Valve core unit and mass flow meter

Abstract

The utility model provides a valve core unit and a mass flowmeter, wherein the valve core unit includes: a first valve core, a second valve core, a third valve core and a switch component; the first valve core is provided with a through hole, the second valve core is stacked with the first valve core, the second valve core is provided with an assembly shaft, the assembly shaft is located below the through hole, the third valve core is sealably assembled on the assembly shaft, the third valve core is used to abut against the first valve core to seal the through hole, the switch component is penetrated through the through hole and can move along the depth direction of the through hole, the switch component is used to abut against the assembly shaft and drive the second valve core and the third valve core to move synchronously to open and close the through hole; wherein the first valve core, the second valve core and the assembly shaft are metal alloy parts, the third valve core is a resin material part, and the hardness of the resin material part is less than that of the metal alloy part. By adopting the above technical solution: the durability and service life of the valve core unit are improved, a lower closed valve leakage rate is achieved, and at the same time, it has strong corrosion resistance, is easy to process and has reasonable cost.

Description

Technical Field

[0001] The utility model relates to the technical field of mass flow meters, and more specifically to a valve core unit and a mass flow meter. Background Art

[0002] Mass flow meter (MFC, Mass Flow Controller) is a device that measures and controls gas flow. When the valve is closed, the gas flow can be controlled to be theoretically 0, but when the valve is closed, a small amount of gas still flows through the gap. The ratio of the gas flow through the gap to the total range is generally called the closed valve leakage rate. The closed valve leakage rate is a key indicator of the mass flow meter, and the main factor affecting this indicator is the valve core of the mass flow meter.

[0003] The existing common valve core unit includes an upper valve core 6 and a lower valve core 7. The contact surfaces of the upper valve core 6 and the lower valve core 7 are ground to form an assembly surface. Figures 1 to 3 As shown, the upper surface of the lower valve core 7 is pressed against the lower surface of the upper valve core 6 by the spring 8, so that the two are in close contact, and the contact surfaces are in close contact with each other to ensure that the flow capacity is basically zero when the valve is closed; it needs to be further explained that the upper valve core 6 is fixed relative to the lower valve core 7, and the lower valve core 7 is connected to the spring 8, and the spring 8 provides the lower valve core 7 with an upward elastic force, so the lower valve core 7 is sealed and connected to the upper valve core 6 under the elastic force of the spring 8. In order to ensure the sealing and other performance of the valve core unit, the following methods are usually used:

[0004] Solution 1: The upper valve core 6 and the lower valve core 7 are made of metal alloy (including but not limited to stainless steels such as 304, 316, 316L, nickel alloys such as Hastelloy), and the lower contact surface of the upper valve core 6 and the upper contact surface of the lower valve core 7 are ground using a mechanical grinding process to achieve a roughness of less than Ra0.1. The upper and lower contact surfaces are pressed to death with a force of more than 5N, which can ensure a 1% closed valve leakage rate in the closed valve state. The advantage of this solution is that when the valve is switched, the lower valve core 7 will not be deformed even if it is hit by moving parts such as the push rod, which can ensure the long-term normal operation of the valve core, and the service life is generally more than 20 million times. In addition, the corrosion resistance can meet the requirements. The disadvantages of this solution are: 1. The closed valve leakage rate is high. Common precision machine tools can only process the surface roughness below Ra0.1 to achieve a leakage rate of about 1%; 2. The processing is difficult. If you want to improve the closed valve leakage rate, you need to increase the flatness / roughness to the nanometer level or even below, which is too difficult to process; 3. Poor repeatability: The sealing principle of the upper valve core 6 and the lower valve core 7 is to press the upper and lower contact surfaces to death, and seal the mass flow meter through the micro-plastic deformation of the metal. The spring 8 applies pressure to the upper valve core 6 and the lower valve core 7 to cause micro-plastic deformation of the contact surface, and then fill the slight roughness of the contact surface to produce sealing. In this process, due to the plastic deformation of the contact surface, and the shape of the roughness of the contact surface is completely random, so after the second disassembly, the original bonding surface will be dislocated, resulting in a significant weakening of the sealing performance, thereby affecting the repeatability.

[0005] Solution 2: The lower valve core 7 is plated on the upper surface of the metal alloy using resin material, and the upper valve core 6 is made of metal alloy material. The contact surface of the upper valve core 6 is the same as Solution 1, and the mechanical grinding process is used to achieve a roughness below Ra0.1. The lower valve core 7 is plated with resin material and then ground to a surface roughness below Ra0.1. The advantage of this solution is that the surface of the lower valve core 7 is made of resin material, and the hardness is much lower than that of the metal alloy material. When the upper valve core 6 and the lower valve core 7 are matched, in addition to microscopic deformation, the gap caused by the difference in surface roughness can be filled by local elastic deformation of the surface of the lower valve core 7, so that a lower closed valve leakage rate can be achieved under the same roughness, generally reaching a level below 0.2‰, and the corrosion resistance and repeatability are good (the elastic deformation of the resin material can compensate for the gap caused by microscopic plastic deformation). The disadvantage is that the resin material needs to be coated on the metal substrate through processes such as electrostatic adsorption, and its bonding force is weak, and it is easy to fall off during grinding. The roughness and flatness of the sealing surface are not easy to improve, and the quality is not easy to guarantee.

[0006] Solution 3: The upper valve core 6 and the lower valve core 7 are made of two different materials. The upper valve core 6 is made of metal alloy material, and the lower valve core 7 is made of resin material. As in Solution 1, a mechanical grinding process is used to achieve a roughness of less than 0.1 for the upper valve core 6 and less than 0.2 for the lower valve core 7. The advantages of this solution are the same as those of Solution 2. The disadvantage is that the lower valve core 7 is made of resin material, which is softer than metal alloy material. When the metal push rod of the movable part repeatedly hits the lower valve core 7, cracks are easily generated in the lower valve core 7. The service life is only at the level of millions of times, and the valve closing leakage rate is greatly affected by temperature changes, and the scope of use is limited.

[0007] In summary, the existing valve core unit cannot take into account both sealing performance and service life. Utility Model Content

[0008] The utility model aims to provide a valve core unit and a mass flow meter to solve the technical problem in the prior art that the valve core unit cannot take into account both sealing performance and service life.

[0009] In order to achieve the above purpose, the technical solution adopted by the utility model is:

[0010] In a first aspect, a valve core unit is provided, comprising:

[0011] A first valve core, a second valve core, a third valve core and a switch component; the first valve core is provided with a through hole, the second valve core is stacked with the first valve core, the second valve core is provided with an assembly shaft, the assembly shaft is located below the through hole, the third valve core is sealingly assembled on the assembly shaft, the third valve core is used to abut against the first valve core to seal the through hole, the switch component is penetrated through the through hole and can move along the depth direction of the through hole, the switch component is used to abut against the assembly shaft and drive the second valve core and the third valve core to move synchronously to open and close the through hole; wherein, the first valve core, the second valve core and the assembly shaft are metal alloy parts, the third valve core is a resin material part, and the hardness of the resin material part is less than that of the metal alloy part.

[0012] By adopting the above technical solution:

[0013] First, the assembly shaft and the second valve core are made of metal alloy parts, which have high hardness and can withstand the reciprocating impact of the switch component, reducing the possibility of cracks on the assembly shaft and the second valve core, and improving the durability and service life of the valve core unit;

[0014] Secondly, the third valve core is made of resin material with low hardness. When it contacts and cooperates with the first valve core, it can produce micro deformation to fill the gap caused by the difference in surface roughness, thereby achieving a lower closed valve leakage rate and better sealing performance;

[0015] Thirdly, the third valve core seal is assembled on the assembly shaft, the two are assembled firmly and not easy to separate, and the assembly process will not damage the sealing surface, thereby improving the quality and yield of the valve core unit;

[0016] Finally, the materials of the first valve core, the second valve core and the third valve core all have strong corrosion resistance, are easy to process and have reasonable cost.

[0017] In one embodiment, the second valve core is provided with a plurality of the assembly shafts, and the third valve core is sealingly assembled on the plurality of the assembly shafts at the same time.

[0018] By adopting the above technical solution, the firmness of the third valve core when assembled to the second valve core is improved, and at the same time, the possibility of the third valve core rotating relative to the second valve core and causing the two to be misaligned can be prevented.

[0019] In one embodiment, the third valve core is sleeved on the second valve core, so that the second valve core is formed with a first assembly surface and a second assembly surface abutting against the third valve core, and the first assembly surface and the second assembly surface are respectively located on different sides of the second valve core.

[0020] By adopting the above technical solution, the third valve core is fixed on the second valve core in a sleeve manner, so that the second valve core is formed with a first assembly surface and a second assembly surface, and the force generated by the abutment between the first assembly surface and the second assembly surface and the third valve core makes the third valve core more secure when assembled on the second valve core.

[0021] In one embodiment, an anti-rotation component is connected between the second valve core and the third valve core, and the anti-rotation component is arranged on the periphery of the assembly shaft.

[0022] By adopting the above technical solution, the third valve core is prevented from rotating relative to the second valve core, and the degree of firmness with which the third valve core is fixed to the second valve core is also improved.

[0023] In one embodiment, the third valve core is an in-mold injection molded part or an interference fit part so as to be in-mold injection molded or interference fit on the second valve core.

[0024] By adopting the above technical solution, the degree of firmness with which the third valve core is fixed to the second valve core is improved.

[0025] In one embodiment, the third valve core is provided with an inner hole that cooperates with the assembly shaft, the hole wall of the inner hole is provided with a limiting groove, and the assembly shaft is provided with a positioning structure that cooperates with the limiting groove; the assembly shaft is inserted into the inner hole and the positioning structure is inserted into the limiting groove, so that the assembly shaft and the third valve core are interference fit and sealed.

[0026] By adopting the above technical solution, the degree of firmness with which the third valve core is fixed to the second valve core is improved, and at the same time the positioning structure can also indicate that the third valve core is assembled in place, which is conducive to obtaining the assembly status.

[0027] In one embodiment, the second valve core is provided with an embedded groove, the third valve core is provided with a snap hole and a snap member arranged around the snap hole and used to be embedded in the embedded groove, and the assembly shaft is used to be inserted into the snap hole so that the snap member is embedded in the embedded groove.

[0028] By adopting the above technical solution, the third valve core is fixedly arranged on the second valve core by means of a buckle.

[0029] In one embodiment, the embedded groove includes a main groove section and a snap groove portion connected to the main groove section, the main groove section and the snap groove portion are arranged in sequence along the assembly direction X of the assembly axis, and the size of the snap groove portion in a direction perpendicular to the assembly direction X is greater than the size of the main groove section in a direction perpendicular to the assembly direction X; the snap member includes a main body portion and a snap portion, the main body portion and the snap portion are arranged in sequence along the assembly direction X of the assembly axis, the size of the snap portion in a direction perpendicular to the assembly direction X is greater than the size of the main body portion in a direction perpendicular to the assembly direction X, the main body portion is inserted into the main groove section, and the snap portion is inserted into the snap groove portion.

[0030] By adopting the above technical solution, the third valve core is fixed to the second valve core by using a wedge-nail-tenon structure.

[0031] In one embodiment, the assembly shaft is in a wedge-shaped structure, and the radial dimension of the assembly shaft gradually decreases along the assembly direction X.

[0032] By adopting the above technical solution, the assembly shaft can be easily inserted into the buckle hole, which is beneficial to the installation of the assembly shaft.

[0033] In one embodiment, the third valve core is threadedly connected to the assembly shaft.

[0034] By adopting the above technical solution, the third valve core can be assembled on the assembly shaft by rotating, and the assembly method is simple.

[0035] In one embodiment, the third valve core and the assembly shaft are both provided with tapered threads, and the third valve core and the assembly shaft are tightly assembled via the tapered threads.

[0036] By adopting the above technical solution, the tightness of the assembly between the third valve core and the second valve core connected by threads is further improved.

[0037] In one embodiment, the valve core unit also includes a fourth valve core, and the fourth valve core is provided with a cavity for accommodating the second valve core and the third valve core, and the cavity is used to communicate with the through hole. An elastic member connected to the second valve core is provided in the cavity, and the elastic member is used to drive the third valve core on the second valve core to abut against the first valve core and provide contact stress, so that the third valve core is sealed and connected to the first valve core.

[0038] By adopting the above technical solution, the elastic member is used to provide contact stress, thereby improving the tightness of the sealing connection between the third valve core and the first valve core.

[0039] In a second aspect, a mass flow meter is provided, comprising a mass flow body and the valve core unit mentioned above, wherein the valve core unit is installed on the mass flow body.

[0040] By adopting the above technical scheme, on the basis of the advantages of the valve core unit of the above embodiment, the mass flow meter of this embodiment also has the following advantages: the sealing performance of the valve core unit is improved, and a closed valve leakage rate of 0.05‰ or even below can be achieved; the repeatability of the valve core unit is improved, so that the closed valve leakage rate of the valve core unit will not be significantly deteriorated during repeated disassembly and assembly; the processing requirements are reduced, and the demand for ultra-precision grinding of the metal alloy surface is reduced; the corrosion resistance of the valve core unit is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0042] Figure 1 It is a cross-sectional view of the prior art Figure 1 .

[0043] Figure 2 It is a cross-sectional view of the prior art Figure 2 .

[0044] Figure 3 It is a cross-sectional view of the prior art Figure 3 .

[0045] Figure 4 It is a cross-sectional view of the valve core unit provided in the first embodiment of the utility model.

[0046] Figure 5 It is a cross-sectional view of the valve core unit provided in the second embodiment of the present utility model.

[0047] Figure 6It is a cross-sectional view of the second valve core provided in the second embodiment of the utility model.

[0048] Figure 7 It is a cross-sectional view of the second valve core provided in the third embodiment of the present utility model.

[0049] Figure 8 It is a cross-sectional view of the valve core unit provided in the fourth embodiment of the present utility model.

[0050] Fig. 9 It is an exploded cross-sectional view of the valve core unit provided in the fourth embodiment of the present utility model.

[0051] Fig.10 It is a cross-sectional view of the valve core unit provided in the fifth embodiment of the present utility model.

[0052] Fig.11 It is an exploded cross-sectional view of the valve core unit provided in the fifth embodiment of the present utility model.

[0053] Fig.12 It is a cross-sectional view of the valve core unit provided in the sixth embodiment of the present utility model.

[0054] The reference numerals in the figures are:

[0055] 1. First valve core; 2. Second valve core; 3. Third valve core; 4. Switch element; 5. Fourth valve core; X, assembly direction;

[0056] 11. through hole; 21. assembly axis; 22. positioning structure; 23. embedded groove; 24. first assembly surface; 25. second assembly surface; 26. anti-rotation member; 31. inner hole; 32. limiting groove; 33. buckle hole; 34. buckle member; 35. tapered thread; 51. cavity; 52. elastic member;

[0057] 231, main body groove section; 232, buckle groove portion; 341, main body portion; 342, buckle portion. DETAILED DESCRIPTION

[0058] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0059] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly located on the other element or indirectly located on the other element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or indirectly connected to the other element.

[0060] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention, and do not indicate that a device or element must have a specific direction, be constructed and operated in a specific direction. Therefore, it should not be understood as a limitation on the present invention.

[0061] In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating relative importance or indicating the number of technical features. In the description of the present utility model, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. The following is a more detailed description of the specific implementation of the present utility model in conjunction with specific embodiments:

[0062] like Figure 4 As shown, a valve core unit provided by an embodiment of the utility model is used in mass flow meters in the semiconductor industry to control gas flow; due to the structural limitations of the valve core unit, most mass flow meters can only control the closed valve leakage rate to 1‰ to 1% of the total range, and the parts need to be corrosion-resistant and have a long service life (generally more than one million times). The valve core unit provided in this embodiment, which is assembled and combined with metal alloy and resin materials, can not only reduce the leakage rate to less than 0.05‰ when the valve is closed, but can also be applied to all required gases, and the number of switches can reach 20 million times or more. The following is an explanation through specific implementation methods:

[0063] The valve core unit of this embodiment includes:

[0064] A first valve core 1, a second valve core 2, a third valve core 3 and a switch component 4; the first valve core 1 is provided with a through hole 11, the second valve core 2 is stacked with the first valve core 1, the second valve core 2 is provided with an assembly shaft 21, the assembly shaft 21 is located below the through hole 11, the third valve core 3 is sealingly assembled on the assembly shaft 21, the third valve core 3 is used to abut on the first valve core 1 to seal the through hole 11, the switch component 4 is penetrated through the through hole 11 and can move along the depth direction of the through hole 11, the switch component 4 is used to abut with the assembly shaft 21 and drive the second valve core 2 and the third valve core 3 to move synchronously to open and close the through hole 11; wherein, the first valve core 1, the second valve core 2 and the assembly shaft 21 are metal alloy parts, the third valve core 3 is a resin material part, and the hardness of the resin material part is lower than that of the metal alloy part.

[0065] The first valve core 1 refers to a component constituting a valve core unit. The interior of the first valve core 1 is provided with a through hole 11, which runs through the first valve core 1. The through hole 11 is used for gas to flow through. The first valve core 1 is stacked with the second valve core 1. In this embodiment, the first valve core 1 is located above the second valve core 2. Of course, in actual application scenarios, the first valve core 1 can be located below the second valve core 2, or the first valve core 1 and the second valve core 2 can be distributed left and right.

[0066] The second valve core 2 refers to a component constituting the valve core unit. The second valve core 2 is used to form a cavity connected to the through hole 11 with other components, and the second valve core 2 is provided with an assembly shaft 21. The assembly shaft 21 refers to an axis body used to fix the third valve core 3. The assembly shaft 21 is located below the through hole 11. Of course, in actual application scenarios, the position of the assembly shaft 21 changes with the relative position of the first valve core 1 and the second valve core 2.

[0067] The third valve core 3 refers to a component constituting the valve core unit. The third valve core 3 is sealingly assembled on the assembly shaft 21, so the third valve core 3 and the assembly shaft 21 are sealed and connected. At the same time, the third valve core 3 is used to abut against the first valve core 1 to seal the through hole 11;

[0068] The switch component 4 refers to a component for opening and closing the through hole 11. The switch component 4 is inserted into the through hole 11 and can move along the depth direction of the through hole 11. It needs to be further explained that the switch component 4 is clearance-matched with the through hole 11, that is, the switch component 4 does not affect the ventilation of the through hole 11; the switch component 4 is used to abut against the assembly shaft 21, and the switch component 4 is used to push the assembly shaft 21 to move the second valve core 2. At the same time, since the third valve core 3 is sealingly assembled on the second assembly shaft 21, the second valve core 2 and the third valve core 3 move synchronously; when the third valve core 3 is separated from the first valve core 1, the through hole 11 is opened, and when the third valve core 3 abuts against the first valve core 1, the through hole 11 is closed.

[0069] Among them, the first valve core 1, the second valve core 2 and the assembly shaft 21 are metal alloy parts, here, the metal alloy parts include but are not limited to stainless steels such as 304 (SUS304), 316 (SUS316), 316L (sus 316L), nickel alloy materials such as Hastelloy, these materials have strong corrosion resistance; the third valve core 3 is a resin material part, here, the resin material part includes but is not limited to PCTFE (polytrifluorochloroethylene), PFA (tetrafluoroethylene-perfluoroalkoxy vinyl ether copolymer), PTFE (polytetrafluoroethylene) and other materials, compared with other resin materials, it has good corrosion resistance, small creep, and good processing performance; at the same time, the hardness of the resin material part is less than that of the metal alloy part. Obviously, there is a significant difference in the hardness of the first valve core 1 and the third valve core 3. At the same time, the hardness of the first valve core 1 and the second valve core 2 is the same or basically the same. The first valve core 1, the second valve core 2 and the third valve core 3 all have strong corrosion resistance, are easy to process and have reasonable cost.

[0070] The working principle of the valve core unit provided in this embodiment is as follows:

[0071] When the switch member 4 moves along the depth direction of the through hole 11 and abuts against the assembly shaft 21, the switch member 4 drives the assembly shaft 21, the second valve core 2 and the third valve core 3 to move synchronously. Driven by the switch member 4, the third valve core 3 disengages from or abuts against the first valve core 1 to open and close the through hole 11, thereby realizing the circulation and cutoff of gas.

[0072] By adopting the above technical solution:

[0073] First, the assembly shaft 21 and the second valve core 2 are metal alloy parts with high hardness, which can withstand the reciprocating impact of the switch member 4, reduce the possibility of cracks on the assembly shaft 21 and the second valve core 2, and improve the durability and service life of the valve core unit;

[0074] Secondly, the third valve core 3 is a resin material with low hardness. When it contacts and cooperates with the first valve core 1, it can produce micro deformation to fill the gap caused by the difference in surface roughness, thereby achieving a lower closed valve leakage rate and better sealing performance;

[0075] Thirdly, the third valve core 3 is sealed and assembled on the assembly shaft 21, the two are assembled firmly and not easy to separate, and the assembly process will not damage the sealing surface, thereby improving the quality and yield of the valve core unit;

[0076] Finally, the materials of the first valve core 1 , the second valve core 2 and the third valve core 3 all have strong corrosion resistance, are easy to process and have reasonable cost.

[0077] In one embodiment, the surface where the third valve core 3 contacts the first valve core 1 is a sealing surface. The sealing surface is ground to below Ra0.1, and the metal alloy portion of the first valve core 1 and the assembly shaft 21 is ground to below Ra0.1 to achieve a leakage rate of 1%. If further fine grinding is performed using CMP (Chemical Mechanical Polishing) and other technologies, the leakage rate can reach below 0.05‰.

[0078] In one embodiment, the switch member 4 is in direct contact with the assembly shaft 21 of the second valve core 2, and both contact positions need to be electrolytically polished and passivated to form a dense oxide film, which can ensure that the product will not produce obvious wear and deformation after long-term operation. The actual verified operation times can reach more than 20 million times.

[0079] In one embodiment, a plurality of assembly shafts 21 are disposed on the second valve core 2 , and the third valve core 3 is sealingly assembled on the plurality of assembly shafts 21 at the same time.

[0080] Here, it can be understood that the second valve core 2 is used for sealing assembly with the assembly shaft 21, the second valve core 2 is fixed on the assembly shaft 21 through the force generated by the sealing assembly, the second valve core 2 is provided with multiple assembly shafts 21, and the third valve core 3 is sealed and assembled on multiple assembly shafts 21 at the same time. In this way, the force generated by the multiple assembly shafts 21 can improve the firmness of the third valve core 3 when it is assembled on the second valve core 2; in addition, the multiple assembly shafts 21 can also limit the third valve core 3 to prevent the third valve core 3 from rotating relative to the second valve core 2.

[0081] By adopting the above technical solution, the firmness of the third valve core 3 when assembled to the second valve core 2 is improved, and at the same time, the possibility of the third valve core 3 rotating relative to the second valve core 2 and causing the two to be misaligned can be prevented.

[0082] like Figure 5 and Figure 6 As shown, in one embodiment, the third valve core 3 is sleeved on the second valve core 2, so that the second valve core 2 is formed with a first assembly surface 24 and a second assembly surface 25 that abut against the third valve core 3, and the first assembly surface 24 and the second assembly surface 25 are respectively located on different sides of the second valve core 2.

[0083] Here, it can be understood that the third valve core 3 is sleeved on the second valve core 2. In this embodiment, the second valve core 2 can be a disc-like structure, wherein the first assembly surface 24 is the circular surface of the second valve core 2, and the second assembly surface 25 is the circumferential surface of the second valve core 2.

[0084] By adopting the above technical solution, the third valve core 3 is fixed on the second valve core 2 in a sleeve manner, so that the second valve core 2 forms a first assembly surface 24 and a second assembly surface 25, and the force generated by the abutment between the first assembly surface 24 and the second assembly surface 25 and the third valve core 3 makes the third valve core 3 more secure when assembled on the second valve core 2.

[0085] like Figure 7 As shown, in one embodiment, an anti-rotation component 26 is connected between the second valve core 2 and the third valve core 3 , and the anti-rotation component 26 is disposed on the periphery of the assembly shaft 21 .

[0086] Here, it can be understood that the anti-rotation component 26 is used to connect the second valve core 2 and the third valve core 3 to prevent the second valve core 2 from rotating relative to the third valve core 3; the anti-rotation component 26 includes but is not limited to a pin, and the anti-rotation component 26 is arranged on the periphery of the assembly shaft 21 to prevent the third valve core 3 from rotating around the assembly shaft 21; in addition, the connection between the pin and the third valve core 3 can also provide a force to fix the third valve core 3 on the second valve core 2, thereby improving the firmness of the fixation of the third valve core 3.

[0087] By adopting the above technical solution, the third valve core 3 is prevented from rotating relative to the second valve core 2, and the degree of fixation of the third valve core 3 on the second valve core 2 is also improved.

[0088] In one embodiment, the third valve core 3 is an in-mold injection molded part or an interference fit part to achieve in-mold injection molding or interference fit on the second valve core 2 .

[0089] Here, it can be understood that the third valve core 3 can be fixed to the second valve core 2 by in-mold injection molding or interference fitting; the former in-mold injection molding refers to fixing the third valve core 3 on the assembly shaft 21 by injection molding, and the latter interference fitting refers to the axial hole interference fit between the third valve core 3 and the assembly shaft 21, wherein the third valve core 3 is provided with an inner hole 31, and the aperture of the inner hole 31 is slightly smaller than the outer diameter of the assembly shaft 21. Optionally, the aperture of the inner hole 31 is smaller than the outer diameter of the assembly shaft 21 by more than 5μm. Such a size design can prevent the third valve core 3 and the second valve core 2 from loosening at a temperature exceeding 100°C.

[0090] By adopting the above technical solution, the firmness of the third valve core 3 when being fixed to the second valve core 2 is improved.

[0091] Please also read Figure 8 and Fig. 9 In one embodiment, the third valve core 3 is provided with an inner hole 31 that cooperates with the assembly shaft 21, the hole wall of the inner hole 31 is provided with a limiting groove 32, and the assembly shaft 21 is provided with a positioning structure 22 that cooperates with the limiting groove 32; the assembly shaft 21 is inserted into the inner hole 31 and the positioning structure 22 is inserted into the limiting groove 32, so that the assembly shaft 21 and the third valve core 3 are interference fit and sealed.

[0092] Here, it can be understood that the third valve core 3 is provided with an inner hole 31, and the inner hole 31 is used to achieve an interference fit with the assembly shaft 21; in addition, the hole wall of the inner hole 31 is provided with a limiting groove 32, and the assembly shaft 21 is provided with a positioning structure 22, and the positioning structure 22 is used to cooperate with the limiting groove 32, and the positioning structure 22 includes but is not limited to a convex rib, and the height of the convex rib relative to the assembly shaft 21 is greater than or equal to 10μm, and the positioning structure 22 is inserted into the limiting groove 32 when the third valve core 3 is assembled on the assembly shaft 21, so that the assembly shaft 21 and the third valve core 3 have an interference fit and the two are sealed and assembled; the force generated by the positioning structure 22 being inserted into the limiting groove 32 makes the third valve core 3 fixed on the second valve core 2 more firmly; in addition, the positioning structure 22 being inserted into the limiting groove 32 represents that the two are assembled in place, which is beneficial for the assembler to obtain the assembly state of the third valve core 3.

[0093] By adopting the above technical solution, the degree of fixation of the third valve core 3 to the second valve core 2 is improved, and the positioning structure 22 can also indicate that the third valve core 3 is assembled in place, which is conducive to obtaining the assembly state.

[0094] Please also read Fig.10 and Fig.11 In one embodiment, the second valve core 2 is provided with an embedded groove 23, the third valve core 3 is provided with a snap hole 33 and a snap member 34 arranged around the snap hole 33 and used to be embedded in the embedded groove 23, and the assembly shaft 21 is used to be inserted into the snap hole 33 so that the snap member 34 is embedded in the embedded groove 23.

[0095] Here, it can be understood that the snap-fit ​​part 34 can be placed in the embedded groove 23 by means of clearance or transition fit, and then the assembly shaft 21 is inserted into the snap-fit ​​hole 33, so that the snap-fit ​​part 34 is embedded in the embedded groove 23 and cannot rebound, thereby forming a tight whole, and finally the third valve core 3 is fixedly set on the second valve core 2. In addition, the above design can ensure that it will not loosen during subsequent grinding and normal operation.

[0096] It needs to be further explained that the buckle hole 33 can be the inner hole 31 , because both of them are used to insert the assembly shaft 21 .

[0097] By adopting the above technical solution, the third valve core 3 is fixedly arranged on the second valve core 2 by means of a buckle.

[0098] In one embodiment, the embedded groove 23 includes a main groove section 231 and a snap groove portion 232 connected to the main groove section 231, the main groove section 231 and the snap groove portion 232 are arranged in sequence along the assembly direction X of the assembly axis 21, and the size of the snap groove portion 232 in a direction perpendicular to the assembly direction X is greater than the size of the main groove section 231 in a direction perpendicular to the assembly direction X; the snap member 34 includes a main body 341 and a snap portion 342, the main body 341 and the snap portion 342 are arranged in sequence along the assembly direction X of the assembly axis 21, the size of the snap portion 342 in a direction perpendicular to the assembly direction X is greater than the size of the main body 341 in a direction perpendicular to the assembly direction X, the main body 341 is inserted into the main groove section, and the snap portion 342 is inserted into the snap groove portion 232.

[0099] Here, it can be understood that the size of the buckle portion 342 before assembly is smaller than the size of the buckle groove portion 232 (the buckle portion 342 is not subject to the lateral force of the assembly shaft 21 during the initial assembly, and the buckle portion 342 is stretched open after the assembly shaft 21 is assembled. After the stretching, the diameter of the buckle portion 342 is larger than the size of the buckle groove portion 232, so that the buckle portion 342 is tightly inserted into the buckle groove portion 232 to ensure a firm assembly, and at the same time, the buckle portion 342 applies a large lateral force to ensure that the buckle portion 342 tightly buckles the assembly shaft 21.

[0100] By adopting the above technical solution, the third valve core 3 is fixed to the second valve core 2 by using a wedge-nail-tenon structure.

[0101] In one embodiment, the assembly shaft 21 is a wedge-shaped structure, and the radial dimension of the assembly shaft 21 gradually decreases along the assembly direction X.

[0102] Here, it can be understood that the radial dimension of the assembly shaft 21 can gradually increase, remain unchanged, or gradually decrease along the assembly direction X; in this embodiment, the radial dimension of the assembly shaft 21 gradually decreases along the assembly direction X.

[0103] By adopting the above technical solution, the assembly shaft 21 can be easily inserted into the buckle hole 33 , which is beneficial to the installation of the assembly shaft 21 .

[0104] like Fig.12 As shown, in one embodiment, the third valve core 3 is threadedly connected to the assembly shaft 21 .

[0105] Here, it can be understood that the inner hole 31 of the third valve core 3 is provided with an internal thread, and the axial surface of the assembly shaft 21 is provided with an external thread, and the two are threadedly connected.

[0106] By adopting the above technical solution, the third valve core 3 can be assembled on the assembly shaft 21 by rotating, and the assembly method is simple.

[0107] In one embodiment, both the third valve core 3 and the assembly shaft 21 are provided with tapered threads 35 , and the third valve core 3 and the assembly shaft 21 are tightly assembled via the tapered threads 35 .

[0108] Here, it can be understood that the tapered thread 35 allows the third valve core 3 to be tightened as it is screwed into the assembly shaft 21 of the second valve core 2 along the assembly direction, so that the two form a tight whole, thereby ensuring that they will not loosen during subsequent grinding and normal operation.

[0109] By adopting the above technical solution, the tightness of the assembly between the third valve core 3 and the second valve core 2 connected by threads is further improved.

[0110] Please refer again Figure 4 In one embodiment, the valve core unit also includes a fourth valve core 5, which is provided with a cavity 51 for accommodating the second valve core 2 and the third valve core 3. The cavity 51 is used to communicate with the through hole 11. An elastic member 52 connected to the second valve core 2 is provided in the cavity 51. The elastic member 52 is used to drive the third valve core 3 on the second valve core 2 to abut against the first valve core 1 and provide contact stress, so that the third valve core 3 is sealed and connected to the first valve core 1.

[0111] Here, it can be understood that the elastic member 52 includes but is not limited to a spring.

[0112] By adopting the above technical solution, the elastic member 52 is used to provide contact stress, thereby improving the tightness of the sealing connection between the third valve core 3 and the first valve core 1 .

[0113] In a second aspect, a mass flow meter is provided, comprising a mass flow body and the above-mentioned valve core unit, wherein the valve core unit is installed on the mass flow body.

[0114] By adopting the above technical scheme, on the basis of the advantages of the valve core unit of the above embodiment, the mass flow meter of this embodiment also has the following advantages: the sealing performance of the valve core unit is improved, and a closed valve leakage rate of 0.05‰ or even below can be achieved; the repeatability of the valve core unit is improved, so that the closed valve leakage rate of the valve core unit will not be significantly deteriorated during repeated disassembly and assembly; the processing requirements are reduced, and the demand for ultra-precision grinding of the metal alloy surface is reduced; the corrosion resistance of the valve core unit is improved.

[0115] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. 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 present invention.

Claims

1. A valve core unit, characterized in that: include: A first valve core (1), a second valve core (2), a third valve core (3) and a switch element (4); the first valve core (1) is provided with a through hole (11); the second valve core (2) and the first valve core (1) are stacked; the second valve core (2) is provided with an assembly shaft (21); the assembly shaft (21) is located below the through hole (11); the third valve core (3) is sealingly assembled on the assembly shaft (21); the third valve core (3) is used to abut against the first valve core (1) to seal the through hole (11) The switch member (4) is inserted into the through hole (11) and can move along the depth direction of the through hole (11), and the switch member (4) is used to abut against the assembly shaft (21) and drive the second valve core (2) and the third valve core (3) to move synchronously to open and close the through hole (11); wherein the first valve core (1), the second valve core (2) and the assembly shaft (21) are metal alloy parts, and the third valve core (3) is a resin material part, and the hardness of the resin material part is less than that of the metal alloy part.

2. The valve core unit according to claim 1, characterized in that: The second valve core (2) is provided with a plurality of assembly shafts (21), and the third valve core (3) is simultaneously and sealingly assembled on the plurality of assembly shafts (21).

3. The valve core unit according to claim 1, characterized in that: The third valve core (3) is sleeved on the second valve core (2), so that the second valve core (2) is provided with a first assembly surface and a second assembly surface which abut against the third valve core (3), and the first assembly surface and the second assembly surface are respectively located on different sides of the second valve core (2).

4. The valve core unit according to claim 1, characterized in that: An anti-rotation component is connected between the second valve core (2) and the third valve core (3), and the anti-rotation component is arranged on the periphery of the assembly shaft (21).

5. The valve core unit according to claim 1, characterized in that: The third valve core (3) is an in-mold injection molded part or an interference fit part so as to be in-mold injection molded or interference fit on the second valve core (2).

6. The valve core unit according to claim 1, characterized in that: The third valve core (3) is provided with an inner hole (31) cooperating with the assembly shaft (21); the hole wall of the inner hole (31) is provided with a limiting groove (32); the assembly shaft (21) is provided with a positioning structure (22) cooperating with the limiting groove (32); the assembly shaft (21) is inserted into the inner hole (31) and the positioning structure (22) is inserted into the limiting groove (32), so that the assembly shaft (21) and the third valve core (3) are interference-fitted and sealed.

7. The valve core unit according to claim 1, characterized in that: The second valve core (2) is provided with an embedded groove (23), the third valve core (3) is provided with a snap hole (33) and a snap member (34) arranged around the snap hole (33) and used to be embedded in the embedded groove (23), and the assembly shaft (21) is used to be inserted into the snap hole (33) so that the snap member (34) is embedded in the embedded groove (23).

8. The valve core unit according to claim 7, characterized in that: The embedded groove (23) comprises a main groove section (231) and a buckle groove portion (232) connected to the main groove section (231), the main groove section (231) and the buckle groove portion (232) are arranged in sequence along the assembly direction X of the assembly axis (21), and the size of the buckle groove portion (232) in a direction perpendicular to the assembly direction X is greater than the size of the main groove section (231) in a direction perpendicular to the assembly direction X; the buckle member (34) comprises a main portion ( The main body (341) and the snap-on portion (342) are arranged in sequence along the assembly direction X of the assembly axis (21); the size of the snap-on portion (342) in a direction perpendicular to the assembly direction X is greater than the size of the main body (341) in a direction perpendicular to the assembly direction X; the main body (341) is inserted into the main body groove section (231), and the snap-on portion (342) is inserted into the snap-on groove portion (232).

9. The valve core unit according to claim 8, characterized in that: The assembly shaft (21) is of a wedge-shaped structure, and the radial dimension of the assembly shaft (21) gradually decreases along the assembly direction X.

10. The valve core unit according to claim 1, characterized in that: The third valve core (3) is threadedly connected to the assembly shaft (21).

11. The valve core unit according to claim 10, characterized in that: The third valve core (3) and the assembly shaft (21) are both provided with a tapered thread (35), and the third valve core (3) and the assembly shaft (21) are tightly assembled via the tapered thread (35).

12. The valve core unit according to any one of claims 1 to 11, characterized in that: The valve core unit also includes a fourth valve core (5), the fourth valve core (5) is provided with a cavity (51) for accommodating the second valve core (2) and the third valve core (3), the cavity (51) is used to communicate with the through hole (11), an elastic member (52) connected to the second valve core (2) is provided in the cavity (51), the elastic member (52) is used to drive the third valve core (3) on the second valve core (2) to abut against the first valve core (1) and provide contact stress, so that the third valve core (3) is sealed and connected to the first valve core (1).

13. A mass flow meter, characterized in that: The invention comprises a mass flow body and a valve core unit according to any one of claims 1 to 12, wherein the valve core unit is mounted on the mass flow body.

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