Butterfly valve stem concentricity assembly equipment and method based on mechanical positioning

Abstract

This invention relates to the field of precision machinery manufacturing, specifically to a butterfly valve stem concentricity assembly device based on mechanical positioning. It includes modules for main pressure drive, mechanical locking, air-float compliance, and air path control. The device uses a servo motor to drive the main pressure rod and push head to press down the valve stem, and utilizes a wave spring and a wedge-shaped expansion ring with a conical surface to achieve mechanical linkage. Its core is that in the initial stage of assembly, positive pressure is introduced through a microporous ceramic layer to form an air-float boundary layer, converting solid friction into viscous friction to provide radial compliance. In the final stage of assembly, when resistance increases, a vacuum generator removes the air film, forcing the expansion ring to contract and rigidly lock the valve stem to provide high axial load-bearing capacity. This invention eliminates external grippers and uses air film transformation and mechanical conical surface cooperation to solve the problems of easy scratching and pressure buckling deformation of slender valve stems in traditional assembly, achieving a rigid-flexible switching of the assembly state and effectively improving the efficiency and concentricity of precision assembly.

Description

Technical Field

[0001] This invention relates to the fields of automated assembly and precision machinery manufacturing, specifically to a butterfly valve stem concentricity assembly equipment and method based on mechanical positioning. Background Technology

[0002] In the fields of automated mechanical assembly and precision machining, the slender valve stems of fluid control equipment such as butterfly valves and plunger pumps require extremely high concentricity and axial assembly accuracy when being assembled through shafts into deep blind holes, water-blocking rings, and splined holes in the valve body. Existing assembly solutions generally use rigid main pressure rods and traditional mechanical guide sleeves for forceful pressing. Although this solution is feasible to a certain extent in conventional low-precision assembly scenarios, it lacks effective perception of the microscopic contact state inside the deep hole, and the rigid transmission structure cannot reduce the periodic disturbances caused by mechanical installation errors. When assembling slender valve stems, it cannot simultaneously consider the radial compliance of the initial section and the axial load-bearing capacity of the final section, which easily leads to buckling deformation of the slender valve stem under pressure during deep hole assembly. At the same time, due to the lack of a precise correction and high-rigidity locking switching mechanism, the valve stem surface often suffers severe scoring and scratches, and may even cause the bottom bearing to break.

[0003] Therefore, how to improve the position perception accuracy, real-time correction capability, and efficient switching between rigid and flexible assembly states during the deep hole assembly process of slender valve stems without introducing complex external gripper mechanisms has become an urgent technical problem to be solved. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides a butterfly valve stem concentricity assembly device and method based on mechanical positioning. Specifically, the technical solution of the present invention is as follows:

[0005] Mechanical positioning-based butterfly valve stem concentricity assembly equipment includes:

[0006] The assembly frame has a top horizontal surface and a bottom plate;

[0007] A servo motor, fixed to the top horizontal surface, has an output shaft;

[0008] A ball screw is connected to the output shaft;

[0009] The lead screw nut is threaded with the ball screw and has a flange face.

[0010] The main pressure rod is fixed to the flange face and has a hollow cylindrical structure inside to accommodate the butterfly valve stem;

[0011] A wave spring is connected to the bottom end face of the main pressure rod;

[0012] A pusher head is connected to the wave spring, with an outer conical surface on its outer circumference and its bottom surface abutting against the top of the butterfly valve stem.

[0013] The guide sleeve is fixed to the lower base plate and is coaxial with the main pressure rod.

[0014] A wedge-shaped tightening ring is placed in the inner hole at the top of the guide sleeve. The inner hole has an inner conical surface that mates with the outer conical surface, and its outer circle is in clearance fit with the inner hole of the guide sleeve.

[0015] A microporous ceramic layer is bonded to the lower inner wall of the guide sleeve, with an independent air chamber between the two.

[0016] It includes a pneumatic proportional valve and a vacuum generator, each connected to the independent air chamber via an independent air pipe;

[0017] The controller connects to and controls the servo motor, pneumatic proportional valve, and vacuum generator.

[0018] Preferably, the output shaft of the servo motor is connected to the top of the ball screw via a plum blossom-shaped flexible coupling; the ball screw is supported in the inner cavity of the assembly frame by an angular contact ball bearing.

[0019] Preferably, the outer diameter of the main pressure rod is 50mm and the inner diameter of the main pressure rod is 30mm.

[0020] Preferably, the inner diameter of the microporous ceramic layer is larger than the outer diameter of the butterfly valve stem; the independent air chambers are evenly distributed along the circumferential direction.

[0021] Preferably, the inclination angle of the outer conical surface of the pusher and the inner conical surface of the wedge-shaped tightening ring are both 15°.

[0022] Preferably, the pusher is configured to move downward when subjected to the axial thrust of the main pressure rod and to press the inner cone surface with the outer cone surface.

[0023] A control method for the concentricity of butterfly valve stems in assembly equipment based on mechanical positioning includes:

[0024] S1. Real-time acquisition of the operating current data of the servo motor, the air pressure data of the independent air chamber, and the real-time downward displacement of the main pressure rod, and calculation of the real-time overhang length of the butterfly valve stem;

[0025] S2. Calculate the current harmonic integral characterizing the high-frequency resistance torque disturbance based on the operating current data;

[0026] S3. Calculate the back pressure differential gradient based on the air pressure data of the relatively arranged independent air chambers;

[0027] S4. The axial interference resistance and actual position deviation angle are calculated back based on the current harmonic integral, the back pressure differential gradient and the real-time overhang length.

[0028] S5. Control the operation of the pneumatic proportional valve and the vacuum generator according to the actual position deviation angle and the axial interference resistance, so as to adjust the axial pressing state and radial position of the butterfly valve stem in the guide sleeve.

[0029] Preferably, step S4 specifically includes:

[0030] The radial eccentricity is obtained by multiplying the back pressure differential gradient by a conversion factor.

[0031] The axial interference resistance is obtained by multiplying the current harmonic integral by the mechanical conversion factor.

[0032] The actual pose angle is calculated by combining the radial eccentricity and the axial interference resistance using trigonometric functions.

[0033] Preferably, step S5 specifically includes:

[0034] S501. When the actual position deviation angle is less than the preset critical deviation angle threshold, the pneumatic proportional valve is controlled to introduce a positive pressure airflow of equal pressure into the independent air chamber so as to form an air-floating boundary layer on the surface of the butterfly valve stem through the microporous ceramic layer.

[0035] S502. When the actual position deviation angle is greater than or equal to the preset critical deviation angle threshold and the axial interference resistance is less than or equal to the preset spline engagement threshold, the downward pressing speed of the servo motor is maintained, and the pneumatic proportional valve is controlled to increase the intake pressure in the independent air chamber on the eccentric side and decrease the intake pressure in the independent air chamber on the opposite side to form a pneumatic micro-correction torque.

[0036] Preferably, step S5 further includes:

[0037] S503. When the axial interference resistance is greater than the preset spline engagement threshold, control the vacuum generator to start and extract the air in the independent air chamber to eliminate the air floating boundary layer; control the servo motor to continue pressing down to compress the wave spring, the main pressure rod pushes the push head to move downward, and the outer cone surface squeezes the inner cone surface to force the wedge-shaped tightening ring to contract towards the center and radially clamp and lock the butterfly valve stem.

[0038] The present invention has the following beneficial effects:

[0039] 1. This invention utilizes the mechanical linkage of a main pressure rod, wave spring, pusher, and wedge-shaped expansion ring, and connects a pneumatic proportional valve and a vacuum generator by fixing a microporous ceramic layer on the inner wall of the guide sleeve. In the initial stage of assembly, a positive pressure airflow is introduced to form an air-floating boundary layer, which converts the solid friction between the valve stem and the sleeve into viscous friction, providing radial compliance and preventing scratches on the valve stem surface. In the final stage of assembly, when the resistance increases, air is extracted to eliminate the air film and the outer conical surface squeezes the inner conical surface, forcing the wedge-shaped expansion ring to contract towards the center to rigidly lock the valve stem, providing axial load-bearing capacity. This allows for efficient switching between rigid and flexible assembly states without the need for external clamps, effectively preventing the slender valve stem from buckling deformation under pressure.

[0040] 2. This invention acquires real-time data on the servo motor's operating current and independent air chamber pressure, extracts and integrates the harmonic amplitude of the current in a specific frequency band using Fast Fourier Transform, and simultaneously calculates the difference in the rate of change of air pressure between the relatively arranged air chambers to obtain the back pressure differential gradient. This is used to inversely calculate the axial interference resistance and the actual posture deviation angle. This not only eliminates the periodic mechanical disturbances caused by frame installation errors but also solves the problem of unmeasurable micro-contact states inside deep blind holes. When the actual posture deviation angle exceeds the standard and the resistance does not reach the engagement threshold, a pneumatic micro-correction torque is formed by controlling the inlet pressure difference between the relative air chambers, achieving refined dynamic posture correction and significantly reducing the risk of bottom bearing breakage and damage. Attached Figure Description

[0041] The following drawings, illustrating embodiments of this application, are incorporated herein by reference and are used to understand this application. The drawings illustrate embodiments of this application and their descriptions, serving to explain the principles of this application. In the drawings,

[0042] Figure 1 This is a schematic diagram of the overall structure of the device;

[0043] Figure 2 This is a cross-sectional view of the guide sleeve of the device;

[0044] Figure 3 This is a schematic diagram of the wedge-shaped expansion ring and inner conical surface structure of the device;

[0045] Figure 4 This is a schematic diagram of the wedge-shaped tightening ring structure of the device;

[0046] Figure 5 This is a flowchart of the method of the present invention.

[0047] In the diagram: 1. Assembly frame; 2. Top horizontal plane; 3. Lower base plate; 4. Servo motor; 5. Output shaft; 6. Ball screw; 7. Screw nut; 8. Flange face; 9. Main pressure rod; 10. Hollow cylindrical structure; 11. Wave spring; 12. Push head; 13. Outer conical surface; 14. Guide sleeve; 15. Wedge-shaped expansion ring; 16. Inner conical surface; 17. Microporous ceramic layer; 18. Independent air chamber; 19. Pneumatic proportional valve; 20. Vacuum generator; 21. Independent air pipe; 22. Controller; 23. Plum blossom-shaped flexible coupling; 24. Angular contact ball bearing; 25. Butterfly valve stem. Detailed Implementation

[0048] In the following description, numerous specific details are set forth to provide a more thorough understanding of this application. However, it will be apparent to those skilled in the art that embodiments of this application may be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described to avoid confusion with embodiments of this application.

[0049] Example 1:

[0050] Combination Figure 1 As shown, the butterfly valve stem concentricity assembly equipment based on mechanical positioning includes:

[0051] The assembly frame 1 has a top horizontal surface 2 and a bottom plate 3;

[0052] Servo motor 4 is fixed to the top horizontal surface 2 and has an output shaft 5;

[0053] Ball screw 6 is connected to output shaft 5;

[0054] The lead screw nut 7 is threaded with the ball screw 6 and has a flange face 8.

[0055] The main pressure rod 9 is fixed to the flange face 8 and has a hollow cylindrical structure 10 that accommodates the butterfly valve stem 25.

[0056] Wave spring 11 is connected to the bottom end face of main pressure rod 9;

[0057] Push head 12 is connected to wave spring 11, with an outer conical surface 13 on its outer circumference and its bottom surface abutting against the top of butterfly valve stem 25;

[0058] Guide sleeve 14 is fixed to the lower base plate 3 and is coaxial with the main pressure rod 9;

[0059] A wedge-shaped tightening ring 15 is placed in the inner hole at the top of the guide sleeve 14. The inner hole is provided with an inner conical surface 16 that mates with the outer conical surface 13, and its outer circle is in clearance fit with the inner hole of the guide sleeve 14.

[0060] A microporous ceramic layer 17 is bonded to the lower inner wall of the guide sleeve 14, with an independent air chamber 18 between the two.

[0061] It includes a pneumatic proportional valve 19 and a vacuum generator 20, which are connected to an independent air chamber 18 via independent air pipes 21;

[0062] Controller 22 connects to and controls servo motor 4, pneumatic proportional valve 19 and vacuum generator 20;

[0063] A set of vertically arranged butterfly valve stem 25 concentricity assembly equipment is used to complete the through-shaft assembly of the slender valve stem into the deep blind hole of the valve body; the assembly frame 1 adopts a portal bearing structure formed by welding and machining. The top horizontal surface 2 is used to install the servo motor 4, and the lower base plate 3 is used to install the guide sleeve 14 and the butterfly valve body to be installed. The verticality between the top horizontal surface 2 and the lower base plate 3 is controlled to be no more than 0.02mm per 300mm to ensure that the downward trajectory of the main pressure rod 9 is consistent with the center line of the valve body hole system.

[0064] The servo motor 4 is an AC servo motor with a current sampling interface, and its rated power can be from 750W to 1500W. The output shaft 5 is connected to the ball screw 6. The rotational motion output by the servo motor 4 is converted into axial linear feed by the ball screw 6 and the screw nut 7. The flange face 8 of the screw nut 7 is rigidly connected to the main pressure rod 9, so that the main pressure rod 9 moves downward along the guide direction of the frame. The main pressure rod 9 adopts a hollow cylindrical structure 10, and its internal channel is used to fit the valve stem 25 of the butterfly valve to be installed, so as to reduce the external size of the structure and improve the axial force symmetry.

[0065] A wave spring 11 is positioned between the bottom end face of the main pressure rod 9 and the push head 12. It provides axial elastic clearance during assembly, absorbs the instantaneous impact generated when the valve stem enters the spline engagement area, and provides controlled displacement for the cone-shaped linkage between the push head 12 and the wedge-shaped expansion ring 15. The bottom surface of the push head 12 contacts the top of the butterfly valve stem 25 to transmit force. The outer cone surface 13 of the outer circumference of the push head 12 cooperates with the inner cone surface 16 of the inner hole of the wedge-shaped expansion ring 15. When the wave spring 11 is compressed, the axial thrust is converted into the radial contraction force of the wedge-shaped expansion ring 15. The guide sleeve 14 is fixed on the lower base plate 3 of the assembly frame 1 and remains coaxial with the main pressure rod 9. It is used to establish the geometric reference during the valve stem insertion process.

[0066] A microporous ceramic layer 17 is bonded to the lower inner wall of the guide sleeve 14. The microporous ceramic layer 17 is a gas permeation medium with uniformly connected micropores. Its function in this invention is not a conventional wear-resistant lining, but to establish a controllable annular gas film on the outer surface of the valve stem. An independent gas chamber 18 is opened between the microporous ceramic layer 17 and the inner wall of the guide sleeve 14. Preferably, there are four fan-shaped gas chambers evenly distributed along the circumference. Each independent gas chamber 18 is connected to a pneumatic proportional valve 19 and a vacuum generator 20 through a gas pipe. The pneumatic proportional valve 19 is used to regulate the positive pressure gas supply, and the vacuum generator 20 is used to extract air from the gas chamber to form a negative pressure adsorption.

[0067] The controller 22 can be an industrial controller 22 or a motion controller 22, which is electrically connected to the servo motor 4, the pneumatic proportional valve 19 and the vacuum generator 20 to execute variable stiffness control logic based on current harmonic integral and back pressure differential gradient. During assembly and operation, when the valve stem enters the guide sleeve 14, the controller 22 controls the pneumatic proportional valve 19 to supply a set pressure airflow to the independent air chamber 18. The gas passes through the microporous ceramic layer 17 to form a uniform air-floating boundary layer on the outer surface of the valve stem, which converts the solid friction between the valve stem and the guide sleeve 14 into viscous friction to reduce the insertion force and the probability of surface scratches.

[0068] When the valve stem is misaligned, the controller 22 controls each independent air chamber 18 to form a differential pressure distribution to generate a radial correction force; when the valve stem enters the spline engagement area and the resistance increases, the controller 22 controls the vacuum generator 20 to evacuate air and maintain the servo motor 4 to press down, so that the wedge-shaped tightening ring 15 radially contracts to clamp the valve stem, completing the switch from the conformal guiding state to the high rigidity press-fit state.

[0069] Through the above structural combination, the equipment has both radial compliance capability in the initial assembly stage and axial load-bearing capability in the final assembly stage, which can reduce the probability of slender valve stem buckling under pressure, surface scratches, and bottom bearing breakage.

[0070] Combination Figure 2 As shown, the output shaft 5 of the servo motor 4 is connected to the top of the ball screw 6 through a plum blossom-shaped flexible coupling 23; the ball screw 6 is supported in the inner cavity of the assembly frame 1 by an angular contact ball bearing 24.

[0071] A plum blossom-shaped flexible coupling 23 is provided between the output shaft 5 of the servo motor 4 and the top of the ball screw 6. The plum blossom-shaped flexible coupling 23 consists of two half couplings and an intermediate elastic body. It can compensate for the radial installation deviation of less than 0.1mm and the angular installation deviation of less than 0.5° between the axis of the output shaft 5 of the servo motor 4 and the axis of the ball screw 6, and weaken the impact transmission when the motor reverses at high speed.

[0072] The technical consideration for adopting this connection method is that the present invention needs to extract the harmonic amplitude in the 50 to 100 Hz frequency band from the operating current of the servo motor 4. If a rigid coupling is used directly, the small assembly error of the assembly frame 1 will introduce additional periodic mechanical disturbances, interfering with the accuracy of the current harmonics in characterizing the micro-friction state of the deep hole. Using a plum blossom-shaped flexible coupling 23 can control the high-frequency interference caused by installation errors to a low level, thereby improving the availability of the current harmonic integration.

[0073] The ball screw 6 is supported in the inner cavity of the assembly frame 1 by two sets of upper and lower angular contact ball bearings 24. The upper set of angular contact ball bearings 24 can be arranged back to back to bear the axial positioning force and overturning moment, while the lower set of angular contact ball bearings 24 can be arranged face to face to bear the reverse axial load during the pressing process. The axial distance between the two sets of bearings can be 120mm to 220mm.

[0074] The preload of the angular contact ball bearing 24 can be set from 0.01mm to 0.03mm to reduce the axial movement and return clearance when the main pressure rod 9 is pressed down. This support method enables the ball screw 6 to maintain high rotational accuracy and axial positioning accuracy when it is subjected to the driving torque of the servo motor 4 and the downward pressure of the main pressure rod 9. When combined with the plum blossom-shaped flexible coupling 23, linear feed can be completed while taking into account both transmission smoothness and detection signal purity.

[0075] In actual assembly, the lead of the ball screw 6 can be 5mm or 10mm. Combined with the encoder feedback of the servo motor 4, the feed resolution of the main pressure rod 9 can be controlled at the level of 0.01mm. This allows the valve stem to have distinguishable displacement characteristics at each stage of entering the bearing hole, water blocking ring and butterfly plate spline hole. This is beneficial for the controller 22 to time-align the mechanical displacement state with the current harmonics and back pressure gradient data.

[0076] The outer diameter of the main pressure rod 9 is 50mm, and the inner diameter of the main pressure rod 9 is 30mm;

[0077] The main pressure rod 9 adopts a hollow cylindrical structure 10 with an outer diameter of 50mm and an inner diameter of 30mm. The material can be 12CrMo tempered steel or 45 steel with surface nitriding treatment. The length can be set from 250mm to 450mm according to the equipment stroke. The above-mentioned size configuration is intended to achieve a balance between axial pressing stiffness, internal accommodation space and the overall machine motion inertia.

[0078] The outer diameter of 50mm allows the moment of inertia of the main pressure rod 9 to meet the bending resistance requirements during the pressing process. When the rated axial thrust is 3000N to 8000N, the elastic deflection of the main pressure rod 9 itself can be controlled within the tolerance range, avoiding additional eccentricity caused by the deflection of the main pressure rod 9.

[0079] The inner diameter of 30mm is used to accommodate the upper end of the butterfly valve stem 25 and to make way for part of the stroke of the push head 12 and the wave spring 11, ensuring that the main pressure rod 9 will not make additional contact with the outer wall of the valve stem when it moves downward; the ratio of the outer diameter to the inner diameter of the main pressure rod 9 is also related to the arrangement space of the wave spring 11. Under this size, a sufficient annular mounting surface can be formed at the bottom of the main pressure rod 9 to stably support the wave spring 11 and reduce the off-center load during the spring compression process;

[0080] The hollow structure can reduce the mass of moving parts. Compared with a solid pressure bar of the same outer diameter, it can reduce the moment of inertia and linear feed inertial force, which is beneficial for the servo motor 4 to maintain speed stability when the assembly resistance changes suddenly. It ensures that the harmonic changes in the motor operating current are mainly caused by the contact state between the valve stem and the deep hole, rather than by the drive fluctuation caused by the excessive mass of the main pressure bar 9.

[0081] In actual processing, the coaxiality of the inner hole of the main pressure rod 9 can be controlled within 0.02mm, and the flatness of the bottom end face can be controlled within 0.01mm, so as to ensure that the wave spring 11 is compressed evenly and maintains the downward direction of the push head 12 consistent with the center line of the main pressure rod 9.

[0082] The inner diameter of the microporous ceramic layer 17 is larger than the outer diameter of the butterfly valve stem 25; the independent air chambers 18 are evenly distributed along the circumference.

[0083] The microporous ceramic layer 17 is disposed on the lower inner wall of the guide sleeve 14, and its inner diameter is slightly larger than the outer diameter of the butterfly valve stem 25 to form an annular gas film gap in the gas supply state. For the butterfly valve stem 25 with an outer diameter of 12mm to 22mm, the inner diameter of the microporous ceramic layer 17 is preferably 0.03mm to 0.2mm larger than the outer diameter of the valve stem. When the gap is less than 0.03mm, microporous blockage or small protrusions on the valve stem surface can easily cause local rubbing. When the gap is greater than 0.2mm, the gas film bearing stiffness decreases and the mapping sensitivity of the back pressure differential gradient to the eccentric displacement weakens.

[0084] The thickness of the microporous ceramic layer 17 can be 3mm to 8mm, the average pore size can be 5μm to 25μm, and the porosity can be 20% to 40%, so as to balance gas permeability and structural strength; the independent gas chambers 18 are evenly distributed along the circumference, preferably set as four gas chambers spaced 90° apart from each other, corresponding to the four directions of up, down, left and right respectively;

[0085] The technical consideration of the four-chamber structure is that two relatively arranged chambers can form a set of back pressure measurement channels to obtain pressure change information in at least two orthogonal directions, thereby determining the direction and degree of valve stem eccentricity; the axial length of each independent chamber 18 can be 20mm to 50mm, the circumferential angle can be 60° to 80°, and the chamber depth can be 1.6mm to 3mm. Gas distribution is achieved between the chamber and the microporous ceramic layer 17 through a uniform contact surface;

[0086] When the valve stem is centered, the gas seepage channels of the four independent gas chambers 18 have approximately the same impedance, and the pressure change rate of the gas chambers is nearly consistent. When the valve stem is eccentric, the gas film gap near the eccentric side decreases, the local flow resistance increases, and the pressure change rate of the corresponding gas chamber increases, while the opposite change occurs on the opposite side. The controller 22 obtains the back pressure differential gradient by comparing the difference in the rate of change of the relatively arranged gas chambers. This parameter is not equivalent to the pressure loss of conventional pipelines, but reflects the transient response of the microscale gas film inside and outside the microporous ceramic layer 17 under the squeezing effect.

[0087] By coordinating the design of the inner diameter of the microporous ceramic layer 17, the outer diameter of the valve stem, and the independent air chamber 18 in a uniform manner, the valve stem can simultaneously obtain three functions in the guide area: non-contact support, eccentric sensing, and differential pressure correction.

[0088] Combination Figure 3 As shown, the inclination angles of the outer conical surface 13 of the pusher 12 and the inner conical surface 16 of the wedge-shaped tightening ring 15 are both 15°.

[0089] The outer conical surface 13 of the outer circumference of the pusher 12 and the inner conical surface 16 of the inner hole of the wedge-shaped expansion ring 15 are both set with an inclination angle of 15°. This inclination angle is the angle of the generatrix of the conical surface relative to the assembly axis. The technical consideration of using 15° is that this angle can achieve a balance between the efficiency of converting axial thrust to radial clamping force, the wedge self-locking tendency, and the feasibility of part machining.

[0090] When the cone angle is too small, for example, less than 10°, the frictional self-locking tendency between the push head 12 and the wedge-shaped tightening ring 15 is enhanced, the force required for release and return increases, and after long-term operation, it is easy to cause response lag due to surface wear. When the cone angle is too large, for example, greater than 20°, the radial contraction generated by the same axial displacement increases, but the force amplification factor decreases, making it difficult to form sufficient clamping force under limited downforce conditions. The 15° cone angle, combined with the elastic compression of the wave spring 11, allows the push head 12 to drive the wedge-shaped tightening ring 15 to produce radial deformation sufficient to grip the valve stem within a relative displacement range of 0.5mm to 1.5mm.

[0091] In the actual structure, the surface roughness of the outer conical surface 13 and the inner conical surface 16 can be controlled between 0.8μm and 1.6μm, and the conical surface runout can be controlled within 0.02mm to reduce local jamming caused by uneven contact; the cone angle also needs to correspond to the mechanical conversion coefficient in the control algorithm, because there is a definite geometric relationship between the axial thrust, the compression of the wave spring 11 and the radial contraction of the wedge-shaped tightening ring 15;

[0092] Based on the pre-stored conversion model of thrust to clamping force of the cone angle, the controller 22 can maintain the downward pressure of the servo motor 4 and predict the clamping degree of the wedge-shaped tightening ring 15 when the interference resistance is detected to exceed the preset spline engagement threshold, thereby ensuring that the locking action matches the valve stem pressing state. Using the same 15° outer cone surface 13 and inner cone surface 16 can also reduce the accumulation of assembly errors and avoid one-sided contact and clamping eccentricity caused by the mismatch of cone angles.

[0093] Combination Figure 4 The pusher 12 is configured to move downward when subjected to the axial thrust of the main pressure bar 9 and to press the inner cone 16 with the outer cone 13.

[0094] The push head 12 is located below the bottom end of the main pressure rod 9 and is connected to the bottom end face of the main pressure rod 9 via a wave spring 11. During the normal flexible guiding stage, when the main pressure rod 9 is pressed down, the bottom surface of the push head 12 contacts the top end of the butterfly valve stem 25 and moves downward together. The wave spring 11 remains close to its free height or only undergoes slight compression. At this time, the outer conical surface 13 of the push head 12 and the inner conical surface 16 of the wedge-shaped expansion ring 15 only maintain slight contact or clearance fit, and the valve stem will not be subjected to significant radial clamping.

[0095] When the valve stem enters the spline engagement area or the blind hole bottom mating area, the axial interference resistance increases, the relative movement speed of the valve stem decreases, and the main pressure rod 9 continues to move downward under the drive of the servo motor 4. The wave spring 11 between the main pressure rod 9 and the push head 12 is compressed, forming an additional displacement of the main pressure rod 9 relative to the push head 12. This additional displacement forces the outer conical surface 13 of the push head 12 to enter the area of ​​the inner conical surface 16 of the wedge-shaped expansion ring 15 axially. Due to the conical surface mating relationship, the axial displacement is converted into a radial contraction displacement of the wedge-shaped expansion ring 15 towards the center. The inner hole of the wedge-shaped expansion ring 15 generates a circumferential clamping force on the outer circle of the valve stem.

[0096] The key to configuring the pusher 12 to perform this action is that it serves as both an axial force transmission component and a conical drive component. The pusher 12 can be integrally turned and ground, and the bottom contact surface can be machined into a flat or shallow arc surface to adapt to different valve stem end shapes. The axial length of the outer conical surface 13 can be 8mm to 15mm to ensure a continuous and progressive clamping stroke within the maximum working compression range of the wave spring 11.

[0097] The stiffness of the wave spring 11 can be set from 100 N / mm to 500 N / mm according to the valve stem diameter and the target clamping force, so that the pusher 12 only triggers a significant conical extrusion action after the actual interference resistance reaches the predetermined level, avoiding premature clamping of the valve stem during the guiding stage and loss of compliance; with this configuration, there is a clear mechanical correspondence between the axial movement of the pusher 12 and the radial contraction of the wedge-shaped tightening ring 15, enabling the equipment to complete the clamping state switching without adding an independent clamping actuator.

[0098] Example 2:

[0099] Combination Figure 5 As shown, the control method for the concentricity assembly equipment of butterfly valve stems based on mechanical positioning includes:

[0100] S1. Real-time acquisition of the operating current data of the servo motor 4, the air pressure data of the independent air chamber 18, and the real-time downward displacement of the main pressure rod 9, and calculation of the real-time overhang length of the butterfly valve stem 25.

[0101] S2. Calculate the current harmonic integral characterizing the high-frequency resistance torque disturbance based on the operating current data;

[0102] S3. Calculate the back pressure differential gradient based on the air pressure data of the relatively arranged independent air chambers 18;

[0103] S4. The axial interference resistance and actual position deviation angle are calculated by back-calculating the current harmonic integral, back pressure differential gradient and real-time overhang length.

[0104] S5. Control the pneumatic proportional valve 19 and vacuum generator 20 to operate according to the actual position deviation angle and axial interference resistance, so as to adjust the axial pressing state and radial position of the butterfly valve stem 25 in the guide sleeve 14.

[0105] The controller 22 is an industrial controller 22 with high-speed sampling and motion control functions; the controller 22 is configured with a resistance conversion module, an eccentricity conversion module, a state determination module, as well as a geometric calculation module, a mechanical deformation module and a superposition module for auxiliary calculation in its logical architecture;

[0106] In S1, the operating current data of the servo motor 4 and the air pressure data of the independent air chamber 18 are acquired in real time. The operating current data can be output by the current sensing unit inside the servo driver. The sampling frequency is preferably 1000Hz to 5000Hz to cover the spectrum analysis requirements of the 50 to 100Hz frequency band.

[0107] The air pressure data of the independent air chamber 18 can be collected by pressure sensors installed on each independent air pipe 21. The range can be -80kPa to +100kPa, and the sampling frequency is preferably 200Hz to 1000Hz. The controller 22 synchronizes the collected data in time and records the displacement of the main pressure rod 9 or the encoder position value of the servo motor 4 to establish the assembly stroke range corresponding to the data.

[0108] In S2, a fast Fourier transform is performed on the operating current data to extract the current harmonic amplitude in the 50 to 100 Hz frequency band. This frequency band is used to characterize the high-frequency resistance torque disturbance caused by micro-friction between the valve stem end and the deep blind hole mating surface, which is different from the motor fundamental frequency control quantity.

[0109] The controller 22 can perform a fast Fourier transform using a sliding time window with a length of 256 or 512 points, and sum or calculate the root mean square value of the amplitude at each frequency point in the 50 to 100 Hz frequency band to form a harmonic energy index; based on this, a time integration operation is performed on the index to obtain the current harmonic integral; the current harmonic integral is used to cumulatively characterize the contact friction intensity per unit time, and the integration time window can be taken from 50 ms to 300 ms;

[0110] In S3, the air pressure data of the relatively arranged independent air chambers 18 are extracted, and the rate of change over time is calculated respectively. If the four independent air chambers 18 are evenly distributed in a 90° circle, the upper and lower sides can be formed as the first pair, and the left and right sides can be formed as the second pair. The controller 22 calculates the rate of change of pressure in each air chamber in adjacent sampling periods through a differential algorithm, and then subtracts the rate of change of the same pair of relative air chambers to obtain the back pressure differential gradient. The back pressure differential gradient reflects the degree of asymmetry of local air film compression caused by valve stem eccentricity.

[0111] In S4, the axial interference resistance and actual position deviation angle are obtained by back calculation based on the current harmonic integral and the back pressure differential gradient. The axial interference resistance is used to represent the frictional resistance level between the bottom end of the valve stem and the valve body hole system, water blocking ring or spline engagement area. The actual position deviation angle is used to represent the degree of deviation of the valve stem center axis relative to the target assembly axis.

[0112] During the equipment calibration phase, the controller 22 stores the conversion relationships between current harmonics and resistance, and between back pressure gradient and eccentricity. It obtains two types of indirect measurement parameters through real-time calculation. Based on the electromechanical energy loss and fluid dynamic asymmetry in the assembly process mapped by the current harmonic integral and the back pressure differential gradient, the controller 22 can invert the axial interference resistance and actual position deviation angle that are difficult to be directly acquired by hardware sensors through these indirect parameters.

[0113] In S5, the pneumatic proportional valve 19 and vacuum generator 20 are controlled to operate according to the actual position deviation angle and axial interference resistance. When the position deviation angle is in the low value region, the controller 22 keeps the positive pressure of each independent air chamber 18 basically consistent, so that the valve stem feeds downward in the air-float boundary layer. When the position deviation angle increases but the axial interference resistance has not yet reached the spline engagement level, the controller 22 adjusts the pressure of the eccentric side and the back side air chamber to form a correction torque.

[0114] When the axial interference resistance exceeds the preset threshold, the controller 22 starts the vacuum generator 20 and maintains the servo motor 4 to continue pressing down, and completes the press-fit locking through negative pressure adsorption and mechanical wedge clamping; this method realizes the switchable control of conformal guidance and rigid press-fit during the assembly process by indirectly sensing the contact state of the microscopic deep blind hole inside the closed deep blind hole.

[0115] To avoid nonlinear logic confusion or uncertain judgments in the above processing, the controller 22 executes the following logic in a fixed order within one assembly cycle: reads the operating current of the servo motor 4, the pressure of the four independent air chambers 18, and the position of the main pressure rod 9 at the same moment; performs sliding time window spectrum analysis on the operating current and outputs the current harmonic amplitude set corresponding to the current time window; compresses the harmonic amplitude set in the time window into a single harmonic energy index, and performs integration and accumulation over several consecutive time windows to form a current harmonic integral that updates over time;

[0116] At the same time, the controller 22 calculates the rate of pressure change at adjacent sampling times for the four independent air chambers 18, and then compares the rate of change of the relative air chambers to obtain the back pressure differential gradient in two orthogonal directions; the current harmonic integral is sent to the resistance conversion module, and the back pressure differential gradient is sent to the eccentricity conversion module to obtain the axial interference resistance and radial eccentricity, respectively.

[0117] The actual position deviation angle is then obtained by combining the guide length and valve stem stiffness information. This position deviation angle, along with the axial interference resistance, is then sent to the state determination module to select one of the control actions: isobaric guidance, differential pressure correction, or vacuum wedging. The purpose of the state determination module is to determine the actuator action in the next stage based on the current assembly state characteristics.

[0118] Logically, this module consists of multiple parallel comparators, which compare the actual input pose angle and axial interference resistance with preset thresholds, and trigger the corresponding control branch based on the Boolean combination of the comparison results. This module represents the discrete state machine logic of the transition from flexible compliance to rigid pressing in the assembly process.

[0119] Specifically, the decision table logic configuration of the state determination module is as follows: First state isobaric guidance: the actual pose deviation angle is less than the preset critical deviation angle threshold and the axial interference resistance is less than or equal to the preset spline engagement threshold; Second state differential pressure correction: the actual pose deviation angle is greater than or equal to the preset critical deviation angle threshold and the axial interference resistance is less than or equal to the preset spline engagement threshold.

[0120] The third state vacuum wedging: regardless of the actual position and orientation angle, as long as the axial interference resistance is greater than the preset spline engagement threshold; through the above-mentioned clear three-state logic branches, it is ensured that the controller 22 can output a unique and definite control command in each sampling cycle, avoiding state deadlock or command conflict, and making it fully software programmable;

[0121] The logical function of the current harmonic integral in this invention is not simply to reflect the size of the motor load, but to distinguish whether the valve stem is in a smooth sliding, slight rubbing, or engaged state; the back pressure differential gradient is not a normal pipeline pressure difference, but to reflect whether the valve stem is eccentric and the direction of eccentricity within the annular gas film formed by the microporous ceramic layer 17; the two correspond to the axial contact state and the radial pose state, respectively. The controller 22 only enters the back calculation process of S4 after obtaining these two quantities simultaneously, thereby avoiding incorrect control branch switching caused by a single transient signal.

[0122] The axial interference resistance output by S4 mainly flows to the spline engagement threshold determination module, while the actual position deviation angle mainly flows to the critical deviation angle threshold determination module. Together, they determine the control branch executed by S5. If the position deviation angle reaches the preset critical deviation angle threshold and the interference resistance is lower than the preset spline engagement threshold, the differential pressure correction branch is entered first. If the interference resistance continues to increase, the vacuum wedging branch is entered first. This ensures that the purpose and direction of each calculation result remain clear.

[0123] The steps in S4 specifically include: multiplying the back pressure differential gradient by a conversion factor to obtain the radial eccentricity; multiplying the current harmonic integral by a mechanical conversion factor to obtain the axial interference drag; and combining the radial eccentricity and the axial interference drag to calculate the actual pose angle using trigonometric functions.

[0124] The S4 back-calculation process uses a pre-calibrated conversion model. The purpose of this conversion model is to accurately estimate the radial eccentricity and axial interference resistance of the valve stem in the absence of physical sensors to directly detect the physical state inside the deep hole. Logically, this model contains two parallel sub-models: the aerodynamic eccentricity inversion sub-model receives the back pressure differential gradient as input to calculate the radial eccentricity; the electromagnetic resistance inversion sub-model receives the current harmonic integral as input to calculate the axial interference resistance.

[0125] The model as a whole characterizes the microscale relationship in fluid dynamics and the high-frequency torque transmission relationship in electromechanical transmission systems. For the conversion from back pressure differential gradient to radial eccentricity, during the equipment commissioning stage, a standard valve stem can be placed in the microporous ceramic layer 17, and a radial offset of 0.01 mm to 0.3 mm can be applied in a known direction through a micro-displacement platform. The pressure change rate difference relative to the air chamber is recorded respectively, and a correspondence table or linear piecewise function between back pressure differential gradient and radial eccentricity is established.

[0126] During the conversion, the controller 22 multiplies the real-time back pressure differential gradient by a conversion factor, or interpolates by looking up a table in the nonlinear region to obtain the radial eccentricity. This conversion factor is related to the porosity of the microporous ceramic layer 17, the gas supply pressure, the gas chamber volume, and the valve stem diameter. Therefore, it is solidified after the equipment assembly and gas supply conditions are determined. The conversion from current harmonic integration to axial interference resistance can be established based on the torque constant of the servo motor 4 and the transmission efficiency of the ball screw 6.

[0127] Under constant downward speed conditions, the high-frequency current fluctuation of servo motor 4 corresponds to the change in output resistance torque. Controller 22 multiplies the current harmonic integral by the mechanical conversion coefficient to obtain the axial interference resistance. The mechanical conversion coefficient can be determined by comprehensively considering the motor torque constant, ball screw 6 lead, transmission efficiency and sampling integration window length, and corrected by standard resistance load test.

[0128] When calculating the actual position deviation angle by combining radial eccentricity and axial interference resistance, the valve stem can be regarded as a small-angle skewed component within the effective guide length of the guide sleeve 14. If the guide length is denoted as L and the radial eccentricity as e, the position deviation angle can be calculated as the angle corresponding to the ratio of e to L according to the arctangent relationship. When it is necessary to take into account the amplifying effect of axial interference resistance on the bending tendency of the valve stem, the axial interference resistance can be introduced into the correction term to form a corrected angle model related to the bending stiffness of the valve stem. The purpose of this corrected angle model is to accurately obtain the actual skew angle of the slender valve stem under pressure.

[0129] Logically, the model receives the radial eccentricity and axial interference resistance calculated above as input. It first outputs the basic geometric deflection angle through the geometric calculation module, then outputs the resistance correction deflection angle through the mechanical deformation module, and finally superimposes the two to output the actual pose deflection angle. The model represents the physical causal relationship between the superposition of rigid body geometric deflection and elastic flexural deformation of a slender rod under eccentric compression conditions.

[0130] In practical control, the pose deviation angle can be expressed as the basic geometric deviation angle plus the resistance correction angle. The basic geometric deviation angle is determined by the radial eccentricity and the guide length, while the resistance correction angle is determined by the axial interference resistance and the valve stem bending stiffness. In terms of algorithm implementation, the specific data flow and calculation rules for the correction angle model are as follows: The geometric calculation module receives the radial eccentricity e and the guide length L, and calculates the basic geometric deviation angle according to the following rules:

[0131]

[0132] Output basic geometric deflection angle ;in, It is the basic geometric deflection angle, in rad. This is the radial eccentricity, in mm; The effective guiding length of the guide sleeve, in mm, is a preset mechanical structural constant; simultaneously, it represents the real-time overhang length of the butterfly valve stem. The controller 22 calculates the axial interference resistance based on the real-time downward displacement of the servo motor 4 and the initial position of the valve stem, and inputs this value into the mechanical deformation module. and pre-configured valve stem bending stiffness Combined with valve stem overhang length and the aforementioned radial eccentricity The calculation rules for cantilever beam deflection are based on the theory of materials mechanics:

[0133]

[0134] in, The deflection angle is the drag correction angle, in rad; F is the axial interference drag, in N; e is the radial eccentricity, which needs to be converted to standard SI units m in the formula calculation to maintain dimensional consistency. This is the real-time overhang length of the butterfly valve stem, which also needs to be converted to standard international units (m) in the formula calculation here; Overall, the bending stiffness of the valve stem is characterized by its resistance to bending, expressed in units of... The overlay module receives the basic geometric deflection angle. With resistance correction angle The results are then summed and superimposed to output the actual pose deflection angle. This rule characterizes the amplification effect of the additional bending moment caused by eccentric compression on the deflection angle. Characterizes the additional bending moment caused by eccentric compression;

[0135] Through the above highly structured decomposition and theoretical formula support, the pose estimation process of slender rods under eccentric compression conditions has clear software programmability and mechanical theoretical basis, eliminating the difficulty of directly collecting attributes through hardware sensors in the internal logic of the inverse calculation process.

[0136] The technical significance of adopting this inverse calculation method is that, because the skew state inside the deep blind hole, which cannot be directly measured, is decomposed into two perceptible parameters, radial eccentricity and axial resistance, and the actual position and orientation angle is recovered through the geometric and mechanical coupling relationship, the controller 22 can distinguish between two different states: simple eccentricity guidance deficiency and enhanced contact interference, thereby improving the pertinence of the control action.

[0137] The steps of S5 specifically include: S501, when the actual position deviation angle is less than the preset critical deviation angle threshold, the pneumatic proportional valve 19 is controlled to introduce a positive pressure airflow of equal pressure into the independent air chamber 18 so as to form an air-floating boundary layer on the surface of the butterfly valve stem 25 through the microporous ceramic layer 17.

[0138] S502. When the actual position deviation angle is greater than or equal to the preset critical deviation angle threshold and the axial interference resistance is less than or equal to the preset spline engagement threshold, the downward pressing speed of the servo motor 4 is maintained, and the pneumatic proportional valve 19 is controlled to increase the intake pressure in the independent air chamber 18 on the eccentric side and decrease the intake pressure in the independent air chamber 18 on the opposite side to form a pneumatic micro-correction torque.

[0139] The control of S5 includes two positive pressure guiding states; in S501, when the actual position deviation angle is less than the preset critical deviation angle threshold, the controller 22 determines that the valve stem is in the range where the assembly can be maintained by the air film self-centering effect; the preset critical deviation angle threshold can be determined according to the valve stem length-to-diameter ratio, the length of the guide sleeve 14 and the allowable contact risk, and is preferably set to 0.1° to 0.5°; the controller 22 outputs the same proportional valve control signal to each independent air chamber 18, so that the pneumatic proportional valve 19 introduces positive pressure airflow of equal pressure to each independent air chamber 18, and the air supply pressure can be 0.05MPa to 0.3MPa;

[0140] After the gas passes through the microporous ceramic layer 17, a continuous annular air-floating boundary layer is formed on the surface of the valve stem, which forms a stable gas film between the outer wall of the valve stem and the inner wall of the microporous ceramic layer 17. Solid contact is effectively isolated, and the frictional force during the axial feeding process is significantly reduced. Since the pressure in the four independent gas chambers 18 is equal, the circumferential stiffness distribution of the gas film is basically consistent. When the valve stem is slightly eccentric, under the action of the restoring fluid support force generated by the fluid dynamics, the valve stem tends to automatically return to the center position.

[0141] In S502, when the actual position deviation angle is greater than or equal to the preset critical deviation angle threshold and the axial interference resistance is less than or equal to the preset spline engagement threshold, the controller 22 determines that the valve stem has deviated beyond the preset self-centering adjustment range, but the bottom end has not yet entered the engagement stage that requires high rigidity pressing. At this time, the controller 22 maintains the downward pressing speed of the servo motor 4 at a constant speed, preferably 2 mm / s to 20 mm / s, to avoid speed fluctuations masking the contact signal. At the same time, the eccentric direction is determined according to the back pressure differential gradient. The intake pressure is increased in the independent air chamber 18 corresponding to the eccentric side, and the intake pressure is decreased in the independent air chamber 18 corresponding to the opposite side. The pressure difference can be 0.01 MPa to 0.1 MPa.

[0142] The differential pressure acts on the outer surface of the valve stem through the microporous ceramic layer 17 to form a pneumatic micro-correction torque, thereby driving the valve stem to generate a slight attitude return around its restricted contact point; for a pair of independent air chambers 18 perpendicular to the eccentric direction, the original pressure can be maintained or a small compensation adjustment can be made to maintain the stability of the air film.

[0143] The preset spline engagement threshold can be obtained through unloaded insertion, water-blocking ring crossing, and spline entry experiments, and is preferably set in the range of 2 to 5 times the unloaded guiding resistance. By adopting this two-stage positive pressure control method, continuous correction can be completed by fluid support and differential pressure torque before the valve stem enters the high-resistance press-fitting area, reducing the probability that the valve stem enters the next stage of mating area in an oblique posture.

[0144] The physical meaning of the preset critical deflection angle threshold in this invention is: the maximum allowable attitude deflection boundary at which the valve stem can still return to center on its own by relying on the restoring force of the air film; when the actual attitude deflection angle is lower than this threshold, the controller 22 considers that the valve stem and the guide sleeve 14 are still in a low-risk non-contact guiding state, and the equal pressure air supply can continue to be used; when the actual attitude deflection angle reaches or exceeds this threshold, the controller 22 considers that the simple equal pressure air film is not enough to suppress the deflection expansion, and therefore switches to differential pressure correction.

[0145] The threshold can be determined using the following calibration logic: First, under the conditions of a standard valve stem and a standard guide sleeve 14, repeatedly perform the cartridge test with different initial deflection angles, and record whether the valve stem can return to center without rubbing when only equal pressure air supply is applied; then, take the maximum deflection angle that can stably return without rubbing as the initial calibration value; combine the valve stem material, length and actual allowable scratch risk to leave a safety margin, and obtain the preset critical deflection angle threshold for batch assembly;

[0146] Therefore, the threshold has both a clear physical meaning and a repeatable experimental basis. For example, in a set of comparative experiments using 45# steel as the valve stem material and an aspect ratio of 20, when the isobaric gas supply was set to 0.1MPa, it was recorded that when the initial deflection angle was 0.2°, the valve stem could automatically return to center within 0.5s without surface scratches due to the gas film restoring force. When the initial deflection angle increased to 0.4°, the recovery time increased to 1.2s and local micro-scratches appeared. When the initial deflection angle reached 0.5°, the valve stem could not return to center and obvious jamming occurred.

[0147] Based on this set of clear experimental data, the preset critical deflection angle threshold was set to 0.3°, thus providing sufficient experimental data support for the threshold setting and proving that this parameter can significantly define the boundary between safety orientation and risk deflection.

[0148] The physical meaning of the preset spline engagement threshold is: the boundary resistance at which the bottom of the valve stem has transitioned from a smooth guiding state to a state of rigid contact and abrupt mechanical interference; this threshold is not a random value corresponding to the instantaneous peak current, but a logical threshold used to determine whether it is necessary to end the positive pressure flexible guidance and prepare to enter the high rigidity press-fitting stage.

[0149] The determination process may include: conducting a no-load guiding test and recording the reference resistance range of the valve stem in the pure guiding zone; conducting a water-blocking ring crossing test and recording the medium resistance range brought about by the elastic seal; and then conducting a spline entry test and recording the resistance range when the valve stem begins to engage significantly.

[0150] The resistance value that is higher than the guide zone and the seal crossing zone and can stably characterize the spline entry point is selected as the preset spline engagement threshold. The purpose of the controller 22 in using this threshold in S502 is to ensure that differential pressure correction only occurs in the stage where it can still be flexibly corrected, and will not continue to rely on low stiffness air film support after entering the high resistance engagement zone.

[0151] The steps of S5 also include: S503, when the axial interference resistance is greater than the preset spline engagement threshold, control the vacuum generator 20 to start and extract the air in the independent air chamber 18 to eliminate the air floating boundary layer; control the servo motor 4 to continue to press down to compress the wave spring 11, the main pressure rod 9 pushes the push head 12 to move downward, the outer cone surface 13 squeezes the inner cone surface 16 to force the wedge-shaped expansion ring 15 to contract towards the center and radially rigidly lock the butterfly valve stem 25;

[0152] S503 is used for high-rigidity press-fit control after the valve stem enters the spline engagement area or final press-fit area of ​​the butterfly plate; when the axial interference resistance is greater than the preset spline engagement threshold, the controller 22 determines that the bottom end of the valve stem has encountered an assembly resistance greater than the threshold setting, and simply relying on air float guidance is not enough to ensure continued press-in; at this time, the controller 22 outputs a start signal to the vacuum generator 20 and switches the corresponding air path, so that the vacuum generator 20 extracts air from each independent air chamber 18, and the air chamber pressure drops rapidly from positive pressure to negative pressure or close to zero pressure, the annular air film inside and outside the microporous ceramic layer 17 is weakened or eliminated, and the outer surface of the valve stem is no longer in a low-friction floating support state;

[0153] The negative pressure generated by the vacuum generator 20 can also create an adhesion constraint between the outer wall of the valve stem and the microporous ceramic layer 17, which helps to reduce the lateral movement of the valve stem during the spline entry stage. At the same time, the controller 22 maintains the servo motor 4 to continue pressing down at the set speed. The main pressure rod 9 moves downward while the valve stem lags behind due to the bottom interference resistance, causing the wave spring 11 to be compressed. After the compression of the wave spring 11 reaches the predetermined value, the main pressure rod 9 generates additional displacement relative to the push head 12. The push head 12 is pushed downward, and its outer conical surface 13 enters the area of ​​the inner conical surface 16 of the wedge-shaped expansion ring 15 and applies extrusion force.

[0154] Due to the conical surface fit, the wedge-shaped tightening ring 15 contracts radially towards the center, and the inner hole forms a circumferential clamping around the butterfly valve stem 25. The clamping force is related to the downward pressure of the servo motor 4, the compression of the wave spring 11, the conical angle, and the conical friction coefficient. The controller 22 can estimate the clamping degree of the wedge-shaped tightening ring 15 based on the displacement increment and current change of the servo motor 4. After the valve stem is radially rigidly locked, the axial thrust of the main pressure rod 9 is stably transmitted to the valve stem through the push head 12 and the wedge-shaped tightening ring 15, so that the valve stem has sufficient axial stiffness to pass through the spline engagement area and complete the seating.

[0155] In this step, the vacuum generator 20 starts and the mechanical wedging action overlap in time, which can promptly switch the radial compliance required in the guiding stage to the axial bearing capacity required in the pressing stage, and prevent the valve stem from continuing to be subjected to force in a floating state in the high resistance area and causing bending instability.

[0156] In practical applications, the vacuum switching response time can be controlled from 50ms to 200ms, the working compression of the wave spring 11 can be controlled from 0.3mm to 1.2mm, and the wedge-shaped tightening ring 15 can be made of spring steel or high-strength stainless steel with a shrinkage slit along the circumference to ensure that it can still provide a stable radial shrinkage during multiple working cycles. Through this control step, the equipment can complete the integrated pressing process of guiding, correcting and locking without adding an external gripper mechanism.

[0157] To improve the stability of S503 trigger judgment, the controller 22 may not immediately switch when a single sampling point exceeds the preset spline engagement threshold. Instead, it may determine that the axial interference resistance is continuously greater than the threshold for multiple consecutive sampling cycles, or that the current harmonic integral and the axial interference resistance continuously increase within a short time window before performing vacuum switching.

[0158] The technical consideration behind this logic is that transient resistance spikes may occur when the valve stem passes through local burrs, the lip of the seal, or short-term friction. If the switching is based solely on a single peak value, the positive pressure correction stage may end prematurely. On the other hand, continuous over-threshold determination can better characterize the actual spline entry or final pressure interference state, thereby making the start-up timing of the vacuum generator 20 more stable.

[0159] The internal execution sequence of S503 can be clearly defined as follows: First, the state determination module confirms that the axial interference resistance has entered the high resistance zone; then, it sends a pumping command to the vacuum generator 20 and the gas path switching unit, so that the positive pressure supply of each independent gas chamber 18 is reduced and switched to a negative pressure or near-zero pressure state; the servo motor 4 continues to press down, so that the main pressure rod 9 generates an additional displacement relative to the obstructed valve rod and compresses the wave spring 11; the controlled displacement released by the wave spring 11 drives the push head 12 to move downward, and the outer conical surface 13 of the push head 12 begins to squeeze the inner conical surface 16 of the wedge-shaped expansion ring 15;

[0160] After the wedge-shaped tightening ring 15 contracts and clamps the valve stem, the subsequent downward pressure is transmitted to the valve stem axis through a high-rigidity path. The function of vacuum switching is to eliminate or weaken the air flotation boundary layer and limit lateral movement, while the function of mechanical wedging is to establish a stable axial bearing passage. The two work together to complete the press-fitting in the high-resistance stage.

[0161] This application has been described through the above embodiments; however, it should be understood that the above embodiments are for illustrative purposes only and are not intended to limit this application to the described embodiments. Those skilled in the art will understand that many more variations and modifications can be made based on the teachings of this application, and all such variations and modifications fall within the scope of protection claimed in this application.

Claims

1. A butterfly valve stem concentricity assembly device based on mechanical positioning, characterized in that, include: The assembly frame (1) has a top horizontal surface (2) and a bottom plate (3). A servo motor (4) is fixed to the top horizontal surface (2) and has an output shaft (5). A ball screw (6) is connected to the output shaft (5); The lead screw nut (7) is threaded with the ball screw (6) and has a flange face (8). The main pressure rod (9) is fixed to the flange face (8) and has a hollow cylindrical structure (10) inside to accommodate the butterfly valve stem (25). A wave spring (11) is connected to the bottom end face of the main pressure rod (9); The push head (12) is connected to the wave spring (11), and its outer peripheral surface is provided with an outer conical surface (13). Its bottom surface abuts against the top of the butterfly valve stem (25). The guide sleeve (14) is fixed to the lower base plate (3) and is coaxial with the main pressure rod (9); A wedge-shaped tightening ring (15) is placed in the inner hole at the top of the guide sleeve (14). The inner hole is provided with an inner cone surface (16) that mates with the outer cone surface (13), and its outer circle is in clearance fit with the inner hole of the guide sleeve (14). A microporous ceramic layer (17) is bonded to the lower inner wall of the guide sleeve (14), with an independent air chamber (18) between them. It includes a pneumatic proportional valve (19) and a vacuum generator (20), which are connected to the independent air chamber (18) via independent air pipes (21); The controller (22) connects to and controls the servo motor (4), the pneumatic proportional valve (19), and the vacuum generator (20).

2. The butterfly valve stem concentricity assembly equipment based on mechanical positioning according to claim 1, characterized in that, The output shaft (5) of the servo motor (4) is connected to the top of the ball screw (6) through a plum blossom-shaped flexible coupling (23); the ball screw (6) is supported in the inner cavity of the assembly frame (1) by an angular contact ball bearing (24).

3. The butterfly valve stem concentricity assembly equipment based on mechanical positioning according to claim 2, characterized in that, The outer diameter of the main pressure rod (9) is 50 mm, and the inner diameter of the main pressure rod (9) is 30 mm.

4. The butterfly valve stem concentricity assembly equipment based on mechanical positioning according to claim 1, characterized in that, The inner diameter of the microporous ceramic layer (17) is larger than the outer diameter of the butterfly valve stem (25); the independent air chambers (18) are evenly distributed along the circumferential direction.

5. The butterfly valve stem concentricity assembly equipment based on mechanical positioning according to claim 1, characterized in that, The inclination angles of the outer conical surface (13) of the pusher (12) and the inner conical surface (16) of the wedge-shaped tightening ring (15) are both 15°.

6. The butterfly valve stem concentricity assembly equipment based on mechanical positioning according to claim 1, characterized in that, The pusher (12) is configured to move downward when subjected to the axial thrust of the main pressure bar (9) and to press the inner cone (16) with the outer cone (13).

7. A control method, applied to the butterfly valve stem concentricity assembly equipment based on mechanical positioning as described in claim 1, characterized in that, include: S1. Real-time acquisition of the operating current data of the servo motor (4), the air pressure data of the independent air chamber (18) and the real-time downward displacement of the main pressure rod (9), and calculation of the real-time overhang length of the butterfly valve stem (25); S2. Calculate the current harmonic integral characterizing the high-frequency resistance torque disturbance based on the operating current data; S3. Calculate the back pressure differential gradient based on the air pressure data of the relatively arranged independent air chambers (18); S4. The axial interference resistance and actual position deviation angle are calculated back based on the current harmonic integral, the back pressure differential gradient and the real-time overhang length. S5. Control the pneumatic proportional valve (19) and the vacuum generator (20) according to the actual position deviation angle and the axial interference resistance to adjust the axial pressing state and radial position of the butterfly valve stem (25) in the guide sleeve (14).

8. The control method according to claim 7, characterized in that, The steps in S4 specifically include: multiplying the back pressure differential gradient by a conversion factor to obtain the radial eccentricity; multiplying the current harmonic integral by a mechanical conversion factor to obtain the axial interference resistance; and calculating the actual pose angle by combining the radial eccentricity and the axial interference resistance using trigonometric functions.

9. The control method according to claim 7, characterized in that, The steps of S5 specifically include: S501, when the actual position deviation angle is less than the preset critical deviation angle threshold, the pneumatic proportional valve (19) is controlled to introduce a positive pressure airflow of equal pressure into the independent air chamber (18) so as to form an air-floating boundary layer on the surface of the butterfly valve stem (25) through the microporous ceramic layer (17). S502. When the actual position deviation angle is greater than or equal to the preset critical deviation angle threshold and the axial interference resistance is less than or equal to the preset spline engagement threshold, the downward speed of the servo motor (4) is maintained, and the pneumatic proportional valve (19) is controlled to increase the intake pressure in the independent air chamber (18) on the eccentric side and decrease the intake pressure in the independent air chamber (18) on the opposite side to form a pneumatic micro-correction torque.

10. The control method according to claim 9, characterized in that, The steps of S5 further include: S503, when the axial interference resistance is greater than the preset spline engagement threshold, controlling the vacuum generator (20) to start and extract the air in the independent air chamber (18) to eliminate the air floating boundary layer; controlling the servo motor (4) to continue pressing down to compress the wave spring (11), the main pressure rod (9) pushes the push head (12) to move downward, the outer cone surface (13) squeezes the inner cone surface (16) to force the wedge-shaped expansion ring (15) to contract towards the center and radially clamp and lock the butterfly valve stem (25).

Images