Needle valve mechanism and gas ejector

Abstract

The invention relates to the technical field of gas ejectors, and particularly discloses a needle valve mechanism and a gas ejector, and the needle valve mechanism comprises a valve body, a valve needle assembly and a buffer assembly. The buffering assembly comprises a buffering seat and a buffering movable part, the outer wall of the buffering seat is matched with the inner wall of the circulation cavity in a sealed mode, the buffering movable part is movably arranged in the buffering cavity, and therefore the effect of abutting against or avoiding the valve needle assembly is achieved. According to the needle valve mechanism, the buffering assembly is arranged, and the problems that in the prior art, when a valve needle opens a valve port and then returns, large impact abrasion is generated on the contact face of the valve port, the stroke amount of the valve needle is increased, and the stability of the gas injection amount of a gas injector is affected are effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of gas injectors, and in particular to a needle valve mechanism and a gas injector. Background Art

[0002] At present, for the types of gas injectors known in the prior art, compared with liquid fuel injectors, gas injectors require a larger stroke, and the contact sealing surface is not lubricated with oil. In the process of returning the valve needle after opening the valve port, dry friction and dry impact will be formed on the contact surface of the valve port, which may cause large impact wear on the sealing contact surface and cause the stroke of the valve needle to increase, thereby affecting the stability and consistency of the gas injector injection volume and affecting the service life of the needle valve mechanism. Summary of the invention

[0003] The purpose of the present invention is to provide a needle valve mechanism and a gas injector to solve the problem in the prior art that when the valve needle returns to its original position after opening the valve port, it will cause severe impact wear on the contact surface of the valve port, causing the stroke of the valve needle to increase, thereby affecting the stability of the gas injector's injection volume.

[0004] On the one hand, the present invention provides a needle valve mechanism, which includes: a valve body, having a flow chamber and a valve port which are interconnected, the flow chamber being used for gas fuel circulation; a valve needle assembly, movably arranged in the flow chamber to block or avoid the valve port; a buffer assembly, including a buffer seat and a buffer movable part, the buffer seat being arranged in the flow chamber and located on the side of the valve needle assembly away from the valve port, the outer wall of the buffer seat being sealed with the inner wall of the flow chamber, the buffer seat having a buffer chamber and a first communicating hole, the first communicating hole being connected to the flow chamber, the buffer movable part having a throttling communicating hole, the throttling communicating hole penetrating the buffer movable part along the axial direction of the valve needle assembly, the buffer chamber being able to communicate with the flow chamber through the throttling communicating hole, and the buffer movable part being movably arranged in the buffer chamber to abut against or avoid the valve needle assembly.

[0005] As an optional technical solution for the needle valve mechanism, the buffer assembly also includes a buffer elastic member, which is located in the buffer cavity, one end of the buffer elastic member abuts against the inner wall of the buffer cavity, and the other end of the buffer elastic member abuts against one end of the buffer movable member away from the valve port.

[0006] As an optional technical solution of the needle valve mechanism, the buffer elastic member is a buffer spring, and the stiffness of the buffer spring is k, 0.5N / mm≤k≤1.5N / mm.

[0007] As an optional technical solution for the needle valve mechanism, the throttling connecting hole includes a first flow hole, a throttling hole and a second flow hole which are connected in sequence, the first flow hole is connected to the flow cavity, the second flow hole is connected to the buffer cavity, and the aperture of the throttling hole is smaller than the aperture of the first flow hole and the aperture of the second flow hole.

[0008] As an optional technical solution of the needle valve mechanism, at least a portion of the buffer movable part is located in the buffer cavity, and a gap between the movable part and the inner wall of the buffer cavity is 0.005 mm-0.0.1 mm.

[0009] As an optional technical solution for the needle valve mechanism, the end surface of the buffer movable part facing the valve port abuts against the end surface of the valve needle assembly away from the valve port to form a sealing structure, and the sealing structure can seal the throttling connecting hole. The sealing structure is a plane seal, a spherical seal, a conical seal, or a non-metallic seal.

[0010] As an optional technical solution for the needle valve mechanism, the valve needle assembly includes a valve needle body, a limit member and a return elastic member. The limit member is sleeved on the valve needle body and connected to the inner wall of the circulation chamber. The two ends of the return elastic member respectively abut the limit member and the inner wall of the circulation chamber. The valve needle body is movably arranged in the circulation chamber to block or avoid the valve port, and the valve needle body can abut against the buffer movable member.

[0011] As an optional technical solution for the needle valve mechanism, the limit member includes a limit block and a fixed block, the limit block is sleeved on the valve needle body and connected to the inner wall of the circulation cavity, the fixed block is sleeved on the valve needle body and abuts against one end of the limit block away from the valve port, the limit block has a second connecting hole, and the second connecting hole connects the circulation cavity with the valve port.

[0012] As an optional technical solution for the needle valve mechanism, the valve needle body includes a first section, a second section and a sealing section which are connected in sequence, the diameter of the first section is smaller than the diameter of the second section, the diameter of the second section is smaller than the diameter of the sealing section, the first section can abut against the buffer movable part, the sealing section is located outside the valve body, and can block or avoid the valve port.

[0013] In another aspect, the present invention provides a gas injector, comprising the needle valve mechanism described in any one of the above schemes.

[0014] The beneficial effects of the present invention are:

[0015] The present invention provides a needle valve mechanism, which includes a valve body, a valve needle assembly and a buffer assembly. The valve body has a flow cavity and a valve port that are interconnected, and the buffer assembly includes a buffer seat and a buffer movable part. The needle valve mechanism of the present invention is provided with a buffer seat and a buffer movable part, the outer wall of the buffer seat is sealed with the inner wall of the flow cavity, and the buffer movable part is movably arranged in the buffer cavity, so as to achieve the function of abutting or avoiding the valve needle assembly. Among them, after the gas fuel passes through the circulation chamber and the first circulation hole in sequence, the pressure generated by the gas fuel acts on the valve needle assembly, so that the valve needle assembly opens the valve port and the gas injector starts to work. At this time, in the process of the valve needle assembly opening the valve port, the buffer movable part will not move toward the valve needle assembly due to the vacuum suction of the buffer chamber. At this time, the buffer movable part avoids the valve needle assembly, and the buffer chamber is connected with the circulation chamber through the throttling connecting hole. The gas fuel enters the buffer chamber. At this time, the buffer movable part moves toward the valve needle assembly due to its own gravity; when the gas fuel is stopped from being introduced, in the process of the valve needle assembly returning to its original position, the valve needle assembly abuts against the buffer movable part. Due to the action of the throttling connecting hole, the valve needle assembly is prevented from separating from the buffer movable part, so that the buffer movable part can play a buffering role on the valve needle assembly when returning to its original position, effectively preventing the valve needle assembly from colliding with and wearing the valve port. By utilizing the needle valve mechanism of the present invention and providing a buffer assembly, the problem in the prior art that when the valve needle returns to its original position after opening the valve port, severe impact wear on the contact surface of the valve port occurs, causing the valve needle's stroke to increase, thereby affecting the stability of the gas injector's jet volume is effectively solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a cross-sectional view of a needle valve mechanism in an embodiment of the present invention;

[0017] Figure 2 for Figure 1 A partial enlarged view of the .

[0018] In the figure:

[0019] 1. Valve body; 11. Flow chamber; 12. Valve port; 13. First step surface; 14. Second step surface;

[0020] 2. Valve needle assembly; 21. Valve needle body; 211. First section; 212. Second section; 213. Blocking section; 2131. Abutting surface; 22. Limiting member; 221. Limiting block; 2211. Second communicating hole; 222. Fixing block; 23. Return elastic member;

[0021] 3. Buffer assembly; 31. Buffer seat; 311. Buffer cavity; 312. First communication hole; 32. Buffer movable part; 321. Throttling communication hole; 3211. First flow hole; 3212. Throttling hole; 3213. Second flow hole; 33. Buffer elastic part;

[0022] 4. Sealed structure. DETAILED DESCRIPTION

[0023] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] In the description of the present invention, it should be noted that the orientations or positional relationships indicated by the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. Among them, the terms "first position" and "second position" are two different positions, and the first feature "above", "above" and "above" the second feature include the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. The first feature "below", "below" and "below" the second feature include the first feature being directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0025] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0027] like Figure 1 to Figure 2As shown, this embodiment provides a needle valve mechanism, which includes a valve body 1, a valve needle assembly 2 and a buffer assembly 3. Among them, the valve body 1 has a flow chamber 11 and a valve port 12 which are interconnected, and the flow chamber 11 is used for the circulation of gas fuel; the valve needle assembly 2 is movably arranged in the flow chamber 11 to block or avoid the valve port 12; the buffer assembly 3 includes a buffer seat 31 and a buffer movable part 32, the buffer seat 31 is arranged in the flow chamber 11, and is located on the side of the valve needle assembly 2 away from the valve port 12, the outer wall of the buffer seat 31 is sealed with the inner wall of the flow chamber 11, the buffer seat 31 has a buffer chamber 311 and a first connecting hole 312, the first connecting hole 312 is connected to the flow chamber 11, the buffer movable part 32 has a throttling connecting hole 321, the throttling connecting hole 321 passes through the buffer movable part 32 along the axial direction of the valve needle assembly 2, the buffer chamber 311 can be connected with the flow chamber 11 through the throttling connecting hole 321, and the buffer movable part 32 is movably arranged in the buffer chamber 311 to abut or avoid the valve needle assembly 2.

[0028] When the gas fuel passes through the circulation chamber 11 and the first connecting hole 312 in sequence, the pressure generated by the gas fuel acts on the valve needle assembly 2, so that the valve needle assembly 2 opens the valve port 12, and the gas injector starts to work. At this time, in the process of the valve needle assembly 2 opening the valve port 12, the buffer movable part 32 will not move toward the valve needle assembly 2 due to the vacuum suction of the buffer chamber 311. At this time, the buffer movable part 32 avoids the valve needle assembly 2, and the buffer chamber 311 is connected with the circulation chamber 11 through the throttling connecting hole 321. The gas fuel enters the buffer chamber 311. At this time, the buffer movable part 32 moves toward the valve needle assembly 2 due to its own gravity; when the gas fuel is stopped from being introduced, in the process of the valve needle assembly 2 returning to its original position, the valve needle assembly 2 abuts against the buffer movable part 32. Due to the action of the throttling connecting hole 321, the valve needle assembly 2 is prevented from separating from the buffer movable part 32, so that the buffer movable part 32 can play a buffering role on the valve needle assembly 2 when returning to its original position, effectively preventing the valve needle assembly 2 from colliding with and wearing the valve port 12. By utilizing the needle valve mechanism of the present invention and providing a buffer assembly 3, the problem in the prior art that when the valve needle returns to its original position after opening the valve port, the contact surface of the valve port will be greatly impacted and worn, resulting in a larger stroke of the valve needle, thereby affecting the stability of the gas injector's injection volume is effectively solved.

[0029] It should be noted that the buffer chamber designed in the present invention has a fixed sealed volume. The pneumatic damping generated during the movement can resist the rebound force generated by the return elastic part of the valve needle assembly 2, slow down the return speed of the valve needle assembly 2, thereby reducing the impact force of the contact surface between the valve needle assembly 2 and the valve port 12, reducing the rebound and seating impact, thereby reducing the impact wear, controlling the stroke amount, and improving the service life of the needle valve mechanism.

[0030] Among them, the return and rebound of the valve needle assembly 2 are directly buffered by using a fixed sealed volume to generate air resistance. At the same time, the size of the buffer chamber and the throttling connecting hole 321 needs to be accurately calculated and determined, and the weight of the buffer movable part needs to be designed to be greater than the air resistance so that the return response of the buffer movable part meets the design requirements.

[0031] In some embodiments, the buffer assembly 3 further includes a buffer elastic member 33. The buffer elastic member 33 is located in the buffer cavity 311, and one end of the buffer elastic member 33 is abutted against the inner wall of the buffer cavity 311, and the other end of the buffer elastic member 33 is abutted against the end of the buffer movable member 32 away from the valve port 12. Such a configuration has the effect of pushing the buffer movable member 32, and can effectively improve the falling response speed of the buffer movable member 32. The buffer elastic member 33 has a certain amount of compression.

[0032] Specifically, in this embodiment, the buffer elastic member 33 is a buffer spring, wherein the stiffness of the buffer spring is k, 0.5N / mm≤k≤1.5N / mm. In this configuration, the buffer spring is preferably a small stiffness spring, which will not produce a large amount of compression and affect the movement of the buffer movable member 32. The stiffness of the buffer spring can be determined according to the design weight of the buffer movable member 32.

[0033] Optionally, the buffer movable member 32 is a buffer piston, the buffer piston has a spring fixing groove, and the other end of the buffer spring is arranged in the spring fixing groove.

[0034] like Figure 2 As shown, the throttling connecting hole 321 includes a first flow hole 3211, a throttling hole 3212 and a second flow hole 3213 which are connected in sequence. The first flow hole 3211 is connected to the flow chamber 11, and the second flow hole 3213 is connected to the buffer chamber 311. The aperture of the throttling hole 3212 is set to be smaller than the aperture of the first flow hole 3211 and the aperture of the second flow hole 3213. The aperture size of the throttling hole 3212 can be adjusted, so that the falling speed of the buffer piston can be controlled according to the size of the throttling hole 3212 and the stiffness of the buffer spring. At the same time, the parameter design of the throttling hole 3212 needs to consider the injection time and interval of the gas injector.

[0035] Among them, the aperture size of the throttling hole 3212 needs to be calculated according to the volume of the buffer chamber 311, and the flow rate of the throttling hole 3212 and the volume of the buffer chamber 311 need to have a certain ratio. During the downward process of the valve needle assembly 2, it can ensure that the throttling hole 3212 can quickly balance the pressure difference between the inside and outside of the buffer chamber 311 to improve the responsiveness of the buffer piston movement, and during the upward process of the valve needle assembly 2, it can ensure that the throttling hole 3212 can produce a throttling effect to prevent the valve needle assembly 2 from separating from the buffer piston, so as to control the magnitude of the buffer force.

[0036] Furthermore, at least part of the buffer movable part 32 is located in the buffer cavity 311, and the gap between the buffer movable part 32 and the inner wall of the buffer cavity 311 is 0.005mm-0.0.1mm. This arrangement can ensure that the buffer movable part 32 can move smoothly in the buffer cavity 311, and at the same time, too much gas will not enter the buffer cavity 311 from the gap between the buffer movable part 32 and the inner wall of the buffer cavity 311.

[0037] Specifically, the end surface of the buffer movable part 32 facing the valve port 12 abuts against the end surface of the valve needle assembly 2 facing away from the valve port 12 to form a sealing structure 4. The throttling communication hole 321 can be sealed by the sealing structure 4. In some embodiments, the sealing structure 4 can be configured as a plane seal, a spherical seal, a conical seal, or a non-metallic seal.

[0038] Among them, the sealing contact surface of the plane seal is a plane, and the sealing effect is achieved through the uniformly distributed sealing pressure ratio.

[0039] The sealing surface of the spherical seal is designed to be conical, and a high sealing pressure ratio is generated under the action of axial force through a narrow contact surface. Usually, a guide structure (such as a valve disc guide) is required to ensure accurate alignment of the sealing surface.

[0040] The sealing contact surface of the cone seal is a spherical surface, which relies on the line contact or narrow surface contact between the ball and the valve seat to form a high specific pressure seal.

[0041] The non-metallic seal is made of non-metallic materials such as rubber, plastic (such as fluororubber, silicone rubber), and graphite, and the seal is achieved by filling the microscopic gap through elastic deformation. The metal-non-metallic composite structure is partially used to enhance the performance. In this embodiment, the friction between the buffer movable part 32 and the valve needle assembly 2 when they are in contact can be reduced, thereby increasing the service life.

[0042] Specifically, the valve needle assembly 2 includes a valve needle body 21, a stopper 22 and a return elastic member 23. The stopper 22 is sleeved on the valve needle body 21 and connected to the inner wall of the circulation chamber 11. The stopper 22 can limit the valve needle body 21, thereby limiting the movement range of the valve needle body 21; the two ends of the return elastic member 23 respectively abut the stopper 22 and the inner wall of the circulation chamber 11, so that the return elastic member 23 can return the valve needle body 21; wherein, the valve needle body 21 is movably arranged in the circulation chamber 11 to block or avoid the valve port 12, and the valve needle body 21 can abut against the buffer movable member 32.

[0043] Furthermore, the limiting member 22 includes a limiting block 221 and a fixing block 222. The limiting block 221 is sleeved on the valve needle body 21 and connected to the inner wall of the circulation cavity 11, and the fixing block 222 is sleeved on the valve needle body 21 and abuts against one end of the limiting block 221 away from the valve port 12 to fix the limiting block 221. The limiting block 221 has a second connecting hole 2211, and the second connecting hole 2211 connects the circulation cavity 11 with the valve port 12, so that the gas fuel is ejected from the valve port 12 after passing through the second connecting hole 2211.

[0044] Alternatively, if Figure 1 As shown, the valve body has a first step surface 13 and a second step surface, the distance between the limit block 221 and the first step surface 13 is H, H is the maximum movement range of the valve needle body 21, and the two ends of one end of the return elastic member 23 are respectively abutted against the limit block 221 and the second step surface 14.

[0045] Specifically, the valve needle body 21 includes a first section 211, a second section 212 and a blocking section 213 which are connected in sequence. The diameter of the first section 211 is smaller than the diameter of the second section 212, and the diameter of the second section 212 is smaller than the diameter of the blocking section 213. The first section 211 is abutted against the buffer movable part 32. The blocking section 213 is located outside the valve body 1 and can block or avoid the valve port 12. The blocking section has an abutting surface 2131, and the valve port 12 is blocked or avoided by the abutting surface 2131.

[0046] This embodiment also provides a gas injector, comprising the needle valve mechanism in the above solution. When the gas fuel passes through the circulation chamber 11 and the first connecting hole 312 in sequence, the pressure generated by the gas fuel acts on the valve needle assembly 2, so that the valve needle assembly 2 opens the valve port 12, and the gas injector starts to work. At this time, in the process of the valve needle assembly 2 opening the valve port 12, the buffer movable part 32 will not move toward the valve needle assembly 2 due to the vacuum suction of the buffer chamber 311. At this time, the buffer movable part 32 avoids the valve needle assembly 2, and the buffer chamber 311 is connected with the circulation chamber 11 through the throttling connecting hole 321. The gas fuel enters the buffer chamber 311. At this time, the buffer movable part 32 moves toward the valve needle assembly 2 due to its own gravity; when the gas fuel is stopped from being introduced, in the process of the valve needle assembly 2 returning to its original position, the valve needle assembly 2 abuts against the buffer movable part 32. Due to the action of the throttling connecting hole 321, the valve needle assembly 2 is prevented from separating from the buffer movable part 32, so that the buffer movable part 32 can play a buffering role on the valve needle assembly 2 when returning to its original position, effectively preventing the valve needle assembly 2 from colliding with and wearing the valve port 12. By using the gas injector of the present invention, by setting the buffer component 3, the problem in the prior art that when the valve needle returns to its original position after opening the valve port, the contact surface of the valve port will be greatly impacted and worn, resulting in a larger stroke of the valve needle, thereby affecting the stability of the gas injector's injection volume is solved.

[0047] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A needle valve mechanism, which can be used in a gas injector, characterized in that: include: A valve body (1) having a flow cavity (11) and a valve port (12) which are interconnected, wherein the flow cavity (11) is used for allowing gas fuel to flow; A valve needle assembly (2) is movably arranged in the circulation chamber (11) to block or avoid the valve port (12); A buffer assembly (3) comprises a buffer seat (31) and a buffer movable part (32), wherein the buffer seat (31) is arranged in the circulation chamber (11) and is located on the side of the valve needle assembly (2) away from the valve port (12), the outer wall of the buffer seat (31) is sealed with the inner wall of the circulation chamber (11), the buffer seat (31) has a buffer chamber (311) and a first connecting hole (312), the first connecting hole (312) is connected to the circulation chamber (11), the buffer movable part (32) has a throttling connecting hole (321), the throttling connecting hole (321) passes through the buffer movable part (32) along the axial direction of the valve needle assembly (2), the buffer chamber (311) can be connected with the circulation chamber (11) through the throttling connecting hole (321), and the buffer movable part (32) is movably arranged in the buffer chamber (311) to abut or avoid the valve needle assembly (2).

2. The needle valve mechanism according to claim 1, characterized in that: The buffer assembly (3) further comprises a buffer elastic member (33), wherein the buffer elastic member (33) is located in the buffer cavity (311), one end of the buffer elastic member (33) abuts against the inner wall of the buffer cavity (311), and the other end of the buffer elastic member (33) abuts against one end of the buffer movable member (32) facing away from the valve port (12).

3. The needle valve mechanism according to claim 2, characterized in that: The buffer elastic member (33) is a buffer spring, the stiffness of the buffer spring is k, and 0.5 N / mm≤k≤1.5 N / mm.

4. The needle valve mechanism according to claim 1, characterized in that: The throttling connecting hole (321) includes a first flow hole (3211), a throttling hole (3212) and a second flow hole (3213) which are connected in sequence, the first flow hole (3211) is connected to the flow chamber (11), the second flow hole (3213) is connected to the buffer chamber (311), and the aperture of the throttling hole (3212) is smaller than the aperture of the first flow hole (3211) and the aperture of the second flow hole (3213).

5. The needle valve mechanism according to claim 1, characterized in that: At least part of the buffer movable part (32) is located in the buffer cavity (311), and the gap between the movable part (32) and the inner wall of the buffer cavity (311) is 0.005 mm-0.0.1 mm.

6. The needle valve mechanism according to claim 1, characterized in that: The end surface of the buffer movable part (32) facing the valve port (12) abuts against the end surface of the valve needle assembly (2) facing away from the valve port (12) to form a sealing structure (4). The sealing structure (4) is capable of sealing the throttling connecting hole (321). The sealing structure (4) is a plane seal, a spherical seal, a conical seal, or a non-metallic seal.

7. The needle valve mechanism according to claim 1, characterized in that: The valve needle assembly (2) includes a valve needle body (21), a limit member (22) and a return elastic member (23); the limit member (22) is sleeved on the valve needle body (21) and connected to the inner wall of the circulation chamber (11); the two ends of the return elastic member (23) respectively abut the limit member (22) and the inner wall of the circulation chamber (11); the valve needle body (21) is movably arranged in the circulation chamber (11) to block or avoid the valve port (12); the valve needle body (21) can abut against the buffer movable member (32).

8. The needle valve mechanism according to claim 7, characterized in that: The limiting member (22) comprises a limiting block (221) and a fixing block (222); the limiting block (221) is sleeved on the valve needle body (21) and connected to the inner wall of the circulation cavity (11); the fixing block (222) is sleeved on the valve needle body (21) and abuts against one end of the limiting block (221) away from the valve port (12); the limiting block (221) has a second connecting hole (2211), and the second connecting hole (2211) connects the circulation cavity (11) with the valve port (12).

9. The needle valve mechanism according to claim 7, characterized in that: The valve needle body (21) includes a first section (211), a second section (212) and a blocking section (213) which are connected in sequence, the diameter of the first section (211) is smaller than the diameter of the second section (212), the diameter of the second section (212) is smaller than the diameter of the blocking section (213), the first section (211) can abut against the buffer movable part (32), the blocking section (213) is located outside the valve body (1) and can block or avoid the valve port (12).

10. A gas injector, characterized in that: It comprises the needle valve mechanism as described in any one of claims 1 to 9.

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