Patent Publication Number: US-2022228743-A1

Title: Gas mixing device and gas water heating device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part and claims priority to U.S. patent application Ser. No. 17/136,541, filed on Dec. 29, 2020, which claims priority to Chinese Patent Application No. 202021208020.5, filed on Jun. 24, 2020, both of which are hereby incorporated by reference their entirety. This application also claims priority to Chinese Patent Application No. 20210412484.6, filed on Feb. 24, 2021, which is also hereby incorporated by reference its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to the field of gas mixing, in particular to a gas mixing device. 
     The present disclosure also relates to the field of water heating devices, in particular to a gas water heating device. 
     BACKGROUND 
     Fully premixed gas combustion refers to a combustion method in which gas is mixed with adequate air before entering the combustor, and no air is needed during the combustion. The flame propagation speed of fully premixed combustion is high, and the volumetric heat intensity of the combustion chamber is very high, generally up to 28˜56* 10 3 Kw/m 2  or higher. Complete combustion can be achieved at a small excess air coefficient, and there is almost no chemical incomplete combustion phenomenon. 
     In a fully premixed gas water heater, a Venturi premixing device is generally used to ensure full mixing of fuel gas and air, making the air flow velocity field uniform, thereby ensuring that the air flow velocity at each point of the combustor is greater than the flame propagation velocity under the lowest load. At the same time, the uniformity of the flame on the surface of the combustor is ensured, thus the flame on the surface of the combustor is prevented from being too long and contacting the surface of the heat exchanger to cause incomplete combustion. 
     However, in general, the Venturi tube of the current fully premixed gas water has a relatively small regulation ratio of no more than 1:10, thus the problem that the water temperature is too high under a low load still exists, which, especially in summer, will reduce the user experience. Moreover, there is also a problem of unstable flue gas emission during power regulation. 
     SUMMARY 
     In view of the above deficiencies, one purpose of the present disclosure is to provide a gas mixing device and a gas water heating device that can provide a higher regulation ratio, thereby solving the problem that the water temperature is too high in summer. 
     It is also an object of the present disclosure to provide a gas mixing device and a gas hot water device to be able to provide a higher adjustment ratio. 
     It is also an object of the present disclosure to provide a gas mixing device and a gas hot water device so as to be able to stabilize stable combustion in a state of low load. 
     Another purpose of the present disclosure is to provide a gas mixing device and a gas water heating device that can improve the stability of flue gas emission during power regulation. 
     To achieve the above purposes, the present disclosure adopts the following technical solutions: 
     A gas mixing device, comprising: 
     a shell provided with a fuel gas channel for inputting fuel gas, an air channel for inputting air and a gas mixing channel, the fuel gas channel being provided with a first cut-off portion capable of changing a flow area, and the air channel being provided with a second cut-off portion capable of changing a flow area; 
     a moving part movable in the shell, the moving part simultaneously changing the flow areas of the first cut-off portion and the second cut-off portions by moving. 
     In at least some embodiments, a movable contraction structure is provided in the shell; the air channel is located inside the contraction structure; the fuel gas channel is located outside the contraction structure; an internal flow area of the contraction structure gradually decreases in an air flow direction to form a contraction section; at least part of the internal flow area of the gas mixing channel gradually increases in an internal gas flow direction to form a diffusion section; and the fuel gas channel is communicated between the contraction section and the diffusion section. 
     In some embodiments, a ratio of a maximum flow area to a minimum flow area of the first cut-off portion is 10 to 30; and a ratio of a maximum flow area to a minimum flow area of the second cut-off portion is 2 to 6. 
     In some embodiments, the moving part moves linearly in the shell. 
     In some embodiments, the moving part comprises an air cut-off plug and a throat that is disposed to sleeve the air cut-off plug; the contraction structure is provided on the throat; an outer wall of the throat and an inner wall of the shell are provided with sealing structures slidable relative to each other; the sealing structures seal and separate the air channel and the fuel gas channel; the air channel is located inside the throat; and the fuel gas channel is located outside the throat. 
     In some embodiments, the shell is provided with a driving motor, which simultaneously drives the throat to move and drives the air cut-off plug to move relative to the throat, thereby simultaneously changing the flow areas of the first cut-off portion and the second cut-off portion. 
     In some embodiments, the shell is provided with a gas mixing tube forming the gas mixing channel; the first cut-off portion is formed between the throat and an end portion of the mixing tube; and the second cut-off portion is formed between the throat and the air cut-off plug. 
     In some embodiments, the air cut-off plug and the throat move synchronously in a predetermined transmission ratio. 
     In some embodiments, the throat is connected to the air cut-off plug or a motor shaft of the driving motor through a transmission mechanism; the driving motor directly drives the air cut-off plug to move, and the air cut-off plug or the motor shaft of the driving motor causes the throat to move through the transmission mechanism. 
     In some embodiments, the transmission mechanism is a linkage mechanism. 
     In some embodiments, the transmission mechanism comprises a first linkage and a second linkage which are rotatably connected through a pivot shaft; wherein one end of the first linkage is rotatably connected to the air cut-off plug or the motor shaft of the driving motor, and one end of the second linkage is rotatably connected to the throat. 
     In some embodiments, the driving motor is a linear motor; and the air cut-off plug is fixedly disposed to sleeve an output shaft of the linear motor. 
     In some embodiments, the shell is provided therein with a guide mechanism defining a moving path of the pivot shaft; and when moving in the moving path, the pivot shaft causes the throat to move linearly. 
     In some embodiments, the outer wall of the throat is provided with a first mating surface which participates in forming the first cut-off portion; the first mating surface has cambered surfaces with different radians in a moving direction of the throat; and the throat moves so that the cambered surfaces with different radians are respectively matched with the gas mixing tube to change the flow area of the first cut-off portion. 
     In some embodiments, an upper end of the air cut-off plug is provided with a second mating surface which participates in forming the second cut-off portion; the second mating surface has surfaces with different radians in a moving direction of the air cut-off plug; and the air cut-off plug moves so that surfaces with different radians are respectively matched with an inner wall of the throat to change the flow area of the second cut-off portion. 
     In some embodiments, the driving motor directly drives the throat and the air cut-off plug to move linearly. 
     In some embodiments, an output end of the driving motor is provided with a first driving gear and a second driving gear which are coaxially disposed; the air cut-off plug is driven by the driving motor through a first rack and the first driving gear to mesh; the throat is driven by the driving motor through a second rack and the second driving gear to mesh; and an addendum circle diameter of the first driving gear is smaller than that of the second driving gear. 
     In some embodiments, the shell is provided with a gas mixing tube forming the gas mixing channel; the moving part comprises an air cut-off plug and a throat that is disposed to sleeve the air cut-off plug; 
     the fuel gas channel is provided therein with a baffle plate; the baffle plate is provided with a flow hole which penetrates the baffle plate; the throat is fixedly provided with a shielding structure for shielding the flow hole; and the shielding structure moves to change a shielded area of the flow hole, so as to change the flow area of the first cut-off portion; 
     the air cut-off plug is fixedly provided with an air cut-off plate; the shell is provided with a variable-diameter portion; and the air cut-off plate and the variable-diameter portion move relative to each other to change the flow area of the second cut-off portion. 
     In at least some embodiments, a gas mixing device includes: 
     a shell, wherein the shell is provided with an air channel for conveying air, a fuel gas channel for conveying fuel gas, and a mixing-gas channel communicating with lower reaches of the air channel and the fuel gas channel, wherein the fuel gas channel comprises a first cut-off portion having a changeable flow area and the air channel comprises a second cut-off portion having a changeable flow area; and 
     a movable mechanism arranged in the shell, wherein the movable mechanism is provided with a flexible separation component which separates the air channel and the fuel gas channel, the movable mechanism penetrates through the flexible separation component and enters the air channel and the fuel gas channel and performs a motion to change the flow area of the first cut-off portion and the flow area of the second cut-off portion, and the flexible separation component is able to deform as the movable mechanism performs the motion. 
     In some embodiments, the movable mechanism performs a linear reciprocating motion. 
     In some embodiments, a part of the flexible separation component is stable, and another part of the flexible separation component moves along with the movement of the movable part. 
     In some embodiments, the shell is provided with a connection hole, through which the movable part penetrates, between the air channel and the fuel gas channel, and the flexible separation component is sleeved on the movable mechanism to shield and seal the connection hole. 
     In some embodiments, the air channel and the fuel gas channel have a shared wall, the connection hole is provided in the shared wall and penetrates through the shared wall, and the flexible separation component comprises a rubber membrane which is fixedly sleeved on the movable mechanism to shield and seal the connection hole. 
     In some embodiments, an outer periphery of the rubber membrane is fixed by clamping and an inner periphery of the rubber membrane onto the movable part. 
     In some embodiments, the movable mechanism comprises an air cut-off plate which is driven to move axially, a fuel gas valve core and a linkage rod, and the linkage rod connects with the air cut-off plate and the fuel gas valve core so as to link the fuel gas valve core and the air cut-off plate. 
     In some embodiments, the linkage rod and the fuel gas valve core are connected via a first elastic piece. 
     In some embodiments, an air valve port is provided in the air channel, the air cut-off plate has an air blocking position to block the air valve port, and in response to the air cut-off plate being located at the air blocking position, the gas-mixing device also includes a first connection portion which communicates the air channel located at lower reach of the air valve port with the air channel located at upper reach of the air valve port. 
     In some embodiments, the first connection portion comprises a first constantly open hole which is arranged in the air cut-off plate and penetrates through the air cut-off plate. 
     In some embodiments, the air valve port is located at a valve port step on an inner wall of the air channel, the valve port step is provided with a flange sealing ring, and the air cut-off plate, when located at the air blocking position, presses the flange sealing ring to hermetically blocks the air valve port. 
     In some embodiments, a fuel gas valve port is provided in the fuel gas channel, the fuel gas valve core has a fuel gas blocking position at which the fuel gas valve port is blocked, and in response to the fuel gas valve core being located at the fuel gas blocking position, the gas-mixing device also includes a second connection portion which communicates the fuel gas channel located at lower reach of the fuel gas valve port with the fuel gas channel located at upper reach of the fuel gas valve port. 
     In some embodiments, a fuel gas valve seat is provided in the fuel gas channel, and the fuel gas valve port and the second connection portion are both located on the fuel gas valve seat. 
     In some embodiments, the second connection portion comprises a second constantly open hole provided in the fuel gas valve seat, and the second constantly open hole is isolated from the fuel gas valve port. 
     In some embodiments, the fuel gas valve seat comprises a valve port end for the fuel gas valve port, the valve port end comprises a guiding surface that is concave towards the fuel gas valve port at a side away from the linkage rod, and the fuel gas valve core comprises a circumferential protruding periphery which is in contact with the guiding surface and covers and blocks the fuel gas valve port. 
     In some embodiments, a sealing ring is set to seal and block the fuel gas valve port at a side of the fuel gas valve core circumferential protruding periphery. 
     In some embodiments, a second elastic piece is provided in the fuel gas channel and the second elastic piece is configured to apply a force to the fuel gas valve core to cause the fuel gas valve core to move towards the blocking position. 
     In some embodiments, deformation of the second elastic piece when the second elastic piece presses and fixes the fuel gas valve core at the blocking position is adjustable. 
     In some embodiments, the valve port end of the fuel gas valve seat is further provided with a supporting holder, and the second elastic piece comprises a pressure spring having one end abutting against the supporting holder and another end abutting against the fuel gas valve core. 
     In some embodiments, the supporting holder accommodates a top hat which is able to move axially, and the pressure spring is compressed and limited between the top hat and the fuel gas valve core. 
     In some embodiments, the shell is provided with a screw-thread hole which stretches into the fuel gas channel and an adjustment screw which is in screw-thread fit with and penetrates through the screw-thread hole, an end of the adjustment screw abuts against a side of the top hat away from the pressure spring, and a length of a part of the adjustment screw, the part being screwed into screw-thread hole, is changeable by rotating the adjustment screw so as to change a position of the top hat in axial direction. 
     In some embodiments, the supporting holder comprises a first bulge which protrudes towards the fuel gas valve core, the fuel gas valve core comprises a second bulge which protrudes towards the first bulge, and two ends of the pressure spring are sleeved on the first bulge and the second bulge respectively. A gas water heating apparatus can include a gas-mixing device according to any of the above embodiments. 
     Advantageous effect: 
     The gas mixing device provided in some embodiments of the present disclosure simultaneously changes the flow areas of the first cut-off portion and the second cut-off portion by movement of the moving part, and simultaneously changes the input amount of fuel gas and of air while maintaining a mixing ratio between fuel gas and air to thereby change the amount of the mixed gas in the gas mixing channel. Therefore, the regulation ratio of the gas mixing device can be stably changed, and a stable flue gas emission can be achieved. 
     The movement of the gas mixing device provided in some embodiments of the present disclosure by the movement mechanism can simultaneously change the over-flow areas of the first and second shut-off portions, and change the input amounts of gas and air while maintaining the gas and air mixing ratio, thereby changing the mixed gas amount of the mixed gas passage, and in turn, the adjustment ratio of the gas mixing device can be stably changed, and the discharge of flue gas can be stabilized. 
     Also, the gas mixing device of at least some embodiments utilizes a flexible spacer component to space the gas passage and the air passage, and the flexible spacer component can be deformed together with the action of the moving mechanism to accommodate the action of the moving mechanism, thereby reducing interference and influence on the action of the moving mechanism, thereby simultaneously achieving precise control of the intake of gas and air. 
     Particular embodiments of the present disclosure are disclosed in detail with reference to the descriptions and figures in the following, and the ways in which the principle of the present disclosure can be employed are pointed out. It should be appreciated that the embodiments of the present disclosure are not limited in scope thereby. 
     Features which are described and/or indicated for one embodiment can be used in one or more other embodiments in an identical or similar way, can be combined with features in the other embodiments, or can replace the features in the other embodiments. It should be emphasized that the term “comprise/include”, when used in this text, refers to the presence of features, integers, steps or components, but does not exclude the presence or addition of one or more other features, integers, steps or components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to explain more clearly the technical solutions in the embodiments in the present disclosure or in the prior art, the following will briefly introduce the figures needed in the description of the embodiments or the prior art. Obviously, figures in the following description are only some embodiments of the present disclosure, and for a person skilled in the art, other figures may also be obtained based on these figures without paying any creative effort. 
         FIG. 1  is a structural diagram of a gas mixing device provided by an embodiment of the present disclosure; 
         FIG. 2  is a cutaway view of  FIG. 1 ; 
         FIG. 3  is a partial enlarged view of  FIG. 2 ; 
         FIG. 4  is a structural diagram of a gas mixing device provided by another embodiment of the present disclosure; 
         FIG. 5  is a cutaway view of  FIG. 4 ; 
         FIG. 6  is a structural cutaway view of a gas mixing device provided by another embodiment of the present disclosure. 
         FIG. 7  is a perspective view of a gas mixing device provided in another embodiment of the present disclosure; 
         FIG. 8  is a cross-sectional view of  FIG. 7 ; 
         FIG. 9  is an enlargement of Part I of  FIG. 8 ; 
         FIG. 10  is a perspective view of the gas valve seat and support bracket of  FIG. 7 ; 
         FIG. 11  is a schematic view of the gas valve seat of  FIG. 10 ; 
         FIG. 12  is a cross-sectional view of  FIG. 10 ; 
         FIG. 13  is a partial schematic view of the air shut-off plate of  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION 
     In order to enable persons skilled in the art to better understand the technical solutions in the present disclosure, a clear and comprehensive description to the technical solutions in the embodiments of the present disclosure will be given in the following in combination with the figures in the embodiments of the present disclosure, and obviously, the embodiments described are only part of the embodiments of the present disclosure, rather than all the embodiments of the present disclosure. Based on the embodiments of the present disclosure, all other embodiments obtained by ordinary skilled persons in this field without paying any creative effort should pertain to the scope of protection of the present disclosure. 
     What needs to be explained is that, when an element is referred to as being “provided on” another element, it can be directly on the other element, or an intervening element may also be present. When an element is considered to be “connected to” another element, it can be directly connected to the other element, or an intervening element may also be present. The terms “perpendicular”, “horizontal”, “left” and “right” as well as similar expressions used in this text are only for the purpose of explanation, and do not represent a unique embodiment. 
     Unless otherwise defined, all technical and scientific terms used in this text have the same meaning as commonly understood by persons pertaining to the technical field of the present disclosure. The terminology used in the description of the present invention is for the purpose of describing the specific embodiments only, and is not intended to limit the present disclosure. The term “and/or” used in the text includes any and all combinations of one or more of the associated listed items. 
     Referring to  FIGS. 1 and 2 , an embodiment of the present disclosure provides a gas mixing device, comprising: a shell  100 , and a moving part movable in the shell  100 , wherein, the shell  100  is provided with a fuel gas channel  200  for inputting fuel gas, an air channel  300  for inputting air and a gas mixing channel  400 . The fuel gas channel  200  is provided with a first cut-off portion  201  capable of changing a flow area, and the air channel  300  is provided with a second cut-off portion  301  capable of changing a flow area. The moving part simultaneously changes the flow areas of the first cut-off portion  201  and the second cut-off portion  301  by moving. 
     The gas mixing device provided by the present disclosure simultaneously changes the flow areas of the first cut-off portion  201  and the second cut-off portion  301  by movement of the moving part, and simultaneously changes the input amount of fuel gas and of air while maintaining a mixing ratio between fuel gas and air to thereby change the amount of the mixed gas in the gas mixing channel  400 . Therefore, the regulation ratio of the gas mixing device can be stably changed, and a stable flue gas emission can be achieved. 
     The gas mixing device of this embodiment coordinately changes the fan speed during the change of the regulation ratio, so that the flue gas is stable. High regulation ratio solves the problem that the water temperature is too high in summer. A higher regulation ratio can be realized, lower power can be achieved, a more stable low-load combustion can be maintained. 
     The gas mixing device of this embodiment is a Venturi tube of a special structure. The air channel  300 , the fuel gas channel  200  and the gas mixing channel  400  form the Venturi structure. Air flows through the air channel  300  towards the gas mixing channel  400 , generating a negative pressure which forms suction of the fuel gas in the fuel gas channel  200 . 
     To be specific, a movable contraction structure is provided in the shell  100 . The contraction structure is a conical structure as a whole. The air channel  300  is located inside the contraction structure. The fuel gas channel  200  is located outside the contraction structure. An internal flow area of the contraction structure gradually decreases in an air flow direction to form a contraction section. At least part of the internal flow area of the gas mixing channel  400  gradually increases in an internal gas flow direction to form a diffusion section, and a mixed gas outlet  103  is formed at the tail end of it. The fuel gas channel  200  is communicated between the contraction section and the diffusion section. Between the contraction section and the diffusion section may be a throat having a flow area that is substantially unchanged in the flow direction. The fuel gas channel  200  is in communication with the throat. 
     In this embodiment, the moving part may be a single element, and may also be assembled from a plurality of elements. The moving part may comprise a plurality of elements driven directly or indirectly by a driving motor  500 . The motion forms of the elements may be the same or different, and the present disclosure does not give limitations to this. The movement form of the moving part in the shell  100  may be rotation, translation and swing, and may even be a combination of a plurality of motions. In this embodiment, the moving part moves linearly in the shell  100 . The driving motor  500  has a motor shaft, the moving part can be mounted on the motor shaft, and the moving part can move in an axial direction. 
     To be specific, the moving part comprises an air cut-off plug  20  and a throat  10  that is disposed to sleeve the air cut-off plug  20 . The contraction structure is provided on the throat  10 . The contraction structure is a part of the throat  10 . The throat  10  can move to change the flow area of the first cut-off portion. The outer wall of the throat  10  and the inner wall of the shell  100  are provided with sealing structures slidable relative to each other. The sealing structures seal and separate the air channel  300  and the fuel gas channel  200 . The air channel  300  is located inside the throat  10 . The fuel gas channel  200  is located outside the throat  10 . The sealing structure may comprise a sealing ring  150  provided on the outer wall of the lower end of the throat  10 . The sealing ring  150  and the inner wall of the lower end of the upper shell  101  are fitted and sealed with each other. The throat  10  of a conical structure projects upwardly. 
     The shell  100  is provided with a gas mixing tube  30  forming the gas mixing channel  400 . The upper end  11  of the throat  10  extends into the gas mixing tube  30 . The throat  10  and the gas mixing tube  30  are coaxially provided. The first cut-off portion  201  is formed between the throat  10  and an end portion (the lower end) of the gas mixing tube  30 . The second cut-off portion  301  is formed between the throat  10  (the inner wall) and the air cut-off plug  20  (the upper end  21 ). The first cut-off portion  201  is located at any position of the fuel gas channel  200 , i.e. may be located at the tail end, entry end or even a middle position of the fuel gas channel  200 . In this embodiment, the first cut-off portion  201  is substantially located at the tail end of the fuel gas channel  200 , and fuel gas enters the gas mixing channel  400  after being discharged from the first cut-off portion  201 . The second cut-off portion  301  is substantially located at the tail end of the air channel  300 , and air enters the gas mixing channel  400  after being discharged from the second cut-off portion  301 . 
     As shown in  FIGS. 1 and 2 , the air channel  300  has an air inlet  105  that may be communicated with a silencer device. The shell  100  comprises an upper shell  101  and a lower shell  102 . The air inlet  105  is located at the lower end of the lower shell  102 . The lower end of the upper shell  101  and the upper end of the lower shell  102  are fixedly connected. An upper end cover  106  covers and seals the upper end of the upper shell  101 . The gas mixing tube  30  is coaxially provided on the upper end cover  106 , forming a mixed gas outlet  103  at the upper end thereof. The throat  10  is located in the shell  100  and moves approximately at the connection part between the upper shell  101  and the lower shell  102 . The throat  10  and the gas mixing tube  30  are provided to be coaxial. The fuel gas channel  200  is formed among the throat  10  and gas mixing tube  30  and the upper shell  101 , and is located outside the throat  10  and gas mixing tube  30 . 
     In this embodiment, the side wall of the upper shell  101  has a gas side tube  110 , which having a fuel gas inlet  104  for inputting fuel gas. The air channel  300  is located inside the throat  10 . When facing  FIG. 2 , the air channel  300  is located on the lower side of the throat  10 , and the fuel gas channel  200  and gas mixing channel  400  are located on the upper side of the throat  10 . 
     What needs to be explained is that the upward and downward orientations described in this embodiment are defined based on the orientation facing  FIG. 2 . In actual use, the installation and use of the gas mixing device is not limited to the state shown in  FIG. 2 . The gas mixing device does not have to be used in the state shown in  FIG. 2 . Correspondingly, the “upper end” and “lower end” described in this embodiment may also be changed adaptively. For example, when an actual gas mixing device is in a state opposite (installed inversely) to the state shown in  FIG. 2 , the “upper end” described in this embodiment becomes the “lower end”, and there is no such limitation that the “upper end” described in this embodiment must be the “top end” in use. 
     In this embodiment, the shell  100  is provided with a driving motor  500 . The driving motor  500  is fixedly mounted at the lower end of the shell  100 . The driving motor  500  simultaneously drives the throat  10  to move and drives the air cut-off plug  20  to move relative to the throat  10 , thereby simultaneously changing the flow areas of the first cut-off portion  201  and the second cut-off portion  301 . To be specific, the driving motor  500  can directly drive the air cut-off plug  20  to move and indirectly drive the throat  10  (e.g., the throat  10  can be caused to move by means of the air cut-off plug  20 ), and can also directly drive the throat  10  to move and indirectly drive the air cut-off plug  20  (e.g., the air cut-off plug  20  can be caused to move by means of the throat  10 ). Of course, the driving motor  500  can also directly drive the air cut-off plug  20  and the throat  10  simultaneously. 
     The motions of the air cut-off plug  20  and the throat  10  may be the same, i.e. they move synchronously and equidistantly. That is, the air cut-off plug  20  and the throat  10  have the same speed when doing linear movements, and the transmission ratio between the two is 1:1. In this embodiment, the air cut-off plug  20  and the throat  10  move synchronously in a predetermined transmission ratio. To be specific, considering the mixing ratio between air and fuel gas, the moving speed of the air cut-off plug  20  may be greater than that of the throat  10 . The change rate of the flow area of the first cut-off portion  201  may be greater than that of the second cut-off portion  301 . The linear movements of the air cut-off plug  20  and the throat  10  are not equal in speed. The air cut-off plug  20  and the throat  10  move upwardly or downwardly together at different speeds to maintain a certain mixing ratio between fuel gas and air, thereby ensuring the stability of combustion. 
     In this embodiment, in order to realize the linear movements of the air cut-off plug  20  and the throat  10 , the driving motor  500  can be a linear motor, and the air cut-off plug  20  is fixedly disposed to sleeve the output shaft (motor shaft) of the linear motor  500 . The air cut-off plug  20  can be mounted on the output shaft of the linear motor  500  to perform a linear movement together with the output shaft. The air cut-off plug  20 , when moving linearly, causes the throat  10  to move linearly as well. 
     In order to realize the movement of the throat  10 , the throat  10  is connected to the air cut-off plug  20  or the motor shaft of the driving motor by means of a transmission mechanism. The driving motor  500  directly drives the air cut-off plug  20  to move, and the air cut-off plug  20  or the motor shaft of the driving motor causes the throat  10  to move by means of the transmission mechanism. As shown in  FIG. 2 , the air cut-off plug  20  is fixedly disposed to sleeve the motor shaft of the linear motor  500 , and the air cut-off plug  20  is connected to the throat  10  by means of the transmission mechanism. The transmission mechanism is a linkage mechanism by means of which the movement of the air cut-off plug  20  is transmitted to the throat  10 , so that when the air cut-off plug  20  moves, it causes the throat  10  to move together with it, and the two maintain a predetermined transmission ratio. Hence, a certain mixing ratio between fuel gas and air is maintained, and the stability of combustion is ensured. 
     In this embodiment, the transmission mechanism is a linkage mechanism. To be specific, the transmission mechanism comprises a first linkage  41  and a second linkage  42  rotatably connected via a pivot shaft  43 . One end of the first linkage  41  is rotatably connected to the air cut-off plug  20 , and one end of the second linkage  42  is rotatably connected to the throat  10 . In this embodiment, one end of the first linkage  41  may also be directly and rotatably connected to the motor shaft of the driving motor  500 , in which case the throat  10  can also be caused to move by means of the transmission mechanism. 
     As can be seen in  FIG. 2 , in order to avoid interference on the moving path, the first linkage  41  and the second linkage  42  are curved or micro-bent structures. Of course, in other embodiments, the first linkage  41  and the second linkage  42  can also be straight rods, and the present disclosure does not make a unique limitation. The two ends of the first linkage  41  are respectively hinged to the lower end of the air cut-off plug  20  and one end of the second linkage  42 , and the other end of the second linkage  42  is hinged to the lower end of the throat  10 . In order to facilitate connection and assembly, the lower end of the throat  10  can extend to form a connection section to be hinged with an end of the second linkage  42 . Of course, an end of the second linkage  42  can also be directly hinged with the main body of the throat  10 . It can be seen that the transmission mechanism in this embodiment has a simple structure, is easy to assemble and has a low manufacture cost. Moreover, it can keep the throat  10  and air cut-off plug  20  in transmission with a predetermined transmission ratio. An appropriate mixing ratio between fuel gas and air can be maintained while realizing a synchronized movement of the two. 
     In order to ensure a stable change of the flow areas of the first cut-off portion  201  and the second cut-off portion  301 , the shell  100  is provided with a guide structure  50  for guiding the movement of the moving part, enabling the moving part to move stably, thereby changing the combustion power stably. To be specific, the guide structure  50  can guide one of the air cut-off plug  20  and the throat  10 . In this embodiment, the guide structure  50  is provided on the gas mixing tube  30 . The guide structure  50  comprises a guide rod provided on the gas mixing tube  30 . The guide rod and the gas mixing tube  30  are coaxially provided. The upper end of the air cut-off plug  20  is disposed to sleeve the guide rod and slidable relative to the guide rod. When the air cut-off plug  20  performs a linear movement (e.g., the up-down movement shown in  FIG. 2 ), the length of the guide rod extending into the air cut-off plug  20  changes, but the guide rod remains extending into the air cut-off plug  20 . Therefore, guiding for the movement of the air cut-off plug  20  is maintained. Of course, the movement of the throat  10  can also be guide by the slidable sealing between the throat  10  and the shell  100 . 
     In this embodiment, the shell  100  is provided therein with a guide mechanism  60  defining a moving path of the pivot shaft  43 . When moving in the moving path, the pivot shaft  43  causes the throat  10  to move linearly. As shown in  FIG. 2 , the guide mechanism  60  is a guide groove fixed on the inner wall of the lower shell  102 . The guide groove is disposed obliquely. The end of it close to the air cut-off plug  20  is the upper end, and the end of it away from the air cut-off plug  20  is the lower end. The guide groove is a linear groove. When the air cut-off plug  20  moves downwardly, the pivot shaft  43  moves towards the lower right side (based on the orientation facing FIG.  2 ) along the guide mechanism (guide groove), and when the air cut-off plug  20  moves upwardly, the pivot  43  moves towards the upper left side. 
     In this embodiment, the first cut-off portion  201  is the part of the whole fuel gas channel  200  which has the minimum flow area. By changing the size of the flow area of the first cut-off portion  201 , the adjustment of the fuel gas supply amount of the fuel gas channel  200  is realized. Correspondingly, the second cut-off portion  301  is the part of the whole air channel  300  which has the minimum flow area. By changing the size of the flow area of the second cut-off portion  301 , the adjustment of the air supply amount of the air channel  300  is realized. 
     To achieve a greater regulation ratio, the ratio of the maximum flow area to the minimum flow area of the first cut-off portion  201  is 10 to 30. For example, the ratio of the maximum flow area to the minimum flow area of the first cut-off portion  201  is around  20 . The ratio of the maximum flow area to the minimum flow area of the second cut-off portion  301  is 2 to 6. For example, the ratio of the maximum flow area to the minimum flow area of the second cut-off portion  301  is around 4. The regulation ratio of the gas mixing device provided in  FIGS. 1 and 2  can reach 1:20 or above. To be more specific, the regulation ratio of the gas mixing device can reach 1:22, and the gas mixing device can have a lower combustion power and a more stable regulation process, and thereby allows the flue gas emission to be stable and not easy to exceed certain standards during combustion power regulation. 
     In this embodiment, the air cut-off plug  20  and the throat  10  are designed to have gradually varied radians, and the regulation ratio of the gas mixing device (Venturi tube) is changed through the radians to achieve a relative large regulation ratio is achieved. Referring to  FIGS. 2 and 3 , the outer wall of the throat  10  is provided with a first mating surface  12  which participates in forming the first cut-off portion  201 . The first mating surface  12  has cambered surfaces with different radians in a moving direction of the throat  10 . The throat  10  moves so that cambered surfaces with different radians are respectively matched with the gas mixing tube  30  to change the flow area of the first cut-off portion  201 . 
     In this embodiment, the first mating surface  12  is disposed on the outer wall of the upper end  11  of the throat  10 , and the upper end  11  of the throat  10  extends into the lower end of the gas mixing tube  30 . The first cut-off portion  201  is formed between the first mating surface  12  and the inner wall of the lower end of the gas mixing tube  30 . The first mating surface  12  can be approximately three cambered surfaces of different radians. The cambered surface in the middle projects outwardly, and a smooth transition exist between the cambered surfaces on two sides and the cambered surface in the middle, so that a smooth regulation of the regulation ratio is realized. 
     The upper end of the air cut-off plug  20  is provided with a second mating surface  22  which participates in forming the second cut-off portion  301 . The second mating surface  22  has cambered surfaces with different radians in a moving direction of the air cut-off plug  20 . The air cut-off plug  20  moves so that cambered surfaces with different radians are respectively matched with the inner wall of the throat  10  to change the flow area of the second cut-off portion  301 . The second cut-off portion  301  is formed between the second mating surface  22  and the inner wall of the throat  10 . Referring to  FIGS. 2 and 3 , the upper end of the air cut-off plug  20  is approximately a diamond structure, the second mating surface  22  also includes approximately three cambered surfaces  221 ,  222 ,  223  of different radians, wherein the cambered surface  221  in the middle as a whole is a conical surface, and in fact is a cambered surface with a relative large radian. 
     In other embodiments, the driving motor  500  can directly drive the throat  10  and the air cut-off plug  20  to move linearly. No transmission mechanism is required between the throat  10  and the air cut-off plug  20 , and the motions of the two are the same. The throat  10  and the air cut-off plug  20  can both be fixedly connected to the output shaft of the driving motor  500  directly, or can be respectively driven by the output shaft, or the throat  10  and the air cut-off plug  20  can be fixedly connected to each other with one of them being directly driven by the output shaft of the driving motor  500 , so that they are driven together. 
     In addition, in other embodiments, the transmission mechanism is not limited to a linkage mechanism. For example, the transmission mechanism may also be a worm gear and worm rod, a gear and chain, belt transmission and so on. 
     In a feasible embodiment as shown in  FIG. 6 , the driving motor  500  directly drives the throat  10  and the air cut-off plug  20 . The output end of the driving motor  500  is provided with a first driving gear  510  and a second driving gear  520  which are coaxially disposed. The air cut-off plug  20  is driven by the driving motor  500  through a first rack  260  and the first driving gear  510  to mesh. The throat  10  is driven by the driving motor  500  through a second rack  160  and the second driving gear  520  to mesh. 
     The addendum circle diameter of the first driving gear  510  is smaller than that of the second driving gear  520 . The screw pitches of the first drive gear  510  and the second drive gear  520  are different. In this embodiment, the above linkage mechanism is changed to be the gear and rack with different screw pitches in this embodiment to realize a synchronous and coaxial linear motion of air and fuel gas at different distances. 
     For the air cut-off plug  20 , throat  10  and gas mixing tube  30  in this embodiment, reference can be made to the description in the embodiment of  FIGS. 1 and 2 , and no redundant depiction will be given in this embodiment. 
     In another specific embodiment, as can be seen from  FIGS. 4 and 5 , the shell  100  is provided with a gas mixing tube  30 ′ forming the gas mixing channel  400 . The moving part comprises an air cut-off plug  20 ′ and a throat  10 ′ that is disposed to sleeve the air cut-off plug  20 ′. The upper end of the throat  10 ′ is cylindrical. The upper end of the cylinder always extends into the gas mixing pipe  30 ′ during the movement of the throat  10 ′, thus the flow area there is namely the cross sectional area of the annular space between the cylindrical upper end and the gas mixing tube  30 ′. Besides, the flow area between the throat  10 ′ and gas mixing tube  30 ′ remains unchanged during the movement of the throat  10 ′. 
     A baffle plate  111  is provided in the fuel gas channel  200 . The baffle plate  111  is provided with a flow hole  112  which penetrates the baffle plate. The flow area (the cross sectional area) between the throat  10 ′ and the gas mixing tube  30 ′ is greater than the flow area of the first cut-off portion  201 . Preferably, the flow area between the throat  10 ′ and the gas mixing tube  30 ′ is greater than the area of the flow hole  112  which is not shielded (the maximum flow area of the first cut-off portion  201 ). The side wall of the upper shell  101  has a fuel gas side tube  110 , the baffle plate  111  is located at the tail end of the fuel gas side tube  110 , and fuel gas passes through the flow hole  112  of the baffle plate  111  and enter the inner cavity of the upper shell  101  (the annulus space between the inner wall of the shell  101  and the gas mixing tube  30 ′). The overall fuel gas side tube  110  is perpendicular to the gas mixing tube  30 ′, and the flow hole  112  faces towards the side wall of the gas mixing tube  30 ′. 
     To be specific, the communication area of the flow hole  112  is namely the flow area of the first cut-off portion  201 . The baffle plate  111  may be a porous wall surface structure, the flow hole  112  comprises a plurality of air holes distributed on the baffle plate  111 , which can be arranged to be an approximately triangular structure, and the number of the air holes increases gradually from top to bottom. Of course, in other embodiments, the flow hole may be a single triangular hole, so that the flow area of the first cut-off portion  201  can be smoothly changed. 
     The throat  10 ′ is fixedly provided with a shielding structure  15  for shielding the flow hole  112 . The shielding structure  15  moves to change a shielded area of the flow hole  112 , so as to change the flow area of the first cut-off portion  201 . The shielding structure  15  changes the number of the shielded air holes to change the communication area of the flow hole  112 , and thus the flow area of the first cut-off portion  201  can be changed. The shielding structure  15  is disposed on the outer side wall of the throat  10 ′ and is provided with fuel gas cut-off cotton  151 , and thus has a better sealing effect when being attached to the inner wall surface of the baffle plate  111 , so that fuel gas can pass through the part of the flow hole  112  which is not shielded. 
     The air cut-off plug  20 ′ is fixedly provided with an air cut-off plate  25 . The shell  100  is provided with a variable-diameter portion  102 ′. The variable-diameter portion  102 ′ is located on the lower shell  102 . In this embodiment, the internal cross sectional area (flow area) of the variable-diameter portion  102 ′ decreases gradually in the air flow direction. When the inner cavity cross section of the lower shell  102  is circular, the internal diameter of the variable-diameter portion  102 ′ decreases gradually in the air flow direction. The air cut-off plate  25  and the variable-diameter portion move relative to each other to change the flow area of the second cut-off portion  301 . 
     To be specific, the upper end of the air cut-off plug  20 ′ does not need to have the structure shown in  FIGS. 1 and 2 , and the air cut-off plug  20 ′ can be a cylindrical structure as a whole. The flow area between the air cut-off plug  20 ′ and the inner wall of the throat  10 ′ is always greater than the flow area between the air cut-off plate  25  and the variable-diameter portion  102 ′. Hence, the second cut-off portion  301  is formed between the air cut-off plate  25  and the variable-diameter portion  102 ′, and the change of the flow area between the air cut-off plate  25  and the variable-diameter portion  102 ′ can affect the amount of air. The air cut-off plate  25  is fixedly connected to the lower end of the air cut-off plug  20 ′. The relative position of the air cut-off plate  25  in the variable-diameter portion  102 ′ is changed by the axial movement (linear movement or up and down movement) of the air cut-off plate  25 , and accordingly the flow area of the annular channel between the air cut-off plate and the variable-diameter portion  102 ′ is changed corresponding to parts of the variable-diameter portion  102 ′ that have different cross sectional areas. 
     In this embodiment, the throat  10 ′, the air cut-off plate  25  and the air cut-off plug  20 ′ are assembled into one piece and move coaxially, synchronously and equidistantly with the motor  500  as the (linear) motor  500  extends and contracts. 
     Based on the same idea, the embodiments of the present disclosure also provide a gas water heating device as described in the following embodiments. Since the principles by which the gas water heating device solves problems and the technical effects which the gas water heating device can achieve are similar to that of the gas mixing device. Reference can be made to the implementation of the gas mixing device described above for the implementation of the gas water heating device. No redundant depiction will be given for the repeated content. 
     A further embodiment of the present disclosure provides a gas water heating device comprising the gas mixing device according to any one of the above embodiments. The gas mixing device can be communicated upstream of the combustor of the gas water heating device for providing premixed gas to the combustor and providing fuel gas to the combustor. The gas water heating device is preferably a fully premixed gas water heater. 
     Referring now to  FIGS. 7 to 13 , a gas mixing device is provided that includes a housing  1100 , a movement mechanism  1001  disposed within said housing  1100 . Said housing  1100  is provided with an air passage  1010  for conveying air, a gas passage  1020  for conveying gas, a mixed gas passage  1030  communicating downstream of said air passage  1010  and said gas passage  1020 ; said gas passage  1020  has a first shut-off portion  1011  which can be changed over flow area; and said air passage  1010  has a second shut-off portion  1021  which can be changed over flow area. 
     Said moving mechanism  1001  is provided with a flexible spacing member sealing said air passage  1010  and said gas passage  1020 . Said moving mechanism  1001  opens into said air passage  1010  and said gas passage  1020  through said flexible spacer component and changes said first and second shut-offs  1011 ,  1021  through an action; said flexible spacer component is deformable with the action of said moving mechanism  1001 . 
     The movement of the gas mixing device provided by the present embodiment by the movement mechanism  1001  can simultaneously change the over-flow areas of the first and second shut-off portions  1011 ,  1021 , and change the input amounts of gas and air while maintaining the gas and air mixing ratio, thereby changing the mixed gas amount of the mixed gas passage  1030 , and in turn, the adjustment ratio of the gas mixing device can be stably changed, and the discharge of flue gas can be stabilized. 
     Also, the gas mixing device of the present embodiment utilizes a flexible spacer component to space the gas passage  1020  and the air passage  1010 , and the flexible spacer component can be deformed together with the action of the moving mechanism  1001  to accommodate the action of the moving mechanism  1001 , thereby reducing interference with the action of the moving mechanism  1001  for the purpose of precisely controlling the intake air of gas and air. 
     The gas mixing device provided by the present embodiment has a greater regulation ratio, which in turn can achieve lower power, maintaining more stable low-load combustion. 
     The gas mixing device of the present embodiment is a venturi pipe of special construction. Wherein the air channel  1010 , the gas channel  1020  and the mixed gas channel  1030  form a venturi structure. Air flows through the air channel  1010  to the mixed gas channel  1030  and creates a negative pressure draws gas in the gas channel  1020 . 
     In the present embodiment, the first shut-off portion  1011  is the location where the overall gas channel  1020  has the smallest excess flow area, and by changing the size of the overflow area of the first shut-off portion  1011 , an adjustment of how much gas is supplied to the gas channel  1020  is achieved. Accordingly, the second shut-off portion  1021  is the location where the throughflow area of the entire air passage  1010  is minimal, and by changing the throughflow area of the second shut-off portion  1021 , an adjustment of how much air is supplied to the air passage  1010  is achieved. 
     The motor  1200  can project into the air channel  1010  through an air inlet  1101  at the lower end of the housing  1100 . The motor  1200  may directly drive the movement mechanism  1001  for movement. The output shaft of the motor  1200  and the linkage rod  1013  are arranged coaxially, and the linkage rod  1013  is arranged coaxially fixedly outside the output shaft of the motor  1200 . The air shut-off plate  1012  is fixedly sleeved outside the linkage rod  1013  to move synchronously with the linkage rod  1013 . 
     Within the housing  1100  there is provided a conical tube structure forming a constricted section  1040  of the venturi structure. Wherein the gas channel  1020  is located outside the constricted section  1040 . Negative pressure is created through the throat section  1050  after being accelerated by the constricted section  1040 , drawing gas in the gas channel  1020 . 
     The gas mixing device of the present embodiment achieves an adjustment of the mixing ratio of air and gas through movement of the moving mechanism  1001 , and in cooperation with a change in the fan rotation speed, so that combustion is stable. The internal over-flow area of at least part of the length of the mixed gas channel  1030  gradually increases along its internal gas flow direction, forming a diffuser section of the venturi structure. Between the diffuser section and the constricted section  1040  the over-flow area flows in a substantially constant throat section  1050 . A gas passage  1020  communicates with the throat section  1050 . The end of the mixed gas passage  1030  forms a gas outlet  1103 . 
     In the present embodiment, the movement mechanism  1001  may be a single element, or may be assembled and formed for multiple elements. The movement mechanism  1001  may be driven directly or indirectly by the motor  1200 . The form of movement of the movement mechanism  1001  in the housing  1100  may be rotation, translation, rocking, or even a combination of actions. In the present embodiment, the movement mechanism  1001  reciprocates linearly. The motor  1200  has a motor  1200  shaft, on which motor  1200  shaft a movement mechanism  1001  can be mounted, moving axially. 
     In the present embodiment, the flexible spacer component is fixedly provided on the housing  1100  and fixedly connected to the moving mechanism  1001 . The flexible spacer component is a flexible material, for example a rubber material. Part of the flexible spacer component is immobilized and part of the flexible spacer component moves with the action of the moving mechanism  1001 . The flexible spacer component is fixedly connected between the moving mechanism  1001  and the housing  1100 , spacing the air channel  1010  and the gas channel  1020 . The connection portion to which the flexible spacer component is fixedly connected to the movement mechanism  1001  acts (moves) with the movement mechanism  1001 , the flexible spacer component deforms to accommodate the action of the movement mechanism  1001  and maintains a sealed spacing between the air passage  1010  and the gas passage  1020 . 
     Specifically, said housing  1100  is provided with a communication hole  1151  between said air passage  1010  and said gas passage  1020  traversed by said moving mechanism  1001 . The flexible spacer part is fixedly sleeved outside the moving mechanism  1001  occludes the communication hole  1151 . 
     Said air channel  1010  and said gas channel  1020  have a common channel wall  1150 . Said communication hole  1151  is provided on said channel wall  1150  through said channel wall  1150 . The flexible spacer component comprises a skin  1018  that is fixedly sleeved outside the moving mechanism  1001  to hide the communication hole  1151 . The outer edge  1181  of said skin  1018  is clip-fixed; the inner edge  1182  of said skin  1018  is fixed to said movement mechanism  1001 , moving linearly and reciprocally following the movement mechanism  1001 . 
     In the present embodiment, said movement mechanism  1001  comprises an air shut-off plate  1012  driven to move axially, a gas spool  1002 , and a linkage rod  1013 . Said linkage rod  1013  connects said air shut-off plate  1012  and gas spool  1002 , linking said gas spool  1002  with said air shut-off plate  1012 . 
     When the linkage rod  1013  rigidly connects the air shut-off plate  1012  and the gas spool  1002  (e. g., in the form of screwing, welding, bolting, etc.), it is difficult to ensure that the air shut-off plate  1012  and the gas spool  1002  reach the blocking position accurately at the same time, e. g., on the basis that the gas spool  1002  first reaches the blocking position cannot continue to descend, if the air shut-off plate  1012  is not reset to its blocking position, and the hard connection between the air shut-off plate  1012  and the gas spool  1002  is hard, the length of the two cannot be adjusted, the air shut-off plate  1012  cannot continue to descend, so that a seal is difficult to form, and the air fuel ratio is difficult to accurately adjust. 
     Based on this consideration, the linkage rod  1013  and the gas spool  1002  are connected between the first elastic member. As shown in  FIG. 9 , the upper end of linkage rod  1013  is a receiving groove. The first elastic member is a (cylindrical) connecting spring  1016 . The lower end of the connecting spring is located in the accommodating slot and fixedly sleeved over the positioning post within the accommodating slot. The upper end of the connection spring is fixedly sleeved outside the connection projection of the connecting end  1119  (lower end) of the gas spool  1002 , so that the connection spring soft-connects the linkage rod  1013  and the gas spool  1002 , so that both the air shut-off plate  1012  and the gas spool  1002  can reach the blocking position accurately to seal the respective valve ports. The first elastic member is in a stretched state when the air shut-off plate  1012  and the gas spool  1002  are in the blocked position. 
     In this embodiment, the second shutoff  1021  is located upstream of the constricted section  1040 . Said air passage  1010  has an air valve opening therein. A second shutoff  1021  is formed between the air shut-off plate  1012  and the air valve opening. The air shut-off plate  1012  has an air blocking position that blocks the air valve. The housing  1100  is provided with a reduction located at the channel wall  1150  of the air channel  1010 . The reduction portion defines an air valve opening. The air passage  1010  is provided with an air inlet port  1101  upstream of the air valve port. In the present embodiment, the internal cross sectional area of the reducing portion gradually decreases along the air flow direction. When the cross section of the air passage  1010  is circular, the internal diameter of the reducing portion gradually decreases along the air flow direction. The air shut-off plate  1012  and the reduction part are reciprocated by an axial straight line to vary the over-flow area of the second shut-off part  1021 . 
     When the air shut-off plate  1012  is in the air blocking position, the gas mixing device is further provided with a first communication connecting an air passage  1010  located downstream of the air valve with an air passage  1010  located upstream of the air valve. Specifically, said first communication portion comprises a first always through hole  1121  located on said air shut-off plate  1012  and passing said air shut-off plate  1012  through. Of course, in other embodiments, the first communication portion may also be a clearance structure of the outer edge  1181  of the air shut-off plate  1012 , as the present embodiment is not the only embodiment contemplated by the inventors. By providing the first communication portion, the air shut-off plate  1012  can precisely control the small-load air-fuel ratio, reduce the minimum load and reach a high adjustment ratio. 
     A gas valve port  2110  is provided in said gas channel  1020 . Said gas spool  1002  has a gas blocking position blocking said gas valve port  2110 . When said gas spool  1002  is in said gas blocking position, said gas mixing device is further provided with a second communication portion connecting a gas passage  1020  located downstream of said gas port  2110  with a gas passage  1020  located upstream of said gas port  2110 . 
     In other embodiments, the second communication may even be provided on the gas spool  1002 , said gas spool  1002  moving axially reciprocally to change the over-flow area with said gas valve port  2110 . 
     A gas valve seat  1111  is provided in said gas channel  1020 . The gas valve seat  1111  defines a gas valve port  2110 . The gas channel  1020  has a gas inlet  1102  located upstream of the gas valve  2110 . A first shut-off portion  1011  is defined between the gas spool  1002  and the gas port  2110 . Specifically, the upper end of the gas valve core  1002  is a mating end  1118  cooperating with the gas valve port  2110 , and the other end is a connecting end  1119  (soft) connected with the linkage rod  1013 . The mating end  1118  of the gas spool  1002  is of gradual arc design. Adjusting the size of the overflow area between the (first shut-off portion  1011 ) gas port  2110  during linear reciprocating movement is accomplished by changing the arc of the outer wall face and the gas port  2110 , thereby changing the input amount of gas, thereby achieving a larger adjustment ratio. 
     For mounting the gas valve seat  1111 , a raised step is also provided within the gas channel  1020 . The gas valve seat  1111  is mounted between the raised step and the common channel wall  1150 , clip-mounted and fixed. Said gas valve port  2110  and said second communication are located on said gas valve seat  1111 . Said second communication comprises a second always through hole  2112  located on said gas valve seat  1111 . Said second always through hole  2112  is spaced apart from said gas port  2110 . When the gas valve core  1002  is in the blocking position, the first normal through hole  1121  is not blocked by the gas valve core  1002 , maintaining communication between the gas valve seat  1111  up and down under a small load, maintaining stable combustion under a small load. 
     In other embodiments, the second communication portion may be a vent structure located at an edge of the gas valve port  2110  and is not spaced apart from the gas valve port  2110 . Of course, the second communication may also be provided on other components, and not limited to on the gas valve seat  1111 . The second connection portion may be, for example, a through-hole that penetrates upstream and downstream of the partition within a gas channel  1020 , which simultaneously communicates upstream and downstream of the gas valve seat  1111 . 
     Under a small load, the gas mixing device moves the air shut-off plate  1012  and the gas spool  1002  to a blocking position (which may be an initial position of the air shut-off plate  1012  and the gas spool  1002 ), so as to realize an input supply of air and gas through the first communication portion and the second communication portion, and since the first communication portion and the second communication portion are always on disposed, the flow area is constant, so that stable supply of air and gas can be performed under a small load, and stable combustion under a small load is achieved. 
     In this embodiment, said gas valve seat  1111  has a valve port end  2115  of said gas valve port  2110 . The lower end of the gas valve seat  1111  is a venting end, which is located above the communication hole  1151  shielded from the skin  1018 , and protrudes downwardly by the connecting end  1119  of the valve core. The sidewall of the gas valve seat  1111  is provided with a sidewall hole  2113 , which opens into the interior of the gas valve seat  1111 , and communicates with the gas valve port  2110 , so as to realize communication between the upstream and downstream of the gas valve seat  1111 . The side of said valve port end  2115  remote from said linkage rod  1013  has a guide surface  2111  recessed towards said gas port  2110 . The guide surface  2111  is a concave tapered structure. By providing the tapered guiding surface  2111 , it is possible to keep the gas valve core  1002  centered when reset, avoiding tilting of the gas valve core  1002  after reset, and affecting precise control of the intake amount of gas air. 
     In order to form a good seal in the blocking position, precise control of the minimum load is carried out with the first communication and the second communication, said air valve being located at a valve port step  1110  on the inner wall of said air passage  1010 . A flange seal ring  2101  is provided on said valve port step  1110 . Compression of the flange seal ring  2101  when the air shut-off plate  1012  is in the air blocking position seals off the air valve. 
     Further, said gas spool  1002  has a circumferential flange  2181  thereon that can be brought into contact with said guide surface  2111  to cap and seal said gas port  2110 . Said gas spool  1002  is fixedly sleeved on one side of said circumferential flange  2181  with a sealing ring  2182  for sealing off said gas valve port  2110 . The sealing ring  2182  is compressed between the circumferential flange  2181  and the guide surface  2111  when the gas spool  1002  is in the gas blocking position, sealing the gas valve port  2110  against leakage. 
     A second elastic member for applying a force to the gas spool  1002  moving towards the blocking position is also provided within the gas passage  1020 . The second elastic member may apply a downward pressing force to the gas valve core  1002 , with which it is not only possible to maintain a seal when the gas valve core  1002  is in the blocked position, but also to eliminate dimensional differences resulting from various component parts of the movement mechanism  1001  and the overall assembly, which are compensated for by elongation or shortening of the second elastic member. 
     In particular, the valve port end  2115  of said gas valve seat  1111  is also provided with a support bracket  1112 . The support bracket  1112  is fixedly mounted at an upper end of the gas valve seat  1111  (valve port end  2115 ). The lower end of the support bracket  1112  is sheathed within an upwardly projecting ledge of the valve port end  2115  and has a sealing ring between the channel wall  1150 . Said second elastic member comprises a compression spring  1113  abutting one end against said support bracket  1112  on the other end against said gas valve core  1002 . The top of the support bracket  1112  has a mounting through-hole  2122 , the mounting through-hole  2122  is a stepped hole, and the overcap  1116  is slidably received within the mounting through-hole  2122 , and limits the uppermost position of the overcap  1116  by a limiting step within the mounting through-hole  2122 . 
     In the present embodiment, the deformation variable when said second elastic member compresses said gas spool  1002  in said blocking position is adjustable. An overcap  1116  capable of changing position axially is accommodated on said support bracket  1112 . Said compression spring  1113  is compression limited between said overcap  1116  and said gas spool  1002 . 
     Specifically, said housing  1100  is provided with a threaded hole leading into said gas passage  1020 , and a screw-fitting adjusting screw  1114  penetrating into said threaded hole. One end of said adjusting screw  1114  abuts on the side of said overcap  1116  remote from said compression spring  1113 . The adjustment screw  1114  and the compression spring  1113  are located on the upper and lower sides of the overcap  1116 , respectively, and the compression spring  1113  abuts the overcap  1116  upward, and the lower end of the adjustment screw  1114  abuts the overcap  1116  downward, limiting the overcap  1116 . A threaded through hole is located at the top of the housing  1100  and penetrates the channel wall  1150  of the gas channel  1020 . Sealing measures, such as sealing rings, are also provided between the upper end of the adjusting screw  1114  and the housing  1100  to avoid gas leakage. 
     Further, to guide the movement of the gas valve core  1002 , a guide rod  1115  is also fixed at an upper end of the gas valve core  1002 . The upper end of the guide rod  1115  projects into a guide groove of the side of the overcap  1116  facing away from the adjusting screw  1114 , and axially moves with the gas valve core  1002  relative to the overcap  1116 , thereby guiding the movement of the gas valve core  1002 . 
     As shown in  FIGS. 9 and 12 , the adjusting screw  1114  and the threaded bore threadingly cooperate, and said adjusting screw  1114  can be rotated to change the length of the screw into said threaded bore, thereby pushing the position of said overcap  1116  in the axial direction to change. Wherein, by screwing inwardly or outwardly by a certain length, the adjusting screw  1114  can change the projecting length into the gas passage  1020  by fitting the threaded hole, thereby pushing the overcap  1116  downward or moving the overcap  1116  upward, changing the axial position of the overcap  1116 , thereby changing the initial form variable (compression amount) of the compression spring  1113 , eliminating dimensional differences resulting from the overall assembly of the component parts of the movement mechanism  1001  and the gas mixing device. 
     In order to avoid exceeding the elastic limit of the compression spring  1113 , ensuring precise regulation of the gas air input amount and avoiding affecting the service life of the device, said support bracket  1112  has a first protrusion  2121  protruding towards said gas spool  1002 . The first protrusion  2121  is located on the overcap  1116  (the overcap  1116  is mounted in the mounting through-hole  2122  at the upper end of the support bracket  1112 , and in turn the first protrusion  2121  is located on the overcap  1116  indirectly disposed at the upper end of the support bracket  1112 ). Said gas spool  1002  has a second protrusion  2183  protruding towards said first projection  2121 . The first protrusion  2121  and the second protrusion  2183  are disposed opposite or facing each other. 
     Both ends of the compression spring  1113  are fixedly sleeved outside of the first protrusion  2121  and the second protrusion  2183 , respectively, to provide mounting positions for the compression spring  1113 . After the gas valve core  1002  is pushed upward by the linkage rod  1013  until the second protrusion  2183  contacts the first protrusion  2121 , reaching the top dead center position of the gas valve core  1002 , the upward movement cannot be continued, so that a compression limit for compressing the compression spring  1113  is avoided, thereby breaking the elasticity of the compression spring  1113 , thereby ensuring precise regulation of the gas air. 
     Any numeral values cited in this text include all values of the lower values and the upper values from the lower limit value to the upper limit value, in increments of one unit, provided that there is a separation of at least two units between any lower value and any higher value. For example, if a value illustrating the number or process variable (such as temperature, pressure and time, etc.) of a component is from 1 to 90, preferably from 20-80, and more preferably from  30  to  70 , then the purpose is to explain that the Description also explicitly enumerates values such as 15 to 85, 22 to 68, 43 to 51 and 30 to 32. For values which are less than one, one unit is appropriately considered to be 0.0001, 0.001, 0.01 or 0.1. These are only examples intended to be explicitly expressed, and all possible combinations of numerical values between the lowest value and the highest value enumerated are all expressly stated in the Description in similar ways. 
     Unless otherwise stated, all ranges include the endpoints and all numbers that fall between the endpoints. The use of “about” or “approximately” together with a range applies to both ends of the range. Therefore, “about  20  to  30 ” is intended to cover “about  20  to about  30 ”, inclusive of at least the specified endpoints. 
     All disclosed articles and reference materials, including patent applications and publications, are incorporated herein by reference. The term “substantially formed of . . . ” describing combinations should include the determined elements, components, parts or steps as well as other elements, components, parts or steps that do not affect the basic novel features of the combination in substance. The use of the term “contain” or “include” to describe the combinations of elements, components, parts or steps herein also give rise to the embodiments constituted substantially by these elements, components, parts or steps. The term “may” as used herein is intended to explain that any attribute included by the “may” as described is selectable. 
     Multiple elements, components, parts or steps can be provided by a single integrated element, component, part or step. Alternatively, a single integrated element, component, part or step can be divided into multiple separate elements, components, parts or steps. The disclosed “a” or “an” used for describing elements, components, parts or steps do not exclude other elements, components, parts or steps. 
     It is to be understood that the above description is intended to be graphically illustrative and not restrictive. Many embodiments and applications other than the examples provided would be apparent to those skilled in the art upon reading the above description. Therefore, the scope of the present teaching should not be determined with reference to the above description, but should, instead, be determined with reference to the appended claims, along with the full scope of the equivalents thereof. The disclosures of all articles and references, including patent applications and publications, are incorporated by reference for all purposes. The omission in the foregoing claims of any aspect of the subject matter that is disclosed herein is not a disclaimer of this subject matter, nor should it be regarded as the inventors not considering this subject matter to be a part of the disclosed utility model subject matter.