two-stage pressure reducing valve

Abstract

The application provides a two-stage pressure reducing valve, which comprises a shell, a first inner cavity and a second inner cavity in the shell and in fluid communication through an intermediate passage, a gas inlet passage and a gas outlet passage, the gas inlet passage being in fluid communication with the first inner cavity, and the gas outlet passage being in fluid communication with the second inner cavity; a first valve assembly contained in the first inner cavity and configured to reduce the pressure of gas from the gas inlet passage and deliver the gas to the intermediate passage; and a second valve assembly contained in the second inner cavity and configured to reduce the pressure of gas from the intermediate passage and deliver the gas to the gas outlet passage. The two-stage pressure reducing valve can improve the reliability of the pressure reducing valve and prolong the service life of the pressure reducing valve.

Description

Technical Field

[0001] This application relates to a pressure reducing valve, and more particularly to a pressure reducing valve for reducing outlet gas pressure in a gas supply line with a large pressure difference. Background Technology

[0002] Pressure reducing valves (also known as pressure regulating valves) are widely used in various gas supply pipelines. They typically regulate gas flow by controlling the opening of an internal valve element, thereby adjusting the higher inlet pressure to a lower outlet pressure and maintaining the outlet pressure within a stable range. In pipelines with significant pressure differences, such as hydrogen supply lines for fuel cells, where the hydrogen storage tank pressure can reach over 35 MPa, while the normal operating pressure of hydrogen for the proton exchange membrane of a fuel cell is 0.1 to 0.2 MPa, a pressure reduction process is necessary.

[0003] Existing pressure-reducing valves (e.g., piston-type pressure-reducing valves) typically utilize the contact and separation between the valve core and valve seat surfaces to achieve opening and closing, and use a spring to adjust the opening degree to achieve pressure reduction. In applications where the outlet gas pressure may vary significantly, the pressure-reducing valve spring is usually adjustable. Therefore, by adjusting the spring force, changes in outlet gas pressure can be regulated to maintain the set outlet gas pressure as much as possible. However, this adjustment is difficult to adapt to changes in outlet gas pressure in a timely manner, and it also requires the installation of an adjustment device on the pressure-reducing valve body, leading to reliability issues. Furthermore, existing technologies also employ two pressure-reducing valves in series to adapt to the outlet pressure; however, these series solutions require corresponding piping connections, resulting in installation, sealing, and maintenance problems.

[0004] Furthermore, for a single pressure-reducing valve, under no gas pressure load, the valve core and seat of an existing pressure-reducing valve maintain their maximum opening under the action of a spring. Therefore, in the initial stage of high-pressure gas entry, the instantaneous high pressure of the gas immediately acts on the moving parts, applying significant stress to them. After prolonged operation, valve core movement, gas pressure, and thermal loads cause wear, fatigue, aging, and deformation of the sealing rings, leading to a degradation of the sealing function. The instantaneous high pressure in the initial stage may cause gas leakage or increase the risk of gas leakage, thus affecting the service life of the pressure-reducing valve and potentially posing safety hazards.

[0005] It should be noted that, apart from the fuel cell field, the same problem exists in other fields that use pressure reducing valves to control gas supply, such as the petroleum, chemical, pharmaceutical, and food industries.

[0006] Therefore, an improved pressure reducing valve is needed to enhance its reliability. Summary of the Invention

[0007] The purpose of this application is to provide an improved pressure reducing valve to overcome at least one of the aforementioned technical problems existing in the prior art.

[0008] Therefore, according to one aspect of this application, a two-stage pressure reducing valve is provided, comprising: a housing, wherein the housing has a first inner cavity and a second inner cavity fluidly connected through an intermediate channel, a gas inlet channel and a gas outlet channel, the gas inlet channel being fluidly connected to the first inner cavity and the gas outlet channel being fluidly connected to the second inner cavity; a first valve assembly, the first valve assembly being housed in the first inner cavity and configured to reduce the pressure of gas from the gas inlet channel and deliver it to the intermediate channel; and a second valve assembly, the second valve assembly being housed in the second inner cavity and configured to reduce the pressure of gas from the intermediate channel and deliver it to the gas outlet channel.

[0009] The two-stage pressure reducing valve of this application can achieve two-stage pressure reduction through two valve assemblies in the same housing, thereby improving the reliability of the pressure reducing valve and extending its service life. Attached Figure Description

[0010] Exemplary embodiments of this application will now be described in detail with reference to the accompanying drawings. It should be understood that the embodiments described below are for illustrative purposes only and are not intended to limit the scope of this application. In the accompanying drawings:

[0011] Figure 1 This is a schematic cross-sectional view of a two-stage pressure reducing valve according to an embodiment of this application;

[0012] Figure 2 It is in working condition. Figure 1 A schematic cross-sectional view of the two-stage pressure reducing valve shown;

[0013] Figure 3 yes Figure 2 The diagram shows the force analysis of the valve core of the two-stage pressure reducing valve. Detailed Implementation

[0014] Preferred embodiments of this application are described in detail below with reference to examples. In the embodiments of this application, a secondary pressure reducing valve for a hydrogen supply system is used as an example for description. However, those skilled in the art should understand that these exemplary embodiments do not imply any limitation on this application. Furthermore, features in the embodiments of this application can be combined with each other unless otherwise specified. In different drawings, the same components are indicated by the same reference numerals, and other components are omitted for brevity, but this does not mean that the secondary pressure reducing valve of this application cannot include other components. It should be understood that the dimensions, proportions, and number of components in the drawings are not intended to limit this application.

[0015] The following referenceFigure 1 To describe the secondary pressure reducing valve of this application. For example... Figure 1 As shown, the secondary pressure reducing valve of this application includes: a housing 100, which has a first inner cavity 14 and a second inner cavity 74 fluidly connected through an intermediate channel 50, as well as a gas inlet channel 11 and a gas outlet channel 62, wherein the gas inlet channel 11 is fluidly connected to the first inner cavity 14, and the gas outlet channel 62 is fluidly connected to the second inner cavity 74; a first valve assembly 1, as shown in the figure. Figure 1 As shown in the dashed box on the right, it is housed in the first inner cavity 14 and configured to depressurize the gas from the gas inlet channel 11 and deliver it to the intermediate channel 50; and the second valve assembly 2, as shown in the figure. Figure 1 As shown in the dashed box on the left, it is housed in the second inner cavity 74 and configured to depressurize the gas from the intermediate channel 50 and deliver it to the gas discharge channel 62.

[0016] like Figure 2 As shown, high-pressure gas (such as gas from gas inlet channel 11) Figure 2 (As shown by the solid arrow in the image) First, it enters the first valve assembly 1, that is, the first inner cavity 14, and becomes an intermediate pressure gas (such as...) through the pressure reduction of the first valve assembly 1. Figure 2 (As shown by the shaded arrow in the image), the gas is output to the channel inlet 12 of the intermediate channel 50. Then, the gas at intermediate pressure enters the second valve assembly 2 through the channel outlet 61 of the intermediate channel 50, that is, it enters the second inner cavity 74, and becomes low-pressure gas (as shown by the pressure reduction of the second valve assembly 2) through the pressure reduction of the second valve assembly 2. Figure 2 (As shown by the hollow arrow in the diagram), the gas is output to the gas exhaust channel 62, thereby providing it to the next device (e.g., the reaction chamber of a fuel cell).

[0017] By forming two valve assemblies within the same housing, the installation and connection of related components are avoided, thus improving reliability. Furthermore, through a two-stage pressure reduction between the gas pressure in the gas inlet channel 11 and the gas outlet channel 62, the first valve assembly 1 outputs gas at an intermediate pressure. This intermediate-pressure gas is then delivered to the second valve assembly 2, from which a reduced-pressure gas is output. This two-stage pressure reduction reduces the pressure shock experienced by each valve assembly, thereby mitigating damage to the components and extending their service life.

[0018] It should be pointed out that, in Figure 1In the illustrated embodiment, the first valve assembly 1 and the second valve assembly 2 are different valve assemblies, wherein the first valve assembly 1 is the valve assembly according to the embodiment of this application, and the second valve assembly 2 is a conventional piston-type pressure reducing valve assembly. However, according to the concept of this application, the two valve assemblies can be the same or different valve assemblies. For example, both valve assemblies can be conventional piston-type pressure reducing valve assemblies, and by forming them within the same housing, reliability and service life can also be improved. Due to Figure 1 The second valve assembly 2 is shown as a conventional valve assembly, and its structure will not be described in detail here. Of course, it can also be combined with... Figure 1 and 2 Conversely, as shown, the first valve assembly 2 is a valve assembly according to an embodiment of this application, while the second valve assembly 1 is a conventional valve assembly, or both valve assemblies are valve assemblies according to an embodiment of this application.

[0019] The valve assembly according to the embodiments of this application, namely Figure 1 and 2 The first valve assembly shown is an improvement proposed to enhance the reliability and extend the service life of the valve assembly.

[0020] like Figure 1 and 2 As shown, the first valve assembly 1 of the secondary pressure reducing valve of this application includes a valve core 20 and a spring 30. The valve core 20 is housed in a first inner cavity 14, and the outer surface of the valve core 20 is configured to be hermetically movable along the inner surface of the first inner cavity 14. The valve core 20 includes a first end and a second end opposite to the first end. Figure 1 In this configuration, the first end of the valve core 20 is the lower end. A spring 30 is housed in a first spring chamber 21 formed in the housing 100 and applies a spring force to the valve core 20. The first inner cavity 14 receives gas through a first inlet channel and outputs gas through a first outlet channel. Figure 1 and 2 In the embodiment shown, the first inlet channel of the first valve assembly 1 is the gas inlet channel 11 of the housing 100, and the first outlet channel of the first valve assembly 1 is the channel inlet 12 of the intermediate channel 50.

[0021] like Figure 1 and 2As shown, a valve seat 40 is provided in the first inner cavity 14, and the valve seat 40 is configured to face the first end of the valve core 20. The first inlet channel is in fluid communication with the first inner cavity 14 through the first through hole 41 of the valve seat 40, wherein the cross-sectional area of ​​the first through hole 41 is smaller than the cross-sectional area of ​​the first inlet channel (i.e., the gas inlet channel 11). Thus, in the initial stage when gas is first introduced, the high-pressure gas entering from the first inlet channel is restricted by the first through hole 41, resulting in a throttling effect, and enters the first inner cavity 14 at a limited mass flow rate, and pushes the valve core 20 to move within the first inner cavity 14 with the limited gas pressure. Accordingly, the acceleration of the related components that exert force on the valve core 20 can be reduced, for example, the spring 30; and the limited gas pressure and acceleration act on, for example, the sealing ring (described below), making its deformation during movement smaller and reducing the risk of leakage.

[0022] To ensure that the first valve assembly provides a relatively stable output air pressure under different mass flow rates during normal operation, such as Figure 2 As shown, in the first valve assembly 1, the valve core 20 is configured such that when the valve core 20 moves within the first inner cavity 14 under pressure from the first inlet channel (i.e., gas inlet channel 11), the effective throttling area between the first end of the valve core 20 and the valve seat 40 decreases with increasing mass flow rate into the first inlet channel (which is related to the gas pressure and effective throttling area of ​​the first inlet channel, as will be further described below), and increases with decreasing mass flow rate into the first inlet channel. Figure 2 In this context, the effective throttling area is the cylindrical area defined by the gas throttling region formed between the first end of the valve core 20 and the valve seat 40. Since the size of the gas throttling region is determined by the smaller of the effective force-bearing area of ​​the first end of the valve core 20 and the effective force-bearing area of ​​the end face of the valve seat 40, and the distance between the first end of the valve core 20 and the valve seat 40, and since the effective force-bearing areas of the first end of the valve core 20 and the end face of the valve seat 40 remain constant, the effective throttling area can be schematically represented by the distance between the first end of the valve core 20 and the valve seat 40. Figure 1 and 2In the diagram, the first end of the valve core 20 is shown with a blind hole and a chamfer. The effective force-bearing area of ​​the first end of the valve core 20 is the effective force-bearing area of ​​the chamfered end face (which includes the cross-sectional area of ​​the blind hole). However, the first end of the valve core 20 may not include the blind hole, and may also be an end face without a chamfer, or with rounded corners, or with various other surface features (e.g., protrusions or recesses). Since various formulas for representing and calculating the effective throttling area exist in the prior art, they will not be elaborated here. When the mass flow rate through the first valve assembly is stable, the effective throttling area of ​​the first valve assembly 1 decreases when the gas pressure entering from the first inlet channel increases, and increases when the gas pressure entering from the first inlet channel decreases. The gas pressure in the first outlet channel increases or decreases, but eventually stabilizes within a defined range.

[0023] The relationship between the air pressure in the first inlet channel and the effective throttling area can be further explained using the following formula.

[0024]

[0025] Where Q represents the mass flow rate, A throttle R represents the effective area, R represents the ideal gas constant, and T represents the effective area. in The temperature of the first entering channel is represented by k, and the adiabatic coefficient is represented by P. in This represents the air pressure in the first inlet channel. From the above formula, it can be seen that when the mass flow rate Q is approximately constant, when the air pressure P in the first inlet channel... in When the area increases, the effective throttling area A throttle Decrease, and conversely, increase when the air pressure P entering the first channel increases. in When reduced, the effective throttling area A throttle Increase.

[0026] exist Figure 2 In the diagram, solid arrows indicate the path of high-pressure gas, while shaded arrows indicate the path of gas with reduced pressure. How the effective throttling area between the first end of valve core 20 and valve seat 40 changes with the mass flow rate and gas pressure of the first inlet channel will be discussed in detail below. Figure 2 and 3 Further description.

[0027] According to an embodiment of this application, the first valve assembly 1 includes a first sealing ring 51 and a second sealing ring 52 disposed along the longitudinal direction of the valve core 20 on the outer surface of the valve core 20, thereby defining a spring chamber 21 for accommodating the spring 30 by the two sealing rings. The spring chamber 21 is provided with a vent 13 for communicating with the surrounding atmosphere. Figure 1 and 2As shown, the vent 13 is located between the first sealing ring 51 and the second sealing ring 52.

[0028] The valve core 20 is provided with an internal channel 24. The first inner cavity 14 and the internal channel 24 are in fluid communication through a second through hole 22 provided on the side wall of the valve core 20. The second through hole 22 is provided between the first end of the valve core 20 and the first sealing ring 51. Therefore, high-pressure gas (such as...) entering from the first inlet channel... Figure 2 (As indicated by the solid arrow) After passing through the first through hole 41, it enters the first inner cavity 14, and enters the inner channel 24 through the second through hole 22 at a reduced air pressure (i.e., the air pressure of the first discharge channel).

[0029] The internal passage 24 forms an opening 23 at the second end of the valve core (20) opposite to the first end. Therefore, gas (such as gas) entering the internal passage 24 through the second through-hole 22... Figure 2 (As indicated by the shaded arrow) can flow to the second end of the valve core 20 to generate air pressure at the second end. It should be noted that the first through hole 41, the second through hole 22, and the opening 23 can be one or more, and their shape and position can be specifically designed as needed.

[0030] like Figure 1 and 2 As shown, the spring 30 is disposed in the spring chamber 21 between the first sealing ring 51 and the second sealing ring 52. Thus, the spring 30 is situated within a space formed by the first sealing ring 51 and the second sealing ring 52, which isolates it from the incoming gas. Figure 1 and 2 In this configuration, spring 20 is disposed between the first and second ends of valve core 20, and spring chamber 21 is shown to be hermetically isolated from the first inner cavity 14. However, spring 30 may also be disposed at the first end of valve core 20, i.e. Figure 1 The lower end shown, or located at the second end of the valve core 20, i.e. Figure 1 The upper end is shown. Therefore, the spring 30 can be configured in various ways, and correspondingly, the spring chamber 21 can also be in fluid communication with the first inner cavity 14, as long as it can maintain the balance between the air pressure of the first inlet channel and the first outlet channel when the mass flow rate and air pressure of the first inlet channel change during operation.

[0031] Regarding the balance between the air pressure in the first inlet channel, the air pressure in the first outlet channel, and the spring force of the first valve assembly 1 during operation, the following formula can be used and referenced. Figure 3 Let me explain.

[0032] F1 = F2 + F spring +F3+F4 (1)

[0033] F1 = P out×A1 (2)

[0034] F2=P0×A2 (3)

[0035] F3 = P out ×A3 (4)

[0036] F4 = P in ×A4 (5)

[0037] Wherein, F1 is the pressure of the gas in the first discharge channel of the first valve assembly acting on the second end of the valve core 20, and P out A1 is the gas pressure of the first discharge channel of the first valve assembly, and A1 is the effective force-bearing area of ​​the second end of the valve core 20 (e.g., in...). Figure 3 In the embodiment shown, A1 is the area of ​​a circle with the inner diameter of the cavity contacted by the second sealing ring 52 as its diameter; F2 is the atmospheric pressure exerted on the valve core 20 by the surrounding environment; P0 is atmospheric pressure; and A2 is the effective force-bearing area of ​​the valve core 20 that withstands atmospheric pressure (e.g., in...). Figure 3 In the illustrated embodiment, A2 is the area of ​​the ring whose outer diameter is the inner diameter of the cavity contacted by the second sealing ring 52; F3 is the pressure of the gas in the first discharge channel of the first valve assembly acting on the first end of the valve core 20; and A3 is the effective force-bearing area near the first end of the valve core 20 (e.g., in...). Figure 3 In the embodiment shown, A3 is the area of ​​the ring whose outer diameter is the inner diameter of the cavity contacted by the first sealing ring 51; F4 is the pressure of the gas in the first inlet channel of the first valve assembly acting on the first end of the valve core 20; P in A4 is the gas pressure of the first inlet channel of the first valve assembly, and A4 is the effective force-bearing area of ​​the first end of the valve core 20 (e.g., in...). Figure 3 In the embodiment shown, A4 is the area of ​​a circle with the diameter of the cylinder at the first end of the valve core 20 as its diameter; F spring This is the elastic force of spring 30 acting on valve core 20. In the operating state of the first valve assembly, the pressure on valve core 20 in its longitudinal direction varies with the air pressure changes in the first inlet channel and the first outlet channel, and tends to maintain equilibrium. The above only considers the main pressure borne by valve core 20 in the longitudinal direction, and depending on the specific structure of valve core 20, there may be more or less force. For example, in... Figure 3 In the illustrated embodiment, for the purpose of simplification, the frictional forces acting on the first sealing ring 51 and the second sealing ring 52 are not listed. Of course, if a more accurate calculation is required, the aforementioned frictional forces can be included in the calculation formula.

[0038] From the above formulas (1)-(5), we can deduce that P out = (F2+F spring+F3+F4) / A1. Therefore, when the mass flow rate and air pressure of the first inlet channel of the first valve assembly change, the valve core 20 is moved by changing the spring force of the spring 30, thereby keeping the air pressure of the first outlet channel of the first valve assembly essentially within the defined range. For example, when the air pressure of the first inlet channel of the first valve assembly 1 increases, the force F4 increases, and correspondingly P out Increase, and based on the above formula, force F spring The pressure also increases, while the valve core 20 moves downward, reducing the effective throttling area S, and through a dynamic process, the air pressure in the first discharge channel returns to stability. Conversely, when the air pressure in the first inlet channel of the first valve assembly decreases, the force F4 decreases, and correspondingly P... out Decrease, and based on the above formula, force F spring The pressure also decreases, while the valve core 20 moves upward, increasing the effective throttling area S, and through a dynamic process, the air pressure in the first discharge channel is restored to stability.

[0039] In the initial stage of operation of the first valve assembly 1, since there is no pneumatic load from the first inlet channel, under the action of the spring 30, the second end of the valve core 20 abuts against the housing 100, so that the first end of the valve core 20 maintains the maximum distance between it and the valve seat 40. When high-pressure gas enters the first through hole 41 of the valve seat 40 through the first inlet channel (i.e., gas inlet channel 11) and is discharged, the throttled gas enters the first inner cavity 14, and flows into the first discharge channel of the first valve assembly 1 (i.e., the channel inlet 12 of the intermediate channel 50) at a reduced pressure through the throttling area formed between the first end of the valve core 20 and the valve seat 40, and also flows into the internal channel 24 of the valve core 20, such as... Figure 2 The arrows are shown in shaded lines. Then, due to the balance between the various forces described above, the air pressure in the first discharge channel causes the valve core 20 to gradually move downwards, reducing the effective throttling area and simultaneously lowering the air pressure in the first discharge channel, gradually achieving the pressure balance described above. Therefore, in the initial stage, the instantaneous high-pressure gas entering the first inner cavity 14 acts on the valve core 20 with reduced pressure, mitigating the impact on the valve core 20 and thus reducing its acceleration. This reduces the deformation of the first sealing ring 51 and the second sealing ring 52 during movement and decreases the stress they experience, reducing the risk of leakage.

[0040] Furthermore, when the first valve assembly 1 is in operation, and the air pressure in the first discharge channel increases to a predetermined value, according to the aforementioned pressure balance relationship, the first end of the valve core 20 abuts against the valve seat 40 to seal the first through hole 41, preventing high-pressure gas from continuing to enter the first inner cavity 14. To provide a more effective seal, the first end of the valve core 20 is provided with an annular protrusion, which can more effectively abut against the valve seat 40 to seal the first through hole 41. Accordingly, the valve seat 40 can be a metal or non-metal plate material, for example, metal materials include carbon steel, alloy steel, copper, aluminum, titanium, etc., and non-metal materials include rubber, plastic, etc.

[0041] As previously described, the second valve assembly 2 can also adopt the same structure as the first valve assembly 1. In this case, the first inlet channel of the second valve assembly 2 is the outlet 61 of the intermediate channel 50, and the first outlet channel of the second valve assembly 2 is the gas outlet channel 62 of the housing 100. Based on the working principle described above for the first valve assembly 1, the second valve assembly 2 can also achieve pressure reduction and pressure stabilization functions. Therefore, the two-stage pressure reducing valve, which includes two valve assemblies according to embodiments of this application, can reduce the impact on the various components of the valve assembly, thereby improving reliability and extending service life.

[0042] The above is for Figure 1 and 2 The exemplary structure of the two-stage pressure reducing valve shown herein and Figure 3 The force conditions of the valve core 20 shown describe the working process of the secondary pressure reducing valve of this application. However, the valve core 20 may also have different structures, and the spring 30 may also have different arrangements. Those skilled in the art can configure and calculate accordingly based on the specific valve assembly structure, which will not be elaborated here.

[0043] According to the embodiments of this application, by allowing high-pressure gas to pass through a two-stage valve assembly disposed in the same housing and enter the inner cavity of the housing through a through hole with a small cross-sectional area, the impact on components such as the valve core of the valve assembly can be reduced, thereby improving reliability.

[0044] The present application has been described in detail above with reference to specific embodiments. Obviously, the above description and the embodiments shown in the accompanying drawings should be understood as exemplary and not as limiting the present application. For example, in a preferred embodiment, the present application has been described using a two-stage pressure reducing valve for the field of fuel cells as an example. However, the present application can be applied not only in the field of fuel cells, but also in any field where pressure reducing valves are needed to control gas pressure regulation. Those skilled in the art can make various modifications or variations to the present application without departing from its spirit, and such modifications or variations do not depart from the scope of the present application.

Claims

1. A two-stage pressure reducing valve characterized by comprising: The secondary pressure reducing valve comprises: a housing (100) having a first inner cavity (14) and a second inner cavity (74) in fluid communication through an intermediate passage (50), and a gas inlet passage (11) in fluid communication with the first inner cavity (14) and a gas outlet passage (62) in fluid communication with the second inner cavity (74); a first valve assembly (1) housed in the first inner cavity (14) and configured to reduce and deliver gas from the gas inlet passage (11) to the intermediate passage (50); a second valve assembly (2) housed in the second inner cavity (74) and configured to reduce and deliver gas from the intermediate passage (50) to the gas outlet passage (62); wherein at least one of the first valve assembly (1) and the second valve assembly (2) comprises: a valve core (20) housed in a respective inner cavity of the housing (100), an outer surface of the valve core (20) being configured to move airtightly along an inner surface of the respective inner cavity, the valve core (20) comprising a first end and a second end opposite to the first end; a spring (30) housed in a spring chamber (21) formed in the housing (100) and exerting a spring force on the valve core (20); wherein the respective inner cavity receives gas through a first inlet passage and outputs gas through a first outlet passage, a valve seat (40) is provided in the respective inner cavity, the valve seat (40) being arranged opposite to the first end of the valve core (20), the first inlet passage is in fluid communication with the respective inner cavity through a first through hole (41) of the valve seat (40), wherein a cross-sectional area of the first through hole (41) is smaller than a cross-sectional area of the first inlet passage; wherein the valve core (20) is configured to seal the first through hole (41) by the first end of the valve core (20) abutting against the valve seat (40) when a gas pressure of the first outlet passage reaches a predetermined value.

2. The two-stage pressure reducing valve according to claim 1, characterized by The valve core (20) is configured such that, when the valve core (20) moves in the respective inner cavity due to a gas pressure from the first inlet passage, an effective throttling area between the first end of the valve core (20) and the valve seat (40) decreases as a mass flow rate into the first inlet passage increases, and increases as the mass flow rate into the first inlet passage decreases.

3. The two-stage pressure reducing valve according to claim 1, characterized by A pressure borne by the valve core (20) in a longitudinal direction thereof varies with gas pressures of the first inlet passage and the first outlet passage, and tends to be balanced.

4. The two-stage pressure reducing valve according to claim 3, characterized by The valve seat (40) is a metal or non-metal plate-like material.

5. The two-stage pressure reducing valve according to claim 1, wherein The first end of the valve core (20) is provided with an annular protrusion.

6. The two-stage pressure reducing valve according to claim 1, wherein A first seal ring (51) and a second seal ring (52) are provided on an outer surface of the valve core (20) in a longitudinal direction of the valve core (20), and the spring chamber (21) is defined by the first seal ring (51) and the second seal ring (52), and the spring chamber (21) is provided with a vent hole (13) for communicating with the atmosphere of the surrounding environment.

7. The two-stage pressure reducing valve according to claim 6, characterized by The valve core (20) is provided with an internal passage (24), and the corresponding internal cavity and the internal passage (24) are in fluid communication through a second through hole (22) provided on a side wall of the valve core (20), and the second through hole (22) is arranged between the first end of the valve core (20) and the first seal ring (51).

8. The two-stage pressure reducing valve according to claim 7, characterized by The internal passage (24) forms an opening (23) at a second end of the valve core (20) opposite to the first end.

9. The two-stage pressure reducing valve according to claim 1, wherein The first entering passage of the first valve assembly (1) is a gas entering passage (11) of the housing (100), and the first discharging passage of the first valve assembly (1) is a passage inlet (12) of the intermediate passage (50); The first entering passage of the second valve assembly (2) is a passage outlet (61) of the intermediate passage (50), and the first discharging passage of the second valve assembly (2) is a gas outlet of the housing (100).

Images