Heating cooker and gas burner mounted on heating cooker

Abstract

The invention provides a heating cooker and a gas burner. An annular burner head is placed on a burner body having an annular mixing chamber to cover an upper surface opening of the mixing chamber, and a lower end surface of a cylindrical wall provided perpendicularly from an outer edge of the burner head is in contact with a placement surface around the upper surface opening. A plurality of flame ports are defined in the outer periphery of the cylindrical wall by a plurality of grooves and a mounting surface, the grooves being recessed in the lower end surface in the radial direction. In addition, a concave gas storage chamber is arranged on the lower end face of the cylindrical wall at the position opposite to the fire support claw, and a central notch, a left notch and a right notch are formed in the outer wall of the gas storage chamber. A communication part for communicating the mixing chamber and the gas storage chamber is provided so as to avoid a position facing the central cutout, and the opening area of the outer peripheral side of the cylindrical wall is expanded with respect to the opening area of the gas storage chamber side in a left passage and a right passage defined by the left cutout and the right cutout, respectively, and the placement surface.

Description

Technical Field

[0001] The present invention relates to a heating cooker that heats a cooking container placed on a trivet using combustion in a gas burner, and a gas burner mounted on the heating cooker. Background Art

[0002] Heating cookers that burn a mixture of fuel gas and air in a gas burner to heat a cooking container such as a pot placed on a trivet from below are widely used. A gas burner generally includes: a burner body having an annular mixing chamber supplied with the mixture gas; and an annular burner head mounted on the burner body to cover the upper surface opening of the mixing chamber. The burner head has a cylindrical wall vertically provided downward in a cylindrical shape from an outer edge portion, and a plurality of radially transverse grooves are recessed in the lower end surface of the cylindrical wall at intervals in the circumferential direction. On the other hand, in the burner body, an annular mounting surface is provided around the upper surface opening of the mixing chamber. When the burner head is mounted on the burner body, the lower end surface of the cylindrical wall abuts against the mounting surface, and a plurality of flame ports communicating with the mixing chamber and opening to the outside of the cylindrical wall are defined by the plurality of grooves and the mounting surface. When the mixture gas supplied to the mixing chamber flows out from the flame ports and is ignited, combustion of the mixture gas starts, and a flame is formed outside the flame ports.

[0003] In addition, the trivet has a plurality of trivet claws supported by an annular frame surrounding the gas burner and extending upward toward the gas burner. The cooking container is supported by the plurality of trivet claws and heated from below by combustion in the gas burner. At this time, since the flame of the gas burner grills the trivet claws (so-called grilled claws), the heat of the flame is taken by the trivet claws instead of the cooking container. Therefore, there are cases where not only the thermal efficiency is reduced, but also the flame is cooled, resulting in poor combustion and deterioration of the CO concentration. Therefore, measures are taken to make the flame ports (trivet flame ports) at positions opposite to the trivet claws among the plurality of flame ports opening to the outside of the gas burner (the cylindrical wall of the burner head) smaller than the flame ports at positions not opposite to the trivet claws (for example, Patent Document 1).

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2023-66271 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] However, although the burning of the claws can be suppressed by reducing the flame of the fire supporter flame port when the gas burner is at high power by reducing the flame as described above, if the flame of the fire supporter flame port becomes too small when the fire power is low (the flow rate of the mixed gas flowing out of the fire supporter flame port becomes too small), it becomes difficult to spread the flame to the adjacent flame ports. Therefore, there is a problem that there is a limit to the reduction of the fire supporter flame port.

[0009] The present invention has been made in response to the above-mentioned problems in the prior art, and an object of the present invention is to provide a technology capable of suppressing the burning of claws at a high firepower while ensuring the burning performance of a gas burner at a low firepower.

[0010] Solutions for solving problems

[0011] In order to solve the above-mentioned problems, the heating cooker of the present invention adopts the following structure. That is,

[0012] A heating cooker, which uses a burner body and an annular burner head to form a gas burner, the burner body having an annular mixing chamber supplied with a mixed gas of fuel gas and air, the annular burner head being placed on the burner body to cover an upper surface opening of the mixing chamber, a plurality of grooves transverse in the radial direction are recessed and provided at intervals in the circumferential direction on the lower end surface of a cylindrical wall vertically provided in a cylindrical shape from an outer edge portion of the burner head toward the bottom, and the upper surface opening of the mixing chamber of the burner body An annular mounting surface is provided around the burner, and when the burner head is placed on the burner body and the lower end surface of the cylindrical wall abuts against the mounting surface, a plurality of flame ports that are connected to the mixing chamber and open on the outer periphery of the cylindrical wall are divided by the plurality of grooves and the mounting surface. The heating cooker burns the mixed gas flowing out of the flame ports to heat the cooking container placed on the fire support, and the fire support has a plurality of fire support claws that are supported by an annular frame surrounding the gas burner and extend toward the top of the gas burner, characterized in that

[0013] A concave gas storage chamber is provided on the lower end surface of the cylindrical wall at a position opposite to the fire support claw, and the gas storage chamber is surrounded by an outer wall, an inner wall and a radial side wall, the outer wall is formed along the outer periphery of the cylindrical wall, the inner wall is formed along the inner periphery of the cylindrical wall, and the radial side walls are formed on both sides separated by the outer wall and the inner wall. If the burner head is placed on the burner body, the lower surface opening of the gas storage chamber is closed by the placement surface.

[0014] On the outer wall, as three notches for connecting the outer periphery of the cylindrical wall to the gas accumulation chamber, a central notch disposed at the center opposite to the fire support claw, and a left notch and a right notch disposed on both sides of the central notch are provided.

[0015] A communication portion for allowing the mixed gas to flow from the mixing chamber into the gas accumulation chamber is provided in a manner to avoid the position of the gas accumulation chamber opposite to the central notch. And,

[0016] The opening area on the outer peripheral side of the cylindrical wall of the left passage divided by the left notch and the placement surface and the right passage divided by the right notch and the placement surface expands relative to the opening area on the gas accumulation chamber side.

[0017] According to the heating cooker of the present invention configured as described above, when the gas burner is at low heat, the flow rate of the mixed gas supplied to the mixing chamber is small. Therefore, the mixed gas slowly flows from the mixing chamber into the gas accumulation chamber through the communication portion. And, the inflowing mixed gas diffuses in the gas accumulation chamber and takes time to flow toward the three notches (central notch, left notch, right notch). Therefore, the mixed gas flows out from any one of the three fire support flame ports (central flame port, left flame port, right flame port) that open to the outer periphery of the cylindrical wall through each of the three notches and the placement surface at the same flow rate, thereby ensuring the afterburning performance at low heat. On the other hand, when the gas burner is at high heat, the flow rate of the mixed gas supplied to the mixing chamber increases significantly. Therefore, the mixed gas violently flows from the mixing chamber into the gas accumulation chamber through the communication portion. However, the communication portion is provided in a manner to avoid the position of the gas accumulation chamber opposite to the central notch. Therefore, the inflowing mixed gas does not directly flow through the gas accumulation chamber and directly flow toward the central notch, but a part of the mixed gas that has temporarily diffused in the gas accumulation chamber flows toward the central notch. Therefore, even at high heat, it is possible to avoid a significant increase in the flow rate of the mixed gas flowing out from the central flame port relative to the flow rate of the mixed gas flowing out from the central flame port at low heat, and it is possible to suppress the burning of the claws caused by the flame of the central flame port. Moreover, the opening area on the outer peripheral side (left flame port and right flame port) of the cylindrical wall of the left passage and the right passage expands relative to the opening area on the gas accumulation chamber side. Therefore, the flow velocity of the mixed gas passing through the left passage and the right passage decreases, and the outflow direction of the mixed gas is dispersed and the flame stays near the left flame port and the right flame port (short flame can be achieved). As a result, it is possible to suppress the rise of the flames of the left flame port and the right flame port, and it is possible to suppress the burning of the claws caused by the flames of the left flame port and the right flame port.

[0018] Alternatively, the opening areas of the left passage and the right passage in the heating cooker of the present invention described above expand in a direction away from the central notch as they go from the gas accumulation chamber side toward the outer peripheral side of the cylindrical wall.

[0019] In this case, the flames of the left flame port and the right flame port are formed to spread in a direction away from the fire support claws opposite to the central flame port in addition to being short-flamed. Therefore, it is possible to further suppress the claw roasting caused by the flames of the left flame port and the right flame port.

[0020] In the heating cooker of the present invention like this, it is also possible that there is a vertical surface vertically provided downward from the inner edge portion of the placement surface, the communication portion is located between the vertical surface and the inner wall, and is formed on the left and right sides avoiding the central portion opposite to the central notch and communicates in the vertical direction.

[0021] In this case, the mixed gas flows into the gas accumulation chamber through the vertical communication portion. Therefore, the inflowing mixed gas temporarily flows upward and diffuses while changing its direction at the upper surface of the gas accumulation chamber. Moreover, the communication portion avoids the central portion and is close to the left and right sides, so that a part of the mixed gas temporarily diffused in the gas accumulation chamber flows toward the central notch. Therefore, even when the gas burner is at high heat, it is possible to suppress the flow rate of the mixed gas flowing out from the central flame port and suppress the claw roasting caused by the flame of the central flame port. In addition, although the mixed gas flowing into the gas accumulation chamber through the communication portions on the left and right sides at high heat is likely to flow toward the left notch and the right notch with respect to the central notch, as described above, it is short-flamed due to the expansion of the opening areas of the left passage and the right passage. Therefore, it is possible to suppress the claw roasting caused by the flames of the left flame port and the right flame port. Furthermore, when the gas burner is at low heat, the mixed gas slowly flows through the vertical communication portion and takes time to diffuse in the gas accumulation chamber. Therefore, the mixed gas can flow out equally from any of the three fire support flame ports to ensure the afterburning performance.

[0022] In addition, in the heating cooker of the present invention like this, it is also possible that the communication portion is formed on the side walls on both sides of the gas accumulation chamber and communicates in the circumferential direction of the cylindrical wall.

[0023] In this case, there is a tendency that when the gas burner is at high heat, the mixed gas flows violently from the inner side to the outer side in the radial direction of the mixing chamber, and it is difficult for the mixed gas to flow into the gas accumulation chamber through the communication part that communicates in the circumferential direction. Moreover, the mixed gas flowing in the circumferential direction does not flow directly out from the three burner flame ports that open in the radial direction, but the mixed gas that has temporarily diffused in the gas accumulation chamber disperses to the three burner flame ports (three notches). Therefore, it is possible to suppress the flow rate of the mixed gas flowing out from each of the three burner flame ports and suppress the roasting of the claws. On the other hand, when the gas burner is at low heat, the mixed gas flows slowly from the inner side to the outer side in the radial direction of the mixing chamber, so that the mixed gas easily flows into the gas accumulation chamber through the communication part that communicates in the circumferential direction. Therefore, compared with the high heat situation, the flow rate of the mixed gas flowing into the gas accumulation chamber is not easily reduced, and a sufficient flow rate of the mixed gas flows to each of the three burner flame ports, ensuring the afterburning performance.

[0024] In the above-mentioned heating cooker of the present invention, it can also be as follows. First, side notches that connect the outside and the inside of the gas accumulation chamber are provided on the side walls on both sides of the gas accumulation chamber, and the communication part is demarcated by the side notches and the mounting surface. Moreover, the side notches widen toward the outer peripheral side of the cylindrical wall as they go from the outside to the inside of the gas accumulation chamber.

[0025] In this way, it is possible to guide the mixed gas that has flowed into the gas accumulation chamber through the communication part along the inner surface of the outer peripheral side of the cylindrical wall at the side notches to the left passage and the right passage. As a result, when the gas burner is at high heat, it is possible to suppress the flow rate of the mixed gas flowing out from the central flame port opposite to the burner claw and suppress the roasting of the claws caused by the flame of the central flame port. In addition, as described above, at the left flame port and the right flame port, due to the expansion of the opening area, the flame becomes short, and it is possible to suppress the roasting of the claws. On the other hand, when the gas burner is at low heat, it is possible to promote the outflow of the mixed gas from the left flame port and the right flame port where the flame becomes short and ensure the afterburning performance.

[0026] In addition, to solve the above-mentioned problems, the gas burner of the present invention adopts the following structure. That is,

[0027] A gas burner is provided on the premise of being mounted on a heating cooker, the heating cooker heats a cooking container placed on a fire support, the fire support having a plurality of fire support claws supported by an annular frame, the gas burner comprising: a burner body having an annular mixing chamber supplied with a mixed gas of fuel gas and air; and an annular burner head mounted on the burner body and covering an upper surface opening of the mixing chamber, the lower end surface of a cylindrical wall vertically arranged in a cylindrical shape from an outer edge portion of the burner head toward downward, A plurality of grooves that are transverse in the radial direction are recessed and spaced apart in the circumferential direction, and an annular mounting surface is provided around the upper surface opening of the mixing chamber of the burner body. When the burner head is placed on the burner body and the lower end surface of the cylindrical wall abuts against the mounting surface, a plurality of flame ports that are connected to the mixing chamber and open on the outer circumference of the cylindrical wall are divided by the plurality of grooves and the mounting surface. The gas burner burns the mixed gas that flows out of the flame ports, and is characterized in that:

[0028] A concave gas storage chamber is provided on the lower end surface of the cylindrical wall at a position opposite to the fire support claw when the cooking device is mounted on the inner side of the frame, and the gas storage chamber is surrounded by an outer wall, an inner wall and radial side walls, the outer wall is formed along the outer circumference of the cylindrical wall, the inner wall is formed along the inner circumference of the cylindrical wall, and the radial side walls are formed on both sides separated by the outer wall and the inner wall. If the burner head is placed on the burner body, the lower surface opening of the gas storage chamber is closed by the placement surface.

[0029] The outer wall is provided with three notches for connecting the outer periphery of the cylindrical wall with the gas storage chamber, including a central notch arranged in the center opposite to the fire support claw, and a left notch and a right notch arranged on both sides of the central notch.

[0030] A communication portion for allowing the mixed gas to flow from the mixing chamber into the gas storage chamber is provided in a manner avoiding a position of the gas storage chamber that faces the central notch, and

[0031] The opening areas of the left passage defined by the left notch and the placement surface and the right passage defined by the right notch and the placement surface on the outer peripheral side of the cylindrical wall are expanded relative to the opening areas on the gas storage chamber side.

[0032] If such a gas burner of the present invention is mounted on a heating cooker, when the heating power is low, the flow rate of the mixed gas supplied to the mixing chamber is small. Therefore, the mixed gas slowly flows from the mixing chamber through the communication portion into the gas accumulation chamber. And the inflowing mixed gas diffuses in the gas accumulation chamber and takes time to flow toward the three notches (the central notch, the left notch, and the right notch). Therefore, the mixed gas flows out from any one of the three burner ports (the central burner port, the left burner port, and the right burner port) that open to the outer periphery of the cylindrical wall through each of the three notches and the mounting surface at the same flow rate, so that the afterburning performance at low heating power can be ensured. On the other hand, when the heating power is high, the flow rate of the mixed gas supplied to the mixing chamber increases significantly. Therefore, the mixed gas violently flows from the mixing chamber through the communication portion into the gas accumulation chamber. However, the communication portion is arranged so as to avoid the position of the gas accumulation chamber opposite to the central notch. Therefore, the inflowing mixed gas does not directly flow through the gas accumulation chamber and directly flow toward the central notch, but a part of the mixed gas that has temporarily diffused in the gas accumulation chamber flows toward the central notch. Therefore, even when the heating power is high, it is possible to avoid a significant increase in the flow rate of the mixed gas flowing out from the central burner port relative to the flow rate of the mixed gas flowing out from the central burner port at low heating power, and it is possible to suppress the burning of the claws caused by the flame of the central burner port. Moreover, the opening area on the outer peripheral side (the left burner port and the right burner port) of the cylindrical walls of the left passage and the right passage expands relative to the opening area on the gas accumulation chamber side. Therefore, the flow velocity of the mixed gas passing through the left passage and the right passage decreases, and the outflow direction of the mixed gas is dispersed and the flame stays near the left burner port and the right burner port (short flame can be achieved). As a result, it is possible to suppress the rise of the flames of the left burner port and the right burner port, and it is possible to suppress the burning of the claws caused by the flames of the left burner port and the right burner port. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 FIG. 6 is a perspective view showing the upper appearance of a gas stove 1 as an example of the heating cooker of the present embodiment.

[0034] Figure 2 FIG. 10 is a longitudinal sectional view showing the internal structure of the gas burner 10.

[0035] Figure 3 FIG. 14 is an enlarged sectional view of the main burner port 14 and the flame stabilizing port 15 divided by placing the cylindrical wall 13a of the burner head 13 on the mounting surface 11d of the burner body 11.

[0036] Figure 4 FIG. 18 is an explanatory view showing the structure of the burner port 20 in the gas burner 10 of the first embodiment.

[0037] Figure 5It is a longitudinal sectional view of the fire support flame port 20 of the first embodiment divided by placing the cylindrical wall 13a of the burner head 13 on the placement surface 11d of the burner body 11.

[0038] Figure 6 It is an explanatory diagram conceptually showing the flow of the mixed gas that flows into the gas accumulation chamber 21 from the rear communication part 24 and flows out from the fire support flame port 20 in the gas burner 10 of the first embodiment.

[0039] Figure 7 It is an explanatory diagram showing the structure of the gas accumulation chamber 21 in the gas burner 10 of the second embodiment.

[0040] Figure 8 It is an explanatory diagram conceptually showing the flow of the mixed gas that flows into the gas accumulation chamber 21 from the side communication part 25 and flows out from the fire support flame port 20 in the gas burner 10 of the second embodiment.

[0041] Figure 9 It is an explanatory diagram showing the structure of the gas accumulation chamber 21 in the modified example of the gas burner 10 of the second embodiment.

[0042] Figure 10 It is an explanatory diagram showing the case where both the rear communication part 24 and the side communication part 25 are provided in the gas accumulation chamber 21.

[0043] Explanation of reference numerals

[0044] 1, Gas stove; 2, Top plate; 3, Through hole; 4, Fire support; 4a, Frame body; 4b, Fire support claw; 10, Gas burner; 11, Burner body; 11a, Outer surface plate; 11b, Inner surface plate; 11c, Mixing chamber; 11d, Placement surface; 11e, Vertical surface; 12, Mixing pipe; 12a, Open end; 13, Burner head; 13a, Cylindrical wall; 13b, Fitting cylinder; 13c, Longitudinal passage; 13d, Main flame port groove; 13e, Flame stabilizing port groove; 14, Main flame port; 15, Flame stabilizing port; 16, Burner cover; 16a, Central opening; 17, Temperature sensor; 18, Support rod; 20, Fire support flame port; 20a, Central flame port; 20b, Left flame port; 20c, Right flame port; 21, Gas accumulation chamber; 21a, Outer wall; 21b, Inner wall; 21c, Side wall; 22a, Central notch; 22b, Left notch; 22c, Right notch; 22d, Thin wall part; 22e, Side notch; 22f, Widening surface; 23b, Left passage; 23c, Right passage; 24, Rear communication part; 25, Side communication part; 27, Blocking wall; 30, Gas supply pipe; 31, Nozzle; 32, On-off valve; 33, Flow regulating valve. Detailed implementation manners

[0045] Figure 1 FIG. 1 is a perspective view showing an upper appearance of a gas stove 1 as an example of a heating cooker according to the present embodiment. The gas stove 1 covers an upper surface of a stove body (not shown) with a top plate 2, and an upper portion of a gas burner 10 provided in the stove body protrudes from a through hole 3 formed in the top plate 2. Further, a trivet 4 for placing a cooking container such as a pot above the gas burner 10 is provided on the top plate 2. The trivet 4 has a plurality of (six in the illustrated example) trivet claws 4b supported by an annular frame 4a surrounding the gas burner 10 and extending upward above the gas burner 10. The cooking container is supported by the plurality of trivet claws 4b and is heated from below by the gas burner 10.

[0046] The gas burner 10 is composed of components such as a burner body 11 that serves as a base, a burner head 13 placed on the burner body 11, an annular burner cover 16 installed above the burner head 13, and a temperature sensor 17 provided in a state of protruding from the center of the burner cover 16.

[0047] A plurality of longitudinally long main flame ports 14 are opened on an outer peripheral surface of the burner head 13 at a predetermined interval in the circumferential direction. When a mixed gas of fuel gas and air flows out from the main flame port 14 and is ignited by a spark plug (not shown), combustion of the mixed gas starts and a flame is formed outside the main flame port 14. Further, flame stabilizer ports 15 having a longitudinal dimension shorter than that of the main flame port 14 are opened between adjacent main flame ports 14. The mixed gas also flows out from the flame stabilizer ports 15, and a flame smaller than the flame of the main flame port 14 is formed outside the flame stabilizer ports 15.

[0048] The burner cover 16 suppresses the boiling soup from splashing onto the burner head 13 when the boiling soup overflows from the cooking container placed on the trivet 4. Further, the temperature sensor 17 measures the temperature of the cooking container by bringing an upper end surface into contact with a bottom surface of the cooking container.

[0049] Figure 2 FIG. 2 is a longitudinal sectional view showing an internal structure of the gas burner 10. The burner body 11 has an annular mixing chamber 11c formed inside by opposing and hermetically joining two metal plates (an outer surface plate 11a and an inner surface plate 11b) formed by stamping a thin plate such as stainless steel. On an upper end side of the outer surface plate 11a, an annular placement surface 11d is formed by bending inward, and further, a shorter cylindrical hanging surface 11e is formed by bending an inner edge side of the placement surface 11d downward. And, an upper portion of the outer surface plate 11a protrudes from the through hole 3 onto the top plate 2 (see Figure 1 ), and the burner head 13 is placed on the placement surface 11d. In addition, the burner body 11 is not limited to being made of sheet metal and may be formed by casting (die casting) or the like.

[0050] In addition, a mixing pipe 12 communicating with the mixing chamber 11c extends from the burner main body 11, and a nozzle 31 at the top end of a gas supply pipe 30 for supplying fuel gas is arranged to face the opening end 12a of the mixing pipe 12. An opening and closing valve 32 for opening and closing the gas supply pipe 30 and a flow rate regulating valve 33 for regulating the flow rate of the fuel gas in the gas supply pipe 30 are provided in the gas supply pipe 30. When the opening and closing valve 32 is opened, fuel gas with a flow rate corresponding to the opening degree of the flow rate regulating valve 33 is supplied to the nozzle 31, and the fuel gas ejected from the nozzle 31 flows into the mixing pipe 12 together with the primary air for combustion sucked from the surroundings. Then, the fuel gas and the primary air are mixed in the mixing pipe 12, and the mixed gas is supplied to the mixing chamber 11c.

[0051] The burner head 13 is formed in a ring shape using a metal material such as aluminum alloy or brass by forging or die-casting. A cylindrical wall 13a is vertically provided downward from the outer edge portion of the burner head 13, and a cylindrical fitting cylinder 13b longer than the cylindrical wall 13a is vertically provided downward from the inner edge portion.

[0052] When the burner head 13 is placed on the burner main body 11, the fitting cylinder 13b is fitted inside the inner surface plate 11b, and the lower end surface of the cylindrical wall 13a abuts against a ring-shaped placement surface 11d located around the upper surface opening of the mixing chamber 11c. Thus, the upper surface opening of the mixing chamber 11c is covered by the burner head 13. In addition, as will be described in detail later, a plurality of radially transverse grooves are recessed at intervals in the circumferential direction on the lower end surface of the cylindrical wall 13a, and a plurality of flame ports (main flame ports 14 and flame stabilizing ports 15) are defined by the abutment of the lower end surface of the cylindrical wall 13a against the placement surface 11d. In addition, in the illustrated example, the placement surface 11d is inclined downward toward the inner side in the radial direction, and correspondingly, the lower end surface of the cylindrical wall 13a is also inclined in the same way.

[0053] The inside of the fitting cylinder 13b of the burner head 13 becomes a longitudinal passage 13c that penetrates the gas burner 10 in the vertical direction, and a support rod 18 with a temperature sensor 17 mounted at the upper end thereof penetrates through the longitudinal passage 13c. Above the burner head 13, a ring-shaped burner cover 16 is fixed using a mounting fitting (not shown), and the upper part of the temperature sensor 17 protrudes from a central opening 16a that penetrates the center of the burner cover 16. The temperature sensor 17 is biased upward by a biasing spring (not shown), and the upper end surface of the temperature sensor 17 abuts against the bottom surface of the cooking container placed on the fire support 4.

[0054] Figure 3is an enlarged cross-sectional view of the main flame port 14 and the flame stabilization port 15 defined by placing the cylindrical wall 13a of the burner head 13 on the placement surface 11d of the burner body 11. First, in Figure 3 FIG. (a) shows a cross-sectional view taken at the position of the main flame port 14. As shown in the figure, a relatively deep groove (main flame port groove 13d) that transversely cuts in the radial direction is recessed in the lower end surface of the cylindrical wall 13a at the position of the main flame port 14. When the lower end surface of the cylindrical wall 13a abuts against the placement surface 11d, the main flame port 14 that communicates with the mixing chamber 11c and opens to the outside of the cylindrical wall 13a is defined by the main flame port groove 13d and the placement surface 11d. When the mixed gas in the mixing chamber 11c flows out from this main flame port 14 and the combustion of the mixed gas starts by ignition, a flame is formed outside the main flame port 14. The flow rate of the fuel gas can be adjusted by the flow rate regulating valve 33 of the gas supply pipe 30 as described above, and the flow rate of the mixed gas supplied to the mixing chamber 11c changes according to the opening degree of the flow rate regulating valve 33. Therefore, the heating power of the gas burner 10 for the cooking container can be varied. In addition, the main flame port 14 of the present embodiment corresponds to the "flame port" of the present invention.

[0055] On the other hand, in Figure 3 FIG. (b) shows a cross-sectional view taken at the position of the flame stabilization port 15. A groove (flame stabilization port groove 13e) shallower than the main flame port groove 13d is recessed in the lower end surface of the cylindrical wall 13a at the position of the flame stabilization port 15 in a manner that transversely cuts in the radial direction. When the lower end surface of the cylindrical wall 13a abuts against the placement surface 11d, the flame stabilization port 15 that communicates with the mixing chamber 11c and opens to the outside of the cylindrical wall 13a is defined by the flame stabilization port groove 13e and the placement surface 11d. The mixed gas in the mixing chamber 11c also flows out from the flame stabilization port 15. The flame stabilization port 15 is smaller than the main flame port 14 (shorter in the longitudinal dimension). Therefore, a flame smaller than the main flame port 14 is formed outside the flame stabilization port 15. The flame stabilization port 15 opens between the adjacent main flame ports 14 as described above, and the smaller flame formed outside the flame stabilization port 15 ensures the afterburning performance and flame stability of the larger flame formed outside the main flame port 14.

[0056] On the outer periphery of the cylindrical wall 13a, such main flame ports 14 and flame stabilizing ports 15 are alternately arranged at intervals in the circumferential direction. However, if the flame formed around the cylindrical wall 13a bakes the stay pawl 4b, the heat of the flame that should originally be transferred to the cooking container is taken away by the stay pawl 4b. Therefore, there are cases where not only the thermal efficiency is reduced, but also the flame is cooled to cause poor combustion and the CO concentration deteriorates. In order to suppress the case where the flame bakes the stay pawl 4b (hereinafter, baked pawl) in this way, for the flame port opposite to the stay pawl 4b, although it is generally smaller than the main flame port 14, if it is too small, a sufficient flow rate of the mixed gas cannot flow out at low heat power, and continuous combustion between adjacent flame ports becomes difficult. Therefore, in the gas burner 10 of the present embodiment, the flame port (hereinafter, stay flame port) of the portion opposite to the stay pawl 4b is configured as follows.

[0057] Figure 4 FIG. is an explanatory diagram showing the structure of the stay flame port 20 in the gas burner 10 of the first embodiment. First, in Figure 4 (a), the appearance of the stay flame port 20 opened on the outer periphery of the cylindrical wall 13a of the burner head 13 is shown enlarged. On the outer periphery of the cylindrical wall 13a at the portion opposite to the stay pawl 4b, three flame ports are opened as the stay flame port 20, namely, a central flame port 20a located at the center and left and right flame ports 20b and 20c located on both sides of the central flame port 20a. And, main flame ports 14 are opened on the left and right outer sides of these stay flame ports 20, and flame stabilizing ports 15 are opened on the outer sides of the main flame ports 14.

[0058] In the example shown in the figure, the lateral dimension of the central flame port 20a is about the same as the lateral dimension of the main flame port 14, the longitudinal dimension is shorter than the longitudinal dimension of the main flame port 14, and is longer than the longitudinal dimension of the flame stabilizing port 15. In addition, the lateral dimensions of the left and right flame ports 20b and 20c are longer than the lateral dimension of the flame stabilizing port 15, and the longitudinal dimensions are also slightly longer than the longitudinal dimension of the flame stabilizing port 15. And, the central flame port 20a is longitudinally long with respect to the left and right flame ports 20b and 20c, while the left and right flame ports 20b and 20c are transversely long with respect to the central flame port 20a.

[0059] In Figure 4 (b), the state of the portion of the cylindrical wall 13a of the burner head 13 opposite to the stay pawl 4b as viewed from below is shown enlarged. In the figure, the portion of the lower end surface of the cylindrical wall 13a placed on the placement surface 11d that abuts against the placement surface 11d is marked with hatching. In addition, the dotted line in the figure transparently shows the vertical surface 11e formed on the inner edge side of the placement surface 11d.

[0060] As shown in the figure, a concave gas storage chamber 21 is provided at the lower end surface of the cylindrical wall 13a at the position opposite to the fire support claw 4b, and the gas storage chamber 21 is surrounded by an outer wall 21a formed along the outer periphery of the cylindrical wall 13a, an inner wall 21b formed along the inner periphery of the cylindrical wall 13a, and radial side walls 21c formed on both sides of the outer wall 21a and the inner wall 21b. In addition, when the cylindrical wall 13a of the burner head 13 is placed on the placement surface 11d of the burner body 11, the lower surface opening of the gas storage chamber 21 is closed by the placement surface 11d.

[0061] In addition, the outer wall 21a is provided with three notches, namely, a central notch 22a arranged in the center opposite to the fire support claw 4b, and a left notch 22b and a right notch 22c arranged on both sides of the central notch 22a as notches for connecting the outer periphery of the cylindrical wall 13a with the gas storage chamber 21. And, as will be discussed later, three fire support flame ports 20 (central flame port 20a, left flame port 20b, right flame port 20c) are divided by the lower end surface of the cylindrical wall 13a (outer wall 21a) abutting against the mounting surface 11d. In addition, as shown in the figure, it is ensured that the radial depth of the cylindrical wall 13a of the gas storage chamber 21 is longer than any of the circumferential widths of the central notch 22a, the left notch 22b, and the right notch 22c.

[0062] In addition, thin-walled portions 22d formed by reducing the thickness are provided on the left and right sides of the inner wall 21b avoiding the central portion opposite to the central notch 22a. Also, a rear connecting portion 24 connected in the up-down direction (depth direction in the figure) is formed between the hanging surface 11e formed on the inner edge side of the mounting surface 11d and the thin-walled portion 22d of the inner wall 21b as discussed later. Moreover, a blocking wall 27 longer than the inner wall 21b is vertically provided at a position radially inward (lower side in the figure) than the inner wall 21b. In addition, the rear connecting portion 24 of the first embodiment is equivalent to the "connecting portion" of the present invention.

[0063] Figure 5 1 is a longitudinal sectional view of the flame port 20 of the first embodiment divided by placing the cylindrical wall 13a of the burner head 13 on the mounting surface 11d of the burner body 11. Figure 5 (a) shows a cross-sectional view cut at the position of the central flame port 20a. The central flame port 20a is divided by the central notch 22a of the outer wall 21a and the mounting surface 11d by the lower end surface of the cylindrical wall 13a abutting against the mounting surface 11d, and is connected to the gas storage chamber 21, and is open at the outer periphery of the cylindrical wall 13a. In addition, the central part of the inner wall 21b opposite to the central notch 22a is not provided with a thin-walled portion 22d, and the mixing chamber 11c is separated from the gas storage chamber 21 by the lower end surface of the inner wall 21b abutting against the mounting surface 11d.

[0064] On the other hand, in Figure 5 (b) shows a cross-sectional view taken at the position of the right flame port 20c. In addition, the left flame port 20b is symmetrically arranged with respect to the right flame port 20c, and for the left flame port 20b, it is basically the same as the right flame port 20c. The right flame port 20c is defined by the right-side notch 22c of the outer wall 21a and the placement surface 11d when the lower end surface of the cylindrical wall 13a abuts against the placement surface 11d, communicates with the gas accumulation chamber 21, and opens to the outside of the circumference of the cylindrical wall 13a. In addition, a thin wall portion 22d is provided on the right-side portion of the inner wall 21b opposite to the right-side notch 22c, and a rear communication portion 24 is formed between the vertical surface 11e formed on the inner edge side of the placement surface 11d and the thin wall portion 22d to communicate in the vertical direction. Therefore, the mixed gas in the mixing chamber 11c flows into the gas accumulation chamber 21 through the rear communication portion 24. At this time, at a position radially inside the inner wall 21b (thin wall portion 22d), the flow of the mixed gas from the radially inner side to the outer side of the mixing chamber 11c toward the rear communication portion 24 is blocked by the blocking wall 27 provided at a position below the inner wall 21b. Therefore, the mixed gas flowing into the gas accumulation chamber 21 is rectified so that the mixed gas flows upward between the vertical surface 11e and the blocking wall 27.

[0065] Figure 6 is an explanatory diagram conceptually showing the flow of the mixed gas flowing from the rear communication portion 24 into the gas accumulation chamber 21 and flowing out from the fire support flame port 20 in the gas burner 10 of the first embodiment. In the figure, similar to Figure 4 (b), it shows the state of the portion of the cylindrical wall 13a of the burner head 13 opposite to the fire support claw 4b as viewed from below, and the portion of the lower end surface of the cylindrical wall 13a that abuts against the placement surface 11d is hatched, and the vertical surface 11e is represented by a dotted line. In addition, the hollow arrows in the figure conceptually represent the flow of the mixed gas. In addition, in Figure 6 , in order to avoid making the drawing complicated, a part of the reference numerals is omitted from the description.

[0066] In Figure 6 (a) shows the flow of the mixed gas in the gas burner 10 at low heat. At low heat, the flow rate of the mixed gas supplied to the mixing chamber 11c is small. Therefore, the mixed gas slowly flows from the mixing chamber 11c into the gas accumulation chamber 21 through the rear communication portion 24. Then, the mixed gas that has flowed in diffuses in the gas accumulation chamber 21 and takes time to flow toward the fire support flame port 20. In particular, in the first embodiment, the mixed gas flows upward through the rear communication portion 24 that communicates in the vertical direction (refer to Figure 5In (b) thereof, while changing the orientation and diffusing at the upper surface of the gas accumulation chamber 21, it slowly flows. As a result, the mixed gas flows out from any one of the three burner flame ports 20 (central flame port 20a, left flame port 20b, right flame port 20c) at the same flow rate, thereby ensuring the afterburning performance at low heat.

[0067] On the other hand, in Figure 6 (b) of FIG. shows the flow of the mixed gas at high heat of the gas burner 10. At high heat, the flow rate of the mixed gas supplied to the mixing chamber 11c increases significantly. Therefore, the mixed gas violently flows into the gas accumulation chamber 21 from the mixing chamber 11c through the rear communication part 24. However, the rear communication part 24 is arranged so as to avoid the position opposite to the central notch 22a. Therefore, the inflowing mixed gas does not directly pass through the gas accumulation chamber 21 and directly flow out from the central flame port 20a (central notch 22a), and a part of the mixed gas temporarily diffused in the gas accumulation chamber 21 flows toward the central notch 22a. In addition, by narrowing the gap between the vertical surface 11e of the rear communication part 24 and the thin wall part 22d in advance, even if the flow rate of the mixed gas supplied to the mixing chamber 11c increases, the flow rate of the mixed gas flowing into the gas accumulation chamber 21 is restricted. Therefore, even at high heat, it is possible to avoid a significant increase in the flow rate of the mixed gas flowing out from the central flame port 20a relative to the flow rate of the mixed gas flowing out from the central flame port 20a at low heat, and it is possible to suppress the roasting of the claws caused by the flame of the central flame port 20a.

[0068] Moreover, since the rear communication part 24 is arranged at positions opposite to the left notch 22b and the right notch 22c, the inflowing mixed gas is more likely to flow toward the left notch 22b and the right notch 22c compared to the central notch 22a. As a result, it preferentially flows out from the left flame port 20b and the right flame port 20c compared to the central flame port 20a. Therefore, as shown in the figure, the lateral width (circumferential width) on the outer peripheral side of the cylindrical wall 13a of the left notch 22b and the right notch 22c expands relative to the lateral width on the gas accumulation chamber 21 side. That is, the opening area on the outer peripheral side (left flame port 20b and right flame port 20c) of the cylindrical wall 13a of the left passage 23b divided by the left notch 22b and the mounting surface 11d and the right passage 23c divided by the right notch 22c and the mounting surface 11d expands relative to the opening area on the gas accumulation chamber 21 side. Therefore, the flow velocity of the mixed gas passing through the left passage 23b and the right passage 23c decreases, and the outflow direction of the mixed gas is dispersed and the flame stays near the left flame port 20b and the right flame port 20c (short flame can be achieved). As a result, it is possible to suppress the rise of the flame of the left flame port 20b and the right flame port 20c, and suppress the roasting of the claws caused by the flame of the left flame port 20b and the right flame port 20c.

[0069] In particular, in the left passage 23b and the right passage 23c of the first embodiment, the opening area expands in a direction away from the central notch 22a as it goes from the side of the gas accumulation chamber 21 toward the outer peripheral side of the cylindrical wall 13a. As a result, the flames of the left flame port 20b and the right flame port 20c are formed to spread in a direction away from the fire support claw 4b opposite to the central flame port 20a in addition to being short-flamed. Therefore, it is possible to further suppress the baking of the claw caused by the flames of the left flame port 20b and the right flame port 20c.

[0070] Figure 7 It is an explanatory diagram showing the structure of the gas accumulation chamber 21 in the gas burner 10 of the second embodiment. In the figure, similar to Figure 4 (b) of, it shows the state of the portion of the cylindrical wall 13a of the burner head 13 opposite to the fire support claw 4b as viewed from below. The portion of the lower end surface of the cylindrical wall 13a that abuts against the mounting surface 11d is hatched, and the vertical surface 11e is shown by a dotted line. In addition, in the second embodiment, the description is centered on the points different from the above-described first embodiment, and for the structures similar to those of the first embodiment, the same reference numerals are given and the detailed description is omitted.

[0071] As shown in the figure, in the gas accumulation chamber 21 of the second embodiment at the lower end surface of the cylindrical wall 13a provided at the portion opposite to the fire support claw 4b, the thin wall portion 22d is not provided on the inner wall 21b, and accordingly, the rear communication portion 24 of the first embodiment is not formed. Instead, side notches 22e that connect the outside and the inside of the gas accumulation chamber 21 are provided on the side walls 21c on both sides of the gas accumulation chamber 21. And when the lower end surface of the cylindrical wall 13a abuts against the mounting surface 11d, a side communication portion 25 is defined by the side notches 22e and the mounting surface 11d. The side communication portion 25 communicates in the circumferential direction of the cylindrical wall 13a, and the mixed gas in the mixing chamber 11c flows into the gas accumulation chamber 21 through the side communication portion 25. In addition, the side communication portion 25 of the second embodiment corresponds to the "communication portion" of the present invention.

[0072] Figure 8 It is an explanatory diagram conceptually showing the flow of the mixed gas that flows into the gas accumulation chamber 21 from the side communication portion 25 and flows out from the fire support flame port 20 in the gas burner 10 of the second embodiment. The hollow arrows in the figure conceptually represent the flow of the mixed gas. In Figure 8shows the flow of the mixed gas when the gas burner 10 is at high heat. At high heat, there is a tendency that the mixed gas flows violently from the inner side to the outer side in the radial direction of the mixing chamber 11c, and it is difficult for the mixed gas to flow into the gas accumulation chamber 21 through the lateral communication part 25 that communicates in the circumferential direction. Also, the mixed gas flowing in the circumferential direction does not directly flow out from the three burner ports 20 (central burner port 20a, left burner port 20b, right burner port 20c) that open in the radial direction, but the mixed gas that has diffused temporarily in the gas accumulation chamber 21 is dispersed to the three burner ports 20. Therefore, it is possible to suppress the flow rate of the mixed gas flowing out from each of the three burner ports 20 and suppress the roasting claws. In addition, the effect obtained by the expansion of the lateral widths of the left notch 22b and the right notch 22c is the same as that of the aforementioned first embodiment.

[0073] On the other hand, in Figure 8 shows the flow of the mixed gas when the gas burner 10 is at low heat. At low heat, the mixed gas flows slowly from the inner side to the outer side in the radial direction of the mixing chamber 11c, so that the mixed gas easily flows into the gas accumulation chamber 21 through the lateral communication part 25 that communicates in the circumferential direction. Therefore, compared with high heat, the flow rate of the mixed gas flowing into the gas accumulation chamber 21 is not easily reduced, and a sufficient flow rate of the mixed gas flows to each of the three burner ports 20 to ensure the afterburning performance.

[0074] In addition, there are also the following modification examples in the gas burner 10 of the second embodiment. Figure 9 is an explanatory diagram showing the structure of the gas accumulation chamber 21 in the modified gas burner 10. In the gas accumulation chamber 21 of the modification example, side notches 22e are also provided on the side walls 21c on both sides in the same manner as in the second embodiment described above. However, the radial width of the cylindrical wall 13a of the side notch 22e in the modification example is not constant, and it widens toward the outer peripheral side of the cylindrical wall 13a as it goes from the outside to the inside of the gas accumulation chamber 21.

[0075] According to the widening of such a lateral notch 22e, the mixed gas flowing into the gas accumulation chamber 21 through the lateral communication portion 25 can be guided along the inner surface of the outer peripheral side of the cylindrical wall 13a at the lateral notch 22e (hereinafter referred to as the widened surface 22f) to the left passage 23b and the right passage 23c. As a result, at high heat, the flow rate of the mixed gas flowing out from the central flame port 20a facing the fire support claw 4b can be suppressed, and the roasting of the claw caused by the flame at the central flame port 20a can be suppressed. In addition, as described above, in the left flame port 20b and the right flame port 20c, due to the expansion of the opening area (the expansion of the lateral width of the left notch 22b and the right notch 22c), the flame becomes short, and thus, the roasting of the claw can be suppressed. On the other hand, at low heat, the outflow of the mixed gas from the left flame port 20b and the right flame port 20c where the flame becomes short can be promoted to ensure the afterburning performance.

[0076] As described above, the gas stove 1 of various embodiments and modification examples has been described. However, the present invention is not limited to the above-described embodiments and modification examples, and can be implemented in various forms without departing from the gist thereof.

[0077] For example, in the left passage 23b and the right passage 23c of the first embodiment described above, the opening area expands in a direction away from the central notch 22a as it goes from the gas accumulation chamber 21 side toward the outer peripheral side of the cylindrical wall 13a. However, the expansion direction of the opening area is not limited to this, and it can expand in a direction closer to the central notch 22a or upward. In addition, it can expand in any two of the three directions of away from the central notch 22a, closer to the central notch 22a, and upward, or can expand in all three directions. Due to these expansions, the short-flaming at the left flame port 20b and the right flame port 20c can also be achieved. However, if the opening area expands in a direction away from the central notch 22a as in the first embodiment described above, in addition to the short-flaming at the left flame port 20b and the right flame port 20c, the effect of moving the flame away from the fire support claw 4b can also be obtained.

[0078] In addition, in the gas accumulation chamber 21 of the first embodiment described above, the mixed gas flows into the gas accumulation chamber 21 through the rear communication portion 24, and in the gas accumulation chamber 21 of the second embodiment described above, the mixed gas flows into the gas accumulation chamber 21 through the lateral communication portion 25. However, the communication portion for flowing the mixed gas from the mixing chamber 11c into the gas accumulation chamber 21 is not limited to any one of them. As Figure 10 shown, both the rear communication portion 24 and the lateral communication portion 25 can be provided. In this case, especially at low heat, compared with the case where only one of the rear communication portion 24 and the lateral communication portion 25 is provided, the inflow of the mixed gas from the mixing chamber 11c into the gas accumulation chamber 21 is promoted, and thus, the improvement of the afterburning performance can be achieved.

Claims

1. A heating cooker, which uses a burner body and an annular burner head to form a gas burner, the burner body having an annular mixing chamber supplied with a mixed gas of fuel gas and air, the annular burner head being placed on the burner body to cover an upper surface opening of the mixing chamber, a lower end surface of a cylindrical wall vertically arranged in a cylindrical shape from an outer edge portion of the burner head toward the bottom is provided with a plurality of grooves transversely extending in a radial direction at intervals in the circumferential direction, and the upper surface opening of the mixing chamber of the burner body is provided with a plurality of grooves transversely extending in a radial direction at intervals in the circumferential direction. An annular mounting surface is provided around the gas burner. If the burner head is placed on the burner body and the lower end surface of the cylindrical wall abuts against the mounting surface, a plurality of flame ports that are connected to the mixing chamber and open on the outer periphery of the cylindrical wall are divided by the plurality of grooves and the mounting surface. The heating cooker burns the mixed gas flowing out of the flame ports to heat a cooking container placed on a fire support. The fire support has a plurality of fire support claws that are supported by an annular frame surrounding the gas burner and extend toward the top of the gas burner, and is characterized in that A concave gas storage chamber is provided on the lower end surface of the cylindrical wall at a position opposite to the fire support claw, and the gas storage chamber is surrounded by an outer wall, an inner wall and a radial side wall, the outer wall is formed along the outer periphery of the cylindrical wall, the inner wall is formed along the inner periphery of the cylindrical wall, and the radial side walls are formed on both sides separated by the outer wall and the inner wall. If the burner head is placed on the burner body, the lower surface opening of the gas storage chamber is closed by the placement surface. The outer wall is provided with three notches for connecting the outer periphery of the cylindrical wall with the gas storage chamber, including a central notch arranged in the center opposite to the fire support claw, and a left notch and a right notch arranged on both sides of the central notch. A communication portion for allowing the mixed gas to flow from the mixing chamber into the gas storage chamber is provided in a manner avoiding a position of the gas storage chamber that faces the central notch, and The opening areas of the left passage defined by the left notch and the placement surface and the right passage defined by the right notch and the placement surface on the outer peripheral side of the cylindrical wall are expanded relative to the opening areas on the gas storage chamber side.

2. The heating cooker according to claim 1, characterized in that: The opening areas of the left passage and the right passage expand in a direction away from the central notch as they move from the gas storage chamber side toward the outer peripheral side of the cylindrical wall.

3. The heating cooker according to claim 1, characterized in that: The heating cooker has a hanging surface vertically arranged downward from the inner edge of the placement surface. The communication portion is located between the vertical surface and the inner wall, and is formed on the left and right sides avoiding the central portion opposite to the central notch, and is communicated in the up-down direction.

4. The heating cooker according to any one of claims 1 to 3, characterized in that: The communication portion is formed on the side walls on both sides of the gas storage chamber and communicates with the cylindrical wall in a circumferential direction.

5. The heating cooker according to claim 4, characterized in that: The side walls on both sides of the gas storage chamber are provided with side notches connecting the outer side and the inner side of the gas storage chamber. The connecting portion is divided by the side notch and the mounting surface, The side notch expands toward the outer peripheral side of the cylindrical wall from the outside toward the inside of the gas storage chamber.

6. A gas burner, which is mounted on a heating cooker as a premise, the heating cooker heats a cooking container placed on a fire support, the fire support having a plurality of fire support claws supported by an annular frame, the gas burner comprising: a burner body having an annular mixing chamber supplied with a mixed gas of fuel gas and air; and an annular burner head mounted on the burner body to cover the upper surface opening of the mixing chamber, at the lower end surface of a cylindrical wall vertically arranged in a cylindrical shape from the outer edge portion of the burner head toward the bottom, A plurality of grooves extending transversely in the radial direction are recessed and spaced apart in the circumferential direction, and an annular mounting surface is provided around the upper surface opening of the mixing chamber of the burner body. When the burner head is placed on the burner body and the lower end surface of the cylindrical wall abuts against the mounting surface, a plurality of flame ports communicating with the mixing chamber and opening on the outer circumference of the cylindrical wall are divided by the plurality of grooves and the mounting surface. The gas burner burns the mixed gas flowing out of the flame ports, and is characterized in that: A concave gas storage chamber is provided on the lower end surface of the cylindrical wall at a position opposite to the fire support claw when the cooking device is mounted on the inner side of the frame, and the gas storage chamber is surrounded by an outer wall, an inner wall and radial side walls, the outer wall is formed along the outer circumference of the cylindrical wall, the inner wall is formed along the inner circumference of the cylindrical wall, and the radial side walls are formed on both sides separated by the outer wall and the inner wall. If the burner head is placed on the burner body, the lower surface opening of the gas storage chamber is closed by the placement surface. The outer wall is provided with three notches for connecting the outer periphery of the cylindrical wall with the gas storage chamber, including a central notch arranged in the center opposite to the fire support claw, and a left notch and a right notch arranged on both sides of the central notch. A communication portion for allowing the mixed gas to flow from the mixing chamber into the gas storage chamber is provided in a manner avoiding a position of the gas storage chamber that faces the central notch, and The opening areas of the left passage defined by the left notch and the placement surface and the right passage defined by the right notch and the placement surface on the outer peripheral side of the cylindrical wall are expanded relative to the opening areas on the gas storage chamber side.

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