Electric pilot piston type linear control valve

Abstract

The present invention relates to the field of automatic valve technology and discloses an electric pilot piston-type linear control valve. The electric pilot piston-type linear control valve comprises an actuator unit, a piston structure, a valve cover, and a valve body with a main valve cavity. The main valve cavity is provided with a main valve port. The actuator unit includes a valve stem capable of axial linear motion and a driving member providing thrust or tension, and the valve stem and the driving member are connected. The piston structure is slidably disposed in the main valve cavity. The piston structure is provided with a pilot valve port, which is connected to the main valve cavity. The piston structure includes a piston connecting plate and a piston that controls the opening and closing of the main valve port. The valve stem passes through the piston connecting plate to control the opening and closing of the pilot valve port. The bottom diameter of the valve stem is larger than the diameter of the pilot valve port. The piston is provided with a through hole connected to the inlet of the valve body. This provides a control valve suitable for high-pressure flow pipeline fluid working conditions.

Description

Technical Field

[0001] The invention relates to the technical field of automatic valves, in particular to an electric pilot piston type straight stroke regulating valve. Background Art

[0002] A regulating valve is a valve used to adjust process parameters such as media flow, pressure, temperature, and liquid level in industrial automation process control. It automatically adjusts the valve opening according to control signals from the automation system, thereby regulating the media flow, pressure, temperature, and liquid level. In various operating conditions where regulating valves are used to control fluid flow, there are sometimes requirements for the pressure of the fluid flowing out of the regulating valve outlet. However, in the valve structure, when a pressure differential exists between the inlet and outlet flow channels, the actuator connected to the valve stem needs to provide a considerable driving force. This, on the one hand, generates excessive unbalanced thrust on the valve stem, making it susceptible to damage; on the other hand, it places very high demands on the actuator, requiring it to generate a very high pulling force to open the valve. Therefore, there is a need for a regulating valve suitable for high-pressure flow pipeline fluid conditions. Summary of the Invention

[0003] The present invention aims to provide an electric pilot piston straight stroke regulating valve, so as to provide a regulating valve suitable for high pressure flow pipeline fluid working conditions.

[0004] To achieve the above-mentioned object, the present invention adopts the following technical solution: an electric pilot piston type straight stroke regulating valve, comprising an actuator unit, a piston structure, a valve cover portion, and a valve body provided with a main valve cavity, wherein the main valve cavity is provided with a main valve port, the actuator unit comprises a valve stem capable of axial linear motion and a driving member providing thrust or pulling force, the valve stem is connected to the driving member, the inlet and outlet of the valve body are both connected to the main valve cavity, and the valve cover portion cooperates with the valve body to cover the main valve cavity;

[0005] The piston structure is slidingly arranged in the main valve cavity. A pilot valve port is provided on the piston structure. The pilot valve port is connected to the main valve cavity. The piston structure includes a piston connecting plate and a piston for controlling the opening and closing of the main valve port. The piston connecting plate is fixed to the piston and a sliding cavity is formed between the piston connecting plate and the piston. The sliding cavity is connected to the main valve cavity. A limiting part is provided at the bottom of the valve stem. The limiting part can only slide in the sliding cavity. After the limiting part slides to the limit position, it is clamped with the piston connecting plate. The valve stem passes through the piston connecting plate to control the opening and closing of the pilot valve port. The diameter of the bottom of the valve stem is larger than the diameter of the pilot valve port. A through hole is provided on the piston to communicate with the inlet of the valve body.

[0006] The beneficial effects of this program are:

[0007] 1. The working principle of this technical solution is: in this technical solution, the valve stem is connected to the driving member, the driving member can drive the valve stem to make axial linear motion, the piston structure closes the main valve port, and the piston structure is provided with a pilot valve port. The driving member can drive the valve stem to move to control the opening and closing of the pilot valve port. When the main valve port of the regulating valve needs to be opened, the valve stem is first controlled to move to open the pilot valve port, and the pilot valve port is connected to the main valve cavity. At the same time, a through hole is provided on the piston to connect the main valve cavity with the inlet of the valve body. In a static state, high-pressure fluid enters the main valve cavity through the through hole and maintains a high-pressure state. The piston abuts against the main valve port under the action of the fluid pressure difference to ensure the closure of the main valve port. When the pilot valve port is opened, the high-pressure fluid in the main valve cavity flows out from the smaller pilot valve port. The pressure in the main valve cavity is less than the pressure in the inlet, that is, the pressure in the main valve cavity is relieved, so that the piston structure slides under the action of the fluid pressure difference to open the main valve port;

[0008] At the same time, the piston connecting plate is fixed to the piston and a sliding cavity is formed between the piston connecting plate and the piston. A limiting part is provided at the bottom of the valve stem, and the limiting part can only slide in the sliding cavity. After the limiting part moves to the extreme position, it is clamped with the piston connecting plate. When the piston structure opens the valve under the action of the fluid pressure difference, the valve stem moves upward at the same time driven by the driving member, and the valve stem can drive the piston structure to move upward, thereby further opening the main valve port. At the same time, the piston structure can open the main valve port faster under the action of the pressure difference and the drive of the valve stem.

[0009] 2. Achieve stable main valve port control under high-pressure fluid. Through the above-mentioned setting, this technical solution enables the piston structure to open the main valve port quickly under the action of pressure difference and valve stem tension. Since the regulating valve can work in a high-pressure fluid environment, when the fluid pressure is high, if the main valve port is opened by pulling the piston structure only by the driving member, a very large pulling force will be required, which will easily cause damage to the valve stem under the action of high pressure and tension. At the same time, the requirements for the driving member are also very high. Through the setting of the pilot valve port, a pressure difference is generated between the main valve cavity and the outlet channel of the valve body, and the main valve cavity is relieved of pressure at the same time, so that the main valve port can be opened with less force, which improves the opening speed of the main valve port, saves product costs, and extends the service life of the device.

[0010] Preferably, as an improvement, the actuator unit also includes a compensation mechanism and a controller, the controller is electrically connected to the driving member, the compensation mechanism includes a connecting rod and a transmission connecting rod, the valve stem is threadedly connected to the transmission connecting rod through the connecting rod, the connecting rod is threadedly connected to the driving member through the transmission connecting rod, a first groove is provided at the bottom of the driving member, the upper part of the transmission connecting rod is slidingly connected to the first groove, a disc spring is provided in the first groove, and the lower end of the disc spring is against the transmission connecting rod.

[0011] The beneficial effects are as follows: 1. By electrically connecting the controller to the driver, the controller controls the travel of the valve stem through the adjustment signal, so that the valve stem movement and the adjustment signal are linearly related. Within the effective adjustment signal and the effective piston travel range, the main valve opening can be proportionally adjusted, thereby achieving precise adjustment of the main valve opening. The change in the main valve opening can change the pressure of the fluid flowing out of the outlet, making the regulating valve suitable for working conditions that require precise control of the outlet fluid flow rate. 2. By providing a disc spring in the first groove, the valve stem can be replenished in time during use to ensure the normal operation of the valve stem.

[0012] Preferably, as an improvement, the piston structure also includes a piston guide rod and a pressure plate and a fixed ring which are sequentially sleeved on the piston guide rod, the piston guide rod passes through the piston and is clamped with the piston, the pilot valve port is located on the piston guide rod, and the lower end surface of the piston is sequentially opened with a first annular groove and a second annular groove from the center outward, the second annular groove is filled with sealing filler, the pressure plate covers the sealing filler, and the fixed ring fixedly connects the piston guide rod and the pressure plate.

[0013] The beneficial effects are: the lower end surface of the piston is opened with a first annular groove and a second annular groove from the center to the outside in sequence, the second annular groove is filled with sealing filler and is tightened with a pressure plate to ensure the sealing of the main valve chamber; the setting of the first annular groove reduces the weight of the piston, and further reduces the pulling force required when the valve stem pulls the piston; the fixing sleeve fixes the piston guide rod and the pressure plate, ensuring the structural stability and working stability of the piston structure.

[0014] Preferably, as an improvement, a third annular groove is provided on the side of the piston, a first sealing ring is provided at the bottom of the third annular groove, a second sealing ring is provided on the outer side of the first sealing ring, the first sealing ring is made of silicone, the second sealing ring is made of polytetrafluoroethylene, a second groove is provided on the lower end face of the valve stem, and the second groove is filled with sealing filler.

[0015] The beneficial effects are: the second sealing ring contacts the inner wall of the main valve cavity, the material of the first sealing ring is silicone, which is elastic. When the second sealing ring is worn after a period of use, the first sealing ring can push the second sealing ring outward to continuously ensure the sealing of the piston; the material of the second sealing ring is polytetrafluoroethylene, which has excellent corrosion resistance and sealing performance, and can avoid the erosion of the second sealing ring by the fluid. At the same time, it has good high lubricity, non-stickiness and weather resistance. The high lubricity and non-stickiness make the piston slide more smoothly in the main valve cavity, and the weather resistance extends the service life of the device; a second groove is opened on the lower end face of the valve stem, and the second groove is filled with sealing filler to ensure the sealing effect of the valve stem on the pilot valve port.

[0016] Preferably, as an improvement, the thread at the upper end of the connecting rod is a right-hand thread, and the thread at the lower end of the connecting rod is a left-hand thread.

[0017] The beneficial effect is: through the above-mentioned arrangement, when the margin of the disc spring is not enough to fill the wear of the sealing packing at the bottom of the valve stem, since the upper part of the connecting rod is a right-hand thread and the lower part is a left-hand thread, the connecting rod can be manually rotated. When the connecting rod is rotated counterclockwise, the transmission connecting rod and the valve stem move to both sides relative to the connecting rod, thereby achieving compensation for the valve stem length, tightening the sealing packing at the bottom of the valve stem, ensuring the sealing of the device, and extending the service life of the valve stem and the device.

[0018] Preferably, as an improvement, a fixed block is provided at the bottom of the valve body, a sliding hole is opened on the fixed block to accommodate the piston guide rod, and the piston guide rod is slidably connected to the fixed block through the sliding hole.

[0019] Beneficial effects: By setting a fixed block and a piston guide rod, the piston guide rod is fixedly connected to the piston, and the piston guide rod slides along the sliding hole when the piston structure slides, so as to ensure that the piston maintains stable axial movement during the movement and prevents its sliding direction from deviating. Because the regulating valve can work in high-pressure fluid, the impact of the high-pressure fluid is large when it flows, which may cause the piston structure to shift when it slides. Through the above-mentioned setting, it can ensure that the piston performs axial movement when working, and ensure the stable operation of the regulating valve.

[0020] Preferably, as an improvement, a spring is further provided in the main valve cavity, with two ends of the spring respectively pressing against the valve cover portion and the piston.

[0021] The beneficial effects are: by setting the spring, on the one hand, the pilot valve port will not be closed during the opening of the main valve port, thereby avoiding the piston shaking and abnormal noise during the adjustment of the valve flow; on the other hand, the spring can provide support force for the closing of the main valve port.

[0022] Preferably, as an improvement, the valve cover part also includes a valve seat and a valve cover, the valve seat and the valve body are fixedly connected by the valve cover, a sealing groove is opened on the upper surface of the valve seat, the sealing groove is filled with sealing filler, a pressure cover is provided to cover the sealing filler, the pressure cover is connected to the valve seat by bolts, and rotating the bolts can make the pressure cover further squeeze the sealing filler.

[0023] The beneficial effect is that, through the above arrangement, when the sealing filler in the sealing groove is worn, the sealing filler can be further compacted by rotating the bolts to tighten the gland, thereby achieving a good sealing effect.

[0024] Preferably, as an improvement, the cross-sectional flow area of ​​the through hole is smaller than the cross-sectional flow area of ​​the pilot valve port.

[0025] The beneficial effect is: the cross-sectional flow area of ​​the through hole is smaller than the cross-sectional flow area of ​​the pilot valve port, so that the fluid medium loss in the main valve chamber is greater than the inflow, and the pressure in the main valve chamber is less than the fluid pressure at the inlet, so as to ensure that a pressure difference is generated to push the piston to slide up. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the structure of an embodiment of the present invention;

[0027] Figure 2 Schematic diagram of the piston structure according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The following is further described in detail through specific implementation methods:

[0029] The figure marks in the drawings of the specification include: valve body 1, drive part 2, valve stem 3, inlet 4, outlet 5, pilot valve port 6, piston connecting plate 7, piston 8, limit part 9, through hole 10, connecting rod 11, transmission connecting rod 12, first groove 13, disc spring 14, piston guide rod 15, pressure plate 16, fixing ring 17, first annular groove 18, second annular groove 19, first sealing ring 20, second sealing ring 21, second groove 22, fixing block 23, spring 24, valve seat 25, valve cover 26, pressure cover 27, sealing groove 28, guide plate 29, guide column 30.

[0030] Example

[0031] The embodiment is basically as follows Figure 1-Figure 2 As shown, Figure 1 The electric pilot piston straight-stroke regulating valve shown includes an actuator unit, a piston structure, a valve cover and a valve body 1 provided with a main valve cavity. The main valve cavity is provided with a main valve port. The actuator unit includes a valve stem 3 that can perform axial reciprocating linear motion and a driving member 2 that provides thrust or pulling force. The valve stem 3 is connected to the driving member 2. The inlet 4 of the valve body 1 and the outlet 5 of the valve body 1 are both connected to the main valve cavity. The valve cover cooperates with the valve body 1 to cover the main valve cavity.

[0032] like Figure 1 and Figure 2 As shown, the piston structure is slidably arranged in the main valve cavity, and a pilot valve port 6 is provided on the piston structure, which is connected to the main valve cavity. The piston structure includes a piston connecting plate 7 and a piston 8 for controlling the opening and closing of the main valve port. The piston connecting plate 7 and the piston 8 are fixedly connected by bolts and a sliding cavity is formed between the piston connecting plate 7 and the piston 8, and the sliding cavity is connected to the main valve cavity. A limiting part 9 is provided at the bottom of the valve stem 3. The limiting part 9 in this embodiment is a limiting collar fixedly connected to the valve stem 3. A limiting convex ring is integrally formed on the outer side of the limiting collar. The limiting collar can only slide in the sliding cavity. After the limiting collar slides to the limit position, it is clamped with the piston connecting plate 7. The valve stem 3 passes through the piston connecting plate 7 to control the opening and closing of the pilot valve port 6. The diameter of the bottom of the valve stem 3 is larger than the diameter of the pilot valve port 6. A through hole 10 is provided on the piston 8 to communicate with the inlet 4 of the valve body 1. The cross-sectional flow area of ​​the through hole 10 is smaller than the cross-sectional flow area of ​​the pilot valve port 6.

[0033] The piston structure also includes a piston guide rod 15 and a pressure plate 16 and a fixing ring 17 which are sleeved on the piston guide rod 15 in sequence. The upper end of the piston guide rod 15 passes through the piston 8 and is clamped with the piston 8. Figure 2 As shown, the pilot valve port 6 is located at the upper part of the piston guide rod 15, and the lower end surface of the piston 8 is opened with a first annular groove 18 and a second annular groove 19 from the center to the outside. The setting of the first annular groove 18 reduces the weight of the piston 8 and reduces the pulling force required when the valve stem 3 pulls the piston 8; the second annular groove 19 is filled with sealing filler, and the pressure plate 16 covers the sealing filler to ensure the sealing of the main valve chamber. The fixing ring 17 fixes the piston guide rod 15 and the pressure plate 16 to each other, and the fixing ring 17 cooperates with the piston guide rod 15 to ensure the integrity of the piston structure.

[0034] like Figure 2 As shown, a third annular groove is provided on the side of the piston 8, a first sealing ring 20 is provided on the inner side of the third annular groove, and a second sealing ring 21 is sleeved on the outer side of the first sealing ring 20. The material of the first sealing ring 20 is silicone, which has elasticity. When the second sealing ring 21 is worn after being used for a period of time, the first sealing ring 20 can push the second sealing ring 21 outward to continuously ensure the sealing of the piston 8; the material of the second sealing ring 21 is polytetrafluoroethylene, which has good high lubricity, non-stickiness and weather resistance. The high lubricity and non-stickiness make the sliding of the piston 8 in the main valve cavity smoother; the lower end surface of the valve stem 3 is provided with a second groove 22, and the second groove 22 is filled with sealing filler, such as Figure 2 A retaining ring is provided at the bottom of the limiting collar to limit and fix the sealing packing in the valve stem 3; a fixing block 23 is provided at the bottom of the valve body 1, and a sliding hole is opened on the fixing block 23 to accommodate the piston guide rod 15. The piston guide rod 15 is slidably connected to the fixing block 23 through the sliding hole to ensure that the piston 8 maintains stable axial movement during movement and prevents its sliding direction from deviating.

[0035] The actuator unit also includes a compensation mechanism, a guide plate 29, a guide column 30 and a controller. The controller is electrically connected to the driving member 2. The controller model can be an STM32 microcontroller. The compensation mechanism includes a connecting rod 11 and a transmission connecting rod 12. Figure 1As shown, the valve stem 3 is threadedly connected to the transmission connecting rod 12 through the connecting rod 11, and the connecting rod 11 is threadedly connected to the driving member 2 through the transmission connecting rod 12. The thread at the upper end of the connecting rod 11 is a right-hand thread, and the thread at the lower end of the connecting rod 11 is a left-hand thread. The connecting rod 11 can be manually rotated. When the connecting rod 11 is rotated counterclockwise, the transmission connecting rod 12 and the valve stem 3 move to both sides relative to the connecting rod 11, thereby achieving compensation for the length of the valve stem 3; a first groove 13 is provided at the bottom of the driving member 2, and the upper part of the transmission connecting rod 12 is slidably connected to the first groove 13. A disc spring 14 is provided in the first groove 13, and the lower end of the disc spring 14 is against the transmission connecting rod 12. By arranging the disc spring 14 in the first groove 13, the wear of the valve stem 3 can be replenished in time during use to ensure the normal operation of the valve stem 3; a guide plate 29 is sleeved on the outside of the driving member 2, and the guide plate 29 is slidably connected to the guide column 30 to ensure that the sliding direction of the driving member 2 is vertical.

[0036] The valve cover portion includes a valve seat 25 and a valve cover 26. The valve seat 25 and the valve body 1 are fixedly connected through the valve cover 26. The valve cover 26 is fixedly connected to the valve seat 25 by bolts. The provision of the valve seat 25 is conducive to extending the effective movement stroke of the valve stem 3, so that it can adapt to various working conditions. The lower end of the guide column 30 is fixed to the valve seat 25 by bolts. A sealing groove 28 is opened on the upper surface of the valve seat 25. The sealing groove 28 is filled with sealing packing. A pressure cover 27 is provided to cover the sealing packing. The pressure cover 27 is connected to the valve seat 25 by bolts. Rotating the bolts can make the pressure cover 27 further squeeze the sealing packing. A spring 24 is also provided in the main valve chamber. The two sides of the spring 24 respectively press against the valve cover 26 and the piston 8. On the one hand, the spring 24 can prevent the pilot valve port 6 from closing during the opening of the main valve port, thereby avoiding the vibration and abnormal noise of the piston 8 during the process of adjusting the valve flow.

[0037] The specific implementation process is as follows:

[0038] In this technical solution, the valve stem 3 is connected to the driving member 2, and the driving member 2 can drive the valve stem 3 to make axial linear motion. The piston structure closes the main valve port. The piston structure is provided with a pilot valve port 6. The driving member 2 can drive the valve stem 3 to move and control the opening and closing of the pilot valve port 6. When the main valve port of the regulating valve needs to be opened, the valve stem 3 is first controlled to move to open the pilot valve port 6. The pilot valve port 6 is connected to the main valve cavity. At the same time, a through hole 10 is provided on the piston 8 to connect the main valve cavity with the inlet 4 of the valve body 1. In a static state, the high-pressure fluid enters the main valve cavity through the through hole 10. And maintain a high-pressure state, the cross-sectional flow area of ​​the through hole 10 is smaller than the cross-sectional flow area of ​​the pilot valve port 6, so that the fluid medium loss in the main valve chamber is greater than the inflow, so that the pressure of the main valve chamber is less than the fluid pressure of the inlet 4, and the piston 8 abuts the main valve port under the action of the fluid pressure difference to ensure the closure of the main valve port. When the pilot valve port 6 is opened, the high-pressure fluid in the main valve chamber flows out from the smaller pilot valve port 6, and the pressure of the main valve chamber is less than the pressure of the inlet 4, that is, the pressure of the main valve chamber is unloaded, so that the piston structure slides under the action of the fluid pressure difference to open the main valve port.

[0039] Through the above-mentioned arrangement, the piston structure of this embodiment can open the main valve port more quickly under the action of pressure difference and the pulling force of the valve stem 3. Since the regulating valve can work in a high-pressure fluid environment, when the fluid pressure is high, if the main valve port is opened by pulling the piston structure only by the driving member 2, a very large pulling force will be required, and the requirements for the driving member 2 will also be very high. Under the action of high pressure and pulling force, the valve stem 3 is easily damaged. Through the setting of the pilot valve port 6, a pressure difference is generated between the main valve cavity and the outlet 5 of the valve body 1, and the main valve cavity is relieved of pressure at the same time, so that the main valve port can be opened with less force, thereby improving the opening speed of the main valve port, saving product costs, and extending the service life of the device.

[0040] The piston connecting plate 7 is fixed to the piston 8 and a sliding cavity is formed between the piston connecting plate 7 and the piston 8. A limit clamping ring is provided at the bottom of the valve stem 3. After the limit clamping ring moves to the limit position, it is clamped with the piston connecting plate 7. When the piston structure opens the valve under the action of the fluid pressure difference, the valve stem 3 moves upward at the same time under the drive of the driving member 2. The valve stem 3 can drive the piston structure to move upward, thereby further opening the main valve port. At the same time, the piston structure can be opened faster under the action of the pressure difference and the drive of the valve stem 3. When the main valve port needs to be closed, the driving member 2 pushes the valve stem 3 to close the pilot valve port 6. Because the bottom diameter of the valve stem 3 is larger than the diameter of the pilot valve port 6, the valve stem 3 continues to move, which can push the piston structure to move downward and thus realize the closure of the main valve port.

[0041] The controller is electrically connected to the drive member 2. The controller controls the movement stroke of the valve stem 3 by adjusting the signal, so that the movement of the valve stem 3 is linearly related to the adjustment signal. Within the effective adjustment signal and the effective movement stroke of the piston 8, the proportional adjustment of the main valve port opening is achieved, thereby achieving precise adjustment of the main valve port opening. The change in the opening of the main valve port can change the pressure of the fluid flowing out of the outlet 5, so that the regulating valve can adapt to the working conditions that require precise control of the flow rate of the fluid at the outlet 5.

[0042] The above is only an embodiment of the present invention, and the common knowledge such as the specific technical solutions and / or characteristics in the solution are not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the description can be used to interpret the content of the claims.

Claims

1. An electric pilot piston linear control valve comprises an actuator unit, a piston structure, a valve cover, and a valve body with a main valve cavity. The main valve cavity is provided with a main valve port. The actuator unit comprises a valve stem capable of axial linear motion and a drive member providing thrust or pull. The valve stem is connected to the drive member. The inlet and outlet of the valve body are both connected to the main valve cavity. The valve cover cooperates with the valve body to cover the main valve cavity. The valve body is characterized by: The piston structure is slidingly arranged in the main valve cavity, and a pilot valve port is provided on the piston structure, and the pilot valve port is communicated with the main valve cavity. The piston structure includes a piston connecting plate and a piston that controls the opening and closing of the main valve port. The piston connecting plate is fixed to the piston and a sliding cavity is formed between the piston connecting plate and the piston, and the sliding cavity is communicated with the main valve cavity. A limiting part is provided at the bottom of the valve stem, and the limiting part can only slide in the sliding cavity. After the limiting part slides to the limit position, it is clamped with the piston connecting plate. The valve stem passes through the piston connecting plate to control the opening and closing of the pilot valve port. The diameter of the bottom of the valve stem is larger than the diameter of the pilot valve port. A through hole is provided on the piston to communicate with the inlet of the valve body. The actuator unit also includes a compensation mechanism and a controller. The controller is electrically connected to the drive component. The compensation mechanism includes a connecting rod and a transmission connecting rod. The valve stem is connected to the main valve cavity through the connecting rod. The cam is threadedly connected to the transmission connecting rod, and the connecting rod is threadedly connected to the driving member through the transmission connecting rod. A first groove is provided at the bottom of the driving member, and the upper part of the transmission connecting rod is slidably connected to the first groove. A disc spring is provided in the first groove, and the lower end of the disc spring is against the transmission connecting rod. The piston structure also includes a piston guide rod and a pressure plate and a fixed collar which are sequentially sleeved on the piston guide rod. The piston guide rod passes through the piston and is clamped with the piston. The pilot valve port is located on the piston guide rod. The lower end surface of the piston is sequentially provided with a first annular groove and a second annular groove from the center outward. The second annular groove is filled with sealing filler. The pressure plate is covered on the sealing filler. The fixed collar fixes the piston guide rod and the pressure plate. A spring is also provided in the main valve chamber, and the two ends of the spring respectively press against the valve cover and the piston.

2. The electric pilot piston type linear control valve according to claim 1, characterized in that: A third annular groove is provided on the side of the piston, a first sealing ring is provided at the bottom of the third annular groove, a second sealing ring is provided on the outer side of the first sealing ring, the first sealing ring is made of silicone, the second sealing ring is made of polytetrafluoroethylene, a second groove is provided on the lower end surface of the valve stem, and the second groove is filled with sealing filler.

3. The electric pilot piston type linear control valve according to claim 2, characterized in that: A fixed block is provided at the bottom of the valve body. A sliding hole capable of accommodating a piston guide rod is opened on the fixed block. The piston guide rod is slidably connected to the fixed block through the sliding hole.

4. The electric pilot piston type linear control valve according to claim 3, characterized in that: The valve cover part also includes a valve seat and a valve cover. The valve seat and the valve body are fixedly connected through the valve cover. A sealing groove is opened on the upper surface of the valve seat. The sealing groove is filled with sealing filler. A pressure cover is provided to cover the sealing filler. The pressure cover is connected to the valve seat by bolts. Turning the bolts can make the pressure cover further squeeze the sealing filler.

5. The electric pilot piston type linear control valve according to claim 4, characterized in that: The cross-sectional flow area of ​​the through hole is smaller than the cross-sectional flow area of ​​the pilot valve port.

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