TWI711791B - Gas stove - Google Patents

Abstract

The present invention provides a gas stove capable of detecting tempering with a small temperature increase using a temperature sensor and capable of suppressing false detection. A hood covering the mixing tube of the stove burner is installed, and the temperature inside the hood is measured with a temperature sensor. Periodically, the amount of increase in the measured temperature during a predetermined judgment period is acquired, and the amount of increase exceeds the flashback threshold to detect flashback. The tempering threshold is set according to the temperature inside the cover. In this way, by changing the tempering threshold, not only the tempering occurs when the temperature inside the cover is low and the measured temperature rise is large, but also the tempering occurs when the inside of the cover becomes hot. When the measured temperature rise is small, it is possible to detect flashback based on the amount of rise exceeding the flashback threshold. In addition, since the tempering threshold in a state where the temperature inside the cover is low can be set to be greater than the tempering threshold in a heated state, it is possible to suppress false detections.

Description

Gas stove

The present invention relates to a gas stove equipped with a temperature sensor for detecting abnormal combustion of fuel gas supplied to a stove burner.

Gas stoves that burn fuel gas in stove burners to heat cooking containers such as pots are becoming widespread. The stove burner includes a burner main body with a plurality of flares and a mixing tube extending from the burner main body. The fuel gas supplied through the gas passage is injected from the nozzle to the open end on the upstream side of the mixing pipe, and flows into the mixing pipe while sucking in primary air for combustion. Then, the mixed gas of the fuel gas and the primary air passing through the mixing tube is ejected from the flares. When ignited by the spark plug, the mixed gas starts to burn to form a flame outside the flares.

In such a stove burner, abnormal combustion of the supplied fuel gas may occur. For example, there is the following situation: when adjusting (weakening) the fire power of the stove burner, if the combustion speed is faster than the spraying speed of the mixed gas, the flame will sneak into the stove burner from the fire port, and the fuel gas injected from the nozzle will be mixed. The phenomenon of continued combustion in the tube (hereinafter referred to as flashback). In addition, there is a situation where the fuel gas leaks from the open end side of the mixing pipe when the flame port is blocked due to overflow of soup or the like from the cooking container, and flames are generated due to ignition of the leaked fuel gas The phenomenon of diffusion in the gas furnace (hereinafter referred to as reverse injection).

Therefore, in order to detect flashback and reverse injection, it is proposed to provide a thermocouple near the open end of the mixing tube in advance (Patent Document 1). When flashback or reverse injection occurs, the thermocouple is heated to generate electromotive force. Therefore, the gas shut-off valve that closes the gas passage using the electromotive force can stop abnormal combustion. In addition, there are cases where a temperature sensor is used instead of a thermocouple. The amount of temperature rise during a fixed period of time is monitored in advance, the occurrence of abnormal combustion is detected based on the amount of temperature rise exceeding a threshold value, and the gas shutoff valve that closes the gas passage is controlled.

【Prior Technical Literature】 【Patent Literature】

[Patent Document 1] JP 2003-28428 A

However, in a gas furnace that uses a temperature sensor to detect abnormal combustion of fuel gas as described above, when the fuel gas supply amount is set to be small (the heating power of the stove burner is small), it is difficult to detect flashback. Such a problem. This is due to the following reasons. First, even if tempering occurs inside the mixing tube, the amount of temperature rise measured by the temperature sensor provided outside the mixing tube is smaller than that of the reverse injection generated from the open end of the mixing tube. In addition, the tempering not only occurs when the temperature around the mixing tube is low shortly after the stove burner is ignited, but also when the periphery of the mixing tube heats up as the stove burner continues to burn. ,because Therefore, especially when tempering occurs in a heated state, the amount of temperature increase will be further reduced, making it difficult to detect the tempering.

The present invention has been completed in response to the above-mentioned problems in the conventional technology, and its object is to provide a gas stove that can detect a tempering with a small temperature increase using a temperature sensor and can suppress false detection.

In order to solve the above-mentioned problems, the gas stove of the present invention adopts the following structure. That is, a gas stove is equipped with a stove burner including a burner body having a plurality of burners and a mixing tube extending from the burner body. When fuel gas supplied through a gas passage is injected from the nozzle to the mixing At the open end of the pipe, the mixed gas of the fuel gas and the primary air flowing in from the open end is ejected from the burner through the mixing pipe. The gas furnace is characterized in that the gas furnace includes a cover that covers the mixing pipe and opens the opening The end is housed inside; a temperature sensor, which is installed on the cover, can measure the temperature inside the cover; a judgment unit, which periodically obtains the increase in the temperature measured by the temperature sensor during a predetermined judgment period , And determine whether the amount of increase exceeds the prescribed tempering threshold; the gas cut-off unit, when the judging unit determines that the amount of rise exceeds the tempering threshold, the gas cut-off unit cuts off the supply of the fuel gas ; And a judgment criterion setting unit, which sets the tempering threshold according to the temperature inside the cover.

In such a gas furnace of the present invention, by changing the tempering threshold according to the temperature inside the hood, it is not only possible to cause the tempering in the state where the temperature inside the hood is low, such as shortly after ignition of the stove burner, etc. When the temperature rise is large when measuring the fire, it can be based on the rise When the tempering threshold is exceeded and tempering is detected, and the inner side of the hood becomes hot as the stove burner continues to burn and tempering occurs, and the measured temperature rise is small, the rise can also be exceeded. The flashback threshold is detected to detect flashback.

In addition, since the tempering threshold in a state where the temperature inside the cover is low can be set to be greater than the tempering threshold in a state where the inside of the cover is heated, it is possible to suppress the increase in the measured temperature even though tempering does not occur. If the tempering threshold is exceeded, it is judged that a false detection such as tempering has occurred.

In the gas furnace of the present invention described above, not only the tempering threshold value is set based on the temperature inside the cover, but the judgment period may be further set based on the temperature inside the cover.

When tempering occurs in a state where the temperature inside the cover is low, the measured temperature rises significantly with the tempering, and it takes time to accurately grasp the amount of increase. In contrast, when the temperature inside the cover changes When tempering occurs in a hot state, the measured temperature will immediately converge and become saturated with the increase in the tempering. Therefore, by changing the judgment period according to the temperature inside the cover, in a state where the temperature inside the cover is low, it is possible to ensure a judgment period sufficient to accurately grasp the amount of increase in the measured temperature with tempering. The difference between the rising amount during normal combustion of the tempering and the rising amount when the tempering occurs becomes larger, and false detection can be suppressed. In addition, in a state where the inside of the cover becomes hot, the occurrence of flashback can be quickly detected by shortening the determination period.

In addition, any one of the mixing tube and the cover of the gas furnace of the present invention may be provided with a heat transfer part that transmits heat from the mixing tube to the cover by contacting any other of the mixing tube and the cover. .

In this way, when the mixing tube is heated due to tempering, the heat will be transferred to the cover via the heat transfer part. Therefore, compared with the case where the heat transfer part is not provided, it can be The generated heat is quickly reflected on the temperature inside the cover (the temperature measured by the temperature sensor). As a result, the use of the temperature sensor attached to the cover can not only improve the detection accuracy of reverse injection, but also the detection accuracy of backfire.

In addition, in the gas furnace of the present invention described above, a material having a thermal conductivity greater than that of the mixing pipe may be used to form the cover.

In this way, compared with the case where the cover is made of the same material as the mixing tube, the thermal conductivity is improved, and the heat generated by the tempering is easily reflected on the temperature inside the cover. Therefore, it is easy to measure by the temperature sensor The amount of temperature rise is used to detect flashback.

By means of the above technical means, the present invention provides a gas furnace that can use a temperature sensor to detect backfire with a small temperature increase and can suppress false detections, thereby controlling the gas shutoff valve that closes the gas passage.

1‧‧‧Gas stove

2‧‧‧Stove main body

3‧‧‧Top plate

4‧‧‧Stove burner

5‧‧‧Fire Support

6‧‧‧Operation knob

10‧‧‧Burner body

11‧‧‧Main burner section

12‧‧‧Auxiliary burner department

13‧‧‧Furnace body

14‧‧‧Main burner head

15‧‧‧Sub burner head

16‧‧‧Main burner burner

17‧‧‧Sub-Burner Flare

18‧‧‧Main burner mixing tube

19‧‧‧Auxiliary burner mixing tube

20‧‧‧Air conditioning device

21‧‧‧Air conditioning device

22‧‧‧Air inlet

23‧‧‧Air inlet

24‧‧‧Placement Department

25‧‧‧Placement Department

26‧‧‧Main burner gas piping

27‧‧‧Sub-burner gas piping

27a‧‧‧Nozzle

30‧‧‧Cover

31‧‧‧Fixed screw

32‧‧‧Temperature sensor

40‧‧‧Gas source piping

41‧‧‧Gas shut-off valve

42‧‧‧Flow control valve

50‧‧‧Control Department

Fig. 1 is a perspective view showing the appearance of the gas stove 1 of the present embodiment.

Fig. 2 is a perspective view showing the stove burner 4 mounted on the gas stove 1.

Fig. 3 is a perspective view showing the cover 30 of this embodiment.

Fig. 4 is an explanatory diagram showing an example of abnormal combustion of fuel gas generated in the stove burner 4.

[Figure 5] It shows the detection of the production in the mixing pipe 19 of the sub-combustor based on the increase in temperature in the hood. Illustration of an example of raw tempering.

Fig. 6 is a flowchart of the flashback detection process executed by the control unit 50 of the present embodiment.

Fig. 7 is a flowchart of the judgment criterion setting process executed in the flashback detection process.

Fig. 8 is an explanatory diagram showing an example of detecting whether or not flashback occurs in the sub-combustor mixing pipe 19 in the gas furnace 1 of the present embodiment according to the flashback detection processing.

Fig. 9 is an explanatory diagram showing an example of detecting whether or not flashback occurs in the sub-combustor mixing pipe 19 in the gas furnace 1 of the first modification.

[Fig. 10] is an explanatory diagram for changing the judgment period and comparing the temperature increase ΔT of the temperature in the cover.

Fig. 11 is a flowchart of the determination criterion setting process executed by the control unit 50 of the second modification.

Fig. 1 is a perspective view showing the appearance of a gas stove 1 of the present embodiment. The gas stove 1 of this embodiment includes: a stove main body 2, which is formed in a thin box shape with an open upper surface side; a top plate 3, which is placed on the stove main body 2 and covers the upper surface of the stove main body 2; Stove burners 4R, 4L are arranged in such a way that their upper parts protrude from the through holes formed in the top plate 3; and fire stays 5R, 5L are arranged on the upper surface of the top plate 3 to surround the stove burners 4R, 4L. Used to place cooking containers such as pots.

In addition, the top plate 3 is provided with operating knobs 6R and 6L corresponding to the stove burners 4R and 4L, respectively, and the operating knobs 6R and 6L are used to be operated by the user during ignition, heating power adjustment, and the like. When the operation knobs 6R, 6L are pushed down and rotated in a predetermined direction (counterclockwise in this embodiment), fuel gas is supplied to the stove burners 4R, 4L, and the unillustrated The spark plug ignites. After that, when the rotation angle of the operation knobs 6R, 6L is changed, the supply amount of fuel gas is changed, so that the heating power of the stove burners 4R, 4L can be adjusted. In addition, the right side stove burner 4R and the left side stove burner 4L have basically the same structure and shape. Therefore, if there is no need to distinguish between the right side and the left side, only the stove burner 4 will be described below. .

FIG. 2 is a perspective view showing the stove burner 4 mounted on the gas stove 1. The stove burner 4 of the present embodiment as shown in the figure is a so-called main and auxiliary burner having a dual structure including a main burner portion 11 in the shape of a ring and a sub-burner portion 12 arranged inside the main burner portion 11. The burner body 10 constituting the main burner portion 11 and the sub burner portion 12 includes a furnace body 13, a ring-shaped main burner head 14 and a circular auxiliary burner head 15, etc., wherein the furnace body 13 is formed There are a ring-shaped main burner mixing chamber and a sub-burner mixing chamber not shown. The main burner head 14 covers the upper opening of the main burner mixing chamber and is placed on the furnace body 13, and the sub-burner head 15 The upper opening of the mixing chamber of the sub-burner is covered and placed on the furnace body 13.

On the lower surface of the outer peripheral wall of the main burner head 14 (the surface mounted on the furnace body 13), a plurality of grooves (flame grooves) are radially formed with respect to the center of the main burner head 14. When the main burner head 14 is placed on the furnace body 13, a plurality of main burner flares 16 communicating with the main burner mixing chamber are formed by the plurality of burner grooves and the upper surface of the furnace body 13. Similarly, on the lower surface of the outer peripheral wall of the auxiliary burner head 15, a plurality of burner grooves are radially formed with respect to the center of the auxiliary burner head 15. When the auxiliary burner head 15 is placed in the furnace In the case of the body 13, a plurality of sub-burner flares 17 communicating with the sub-burner mixing chamber are formed by a plurality of burner slots and the upper surface of the furnace body 13.

In addition, a main burner mixing pipe 18 communicating with the main burner mixing chamber and an auxiliary burner mixing pipe 19 communicating with the auxiliary burner mixing chamber are extended from the furnace body 13. The main burner mixing pipe 18 and the auxiliary burner mixing pipe 19 of this embodiment are integrated with the furnace body 13 by casting using iron. Body formation. An air conditioning device 20 is provided at the opening end of the main burner mixing pipe 18 on the side opposite to the furnace body 13 to adjust the opening degree of the air inlet 22. When the fuel gas supplied through the main combustor gas pipe 26 is injected to the open end of the main combustor mixing pipe 18, it flows into the main combustor mixing pipe 18 while drawing in primary air for combustion from the air inflow port 22. Furthermore, since the mixed gas of the fuel gas and the primary air passing through the main burner mixing pipe 18 is supplied to the main burner mixing chamber and ejected from the main burner port 16, when a spark is emitted from a spark plug not shown, mixing starts The combustion of the gas forms a flame on the outside of the main burner port 16.

Similarly, an air conditioning device 21 is provided at the opening end of the sub-combustor mixing pipe 19 on the side opposite to the furnace body 13 so that the opening degree of the air inflow port 23 can be adjusted. In addition, the auxiliary burner mixing pipe 19 is shorter than the main burner mixing pipe 18, and the open end of the auxiliary burner mixing pipe 19 is located closer to the furnace body 13 than the open end of the main burner mixing pipe 18. When the fuel gas supplied through the sub-burner gas piping 27 is injected to the open end of the sub-burner mixing pipe 19, it flows into the sub-burner mixing pipe 19 together with the primary air drawn in from the air inlet 23, and is mixed by the sub-burner The mixed gas in the pipe 19 passes through the auxiliary burner mixing chamber and is ejected from the auxiliary burner burner 17. The main burner head 14 of the present embodiment is formed with a slit for prolonged firing, which is not shown. The prolonged firing from the side of the main burner part 11 to the side of the sub-burner part 12 is formed through the slit for prolonged firing. The portion 12 starts the combustion of the mixed gas to form a flame on the outside of the sub-combustor burner 17.

In addition, the gas furnace 1 of the present embodiment is provided with a cover 30 covering the main burner mixing pipe 18 and the sub burner mixing pipe 19. FIG. 3 is a perspective view showing the cover 30 of this embodiment. First, FIG. 3(a) shows the cover 30 in a state before mounting. The cover 30 is formed by bending the left and right ends of the substantially rectangular upper surface portion of the aluminum flat plate downward by sheet metal processing using an aluminum flat plate to form the left and right sides, and the front and rear ends of the substantially rectangular upper surface portion of the aluminum flat plate are formed. Also bend down Folded to form a box shape surrounding the surroundings.

On the other hand, the mounting portions 24, 25 on which the cover 30 is mounted are respectively provided on the main combustor mixing pipe 18 and the sub-combustor mixing pipe 19 of this embodiment so as to protrude upward, and the mounting portions 24, 25 The upper end is formed flat. In a state where the cover 30 is placed on the placing portion 24 of the main combustor mixing pipe 18 and the placing portion 25 of the sub-combustor mixing pipe 19, the upper surface of the cover 30 is fixed by fastening screws 31. In addition, the mounting parts 24 and 25 of this embodiment correspond to the "heat transfer part" of the present invention.

Fig. 3(b) shows the state after the cover 30 is attached. In addition, in the figure, in order to be able to see the main combustor mixing pipe 18 and the sub-combustor mixing pipe 19, the cover 30 is shown with a broken line through the cover 30. As shown in the figure, both the open end of the main combustor mixing pipe 18 and the open end of the sub-combustor mixing pipe 19 are arranged inside the cover 30. In addition, a temperature sensor 32 for measuring the temperature inside the cover 30 is mounted, and the temperature sensor 32 of this embodiment uses a thermistor whose resistance changes in accordance with a change in temperature. In the example shown in the figure, the tip of the temperature sensor 32 penetrates the side surface of the cover 30 near the sub-burner mixing pipe 19, and the tip is close to the outside of the opening end of the sub-burner mixing pipe 19.

In the stove burner 4 described above, abnormal combustion of the supplied fuel gas may occur. FIG. 4 is an explanatory diagram showing an example of abnormal combustion of the fuel gas generated in the stove burner 4. In the figure, a cross section obtained by cutting the sub-combustor mixing pipe 19 with a horizontal plane is shown. In addition, the cross section of the main combustor mixing pipe 18 is omitted from the drawing, but its basic structure is the same as that of the sub combustor mixing pipe 19. As described above, the fuel gas is supplied to the sub-combustor mixing pipe 19 through the sub-combustor gas pipe 27. The sub-combustor gas pipe 27 and the main combustor gas pipe 26 are branched from one gas source pipe 40 on the upstream side.

The gas source piping 40 is provided with a gas for opening and closing the gas source piping 40 The body shut-off valve 41 and the flow rate adjustment valve 42 for adjusting the flow rate of the fuel gas passing through the gas source piping 40. The gas shutoff valve 41 is electrically connected to the control unit 50 and is controlled to open and close by the control unit 50. The flow control valve 42 is connected to the operation knob 6 on the top plate 3 via a shaft (not shown), and adjusts the flow rate of the fuel gas according to the rotation of the operation knob 6 to change the heating power of the stove burner 4. In addition, in this embodiment, the main burner gas pipe 26, the sub-burner gas pipe 27, and the gas source pipe 40 correspond to the "gas passage" of the present invention.

When the gas shutoff valve 41 and the flow control valve 42 are opened to supply fuel gas to the sub-burner gas pipe 27, the fuel gas is injected from the nozzle 27a at the tip of the sub-burner gas pipe 27 to the open end of the sub-burner mixing pipe 19 , And mixed with the primary air flowing in from the air inlet 23 while passing through the sub-combustor mixing pipe 19. In addition, by igniting the mixed gas ejected from the sub-combustor flares 17 via the sub-combustor mixing chamber, the combustion that forms a flame outside the sub-combustor flares 17 is normal combustion. Also, similarly, the fuel gas supplied to the main combustor gas pipe 26 is injected to the open end of the main combustor mixing pipe 18, but the supply amount of the fuel gas supplied to the main combustor mixing pipe 18 is set to be greater than The supply amount of the fuel gas supplied from the sub-combustor mixing pipe 19.

In contrast to this, there is a case where the auxiliary burner port 17 is blocked due to overflow of soup or the like from the cooking container placed on the flame holder 5, and the mixed gas cannot be ejected from the auxiliary burner port 17, so The fuel gas injected from the nozzle 27a of the sub-combustor gas piping 27 leaks from the air inlet 23. When the leaked fuel gas is ignited, as shown in FIG. 4(a), it is ejected from the air inlet 23. Flame phenomenon (hereinafter referred to as reverse spray). In addition, the reverse injection is not only generated at the air inlet 23 of the sub-combustor mixing pipe 19, but may also be generated at the air inlet 22 of the main burner mixing pipe 18 when the main burner 16 is blocked. As above, The open end of the main burner mixing pipe 18 and the open end of the sub-burner mixing pipe 19 are both arranged inside the cover 30, and the heat of the flame diffused by the occurrence of the reverse injection is stuffed inside the cover 30. Therefore, the temperature sensor 32 is heated sharply. The control unit 50 is electrically connected to the temperature sensor 32, and can detect the occurrence of the reverse injection based on the temperature measured by the temperature sensor 32. In addition, the control unit 50 closes the gas shutoff valve 41 to forcibly extinguish the flame when it detects that the reverse injection occurs.

In addition, there is a case in which the spray speed of the mixed gas is lower than the combustion speed when the heating power of the stove burner 4 is adjusted, and the auxiliary burner head 15 is placed obliquely with respect to the furnace body 13, and the flame passes from the auxiliary burner burner. 17 submerged into the furnace burner 4, as shown in FIG. 4(b), a phenomenon in which the fuel gas injected from the nozzle 27a of the sub-burner gas pipe 27 burns in the sub-burner mixing pipe 19 (hereinafter referred to as the return fire). In particular, in a fuel gas that burns at a faster rate like a gas with a large amount of hydrogen, flashback is likely to occur. In addition, the flashback is not limited to being generated in the sub-combustor mixing pipe 19, and may be similarly generated in the main combustor mixing pipe 18. In addition, once flashback occurs, combustion is maintained until the supply of fuel gas is stopped, and the main burner mixing pipe 18 and the sub-burner mixing pipe 19 are heated, thus covering the main burner mixing pipe 18 and the sub-burner mixing pipe 19 The temperature inside the cover 30 (hereinafter referred to as the temperature in the cover) rises. The control unit 50 closes the gas shut-off valve 41 to forcibly extinguish the flame when it detects the occurrence of flashback based on the increase in the measured temperature of the temperature sensor 32 as described later.

As described above, in the gas furnace 1 of the present embodiment, the main burner mixing pipe 18 is provided with the placing portion 24, the sub-burner mixing pipe is provided with the placing portion 25, and the cover 30 is placed (in contact with ) It is fixed in the state of the placing parts 24 and 25. Therefore, when the main burner mixing pipe 18 and the sub-burner mixing pipe 19 are heated due to the occurrence of backfire, the heat is transferred to the cover 30 via the mounting parts 24 and 25. As a result, compared with the case where the mounting portions 24 and 25 are not provided, the heat generation due to tempering can be made faster. The temperature in the cover (the temperature measured by the temperature sensor 32) is quickly reflected, and the temperature sensor 32 mounted on the cover 30 can detect not only the occurrence of back-spraying but also the occurrence of backfire. In particular, for the sub-burner mixing pipe 19, the fuel gas supply amount is smaller than that of the main burner mixing pipe 18. Therefore, the amount of heat generated during tempering is also small, and there is a tendency that it is difficult to detect the occurrence of tempering. However, by contacting the mounting portion 25 with the cover 30 and transferring heat to the cover 30, the temperature rise measured by the temperature sensor 32 can be increased, and therefore, the occurrence of return in the sub-combustor mixing pipe 19 can be detected fire.

In addition, the cover 30 of this embodiment is formed of an aluminum flat plate (thermal conductivity: 236W/(m.K)), and iron (thermal conductivity: 84W/(m.K)) is used in the same way as the auxiliary burner mixing pipe 19 and the main burner mixing pipe 18. (m.K)) Compared with the case where the cover 30 is formed, the thermal conductivity can be improved. Therefore, it is easy to detect the flashback based on the temperature increase measured by the temperature sensor 32.

In addition, in the gas furnace 1 of the present embodiment, the main burner mixing pipe 18 and the sub-combustor mixing pipe 19 are provided with mounting portions 24, 25 and the mounting portions 24, 25 are in contact with the cover 30, but it may be Yes, in contrast to this, contact portions protruding toward the main combustor mixing pipe 18 and the sub-combustor mixing pipe 19 are provided in advance on the cover 30 side so that the contact portions are in contact with the main combustor mixing pipe 18 and the sub-combustor The state of the mixing tube 19 fixes the cover 30 in advance.

In addition, in the gas furnace 1 of the present embodiment, one temperature sensor 32 is used to detect the reverse injection and backfire of the main burner mixing pipe 18 and the sub-burner mixing pipe 19, but multiple Temperature sensor 32. For example, the temperature sensor 32 installed on the side of the main burner mixing pipe 18 side of the hood 30 may be used to detect the reverse injection and backfire at the main burner mixing pipe 18, and the temperature sensor 32 installed on the hood 30 may be used. The temperature sensor 32 on the side surface of the auxiliary burner mixing pipe 19 detects the reverse injection and backfire at the auxiliary burner mixing pipe 19. On the other hand, in this embodiment, one temperature When the sensor 32 detects both the main burner mixing pipe 18 and the sub-burner mixing pipe 19, the temperature sensor 32 is installed in advance on the side of the cover 30 on the side of the sub-burner mixing pipe 19 , It is easy to detect the backfire at the sub-combustor mixing pipe 19, which generates less calorific value during tempering than the main combustor mixing pipe 18.

FIG. 5 is an explanatory diagram showing an example of detecting the flashback generated in the sub-combustor mixing pipe 19 based on the amount of increase in the temperature in the hood. In the graph of Fig. 5, the time is taken as the horizontal axis and the temperature is taken as the vertical axis. The single-dot chain line represents the change in temperature in the hood when the stove burner 4 is burning normally, and the solid line represents The temperature change in the cover when the sub-combustor mixing pipe 19 is backfired. In addition, the temperature inside the cover is the temperature measured by the temperature sensor 32.

First, Fig. 5(a) shows an example in which tempering occurs in a state where the temperature inside the cover 30 is low (for example, 25° C.) shortly after the stove burner 4 is ignited. In a state where the temperature inside the hood 30 is low, when the stove burner 4 is burning normally, the temperature in the hood also gradually rises due to the radiant heat from the stove burner 4. In contrast, when the sub-combustor mixing pipe 19 is backfired, the sub-combustor mixing pipe 19 is heated, and the temperature of the inside of the cover 30 covering the sub-combustor mixing pipe 19 rises significantly from that during normal combustion. . Therefore, the temperature increase ΔT of the temperature in the hood for a fixed period of time Δt (for example, 5 minutes) can be obtained, and the temperature increase ΔT can exceed the predetermined tempering threshold (larger than the temperature increase during normal combustion). Value) and it is detected that backfire occurs in the mixing pipe 19 of the sub-combustor.

In addition, in (a) of FIG. 5, for comparison, the change in the temperature in the hood when the main combustor mixing pipe 18 is backfired is indicated by a broken line. As described above, in the main burner mixing pipe 18 that has more fuel gas supply than the auxiliary burner mixing pipe 19, the amount of heat generated during tempering is large, and the temperature rise in the hood is also large. Compared with the mixer tube 19, it is easier to inspect Measured backfire.

On the other hand, in (b) of FIG. 5, there is shown an example in which tempering occurs in a state (for example, 80° C.) in which the inside of the hood 30 heats up as the stove burner 4 continues to burn. Compared with the state where the temperature inside the cover 30 of FIG. 5(a) is low, in the state where the inside of the cover 30 is hot, even if the secondary burner mixing pipe 19 is backfired, the temperature in the cover is constant. During the period Δt, the temperature increase ΔT is also small. Therefore, the amount of temperature increase ΔT does not exceed the tempering threshold value, and it is difficult to detect the tempering at the sub-combustor mixing pipe 19. Nevertheless, if the tempering threshold is lowered in advance, the following situation will occur: in a state where the temperature inside the cover 30 is low, although tempering does not occur, it is likely to be erroneously detected due to the temperature increase ΔT exceeding the tempering threshold Out of tempering. In addition, in FIG. 5(b), the illustration of the case where backfire occurs in the main combustor mixing pipe 18 is omitted, but the temperature in the cover increases with the tempering of the sub combustor mixing pipe 19 because of the increase in temperature ΔT is smaller than the amount of temperature increase ΔT in which the temperature in the hood rises with the tempering of the main burner mixing pipe 18, so it is difficult to detect the tempering.

Therefore, in the gas furnace 1 of this embodiment, the control unit 50 executes the following flashback detection processing, thereby not only detecting that the temperature inside the cover 30 is low in the sub-combustor mixing pipe 19 The flashback can also detect the flashback generated in the sub-burner mixing pipe 19 in a state where the inside of the cover 30 is heated.

FIG. 6 is a flowchart of the flashback detection process executed by the control unit 50 of this embodiment. The user of the gas stove 1 operates the operation knob 6 to ignite the stove burner 4, thereby starting the flashback detection process. In the flashback detection process, first, the temperature sensor 32 measures the temperature in the hood when the furnace burner 4 is ignited (step 100). Then, a process (hereinafter referred to as a judgment criterion setting process) of setting the judgment criterion of the tempering according to the measured temperature in the cover is executed.

Figure 7 is the flow of the judgment criterion setting process executed in the flashback detection process Figure. In the determination criterion setting process, first, it is determined whether the temperature in the cover measured by the temperature sensor 32 is less than 80°C (step 130). Then, when the temperature in the cover is less than 80°C (step 130: YES), the tempering threshold is set to the first threshold (23°C in this embodiment) (step 132).

On the other hand, when the temperature in the cover is 80°C or higher (step 130: No), it is next judged whether the temperature in the cover is lower than 110°C (step 134). Then, when the temperature in the cover is 80°C or more and less than 110°C (step 134: Yes), the tempering threshold is set to a second threshold (13°C in this embodiment) that is smaller than the first threshold ( Step 136).

On the other hand, when the temperature in the cover is 110°C or higher (step 134: No), the tempering threshold is set to a third threshold (4°C in this embodiment) that is smaller than the second threshold (step 138). After the tempering threshold value is set according to the temperature in the cover in this way, the judgment criterion setting process of FIG. 7 is ended and the process of returning to the tempering detection process of FIG. 6 is ended. In addition, in this embodiment, the control unit 50 that sets the tempering threshold according to the temperature in the cover corresponds to the "judgment criterion setting unit" of the present invention.

In the flashback detection process, when returning from the judgment criterion setting process (step 102), next, it is judged whether a predetermined sampling time (15 seconds in this embodiment) has passed since the last measurement of the temperature in the cover (Step 104). In the gas furnace 1 of the present embodiment, the temperature in the hood is measured every time the sampling time has elapsed, and if the sampling time has not elapsed (step 104: No), it stands by until the sampling time elapses.

After that, when the sampling time has elapsed (step 104: Yes), the temperature sensor 32 is used to measure the temperature in the cover (step 106), and it is determined whether the measured temperature in the cover is a predetermined cut-off temperature (in this embodiment). Medium is 155°C) or higher (Step 108). When the temperature in the cover is higher than the cut-off temperature (step 108: Yes), it is determined that the inside of the cover 30 becomes high Normally (for example, reverse injection occurs in the main burner mixing pipe 18 or the sub-burner mixing pipe 19) and become a dangerous state. The gas shut-off valve 41 is closed to forcibly extinguish the flame (step 110), after which the return of FIG. 6 is ended. Fire detection processing.

On the other hand, when the temperature in the cover is lower than the cut-off temperature (step 108: No), the amount of increase in the temperature in the cover relative to the reference time is acquired (step 112). As described above, in the gas stove 1 of this embodiment, the temperature in the hood is measured every time the sampling time (15 seconds) has elapsed. However, the time when the temperature in the hood was last measured is not used as the reference time, but retrospective The time within a predetermined judgment period (5 minutes in this embodiment) is used as the reference time. In addition, when the time elapsed since the ignition of the stove burner 4 has not reached the judgment period, the time at the ignition of the stove burner 4 is set as the reference time.

Then, after obtaining the increase in the temperature in the hood measured in step 106 with respect to the temperature in the hood measured at the reference time, it is determined whether the obtained increase exceeds the tempering threshold set at the reference time (step 114 ). As a result, when the amount of increase in the temperature in the cover exceeds the tempering threshold (step 114: Yes), it is determined that tempering has occurred, and the gas shutoff valve 41 is closed to forcibly extinguish the flame (step 110), after which the end of FIG. 6 Tempering detection processing. In addition, in this embodiment, the control unit 50 that determines whether the increase in the temperature in the cover exceeds the tempering threshold corresponds to the "determination means" of the present invention. In addition, the control unit 50 that performs control to close the gas shutoff valve 41 corresponds to the “gas shutoff unit” of the present invention.

In contrast, when the amount of increase in the temperature in the cover does not exceed the tempering threshold (step 114: No), the determination criterion setting process is executed according to the temperature in the cover measured in step 106 (step 116). In the determination criterion setting processing of this step 116, the same processing as the determination criterion setting processing of the above-mentioned step 102 (refer to FIG. 7) is executed. That is, according to step 106 The tempering threshold value is set to one of the first threshold value, the second threshold value, and the third threshold value according to the measured temperature in the cover.

Next, it is judged whether or not the furnace burner 4 is stopped from burning by the operation of the operation knob 6 (step 118). Then, in the case of continuing combustion (step 118: No), the process returns to step 104, and after the sampling time has elapsed, the temperature in the hood is measured again, and the subsequent processes described above are repeated. Therefore, when the tempering is judged in step 114 performed after the judgment period (5 minutes) has elapsed, the tempering threshold set in step 116 can be used.

While the process is repeated in this way, if no flashback is detected, when the stove burner 4 is stopped by operating the operation knob 6 (step 118: Yes), the flashback detection process of FIG. 6 ends.

FIG. 8 is an explanatory diagram showing an example of detecting whether or not flashback has occurred in the sub-combustor mixing pipe 19 in the gas furnace 1 of the present embodiment according to the flashback detection processing. In the graph of Fig. 8, the temperature in the cover at the reference time is taken as the horizontal axis, and the temperature rise ΔT during the judgment period (5 minutes) of the temperature in the cover relative to the reference time is taken as the vertical axis. The temperature rise amount ΔT in the case where the temperature in the hood is normally combusted by the stove burner 4 is indicated, and the temperature rise amount ΔT in the case where the temperature in the hood is tempered in the sub-burner mixing pipe 19 is indicated by a solid line. In addition, the broken line indicates the tempering threshold value set based on the temperature in the cover at the reference time.

As shown in the figure, when the stove burner 4 is burning normally and when the secondary burner mixing pipe 19 is backfired, the temperature in the hood at the reference time is higher, and the temperature in the hood rises ΔT relative to the reference time. The smaller. In addition, the higher the temperature in the hood at the reference time, the temperature increase in the hood relative to the reference time ΔT during normal combustion and the temperature increase in the hood relative to the reference time ΔT when tempering occurs The smaller the gap.

Therefore, in the gas furnace 1 of this embodiment, as described above, the tempering threshold is set based on the temperature in the hood at the reference time. If the temperature in the hood is less than 80°C, the tempering threshold is set to the first threshold. If the temperature is 80°C or more and less than 110°C, set the tempering threshold to a second threshold value smaller than the first threshold. If the temperature in the cover is 110°C or higher, set the tempering threshold to a second threshold value smaller than the second threshold. 3 threshold. The first threshold value is set by experiment in advance to be greater than the maximum value of the temperature increase ΔT during normal combustion when the temperature in the hood at the reference time is less than 80°C and greater than the temperature increase ΔT when tempering occurs. The minimum value is small (23°C in this embodiment). Similarly, the second threshold is set so that the temperature in the hood at the reference time is in the range from 80°C to 110°C, which is greater than the maximum value of the temperature increase ΔT during normal combustion and is greater than the temperature increase when flashback occurs. The minimum value of the amount ΔT is smaller (in this embodiment, it is 13°C), and the third threshold is set to the amount of temperature increase Δ compared to the normal combustion when the temperature in the hood at the reference time is 110°C or higher The maximum value of T is large and a value smaller than the minimum value of the temperature increase amount ΔT at the time of occurrence of tempering (4°C in this embodiment).

In this way, in the gas stove 1 of the present embodiment, by changing the tempering threshold value according to the temperature in the hood at the reference time, not only can the temperature inside the hood 30 be lower immediately after the stove burner 4 is ignited When tempering occurs in the state, it can be detected that tempering occurs in the sub-burner mixing tube 19 based on the temperature increase ΔT of the temperature in the hood during the judgment period exceeding the tempering threshold value. When the combustor 4 continues to burn and becomes hot while flashback occurs, the occurrence of flashback in the sub-combustor mixing pipe 19 can also be detected based on the temperature increase ΔT of the hood temperature in the judgment period exceeding the flashback threshold.

In addition, since the tempering threshold on the low temperature side of the cover temperature at the reference time (when the temperature inside the cover 30 is low) is set to be greater than the high temperature side of the cover temperature at the reference time (the inside of the cover 30 becomes hot) State) the tempering threshold value, so it can suppress that although no tempering occurs The amount of temperature rise ΔT exceeds the tempering threshold, and the occurrence of tempering is erroneously detected.

The gas stove 1 of this embodiment described above also has the following modification examples. Hereinafter, the modification examples will be explained focusing on the differences from the above-mentioned embodiment. In addition, in the description of the modified example, the same reference numerals are given to the same configurations as those of the above-mentioned embodiment, and the description is omitted.

FIG. 9 is an explanatory diagram showing an example in which the occurrence of backfire in the sub-combustor mixing pipe 19 is detected in the gas furnace 1 of the first modification. In FIG. 9, as in FIG. 8, the temperature in the cover at the reference time is taken as the horizontal axis, and the temperature increase ΔT during the judgment period (5 minutes) of the temperature in the cover relative to the reference time is taken as the vertical axis. The one-dot chain line indicates the temperature rise ΔT of the temperature in the hood when the stove burner 4 is burning normally, and the solid line indicates the temperature in the hood when the secondary burner mixing tube 19 is backfired. The amount of rise △T. In addition, in the gas burner 1 of the above embodiment, the tempering threshold is set in three steps (the first threshold, the second threshold, and the third threshold) based on the temperature in the hood at the reference time. In contrast, In the gas furnace 1 of the first modified example, as shown by the broken line in the figure, the tempering threshold is set linearly based on the temperature in the cover at the reference time.

The straight line exemplified by the broken line in Fig. 9 is obtained as follows: For the temperature in the hood at each reference time (for example, every 10°C), the temperature rise ΔT during normal combustion and the temperature at which backfire occurs The intermediate value between the amount of increase ΔT, and the threshold value adjusted from the intermediate value in consideration of safety is set, and the linear expression is further used to approximate these threshold values. In the gas furnace 1 of the first modification, in the determination criterion setting processing (step 102, step 116) in the tempering detection processing shown in FIG. 6, the first-order approximation equation shown by the broken line in FIG. 9 is set to The tempering threshold corresponding to the temperature in the hood at the reference time.

In the gas furnace 1 of the first modification as described above, the tempering threshold is changed linearly according to the temperature in the cover at the reference time, which is similar to the case where the tempering threshold is changed in a stepwise manner. In particular, the tempering threshold can be set to be larger on the low temperature side of the temperature in the hood at the reference time. Therefore, it is possible to prevent tempering not occurring but the temperature increase ΔT exceeding the tempering threshold and judging that tempering has occurred. Misdetection. On the other hand, on the high temperature side of the temperature in the cover at the reference time, the tempering threshold can be set to be small. Therefore, it is possible to suppress the occurrence of tempering but the temperature increase ΔT does not exceed the tempering threshold and it is impossible to determine that the tempering has occurred. Undetected situations like fire.

In addition, in the above-mentioned embodiment, the determination period for obtaining the temperature rise amount ΔT of the temperature in the cover is set to 5 minutes, but the present invention is not limited to this. The determination period may be set based on the temperature in the cover at the reference time. Fig. 10 is an explanatory diagram for comparing the temperature rise amount ΔT of the temperature in the cover while changing the judgment period. In the graph of Fig. 10, the temperature in the hood at the reference time is taken as the horizontal axis, and the temperature rise ΔT during the judgment period of the hood temperature relative to the reference time is taken as the vertical axis, indicating that the temperature in the hood is mixed in the sub-combustor The amount of temperature increase ΔT in the case where the pipe 19 is tempered is indicated by a solid line when the judgment period is set to 5 minutes, and a two-dot chain line is shown when the judgment period is set to 3 minutes.

As shown in the figure, when the temperature in the cover at the reference time is less than 70°C, if the determination period is set to 3 minutes, the temperature increase ΔT of the temperature in the cover becomes substantially constant (peak). That is, when the temperature in the hood at the reference time is less than 70°C, when tempering occurs in the sub-combustor mixing pipe 19, the temperature in the hood will be at least 3 minutes after the tempering occurs with the tempering. The time has risen sharply. On the other hand, when the temperature in the cover at the reference time is 70°C or higher, the temperature increase ΔT of the temperature in the cover when the judgment time is set to 5 minutes is compared with the temperature increase ΔT in the case where the judgment time is set to 3 minutes. There is no big difference in the temperature rise ΔT of the temperature inside the cover. That is, when the temperature in the hood at the reference time is 70°C or higher, even if tempering occurs in the sub-burner mixing tube 19, the temperature in the hood will immediately converge with the increase in the tempering, and the tempering will occur automatically. Within 3 minutes In a saturated state.

FIG. 11 is a flowchart of the judgment criterion setting process (step 102 and step 116 in FIG. 6) executed by the control unit 50 of the second modification. In the determination criterion setting process of the second modification example, first, the tempering threshold is set based on the temperature in the cover measured by the temperature sensor 32 (step 150). In the processing of this step 150, the temperature in the hood may be set in a stepwise manner based on the tempering threshold as in the above-mentioned embodiment, or the temperature in the hood may be set in a linear manner as in the first modification.

Next, it is determined whether the temperature in the cover measured by the temperature sensor 32 is less than 70°C (step 152). And, when the temperature in the cover is less than 70°C (step 152: Yes), the determination period is set to the first period (5 minutes in the second modification) (step 154).

On the other hand, when the temperature in the cover is 70°C or higher (step 152: No), the judgment period is set to a second period shorter than the first period (3 minutes in the second modification) (step 156 ). After the determination period is set based on the temperature in the cover in this way, the determination criterion setting process of FIG. 11 is ended, and the backfire detection process of FIG. 6 is returned. Then, in the process of step 112 performed at the time after the set judgment period has elapsed, the temperature rise amount of the temperature in the cover relative to the reference time for setting the judgment period is acquired.

In the gas furnace 1 of the second modification as described above, by changing the judgment period based on the temperature in the hood at the reference time, it is possible to ensure sufficient time on the low-temperature side of the temperature in the hood (when the temperature inside the hood 30 is low) Accurately grasp the temperature increase amount ΔT of the temperature rise in the hood with tempering during the judgment period, because the difference between the temperature increase amount ΔT during normal combustion and the temperature increase amount ΔT when tempering occurs becomes larger, so , Can suppress false detection. In addition, on the high-temperature side of the temperature in the cover (when the inside of the cover 30 is heated), the temperature in the cover is immediately saturated as the tempering increases. Therefore, by shortening the judgment period, the occurrence of tempering can be quickly detected .

As mentioned above, although the gas furnace 1 of this embodiment and a modification was demonstrated, this invention is not limited to the above-mentioned embodiment and modification, and can be implemented in various ways within the range which does not deviate from the summary.

For example, in the above-mentioned present embodiment and modification examples, the stove burner 4 is described as a so-called main and sub-burner having a dual structure including a main burner portion 11 and a sub-burner portion 12. However, in a single burner that does not have the sub-burner unit 12, flashback sometimes occurs, especially when the heating power is set to be weak (to make the fuel gas supply amount smaller), the temperature in the hood varies The rising amount of the flashback rise is small, so the present invention can be preferably applied to detect flashback.

In addition, in the second modification described above, the judgment period is set in two stages (the first period and the second period) according to the temperature in the cover. However, it is not limited to this, and may be based on the temperature in the cover. Set the judgment period in a straight line.

Claims (4)

A gas stove is equipped with a stove burner including a burner body having a plurality of burners and a mixing tube extending from the burner body. When fuel gas supplied through a gas passage is injected from a nozzle to the mixing tube In the case of an open end, the mixed gas of the fuel gas and the primary air flowing in from the open end is ejected from the burner through the mixing tube. The feature is that the gas stove includes a cover that covers the mixing tube and accommodates the open end On the inside; the temperature sensor is installed on the aforementioned cover and can measure the temperature inside the cover; the judgment unit periodically obtains the increase in the temperature measured by the aforementioned temperature sensor during a predetermined judgment period, and Determine whether the amount of increase exceeds the prescribed tempering threshold; the gas cut-off unit is to cut off the supply of the fuel gas when the judgment unit determines that the amount of rise exceeds the tempering threshold; And the judgment criterion setting unit sets the tempering threshold value according to the temperature inside the cover, and changes the tempering threshold value according to the temperature inside the cover during the combustion process of the mixed gas. The gas furnace described in the first item of the patent application, wherein the determination criterion setting unit not only sets the tempering threshold value based on the temperature inside the cover, but also sets the determination period based on the temperature inside the cover. The gas stove described in item 1 or 2 of the scope of patent application, wherein any one of the mixing tube and the hood is provided in contact with any other of the mixing tube and the hood to remove heat from The mixing tube is transferred to the heat transfer part of the cover. Such as the gas stove described in item 3 of the scope of patent application, in which, The aforementioned cover is formed of a material having a thermal conductivity greater than that of the aforementioned mixing pipe.

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