Elastic expansion sleeve clamp applied to turning of light differential shell and using method of elastic expansion sleeve clamp

Abstract

The invention discloses an elastic expansion sleeve clamp applied to turning of a lightweight differential shell and a using method of the elastic expansion sleeve clamp, and relates to the technical field of elastic expansion sleeve clamps. Comprising a carrying structure which is assembled with the end part in a lathe of the differential shell through a positioning bolt; and the driving source is arranged in the carrying structure and forms an insertion matching relationship with the carrying structure. The traction assembly and oil liquid circulation are introduced into the clamping assembly, the double effects of clamping and traction are achieved, a traction magnetic attraction rod is matched with a return spring, trace axial traction force can be applied to a shell in the clamping process, a workpiece automatically tends to a machining datum plane in the positioning process, the clamping precision is further improved, and meanwhile, the clamping efficiency is improved. An oil injection channel and an oil drainage channel arranged in the blocking ring column are communicated with the oil storage sleeve, closed lubricating oil circulation can be formed in the clamping mechanism, low-friction operation of a transmission part is kept, the service life is prolonged, and the automatic return and self-lubricating functions are achieved.

Description

An elastic expansion sleeve fixture for machining lightweight differential housings and its application method Technical Field

[0001] This invention relates to the field of elastic expansion sleeve fixture technology, specifically to an elastic expansion sleeve fixture used in the machining of lightweight differential housings and its application method. Background Technology

[0002] In the machining process of lightweight differential housings, the clamping stability, force control accuracy, and adaptability of the fixtures are key to ensuring the quality of the parts.

[0003] A search revealed that Chinese invention patent application with publication number "CN116275172A" describes a process in which parts are fitted onto a main rod during production. A drive assembly is used to simultaneously tighten and clamp the workpiece using a first and a second tensioning element. The first and second tensioning elements, located at both ends inside the workpiece, effectively clamp the workpiece, improving the stability of long workpieces and thus enhancing the processing accuracy and efficiency.

[0004] Furthermore, the Chinese utility model patent application with publication number "CN217316959U" describes a method that, during actual use, when the connecting seat moves towards the chuck with the expansion sleeve, the bottom of the workpiece is close to the expansion sleeve, and the expansion sleeve gradually expands along the side wall of the conical part, so that there is no gap between the bottom of the workpiece and the expansion sleeve, thus achieving precise internal positioning. The positioning device, adjustment positioning and stop block set around the chuck perform precise external positioning of the workpiece, and the workpiece is simultaneously positioned internally and externally, so that the workpiece will not be displaced, reducing clamping errors and ensuring the machining accuracy of the workpiece.

[0005] However, in actual use, the aforementioned disclosed devices and similar existing technology devices generally lack an active traction and correction mechanism for the axial direction of the workpiece. During clamping, they cannot dynamically correct the workpiece's posture. For thin-walled hollow structures such as lightweight differential housings, when the tensioning force is applied radially, slight separation or tilting between the workpiece end face and the positioning reference surface is very likely to occur, causing unstable axial positioning. This results in runout error and coaxiality deviation during turning. Furthermore, under the action of clamping force, the workpiece may slip slightly or spring back, making it difficult to ensure that the inner hole axis is completely aligned with the lathe spindle after clamping, affecting machining accuracy and surface quality. Summary of the Invention

[0006] The purpose of this invention is to provide an elastic expansion sleeve fixture for machining lightweight differential housings and its usage method, so as to solve the problems mentioned in the background art.

[0007] Firstly, to achieve the above objectives, the present invention provides the following technical solution: an elastic expansion sleeve fixture for machining lightweight differential housings, comprising: a mounting structure, assembled with the end portion of the differential housing lathe via positioning bolts; a drive source, disposed inside the mounting structure and forming a plug-in fit with the mounting structure; and a clamping assembly, integrated and fixed on the side of the mounting structure facing the machining end of the differential housing lathe, wherein the clamping assembly, the mounting structure, and the machining end of the differential housing lathe are on the same axis; the clamping assembly includes: a blocking ring column, the bottom axis of which is fixed to the top axis of the mounting structure. The barrier ring column has a through hole at its axial center for accommodating the output shaft of the drive source; several movable slots are evenly distributed on the top and bottom outer periphery of the barrier ring column, and a connecting arm is rotatably connected to each movable slot; the top and bottom of the contact arc plate are hinged to one end of the connecting arm in two movable slots arranged in the same axis, for forming a clamping fit with the inner wall of the differential housing, and the other end of the connecting arm in the two movable slots arranged in the same axis is hinged to the outer wall of the output shaft of the drive source; an assembly notch is provided at the bottom of the contact arc plate for forming a sliding fit with several sets of slide rails distributed along the axial circumference on the top surface of the mounting structure.

[0008] As a further preferred embodiment of this technical solution, the driving source includes: an electro-hydraulic push rod, the rod body of which serves as the output shaft of the driving source, and the top and middle ends of the rod body are provided with associated grooves that match the number and position of the connecting arms, the inner wall of which is used to hinge with the periphery of the other end of the connecting arm.

[0009] As a further preferred embodiment of this technical solution, as the electro-hydraulic push rod extends outward along the axial direction, the connecting grooves at the top and middle ends of the rod synchronously drive the connecting arm, which is hinged to it, to rotate around the movable groove. The end of the connecting arm away from the connecting groove pushes the contact arc plate through the bottom mounting notch along the slide rail on the top surface of the mounting structure to slide radially away from the axis. As the rod continues to extend, the outer arc surface of the contact arc plate contacts the inner wall of the differential housing, and the radial tension force applied by the lever action of the connecting arm continues until the contact arc plate is in contact with the inner wall of the differential housing. As the electro-hydraulic push rod retracts, the connecting groove pulls the connecting arm to rotate in the opposite direction, and the contact arc plate slides along the slide rail towards the axis, disengaging the contact arc plate from the inner wall of the differential housing and releasing the clamping fit.

[0010] As a further preferred embodiment of this technical solution, the mounting structure includes: an assembly bolt ring seat and a connecting assembly ring seat stacked together by positioning bolts, wherein the assembly bolt ring seat is fixed to the lathe end of the differential housing by positioning bolts, and the connecting assembly ring seat is stacked and assembled on the top surface of the assembly bolt ring seat by positioning bolts; an oil storage sleeve, axially fixed to the axial center position of the top surface of the connecting assembly ring seat, and filled with lubricating oil; a mounting sleeve, axially fixed to the top of the oil storage sleeve, and several sets of slide rails are installed on the surface of the mounting sleeve inside the mounting sleeve; and a through channel, which is opened from the axial center of the mounting sleeve and extends to the bottom of the assembly bolt ring seat, and the through channel and the sleeve of the electro-hydraulic push rod are in a plug-in fit relationship.

[0011] As a further preferred embodiment of this technical solution, a traction assembly is interposed and installed inside the barrier ring post. The traction assembly applies traction force to the differential housing during clamping. The traction assembly includes: an oil injection channel located on one side inside the barrier ring post, one end of which communicates with the interior of the oil storage sleeve; and an oil drain channel located on the middle side inside the barrier ring post, one end of which communicates with the interior of the oil storage sleeve. The oil injection channel and the oil drain channel are connected via a spring channel located at the top of the barrier ring post. There is a dimensional difference between the spring channel and the oil drain channel. According to the specification difference, a return spring is installed inside the channel. A pressure hole ring is fixed on the top surface of the return spring. A traction magnetic rod is fixed on the top of the pressure hole ring. A sealing ring fixed to the inner wall of the spring channel is sleeved on the outside of the traction magnetic rod. The sealing ring is used to limit the movement stroke of the traction magnetic rod. A pressure plate is fixed at the bottom of the outside of the electric hydraulic push rod body and is set inside the oil storage sleeve. A blocking plug rod adapted to the oil drain channel is fixed on the top surface of the pressure plate. When the electric hydraulic push rod is pressurized, the blocking plug rod enters the oil drain channel to seal.

[0012] As a further preferred embodiment of this technical solution, maintenance valves are installed on both sides of the outer side of the oil storage sleeve, and the two maintenance valves are used for injecting lubricating oil and discharging lubricating oil, respectively.

[0013] As a further preferred embodiment of this technical solution, several lubrication valves are installed on the outside of the mounting sleeve, and lubricating grease is added to the mounting sleeve through the lubrication valves.

[0014] Secondly, to improve the above technical solution, a method for using an elastic expansion sleeve fixture for machining lightweight differential housings is also proposed, which is applied to the above-mentioned elastic expansion sleeve fixture for machining lightweight differential housings.

[0015] As a further preferred embodiment of this technical solution, the method includes: acquiring attribute data of the electro-hydraulic push rod, including: extension stroke, extension rate, and extension response time; calculating the radial movement distance required for the contact arc plate based on the specifications of the differential housing to be processed, and converting the radial movement distance into the target extension stroke of the electro-hydraulic push rod through the lever transmission ratio between the connecting arm and the electro-hydraulic push rod body; acquiring the impact resistance characteristics of the lightweight material of the differential housing to be processed, and determining the upper limit of the extension rate of the electro-hydraulic push rod; and adjusting the extension response time of the electro-hydraulic push rod based on the lathe machining cycle time to ensure that the clamping action is synchronized with the workpiece transfer process of the lathe.

[0016] As a further preferred embodiment of this technical solution, the method for determining the radial movement distance includes: obtaining the inner hole size parameters of the differential housing to be processed, the initial installation position of the contact arc plate, the effective radius from the hinge point of the arc plate to the contact surface, and the initial clamping angle of the arc plate; establishing the displacement change relationship of the arc plate end along the radial direction of the housing based on the rotational trajectory of the arc plate; calculating the displacement difference generated when the arc plate rotates from the initial position to the target position according to the target clamping radius, wherein the calculation process of the displacement difference includes: determining the angle change of the arc plate according to the initial angle and the target angle; calculating the displacement of the arc plate end relative to the center of the housing in the geometric model according to the angle change; The required radial movement distance is determined by comparing the arc plate displacement with the target difference in the inner diameter of the housing. When the contact arc plate is connected to the electro-hydraulic push rod through a linkage mechanism, a geometric transmission model is established between the linear motion of the push rod and the rotation of the arc plate. The geometric transmission model generates a corresponding data table of the linkage displacement and the arc plate displacement by inputting parameters such as the linkage length, hinge position, and installation angle. Based on the corresponding data table, the linear displacement of the push rod required to achieve the target radial movement is deduced. The theoretical displacement result obtained from the geometric model is superimposed and corrected with the fixture assembly error, manufacturing tolerance, and thermal deformation compensation amount under operating temperature to obtain the final radial movement distance used for control.

[0017] As a further preferred embodiment of this technical solution, the method for converting the target telescopic stroke includes: inputting the corrected radial movement distance through a pre-calibrated geometric ratio of the connecting arm to convert the radial displacement into the target telescopic stroke of the electro-hydraulic actuator; calculating the displacement transmission ratio under the current working condition based on the connecting arm length, installation angle, and force transmission path during the conversion process; calculating the theoretical target telescopic stroke based on the displacement transmission ratio under the current working condition, and introducing the elastic deformation of the connecting arm under stress and the actual displacement deviation compensation term of the actuator; adjusting the theoretical target telescopic stroke through an experimentally calibrated error correction model; and superimposing the adjusted result with the thermal deformation compensation of the fixture at the working temperature to obtain the final target telescopic stroke for electro-hydraulic actuator control.

[0018] As a further preferred embodiment of this technical solution, the method for determining the upper limit of the telescopic rate includes: obtaining the lightweight material parameters used in the differential housing to be processed, including impact resistance, allowable contact pressure, local stiffness, and the equivalent mass when the fixture contacts the workpiece; calculating the allowable energy input range when the arc plate contacts the housing based on the impact absorption capacity of the material; calculating the maximum allowable contact force during the clamping process based on the surface bearing capacity of the housing and the contact area of ​​the arc plate; generating two upper limit values ​​of the rate based on the energy limit and force limit of the electro-hydraulic push rod, and automatically selecting the lower one as the final safe upper limit of the telescopic rate.

[0019] As a further preferred embodiment of this technical solution, the method for adjusting the extension and retraction response time includes: acquiring the machining cycle data of the lathe and the time window reserved for clamping actions in the workpiece transfer process; calculating the available time from the workpiece arrival to the start of cutting on the lathe based on the process cycle, and using this time as the upper limit of the push rod extension and retraction action; dividing the extension and retraction process of the push rod into a rapid approach stage, a smooth deceleration stage, and a closed-loop locking stage; the rapid approach stage advances most of the stroke at the speed of the approach rate upper limit to shorten the clamping preparation time; the smooth deceleration stage automatically reduces the extension and retraction speed when approaching the target position, and achieves a smooth transition through a speed planning algorithm; the closed-loop locking stage switches to position and force composite control within the final clamping range, and ensures that the clamping force is constant through force feedback; dynamically adjusting the duration ratio of each stage in the three-stage control to strictly control the total response time within the time window range; if the response time is detected to exceed the allowable range, automatically performing parameter reallocation, and achieving resynchronization of clamping and machining cycle by shortening the stroke ratio of the rapid stage, increasing the control bandwidth, or optimizing the acceleration and deceleration curve.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: The elastic expansion sleeve fixture and its method of use for machining lightweight differential housings, through the integrated design of the mounting structure, drive source and clamping components, enable the fixture to achieve rapid positioning and stable assembly on the differential housing lathe. The mounting structure adopts a multi-layer ring seat stacking form and is fixed to the end of the lathe by positioning bolts, which makes the fixture installation and disassembly process simple and quick, significantly improving the efficiency of changeover machining in the workshop. At the same time, the through channel set inside the mounting structure forms a plug-in fit with the electro-hydraulic push rod, which not only ensures the coaxiality of the fixture as a whole, but also facilitates the maintenance and replacement of the drive source, reducing downtime.

[0021] Secondly, this invention utilizes an electro-hydraulic push rod as a drive source, combined with a lever transmission structure of connecting arm-contact arc plate, to achieve radially uniform tensioning and clamping of the differential housing's inner hole. Multiple sets of associated grooves on the push rod output shaft form multi-point synchronous transmission with the connecting arm, making the clamping force distribution more balanced and avoiding the problem of localized housing deformation that is easily caused by traditional single-point drive fixtures. The contact arc plate adopts an arc surface fitting design, which can automatically match according to the size of the housing's inner hole, ensuring that the clamping surface forms a stable surface contact with the inner wall of the housing, thereby improving positioning accuracy and machining coaxiality, and reducing clamping deviation.

[0022] Furthermore, this invention achieves a dual function of clamping and traction by introducing a traction component and oil circulation inside the clamping assembly. The traction magnetic rod, in conjunction with the return spring, can apply a small axial traction force to the housing during the clamping process, causing the workpiece to automatically tend towards the machining reference surface during positioning, further improving the clamping accuracy. At the same time, the oil injection and drain channels inside the blocking ring column are connected to the oil storage sleeve, forming a closed lubricating oil circulation inside the clamping mechanism, maintaining low friction operation of the transmission components, extending service life, and providing automatic return and self-lubrication functions.

[0023] Furthermore, the clamp of the present invention introduces a control strategy based on geometric model and mechanical compensation in its usage method. By dynamically calculating and correcting the stroke, speed and response time of the electro-hydraulic push rod, precise control of the clamping action is achieved. The radial movement distance, extension stroke and upper limit of speed are all adjusted in real time according to the characteristics of the shell material and the transmission parameters of the clamp, which effectively prevents deformation or damage to the lightweight shell material caused by excessive clamping force or excessive speed. Attached Figure Description

[0024] Figure 1 is an isometric view of the present invention; Figure 2 is an exploded view of the present invention; Figure 3 is a structural composition diagram of the clamping assembly of the present invention; Figure 4 is an assembly diagram of the internal slide rail and clamping assembly of the mounting sleeve of the present invention; Figure 5 is an assembly diagram of the barrier ring column and the electro-hydraulic push rod of the present invention; Figure 6 is a partial enlarged view of part A in Figure 5; Figure 7 is a planar sectional view of the present invention used to demonstrate the traction assembly; Figure 8 is a planar sectional view of the present invention used to demonstrate the clamping assembly.

[0025] In the diagram: 1. Assembly bolt ring seat; 2. Connecting assembly ring seat; 3. Positioning bolt; 4. Mounting sleeve; 5. Electro-hydraulic push rod; 6. Clamping assembly; 601. Contact arc plate; 602. Assembly notch; 603. Connecting arm; 604. Movable groove; 605. Barrier ring column; 7. Oil storage sleeve; 8. Maintenance valve; 9. Traction assembly; 901. Return spring; 902. Oil drain channel; 903. Oil injection channel; 904. Pressure hole ring; 905. Spring channel; 906. Traction magnetic rod; 907. Sealing ring; 10. Lubrication valve; 11. Slide rail; 12. Barrier plug rod; 13. Pressure plate; 14. Connecting groove. Detailed Implementation

[0026] 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.

[0027] Before understanding the technical solution proposed in this application, it should be clear that the problem solved by this technical device is that when expansion or contraction is applied, the axial orientation is not positioned, which will cause axial movement between the fixture and the differential housing workpiece, resulting in the workpiece machining datum offset, which in turn causes the dimensional and positional accuracy of key parts such as keyways and bearing holes to exceed the tolerance, and even causes the workpiece to loosen and fall off during high-speed turning, which may pose a safety hazard.

[0028] As shown in Figures 1 to 8, this invention provides a technical solution: an elastic expansion sleeve clamp for machining lightweight differential housings. This clamp can effectively achieve high-precision positioning and stable clamping of the differential housing. The specific structure includes the following components: a mounting structure, which is reliably assembled with the end of the differential housing lathe via positioning bolts 3, ensuring the clamp remains stable during operation; a drive source, located inside the mounting structure and forming a plug-in connection with it, providing power input to the clamp and serving as the core component for clamping and releasing actions; and a clamping assembly 6, integrated and fixed on the side of the mounting structure facing the machining end of the differential housing lathe. The clamping assembly 6, the mounting structure, and the machining end of the differential housing lathe are all on the same axis to ensure clamping alignment and machining accuracy.

[0029] As a preferred embodiment, in this embodiment, the clamping assembly 6 includes: a barrier ring post 605, the bottom axis of which is fixed to the top axis of the mounting structure; a through hole at the axis of the barrier ring post 605 for accommodating the output shaft of the drive source, serving as structural support and motion transmission; and several movable slots 604 evenly distributed on the top and bottom outer periphery of the barrier ring post 605, each movable slot 604 rotatably connected to a connecting arm 603, allowing the connecting arm 603 to rotate flexibly within the movable slot 604 and contact the arc plate 601, with an indented surface. The top and bottom of the device are hinged to one end of the connecting arm 603 in the two coaxially arranged movable slots 604, which are used to form a clamping fit with the inner wall of the differential housing to achieve uniform clamping of the workpiece; the other end of the connecting arm 603 in the two coaxially arranged movable slots 604 is hinged to the outer wall of the output shaft of the drive source to form a lever transmission structure. The assembly notch 602 is set at the bottom of the contact arc plate 601, which is used to form a sliding fit with several sets of slide rails 11 distributed along the axial circumference on the top surface of the mounting structure, so that the contact arc plate 601 can move smoothly in the radial direction.

[0030] It is worth noting that in the technical solution proposed in this application, the clamping assembly 6 achieves precise tightening and releasing of the differential housing inner hole through the lever transmission structure formed by the axial extension and retraction movement of the output shaft of the drive source and the connecting arm 603. Specifically, when the drive source retracts the output shaft into the mounting structure, the connecting arm 603 rotates around the rotation fulcrum in the movable groove 604. Its end away from the output shaft pushes the contact arc plate 601 to move radially outward along the sliding fit direction between the assembly notch 602 and the slide rail 11 through the hinge point. The outer surface of the contact arc plate 601 gradually fits against the inner wall of the differential housing, and the axial force of the drive source is amplified into a uniform radial clamping force by utilizing the lever principle. When the drive source extends the output shaft towards the machining end, the connecting arm... 603 rotates in the opposite direction, pulling the contact arc plate 601 to move radially inward along the slide rail 11, releasing the clamping of the workpiece. During this process, the sliding fit between the assembly notch 602 and the slide rail 11 restricts the movement trajectory of the contact arc plate 601, ensuring that it moves smoothly only radially and avoiding offset or tilting. Meanwhile, the blocking ring column 605 provides guidance and support to the output shaft of the drive source through its own axial through hole, preventing radial swaying of the output shaft during extension and retraction, further ensuring the centering and stability of the clamping assembly 6. This design not only achieves uniform transmission of clamping force, but also effectively controls the movement accuracy of the contact arc plate 601 through the cooperation of the mechanical structure, fully meeting the high-precision positioning requirements of the lightweight differential housing for machining fixtures.

[0031] As a supplement to the above implementation scheme, in this implementation scheme, the driving source specifically includes: an electric hydraulic push rod 5, the rod body of which serves as the output shaft of the driving source, and the top and middle ends of the rod body are provided with associated grooves 14 that match the number and position of the connecting arms 603. The inner wall of the associated grooves 14 is used to hinge with the periphery of the other end of the connecting arm 603, thereby realizing power transmission and motion conversion.

[0032] It is worth noting that the specific working process of the clamping component 6 in this technical solution is as follows: As the electric hydraulic push rod 5 extends, when the rod extends outward along the axial direction, the connecting grooves 14 at the top and middle ends of the rod synchronously drive the connecting arm 603, which is hinged to it, to rotate around the movable groove 604. The end of the connecting arm 603 away from the connecting groove 14 pushes the contact arc plate 601 to slide radially away from the axis through the bottom assembly notch 602 along the slide rail 11 on the top surface of the mounting structure. As the rod continues to extend... The outer arc surface of the contact arc plate 601 contacts the inner wall of the differential housing, and the radial tension force gradually increases through the lever action of the connecting arm 603 until the contact arc plate 601 is completely in contact with the inner wall of the differential housing, achieving reliable clamping. As the electric hydraulic push rod 5 retracts, the associated groove 14 pulls the connecting arm 603 to rotate in the opposite direction, and the contact arc plate 601 slides along the slide rail 11 towards the axis. The contact arc plate 601 disengages from the inner wall of the differential housing and releases the clamping fit, facilitating the loading and unloading of the workpiece.

[0033] As a preferred embodiment, in this embodiment, the mounting structure further includes: a mounting bolt ring seat 1 and a connecting mounting ring seat 2, which are stacked by positioning bolts 3. The mounting bolt ring seat 1 is fixed to the end of the differential housing lathe by the positioning bolts 3, and the connecting mounting ring seat 2 is stacked on the top surface of the mounting bolt ring seat 1 by the positioning bolts 3 to form a stable mounting base. An oil storage sleeve 7 is axially fixed to the axis position of the top surface of the connecting mounting ring seat 2 and is filled with lubricating oil for lubricating the internal moving parts. A mounting sleeve 4 is axially fixed to the top of the oil storage sleeve 7. Several sets of slide rails 11 are installed on the surface of the mounting sleeve 4 to provide radial guidance for the contact arc plate 601. A through channel is opened from the axis of the mounting sleeve 4 and extends to the bottom of the mounting bolt ring seat 1. The through channel and the sleeve of the electro-hydraulic push rod 5 are in a plug-in fit relationship to ensure the centering of the push rod during the movement process.

[0034] In a preferred embodiment, a traction assembly 9 is also installed inside the barrier ring post 605. The traction assembly 9 is used to apply auxiliary traction force to the differential housing during clamping, further enhancing clamping stability. Specifically, in this embodiment, the traction assembly 9 includes an oil injection channel 903, which is opened on one side inside the barrier ring post 605, with one end connected to the inside of the oil storage sleeve 7, for injecting lubricating oil. The oil drain channel 902 is located inside the middle side of the barrier ring post 605, and one end is connected to the inside of the oil storage sleeve 7 for the return of lubricating oil. The oil injection channel 903 is connected to the oil drain channel 902 and the spring channel 905 located at the top of the barrier ring post 605. There is a size difference between the spring channel 905 and the oil drain channel 902. According to the size difference, a return spring 901 is installed inside the spring channel 905. A pressure hole ring 904 is fixed to the top surface of the return spring 901. A traction magnetic rod 906 is fixed to the top of the pressure hole ring 904. The part is fitted with a sealing ring 907 fixed to the inner wall of the spring channel 905. The sealing ring 907 is used to limit the movement of the traction magnetic rod 906 to ensure that its movement is smooth and does not exceed the limit. It should be added that, in this embodiment, the bottom end of the electric hydraulic push rod 5 is fixed with a pressure plate 13 set inside the oil storage sleeve 7. The top surface of the pressure plate 13 is fixed with a blocking plug rod 12 that is compatible with the oil drain channel 902. When the electric hydraulic push rod 5 is pressurized, the blocking plug rod 12 enters the oil drain channel 902 to seal, thereby establishing oil pressure to drive the traction magnetic rod 906 to move.

[0035] It should be emphasized that, in the actual operation of the technical solution proposed in this application, the lightweight differential housing is first aligned with the outer surface of the contact arc plate 601 of the clamping assembly 6 using a hoisting device, so that the inner hole of the housing is coaxial with the slide rail 11 on the top surface of the mounting sleeve 4. The workpiece is slowly lowered until the bottom of the housing is in contact with the top surface of the mounting sleeve 4, completing the initial axial positioning. Then, the electric hydraulic push rod 5 is activated, and a "tightening" command is sent to the drive source. The rod of the electric hydraulic push rod 5 begins to slowly extend towards the processing end. The pressure plate 13 fixed at the bottom of the rod moves upward with the rod in the oil storage sleeve 7, squeezing the lubricating oil in the oil storage sleeve 7. At the same time, the rod drives the blocking plug rod 12 to rise synchronously. When the blocking plug rod 12 is fully inserted into the oil drain channel 902, the oil drain channel 902 is sealed, and the lubricating oil in the oil storage sleeve 7 cannot flow back through the oil drain channel 902, and the oil pressure gradually increases.

[0036] The increased oil pressure enters the spring channel 905 inside the blocking ring column 605 through the oil injection channel 903, pushing the pressure hole ring 904 to move towards the machining end against the elastic force of the return spring 901. The traction magnetic suction rod 906 at the top of the pressure hole ring 904 extends along the spring channel 905 and passes through the top surface of the blocking ring column 605. The magnetic suction surface at its top contacts the inner wall of the differential housing, using the strong magnetic attraction effect to apply an axial auxiliary traction force to the housing, preventing the housing from axially moving due to centrifugal force or cutting force during clamping. During this process, the sealing ring 907 strictly limits the travel of the traction magnetic suction rod 906, ensuring that it extends smoothly only along the axial direction and avoiding collision or displacement with the inner wall of the housing.

[0037] Meanwhile, the connecting grooves 14 at the top and middle of the electric hydraulic push rod 5 synchronously drive the connecting arm 603 to rotate around the pivot point in the movable groove 604. The end of the connecting arm 603 away from the connecting groove 14 pushes the contact arc plate 601 to move radially outward along the slide rail 11 on the top surface of the mounting sleeve 4 through the hinge point. The outer surface of the contact arc plate 601 gradually comes into contact with the inner wall of the differential housing. As the rod continues to extend, the lever transmission structure amplifies the axial thrust of the electric hydraulic push rod 5 into a uniform radial clamping force. The contact area between the contact arc plate 601 and the inner wall of the housing continuously increases until it completely clamps the workpiece, achieving high-precision radial positioning. At this time, the radial clamping force of the contact arc plate 601 and the axial traction force of the traction magnetic rod 906 form a bidirectional constraint, completely eliminating the radial offset and axial movement that may occur in the housing during machining, ensuring that the machining accuracy meets the design requirements.

[0038] After the machining process is completed, the control electric hydraulic push rod 5 issues a "release" command, and the rod begins to retract into the mounting structure. The pressure plate 13 moves down with the rod, the oil pressure in the oil storage sleeve 7 decreases, the blocking plug rod 12 exits from the oil drain channel 902, the oil drain channel 902 is unblocked, and the lubricating oil in the spring channel 905 flows back to the oil storage sleeve 7 through the oil drain channel 902. The return spring 901 pushes the pressure hole ring 904 and the traction magnetic suction rod 906 to retract into the spring channel 905 until the traction magnetic suction rod 906 is completely retracted into the blocking ring column 605, releasing the axial traction on the housing. At the same time, the connecting grooves 14 at the top and middle of the rod drive the connecting arm 603 to rotate in the opposite direction, pulling the contact arc plate 601 to move radially inward along the slide rail 11. The contact arc plate 601 disengages from the inner wall of the housing. At this time, the operator can easily remove the machined differential housing from the fixture using the hoisting equipment, completing a complete machining cycle.

[0039] It is worth noting that during the above process, the lubricating oil in the oil storage sleeve 7 not only lubricates the rod body of the electro-hydraulic push rod 5, reducing frictional loss between the rod body and the through channel, but also provides power to the traction assembly 9 through oil pressure transmission, achieving the design goal of one oil for two purposes. The cooperation between the sealing ring 907 and the blocking plug rod 12 effectively prevents the leakage of lubricating oil, ensures the working stability of the traction assembly 9, and further improves the service life and maintenance convenience of the clamp.

[0040] As a preferred embodiment, this embodiment is mainly used to supplement the maintenance of the oil storage sleeve 7 and the mounting sleeve 4. The oil storage sleeve 7 is equipped with maintenance valves 8 on both sides of its exterior. The two maintenance valves 8 are used to inject and discharge lubricating oil, respectively, to facilitate maintenance and lubrication management. Several lubrication valves 10 are installed on the exterior of the mounting sleeve 4. Lubricating grease is added to the mounting sleeve 4 through the lubrication valves 10 to ensure good lubrication of the slide rail 11 and other moving parts, and to extend its service life.

[0041] As a preferred embodiment, this embodiment also proposes a method for using an elastic expansion sleeve fixture for machining lightweight differential housings. This method is applied to an elastic expansion sleeve fixture specifically designed for lightweight differential housings, and its usage process includes the following steps: First, obtain the key attribute data of the electro-hydraulic push rod 5, specifically including: extension stroke range, maximum extension rate, and system extension response time; these data are usually read directly from the equipment technical manual or control system to provide a parameter basis for subsequent control strategies.

[0042] Secondly, based on the actual specifications of the differential housing to be processed—such as the inner diameter, wall thickness, and material properties—the precise radial movement distance required for the contact arc plate 601 is calculated. This calculation needs to take into account the fit between the fixture and the workpiece, and then, through the lever transmission ratio between the connecting arm 603 and the electro-hydraulic push rod 5, the required radial movement distance is converted into the target extension stroke of the electro-hydraulic push rod 5 to achieve reliable clamping of the workpiece.

[0043] Next, the basic mechanical properties of the lightweight material used in the differential housing to be processed are obtained, especially its impact resistance, yield strength and surface hardness. Based on this, the upper limit of the extension rate of the electro-hydraulic push rod 5 is determined to prevent workpiece surface damage or local material deformation caused by excessive clamping speed.

[0044] Finally, based on the actual machining cycle and working cycle of the lathe, the extension and retraction response time of the electro-hydraulic push rod 5 is dynamically adjusted to ensure that the clamping action is precisely synchronized with the lathe's workpiece transfer process, positioning signals and machining start and stop stages, so as to avoid waiting or interference.

[0045] The method for determining the radial movement distance includes the following specific steps: obtaining the inner hole size parameters of the differential housing to be processed, the initial installation position of the contact arc plate 601, the effective radius from the hinge point of the arc plate to the contact surface, and the initial clamping angle of the arc plate, etc.; based on the rotational motion trajectory of the arc plate around the hinge point, establishing a displacement change relationship model of the arc plate end along the radial direction of the housing, which should consider the nonlinear characteristics of the actual motion of the arc plate; and calculating the theoretical displacement difference generated when the arc plate rotates from the initial position to the target position according to the target clamping radius. The specific calculation of the displacement difference includes: determining the angle change based on the initial angle and target clamping angle of the arc plate; calculating the actual displacement of the arc plate endpoint relative to the center of the shell in the established geometric model based on the angle change; comparing the calculated arc plate displacement with the target clamping difference required for the inner diameter of the shell to further determine the required precise radial movement distance; when the contact arc plate 601 is connected to the electro-hydraulic push rod 5 through the linkage mechanism, a geometric transmission model between the linear motion of the push rod and the rotational motion of the arc plate needs to be established to describe their motion coupling relationship; this geometric transmission model generates a corresponding data table of linkage displacement and arc plate radial displacement by inputting multiple parameters (such as the actual length of the linkage, the position of the hinge point, the system installation angle, etc.) for real-time query or control feedback; based on this corresponding data table, the theoretical linear displacement of the push rod required to achieve the target radial movement distance can be derived; after obtaining the theoretical displacement result, the errors existing in the fixture assembly process, the manufacturing tolerances of parts, and the thermal deformation compensation caused by the actual working temperature need to be superimposed and corrected to obtain a final radial movement distance with high precision that can be used for actual control.

[0046] The conversion method for the target telescopic stroke includes: inputting the radial movement distance after the above-mentioned correction process into the system, and converting the radial displacement linearly or nonlinearly into the target telescopic stroke of the electro-hydraulic push rod 5 through the pre-calibrated geometric ratio of the connecting arm 603; during the conversion process, the displacement transmission ratio under the current working condition needs to be calculated based on the actual length, installation angle and force transmission path of the connecting arm 603, which may be dynamically adjusted with the change of clamping position; the theoretical target telescopic stroke is calculated based on the obtained displacement transmission ratio, and the elastic deformation compensation of the connecting arm 603 under stress and the system deviation compensation term of the actual displacement of the push rod are introduced to improve the control accuracy; the theoretical target telescopic stroke is adjusted by the error correction model (such as nonlinear fitting formula or lookup table compensation method) that has been experimentally calibrated in advance to eliminate the influence of friction, hysteresis and nonlinearity in actual motion; the adjusted result is superimposed with the thermal deformation compensation of the fixture at the current working temperature to finally obtain the final target telescopic stroke for servo control of the electro-hydraulic push rod 5.

[0047] The method for determining the upper limit of the telescopic rate includes: obtaining key parameters of the lightweight material used in the differential housing to be processed, including the material's impact resistance, maximum allowable contact pressure, local stiffness characteristics, and equivalent mass when the fixture contacts the workpiece; calculating the maximum allowable energy input range at the moment of contact between the arc plate and the housing based on the material's impact energy absorption capacity to avoid internal cracks or surface crushing of the housing; calculating the maximum allowable contact force during clamping based on the surface bearing stress of the housing and the actual contact area of ​​the arc plate, as a force control boundary condition; and generating two recommended upper limit values ​​for the rate based on the energy limit standard and output force limit standard of the electro-hydraulic push rod 5, respectively. The system will automatically select the lower one as the final safe telescopic rate upper limit to ensure that the clamping process meets the requirements of workpiece safety and equipment reliability.

[0048] The adjustment methods for extension and retraction response time include: acquiring the machining cycle data of the lathe and the strict time window reserved for clamping actions in the workpiece transfer process, which is usually provided by the machine tool CNC system or production cycle controller; calculating the available time from the workpiece being transported to the lathe starting to cut based on the overall process cycle, and using this time as the upper limit of the response time for the push rod extension and retraction action to avoid production line blockage; dividing the entire extension and retraction process of the push rod into three control stages: rapid approach stage, smooth deceleration stage, and closed-loop locking stage. The rapid approach phase advances most of the stroke at the maximum approach speed, significantly shortening the clamping preparation time. The smooth deceleration phase automatically reduces the extension speed as the plate approaches the target position, using an S-shaped speed planning algorithm to achieve a smooth transition and reduce impact and vibration. The closed-loop locking phase switches to a combined position and force control strategy within the final clamping range, ensuring the clamping force remains constant within the set range through real-time force feedback. During these three phases of control, the duration and stroke ratio of each phase are dynamically adjusted to strictly control the total response time within the process time window. If the actual response time exceeds the allowable range, a control parameter reallocation strategy is automatically executed. This involves shortening the stroke ratio of the rapid approach phase, increasing the system control bandwidth, or optimizing the acceleration and deceleration curves to resynchronize the clamping action with the processing cycle, ensuring the continuity and efficiency of the production process.

[0049] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended embodiments and their equivalents.

Claims

1. A flexible expansion sleeve fixture for machining lightweight differential housings, characterized in that, include: The mounting structure is assembled with the end of the differential housing on the lathe via positioning bolts (3); The drive source is located inside the mounting structure and forms a plug-in relationship with the mounting structure; the clamping assembly (6) is integrated and fixed on the side of the mounting structure facing the lathe machining end of the differential housing, and the clamping assembly (6), the mounting structure and the lathe machining end of the differential housing are on the same axis; the clamping assembly (6) includes: a blocking ring column (605), the bottom axis position is fixed with the top axis position of the mounting structure, and the axis position of the blocking ring column (605) is provided with a through hole for adapting the output shaft of the drive source; a number of movable grooves (604) are evenly opened on the top and bottom outer periphery of the blocking ring column (605). Each movable slot (604) is rotatably connected to a connecting arm (603); the top and bottom of the concave surface of the contact arc plate (601) are hinged to one end of the connecting arm (603) in the two movable slots (604) arranged in the same axis, for forming a clamping fit with the inner wall of the differential housing, and the other end of the connecting arm (603) in the two movable slots (604) arranged in the same axis is hinged to the outer wall of the output shaft of the drive source; the assembly notch (602) is set at the bottom of the contact arc plate (601), for forming a sliding fit with several sets of slide rails (11) distributed along the axial circumference on the top surface of the mounting structure.

2. The elastic expansion sleeve fixture for machining a lightweight differential housing as described in claim 1, characterized in that: The driving source includes an electric hydraulic push rod (5), the rod body of which is the output shaft of the driving source. The top and middle ends of the rod body are provided with associated grooves (14) that match the number and position of the connecting arms (603). The inner wall of the associated grooves (14) is used to hinge with the outer periphery of the other end of the connecting arms (603).

3. The elastic expansion sleeve fixture for machining a lightweight differential housing as described in claim 2, characterized in that: As the electric hydraulic push rod (5) extends outward along its axis, the connecting grooves (14) at the top and middle ends of the rod synchronously drive the connecting arm (603) hinged to it to rotate around the movable groove (604). The end of the connecting arm (603) away from the connecting groove (14) pushes the contact arc plate (601) to slide radially away from the axis through the bottom mounting notch (602) along the slide rail (11) on the top surface of the mounting structure. As the rod continues to extend, the contact... The outer arc surface of the arc plate (601) contacts the inner wall of the differential housing, and the radial tension force is applied by the lever action of the connecting arm (603) until the contact arc plate (601) is in contact with the inner wall of the differential housing; as the electric hydraulic push rod (5) retracts, the connecting groove (14) pulls the connecting arm (603) to rotate in the opposite direction, the contact arc plate (601) slides along the slide rail (11) towards the axis, the contact arc plate (601) disengages from the inner wall of the differential housing, and the clamping fit is released.

4. The elastic expansion sleeve fixture for machining a lightweight differential housing as described in claim 2, characterized in that: The mounting structure includes: an assembly bolt ring seat (1) and a connecting assembly ring seat (2) stacked by positioning bolts (3), wherein the assembly bolt ring seat (1) is fixed to the end of the differential housing lathe by positioning bolts (3), and the connecting assembly ring seat (2) is stacked on the top surface of the assembly bolt ring seat (1) by positioning bolts (3); an oil storage sleeve (7) is axially fixed to the axial center position of the top surface of the connecting assembly ring seat (2), and its interior is filled with lubricating oil; a mounting sleeve (4) is axially fixed to the top of the oil storage sleeve (7), and several sets of slide rails (11) are installed on the surface of the mounting sleeve (4); a through channel is opened from the axial center of the mounting sleeve (4) and extends to the bottom of the assembly bolt ring seat (1), and the through channel and the sleeve of the electric hydraulic push rod (5) are in a plug-in fit relationship.

5. The elastic expansion sleeve fixture for machining a lightweight differential housing as described in claim 4, characterized in that: A traction assembly (9) is installed inside the barrier ring post (605). The traction assembly (9) is used to apply traction force to the differential housing during clamping. The traction assembly (9) includes: an oil injection channel (903) located on one side inside the barrier ring post (605), with one end connected to the inside of the oil storage sleeve (7); and an oil drain channel (902) located on the middle side inside the barrier ring post (605), with one end connected to the inside of the oil storage sleeve (7). The oil injection channel (903) and the oil drain channel (902) are connected by a spring channel (905) located at the top of the barrier ring post (605). There is a specification difference between the spring channel (905) and the oil drain channel (902). The spring channel (905) is installed inside according to the specification difference. There is a return spring (901), and a pressure hole ring (904) is fixed on the top surface of the return spring (901). A traction magnetic rod (906) is fixed on the top of the pressure hole ring (904). A sealing ring (907) is fixed on the outside of the traction magnetic rod (906) and fixed on the inner wall of the spring channel (905). The sealing ring (907) is used to limit the movement stroke of the traction magnetic rod (906). A pressure plate (13) is fixed at the bottom of the outside of the electric hydraulic push rod (5) and is set inside the oil storage sleeve (7). A blocking plug rod (12) that is adapted to the oil drain channel (902) is fixed on the top surface of the pressure plate (13). When the electric hydraulic push rod (5) is pressurized, the blocking plug rod (12) enters the oil drain channel (902) for sealing.

6. The elastic expansion sleeve fixture for machining a lightweight differential housing as described in claim 4, characterized in that: Maintenance valves (8) are installed on both sides of the outside of the oil storage sleeve (7). The two maintenance valves (8) are used to inject lubricating oil and discharge lubricating oil, respectively.

7. The elastic expansion sleeve fixture for machining a lightweight differential housing as described in claim 4, characterized in that: Several lubrication valves (10) are installed on the outside of the mounting sleeve (4) to add grease to the mounting sleeve (4).

8. A method of using an elastic expansion sleeve fixture for machining lightweight differential housings, applicable to the elastic expansion sleeve fixture for machining lightweight differential housings as described in any one of claims 1-7, characterized in that... include: Obtain the attribute data of the electro-hydraulic push rod (5), including: extension stroke, extension rate and extension response time; calculate the radial movement distance required for the contact arc plate (601) according to the specifications of the differential housing to be processed, and convert the radial movement distance into the target extension stroke of the electro-hydraulic push rod (5) through the lever transmission ratio between the connecting arm (603) and the rod body of the electro-hydraulic push rod (5); obtain the impact resistance characteristics of the lightweight material of the differential housing to be processed, and determine the upper limit of the extension rate of the electro-hydraulic push rod (5); adjust the extension response time of the electro-hydraulic push rod (5) based on the cycle time of lathe machining to ensure that the clamping action is synchronized with the workpiece transfer process of the lathe.

9. The elastic expansion sleeve fixture for machining a lightweight differential housing as described in claim 8, and its method of use, characterized in that: The method for determining the radial movement distance includes: obtaining the inner hole size parameters of the differential housing to be processed, the initial installation position of the contact arc plate (601), the effective radius from the hinge point of the arc plate to the contact surface, and the initial clamping angle of the arc plate; establishing the displacement change relationship of the arc plate end along the radial direction of the housing based on the rotational motion trajectory of the arc plate; calculating the displacement difference generated when the arc plate rotates from the initial position to the target position according to the target clamping radius, wherein the calculation process of the displacement difference includes: determining the angle change of the arc plate according to the initial angle and the target angle; calculating the displacement of the arc plate end relative to the center of the housing in the geometric model according to the angle change; and comparing the arc plate displacement with the housing displacement. The target difference in the inner diameter is compared to determine the required radial movement distance. When the contact arc plate (601) is connected to the electric hydraulic push rod (5) through the linkage mechanism, a geometric transmission model between the linear motion of the push rod and the rotation of the arc plate is established. The geometric transmission model generates a corresponding data table of the displacement of the connecting rod and the displacement of the arc plate by inputting parameters such as the length of the connecting rod, the hinge position, and the installation angle. Based on the corresponding data table, the linear displacement of the push rod required to achieve the target radial movement is deduced. The theoretical displacement result obtained from the geometric model is superimposed and corrected with the fixture assembly error, manufacturing tolerance, and thermal deformation compensation amount under working temperature to obtain the final radial movement distance used for control.

10. The elastic expansion sleeve fixture for machining a lightweight differential housing as described in claim 8, and its method of use, characterized in that: The conversion method for the target telescopic stroke includes: inputting the corrected radial movement distance through the pre-calibrated geometric ratio of the connecting arm (603) to convert the radial displacement into the target telescopic stroke of the electro-hydraulic push rod (5); calculating the displacement transmission ratio under the current working condition based on the length of the connecting arm (603), the installation angle, and the force transmission path during the conversion process; calculating the theoretical target telescopic stroke based on the displacement transmission ratio under the current working condition, and introducing the elastic deformation of the connecting arm (603) under stress and the actual displacement deviation compensation term of the push rod; adjusting the theoretical target telescopic stroke through the experimentally calibrated error correction model; and superimposing the adjusted result with the thermal deformation compensation of the fixture at the working temperature to obtain the final target telescopic stroke for the control of the electro-hydraulic push rod (5).

11. The elastic expansion sleeve fixture for machining a lightweight differential housing as described in claim 8, and its method of use, characterized in that: The method for determining the upper limit of the telescopic rate includes: obtaining the lightweight material parameters used in the differential housing to be processed, including impact resistance, allowable contact pressure, local stiffness, and equivalent mass when the fixture contacts the workpiece; calculating the allowable energy input range when the arc plate contacts the housing based on the impact absorption capacity of the material; calculating the maximum allowable contact force during the clamping process based on the surface bearing capacity of the housing and the contact area of ​​the arc plate; generating two upper limit values ​​of the rate based on the energy limit and force limit of the electric hydraulic push rod (5), and automatically selecting the lower one as the final safe telescopic rate upper limit.

12. The elastic expansion sleeve fixture for machining a lightweight differential housing as described in claim 8, and its method of use, characterized in that: The adjustment method for the extension and retraction response time includes: acquiring the machining cycle data of the lathe and the time window reserved for the clamping action in the workpiece transfer process; calculating the available time from the workpiece arrival to the start of cutting on the lathe based on the process cycle, and using this time as the upper limit of the response of the push rod extension and retraction action; The extension and retraction process of the push rod is divided into a rapid approach phase, a smooth deceleration phase, and a closed-loop locking phase. In the rapid approach phase, the push rod advances for most of its stroke at the maximum approach speed to shorten the clamping preparation time. In the smooth deceleration phase, the extension and retraction speed is automatically reduced when approaching the target position, and a smooth transition is achieved through a speed planning algorithm. In the closed-loop locking phase, position and force composite control is switched within the final clamping range, and the clamping force is kept constant through force feedback. In the three-stage control, the duration ratio of each stage is dynamically adjusted to ensure that the total response time is strictly controlled within the time window. If the response time is detected to exceed the allowable range, parameter reallocation is automatically performed. By shortening the stroke ratio of the rapid phase, increasing the control bandwidth, or optimizing the acceleration and deceleration curve, the clamping and machining cycle are resynchronized.

Images