A three-jaw chuck with self-compensating clamping force

Abstract

A three-jaw chuck with self-compensation for clamping force relates to a clamping device. In order to solve the problem that the clamping force provided by the movable jaws will periodically decrease with the rotation of the three-jaw chuck, affecting the processing accuracy of the workpiece, and in severe cases, the workpiece clamping failure is likely to occur. The present invention includes a chuck base and three movable jaws, each movable jaw is arranged along the circumferential direction of the chuck base and is movably connected to the chuck base; each movable jaw includes a jaw collet, a variable stiffness support column and a jaw mounting seat, the jaw collet is installed at one end of the jaw mounting seat and can move along the clamping force direction, and the variable stiffness support column is supported between the jaw collet and the jaw mounting seat; when the jaw collet loses the clamping force with the rotation of the three-jaw chuck, the stiffness of the variable stiffness support column is increased to compensate for the clamping force lost by the movable jaw. The present invention is mainly used for fine-tuning the clamping force of the movable jaw under dynamic conditions.

Description

Technical Field

[0001] The invention relates to a clamping device, in particular to a three-jaw chuck. Background Art

[0002] Currently, when using a three-jaw chuck, the clamping force is typically applied manually before the machining process. Control of this force often relies on the worker's experience and judgment. During the machining of some precision workpieces, the magnitude of the clamping force can affect the workpiece's accuracy. Excessive clamping force can cause the workpiece to deform under clamping, impacting machining accuracy. However, insufficient clamping force can lead to clamping failure during machining due to vibration and other factors, potentially causing production safety accidents. Furthermore, during turning, the clamping force provided by each jaw of a three-jaw chuck fluctuates periodically with rotation. As the speed changes, the clamping force provided by each jaw varies due to its own inertia, further impacting machining accuracy and contributing to clamping failures.

[0003] Among existing patents, those related to three-jaw chuck clamping force control include CN201720209996.6 and CN201821012143.4. CN201720209996.6 provides a three-jaw chuck positioning and locking mechanism with adaptive clamping force. This patent allows for real-time adjustment of the three-jaw chuck's clamping force in static conditions, but cannot achieve real-time adjustment of the clamping force of the three-jaw chuck's jaws in dynamic conditions. CN201821012143.4 provides a three-jaw chuck for machine tools with excellent fixing performance. However, this patent can only detect whether the clamping force meets the requirements and still relies on workers to manually adjust the clamping force, making it impossible to achieve real-time compensation of the clamping force during the machining process. Summary of the Invention

[0004] In view of this, the present invention provides a three-jaw chuck with self-compensating clamping force, which adjusts the stiffness of the variable-rigidity support column to achieve adjustment of the clamping force of the movable jaws.

[0005] The technical solution adopted by the present invention to solve the above technical problems is:

[0006] A three-jaw chuck with self-compensating clamping force comprises a chuck base and three movable jaws, each movable jaw being arranged along the circumferential direction of the chuck base and movably connected to the chuck base; each movable jaw comprises a jaw collet, a variable stiffness support column and a jaw mounting seat, the jaw collet being mounted on one end of the jaw mounting seat and movable along the clamping force direction, the variable stiffness support column being supported between the jaw collet and the jaw mounting seat; when the jaw collet loses clamping force as the three-jaw chuck rotates, the stiffness of the variable stiffness support column is increased to compensate for the clamping force lost by the movable jaw.

[0007] Preferably, the variable stiffness support column is a piezoelectric ceramic column. As the clamping force of the clamping jaws is lost, the input voltage of the piezoelectric ceramic column increases to improve the stiffness of the piezoelectric ceramic column.

[0008] Preferably, it also includes a circuit module for power transmission and signal transmission, which connects the piezoelectric ceramic column with the external voltage and information receiving module to achieve dynamic power transmission and signal transmission during the rotation of the piezoelectric ceramic column.

[0009] Preferably, the circuit module includes a conductive slip ring and two brushes. The conductive slip ring is coaxially arranged on the outer circumference of the chuck base. The conductive slip ring has a positive conductive groove and a negative conductive groove. The two brushes are hinged to the processing machine tool. The positive conductive groove connects one of the brushes to the positive pole of the piezoelectric ceramic column, and the negative conductive groove connects the other brush to the negative pole of the piezoelectric ceramic column. The movable claw and the conductive slip ring rotate with the chuck base, and the two brushes slide and contact in the corresponding positive conductive groove and negative conductive groove to transmit the voltage signal of the piezoelectric ceramic column and input voltage to the piezoelectric ceramic column.

[0010] Preferably, the circuit module further comprises two tension springs, each tension spring corresponding to a brush, and the tension springs connect the graphite brushes to the processing machine tool to ensure that the graphite brushes are always in contact with the conductive slip rings.

[0011] Preferably, the circuit module also includes three transmission units for transmitting voltage signals between the piezoelectric ceramic column and the conductive slip ring, each transmission unit corresponds to a movable claw, and the transmission unit includes a sliding contact strip and two sliding pins. The sliding contact strip is provided with a positive conductive metal wire and a negative conductive metal wire. One end of the positive conductive metal wire is connected to the positive pole of the piezoelectric ceramic column, and the other end extends to one side end surface of the claw mounting seat and is slidingly connected to one of the sliding pins, and one of the sliding pins is connected to the positive conductive sliding groove of the conductive slip ring; one end of the negative conductive metal wire is connected to the negative pole of the piezoelectric ceramic column, and the other end extends to the other side end surface of the claw mounting seat and is slidingly connected to another sliding pin, and the other sliding pin is connected to the negative conductive sliding groove of the conductive slip ring.

[0012] Preferably, the jaw chuck is connected to the jaw mounting seat via a flexible hinge, so that the jaw chuck can move relative to the jaw mounting seat along the direction of the clamping force.

[0013] Preferably, a groove is provided on the side of the jaw chuck facing the variable stiffness support column, one end of the variable stiffness support column is fixedly connected to the jaw mounting seat and pre-tightened, and the other end of the variable stiffness support column is inserted into the groove on the jaw chuck to ensure that the variable stiffness support column supports the jaw chuck along the clamping force direction of the jaw chuck.

[0014] The beneficial effects of the present invention compared with the prior art are:

[0015] 1. The design of the movable jaws of this invention allows for real-time adjustment of the clamping force of the movable jaws during the dynamic operation of the three-jaw chuck by varying the stiffness of the variable-stiffness support column. This maintains the clamping force of the jaw chuck on the workpiece within a preset range, ensuring workpiece machining accuracy and preventing clamping failure. Automatic compensation of the clamping force during dynamic clamping is achieved without the need for manual adjustment.

[0016] 2. The variable-rigidity support column of the present invention utilizes a piezoelectric ceramic column. This column functions as a pressure sensor, measuring the real-time clamping force of the movable jaws. It also allows for rapid adjustment of its own stiffness to precisely fine-tune the clamping force of the jaw chuck. The piezoelectric ceramic column design achieves closed-loop control, ensuring the stability of the three-jaw chuck's clamping force and the reliability of its clamping during cutting. The piezoelectric drive used to adjust the jaw chuck's support force offers advantages over motor drive, such as high positioning accuracy, compact size, fast response, and no electromagnetic interference, as well as a higher load capacity.

[0017] 3. The connection design of the jaw chuck, jaw mounting seat and flexible hinge of the present invention ensures the structural rigidity and stability of the jaw chuck in the working force direction, avoids shaking when clamping the workpiece for processing, ensures the stability of clamping during the entire processing process, ensures the subsequent processing quality, and improves safety.

[0018] 4. The present invention uses a circuit module to transmit the voltage signal of the piezoelectric ceramic column and provide voltage for the piezoelectric ceramic column, thereby avoiding the entanglement of the power cord during use.

[0019] 5. In the present invention, each brush is tightened by a tension spring. The graphite brush is always in contact with the conductive slip ring under the tension of the tension spring, ensuring the reliability of voltage signal transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings are incorporated in and constitute a part of this application and are used to provide a further understanding of the present invention.

[0021] Figure 1 A schematic top view of a three-jaw chuck that implements self-compensation of clamping force according to the present invention.

[0022] Figure 2 A schematic structural diagram of a three-jaw chuck that realizes self-compensation of clamping force according to the present invention.

[0023] Figure 3 An exploded view of the three-jaw chuck with self-compensation of clamping force according to the present invention.

[0024] Figure 4 for Figure 2 A partial enlarged view of point A in the middle.

[0025] Figure 5 for Figure 2 A partial enlarged view of point B in the middle.

[0026] Figure 6 for Figure 1 A partial enlarged view of point C in the middle.

[0027] Explanation of the reference numerals: 1-chuck base; 11-chuck base; 12-chuck top seat; 2-movable jaw; 21-jaw chuck; 22-variable stiffness support column; 23-jaw mounting seat; 3-circuit module; 31-conductive slip ring; 311-positive conductive slide groove; 312-negative conductive slide groove; 32-brush; 33-support frame; 34-tension spring; 35-sliding contact strip; 351-positive conductive metal wire; 352-negative conductive metal wire; 36-sliding pin; 4-flexible hinge; 41-metal sheet. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0029] General three-jaw chucks include pneumatic three-jaw chucks and three-jaw chucks that drive the movable jaws to move through spiral tooth grooves. Regardless of the type of three-jaw chuck, during turning, due to the high-speed rotation of the three-jaw chuck, under inertia, the clamping force provided by each movable jaw will periodically decrease as the three-jaw chuck rotates. At the same time, as the speed of the three-jaw chuck increases, the clamping force of the movable jaws will gradually decrease. Excessive clamping force will cause the workpiece to vibrate during the machining process, affecting the machining accuracy of the workpiece. In severe cases, the workpiece clamping failure may occur, causing production safety accidents.

[0030] See also Figures 1 to 6 The embodiment of the present application provides a three-jaw chuck with self-compensating clamping force, including a chuck base 1 and three movable jaws 2. The chuck base 1 includes a detachably connected chuck base 11 and a chuck top 12. The chuck top 12 is evenly provided with three mounting grooves along the circumferential direction. A movable jaw 2 is installed in each mounting groove. When the movable jaw 2 moves along the radial direction of the chuck base 11, the diameter of the clamping opening enclosed by the three movable jaws 2 changes, thereby realizing the adjustment of the initial clamping force of the three-jaw chuck. Figure 1 and Figure 6The clamping jaw 21 is fixed to the side of the clamping jaw 21 and is fixed to the clamping jaw 21 so as to prevent the clamping jaw 21 from sliding out of the clamping jaw 21. Since the jaw chuck 21 is movably connected to the jaw mounting base 23, when the three-jaw chuck rotates, the jaw chuck 21 will move outward under centrifugal force, thereby causing further loss of the clamping force of the jaw chuck 21. The jaw chuck 21 moves outward under centrifugal force and squeezes the variable stiffness support column 22, at which time the variable stiffness support column 22 is bent. This embodiment increases the stiffness of the variable stiffness support column 22 to counteract the outward squeezing force of the jaw chuck 21 and compensate for the clamping force lost by the jaw chuck 21. That is, this embodiment uses the increase in the stiffness of the variable stiffness support column 22 to achieve fine-tuning of the clamping force of the movable jaw 2, so that the clamping force of the jaw chuck 21 on the workpiece remains within a pre-set range, thereby ensuring the processing accuracy of the workpiece and avoiding the occurrence of clamping failure. At the same time, automatic compensation of the clamping force under dynamic clamping can be achieved without manual adjustment.

[0031] like Figure 1 and Figure 6 As shown, since the change in the clamping force of the jaw chuck 21 generally needs to be measured by a pressure sensor, the variable stiffness support column 22 adjusts the stiffness according to the data measured by the pressure sensor. However, since the clamping force of the jaw chuck 21 changes in real time, the frequency of change of the data measured by the pressure sensor is relatively large, resulting in the frequency of the stiffness change of the variable stiffness support column 22 may not be able to adapt to the frequency of change of the clamping force of the jaw chuck 21, and thus the precise fine-tuning of the clamping force of the jaw chuck 21 cannot be achieved.

[0032] To this end, the variable stiffness support column 22 described in this embodiment is a piezoelectric ceramic column. As the clamping force of the claw chuck 21 is lost, the input voltage of the piezoelectric ceramic column increases to improve the stiffness of the piezoelectric ceramic column.

[0033] Piezoelectric ceramics are a special type of ceramic material with a piezoelectric effect. Under the action of external forces, the centers of positive and negative charges inside the ceramic material will undergo relative displacement, resulting in the generation of charges on the surface of the material, thereby realizing the mutual conversion of mechanical energy and electrical energy. In other words, the piezoelectric ceramic column has the characteristics of simultaneous measurement, control and self-feedback, that is, it can be used as a pressure sensor and can also achieve rapid adjustment of its own stiffness, thereby achieving precise fine-tuning of the clamping force of the jaw chuck 21. The design of the piezoelectric ceramic column realizes closed-loop control, ensuring the stability of the clamping force of the three-jaw chuck and the reliability of clamping during cutting. The adjustment of the support force of the jaw chuck adopts piezoelectric drive. Compared with motor drive, piezoelectric drive has the characteristics of high positioning accuracy, small size, fast response speed, no electromagnetic interference, and higher load capacity. At the same time, piezoelectric ceramic sensors are conventional instruments required for force measurement experiments, avoiding the cost of purchasing other high-value sensors.

[0034] The use process of this embodiment is as follows: when the three movable jaws 2 are installed on the chuck base 1, the initial clamping force of the jaw chuck 21 can be measured by the piezoelectric ceramic column. When the initial clamping force is close to the pre-designed clamping force, there is no need to further adjust the clamping force of the three movable jaws 2. During the workpiece processing, as the three-jaw chuck rotates, the clamping force provided by each movable jaw 2 will decrease due to centrifugal force, and will also further decrease as the speed increases; at this time, the squeezing force of the jaw chuck 21 on the piezoelectric ceramic column increases. Under the action of external force, the positive and negative charge centers inside the ceramic material of the piezoelectric ceramic column will undergo relative displacement, resulting in charge on the surface of the material. In other words, the voltage of the piezoelectric ceramic column changes. According to the voltage difference between the actual voltage of the piezoelectric ceramic column and the initial voltage, the voltage of the piezoelectric ceramic column is increased to increase the stiffness of the piezoelectric ceramic column and gradually straighten it. The piezoelectric ceramic column generates an inward squeezing force on the jaw chuck 21, and the clamping force of the jaw chuck 21 increases with the increase of the piezoelectric ceramic column voltage. Therefore, this embodiment realizes the fine adjustment and compensation of the clamping force of the clamping jaw chuck 21 through the design of the piezoelectric ceramic column, thereby ensuring the processing accuracy of the workpiece and avoiding the occurrence of clamping failure.

[0035] like Figures 2 to 5 As shown, during the processing of the workpiece, the three-jaw chuck needs to drive the workpiece and the movable jaw 2 to rotate, and the output of the piezoelectric ceramic column voltage signal and the adjustment of the voltage require circuit implementation. If a power cord is used to connect the piezoelectric ceramic column and the external voltage and information receiving module, the power cord will become entangled and unusable.

[0036] To this end, this embodiment uses a circuit module 3 to transmit the voltage signal of the piezoelectric ceramic column and provide voltage for the piezoelectric ceramic column. The circuit module 3 connects the piezoelectric ceramic column with an external voltage and information receiving module to realize dynamic power transmission and signal transmission of the piezoelectric ceramic column during rotation. Specifically, the circuit module 3 includes a conductive slip ring 31, two brushes 32, and a support frame 33. The conductive slip ring 31 is grooved along the circumferential direction of the chuck top seat 12 and electroplated with metal. Since the voltage of the piezoelectric ceramic column needs to be measured, the positive and negative electrodes of the piezoelectric ceramic column need to be connected. Therefore, the conductive slip ring 31 has a positive conductive groove 311 and a negative conductive groove 312. The positive conductive groove 311 is electrically connected to the positive electrode of the piezoelectric ceramic column, and the negative conductive groove 312 is electrically connected to the negative electrode of the piezoelectric ceramic column. The brushes 32 are graphite brushes. Since graphite has lubricity, the friction between the brushes 32 and the conductive slip ring 31 can be reduced. The two brushes 32 are installed on the processing machine via a support frame 33. One end of one brush 32 is connected to the support frame 33 by a pin hinge, and the other end is slidably connected to the positive conductive slide groove 311 and is always in contact with it; one end of the other brush 32 is connected to the support frame 33 by a pin hinge, and the other end is slidably connected to the negative conductive slide groove 312 and is always in contact with it.

[0037] During use, the movable jaw 2 (piezoelectric ceramic column) and the conductive slip ring 31 rotate with the chuck base 11. Since the two brushes 32 are mounted and fixed on the processing machine, they slide and contact within the corresponding positive and negative conductive grooves 311 and 312. The voltage signal of the piezoelectric ceramic column is transmitted to the two brushes 32 via the positive and negative conductive grooves 311 and 312. The two brushes 32 are connected to a signal amplifier and then to an analog-to-digital converter, which ultimately transmits the digital signal to a computer, which can then read the real-time voltage value of the piezoelectric ceramic column. The computer compares the actual voltage value of the piezoelectric ceramic column with a preset voltage threshold (range value). If the actual voltage value of the piezoelectric ceramic column is less than the preset voltage threshold, the input voltage to the piezoelectric ceramic column is increased to increase the stiffness of the piezoelectric ceramic column. It should be noted that, in this embodiment, only one set of brushes 32 (two brushes 32 form a group) and one conductive slip ring 31 are provided to achieve common control of the three movable jaws 2. If it is desired to achieve individual control of the three movable jaws 2, separate control can be achieved by simply increasing the number of lines (width) of the conductive slip ring 31 and the number of graphite brushes. That is, two additional sets of brushes 32 and two conductive slip rings 31 are provided, for a total of three conductive slip rings 31 and three sets of brushes 32. Each movable jaw 2 corresponds to a conductive slip ring 31 and a set of brushes 32. Each set of brushes 32 is slidably connected to the corresponding conductive slip ring 31. The voltage signal of each movable jaw 2 is transmitted via the corresponding conductive slip ring 31 and brush 32.

[0038] like Figure 1 and Figure 2 As shown, since the brush 32 and the support frame 33 are hingedly connected, when the three-jaw chuck rotates at high speed, the three-jaw chuck may vibrate, thereby causing the brush 32 to have poor contact with the conductive slip ring 31.

[0039] To this end, the circuit module 3 described in this embodiment also includes two tensioning springs 34, each tensioning spring 34 corresponds to a brush 32, the tensioning spring 34 connects the graphite brush and the support frame 33, and the graphite brush is always in contact with the conductive slip ring 31 under the tension of the tensioning spring 34, thereby ensuring the reliability of voltage signal transmission.

[0040] like Figure 3 、 Figure 4 and Figure 5 As shown, since the movable jaw 2 and the conductive slip ring 31 rotate together with the three-jaw chuck body, the two are actually relatively stationary. The piezoelectric ceramic column and the conductive slip ring 31 can be connected by a power cord. However, when assembling different workpieces, the position of the movable jaw 2 needs to be adjusted as the workpiece is replaced. During the adjustment process, the power cord connecting the piezoelectric ceramic column and the conductive slip ring 31 may be damaged.

[0041] To this end, the circuit module 3 in this embodiment further includes three transmission units for transmitting voltage signals between the piezoelectric ceramic column and the conductive slip ring 31 and inputting voltage to the piezoelectric ceramic column, and each transmission unit corresponds to a movable claw 2 . Each transmission unit includes a sliding contact belt 35 and two sliding pins 36. The sliding contact belt 35 is an integrated T-shaped structure. One section of the sliding contact belt 35 is installed on the outer end surface of the claw mounting seat 23, and the other two sections of the sliding contact belt 35 are respectively installed on the two side end surfaces of the claw mounting seat 23. The sliding contact belt 35 is electroplated with a positive conductive metal wire 351 and a negative conductive metal wire 352. One section of the positive conductive metal wire 351 and one section of the negative conductive metal wire 352 are electroplated side by side on a section of the sliding contact belt 35 on the outer end surface of the claw mounting seat 23, another section of the positive conductive metal wire 351 is electroplated on a section of the end surface of the sliding contact belt 35 on one side of the claw mounting seat 23, and another section of the negative conductive metal wire 352 is electroplated on a section of the end surface of the sliding contact belt 35 on the other side of the claw mounting seat 23. The two sliding pins 36 are mounted on the left and right sides of the mounting slot on the chuck top 12, with one pin 36 being a positive conductive pin and the other being a negative conductive pin. One end of the positive conductive pin is connected to the positive conductive slot 311 of the conductive slip ring 31, while the other end extends into the mounting slot on the chuck top 12 and is slidably connected to the positive conductive metal wire 351. The positive conductive metal wire 351 connects the positive electrode of the piezoelectric ceramic column to the positive conductive pin. The negative conductive pin is connected to the negative conductive slot 312 of the conductive slip ring 31, while the other end extends into the mounting slot between the chuck top 12 and is slidably connected to the negative conductive metal wire 352. The negative conductive metal wire 352 connects the negative electrode of the piezoelectric ceramic column to the negative conductive pin.

[0042] This embodiment uses a sliding contact strip 35 and a sliding pin 36 to achieve wireless power and voltage signal transmission between the piezoelectric ceramic pillars and the conductive slip ring 31. During assembly of different workpieces, as the workpieces are replaced, the position of the movable jaw 2 is adjusted. The sliding pin 36 maintains contact with the conductive metal wire on the sliding contact strip 35. Therefore, adjusting the position of the movable jaw 2 does not affect the electrical connection between the piezoelectric ceramic pillars and the conductive slip ring 31, thus avoiding the problem of easily damaged power cords. The voltage signal from each piezoelectric ceramic pillar is sequentially transmitted to the sliding contact strip 35, sliding pin 36, conductive slip ring 31, and graphite brushes. The graphite brushes ultimately transmit the signal to a computer, which reads the real-time voltage value of the piezoelectric ceramic pillar. Furthermore, multiple adjustments to the position of the movable jaw 2 may result in poor contact between the sliding pin 36 and the positive conductive wire 351 or negative conductive wire 352 on the sliding contact strip 35. Therefore, the sliding pin 36 described in this embodiment can be an elastic sliding pin to ensure reliable contact even after multiple adjustments to the position of the movable jaw 2.

[0043] like Figure 1 and Figure 6As shown, since the claw chuck 21 is installed at one end of the claw mounting base 23 and can move along the clamping force direction, if a mechanical connection is adopted, the structure of the claw will be more complicated.

[0044] To this end, the claw chuck 21 and the claw mounting seat 23 described in this embodiment are connected via a flexible hinge 4. The flexible hinge 4 is composed of four metal sheets 41 symmetrically arranged between the claw chuck 21 and the claw mounting seat 23. The claw chuck 21 is partially inserted into the mounting groove of the claw mounting seat 23. One end of each metal sheet 41 is connected to the side wall of the claw chuck 21, and the other end is connected to the inner wall of the mounting groove on the claw mounting seat 23. As the force on the claw chuck 21 changes, the metal sheet 41 deforms to achieve movement of the claw chuck 21 relative to the claw mounting seat 23 along the direction of the clamping force. In this embodiment, the metal sheet 41, the claw chuck 21, and the claw mounting seat 23 can be set as an integrated structure. That is, when processing the claw chuck 21 and the claw mounting seat 23, four metal sheets 41 are directly reserved to be used as the flexible hinge 4 connecting the claw chuck 21 and the claw mounting seat 23 to ensure the supporting strength of the claw chuck 21. The connection design of the jaw chuck, jaw mounting base and flexible hinge in this embodiment ensures the structural rigidity and stability of the jaw chuck in the working force direction, avoids shaking when clamping the workpiece for processing, ensures the stability of clamping during the entire processing process, ensures the subsequent processing quality, and improves safety.

[0045] The working process of the present invention is further described below to further demonstrate the working principle and advantages of the present invention:

[0046] Clamping force assembly test: During assembly, one end of the piezoelectric ceramic column is fixed on the claw housing, and the other end is pressed against the inner end face of the claw chuck and pre-tightens the piezoelectric ceramic column in advance; the initial clamping force of the claw chuck 21 is measured through the piezoelectric ceramic column. When the initial clamping force is close to the pre-designed clamping force, there is no need to continue adjusting the clamping force of the three movable claws 2.

[0047] Dynamic adjustment of clamping force: Start the three-jaw chuck. As the three-jaw chuck rotates, the clamping force provided by each movable jaw 2 will decrease due to centrifugal force, and will further decrease as the rotation speed increases; at this time, the squeezing force of the jaw clamp 21 on the piezoelectric ceramic column increases. Under the action of external force, the voltage of the piezoelectric ceramic column changes, and the voltage signal of the piezoelectric ceramic column is transmitted to the sliding contact strip 35, the sliding pin 36, the conductive slip ring 31 and the brush 32 in sequence. The two brushes 32 are connected to the signal amplifier, and then to the analog-to-digital converter, and finally the digital signal is transmitted to the computer, which can then read the real-time voltage value of the piezoelectric ceramic column. According to the voltage difference between the actual voltage and the initial voltage of the piezoelectric ceramic column, the voltage of the piezoelectric ceramic column is increased to increase the stiffness of the piezoelectric ceramic column and gradually straighten it. The piezoelectric ceramic column generates an inward squeezing force on the claw chuck 21. The clamping force of the claw chuck 21 increases with the increase of the voltage of the piezoelectric ceramic column, thereby realizing fine-tuning and compensation of the clamping force of the claw chuck 21 in a dynamic state, ensuring the processing accuracy of the workpiece and avoiding the occurrence of clamping failure.

[0048] The movable claws in this embodiment are of modular design, and the piezoelectric ceramic columns and circuit modules are both detachable structures, so corresponding damaged parts can be replaced at any time, reducing maintenance costs.

[0049] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the invention. It should be understood that many modifications may be made to the illustrative embodiments, and that other arrangements may be devised, without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in ways other than those described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be employed in conjunction with other described embodiments.

Claims

1. A three-jaw chuck with self-compensating clamping force, comprising a chuck base and three movable jaws, each movable jaw being arranged along the circumference of the chuck base and movably connected to the chuck base; characterized in that: Each movable jaw includes a jaw chuck, a variable stiffness support column, and a jaw mounting seat. The jaw chuck is mounted on one end of the jaw mounting seat and can move in the direction of the clamping force. The variable stiffness support column is supported between the jaw chuck and the jaw mounting seat. When the jaw chuck loses its clamping force as the three-jaw chuck rotates, the stiffness of the variable stiffness support column is increased to compensate for the loss of clamping force of the movable jaw. The variable stiffness support column is a piezoelectric ceramic column. As the clamping force of the clamping jaws is lost, the input voltage of the piezoelectric ceramic column increases to increase the stiffness of the piezoelectric ceramic column. It also includes a circuit module for transmitting power and signals, the circuit module connects the piezoelectric ceramic column with the external voltage and information receiving module to achieve dynamic power transmission and signal transmission during the rotation of the piezoelectric ceramic column; The circuit module includes a conductive slip ring and two brushes. The conductive slip ring is coaxially arranged on the outer circumference of the chuck base. The conductive slip ring has a positive conductive chute and a negative conductive chute. The two brushes are hinged to the processing machine tool. The positive conductive chute connects one of the brushes to the positive electrode of the piezoelectric ceramic column, and the negative conductive chute connects the other brush to the negative electrode of the piezoelectric ceramic column. The movable claw and the conductive slip ring rotate with the chuck base. The two brushes slide and contact in the corresponding positive and negative conductive chute to transmit the voltage signal of the piezoelectric ceramic column and input voltage to the piezoelectric ceramic column. The circuit module further comprises two tension springs, each tension spring corresponds to a brush, and the tension springs connect the graphite brushes and the processing machine tool to ensure that the graphite brushes are always in contact with the conductive slip rings.

2. A three-jaw chuck with self-compensating clamping force according to claim 1, characterized in that: The circuit module also includes three transmission units for transmitting voltage signals between the piezoelectric ceramic column and the conductive slip ring. Each transmission unit corresponds to a movable claw. The transmission unit includes a sliding contact strip and two sliding pins. The sliding contact strip is provided with a positive conductive metal wire and a negative conductive metal wire. One end of the positive conductive metal wire is connected to the positive pole of the piezoelectric ceramic column, and the other end extends to one side end surface of the claw mounting seat and is slidably connected to one of the sliding pins. One of the sliding pins is connected to the positive conductive sliding groove of the conductive slip ring; one end of the negative conductive metal wire is connected to the negative pole of the piezoelectric ceramic column, and the other end extends to the other side end surface of the claw mounting seat and is slidably connected to another sliding pin. The other sliding pin is connected to the negative conductive sliding groove of the conductive slip ring.

3. The three-jaw chuck with self-compensating clamping force according to claim 1, characterized in that: The clamping jaw chuck is connected to the clamping jaw mounting seat via a flexible hinge, so that the clamping jaw chuck can move relative to the clamping jaw mounting seat along the clamping force direction.

4. The three-jaw chuck with self-compensating clamping force according to claim 1, characterized in that: A groove is provided on the side of the jaw chuck facing the variable stiffness support column. One end of the variable stiffness support column is fixedly connected to the jaw mounting seat and pre-tightened, and the other end of the variable stiffness support column is inserted into the groove on the jaw chuck to ensure that the variable stiffness support column supports the jaw chuck along the clamping force direction of the jaw chuck.

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