Normally closed electromagnetic valve

Abstract

The normally-closed electromagnetic valve comprises a valve body and a valve seat, the valve body comprises a valve element and an electromagnetic driving mechanism, the electromagnetic driving mechanism comprises an electromagnetic coil, a fixed iron core, an elastic piece, a magnetism isolating sleeve and a movable iron core, and a permanent magnet used for magnetizing the movable iron core is connected to the position, between the electromagnetic coil and the valve seat, of the magnetism isolating sleeve in a sleeved mode; and the elastic piece is arranged in the magnetism isolating sleeve and located between the fixed iron core and the movable iron core, one end of the elastic piece is connected with the fixed iron core, the other end of the elastic piece is connected to the outer side wall of the movable iron core in a sleeving mode, and the elastic piece is used for enabling the valve element to have the movement trend of closing the valve seat all the time. The normally-closed electromagnetic valve enables the movable iron core to move stably, and the sealing performance of valve closing is good.

Description

Technical Field

[0001] The present application relates to the technical field of automobile air suspension system control valves, and in particular to a normally closed solenoid valve. Background Art

[0002] Automotive air suspension is a device that controls the vehicle's suspension height through air pressure. The air suspension control solenoid valve is a crucial component in automotive air suspension systems. Its primary function is to control inflation or deflation, adjusting the air spring stiffness based on varying road conditions. Therefore, this solenoid valve is also known as the stiffness valve.

[0003] In related art, solenoid valves for automotive air suspension systems, particularly normally closed solenoid valves, typically have a relatively high elastic force in the elastic member between the moving iron core and the fixed iron core. This allows the valve core to remain closed when the solenoid coil is de-energized, achieving a normally closed state. When the solenoid coil is energized, a magnetic field is generated, magnetizing the moving iron core and the fixed iron core. This causes the moving iron core to overcome the elastic force of the elastic member and move toward the fixed iron core, thereby opening the valve. Due to the high elastic force of the elastic member, when the solenoid coil is de-energized, the moving iron core exerts a significant impact force on the valve body, causing significant vibration and noise. To address this issue, a permanent magnet is installed within the solenoid valve. The movement of the moving iron core cuts through the permanent magnet's magnetic field lines, creating resistance to the moving iron core's movement. This reduces the iron core's closing rate and minimizes vibration and noise. This is illustrated in the Chinese patent application entitled "Solenoid Valve" with publication number CN221347884U. In the technical solution disclosed in this patent application, the elastic member between the moving iron core and the fixed iron core has one end connected to the center hole of the fixed iron core and the other end connected to the center hole of the moving iron core, and an annular buffer is connected to the end face of the moving iron core.

[0004] The solenoid valve of the above-mentioned related technology has the following defects in actual use: the upper and lower ends of the elastic part are respectively connected to the center positions of the moving iron core and the fixed iron core. Due to the gap between the moving iron core and the solenoid valve housing and the influence of the moving iron core's own weight, when the electromagnetic coil loses power and the elastic part drives the moving iron core to move and close the valve, it will produce an axial swing, causing the moving iron core to move unsteadily, resulting in the valve not closing tightly or the valve sealing being poor. Utility Model Content

[0005] The technical problem to be solved by the present application is to overcome the defects of the above related technologies and provide a normally closed solenoid valve that can make the moving iron core move smoothly and has good sealing performance when closing the valve.

[0006] The technical solution of the present application is to provide a normally closed solenoid valve with the following structure: comprising a valve body and a valve seat, the valve body comprising a valve core and an electromagnetic drive mechanism, the electromagnetic drive mechanism comprising an electromagnetic coil, a fixed iron core, an elastic member, a magnetic isolation sleeve and a moving iron core, the fixed iron core being connected to an end of the magnetic isolation sleeve away from the valve seat and at least partially arranged in the magnetic isolation sleeve, the moving iron core slidingly fitting in the magnetic isolation sleeve and connected to the valve core; a permanent magnet for magnetizing the moving iron core is sleeved on the magnetic isolation sleeve between the electromagnetic coil and the valve seat; the elastic member is arranged in the magnetic isolation sleeve and between the fixed iron core and the moving iron core, and one end of the elastic member is connected to the fixed iron core, and the other end of the elastic member is sleeved on the outer wall of the moving iron core, so that the valve core always has a movement tendency to close the valve seat.

[0007] In some embodiments, a soft buffer pad extending axially outward is connected to an end surface of the fixed iron core close to one end of the moving iron core and / or an end surface of the moving iron core close to one end of the fixed iron core.

[0008] In some embodiments, the buffer pad is disposed in the elastic member and connected to the end surface of the fixed iron core.

[0009] In some embodiments, a concave mounting groove is provided on the end surface of the fixed iron core, the buffer pad is connected in the mounting groove and extends axially outward from the mounting groove, and the end surface of the buffer pad facing the moving iron core is set to be a plane.

[0010] In some embodiments, an outer circumferential wall of one end of the movable iron core close to the fixed iron core is provided with an annular step along the circumferential direction, and the elastic member is sleeved on the annular step.

[0011] In some embodiments, the fixed iron core includes an integrally formed insertion portion and a stop portion, the insertion portion is inserted into an end of the magnetic isolation sleeve away from the valve seat, and the stop portion is arranged outside the magnetic isolation sleeve and abuts against the end of the electromagnetic coil.

[0012] In some embodiments, the permanent magnet includes a magnetic conductive seat sleeved on the magnetic isolation sleeve and at least one magnetic steel connected to the magnetic conductive seat and extending along the circumference of the magnetic isolation sleeve.

[0013] In some embodiments, the inner wall of the magnetic base is provided with at least one accommodating groove penetrating through both end surfaces of the magnetic base along the circumferential direction, and the magnetic steel is connected to each of the accommodating grooves.

[0014] In some embodiments, the end of the magnetic isolation sleeve close to the valve seat has a baffle extending radially outward, and the baffle abuts against the end surface of the permanent magnet.

[0015] In some embodiments, the normally closed solenoid valve further includes an electrical connection seat connected to an end of the valve body away from the valve seat, and an inner end of the electrical connection seat abuts against an end surface of the fixed iron core.

[0016] To sum up, the normally closed solenoid valve of the present application has the following advantages compared with the related art: the elastic part between the fixed iron core and the moving iron core of the normally closed solenoid valve is connected to the fixed iron core at one end, and the other end is sleeved on the outer wall of the moving iron core, so that the moving iron core and the elastic part are connected as one. In the process of the electromagnetic coil losing power and driving the moving iron core to move and close the valve, the elastic part can effectively prevent the moving iron core from swinging away from the axial direction, so that the movement of the moving iron core is smooth and the concentricity is good, so that the valve is tightly closed or the valve core has good sealing performance when closing the valve; furthermore, the elastic part is connected to the outer wall of the end of the moving iron core, so that the elastic force of the elastic part can be set to be larger, thereby increasing the pre-tightening force of the valve core, and making the sealing effect better when the normally closed solenoid valve is closed. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic structural diagram of a normally closed solenoid valve in some embodiments of the present application.

[0018] Figure 2 is a cross-sectional view of a normally closed solenoid valve in some embodiments of the present application.

[0019] Figure 3 This is a schematic diagram of the assembly structure of a normally closed solenoid valve in some embodiments of the present application.

[0020] Figure 4 This is a schematic structural diagram of a permanent magnet of a normally closed solenoid valve in some embodiments of the present application.

[0021] Figure 5 This is a schematic diagram of the assembly structure of a permanent magnet of a normally closed solenoid valve in some embodiments of the present application.

[0022] Description of reference numerals:

[0023] 1. Valve body, 100. Valve housing, 101. Electromagnetic coil, 102. Magnetic isolation sleeve, 103. Fixed iron core, 104. Moving iron core, 105. Elastic member, 106. Annular step, 107. Mounting groove, 108. Buffer pad, 109. Insertion portion, 110. Stop portion, 111. Baffle, 112. Valve core, 2. Valve seat, 200. First air hole, 201. Second air hole, 202. Valve port, 203. Annular groove, 204. Sealing ring, 3. Electrical connection seat, 4. Permanent magnet, 400. Magnetic seat, 401. Accommodation groove, 402. Magnet. DETAILED DESCRIPTION

[0024] First, those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the embodiments of the present application and are not intended to limit the scope of protection of the embodiments of the present application. Those skilled in the art may adjust them as needed to suit specific application scenarios.

[0025] In the description of the embodiments of this application, it should be noted that, unless otherwise specified or limited, the terms "connected" and "connection" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium. Those skilled in the art will understand the specific meanings of the above terms in the embodiments of this application based on the specific circumstances.

[0026] In the embodiments of the present application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, a first feature being "above," "above," and "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0027] The present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] like Figures 1 to 5 As shown; The embodiment of the present application discloses a normally closed solenoid valve, which is used for an air pressure control valve of an automobile air suspension system, or is called a normally closed stiffness valve; its structure includes a valve body 1 and a valve seat 2 connected to the valve body 1, the valve body 1 includes a valve housing 100, a valve core 112 and an electromagnetic drive mechanism for driving the valve core 112 to move axially to open or close the valve seat 2; the electromagnetic drive mechanism includes an electromagnetic coil 101, a fixed iron core 103, an elastic member 105, a magnetic isolation sleeve 102 and a moving iron core 104, the fixed iron core 103 is connected to the end of the magnetic isolation sleeve 102 away from the valve seat 2 and is at least partially arranged in the magnetic isolation sleeve 102 The moving iron core 104 slides in the magnetic isolation sleeve 102 and is connected to the valve core 112; the valve seat 2 is connected to one end of the valve housing 100, and an annular groove 203 is provided on the outer wall of the valve seat 2, and a sealing ring 204 is connected in the annular groove 203 to seal with the inner wall of the valve housing 100; the valve seat 2 has a valve cavity and a first air hole 200 arranged at the end of the valve seat 2, a plurality of second air holes 201 arranged on the side wall of the valve seat 2, and a valve port 202 arranged in the valve seat 2 and connecting the first air hole 200 and the second air hole 201; the valve core 112 is clearance-fitted in the valve cavity for opening or closing the valve port 202.

[0029] In this embodiment, the valve core 112 is integrally formed at one end of the movable iron core 104 away from the fixed iron core 103 . A soft buffer seat for sealing against the valve port 202 is connected to the valve core 112 .

[0030] Further in this embodiment, Figure 2 As shown, the elastic member 105 is a coil spring, which is arranged in the magnetic isolation sleeve 102 and located between the fixed iron core 103 and the movable iron core 104, and one end of the elastic member 105 is connected to the fixed iron core 103, and the other end of the elastic member 105 is sleeved on the outer wall of the movable iron core 104, so as to ensure that the valve core 112 always has a movement tendency to close the valve seat 2.

[0031] The first air hole 200 and the second air hole 201 of the valve seat 2 of the normally closed solenoid valve in the embodiment of the present application are respectively connected to an air spring chamber of the automobile air suspension system. Under normal conditions, the elastic member 105 causes the valve core 112 on the movable iron core 104 to close the valve seat 2 and maintain the valve core 112 in a normally closed state. When the air spring pressure drops significantly and needs to be replenished, the electromagnetic drive mechanism drives the valve core 112 to open the valve seat 2 to replenish the air pressure. In this embodiment, the first air hole 200 and the second air hole 201 both have air inlet and outlet, such as the first air hole 200 for air intake and the second air hole 201 for air outlet; or the first air hole 200 for air outlet and the second air hole 201 for air intake.

[0032] It is understood that this embodiment is a normally closed solenoid valve. When the electromagnetic coil 101 loses power, that is, in the normal state of the normally closed solenoid valve, the movable iron core 104 always has a tendency to move closer to the valve seat 2 under the elastic force of the elastic member 105 and seals against the valve port 202 of the valve seat 2, that is, the solenoid valve is in the closed state. When the normally closed solenoid valve is opened, the electromagnetic coil 101 is energized to generate a magnetic field, thereby magnetizing the movable iron core 104 and the fixed iron core 103, causing the two to generate an electromagnetic force that attracts each other. When the electromagnetic force is greater than the elastic force of the elastic member 105 and the weight of the movable iron core 104, the movable iron core 104 compresses the elastic member 105, causing axial movement in the direction closer to the fixed iron core 103, thereby opening the valve port 202 of the valve seat 2.

[0033] It is not difficult to understand that in order to facilitate the installation of the moving iron core 104 and consider the influence of the deformation of the magnetic isolation sleeve 102 on the axial movement of the moving iron core 104, a certain gap is provided between the outer circumferential wall of the moving iron core 104 and the inner wall of the magnetic isolation sleeve 102; when the electromagnetic coil 101 loses power, the elastic force of the elastic member 105 causes the moving iron core 104 to move quickly toward the valve seat 2 to close the valve. The moving iron core 104 has weight and will inevitably deviate from the center line of the magnetic isolation sleeve 102 under the action of gravity, causing the moving iron core 104 to be non-concentric with the magnetic isolation sleeve 102. This will cause the valve core 112 on the moving iron core 104 to be not tightly sealed when it abuts against the valve port 202, or the moving iron core 104 will swing laterally during axial movement, resulting in poor stability. In this embodiment, one end of the elastic member is connected to the fixed iron core 103, and the other end is sleeved on the outer side wall of the moving iron core 104, so that the moving iron core 104 and the elastic member 105 are connected as a whole. When the electromagnetic coil 101 loses power and the elastic member 105 drives the moving iron core 104 to move and close the valve, the moving iron core 104 can be effectively prevented from swinging away from the axial direction, so that the movement of the moving iron core 104 is smooth and the concentricity is good, so that the valve is tightly closed or the valve core 112 has a good sealing effect when closing the valve; in addition, the elastic member 105 is connected to the outer side wall of the end of the moving iron core 104, so that the elastic force of the elastic member 105 can be set to be larger, thereby increasing the pre-tightening force of the valve core 112, so that the sealing effect is better when the normally closed solenoid valve is closed.

[0034] It is understood that after the electromagnetic coil 101 loses power, if the residual magnetism between the moving iron core 104 and the fixed iron core 103 is low, the elastic force of the elastic member 105 will cause the moving iron core 104 to quickly reset, causing the free end of the valve core 112 at the rear end of the moving iron core 104 to impact the valve port 202 of the valve seat 2, thereby generating a large impact noise. In this embodiment, a permanent magnet 4 for magnetizing the moving iron core 104 is mounted on the magnetic isolation sleeve 102 between the electromagnetic coil 101 and the valve seat 2. The permanent magnet 4 generates a magnetic field, thereby magnetizing the moving iron core 104. When the moving iron core 104 drives the valve core 112 to close the valve seat 2, the moving iron core 104 cuts the magnetic flux lines generated by the permanent magnet 4, generating resistance, thereby reducing the speed at which the valve core 112 closes the valve, thereby reducing the impact force between the sealing body at the free end face of the valve core 112 and the valve port 202, thereby reducing noise. In other words, after the electromagnetic coil 101 loses power, the magnetic field generated by the permanent magnet 4 continues to magnetize the movable iron core 104, so that a magnetic attraction still exists between the movable iron core 104 and the fixed iron core 103, thereby reducing the closing speed of the valve core 112. It is not difficult to understand that after the electromagnetic coil 101 loses power, the magnetic field of the electromagnetic coil 101 does not disappear immediately, but remains for a certain period of time, thereby maintaining a certain magnetic attraction between the movable iron core 104 and the fixed iron core 103, thereby reducing the closing speed of the valve core 112.

[0035] It can be understood that before the electromagnetic coil 101 is energized, the permanent magnet 4 pre-magnetizes the moving iron core 104, thereby reducing the time required for the electromagnetic coil 101 to magnetize the moving iron core 104, increasing the rate of the magnetic force generated by the moving iron core 104, and improving the response speed when the solenoid valve is opened.

[0036] Furthermore, in this embodiment, after the electromagnetic coil 101 is energized, under the action of the electromagnetic force, the movable iron core 104 compresses the elastic member 105 and moves toward the fixed iron core 103, causing the movable iron core 104 to collide with the fixed iron core 103, thereby generating noise. Figure 2 and Figure 3 As shown, a soft buffer pad 108 extending axially outward is connected to the end surface of the fixed core 103 close to the movable core 104. The buffer pad 108 can reduce or weaken the force of the movable core 104 hitting the fixed core 103, thereby avoiding noise.

[0037] In other embodiments, the buffer pad 108 may also be provided on the end face of the moving iron core 104 close to the fixed iron core 103; or a buffer pad 108 may be provided on the end face of the fixed iron core 103 close to the moving iron core 104 and the end face of the moving iron core 104 close to the fixed iron core 103, so as to avoid the noise generated by the moving iron core 104 hitting the fixed iron core 103, so that the normally closed solenoid valve has low noise when the valve is opened.

[0038] It is not difficult to understand that the buffer pad 108 provided on the end face of the moving iron core 104 will cause the magnetic flux area of the moving iron core 104 to decrease, that is, under a certain current or when the current remains unchanged, the reduction in the magnetic flux area of the moving iron core 104 will cause the electromagnetic force of the moving iron core 104 to decrease when opening the valve. If the area of the buffer pad 108 is increased in order to reduce the force of the moving iron core 104 hitting the fixed iron core 103, a larger current will inevitably be required, which will correspondingly increase power consumption. For this reason, the area or thickness of the annular buffer has to be reduced to avoid affecting the electromagnetic force of the moving iron core 104 when opening the valve, but this will cause the moving iron core 104 to hit the fixed iron core 103 when opening the valve and generate noise. In this embodiment, the elastic member 105 is connected to the outer wall of the end face of the moving iron core 104, and the buffer pad 108 is arranged on the end face of the fixed iron core 103 facing the moving iron core 104; under the premise that the electromagnetic force generated by the electromagnetic coil 101 can maintain the valve core 112 open, the area of the buffer pad 108 can be set larger, thereby weakening the force of the moving iron core 104 hitting the fixed iron core 103 to a greater extent, so that the normally closed solenoid valve has lower noise when the valve is opened.

[0039] In the related art, the annular cushion 108 connected to the end face of the moving iron core 104 will be compressed after contacting the end face of the fixed iron core 103, so that a vacuum is generated in the annular cushion 108, which causes the moving iron core 104 to be difficult to return to its original position when closing the valve. Figure 2 As shown, a concave mounting groove 107 is provided on the end surface of the fixed core 103. A buffer pad 108 is connected to the mounting groove 107 and extends axially outward from the mounting groove 107. The end surface of the buffer pad 108 facing the movable core 104 is designed to be flat. Before or when the movable core 104 is about to collide with the fixed core 103, the flat surface of the buffer pad 108 contacts the end surface of the movable core 104, thereby weakening the impact force. This flat surface of the buffer pad 108 effectively prevents the movable core 104 from having difficulty returning to its original position when closing the valve.

[0040] In some embodiments, as Figure 2 and Figure 3 As shown, an annular step 106 is formed along the circumferential direction on the outer circumferential wall of the end of the movable iron core 104 near the fixed iron core 103, and the elastic member 105 is sleeved on the annular step 106. This arrangement ensures a stable connection between the elastic member 105 and the movable iron core 104 and ensures concentricity between the elastic member 105 and the movable iron core 104, thereby ensuring smooth axial movement of the movable iron core 104.

[0041] In some embodiments, in order to make the internal structure of the normally closed solenoid valve more compact and smaller in size, the fixed iron core 103 includes an integrally formed inserting portion 109 and a stopper portion 110. Figure 2 and Figure 3 As shown, the insert portion 109 is plugged and sealed into the end of the magnetic isolation sleeve 102 away from the valve seat 2, and the stop portion 110 is disposed outside the magnetic isolation sleeve 102 and abuts against the end of the electromagnetic coil 101. Furthermore, in this embodiment, the normally closed solenoid valve also includes an electrical connection seat 3, which is connected to the end of the valve body away from the valve seat 2, and the inner end of the electrical connection seat 3 abuts against the end surface of the stop portion 110 of the fixed iron core 103. This makes the internal structure of the normally closed solenoid valve more compact and improves structural stability.

[0042] In some embodiments, the permanent magnet 4 includes a magnetic base 400 sleeved on the magnetic isolation sleeve 102 and at least one magnetic steel 402 connected to the magnetic base 400 and extending circumferentially along the magnetic isolation sleeve 102. Specifically, Figure 4 and Figure 5As shown, the inner wall of the magnetic base 400 is circumferentially provided with at least one receiving groove 401 extending through both ends of the magnetic base 400. Each receiving groove 401 is connected to two magnets 402 spaced apart along the circumference of the magnetic base 400. This arrangement stabilizes the magnetic field of the permanent magnet 4 and improves magnetic energy utilization, significantly reducing the velocity of the moving iron core 104 when axially moving to close the valve, thereby preventing the valve core 112 from forcefully impacting the valve port 202 of the valve seat 2.

[0043] In some embodiments, in order to make the structure of the normally closed solenoid valve more compact, simple and reduce production costs, the end of the magnetic isolation sleeve 102 close to the valve seat 2 has a baffle 111 extending radially outward, such as Figure 2 As shown, the baffle 111 abuts against the end face of the permanent magnet 4. This avoids the need for additional components on the magnetic isolation sleeve 102 to limit the axial movement of the permanent magnet 4, thereby making the normally closed solenoid valve more compact, simple, and easy to assemble.

[0044] In the description of the embodiments of the present application, it should be noted that in the description of the present application, terms such as "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying 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, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present application.

[0045] In the description of the present application, the description with reference to the terms "one embodiment", "some embodiments", "in the present embodiment", "specific example", or "some examples" means that the specific features, mechanisms, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, mechanisms, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples, unless they are contradictory.

[0046] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A normally closed solenoid valve, characterized in that: It includes a valve body and a valve seat, the valve body includes a valve core and an electromagnetic drive mechanism, the electromagnetic drive mechanism includes an electromagnetic coil, a fixed iron core, an elastic member, a magnetic isolation sleeve and a moving iron core, the fixed iron core is connected to the end of the magnetic isolation sleeve away from the valve seat and is at least partially arranged in the magnetic isolation sleeve, the moving iron core is slidably fitted in the magnetic isolation sleeve and connected to the valve core; a permanent magnet for magnetizing the moving iron core is sleeved on the magnetic isolation sleeve between the electromagnetic coil and the valve seat; the elastic member is arranged in the magnetic isolation sleeve and is located between the fixed iron core and the moving iron core, and one end of the elastic member is connected to the fixed iron core, and the other end of the elastic member is sleeved on the outer wall of the moving iron core, so that the valve core always has a movement tendency to close the valve seat.

2. The normally closed solenoid valve according to claim 1, characterized in that: A soft buffer pad extending outward in the axial direction is connected to the end surface of the fixed iron core close to one end of the moving iron core and / or the end surface of the moving iron core close to one end of the fixed iron core.

3. The normally closed solenoid valve according to claim 2, characterized in that: The buffer pad is arranged in the elastic member and connected to the end surface of the fixed iron core.

4. The normally closed solenoid valve according to claim 3, characterized in that: An inwardly concave mounting groove is provided on the end surface of the fixed iron core, the buffer pad is connected in the mounting groove and extends outwardly from the mounting groove in the axial direction, and the end surface of the buffer pad facing the movable iron core is set as a plane.

5. The normally closed solenoid valve according to claim 1, characterized in that: An outer circumferential wall of one end of the movable iron core close to the fixed iron core is provided with an annular step along the circumferential direction, and the elastic member is sleeved on the annular step.

6. The normally closed solenoid valve according to claim 1, characterized in that: The fixed iron core includes an integrally formed inserting portion and a stopping portion. The inserting portion is plugged into an end of the magnetic isolation sleeve away from the valve seat, and the stopping portion is arranged outside the magnetic isolation sleeve and abuts against the end of the electromagnetic coil.

7. The normally closed solenoid valve according to claim 1, characterized in that: The permanent magnet includes a magnetic conductive seat sleeved on the magnetic isolation sleeve and at least one magnetic steel connected to the magnetic conductive seat and extending along the circumference of the magnetic isolation sleeve.

8. The normally closed solenoid valve according to claim 7, characterized in that: The inner wall of the magnetic base is provided with at least one accommodating groove penetrating through both end surfaces of the magnetic base along the circumferential direction, and the magnetic steel is connected in each of the accommodating grooves.

9. The normally closed solenoid valve according to claim 1, characterized in that: One end of the magnetic isolation sleeve close to the valve seat is provided with a baffle extending radially outward, and the baffle abuts against the end surface of the permanent magnet.

10. The normally closed solenoid valve according to claim 1, characterized in that: The normally closed solenoid valve further includes an electrical connection seat connected to an end of the valve body away from the valve seat, and an inner end of the electrical connection seat abuts against an end surface of the fixed iron core.

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