water heater

Abstract

To provide a technique capable of accelerating the detection of decreasing oxygen concentration in mixed gas being supplied to a sensor burner.SOLUTION: A water heater 1 comprises a sensor burner 10 having: a combustion plate 20 comprising first flame holes 23 and second flame holes 24 from which mixed gas including combustion gas and air is ejected, a cylindrical unit 30 disposed downstream of and above the combustion plate 20 to allow the mixed gas ejected from the first flame holes 23 and the second flame holes 24 to flow therethrough, and a thermocouple 40 disposed in the cylindrical unit 30 and detecting the temperature in the cylindrical unit 30. The flow velocity of the mixed gas ejected from the first flame holes 23 is greater than that of the mixed gas ejected from the second flame holes 24.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a water heater. [Background technology]

[0002] 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 from the flame port toward the side from which the mixture is ejected. The thermocouple is disposed 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 performs control such as adjusting the mixture ratio to maintain complete combustion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-300040 Summary of the Invention [Problem to be solved by the invention]

[0004] In a water heater such as that 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 in 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, cutting off the air-fuel mixture).

[0005] However, conventional sensor burners, including the sensor burner disclosed in Patent Document 1, may be slow or difficult to raise the flame upward when the oxygen concentration changes to decrease, and in such cases it takes time to detect the decrease in oxygen concentration.

[0006] An object of the present disclosure is to provide a technique that can more quickly detect a decrease in the oxygen concentration in a mixed gas supplied to a sensor burner in a water heater. [Means for solving the problem]

[0007] 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.

[0008] 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. [Effects of the Invention]

[0009] The technology according to the present disclosure can more quickly detect a decrease in the oxygen concentration in the mixed gas supplied to the sensor burner in the water heater. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing an overview of the water heater of the first embodiment. [Figure 2] FIG. 2 is a block diagram illustrating an example of the electrical configuration of the water heater. [Figure 3] FIG. 3 is a perspective view of the combustion plate of the sensor burner. [Figure 4] 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. [Figure 5] FIG. 5 is an explanatory diagram that schematically shows the sensor burner and the flame when the flame from the first burner port is in a lifted state. [Figure 6] FIG. 6 is a perspective view of a combustion plate of a sensor burner having a conventional configuration. [Figure 7] FIG. 7 is an explanatory diagram that schematically shows a sensor burner and a flame when the flame from the first burner port is lifted in a sensor burner of a conventional configuration. DETAILED DESCRIPTION OF THE INVENTION

[0011] The following describes exemplary embodiments of the present disclosure. Note that the following exemplary features [1] to [6] may be combined in any compatible combination.

[0012] [1] A combustion plate having a flame hole 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. Water heater.

[0013] In the water heater described in [1], when 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 burner holes are configured so that 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. Therefore, when the oxygen concentration in the mixed gas decreases and the flame tries to rise upward (downstream), the mixed gas flows more easily toward the first burner hole, making it easier for the first burner hole to respond. Therefore, when the oxygen concentration decreases significantly, a region where the lift state is promoted with good responsiveness can be partially created, allowing the temperature detected by the thermocouple to change more quickly.

[0014] [2] The water heater according to [1], 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.

[0015] The water heater described in [2] can increase the flow rate of the mixed gas ejected from the first flame hole by utilizing a simple structure in which the length from the inlet to the outlet of the first flame hole is relatively short.

[0016] [3] A combustion plate having a flame hole 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. Water heater.

[0017] 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 port is shorter than the length from the inlet to the outlet of the second burner port, the flow rate at the first burner port is increased compared to a configuration in which the length of the first burner port is the same as the length of the second burner port. 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 port, making the first burner port more likely to respond. 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.

[0018] [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, A step is formed in which the first upper surface portion is positioned lower than the second upper surface portion. A water heater according to any one of [1] to [3].

[0019] In the water heater described in [4], the first upper surface portion where the outlets of the first burner hole group are provided is located below the second upper surface portion where the outlets of the second burner hole group are provided, so it is easy to prevent the flames from the first burner hole group and the second burner hole group from continuing. Therefore, in this water heater, when a change occurs that reduces the oxygen concentration in the mixed gas, the flame from the first burner hole group is easy to lift.

[0020] [5] The first upper surface portion is provided on the 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. [4] The water heater described in [4].

[0021] 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, so that it is easy to prevent the flames from the first and second groups of flame holes from continuing around the entire circumference of the first upper surface portion. Moreover, this water heater can achieve the above effect with a simple configuration of "depressing the center of the upper surface of the combustion plate."

[0022] [6] The thermocouple overlaps with the first flame hole in the thickness direction of the combustion plate. A water heater according to any one of [1] to [5].

[0023] In the water heater described in [6], the thermocouple is located downstream of and overlaps 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 at the thermocouple. Therefore, this water heater can more quickly detect a decrease in the oxygen concentration in the mixed gas.

[0024] 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.

[0025] 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, etc.

[0026] 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 a 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.

[0027] The sensor burner 10 is a burner provided to detect the combustion state of the main burner 3. Mixed gas (gas and a portion of primary air) is supplied to the sensor burner 10, and combustion is performed. The mixture ratio of the mixed gas supplied to the sensor burner 10 is different from the mixture ratio 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 circumferential surface of the combustion plate 20 is a cylindrical surface centered on the axis A1. In this configuration, most or all of the outer circumferential 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. In this configuration, the extension direction of each of the flame holes 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 flow of the mixed gas. 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 flow of the mixed gas. In the cylindrical portion 30, the lower side is the side where the mixed gas is introduced into the cylindrical portion 30, and in the example of Figure 4, this is the side where the combustion plate 20 is arranged. In the cylindrical portion 30, the upper side is the side where the exhaust gas after combustion flows out of the cylindrical portion 30.

[0028] 2. Control device configuration 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, the control device 13 receives a signal indicating the flame temperature output from the sensor burner 10 (the output of a thermocouple 40, which will be described later), and is connected to an operation panel 13A that is set and operated by a user.

[0029] The control device 13 is configured by a well-known microcomputer including a CPU, a ROM, a RAM, etc. The control device 13 controls the flow rate adjustment valve 7 and the like in accordance with a program pre-stored in the ROM.

[0030] When the discharge of primary air and combustion gas supplied to the main burner 3 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 voltage) output from the thermocouple 40.

[0031] When the control device 13 detects an incomplete combustion state from 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. In addition, since the sensor burner 10 is set so that its combustion state changes more significantly than that of the main burner 3, it is possible to prevent incomplete combustion in 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.

[0032] 3. Structure of the sensor burner As shown in FIGS. 3 and 4, the sensor burner 10 includes a combustion plate 20, a cylindrical portion 30, and a thermocouple 40.

[0033] As shown in Figure 3, combustion plate 20 has a disk-shaped main body 21. Combustion plate 20 is made of a material with excellent fire resistance and heat insulation properties, such as ceramics. At least a portion of combustion plate 20 is inserted into tubular portion 30.

[0034] 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 (a portion 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 the axis A1 of the main body 21, for example.

[0035] As shown in FIGS. 3 and 4 , the main body 21 is provided with a first burner hole group 23Z and a second burner hole group 24Z. The first burner hole group 23Z has a plurality of first burner holes (main burner holes) 23. The second burner hole group 24Z has a plurality of second burner holes (sleeve burner holes) 24 that are different from the first burner holes 23. The first burner holes 23 and the second burner holes 24 correspond to an example of the “burner hole” in the present disclosure. The first burner holes 23 are holes that form a relatively large flame and are used to generate a main flame that contributes greatly to heating. The second burner holes 24 are holes that generate a sleeve flame and stabilize the flame from the first burner holes 23. The diameter of the first burner holes 23 is the same as the diameter of the second burner holes 24. The first burner holes 23 and the second burner 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 in the vertical direction. The inlets 23A of the first burner holes 23 and the inlets 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 the inlets 24A of the second burner holes 24 are open to a mixing tube (not shown) which will be described later. The first burner holes 23 and the second burner holes 24 eject a mixed gas which is a mixture of combustion gas and air.

[0036] As shown in Figures 3 and 4, first flame holes 23 are provided on the central side of upper surface portion 21B of main body portion 21. First flame holes 23 are provided on first upper surface portion P1 of upper surface portion 21B. First upper surface portion P1 is the bottom surface portion of groove portion 22 (the central portion of upper surface portion 21B). Outlets 23B of first flame holes 23 are provided on first upper surface portion P1. The multiple first flame holes 23 are arranged, for example, in the shape of a multi-layered ring centered on axis A1 of main body portion 21 on first upper surface portion P1.

[0037] 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 to surround 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.

[0038] The first upper surface portion P1 is positioned lower than the second upper surface portion P2 to define a step 25. The step 25 is provided in an annular shape with the axis A1 of the main body portion 21 as its center.

[0039] 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. Furthermore, 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.

[0040] The sensor burner 10 is provided with, for example, a mixing tube (not shown). The mixing tube supplies a mixed gas obtained by mixing combustion gas and air into the cylindrical portion 30 via the combustion plate 20. A mixing space in which the combustion gas and air are mixed is provided inside the mixing tube. The combustion gas and air are introduced into the mixing tube.

[0041] As shown in FIG. 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 FIG. 4) is provided downstream and above the combustion plate 20. A portion of the combustion plate 20 (the upper end portion shown in FIG. 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.

[0042] As shown in Fig. 4, the thermocouple 40 is provided so as to be 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 portion located inside the cylindrical portion 30.

[0043] 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 the 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 the 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 a change in temperature inside the tubular section 30 due to a decrease in oxygen concentration, and therefore makes it possible to more quickly detect a decrease in the oxygen concentration in the mixed gas supplied to the tubular section 30.

[0044] 4. Combustion control of sensor burner 4, when combustion is performed in the sensor burner 10, the mixed gas is ejected from the first flame hole 23, and a flame is generated from the first flame hole 23. The mixed gas is also ejected from the second flame hole 24, and a flame is generated 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).

[0045] In the sensor burner 10, when the oxygen concentration in the mixed gas supplied to the cylindrical portion 30 decreases, a phenomenon occurs in which the flame from the first burner hole 23 lifts (floats up) downstream, as shown in Fig. 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 burner hole 23 is greater than the flow velocity of the mixed gas ejected from the second burner hole 24, and the lift (floats up) of the flame from the first burner hole 23 to the downstream side can be made faster than the lift (floats up) of the flame from the second burner hole 24 to the downstream side.

[0046] The temperature detected by the thermocouple 40 changes depending on the flame lift. For example, in the state before the flame lift shown in FIG. 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 FIG. 5 occurs quickly, and as this state is further accelerated, it quickly transitions to a further lift state as shown by the two-dot chain line in FIG. 5. In the lift state shown in FIG. 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.

[0047] In the sensor burner 10, 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 lift upward (downstream), more mixed gas flows toward the first flame hole 23, making the first flame hole 23 more likely to respond. 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 in which the lift state is promoted with good responsiveness is partially created, and the temperature detected by the thermocouple 40 can be changed more quickly.

[0048] For example, the control device 13 performs control 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 perform 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 value. The control device 13 may also perform 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.

[0049] 6 and 7 are diagrams illustrating the configuration of a conventional sensor burner 210. As shown in FIGS. 6 and 7, the conventional combustion plate 220 does not have a configuration corresponding 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 side does not easily react more quickly. In other words, there is little difference in the inflow velocity of the mixed gas between the first burner hole 223 side and the second burner hole 224 side, and the flame lift is generally lifted with reduced local deviation, as shown by the two-dot chain line in FIG. 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 good 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.

[0050] In the sensor burner 10 of the present disclosure, the flow velocity of the mixed gas ejected from the second flame hole 24 is smaller than the flow velocity of the mixed gas ejected from the first flame hole 23, so the flame from the first flame hole 23 is easily stabilized by the flame from the second flame hole 24. Therefore, when the decrease in oxygen concentration in the mixed gas supplied to the cylindrical portion 30 is small, the change in the electromotive force of the thermocouple 40 can be suppressed, and the supply of the mixed gas can be prevented from being inadvertently cut off.

[0051] In the sensor burner 10 of the present disclosure, a step 25 is formed by the first upper surface portion P1 where the outlet 23B of the first burner hole 23 is provided and the second upper surface portion P2 where the outlet 24B of the second burner hole 24 is provided, making it easier to separate the flame from the first burner hole 23 and the flame from the second burner hole 24. Therefore, when the oxygen concentration in the mixed gas tends to decrease, the flame from the first burner hole 23 can be quickly lifted (raised up). On the other hand, when the decrease in oxygen concentration in the mixed gas is within an acceptable range (a degree of decrease where detection is not desired), the flame away from the combustion plate 20 is held by the flame from the second burner 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 burner hole 23 slightly away 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 further decreases and goes outside the allowable range, the flame can be quickly lifted, and the decrease in oxygen concentration can be quickly detected.

[0052] 5.Example of effects In the water heater 1 of the present disclosure, a state (lift state) in which the flame rises upward (downstream) 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, which allows the first flame hole 23 to react more quickly. Therefore, when the oxygen concentration decreases significantly, a region where the lift state is promoted with good responsiveness can be partially created, and the temperature detected by the thermocouple 40 can be changed more quickly.

[0053] The water heater 1 of the present disclosure can address the problem that "when different gas components are introduced, the likelihood of the lift state occurring varies depending on the 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 particularly pronounced. For this reason, 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 nozzle group as shown in Figure 3, which relatively increases the flow velocity in the first nozzle group 23Z and promotes 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 nozzle 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 likelihood of lift occurring is similar to that when natural gas-based gas is burned.

[0054] In the water heater 1 of the present disclosure, the length from inlet 23A to outlet 23B of first flame hole 23 is shorter than the length from inlet 24A to outlet 24B of second flame hole 24. This makes it possible to increase the flow rate of the mixed gas ejected from first flame hole 23 by utilizing a simple structure in which the length from inlet 23A to outlet 23B of first flame hole 23 is relatively short.

[0055] In the water heater 1 of the present disclosure, the first upper surface portion P1 where the outlets 23B of the first flame holes 23 are provided is located below the second upper surface portion P2 where the outlets 24B of the second flame holes 24 are provided, making it easier to separate the flames from the first flame holes 23 and the flames from the second flame holes 24. Therefore, when the oxygen concentration in the mixed gas tends to decrease, it becomes easier to lift the flame from the first flame holes 23.

[0056] 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, which makes it easier to separate the flame from the first flame hole 23 and the flame from the second flame hole 24 all around the first upper surface portion P1. Also, the annular step 25 can be easily formed by a simple structure in which the center portion of the upper surface portion 21B of the combustion plate 20 is recessed.

[0057] In the water heater 1 of the present disclosure, the thermocouple 40 is positioned downstream of and overlaps the first flame hole 23, and is therefore more likely to be exposed to the flame from the first flame hole 23. This makes it easier to detect a change in temperature inside the tubular portion 30 due to a decrease in oxygen concentration, and therefore makes it possible to detect a decrease in the oxygen concentration in the mixed gas supplied to the tubular portion 30 more quickly.

[0058] <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.

[0059] In the above-described embodiment, step 25 is formed by first upper surface portion P1 and second upper surface portion P2. However, other configurations are possible as long as first upper surface portion P1 is located upstream of second upper surface portion P2. For example, combustion plate 20 may have a cone-shaped recess (a curved shape that is convex toward the upstream side) instead of groove portion 22, with first flame holes provided at the bottom of the recess (the upper surface portion corresponding to 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 second upper surface portion P2). Even with such a 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.

[0060] In the above embodiment, the diameter of the first burner holes 23 is the same as the diameter of the second burner holes 24, but they may be different.

[0061] In the above-described embodiment, there is no particular limitation on the number of first burner holes 23 and the number of second burner holes 24. Furthermore, there is no particular limitation on the arrangement, such as the way in which outlets 23B of first burner holes 23 and outlets 24B of second burner holes 24 are arranged, as long as they are provided on first upper surface portion P1 and second upper surface portion P2, respectively.

[0062] In the above-described embodiment, a configuration is 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), but the thermocouple 40 may also be configured to overlap with the first upper surface portion P1 without overlapping with the first flame hole 23.

[0063] It should be noted that 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 indicated by the claims or the scope equivalent to the claims. [Explanation of symbols]

[0064] 1. Water heater 3...Main burner 5...Heat exchanger 7...Flow control valve 7A...First shut-off valve 7B...Second shut-off valve 7C...Third shut-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...Top part 21B…Bottom part 22...Groove 23...First flame hole (flame hole) 23A…Entrance 23B…Exit 23Z…1st flame hole group 24...2nd flame hole (flame hole) 24A…Entrance 24B…Exit 24Z…Second flame hole group 25...Step 26...First flow path 27...Second flow path 30...Cylindrical part 40...thermocouple A1...axis F1...external flame F2…Internal inflammation P1…First top part P2…Second top part

Claims

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, 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.

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 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.

3. 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 located lower than the second upper surface portion. The water heater according to claim 1 or 2.

4. 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 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. Water heater.

5. The first upper surface portion is provided on the 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.

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