A solenoid valve

Abstract

This utility model discloses an electromagnetic valve: a housing, a stationary iron core, and a moving iron core. One end face of the stationary iron core facing the moving iron core and the other end face of the moving iron core facing the stationary iron core have a first straight hole, and the other has a second straight hole. A spring assembly includes a first spring and a second spring sleeved outside the first spring. One end of the first spring is connected to the first straight hole, and the other end abuts against the inner bottom wall of the second straight hole. The first spring causes the moving iron core to always have a tendency to move away from the stationary iron core. One end of the second spring is connected to the second straight hole, and the other end extends axially out of the second straight hole and has a free gap with either the stationary or moving iron core. When the moving iron core moves towards the stationary iron core until the free gap disappears, the second spring is compressed. This electromagnetic valve has a simple processing technology, low production cost, and low product defect rate.

Description

Technical Field

[0001] This application relates to the field of control valve technology for automotive air suspension systems, specifically to a solenoid valve. Background Technology

[0002] Air suspension is a device that controls the suspension height of a vehicle through air pressure. In an automotive air suspension system, the air suspension control solenoid valve is an important component. Its main function is to control the inflation or deflation of air according to different road conditions, thereby adjusting the vehicle's suspension height and improving the vehicle's suspension performance and driving stability.

[0003] Most air suspension control solenoid valves in related technologies are bidirectional airflow solenoid valves. Their structure includes a valve body and an electromagnetic drive section. The valve body includes a housing, a stationary iron core, a moving iron core, a valve core, and a valve seat. The moving iron core slides axially within the housing, and a spring is provided between the moving and stationary iron cores. The valve core is connected to the moving iron core and can move axially with the moving iron core to open or close the valve seat. The electromagnetic drive section includes an electromagnetic coil mounted on the outer peripheral wall of the housing. When the electromagnetic coil is de-energized, the electromagnetic force disappears, and the restoring force of the spring causes the moving iron core to drive the valve core to close the valve seat. When the electromagnetic coil is energized, it generates electromagnetic force, causing the moving iron core to overcome the spring force and move towards the stationary iron core to open the valve seat.

[0004] It's easy to understand that the spring's stiffness is typically designed so that it can overcome the force exerted by the gas on the solenoid valve to open it and close it with a small preload. During operation, the instantaneous pressure fluctuations of the gas create significant pressure differences, so the spring must consistently provide the force necessary to reliably close the solenoid valve at higher operating pressures. This necessitates high spring stiffness, which in turn requires the solenoid valve's magnetic circuit to provide a large electromagnetic force capable of overcoming the spring force to open the valve. Furthermore, the closer the moving iron core is to the stationary iron core, or the smaller the distance between them, the greater the electromagnetic force, resulting in significant impact noise when the moving and stationary iron cores come into contact.

[0005] To reduce the impact noise between the moving and stationary iron cores, related solenoid valves incorporate a pad made of soft material on the end face of the moving iron core closest to the stationary iron core. This pad abuts against the end of the stationary iron core when the valve core opens, reducing the impact force and noise. Examples of such solenoid valves can be found in prior Chinese patent applications such as CN215721142U and CN221504116U.

[0006] The solenoid valves mentioned above have the following defects in actual use: the soft pads used to reduce the impact noise between the moving iron core and the stationary iron core need to be grooved on the moving iron core or the stationary iron core, and then rubber material is filled into the groove through a mold. The filling material is cured at high temperature to form the pads. The process is complicated and the production cost is high. Moreover, the difference in the curing process precision of the rubber material results in uneven thickness of the pads and a high product defect rate. Utility Model Content

[0007] The technical problem to be solved by this application is to overcome the defects of the above-mentioned related technologies and provide a solenoid valve with simple processing technology, low production cost and low product defect rate.

[0008] The technical solution of this application is to provide a solenoid valve having the following structure: including...

[0009] The housing and the stationary iron core and the moving iron core located inside the housing, wherein one of the end face of the stationary iron core facing the end of the moving iron core and the end face of the moving iron core facing the end of the stationary iron core are provided with a first straight hole, and the other is provided with a second straight hole coaxial with the first straight hole;

[0010] A spring assembly includes a first spring and a second spring sleeved outside the first spring. One end of the first spring is connected to the first straight hole, and the other end abuts against the inner bottom wall of the second straight hole. The first spring causes the moving iron core to always have a tendency to move away from the stationary iron core. One end of the second spring is connected to the second straight hole, and the other end extends axially out of the second straight hole and has a free gap with the stationary iron core or the moving iron core. When the moving iron core moves towards the stationary iron core until the free gap disappears, the second spring is compressed.

[0011] In some embodiments, the first straight hole is disposed on the stationary iron core and the second straight hole is disposed on the moving iron core, and when the solenoid valve is closed, the second spring has the free gap between the end near the stationary iron core and the stationary iron core.

[0012] In some embodiments, the diameter of the second straight hole is larger than the diameter of the first straight hole.

[0013] In some embodiments, one end of the first spring is radially limited within the first straight hole, and one end of the second spring is radially limited within the second straight hole.

[0014] In some embodiments, the stiffness of the second spring is greater than the stiffness of the first spring.

[0015] In some embodiments, the second spring has fewer coils than the first spring.

[0016] In some embodiments, the wire diameter of the second spring is greater than or equal to the wire diameter of the first spring.

[0017] In some embodiments, when the moving iron core moves toward the stationary iron core to a fully engaged state, the second spring is fully compressed and does not extend out of the second straight hole.

[0018] In some embodiments, a valve seat is sealed to one end of the housing away from the stationary iron core, and a valve core is connected to one end of the moving iron core away from the stationary iron core. A first vent is provided at the center of the valve seat, and a second vent is provided on the outer side wall of the housing near the valve seat, which communicates with the first vent. Under the elastic force of the first spring, the valve core and the valve seat abut against each other to seal, thereby disconnecting the first vent from the second vent.

[0019] In some embodiments, the outer circumferential wall of the moving iron core is provided with an annular groove.

[0020] In summary, the solenoid valve proposed in this application has the following advantages compared with related technologies:

[0021] Firstly, this solenoid valve incorporates a spring assembly between the stationary and moving iron cores. This assembly includes a nested first spring and a second spring. The first spring connects to a first straight hole, and the second spring connects to a second straight hole. The first spring consistently provides the driving force for the moving iron core to close the valve. The portion of the second spring extending beyond the second straight hole has a free gap with either the stationary or moving iron core. When the moving iron core moves towards the stationary iron core until the free gap disappears, the second spring is compressed. That is, during the process of the moving iron core moving towards the stationary iron core to open the solenoid valve, the gap between the moving and stationary iron cores decreases, increasing the electromagnetic force and causing the moving iron core to quickly attract towards the stationary iron core. However, the elastic force of the second spring effectively buffers the impact force during this attraction, resulting in good noise reduction. This solenoid valve only requires the addition of a second spring that can be connected within the second straight hole to effectively reduce the impact noise during the attraction of the moving and stationary iron cores. Its manufacturing process is simple and its production cost is low. Furthermore, the installed second spring has lower requirements for manufacturing precision, resulting in a low defect rate during the production of this solenoid valve.

[0022] Secondly, when the solenoid valve is open, only the first spring is compressed under the action of electromagnetic force. At this time, only a small electromagnetic force is needed to quickly open the solenoid valve, thereby improving the response speed of the solenoid valve. When the solenoid valve switches from the open state to the closed state, that is, when the electromagnetic force disappears, the elastic force of the first spring and the second spring is applied to the moving iron core at the same time. This not only gives the moving iron core a large kinetic energy, but also effectively resists the force exerted on the valve core by the external gas, thereby achieving the purpose of quickly closing the valve and improving the response speed of the solenoid valve. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of a solenoid valve according to some embodiments of this application.

[0024] Figure 2 This is a three-dimensional cross-sectional view of a solenoid valve according to some embodiments of this application.

[0025] Figure 3 This is a cross-sectional view of a solenoid valve in a closed state according to some embodiments of this application.

[0026] Figure 4 This is a cross-sectional view of a solenoid valve in an open state according to some embodiments of this application.

[0027] Explanation of reference numerals in the attached figures:

[0028] 1. Valve body; 100. Housing; 101. Stationary iron core; 102. Moving iron core; 103. First straight hole; 104. Second straight hole; 105. Valve core; 106. Valve seat; 107. First vent; 108. Second vent; 109. Valve port; 110. Annular groove; 111. Connector; 2. Spring assembly; 200. First spring; 201. Second spring; H. Free clearance. Detailed Implementation

[0029] First, those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the embodiments of this application and are not intended to limit the scope of protection of the embodiments of this application. Those skilled in the art can make adjustments as needed to adapt to specific application scenarios.

[0030] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application based on the specific circumstances.

[0031] In the embodiments of this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0032] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0033] like Figures 1-4 As shown in the figure, this application discloses a solenoid valve for use in an automotive air suspension system. The solenoid valve includes a valve body 1 and an electromagnetic drive part. The valve body 1 includes a housing 100, a valve seat 106, a valve core 105, and a stationary iron core 101 and a moving iron core 102 located within the housing 100. The stationary iron core 101 is sealed to one end of the housing 100 and extends at least partially into the housing 100. The moving iron core 102 is axially slidably fitted within the housing 100, and a spring is provided between the moving iron core 102 and the stationary iron core 101. Component 2; Valve seat 106 is sealed to the end of housing 100 away from stationary iron core 101, and a connector 111 is formed at the end of moving iron core 102 away from stationary iron core 101. Valve core 105 is connected to connector 111. A first vent 107 is provided at the center of valve seat 106, and a second vent 108 communicating with the first vent 107 is provided on the outer side wall of housing 100 near valve seat 106. The electromagnetic drive part includes an electromagnetic coil disposed on the outer side wall of housing 100 and an electrical connector electrically connected to the electromagnetic coil.

[0034] Understandably, when the electromagnetic coil is de-energized, the electromagnetic force disappears, and the moving iron core 102 moves axially away from the stationary iron core 101 under the elastic force of the spring assembly 2, closing the valve port 109 at the inner end of the valve seat 106, thereby disconnecting the first vent 107 from the second vent 108. At this time, the solenoid valve is in the closed state. When the electromagnetic coil is energized, it generates electromagnetic force, and the moving iron core 102 overcomes the elastic force of the spring assembly 2, moving axially towards the stationary iron core 101 and opening the valve port 109 at the inner end of the valve seat 106, connecting the first vent 107 with the second vent 108. At this time, the solenoid valve is in the open state.

[0035] In this embodiment, the working medium of the solenoid valve is gas. Both the first air port 107 and the second air port 108 can allow air to enter and exit each other, such as air entering through the first air port 107 and exiting through the second air port 108; or air exiting through the first air port 107 and entering through the second air port 108. That is, the solenoid valve is a solenoid valve with bidirectional airflow.

[0036] It is easy to understand that during the operation of the solenoid valve, the instantaneous pressure fluctuations of the gas will generate a large pressure difference. Therefore, the spring assembly 2 must always provide a force that can reliably close the solenoid valve under high operating pressure. Correspondingly, the spring assembly 2 needs to have high stiffness. However, this means that the magnetic circuit of the solenoid valve must provide a large electromagnetic force that can overcome the spring force to open the solenoid valve. Furthermore, due to the magnetic characteristic of the solenoid valve, the closer the moving iron core 102 is to the stationary iron core 101, or the smaller the distance between the moving iron core 102 and the stationary iron core 101, the greater the electromagnetic force. This results in a large impact noise when the moving iron core 102 and the stationary iron core 101 come into contact. In this embodiment, in order to reduce or weaken the impact force and the impact noise generated when the moving iron core 102 and the stationary iron core 101 come into contact, the spring assembly 2 is configured as two parallel springs, namely the first spring 200 and the second spring 201. Specifically, see [link to documentation]. Figure 1 , Figure 2 , Figure 3 and Figure 4As shown, the spring assembly 2 includes a first spring 200 and a second spring 201 sleeved outside the first spring 200; the stationary iron core 101 has a first end face at the end facing the moving iron core 102, and the moving iron core 102 has a second end face at the end facing the stationary iron core 101. The first end face and the second end face are axially opposite each other. A first straight hole 103 is provided at the center of the first end face, which is axially recessed, and a second straight hole 104 is provided at the center of the second end face, which is axially recessed and coaxial with the first straight hole 103. The first spring 200... One end of the spring 200 is connected to the first straight hole 103, and the other end abuts against the inner bottom wall of the second straight hole 104. The first spring 200 causes the moving iron core 102 to always have a tendency to move away from the stationary iron core 101. One end of the second spring 201 is connected to the second straight hole 104, and the other end extends axially out of the second straight hole 104 and has a free gap H between it and the stationary iron core 101. When the moving iron core 102 moves towards the stationary iron core 101 until the free gap H disappears, the second spring 201 is compressed. That is, during the process of the moving iron core 102 moving towards the stationary iron core 101 to open the solenoid valve, the electromagnetic force increases because the gap between the moving iron core 102 and the stationary iron core 101 becomes smaller, causing the moving iron core 102 to quickly attract towards the stationary iron core 101. However, the elastic force of the second spring 201 can effectively buffer the impact force when the moving iron core 102 and the stationary iron core 101 are attracted, thus making its noise reduction effect good. This solenoid valve effectively reduces the impact noise when the moving iron core 102 and the stationary iron core 101 are attracted by simply adding a second spring 201 that can be connected inside the second straight hole 104. Its processing technology is simple and the production cost is low. In addition, the installed second spring 201 has low requirements for processing precision, resulting in a low product defect rate during the production of this solenoid valve.

[0037] Furthermore, in this embodiment, it can be understood that the closer the moving iron core 102 is to the stationary iron core 101, the smaller the gap between them, the greater the electromagnetic force generated by the electromagnetic coil, and the higher the kinetic energy and speed of the moving iron core 102. Since the stiffness of the second spring 201 is greater than that of the first spring 200, when the second spring 201 is compressed, the impact speed of the moving iron core 102 can be reduced, thereby reducing the impact force when the moving iron core 102 and the stationary iron core 101 are fully attracted, thus achieving a good noise reduction effect.

[0038] Accordingly, given that the first spring 200 can overcome the force of the gas on the solenoid valve to open it under a very small preload and can close the solenoid valve, and that the impact noise when the moving iron core 102 and the stationary iron core 101 are fully engaged can be effectively reduced under the action of the second spring 201, the stiffness of the first spring 200 can be set to be smaller, which is beneficial to the rapid opening of the solenoid valve and the miniaturization of its size.

[0039] In the foregoing embodiments, see Figure 3 and Figure 4 As shown, because there is a free gap H between the part of the second spring 201 extending out of the second straight hole 104 and the stationary iron core 101, when the solenoid valve is opened, only the first spring 200 is compressed under the action of electromagnetic force. At this time, only a small electromagnetic force is needed to quickly open the solenoid valve, thereby improving the response speed of the solenoid valve. When the moving iron core 102 moves to the point where the extended part of the second spring 201 abuts against the first end face of the stationary iron core 101, the free gap H disappears. As the moving iron core 102 continues to move closer to the stationary iron core 101, the second spring 201 is compressed. At this time, the first spring 200 and the second spring 201 are connected in parallel and both are compressed, thereby relieving the pressure on the moving iron core 101. 2. The impact force when the solenoid valve is attracted and resisted by the stationary iron core 101; furthermore, when the solenoid valve switches from the open state to the closed state, that is, when the electromagnetic force disappears, the elastic force of the first spring 200 and the second spring 201 is applied to the moving iron core 102 at the same time. In addition, the stiffness of the second spring 201 is greater than that of the first spring 200. The second spring 201 in the compressed state stores more energy, so that the moving iron core 102 has a larger initial kinetic energy. This can effectively overcome the force of the external gas applied to the solenoid valve core 105, which causes the valve core 105 to tend to open, as well as the influence of the residual magnetism of the moving iron core 102, thereby achieving the purpose of fast valve closing and improving the response speed of the solenoid valve.

[0040] Understandably, the moving iron core 102 moves downwards under the combined restoring force of the first spring 200 and the second spring 201, overcoming the force exerted by the gas on the moving iron core 102 away from the valve seat 106. When the downward movement is equal to the compression of the second spring 201, it continues to move downwards, at which point the second spring 201 disengages from the first end face of the stationary iron core 101, and at the instant of disengagement, the restoring force of the second spring 201 disappears. At this time, the restoring force of the first spring 200 alone is actually insufficient to overcome the force exerted by the gas on the moving iron core 102 or the valve core 105. However, the moving iron core 102 obtains a large acceleration and has a large kinetic energy during the initial valve closing process. Therefore, the moving iron core 102 continues to move until the valve core 105 closes the valve port 109 of the valve seat 106 under its own kinetic energy and the force of the first spring 200.

[0041] In the above embodiment, the first straight hole 103 on the first end face of the stationary iron core 101 is a cylindrical blind hole formed by cutting with a drill bit of a single diameter, and the second straight hole 104 on the second end face of the moving iron core 102 is also a cylindrical blind hole formed by cutting with a drill bit of a single diameter. Therefore, its processing technology is simple, processing is convenient, processing time is short, and production cost is low.

[0042] Furthermore, in this embodiment, both the first spring 200 and the second spring 201 are cylindrical helical springs. In other embodiments, the second spring 201 may also be a square helical spring or a conical spring, etc.

[0043] In some embodiments, a second straight hole 104 that is axially recessed may be provided at the center of the first end face of the stationary iron core 101, and a first straight hole 103 that is axially recessed and coaxial with the second straight hole 104 may be provided at the center of the second end face of the moving iron core 102. One end of the first spring 200 is connected to the first straight hole 103, and the other end abuts against the inner bottom wall of the second straight hole 104. One end of the second spring 201 is connected to the second straight hole 104, and the other end extends axially out of the second straight hole 104 and has a free gap H between it and the moving iron core 102. That is, in this embodiment, the first straight hole 103 is provided on the second end face of the moving iron core 102, while the second straight hole 104 is provided on the first end face of the stationary iron core 101.

[0044] It is understandable that in this embodiment, the second spring 201 is sleeved outside the first spring 200, and the inner diameter of the second spring 201 is larger than the outer diameter of the first spring 200. The second straight hole 104 is used to accommodate the second spring 201. If the diameters of the first straight hole 103 and the second straight hole 104 are equal, it will inevitably affect the effective magnetic flux area of ​​the electromagnetic coil to the moving iron core 102. In this embodiment, see... Figure 2 and Figure 3 As shown, the diameter of the second straight hole 104 is larger than that of the first straight hole 103. That is, the diameters of the first straight hole 103 and the second straight hole 104 are set according to the outer diameters of the first spring 200 and the second spring 201, which can effectively reduce the influence of the electromagnetic coil on the effective magnetic flux area of ​​the moving iron core 102.

[0045] Furthermore, in this embodiment, since the first spring 200 and the second spring 201 are arranged in parallel, and the second spring 201 is sleeved on the outside of the first spring 200, in order to avoid the first spring 200 and the second spring 201 affecting the stability of the axial movement of the moving iron core 102 when compressed or released, and to make the connection between the first spring 200 and the second spring 201 more stable and able to be compressed or released smoothly, see [reference needed]. Figure 3 and Figure 4 As shown, one end of the first spring 200 is fitted against the inner wall of the first straight hole 103 and radially limited within the first straight hole 103, while one end of the second spring 201 is fitted against the inner wall of the second straight hole 104 and radially limited within the second straight hole 104. When the moving iron core 102 moves axially, the first spring 200 and the second spring 201 are radially limited, thereby preventing the first spring 200 and the second spring 201 from shifting or tilting, making the axial movement of the moving iron core 102 more stable.

[0046] Understandably, the inner diameter of the second spring 201 is larger than the outer diameter of the first spring 200, and the number of coils in the second spring 201 is less than the number of coils in the first spring 200. This not only ensures that the stiffness of the second spring 201 is greater than that of the first spring 200, but also saves materials and reduces costs.

[0047] Further in this embodiment, see Figure 2 As shown, the wire diameter of the second spring 201 is greater than or equal to that of the first spring 200. That is, the second spring 201 is a thick spring, and the first spring 200 is a thin spring. With this configuration, the first spring 200 can overcome the force of the gas on the solenoid valve to open it under a very small preload and can also close the solenoid valve. At the same time, the stiffness of the first spring 200 can be set to be smaller, which is beneficial to the rapid opening of the solenoid valve.

[0048] It is understandable that when the solenoid valve is open, and the moving iron core 102, under the action of electromagnetic force, overcomes the elastic force of the first spring 200 and the second spring 201 and is completely abutted and attracted to the stationary iron core 101, that is, when the second end face of the moving iron core 102 is completely abutted to the first end face of the stationary iron core 101, even if the force of external high-pressure gas is applied to the moving iron core 102 and high-frequency pressure fluctuations occur, or if the voltage change of the electronic control part causes high-frequency fluctuations in the electromagnetic force, vibration and vibration noise are unlikely to occur between the moving iron core 102 and the stationary iron core 101 due to the abutting and attracted relationship. Therefore, in this embodiment, see Figure 3 and Figure 4 As shown, when the moving iron core 102 moves towards the stationary iron core 101 to the fully engaged state, the second spring 201 is fully compressed and does not extend out of the second straight hole 104; that is, when the second spring 201 is fully compressed, the moving iron core 102 and the stationary iron core 101 abut against each other and are fully engaged. This arrangement avoids the situation where, when the second spring 201 is fully compressed, part of it still extends out of the second straight hole 104, which would prevent the second end face of the moving iron core 102 from completely abutting against the first end face of the stationary iron core 101 or create a gap between the second end face of the moving iron core 102 and the first end face of the stationary iron core 101; moreover, when the solenoid valve switches from the open state to the closed state, the fully compressed second spring 201 can provide the moving iron core 102 with greater kinetic energy, thereby improving the response speed of the solenoid valve.

[0049] Further in this embodiment, see Figure 3 As shown, an annular groove 110 is provided on the outer circumferential wall of the moving iron core 102. The setting of the annular groove 110 reduces the contact area between the moving iron core 102 and the inner wall of the housing 100, thereby making the movement of the moving iron core 102 smoother.

[0050] In the description of the embodiments of this application, it should be noted that the terms "inner" and "outer" and other terms indicating direction or positional relationship are based on the direction or positional relationship shown in the drawings. This is only for the convenience of description and does not indicate or imply that the device or component must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this application.

[0051] In the description of this application, the references to terms such as "an embodiment," "some embodiments," "in this embodiment," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0052] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An electromagnetic valve characterized by comprising: include The housing and the stationary iron core and the moving iron core located inside the housing, wherein one of the end face of the stationary iron core facing the end of the moving iron core and the end face of the moving iron core facing the end of the stationary iron core are provided with a first straight hole, and the other is provided with a second straight hole coaxial with the first straight hole; A spring assembly includes a first spring and a second spring sleeved outside the first spring. One end of the first spring is connected to the first straight hole, and the other end abuts against the inner bottom wall of the second straight hole. The first spring causes the moving iron core to always have a tendency to move away from the stationary iron core. One end of the second spring is connected to the second straight hole, and the other end extends axially out of the second straight hole and has a free gap with the stationary iron core or the moving iron core. When the moving iron core moves towards the stationary iron core until the free gap disappears, the second spring is compressed.

2. The electromagnetic valve according to claim 1, characterized by: The first straight hole is disposed on the stationary iron core and the second straight hole is disposed on the moving iron core. When the solenoid valve is closed, the second spring has the free gap between the end near the stationary iron core and the stationary iron core.

3. The solenoid valve according to claim 2, characterized in that: The diameter of the second straight hole is larger than that of the first straight hole.

4. The solenoid valve according to claim 3, characterized in that: One end of the first spring is radially limited within the first straight hole, and one end of the second spring is radially limited within the second straight hole.

5. The solenoid valve according to claim 1, characterized in that: The stiffness of the second spring is greater than that of the first spring.

6. The solenoid valve according to claim 1, characterized in that: The second spring has fewer coils compared to the first spring.

7. The solenoid valve according to claim 6, characterized in that: The wire diameter of the second spring is greater than or equal to that of the first spring.

8. The solenoid valve according to any one of claims 1 to 7, characterized in that: When the moving iron core moves toward the stationary iron core to a fully engaged state, the second spring is fully compressed and does not extend out of the second straight hole.

9. The solenoid valve according to claim 1, characterized in that: The end of the housing away from the stationary iron core is sealed with a valve seat, and the end of the moving iron core away from the stationary iron core is connected with a valve core. The valve seat has a first air hole at its center, and the outer wall of the housing near the valve seat has a second air hole that communicates with the first air hole. Under the elastic force of the first spring, the valve core and the valve seat abut against each other to seal, thereby disconnecting the first air hole from the second air hole.

10. The solenoid valve according to claim 1, characterized in that: The outer circumferential wall of the moving iron core is provided with an annular groove.

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