame hole 23 is provided, is located below the second upper surface portion P2, where the outlet 24B of the second flame hole 24 is provided, making it easier to separate the flame from the first flame hole 23 and the flame from the second flame hole 24. Therefore, when the oxygen concentration in the mixed gas tends to decrease, it becomes easier to lift the flame from the first flame hole 23.

In the water heater 1 of the present disclosure, the surface portion (second upper surface portion P2) provided on the outer periphery of the first upper surface portion P1 is located on the upper side, making it easier to separate the flame from the first flame hole 23 and the flame from the second flame hole 24 around the entire circumference of the first upper surface portion P1. Furthermore, the annular step 25 can be easily formed by a simple structure that recesses the central portion of the upper surface portion 21B of the combustion plate 20.

In the water heater 1 of the present disclosure, the thermocouple 40 is positioned downstream and overlapping with the first flame hole 23, making it more likely to be exposed to the flame from the first flame hole 23. This makes it easier to detect changes in temperature inside the tubular portion 30 due to a decrease in oxygen concentration, allowing for earlier detection of a decrease in the oxygen concentration in the mixed gas supplied to the tubular portion 30.

<Other Embodiments>
The present invention is not limited to the embodiments described above and in the drawings. For example, any combination of features of the above-described or following embodiments is possible within a range that does not contradict. Furthermore, any feature of the above-described or following embodiments may be omitted unless expressly stated as essential. Furthermore, the above-described embodiments may be modified as follows.

In the above-described embodiment, the step 25 is formed by the first upper surface portion P1 and the second upper surface portion P2. However, other configurations are possible as long as the first upper surface portion P1 is located upstream of the second upper surface portion P2. For example, the combustion plate 20 may have a cone-shaped recess (a curved shape that is convex upstream) instead of the groove portion 22, with first flame holes provided at the bottom of the recess (the upper surface portion corresponding to the first upper surface portion P1) and second flame holes provided at the outer peripheral upper surface portion of the recess (the upper surface portion corresponding to the second upper surface portion P2). Even with this configuration, the path length of the mixed gas ejected through the first flame holes is shorter than the path length of the mixed gas ejected through the second flame holes.

In the above embodiment, the diameter of the first flame hole 23 is the same as the diameter of the second flame hole 24, but they may be different.

In the above-described embodiment, the number of first flame holes 23 and the number of second flame holes 24 are not particularly limited. Furthermore, as long as the outlets 23B of the first flame holes 23 and the outlets 24B of the second flame holes 24 are provided on the first upper surface portion P1 and the second upper surface portion P2, respectively, there are no particular limitations on the arrangement, such as the way they are arranged.

In the above embodiment, a configuration was illustrated in which the thermocouple 40 overlaps with the first flame hole 23 in the thickness direction of the combustion plate 20 (the direction along the axis A1). However, the thermocouple 40 may also overlap with the first upper surface portion P1 without overlapping with the first flame hole 23.

The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is not limited to the embodiments disclosed herein, but is intended to include all modifications within the scope of the claims or within the scope equivalent to the claims.

1...water heater 3...main burner 5...heat exchanger 7...flow rate adjustment valve 7A...first on-off valve 7B...second on-off valve 7C...third on-off valve 8...blower 9...water volume control motor 10...sensor burner 13...control device 13A...operation panel 20...combustion plate 21...main body 21A...upper surface 21B...lower surface 22...groove 23...first flame hole (flame hole)
23A...Inlet 23B...Outlet 23Z...First flame hole group 24...Second flame hole (flame hole)
24A... inlet 24B... outlet 24Z... second burner hole group 25... step 26... first flow path 27... second flow path 30... cylindrical portion 40... thermocouple A1... axis F1... outer flame F2... inner flame P1... first upper surface portion P2... second upper surface portion

Claims (5)

a combustion plate having flame holes through which a mixed gas of combustion gas and air is ejected;
a cylindrical portion provided downstream and above the combustion plate, through which the mixed gas ejected from the flame hole passes;
a thermocouple disposed in the cylindrical portion and configured to detect a temperature inside the cylindrical portion;
A water heater having a sensor burner that generates a flame above the flame hole,
the burner holes include a first burner hole group having a plurality of first burner holes and a second burner hole group having a plurality of second burner holes different from the first burner holes,
a flow velocity of the mixed gas ejected from the first burner hole is greater than a flow velocity of the mixed gas ejected from the second burner hole;
the thermocouple overlaps with the first flame hole in a thickness direction of the combustion plate,
The length from the inlet to the outlet of the first burner port is shorter than the length from the inlet to the outlet of the second burner port.
Water heater. a combustion plate having flame holes through which a mixed gas of combustion gas and air is ejected;
a cylindrical portion provided downstream and above the combustion plate, through which the mixed gas ejected from the flame hole passes;
a thermocouple disposed in the cylindrical portion and configured to detect a temperature inside the cylindrical portion;
A water heater equipped with a sensor burner that generates a flame above the flame hole,
the burner holes include a first burner hole group having a plurality of first burner holes and a second burner hole group having a plurality of second burner holes different from the first burner holes,
a length from an inlet to an outlet of the first burner port is shorter than a length from an inlet to an outlet of the second burner port;
The thermocouple overlaps with the first flame hole in the thickness direction of the combustion plate.
Water heater. The upper surface portion of the combustion plate includes a first upper surface portion where the outlets of the first burner hole group are provided and a second upper surface portion where the outlets of the second burner hole group are provided, and a step is formed in which the first upper surface portion is located lower than the second upper surface portion.
The water heater according to claim 1 or 2 . a combustion plate having flame holes through which a mixed gas of combustion gas and air is ejected;
a cylindrical portion provided downstream and above the combustion plate, through which the mixed gas ejected from the flame hole passes;
a thermocouple disposed in the cylindrical portion and configured to detect a temperature inside the cylindrical portion;
A water heater having a sensor burner that generates a flame above the flame hole,
the burner holes include a first burner hole group having a plurality of first burner holes and a second burner hole group having a plurality of second burner holes different from the first burner holes,
a flow velocity of the mixed gas ejected from the first burner hole is greater than a flow velocity of the mixed gas ejected from the second burner hole;
the thermocouple overlaps with the first flame hole in a thickness direction of the combustion plate,
The upper surface portion of the combustion plate includes a first upper surface portion where the outlets of the first group of flame holes are provided, and a second upper surface portion where the outlets of the second group of flame holes are provided, and a step is formed in which the first upper surface portion is positioned lower than the second upper surface portion . the first upper surface portion is provided on a central side of the upper surface portion of the combustion plate,
the second upper surface portion is provided to surround the first upper surface portion of the upper surface portion of the combustion plate,
The step is configured in an annular shape.
The water heater according to claim 3 or claim 4 .