Pilot proportional valve

Abstract

The pilot proportional valve comprises a main valve body and a main valve element, a main valve cavity is formed in the main valve body, and the main valve cavity extends in the direction of the central axis of the main valve cavity; the bottom end face of the main valve body is used for being in butt joint with an external device. The main valve core is movably arranged in the main valve cavity; installation parts protruding outwards are arranged on the two opposite sides of the main valve body. At least one mounting hole penetrating through the thickness direction of the mounting part is formed in the mounting part; the mounting holes comprise a first through hole and a second through hole which are communicated with each other and are positioned at the top and the bottom; the inner diameter of the first through hole is larger than that of the second through hole, and a step face used for bearing a screw is formed at the connecting position of the first through hole and the second through hole. Wherein the step surface is lower than the central axis in the height direction. Due to the fact that the step face is lower than the central axis of the main valve cavity, assembly stress mainly acts on the lower area of the main valve body, the problem that the main valve element is stuck due to deformation of the main valve body is solved, and the main valve element is particularly suitable for long-term stable operation of the high-precision pilot proportional valve.

Description

Technical Field

[0001] The present disclosure relates to the field of hydraulic valves, and in particular to a pilot proportional valve. Background Art

[0002] A pilot proportional valve is a hydraulic component that precisely controls fluid direction, pressure, or flow through electrical signals. It consists of a pilot valve and a main valve. The pilot valve receives the electrical signal and adjusts the control pressure, which in turn drives the main valve core, achieving high-precision and fast-response flow regulation. Widely used in engineering machinery, automation equipment, and other fields, it offers flexible control, energy efficiency, and high efficiency.

[0003] Existing pilot proportional valves require screws to secure the main valve during assembly. However, this assembly method results in uneven stress distribution within the main valve body. Over extended use, the high-pressure impact of the hydraulic oil further impacts the stress distribution within the main valve body, causing it to gradually deform. This deformation alters the clearance between the main valve core and the main valve cavity, ultimately hindering or even blocking the main valve core, impacting the oil circuit switching performance and service life of the pilot proportional valve. Summary of the Invention

[0004] In order to solve the problems existing in the prior art, the present disclosure provides a pilot proportional valve.

[0005] According to a first aspect of the present disclosure, there is provided a pilot proportional valve, comprising: A main valve body, wherein a main valve cavity is provided in the main valve body, and the main valve cavity is configured to extend along the direction of the central axis thereof; the bottom end surface of the main valve body is configured to be connected to an external device; a main valve core, the main valve core being configured to be movably disposed in the main valve chamber; The opposite sides of the main valve body are constructed to be provided with outwardly protruding mounting portions; at least one mounting hole is provided on the mounting portion that passes through its thickness direction; the mounting holes include a first through hole that is interconnected and located at the top, and a second through hole that is located at the bottom; the inner diameter of the first through hole is larger than the inner diameter of the second through hole, and a step surface for supporting screws is formed at the position where the two are connected; wherein the step surface is constructed to be lower than the center axis in the height direction.

[0006] In one embodiment of the present disclosure, the end surface of the mounting portion is higher than the height of the central axis, and the step surface is a plane.

[0007] In one embodiment of the present disclosure, inner diameters of the mounting holes located at the four corners of the main valve body are respectively larger than the inner diameter of the mounting hole near the center of the mounting portion.

[0008] In one embodiment of the present disclosure, a height ratio of the first through hole to the second through hole ranges from 0.25 to 0.67.

[0009] In one embodiment of the present disclosure, the bottom of the main valve body is configured to be finely milled, and the bottom end surface of the main valve body is configured to have a deformation space that is gradually recessed upward from the outside to the inside.

[0010] In one embodiment of the present disclosure, a limiting screw is provided at the bottom of the main valve body, and a limiting groove is provided on the main valve core, and the limiting groove is constructed to extend in the direction of the central axis; wherein, the limiting screw is constructed to extend to cooperate with the limiting groove.

[0011] In one embodiment of the present disclosure, the axis on which the limit screw is located is perpendicular to the central axis.

[0012] In one embodiment of the present disclosure, the angle between the axis of the limit screw and the central axis is in the range of 95° to 105°.

[0013] In one embodiment of the present disclosure, at least one shoulder is provided on the main valve core, and at least one throttling groove is provided on the circumferential surface of the shoulder at a position adjacent to the edge thereof.

[0014] In one embodiment of the present disclosure, the throttling groove is trapezoidal.

[0015] One beneficial effect of the present disclosure is that during the assembly process of the main valve body of the pilot proportional valve provided by the present disclosure, when the screws are tightened, the step surface is lower than the central axis of the main valve cavity, so that the assembly stress mainly acts on the lower area of ​​the main valve body, avoiding the stress from being directly transmitted to the wall of the main valve cavity, thereby significantly reducing the radial deformation of the main valve cavity during subsequent use, avoiding the problem of the main valve core being stuck due to deformation of the main valve body, and is particularly suitable for the long-term stable operation of high-precision pilot proportional valves.

[0016] Other features and advantages of the present disclosure will become apparent from the following detailed description of exemplary embodiments of the present disclosure with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0018] Figure 1 is a cross-sectional schematic diagram of a pilot proportional valve provided by an embodiment of the present disclosure; Figure 2 1 is a schematic cross-sectional view of a main valve of a pilot proportional valve provided in an embodiment of the present disclosure; Figure 3This is a schematic diagram of the main valve core of the pilot proportional valve provided in an embodiment of the present disclosure; Figure 4 Schematic diagram of the bottom surface of the main valve body of the pilot proportional valve provided in an embodiment of the present disclosure.

[0019] Figures 1 to 4 The one-to-one correspondence between the component names and the reference numerals is as follows: 10. Main valve part; 11. Main valve body; 110. Mounting hole; 111. Mounting part; 112. First through hole; 113. Second through hole; 114. Step surface; 12. Main valve chamber; 13. Main valve core; 131. Shoulder; 132. Throttle groove; 133. Limit groove; 14. Limit screw; 15. Return spring; 16. Position sensor; 17. Working oil port; 18. Recessed part; 20. Pilot valve part. DETAILED DESCRIPTION

[0020] Various exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present disclosure.

[0021] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the present disclosure, its application, or uses.

[0022] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0023] It should be noted that like reference numerals and letters refer to like items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0024] In this document, “upper”, “lower”, “front”, “back”, “left”, “right”, etc. are only used to indicate the relative position relationship between related parts, rather than to limit the absolute positions of these related parts.

[0025] In this article, "first", "second", etc. are only used to distinguish each other, and do not indicate the importance and order, or the prerequisite for each other's existence.

[0026] In this document, “equal”, “same”, etc. are not strictly limited in a mathematical and / or geometric sense, but also include errors that can be understood by those skilled in the art and are allowed in manufacturing or use.

[0027] The pilot proportional valve provided in the present disclosure is used in the speed control system of a nuclear power steam turbine to accurately adjust the steam flow, thereby controlling the power, speed or pressure of the unit, and proportionally adjusting the valve opening according to the control signal to achieve linear or nonlinear control of the steam flow.

[0028] The pilot proportional valve uses the principle of electrical feedback control to automatically, quickly, and accurately feed the output signal of the controlled object, i.e., the output quantity, such as displacement, velocity, or force, back to the system input. This signal is then compared with a given value to form a deviation signal, thereby controlling the controlled object and keeping the difference between the system's output and the given value within an acceptable range. At the same time, the output power is significantly amplified, converting tiny electrical signals into high-power hydraulic energy (flow and pressure) output, enabling it to drive various loads and perform automated intelligent control applications such as position control, velocity control, acceleration control, or force control.

[0029] The pilot proportional valve includes a pilot valve portion and a main valve portion. The pilot valve portion includes a pilot valve body, a pilot valve core, a pilot valve sleeve, a tempering demodulator and a high-frequency electromagnet. The pilot proportional valve adopts a servo valve-type pilot valve core valve sleeve structure, with μ-level processing accuracy and a hysteresis ring close to that of a servo valve. The pilot valve sleeve and the pilot valve body have an interference fit, the pilot valve port has zero coverage, there is no zero-position dead zone, and the frequency response is close to that of a servo valve. In order to meet the high-frequency dynamic performance of the pilot valve core and the pilot valve sleeve, there are two types of materials that can be selected for the pilot valve core and the pilot valve sleeve: one is high-strength carburized steel, such as: 12CrNi3A, 18CrNiWA, etc., and the other is high-hardness alloy tool steel, such as: Cr12MoV, 9Cr18Mo, etc. Preferably, the pilot proportional valve provided in the present disclosure uses Cr12MoV material.

[0030] The pilot valve body is constructed of cast steel, with a cobalt-based alloy overlay weld finish on the high-temperature section. The pilot valve spool features a multi-stage pressure reduction design to reduce steam velocity and minimize erosion. The control axis card integrates a PID control module and supports bus communication (such as Profibus DP). The control axis card receives the pilot valve spool position command signal, compares it with the pilot valve spool's actual position signal, performs closed-loop calculations based on the deviation, and converts the result into a command signal for the pilot valve controller, which drives the pilot valve spool and regulates the flow rate entering the pilot valve spool's control chamber, moving the pilot valve spool in a direction that minimizes position deviation until the pilot valve spool position deviation is zero and the pilot valve spool returns to its neutral position. When power is removed, the pilot valve spool returns to its safe position under the action of a spring. Oil is then returned to the left and right control chambers of the pilot valve spool, and the spring forces the pilot valve spool back to its neutral position.

[0031] The main valve portion of the pilot proportional valve provided in the present disclosure includes a main valve body provided with a main valve cavity, and a main valve core movably connected in the main valve cavity, wherein the main valve cavity is constructed to extend in the direction of its central axis, and the extension direction of the main valve core is consistent with it, so that the main valve core can reciprocate along the extension direction of the main valve cavity to realize the opening, closing or reversing of the control oil circuit of the pilot proportional valve.

[0032] The bottom of the main valve body is configured to interface with an external device to securely mount the pilot proportional valve. Mounting portions are located on opposite sides of the main valve body. These portions protrude outward from opposite sides of the main valve body and have at least one mounting hole extending through the thickness of the main valve body. The main valve body can be secured to the external device by screws passing through these mounting holes.

[0033] The mounting hole includes a first through hole located at the top and interconnected, and a second through hole located at the bottom. The inner diameter of the first through hole is larger than the inner diameter of the second through hole, and the position where the two are connected forms a step surface for supporting the screw; when the screw passes through the first through hole and the second through hole, the end flange of the screw is supported on the step surface, thereby fixing the main valve body on the external device, thereby realizing the installation of the proportional valve.

[0034] The stepped surface is constructed to be lower in height than the central axis. This ensures that during assembly of the main valve body provided by the present disclosure, when the screws are tightened, the assembly stress is primarily applied to the lower area of ​​the main valve body, avoiding direct transmission to the main valve cavity wall. This significantly reduces radial deformation of the main valve cavity. This structural design fundamentally avoids the problem of main valve core seizure caused by main valve body deformation and is particularly suitable for the long-term stable operation of high-precision proportional valves.

[0035] The specific embodiments of the present disclosure are described below with reference to the accompanying drawings.

[0036] like Figures 1 to 2 As shown, the present disclosure provides a pilot proportional valve, including a main valve portion 10 and a pilot valve portion 20. The main valve portion 10 includes a main valve body 11 provided with a main valve chamber 12, and a main valve core 13 movably connected within the main valve chamber 12. A working oil port 17 is connected to the main valve chamber 12. The main valve chamber 12 is configured to extend in the direction of its central axis, and the main valve core 13 extends in the same direction as the main valve chamber 12, so that the main valve core 13 can reciprocate along the extension direction of the main valve chamber 12 to open and close the pilot proportional valve or control the switching of the oil circuit.

[0037] The bottom of the main valve body 11 is configured to interface with an external device to securely mount the pilot proportional valve. Mounting portions 111 are provided on opposite sides of the main valve body 11. These mounting portions 111 protrude outward from opposite sides of the main valve body 11. Each mounting portion 111 is provided with at least one mounting hole 110 extending through its thickness. The main valve body 11 can be secured to an external device by inserting a screw through each mounting hole 110.

[0038] The mounting hole 110 includes a first through hole 112 which is interconnected and located at the top of the mounting portion 111, and a second through hole 113 which is located at the bottom. The inner diameter of the first through hole 112 is larger than the inner diameter of the second through hole 113, and the position where the two are connected forms a step surface 114 for supporting the screw; when the screw passes through the first through hole 112 and the second through hole 113, the end flange of the screw is supported on the step surface 114, thereby fixing the main valve body 11 on the external device, thereby realizing the installation of the pilot proportional valve.

[0039] Specifically, if Figure 2 and Figure 4 As shown, the inner diameters of the mounting holes 110 at the four corners of the main valve body 11 are larger than the inner diameters of the mounting holes 110 near the center of the mounting portion 111. The larger-diameter mounting holes 110 at the four corners of the main valve body 11 can accommodate larger-diameter fastening screws or locating pins, strengthening the connection between the edge of the main valve body 11 and external devices, better resisting vibration or impact from the external environment, and preventing deformation or loosening of the main valve body 11. The smaller-diameter mounting holes 110 near the center of the main valve body 11 are suitable for standard screws, ensuring a compact overall structure and assembly flexibility. Furthermore, the top end surface of the mounting portion 111 is elevated above the central axis of the main valve chamber 12. The connection between the first through-hole 112 and the second through-hole 113 forms a flat step surface 114 for supporting the screws. The elevated end surface of the mounting portion 111, combined with the flat, rather than tapered, step surface 114, ensures a smooth contact surface between the screws and the main valve body 11 during installation, improving assembly precision and reducing the risk of loosening of the valve blocks in the main valve body 11 during use. In addition, the height ratio of the first through hole 112 to the second through hole 113 ranges from 0.25 to 0.67. Specifically, the height ratio of the first through hole 112 to the second through hole 113 provided in the present disclosure is 0.43.

[0040] The bottom of the main valve body 11 of the pilot proportional valve provided by the present invention is constructed to be processed by precision milling, and the bottom end surface of the main valve body 11 is constructed to have a deformation space that gradually concave upward from the outside to the inside. Specifically, the concave portion 18 is located at Figure 4The middle arrow points to the center of the bottom of the main valve body 11. The main valve body 11 is made of QT400, a material with high compressive strength. During the bottom surface machining of the main valve body 11, the final step involves precision milling of the bottom end face of the main valve body 11, with the tool feed only from one direction. This creates a concave shape on the bottom of the main valve body 11 after precision milling. When the main valve body 11 is installed and the screws are tightened, the deformation of the main valve body 11 precisely fills the recessed space of the pre-machined recess 18, effectively offsetting the compression of the main valve cavity 12 by the installation stress, thereby preventing the main valve core 13 from being stuck due to compression and deformation of the main valve cavity 12.

[0041] like Figure 1 and Figure 3 As shown, a limiting screw 14 is provided at the bottom of the main valve body 11 of the pilot proportional valve provided by the present invention, and a limiting groove 133 is provided on the main valve core 13. The limiting groove 133 is constructed to extend in the direction of the central axis; wherein, the limiting screw 14 is constructed to extend to cooperate with the limiting groove 133. When the main valve core 13 reciprocates in the main valve chamber 12, the head of the limiting screw 14 slides in the limiting groove 133, so that the main valve core 13 can move freely in the axial direction; at the same time, the side wall of the limiting groove 133 contacts the limiting screw 14, forming a mechanical stop, limiting the freedom of the main valve core 13 to rotate around the central axis. The matching structure of the limiting screw 14 and the limiting groove 133 can effectively prevent the main valve core 13 from rotating at high speed during operation, and can eliminate the problem of reduced control accuracy of its position due to rotational vibration, thereby reducing the risk of oil circuit blockage caused by this.

[0042] The main valve core 13 of the pilot proportional valve provided herein is made of Y40Mn and undergoes high-frequency quenching, achieving a hardness of HRA 76.3-78.5 and a hardened layer depth of 0.6-0.8. This improves the wear resistance of the main valve core 13 while maintaining its inherent toughness. To reduce leakage and prevent the main valve core 13 from getting stuck, the outer diameter of the main valve core 13 is ground to the main bore of the main valve body 11, achieving a cylindricity of 2μm and a clearance of 10-16μm.

[0043] like Figure 1As shown, the axis of the limit screw 14 is perpendicular to the central axis or forms an angle of 95° to 105°. When the axis of the limit screw 14 is perpendicular to the central axis, the contact surface of the limit screw 14 and the limit groove 133 forms a right-angle limit. This right-angle limit reduces the tiny displacement of the main valve core 13 caused by vibration when the main valve core 13 reciprocates, making the stroke control of the main valve core 13 more accurate. When the axis of the limit screw 14 is at an angle of 75° to 85° to the central axis, the axial displacement of the main valve core 13 will be converted into an extrusion effect on the oblique contact surface, so that the vibration energy of the main valve core 13 is not only rigidly blocked, but also dissipated due to the existence of oblique friction. The inclined design reduces the noise caused by the reciprocating motion of the main valve core 13, and reduces the impact between metal parts, avoiding the situation where the limit screw 14 becomes loose or the contact surface is worn and cracked due to long-term vibration of the main valve core 13. In addition, the inclined design introduces inclined surface contact. When the inclination angle between the limit screw 14 and the limit groove 133 is smaller than the friction angle between the materials, a self-locking effect can be formed to prevent the main valve core 13 from accidentally rotating or loosening under vibration or external force.

[0044] like Figure 3 As shown, the main valve core 13 of the pilot proportional valve provided by the present disclosure is provided with two cylindrical shoulders 131, and the shoulders 131 include a circumferential surface with an arc and end surfaces on both sides, which are used to control the on / off or flow direction of the fluid. Specifically, the valve core rod of the main valve core 13 in the present disclosure is provided with two shoulders 131 at intervals, and the position where the circumferential surface of the shoulder 131 and the end surface of the shoulder 131 intersect is defined as the edge of the shoulder 131. Two throttling grooves 132 are provided on the circumferential surface of each shoulder 131 adjacent to its edge. Specifically, the shape of the throttling groove 132 on the main valve core 13 provided by the present disclosure is trapezoidal. As shown Figure 3 As shown by the dotted line pointed by the middle arrow A, the width of the throttling groove 132 is defined as the distance between the two farthest points in the intersection formed by the throttling groove 132 and the parallel surface of the shoulder 131 end face, and the ratio of the maximum width of the throttling groove 132 to the end face diameter of the shoulder 131 is in the range of 0.5 to 0.7. Specifically, the ratio of the maximum width of the throttling groove 132 provided in the present invention to the end face diameter of the shoulder 131 is 0.6, and the width of the throttling groove 132 gradually decreases from the edge of the shoulder 131 to the center of the shoulder 131.

[0045] The throttle groove 132 of the traditional pilot proportional valve main valve core 13 is in the form of a triangular groove, and the processing method adopts electrospark machining, which has low efficiency. In addition, due to the characteristics of electrospark machining, the end face of the triangular groove is uneven, and the black residue remaining on it is difficult to remove, which has a great impact on the cleanliness and performance of the finished product.

[0046] The throttle groove 132 of the main valve core 13 of the pilot proportional valve can be designed in a triangular, trapezoidal or U-shaped and triangular combination according to the difference in diameter and function.

[0047] When the main valve core 13 moves, the throttle groove 132 gradually adjusts the flow area of ​​the oil to avoid sudden pressure changes caused by sudden opening or closing of the oil circuit, thereby significantly reducing the impact of the hydraulic oil on the main valve body 11 and reducing the mechanical wear of the main valve body 11 and the main valve core 13, thereby extending the service life of the main valve body 11 and the main valve core 13.

[0048] The throttling groove 132 structure, which combines a triangular, trapezoidal, or U-shaped structure with a triangular shape, achieves more optimized flow regulation characteristics compared to traditional V-groove designs. This composite groove structure, by changing the gradual change pattern of the flow channel cross-sectional shape, produces a smoother pressure drop gradient when the fluid passes through the throttling area. This effectively reduces the occurrence of turbulence (turbulence refers to the flow instability caused by sudden changes in flow velocity and boundary layer separation when the fluid passes through the throttling groove 132 at high speed, manifesting as irregular vortex motion and strong pressure pulsation. This disordered flow not only increases energy loss but also causes high-frequency vibration of the valve core, reducing control accuracy) and cavitation (cavitation occurs when the local pressure drops suddenly below the saturated vapor pressure, causing dissolved gas in the fluid to rapidly precipitate and form tiny bubbles. These bubbles instantly collapse when the fluid moves to the high-pressure area, generating shock waves of up to thousands of atmospheres of pressure. This periodic micro-jet impact continuously erodes the valve core surface material, forming honeycomb-like cavitation damage).

[0049] The main valve portion 10 of the pilot proportional valve provided in the present disclosure is further provided with a return spring 15. Figure 1 As shown, the return spring 15 and the spring seat are installed between the main valve body 11 and the end cover without any gap, and the return spring 15 has a certain pre-compression amount.

[0050] The pilot proportional valve provided by the present disclosure utilizes a return spring 15 to balance the hydraulic pressure in both the left and right directions of movement of the main valve core 13. This ensures that the main valve core 13 moves equally in both directions under the same input signal. Furthermore, the suspension of the spring seat helps reduce hysteresis.

[0051] The single-spring design of the return spring 15 balances the main valve core 13 through the interaction of spring force and hydraulic pressure. When the main valve core 13 moves, the hydraulic pressure on one side increases, compressing or stretching the return spring 15, generating a counterforce. By adjusting the hydraulic pressure, the spring force and the hydraulic pressure are dynamically balanced, thereby precisely controlling the valve core position and achieving proportional flow regulation. This design simplifies the structure, requiring only a single spring to achieve force balance in both directions of movement.

[0052] The position sensor 16 used in the pilot proportional valve provided by the present invention is an inductive displacement sensor. The inductive displacement sensor uses electromagnetic induction to convert the displacement of the measured main valve core 13 into changes in the self-inductance coefficient and mutual inductance coefficient of the coil, and then converts it into a voltage or current change output by the circuit, thereby realizing the conversion of non-electrical quantity to electrical quantity.

[0053] The embodiments of the present disclosure have been described above. The above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terms used herein are selected to best explain the principles of the embodiments, their practical applications, or technical improvements in the marketplace, or to enable other persons skilled in the art to understand the embodiments disclosed herein. The scope of the present disclosure is defined by the appended claims.

Claims

1. A pilot proportional valve, characterized in that: include: A main valve body, wherein a main valve cavity is provided in the main valve body, and the main valve cavity is configured to extend along the direction of the central axis thereof; The bottom end surface of the main valve body is configured to interface with an external device; a main valve core, the main valve core being configured to be movably disposed in the main valve chamber; The opposite sides of the main valve body are constructed to be provided with outwardly protruding mounting portions; at least one mounting hole is provided on the mounting portion that passes through its thickness direction; the mounting holes include a first through hole that is interconnected and located at the top, and a second through hole that is located at the bottom; the inner diameter of the first through hole is larger than the inner diameter of the second through hole, and a step surface for supporting screws is formed at the position where the two are connected; wherein the step surface is constructed to be lower than the center axis in the height direction.

2. The pilot proportional valve according to claim 1, characterized in that: The top end surface of the mounting portion is higher than the height of the central axis, and the step surface is a plane.

3. The pilot proportional valve according to claim 1, characterized in that: The inner diameters of the mounting holes located at the four corners of the main valve body are respectively larger than the inner diameter of the mounting hole close to the center of the mounting portion.

4. The pilot proportional valve according to claim 1, characterized in that: The height ratio of the first through hole to the second through hole is in a range of 0.25 to 0.

67.

5. The pilot proportional valve according to claim 1, characterized in that: The bottom of the main valve body is configured to be processed by precision milling, and the bottom end surface of the main valve body is configured to have a deformation space that is gradually recessed upward from the outside to the inside.

6. The pilot proportional valve according to claim 1, characterized in that: A limiting screw is provided at the bottom of the main valve body, and a limiting groove is provided on the main valve core. The limiting groove is constructed to extend in the direction of the central axis; wherein the limiting screw is constructed to extend to cooperate with the limiting groove.

7. The pilot proportional valve according to claim 6, characterized in that: The axis where the limit screw is located is perpendicular to the central axis.

8. The pilot proportional valve according to claim 6, characterized in that: The included angle between the axis of the limit screw and the central axis is in the range of 95° to 105°.

9. The pilot proportional valve according to claim 1, characterized in that: At least one shoulder is provided on the main valve core, and at least one throttling groove is provided on the circumferential surface of the shoulder at a position adjacent to the edge thereof.

10. The pilot proportional valve according to claim 9, characterized in that: The throttling groove is trapezoidal.

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