Positioning tool for machining of shaft workpieces

Abstract

The application discloses a positioning tool for shaft workpiece machining and relates to the technical field of positioning tools.The positioning tool comprises a positioning table, a chuck, an intermediate supporting unit and a tailstock, the intermediate supporting unit comprises a driving cylinder, an adjusting mechanism and a clamping unit, the clamping unit is provided with a radial plate and a flexible body provided with rolling bodies, the driving unit drives the driving cylinder to move axially and rotate, during machining, the intermediate supporting unit moves synchronously with the cutter feeding, the rolling bodies form follow-up support in the adjacent area of the cutting point, the supporting span is shortened to enhance the cutting rigidity, the deformation and chatter are inhibited, the rolling bodies rotate with the workpiece to realize rolling contact, the machined surface is prevented from being scratched, elastic members and fluid are integrated in the flexible body, force measuring elements are matched to realize closed-loop control of clamping force, the supporting rigidity can be adjusted by changing the state of the fluid, and the rough machining and fine machining requirements are considered.

Description

Technical Field

[0001] This invention relates to the field of positioning tooling technology, specifically a positioning tooling for machining shaft-type workpieces. Background Technology

[0002] When turning slender shaft-like workpieces, a chuck and tailstock center are usually used to clamp the two ends of the workpiece. However, the overhanging area in the middle of the workpiece lacks effective support and is prone to bending deformation and cutting chatter under radial cutting force, which directly affects dimensional accuracy and surface quality.

[0003] In production, a follower rest or center rest is often added for auxiliary support. However, existing follower rests are mostly fixed at a certain position on the machine bed, or can only be manually adjusted to the vicinity of the tool starting point. The distance between the support point and the cutting point will increase continuously with the tool feed, resulting in an increase in the support span. This significantly reduces the effect of improving the rigidity of the cutting part and suppressing vibration. Summary of the Invention

[0004] The purpose of this invention is to provide a positioning fixture for machining shaft-type workpieces, so as to solve the problem that the support point cannot follow the tool during the feed process in the prior art, resulting in a decrease in vibration suppression effect.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a positioning fixture for machining shaft-type workpieces, comprising a positioning table, a chuck, an intermediate support unit and a tailstock, wherein the chuck and the tailstock are respectively installed on both sides of the positioning table, the chuck is fixedly installed on one side of the positioning table, and the tailstock is axially movable on the other side of the positioning table; The intermediate support unit includes a drive unit, a detection unit, a drive cylinder, an adjustment mechanism, and multiple clamping units. The drive unit is mounted on the positioning table and is used to drive the drive cylinder to move along the workpiece axis and rotate around the axis by a set angle. The output end of the drive unit is connected to the drive cylinder. The detection unit is mounted on the drive cylinder and is used to detect the radial runout and vibration data of the workpiece and transmit them to the control system. The adjustment mechanism is mounted on the drive cylinder. Multiple clamping units are arranged circumferentially along the drive cylinder. Each clamping unit includes a radial plate and multiple clamping members. The radial plate is located inside the drive cylinder and is drively connected to the adjustment mechanism. The clamping member includes a flexible body and a plurality of rolling elements. The flexible body is mounted on a radial plate, and the plurality of rolling elements are all mounted on the flexible body.

[0006] The rolling element is a ball, and the flexible body is provided with a ball groove, in which the ball rolls.

[0007] Clamping cylinders are installed at both ends of the drive cylinder. Elastic plates are installed on the telescopic rods of the clamping cylinders. When the clamping cylinder drives the elastic plates to work, the workpiece can be clamped and positioned. The clamping cylinder is electrically connected to the control system. The elastic plates can prevent the workpiece from being pinched and damaged.

[0008] The flexible body includes a fixed cylinder and a sliding cylinder; The fixed cylinder is mounted on the radial plate, and a sliding cavity is provided inside the fixed cylinder. The sliding cylinder is slidably connected to the sliding cavity. An elastic element is connected between the fixed cylinder and the sliding cylinder; The rolling element is rotatably mounted on the sliding cylinder.

[0009] The fixed cylinder and the sliding cylinder are slidably connected by a guide key and a guide groove. The guide key is set on the sliding cylinder, and the guide groove is set on the fixed cylinder. The guide key slides in the guide groove and limits the maximum extension stroke of the sliding cylinder.

[0010] The elastic element is a spring.

[0011] The sliding cavity is filled with fluid, and a force measuring element is installed on the fixed cylinder at the position corresponding to the fluid. The force measuring element is electrically connected to the control system.

[0012] The force measuring element is a pressure sensor, which is electrically connected to the control system.

[0013] A sealing plate or sealing ring is provided between the guide key and the guide groove to achieve a sliding seal between the guide key and the guide groove, so as to facilitate the filling of fluid.

[0014] The fluid is a thermally expanding medium, and a heating element and a temperature measuring element are installed inside the fixed cylinder. The heating element and the temperature measuring element are electrically connected to the control system.

[0015] Heating elements include heating wires and heating plates, while temperature sensing elements are temperature sensors.

[0016] Both the fixed cylinder and the sliding cylinder are made of heat-insulating material.

[0017] The fluid is a magnetorheological fluid, and an excitation assembly is installed inside the fixed cylinder. The excitation assembly is electrically connected to the control system.

[0018] The fixed cylinder is a cylinder structure, and the sliding cylinder is a piston rod structure. The sliding cylinder divides the fixed cylinder into two independent chambers: a rod chamber and a rodless chamber. The piston has at least one damping through hole, which connects the rod chamber and the rodless chamber. The magnetorheological fluid can flow between the rod chamber and the rodless chamber through the damping through hole.

[0019] The elastic element is disposed within the rodless cavity.

[0020] The excitation component is an excitation coil, which is located inside the fixed cylinder and is used to apply a controllable magnetic field to the magnetorheological fluid.

[0021] The adjustment mechanism includes a movable ring and a linear push rod. Two movable rings are provided, and the two movable rings are slidably mounted on the drive cylinder. The two movable rings are respectively connected to the two ends of the linear push rod. The drive cylinder has through slots at the positions of the two moving rings, and each moving ring is rotatably connected to the radial plate via a connecting rod.

[0022] The linear push rod is a two-way push rod with two telescopic parts. The two telescopic parts of the linear push rod are respectively connected to two moving rings, and the cylinder of the linear push rod is mounted on the drive cylinder.

[0023] The drive unit includes a linear motion mechanism and a rotary mechanism. The linear motion mechanism is mounted on a positioning platform, and its output end is connected to a moving platform. The moving platform moves linearly on the positioning platform. The rotary mechanism is mounted on the moving platform, and its output end is connected to a drive cylinder.

[0024] The radial plate has a C-shaped longitudinal section, and multiple radial plates form a ring structure.

[0025] The drive cylinder has baffles at both ends, and a connecting groove in the middle of each baffle. Several telescopic cleaning plates, each equipped with a brush, are located outside the connecting groove. The workpiece passes through the connecting grooves at both ends. The cleaning plates extend and retract via telescopic cylinders mounted on the baffles.

[0026] As the drive cylinder moves, the cleaning plate extends a brush to clean the surface of the workpiece, preventing debris from entering the drive cylinder.

[0027] When loading and unloading workpieces, the telescopic cylinder drives the cleaning plate and brush to retract, making it easier to load and unload workpieces.

[0028] During the workpiece processing, the telescopic cylinder drives the cleaning plate and brush to extend to block the connecting groove and prevent debris from entering.

[0029] Compared with the prior art, the beneficial effects of the present invention are: 1. The follow-up support suppresses deformation and chatter without damaging the surface. The drive unit synchronously moves the drive cylinder according to the axial feed position of the tool, ensuring that the rolling elements on the clamping unit always press against the outer circle of the workpiece in the vicinity of the cutting point. This significantly shortens the actual support span, effectively enhances the rigidity of the cutting area, and suppresses bending deformation and high-frequency chatter caused by cutting forces. The rolling elements form rolling contact with the workpiece rotation, eliminating sliding and scraping between the support element and the machined surface, protecting the surface integrity. This solves the problems of existing tool holders that cannot follow the tool in real time, have large support spans, poor vibration reduction effects, and are prone to scratching the workpiece surface.

[0030] 2. Closed-loop clamping force control prevents workpiece damage. The flexible body consists of a fixed cylinder, a sliding cylinder, an elastic element, and internal fluid, and is equipped with a force-measuring element. When the adjustment mechanism feeds, the sliding cylinder is compressed and retracts, squeezing the fluid. The force-measuring element collects the fluid pressure in real time and feeds it back to the control system, thereby adjusting the feed amount of the adjustment mechanism, forming a closed-loop clamping force control. This method can maintain the clamping force within a set range, preventing insufficient clamping force from causing the workpiece to move during cutting, and also avoiding excessive clamping force from causing indentations or plastic deformation on the workpiece surface. It is particularly suitable for protecting thin-walled shafts. This solves the problem of not being able to monitor and adjust the clamping force in real time, which can easily damage the workpiece due to uncontrolled force.

[0031] 3. Automatic circumferential positioning of the workpiece during unloading. The drive unit includes a rotating mechanism. After the workpiece is disengaged from the chuck and tailstock at both ends, the rotating mechanism drives the workpiece to rotate by a preset angle via the drive cylinder, ensuring that features such as keyways and flat sections are accurately aligned with the alignment structure at the unloading station. This feature eliminates the need for manual flipping and adjustment, shortens unloading auxiliary time, reduces the risk of collisions, and improves the overall processing cycle time. It solves the problems of requiring manual circumferential alignment after processing, low efficiency, and easy damage to the workpiece.

[0032] 4. Adjustable support stiffness, accommodating both roughing and finishing. The fluid used is a thermally expanding medium or magnetorheological fluid, and the fluid pressure or shear yield strength is changed through heating elements or excitation components. During roughing, the stiffness is increased, making the flexible body approach a rigid support to resist large cutting forces and ensure dimensional stability. During finishing, the stiffness is reduced, and damping is used to absorb cutting vibrations and reduce surface roughness. This solves the problem that fixed stiffness supports cannot simultaneously meet the high rigidity requirements of roughing and the vibration absorption requirements of finishing. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the rotating mechanism in this invention; Figure 3 This is a schematic diagram of the linear motion mechanism in this invention; Figure 4 This is a schematic diagram of the linear push rod in this invention; Figure 5 This is a schematic diagram of the moving ring structure in this invention; Figure 6 This is a schematic diagram of the connecting rod in this invention; Figure 7 This is a schematic diagram of the structure of the rolling element in this invention.

[0034] In the diagram: 1. Positioning stage; 2. Chuck; 3. Intermediate support unit; 31. Drive cylinder; 32. Adjustment mechanism; 321. Moving ring; 322. Linear push rod; 323. Connecting rod; 33. Clamping unit; 331. Radial plate; 332. Clamping component; 3321. Flexible body; 33211. Fixed cylinder; 33212. Sliding cylinder; 3322. Rolling element; 34. Linear movement mechanism; 341. Moving stage; 35. Rotation mechanism; 4. Tailstock. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] like Figures 1-5 As shown in the first embodiment of the present invention, a technical solution for a positioning fixture for machining shaft-type workpieces is provided.

[0037] The specific content of Embodiment 1 is as follows: A positioning fixture for machining shaft-type workpieces includes a positioning table 1, a chuck 2, an intermediate support unit 3, and a tailstock 4. The chuck 2 and tailstock 4 are respectively installed on both sides of the positioning table 1. The operation of the chuck 2 and tailstock 4 is controlled by a control system. The chuck 2 can automatically clamp and release the workpiece, and the tailstock 4 can move linearly and contact the workpiece to support it. The chuck 2 is fixedly installed on one side of the positioning table 1, and the tailstock 4 is axially movable on the other side of the positioning table 1. The intermediate support unit 3 includes a drive unit, a detection unit, a drive cylinder 31, an adjustment mechanism 32, and multiple clamping units 33. The drive unit is installed on the positioning table 1 and is used to drive the drive cylinder 31 to move axially along the workpiece and rotate around the axis. The output end of the drive unit is connected to the drive cylinder 31 at a set angle. The detection unit is mounted on the drive cylinder 31 and includes a displacement sensor or a vibration sensor. The detection unit is used to detect the radial runout and vibration data of the workpiece and transmit them to the control system. The adjustment mechanism 32 is mounted on the drive cylinder 31. A plurality of clamping units 33 are arranged circumferentially along the drive cylinder 31. Each clamping unit 33 includes a radial plate 331 and a plurality of clamping elements 332. The radial plate 331 is located inside the drive cylinder 31 and is drively connected to the adjustment mechanism 32. Each clamping element 332 includes a flexible body 3321 and a plurality of rolling elements 3322. The flexible body 3321 is mounted on the radial plate 331, and the plurality of rolling elements 3322 are all mounted on the flexible body 3321.

[0038] The adjustment mechanism 32 consists of multiple hydraulic cylinders, the output ends of which are connected to multiple radial plates 331 respectively. The hydraulic cylinders are mounted on the drive cylinder 31. The hydraulic cylinders drive the radial plates 331 to move radially inward or radially outward, which can accommodate workpieces of different diameters.

[0039] The drive unit consists of a linear module and a rotary cylinder. The linear module is mounted on the positioning platform 1, and the rotary cylinder is mounted on the slider of the linear module. The drive cylinder 31 is mounted on the output end of the rotary cylinder. The linear module drives the slider to move, and the slider drives the drive cylinder 31 to move through the rotary cylinder. The rotary cylinder can drive the drive cylinder 31 to rotate a certain angle.

[0040] The longitudinal section of the radial plate 331 is C-shaped, and multiple radial plates 331 form a ring structure.

[0041] The drive cylinder 31 has baffles at both ends (not shown in the figure), a connecting groove in the middle of the baffle, and several telescopic cleaning plates (not shown in the figure) on the outside of the connecting groove. Each cleaning plate is equipped with a brush. The workpiece passes through the connecting grooves at both ends. The cleaning plates extend and retract via telescopic cylinders mounted on the baffles.

[0042] As the drive cylinder 31 moves, the cleaning plate extends a brush to clean the surface of the workpiece, preventing debris from entering the drive cylinder 31. During workpiece loading and unloading, the telescopic cylinder retracts the cleaning plate and brush to facilitate workpiece loading and unloading. During workpiece processing, the telescopic cylinder extends the cleaning plate and brush to block the connecting groove, preventing debris from entering.

[0043] The rolling element 3322 is a ball, and the flexible body 3321 is provided with a ball groove, in which the ball rolls.

[0044] The drive cylinder 31 is equipped with clamping cylinders at both ends. The extension rod of the clamping cylinder is equipped with an elastic plate. When the clamping cylinder drives the elastic plate to work, it can clamp and position the workpiece. The clamping cylinder is electrically connected to the control system. The elastic plate can prevent the workpiece from being pinched and damaged.

[0045] In the initial state, the drive cylinder 31 is located between the chuck 2 and the tailstock 4, and the drive cylinder 31, chuck 2 and tailstock 4 are all in a concentric state.

[0046] When a workpiece needs to be loaded, the operator inserts the middle part of the workpiece into the drive cylinder 31 and controls the adjustment mechanism 32 through the control system. The adjustment mechanism 32 drives the radial plates 331 in the multiple clamping units 33 to move radially inward, so that the multiple radial plates 331 drive the flexible bodies 3321 to move radially inward respectively. The flexible bodies 3321 drive the rolling bodies 3322 to contact the surface of the workpiece to center and clamp the workpiece. The rolling bodies 3322 form rolling contact with the workpiece, which not only ensures uniform support force at multiple points, but also avoids scratching the surface of the workpiece blank during clamping. Afterward, the clamping cylinder clamps the workpiece to prevent it from moving.

[0047] After the workpiece is loaded and clamped, the control system controls the chuck 2 to be in the open state and drives the drive cylinder 31 to move to the left through the drive unit. The drive cylinder 31 drives the clamped workpiece to be inserted into the chuck 2 through the clamping cylinder. After the chuck 2 clamps one end of the workpiece, the tailstock 4 moves to the left to position the other end of the workpiece, forming a complete end reference constraint, which stably ensures the machining positioning accuracy.

[0048] After the workpiece is positioned at both ends, it enters the cutting process. At this time, the clamping cylinder releases the workpiece to facilitate the workpiece to be rotated and cut. The chuck 2 clamps the workpiece and drives it to rotate at a constant speed around the axis. The center of the tailstock 4 rotates synchronously with the workpiece, providing stable rotational support and axial positioning for the other end of the workpiece. The turning tool feeds along the axis of the workpiece to cut the outer circle of the workpiece. During the turning process of the turning tool on the workpiece, the drive unit drives the drive cylinder 31 to move axially synchronously with the feed position of the tool, so that the intermediate support unit 3 is always kept in the vicinity of the cutting point. The rolling element 3322 forms a real-time follow-up support for the workpiece near the cutting position. This follow-up support structure can significantly shorten the support span at the cutting point, effectively enhance the rigidity of the cutting part of the long and thin shaft workpiece, and suppress the workpiece bending deformation and high-frequency vibration caused by the cutting force. At the same time, the rolling element 3322 rotates synchronously with the workpiece surface, converting the sliding friction at the support into rolling friction, which will not scratch the machined surface of the workpiece. Combined with the buffering characteristics of the flexible body 3321, it can absorb the cutting impact, further improving the machining accuracy and surface quality of the workpiece.

[0049] When the workpiece needs to be unloaded after processing, the chuck 2 and tailstock 4 stop rotating, the clamping cylinder clamps the workpiece again, the control system controls the chuck 2 to release the workpiece, and drives the tailstock 4 to move away from the workpiece to the right. Then, the drive unit drives the workpiece to the right a certain distance through the drive cylinder 31 and the clamping cylinder, so that the two ends of the workpiece leave enough clearance between the chuck 2 and the tailstock 4. Afterwards, the drive unit drives the workpiece to rotate to a preset circumferential angle through the drive cylinder 31 and the clamping cylinder, so that the keyway, flat part and positioning plane of the workpiece are aligned with the alignment structure of the picking station, which is adapted to the circumferential positioning requirements of automated gripping, eliminating the need for manual secondary flipping and adjustment, and reducing the risk of collision during unloading. Finally, the adjusting mechanism 32 drives the radial plates 331 in the multiple clamping units 33 to move radially outward, so that the multiple radial plates 331 and the rolling elements 3322 do not contact the workpiece surface. At the same time, the clamping cylinder releases the workpiece, and the operator removes the processed workpiece. The entire tooling can realize the full automation of loading, positioning, support, and unloading, effectively reducing the intensity of manual labor and operational safety risks, and improving the overall processing speed.

[0050] like Figures 6-7 As shown, in Embodiment 2 of the present invention, an optimized design is made based on Embodiment 1, providing a flexible body 3321, which prevents the shaft workpiece from being pinched or damaged when it rotates due to the elastic arrangement between the fixed cylinder 33211 and the sliding cylinder 33212.

[0051] The specific details of Embodiment 2 are as follows: The flexible body 3321 includes a fixed cylinder 33211 and a sliding cylinder 33212; the fixed cylinder 33211 is mounted on the radial plate 331, and a sliding cavity is provided inside the fixed cylinder 33211; the sliding cylinder 33212 is slidably connected to the sliding cavity; an elastic element (not shown in the figure) is connected between the fixed cylinder 33211 and the sliding cylinder 33212; the rolling body 3322 is rotatably mounted on the sliding cylinder 33212.

[0052] The fixed cylinder 33211 and the sliding cylinder 33212 are slidably connected by a guide key and a guide groove. The guide key is provided on the sliding cylinder 33212, and the guide groove is provided on the fixed cylinder 33211. The guide key slides in the guide groove and limits the maximum extension stroke of the sliding cylinder 33212.

[0053] The elastic element is a spring.

[0054] When the rolling element 3322 abuts against the workpiece surface, the sliding cylinder 33212 moves inward toward the fixed cylinder 33211 under the reaction force of the workpiece. Simultaneously, the sliding cylinder 33212 compresses the elastic element, automatically compensating for roundness deviations and dimensional tolerances of the workpiece surface. This ensures that all rolling elements 3322 can uniformly conform to the workpiece surface, avoiding excessive stress at a single point. At the same time, flexible buffering offsets clamping impacts, preventing surface damage and dents caused by rigid clamping, making it particularly suitable for clamping thin-walled shaft workpieces. When the clamping force is removed, the elastic element releases its elastic force, pushing the sliding cylinder 33212 to automatically reset, ensuring consistent support state for each clamping operation and high clamping repeatability.

[0055] like Figures 6-7 As shown, Embodiment 3 of the present invention further optimizes the design based on Embodiment 2 by incorporating fluid within the sliding cavity to further improve the control accuracy of the clamping force. The fluid used is oil.

[0056] The specific content of Embodiment 3 is as follows: fluid is provided in the sliding cavity, and a force measuring element is provided in the fixed cylinder 33211 corresponding to the position of the fluid. The force measuring element is electrically connected to the control system.

[0057] The force measuring element is a pressure sensor, which is electrically connected to the control system.

[0058] A sealing plate or sealing ring is provided between the guide key and the guide groove to achieve a sliding seal between the guide key and the guide groove, so as to facilitate the filling of fluid.

[0059] The fluid filling the sliding cavity can uniformly transmit contact pressure. When the sliding cylinder 33212 is compressed and retracts, the fluid inside the cavity is squeezed, causing a pressure change. The force measuring element on the fixed cylinder 33211 collects the fluid pressure signal in real time and transmits it to the control system, which accurately converts it into the current actual clamping support force. The control system dynamically adjusts the feed amount of the adjusting mechanism 32 according to the preset force threshold, forming a closed-loop control of the clamping force. This prevents insufficient clamping force from causing the workpiece to shift during processing, and also avoids excessive clamping force from causing plastic deformation of the workpiece. This structure allows for flexible setting of clamping parameters for workpieces of different materials and wall thicknesses, significantly improving clamping reliability and workpiece processing yield.

[0060] like Figures 6-7As shown, in Embodiment 4 of the present invention, the design is further optimized based on Embodiment 3 by using a thermally expanding medium for the fluid to achieve stepless adjustment of the support stiffness.

[0061] The specific details of Embodiment 4 are as follows: The fluid is a thermally expanding medium; a heating element and a temperature measuring element are installed inside the fixed cylinder 33211; the heating element and the temperature measuring element are electrically connected to the control system. The heating element is a heating wire, a heating plate, etc., and the temperature measuring element is a temperature sensor. Both the fixed cylinder 33211 and the sliding cylinder 33212 are made of heat-insulating material.

[0062] During the rough machining of the workpiece, the workpiece is rotated by the chuck 2. At this time, the control system controls the heating element to heat the thermal expansion medium. After the medium is heated, its volume expands, which increases the pressure in the sliding cavity. This causes the sliding cylinder 33212 to extend radially and clamp the workpiece, thereby increasing the rigidity of the sliding cylinder 33212, reducing the probability of deformation of the workpiece due to pressure during the turning process, and improving stability.

[0063] During the finishing process, the workpiece is rotated by the chuck 2. At this time, the control system controls the heating element to reduce the heating power or stop heating, the pressure in the sliding cavity decreases, and the stiffness of the flexible body 3321 decreases, so as to absorb cutting vibration and improve surface quality.

[0064] After the workpiece is processed, the thermal expansion medium is cooled to the set temperature through an external cooling structure or natural air cooling to prepare for the next operation.

[0065] This embodiment is applicable to processing scenarios where the interval between roughing and finishing processes is relatively long.

[0066] like Figures 6-7 As shown, in Embodiment 5 of the present invention, the design is further optimized based on Embodiment 3. The fluid used is magnetorheological fluid, which realizes the adjustment of stiffness during clamping and the adjustment of buffering and shock absorption of workpieces during loading and unloading.

[0067] The specific details of Example 5 are as follows: The fluid is a magnetorheological fluid. An excitation assembly is installed inside the fixed cylinder 33211, and the excitation assembly is electrically connected to the control system. The fixed cylinder 33211 has a cylinder structure, and the sliding cylinder 33212 has a piston rod structure. The sliding cylinder 33212 divides the fixed cylinder 33211 into two independent chambers: a rod chamber and a rodless chamber. The piston has at least one damping through-hole, which connects the rod chamber and the rodless chamber. The magnetorheological fluid can flow between the rod chamber and the rodless chamber through the damping through-hole. The elastic element is installed in the rodless chamber. The excitation assembly is an excitation coil, which is installed inside the fixed cylinder 33211 and is used to apply a controllable magnetic field to the magnetorheological fluid.

[0068] During the workpiece loading and unloading clamping stage, the control system controls the excitation component to pass a weak current or not pass a current. At this time, the magnetorheological fluid is in a low viscosity state, the flow resistance of the magnetorheological fluid through the damping hole is small, the overall support stiffness of the flexible body 3321 is low, and the rolling body 3322 can produce a large elastic yield when it contacts the workpiece, buffering the contact impact at the moment of clamping, avoiding bumping and scratching the machined surface of the workpiece or the blank reference surface, and effectively protecting the precision shaft.

[0069] After clamping and centering are completed, the control system supplies basic operating current to the excitation component. The magnetic field generated by the excitation component acts on the magnetorheological fluid, causing its viscosity and shear yield strength to increase rapidly. The resistance of the magnetorheological fluid when passing through the damping orifice increases, and the support stiffness of the flexible body 3321 is increased simultaneously, ensuring stable workpiece clamping and preventing movement or skewness.

[0070] During the roughing stage of the workpiece, the control system increases the current of the excitation component, and the magnetic field generated by the excitation component gradually strengthens. The shear yield strength of the magnetorheological fluid is greatly improved, and the magnetorheological fluid is in a near-solid state. The flexible body 3321 is close to a rigid support state, which can provide high-strength intermediate support, effectively resist the radial load generated by large cutting forces, reduce the bending deformation of long shaft workpieces, and improve the dimensional stability and material removal efficiency of roughing.

[0071] During the workpiece finishing stage, the control system dynamically adjusts the magnitude of the excitation current based on real-time cutting parameters and radial runout data collected by the detection unit. Utilizing the millisecond-level stiffness response characteristics of the magnetorheological fluid, it changes the flow resistance of the damping through-hole in real time, matches the support damping at different cutting positions, accurately suppresses high-frequency chatter during the cutting process, significantly reduces workpiece surface roughness, and improves machining accuracy and surface quality.

[0072] This embodiment is applicable to processing scenarios where the interval between roughing and finishing processes is short and requires rapid switching.

[0073] like Figures 3-6 As shown, in Embodiment Six of the present invention, the design is further optimized based on the embodiment, providing an adjustment mechanism 32 implementation that is different from Embodiment One. It adopts a linkage structure for power transmission, which can realize the simultaneous radial movement of multiple radial plates 331, avoid the radial plates 331 from tilting, and the structure is simpler.

[0074] The specific content of Embodiment Six is ​​as follows: The adjustment mechanism 32 includes a movable ring 321 and a linear push rod 322. Two movable rings 321 are provided, and the two movable rings 321 are slidably mounted on the drive cylinder 31. The two movable rings 321 are respectively connected to the two ends of the linear push rod 322. The drive cylinder 31 has through slots at the positions corresponding to the two movable rings 321. Each movable ring 321 is rotatably connected to the radial plate 331 through a connecting rod 323.

[0075] The linear push rod 322 is a bidirectional push rod with two telescopic parts. The two telescopic parts of the linear push rod 322 are respectively connected to two moving rings 321, and the cylinder of the linear push rod 322 is mounted on the drive cylinder 31.

[0076] When clamping the workpiece, the linear push rod 322 drives the two moving rings 321 to slide axially toward each other along the outer wall of the drive cylinder 31, so that the two moving rings 321 move closer to each other. The two moving rings 321 convert the axial movement into the radial feed motion of the radial plate 331 through the connecting rod 323, which drives multiple sets of clamping units 33 to synchronously retract toward the workpiece axis, thus completing the centering and clamping of the workpiece. When the workpiece is released, the linear push rod 322 extends and drives the two moving rings 321 to slide in opposite directions, so that the two moving rings 321 move away from each other. The two moving rings 321 pull the radial plate 331 radially outward through the connecting rod 323, thereby releasing the clamping constraint on the workpiece.

[0077] The symmetrical transmission structure is subjected to balanced force without eccentric load, and the feed synchronization of multiple radial plates 331 is high, which can effectively ensure the centering and clamping accuracy of the workpiece and avoid workpiece skewing caused by unilateral force. The linkage transmission has strong load-bearing capacity and high transmission efficiency, and can output stable and reliable clamping force to meet the clamping requirements of large-diameter and heavy shafts. At the same time, the main transmission structure is arranged outside the drive cylinder 31, which makes it easy to add a protective structure to resist the corrosion of chips and cutting fluid, making daily maintenance and repair more convenient and adaptable to the complex working conditions of cutting.

[0078] like Figures 2-3 As shown, Embodiment Seven of the present invention further optimizes the design based on Embodiment One, and provides a different implementation of the drive unit than Embodiment One, realizing the axial movement and circumferential rotation functions of the drive cylinder 31. The structure is simpler and can be adapted to material handling stations at different positions.

[0079] The specific content of Embodiment 7 is as follows: The driving unit includes a linear motion mechanism 34 and a rotating mechanism 35. The linear motion mechanism 34 is mounted on the positioning platform 1, and the output end of the linear motion mechanism 34 is connected to a moving platform 341. The moving platform 341 moves linearly on the positioning platform 1. The rotating mechanism 35 is mounted on the moving platform 341, and the output end of the rotating mechanism 35 is connected to the driving cylinder 31. The linear motion mechanism 34 is a linear electric cylinder, and the rotating mechanism 35 is a rotary cylinder or a rotary motor.

[0080] The drive unit adopts a modular design combining linear and rotary components. The linear movement mechanism 34 drives the moving table 341 to reciprocate along the axial direction of the positioning table 1 through the output end. The rotary mechanism 35 moves synchronously with the moving table 341, thereby driving the drive cylinder 31 to complete the overall axial feed and retraction.

[0081] When the workpiece is loaded, the drive cylinder 31 moves forward and accurately sends the pre-clamped workpiece into the chuck 2. After the workpiece is processed, the drive cylinder 31 moves backward, so that the two ends of the workpiece are separated from the positioning area of ​​the chuck 2 and the tailstock 4, leaving space for unloading.

[0082] The rotating mechanism 35 is mounted on the moving table 341. The output end of the rotating mechanism 35 is connected to the drive cylinder 31. The rotating mechanism 35 drives the workpiece to rotate at a set angle through the drive cylinder 31 so that the workpiece is facing the unloading position, adapting to the unloading requirements of different directions.

[0083] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A positioning fixture for machining shaft-type workpieces, characterized in that: It includes a positioning platform (1), a chuck (2), an intermediate support unit (3), and a tailstock (4), wherein the chuck (2) and the tailstock (4) are respectively installed on both sides of the positioning platform (1); The intermediate support unit (3) includes a drive unit, a detection unit, a drive cylinder (31), an adjustment mechanism (32), and multiple clamping units (33). The drive unit is installed on the positioning table (1), and the output end of the drive unit is connected to the drive cylinder (31). The detection unit is installed on the drive cylinder (31), and the adjustment mechanism (32) is installed on the drive cylinder (31). Multiple clamping units (33) are arranged circumferentially along the drive cylinder (31). Each clamping unit (33) includes a radial plate (331) and multiple clamping members (332). The radial plate (331) is located inside the drive cylinder (31) and is connected to the adjustment mechanism (32) in a transmission manner. The clamping member (332) includes a flexible body (3321) and a plurality of rolling elements (3322), the flexible body (3321) being mounted on a radial plate (331), and the plurality of rolling elements (3322) being mounted on the flexible body (3321).

2. The positioning fixture for machining shaft-type workpieces according to claim 1, characterized in that: The flexible body (3321) includes a fixed cylinder (33211) and a sliding cylinder (33212); The fixed cylinder (33211) is mounted on the radial plate (331), and a sliding cavity is provided inside the fixed cylinder (33211). The sliding cylinder (33212) is slidably connected to the sliding cavity. An elastic element is connected between the fixed cylinder (33211) and the sliding cylinder (33212); The rolling element (3322) is rotatably mounted on the sliding cylinder (33212).

3. The positioning fixture for machining shaft-type workpieces according to claim 2, characterized in that: The sliding cavity is filled with fluid, and the fixed cylinder (33211) is provided with a force measuring element at the position corresponding to the fluid. The force measuring element is electrically connected to the control system.

4. A positioning fixture for machining shaft-type workpieces according to claim 3, characterized in that: The fluid is a thermally expanding medium. The fixed cylinder (33211) is equipped with a heating element and a temperature measuring element, which are electrically connected to the control system.

5. A positioning fixture for machining shaft-type workpieces according to claim 3, characterized in that: The fluid is a magnetorheological fluid, and an excitation assembly is provided inside the fixed cylinder (33211). The excitation assembly is electrically connected to the control system.

6. A positioning fixture for machining shaft-type workpieces according to claim 1, characterized in that: The adjustment mechanism (32) includes a movable ring (321) and a linear push rod (322). There are two movable rings (321), which are slidably mounted on the drive cylinder (31). The two movable rings (321) are respectively connected to the two ends of the linear push rod (322). The drive cylinder (31) has through slots at the positions corresponding to the two moving rings (321), and each moving ring (321) is rotatably connected to the radial plate (331) through a connecting rod (323).

7. A positioning fixture for machining shaft-type workpieces according to claim 1, characterized in that: The drive unit includes a linear motion mechanism (34) and a rotation mechanism (35). The linear motion mechanism (34) is mounted on the positioning table (1). The output end of the linear motion mechanism (34) is connected to a moving table (341). The rotation mechanism (35) is mounted on the moving table (341). The output end of the rotation mechanism (35) is connected to the drive cylinder (31).

8. A positioning fixture for machining shaft-type workpieces according to claim 1, characterized in that: The longitudinal section of the radial plate (331) is C-shaped, and multiple radial plates (331) form a ring structure.

9. A positioning fixture for machining shaft-type workpieces according to claim 1, characterized in that: The drive cylinder (31) is provided with baffles at both ends, a connecting groove is provided in the middle of the baffle, and a number of telescopic cleaning plates are provided on the outside of the connecting groove, and brushes are provided on the cleaning plates.

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