Low-torque butterfly valve, valve seat and valve plate design method

Abstract

The invention provides a low-torque butterfly valve, a valve seat and a valve plate design method, the low-torque butterfly valve comprises a valve body, the valve seat, the valve plate and a valve rod, and the width of the valve seat is gradually increased in the circumferential extension direction of a medium channel from the rotary connection position of the valve rod and the valve body. According to the butterfly valve, the valve seat with the width gradually increased in the circumferential extending direction of the medium channel from the rotary connecting position of the valve rod and the valve body is arranged on the side wall of the medium channel, so that in the opening and closing process of the butterfly valve, when the valve plate is closed to a set angle, the valve plate makes extrusion contact with the valve seat. Compared with a conventional rubber-lined butterfly valve, a valve seat sealing face evenly protrudes, the problem that large friction exists between the valve plate and the valve seat all the time in the opening and closing process of the valve plate is solved, and therefore the torque and friction abrasion of the center line rubber-lined butterfly valve in the opening and closing process are effectively reduced, and the use performance of the center line rubber-lined butterfly valve is effectively improved.

Description

Technical Field

[0001] The present invention relates to the field of valve technology, and in particular to a low-torque butterfly valve, a valve seat and a valve plate design method. Background Art

[0002] Compared to eccentric butterfly valves, centerline rubber-lined butterfly valves have a simpler structure, require no specialized tooling during manufacturing, and have lower processing equipment requirements. Therefore, centerline rubber-lined butterfly valves are very cost-effective to produce. Furthermore, due to their soft seal, centerline rubber-lined butterfly valves achieve zero leakage and are widely used in industries such as nuclear power, where sealing requirements are stringent. Therefore, centerline rubber-lined butterfly valves have enormous market value.

[0003] Existing centerline rubber-lined butterfly valves experience significant extrusion friction between the valve disc and valve seat during opening and closing, especially near the upper and lower positions where the valve stem and valve seat meet. Friction and wear occur at any angle during the valve disc opening and closing process. As the valve disc gradually closes, the extrusion friction increases as it moves further away from the upper and lower positions of the valve seat. Consequently, the lifespan of centerline rubber-lined butterfly valves is shorter than that of eccentric butterfly valves. Summary of the Invention

[0004] One objective of the present invention is to provide a low-torque butterfly valve to address the technical problem of existing centerline rubber-lined butterfly valves, which suffer from friction between the valve disc and valve seat at all opening and closing angles during opening and closing. Furthermore, as the valve disc gradually closes, the area of friction between the valve disc and valve seat gradually increases, resulting in a shorter service life for centerline rubber-lined butterfly valves compared to eccentric butterfly valves. A second objective is to provide a valve seat design method for a low-torque butterfly valve. A third objective is to provide a valve disc design method for a low-torque butterfly valve.

[0005] The present invention provides a low-torque butterfly valve, comprising:

[0006] The valve body is provided with a medium passage;

[0007] A flexible valve seat is provided on a side wall of the medium channel;

[0008] a valve plate located in the medium channel, the valve plate being configured to be in press contact with the flexible valve seat to seal the medium channel;

[0009] a valve stem extending radially along the valve plate and passing through the valve plate to be rotatably connected to the valve body;

[0010] an actuator connected to the valve stem, the actuator being used to drive the valve stem to rotate, thereby driving the valve plate to rotate, so that the valve plate opens or closes the medium channel;

[0011] Wherein, from the rotational connection position between the valve stem and the valve body, the width of the flexible valve seat gradually increases along the circumferential extension direction of the medium channel.

[0012] In one embodiment of the present invention, a penetration channel is provided on the valve plate, and the penetration channel is used for penetrating the valve stem.

[0013] In one embodiment of the present invention, a positioning seat is provided on the valve body, and the positioning seat is used to position and install the valve plate.

[0014] In one embodiment of the present invention, the positioning seat is a cylindrical positioning seat, and the outer diameter of the positioning seat is smaller than the through channel.

[0015] In one embodiment of the present invention, a rotation hole is formed on the positioning seat coaxially with the penetration hole, and the rotation hole is used for rotationally connecting to the valve stem.

[0016] In one embodiment of the present invention, a pin is provided between the valve stem and the valve plate, and the valve plate and the valve stem are connected via the pin.

[0017] In one embodiment of the present invention, the valve stem is interference-fitted with the penetration channel, a convex portion is provided on the valve stem, and the convex portion is clearance-fitted with the rotation hole.

[0018] In one embodiment of the present invention, an end cover is provided on the valve body, a sealing component is provided between the valve body and the end cover, the valve stem passes through the end cover and is connected to the actuator, and the sealing component is used to seal the gap between the valve stem and the valve body.

[0019] The present invention also provides a valve seat design method for a low-torque butterfly valve, which is applied to the low-torque butterfly valve described above. The valve seat design method includes:

[0020] A Y-axis is established along the axis of the valve stem, and an X-axis is established perpendicular to the axis of the valve stem. A coordinate system is established with the X-axis passing through the midpoint of the axis of the valve stem as the origin. The coordinate system and the flexible valve seat are located in the same plane.

[0021] A line connecting any point along the circumference of the medium channel and the origin forms an angle θ with the X-axis;

[0022] Analyzing the contact condition between the valve plate and the flexible valve seat at the angle θ;

[0023] A closing angle α between the valve plate and the flexible valve seat is preset, and at the angle α, the valve plate begins to contact the flexible valve seat;

[0024] The dimensional relationship at the position where the valve plate begins to contact the flexible valve seat is expressed as:

[0025] d=(r·sinα)·cosθ,θ∈[0°,90°],

[0026] Wherein d is half of the width of the raised sealing surface of the flexible valve seat, and r is the radius of the valve plate.

[0027] The present invention also provides a valve plate design method for a low-torque butterfly valve, which is applied to the low-torque butterfly valve described above. The valve plate design method includes:

[0028] The inner diameter of the flexible valve seat is preset to be D, and the outer diameter of the valve plate is preset to be R;

[0029] When the low-torque butterfly valve is applied to the working condition of 0-0.6 MPa, and the valve plate and the flexible valve seat are in the closed state, the radial extrusion amount between the valve plate and the flexible valve seat is preset to be L.

[0030] The outer diameter of the valve plate is expressed as:

[0031] R=D+L;

[0032] When the low-torque butterfly valve is applied to the working condition of 0.7-1 MPa, and the valve plate and the flexible valve seat are in the closed state, the radial extrusion amount of the valve plate and the flexible valve seat is preset to be 2L.

[0033] The outer diameter of the valve plate is expressed as:

[0034] R=D+2L;

[0035] When the low-torque butterfly valve is applied to the working condition of 1.1-1.6 MPa, and the valve plate and the flexible valve seat are in the closed state, the radial extrusion amount between the valve plate and the flexible valve seat is preset to be 3L.

[0036] The outer diameter of the valve plate is expressed as:

[0037] R=D+3L.

[0038] Beneficial effects of the present invention: The present invention proposes a design method for a low-torque butterfly valve, valve seat, and valve plate. By providing a flexible valve seat with gradually increasing width along the circumferential extension direction of the medium channel at the rotational connection position between the valve stem and the valve body on the side wall of the medium channel, the butterfly valve shown in the present invention only comes into squeeze contact with the flexible valve seat when the valve plate is closed to a set angle during the opening and closing process. Compared with the uniformly raised valve seat sealing surface of a conventional rubber-lined butterfly valve, this avoids the problem of constant high friction between the valve plate and the flexible valve seat during the opening and closing process of the valve plate, thereby effectively reducing the torque and friction wear of the centerline rubber-lined butterfly valve during the opening and closing process, and effectively improving the performance of the centerline rubber-lined butterfly valve. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The accompanying drawings are incorporated into and constitute a part of the specification, illustrate embodiments consistent with the present application, and together with the specification, are used to explain the principles of the present application. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without inventive effort.

[0040] In the attached figure:

[0041] Figure 1 A schematic structural diagram of a low-torque butterfly valve provided by one embodiment of the present invention;

[0042] Figure 2 for Figure 1 Schematic diagram of the AA section structure;

[0043] Figure 3 This is a schematic structural diagram of a valve body and a valve seat in a low-torque butterfly valve provided in one embodiment of the present invention;

[0044] Figure 4 This is a schematic structural diagram of a valve plate in a low-torque butterfly valve provided in one embodiment of the present invention;

[0045] Figure 5 A schematic plan view of the angle θ of a low-torque butterfly valve provided in an embodiment of the present invention when the valve disc is in a closed state;

[0046] Figure 6 A schematic cross-sectional view of a low-torque butterfly valve provided in one embodiment of the present invention when the valve plate at angle α contacts the flexible valve seat;

[0047] Figure 7 A flow chart showing a valve seat design method for a low-torque butterfly valve provided by one embodiment of the present invention;

[0048] Figure 8 A flow chart showing a method for designing a valve plate of a low-torque butterfly valve according to an embodiment of the present invention is shown.

[0049] The reference numerals are as follows:

[0050] Valve body 1, medium channel 101, positioning seat 102, rotating hole 102a, flexible valve seat 2, valve plate 3, penetration channel 301, valve stem 4, pin shaft 5, end cover 6, sealing component 7. DETAILED DESCRIPTION

[0051] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments. The details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention. The following embodiments and features therein may be combined with one another without conflict.

[0052] It should be noted that the illustrations provided in the following embodiments are merely schematic illustrations of the basic concept of the present invention. The drawings only show components related to the present invention and are not drawn according to the number, shape, and size of components in actual implementation. In actual implementation, the type, quantity, and proportion of each component may be changed arbitrarily, and the component layout may also be more complex.

[0053] In the following description, numerous details are discussed to provide a more thorough explanation of the embodiments of the present invention. However, it will be apparent to those skilled in the art that the embodiments of the present invention may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring the embodiments of the present invention.

[0054] Please combine Figures 1 to 6 As shown, the present invention provides a low-torque butterfly valve.

[0055] In an exemplary embodiment of the present application, a valve body 1 is provided with a medium channel 101; a flexible valve seat 2 is arranged on the side wall of the medium channel 101; a valve plate 3 is located in the medium channel 101, and the valve plate 3 is used to squeeze and contact the flexible valve seat 2 to seal the medium channel 101; a valve stem 4 extends radially along the valve plate 3 and passes through the valve plate 3 and is rotatably connected to the valve body 1; an actuator is connected to the valve stem 4, and the actuator is used to drive the valve stem 4 to rotate, so as to drive the valve plate 3 to rotate, so that the valve plate 3 opens or closes the medium channel 101; wherein, from the rotational connection position of the valve stem 4 and the valve body 1, the width of the flexible valve seat 2 gradually increases along the circumferential extension direction of the medium channel 101.

[0056] In this embodiment, a flexible valve seat 2 with gradually increasing width along the circumferential extension direction of the medium channel 101 is provided on the side wall of the medium channel 101 at the rotational connection position between the valve stem 4 and the valve body 1. This allows the butterfly valve shown in the present invention to only come into squeeze contact with the flexible valve seat 2 when the valve plate 3 is closed to a set angle during the opening and closing process. Compared to the uniformly raised valve seat sealing surface of a conventional rubber-lined butterfly valve, this avoids the problem of constant high friction between the valve plate 3 and the flexible valve seat 2 during the opening and closing process of the valve plate 3, thereby effectively reducing the torque and friction wear of the centerline rubber-lined butterfly valve during the opening and closing process, and effectively improving the performance of the centerline rubber-lined butterfly valve. Because the flexible valve seat 2 is designed to gradually increase in width along the circumferential extension direction of the medium channel 101 at the rotational connection position between the valve stem 4 and the flexible valve body 1, the valve plate 3 only comes into compression contact with the flexible valve seat 2 when the valve plate 3 is closed to a set angle. In the open and closed positions where the valve plate 3 and the flexible valve seat 2 are not in contact or compression, the actuator only needs to output a relatively low torque to drive the valve plate 3 to rotate, thereby effectively reducing the energy consumption of the actuator. The flexible valve seat 2 includes, but is not limited to, a rubber material, so that when the valve plate 3 comes into contact and compression with the flexible valve seat 2, the flexible valve seat 2 deforms, thereby achieving a sealing effect on the medium channel 101.

[0057] In an exemplary embodiment of the present application, a penetration channel 301 is provided on the valve plate 3 , and the penetration channel 301 is used for penetrating the valve stem 4 .

[0058] In this embodiment, the penetration channel 301 is opened along the radial direction of the valve plate 3 , and the valve stem 4 passes through the penetration channel 301 and is rotatably connected to the valve body 1 .

[0059] In an exemplary embodiment of the present application, a positioning seat 102 is provided on the valve body 1 , and the positioning seat 102 is used to position and install the valve plate 3 .

[0060] In this embodiment, by providing a positioning seat 102 on the valve body 1, the valve plate 3 can be quickly positioned and installed with the valve body 1, thereby effectively improving the installation efficiency.

[0061] In an exemplary embodiment of the present application, the positioning seat 102 is a cylindrical positioning seat 102 , and the outer diameter of the positioning seat 102 is smaller than the penetration channel 301 .

[0062] In this embodiment, the positioning seat 102 is designed to be cylindrical, and the outer diameter of the positioning seat 102 is smaller than the penetration channel 301 , so that the valve plate 3 can cooperate with the positioning seat 102 through the penetration channel 301 to achieve positioning installation of the valve plate 3 and the valve body 1 .

[0063] In an exemplary embodiment of the present application, a rotation hole 102 a is provided on the positioning seat 102 coaxially with the through hole, and the rotation hole 102 a is used for rotationally connecting to the valve stem 4 .

[0064] In this embodiment, by providing a rotation hole 102a in the positioning seat 102, when the valve stem 4 passes through the through-channel 301 in the valve plate 3 and engages with the rotation hole 102a, a rotational connection between the valve stem 4 and the valve body 1 is achieved. The outer diameter of the valve stem 4 is smaller than the inner diameter of the rotation hole 102a.

[0065] In an exemplary embodiment of the present application, a pin shaft 5 is provided between the valve stem 4 and the valve plate 3 , and the valve plate 3 and the valve stem 4 are connected via the pin shaft 5 .

[0066] In this embodiment, the valve plate 3 and the valve stem 4 are fixedly connected via a pin 5 , so that the valve stem 4 can drive the valve plate 3 to rotate.

[0067] In an exemplary embodiment of the present application, the valve stem 4 is interference-fitted with the penetration channel 301 , and a convex portion is provided on the valve stem 4 , which is clearance-fitted with the rotation hole 102 a .

[0068] In this embodiment, the valve stem 4 is fixedly connected to the valve plate 3 by means of an interference fit with the through-channel 301, so that the valve stem 4 can drive the valve plate 3 to rotate; the valve stem 4 is rotationally connected to the valve body 1 by means of a clearance fit between the convex portion provided on the axial end and the rotating hole 102a.

[0069] In an exemplary embodiment of the present application, an end cover 6 is provided on the valve body 1, a sealing component 7 is provided between the valve body 1 and the end cover 6, the valve stem 4 passes through the end cover 6 and is connected to the actuator, and the sealing component 7 is used to seal the gap between the valve stem 4 and the valve body 1.

[0070] In this embodiment, the end cap 6 is connected to the valve body 1 by bolts. The bolted connection causes the end cap 6 to squeeze the sealing component 7, providing a sealing preload force for the sealing component 7, causing the sealing component 7 to elastically deform, thereby sealing the gap between the valve stem 4 and the valve body 1. The sealing component 7 includes, but is not limited to, an O-ring.

[0071] Please combine Figure 7 As shown, the present invention provides a valve seat design method for a low-torque butterfly valve.

[0072] In an exemplary embodiment of the present application, the valve seat design method includes at least steps S710 to S750.

[0073] In step S710, a vertical coordinate Y axis is established along the axis of the valve stem 4, a horizontal coordinate X axis is established perpendicular to the axis of the valve stem 4, and a coordinate system is established with the X axis passing through the midpoint of the axis of the valve stem 4 as the origin. The coordinate system is located in the same plane as the flexible valve seat 2.

[0074] In step S720 , a line is drawn between any point on the circumference of the medium channel 101 and the origin, and an angle θ is formed between the line and the X-axis.

[0075] In step S730 , the contact condition between the valve plate 3 and the flexible valve seat 2 at the angle θ is analyzed.

[0076] In step S740 , a closing angle α between the valve plate 3 and the flexible valve seat 2 is preset. At the angle α, the valve plate 3 begins to contact the flexible valve seat 2 .

[0077] In step S750, the dimensional relationship existing at the position where the valve plate 3 begins to contact the flexible valve seat 2 is expressed as:

[0078] d=(r·sinα)·cosθ,θ∈[0°,90°],

[0079] Wherein d is half of the width of the raised sealing surface of the flexible valve seat 2 , and r is the radius of the valve plate 3 .

[0080] In this embodiment, the contact between the valve plate 3 and the flexible valve seat 2 is analyzed at an angle θ with the vertical plane of the valve stem 4. It is assumed that the valve plate 3 begins to contact the flexible valve seat 2 when the closing angle is α, and a dimensional relationship d=rcosθ·sinα is established, where d is half the width of the convex sealing surface of the flexible valve seat 2, and r is the radius of the valve plate 3. When α is a certain value, θ is at any position in the range of 0° to 90°, and contacts the flexible valve seat 2 when the valve plate 3 is closed to the angle α, and this dimensional relationship can be converted into

[0081] d=(r·sinα)·cosθ, equation ①

[0082] The width of the flexible valve seat 2 is made to be a cosine function curve of θ to optimize the structure.

[0083] In three-dimensional design, it is difficult to design a spatial cosine curve. To simplify the three-dimensional design, the valve seat edge curve can be designed by designing the required curve on a plane and then projecting it onto the target surface. The midpoint of the vertical valve stem 4 is taken as the coordinate origin. This position corresponds to θ = 0°, ordinate y = d, and abscissa x = r·sinθ (x∈[0, r]). Substituting the above dimensional relationship into ①, we get

[0084]

[0085] That is, the edge line of the flexible valve seat 2 is an elliptical curve The edge curve of the flexible valve seat 2 is designed by first designing the curve on a plane and then projecting it onto the target surface.

[0086] The valve seat design method of the low-torque butterfly valve shown in the embodiment of the present application adopts a cosine function curve to design the sealing surface width of the flexible valve seat 2. The sealing surface width (d value) of the contact point between the valve plate 3 and the flexible valve seat 2 varies with the angle θ like a cosine function. Compared with the traditional uniformly raised valve seat width sealing surface design, it can effectively reduce the opening and closing torque of the valve, greatly reduce the power requirement of the actuator, and effectively reduce the wear of the rubber sealing surface, and the service life of the flexible valve seat 2 is effectively improved.

[0087] Please combine Figure 8 As shown, the present invention provides a design method for the valve plate 3 of a low-torque butterfly valve.

[0088] In an exemplary embodiment of the present application, the valve plate 3 design method includes at least steps S810 to S840.

[0089] In step S810 , the inner diameter of the flexible valve seat 2 is preset to be D, and the outer diameter of the valve plate 3 is preset to be R.

[0090] In step S820, when the low-torque butterfly valve is applied to the working condition of 0-0.6 MPa and the valve plate 3 and the flexible valve seat 2 are in the closed state, the radial extrusion amount between the valve plate 3 and the flexible valve seat 2 is preset to L.

[0091] The outer diameter of the valve plate 3 is expressed as:

[0092] R=D+L.

[0093] In step S830, when the low-torque butterfly valve is applied to the working condition of 0.7-1 MPa, and the valve plate 3 and the flexible valve seat 2 are in the closed state, the radial extrusion amount between the valve plate 3 and the flexible valve seat 2 is preset to 2L.

[0094] The outer diameter of the valve plate 3 is expressed as:

[0095] R=D+2L.

[0096] In step S840, when the low-torque butterfly valve is applied to the working condition of 1.1-1.6 MPa, and the valve plate 3 and the flexible valve seat 2 are in the closed state, the radial extrusion amount between the valve plate 3 and the flexible valve seat 2 is preset to 3L.

[0097] The outer diameter of the valve plate 3 is expressed as:

[0098] R=D+3L.

[0099] In this embodiment, valve plates 3 of different sizes and specifications can be selected according to the medium pressure under different working conditions to reduce the working torque of the actuator, thereby reducing the configuration cost of the centerline rubber-lined butterfly valve.

[0100] For example, since the center line rubber lined butterfly valve forms a seal by squeezing the protrusion of the valve plate 3 and the rubber valve seat, when the squeezing amount is large, good sealing performance can be guaranteed in the range of low pressure difference to high pressure difference. However, the opening and closing torque of the butterfly valve will also increase accordingly, resulting in an increase in the configuration of the actuator, increasing the cost of the butterfly valve, and the friction and wear between the valve seat and the valve plate 3 will also increase, resulting in a reduced service life of the butterfly valve.

[0101] Therefore, in order to increase the service life of the rubber-lined butterfly valve and reduce costs, the extrusion between the valve plate 3 and the valve seat is designed according to different pressure differentials. When the pressure differential is within the range of 0.6MPa, 1MPa, and 1.6MPa, the outer diameter of the contact point between the valve plate 3 and the valve seat is D+L, D+2L, and D+3L, respectively, where D is the inner diameter of the valve seat and L is the radial extrusion between the valve plate 3 and the valve seat. When the pressure differential is within the range of 0.6MPa, the radial extrusion between the valve plate 3 and the valve seat is L; when it is within the range of 0.7-1MPa, the radial extrusion between the valve plate 3 and the valve seat is 2L; and when it is within the range of 1.1MPa-1.6MPa, the radial extrusion is 3L. For non-metallic materials, the greater the deformation, the smaller the extrusion that can be achieved. By designing the sealing outer diameter of the valve plate 3 according to different pressure differentials, the butterfly valve can reduce the radial extrusion with the valve seat at low pressure differentials. While ensuring sealing, it can effectively reduce the friction between the valve plate 3 and the valve seat, thereby reducing the actuator torque, and further reducing the actuator configuration and the overall machine cost.

[0102] The working principle is that by disposing a valve seat with gradually increasing width along the circumferential extension of the medium channel 101 at the rotational connection point between the valve stem 4 and the valve body 1 on the side wall of the medium channel 101, the butterfly valve shown in the present invention only comes into contact with the valve seat when the valve plate 3 is closed to a set angle during the opening and closing process. Compared to the uniformly raised valve seat sealing surface of conventional rubber-lined butterfly valves, this avoids the problem of high friction between the valve plate 3 and the valve seat during the opening and closing process, thereby effectively reducing the torque and friction wear of the centerline rubber-lined butterfly valve during opening and closing, and effectively improving the performance of the centerline rubber-lined butterfly valve.

[0103] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A low torque butterfly valve, characterized in that: include: The valve body is provided with a medium passage; A flexible valve seat is provided on a side wall of the medium channel; a valve plate located in the medium channel, the valve plate being configured to be in press contact with the flexible valve seat to seal the medium channel; a valve stem extending radially along the valve plate and passing through the valve plate to be rotatably connected to the valve body; an actuator connected to the valve stem, the actuator being used to drive the valve stem to rotate, thereby driving the valve plate to rotate, so that the valve plate opens or closes the medium channel; Wherein, from the rotational connection position between the valve stem and the valve body, the width of the flexible valve seat gradually increases along the circumferential extension direction of the medium channel.

2. The low torque butterfly valve according to claim 1, characterized in that: A penetration channel is provided on the valve plate, and the penetration channel is used for penetrating the valve stem.

3. The low torque butterfly valve according to claim 2, characterized in that: A positioning seat is provided on the valve body, and the positioning seat is used for positioning and installing the valve plate.

4. The low torque butterfly valve according to claim 3, characterized in that: The positioning seat is a cylindrical positioning seat, and the outer diameter of the positioning seat is smaller than the penetration channel.

5. The low torque butterfly valve according to claim 4, characterized in that: A rotation hole is provided on the positioning seat coaxially with the penetration hole, and the rotation hole is used for rotationally connecting with the valve stem.

6. The low torque butterfly valve according to claim 1, characterized in that: A pin is provided between the valve stem and the valve plate, and the valve plate and the valve stem are connected via the pin.

7. The low torque butterfly valve according to claim 5, characterized in that: The valve stem is interference-fitted with the penetration channel, and a convex portion is provided on the valve stem, and the convex portion is clearance-fitted with the rotation hole.

8. The low torque butterfly valve according to claim 1, characterized in that: An end cover is provided on the valve body, a sealing component is provided between the valve body and the end cover, the valve stem passes through the end cover and is connected to the actuator, and the sealing component is used to seal the gap between the valve stem and the valve body.

9. A valve seat design method for a low-torque butterfly valve, applied to the low-torque butterfly valve according to any one of claims 1 to 8, characterized in that: The valve seat design method includes: A Y-axis is established along the axis of the valve stem, and an X-axis is established perpendicular to the axis of the valve stem. A coordinate system is established with the X-axis passing through the midpoint of the axis of the valve stem as the origin. The coordinate system and the flexible valve seat are located in the same plane. A line connecting any point along the circumference of the medium channel and the origin forms an angle θ with the X-axis; Analyzing the contact condition between the valve plate and the flexible valve seat at the angle θ; A closing angle α between the valve plate and the flexible valve seat is preset, and at the angle α, the valve plate begins to contact the flexible valve seat; The dimensional relationship at the position where the valve plate begins to contact the flexible valve seat is expressed as: d=(r·sinα)·cosθ,θ∈[0°,90°], Wherein d is half of the width of the raised sealing surface of the flexible valve seat, and r is the radius of the valve plate.

10. A valve plate design method for a low-torque butterfly valve, applied to the low-torque butterfly valve according to any one of claims 1 to 8, characterized in that: The valve plate design method includes: The inner diameter of the flexible valve seat is preset to be D, and the outer diameter of the valve plate is preset to be R; When the low-torque butterfly valve is applied to the working condition of 0-0.6 MPa, and the valve plate and the flexible valve seat are in the closed state, the radial extrusion amount between the valve plate and the flexible valve seat is preset to be L. The outer diameter of the valve plate is expressed as: R=D+L; When the low-torque butterfly valve is applied to the working condition of 0.7-1 MPa, and the valve plate and the flexible valve seat are in the closed state, the radial extrusion amount of the valve plate and the flexible valve seat is preset to be 2L. The outer diameter of the valve plate is expressed as: R=D+2L; When the low-torque butterfly valve is applied to a working condition of 1.1-1.6 MPa, and the valve plate and the flexible valve seat are in a closed state, the radial extrusion amount between the valve plate and the flexible valve seat is preset to be 3L, and the outer diameter of the valve plate is expressed as: R=D+3L.

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