Self-centering double-claw type clamp for turning slender shaft, control system and application

Abstract

The invention belongs to the technical field of turning clamps, and particularly relates to a self-centering double-claw type clamp for turning a slender shaft, a control system and application, a three-point type clamping structure in which a clamping wheel is matched with a centering wheel is adopted, in the stage of clamping a workpiece shaft, a first stepping motor drives a sliding base to slide along a shell, the clamping wheel is controlled to be opened and closed through the cooperation of the sliding base and clamping claws, and the clamping wheel is driven to rotate; in the stage of turning the workpiece shaft, the correction mechanism is controlled by the control system to finely adjust the position of the centering wheel, so that the bending deformation of the workpiece shaft in the turning process is reduced; the self-centering double-claw type clamp is applied to turning of the slender shaft workpiece, and the turning quality of the slender shaft workpiece can be effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of turning fixtures, and in particular relates to a self-centering double-claw fixture for turning a slender shaft, a control system and an application thereof. Background Art

[0002] Shaft workpieces occupy a key position in the industry and are widely used in many fields. Turning, as an important processing method for manufacturing shaft workpieces, has experienced a development process from early manual operation to traditional ordinary lathe processing, but traditional lathes have problems such as low efficiency and poor precision consistency. Modern industry has put forward new requirements for turning shaft workpieces with high precision, high surface quality and high efficiency production.

[0003] During the cutting process of shaft workpieces, if the local support rigidity of the workpiece is insufficient, the workpiece will produce elastic deformation and vibration due to the cutting force, resulting in large dimensional accuracy errors of the shaft workpieces, such as increase in diameter size, shape accuracy, roundness error, and cylindricity error.

[0004] Through further research, we found that the slender shaft workpiece has a large aspect ratio and its own rigidity is poor during the cutting process. The slender shaft workpiece is easily deformed under the action of cutting force, the processing accuracy is difficult to guarantee, and there is even a risk of scrapping the parts. Summary of the invention

[0005] The cam is configured to move the two ends of the camshafts relative to the first end of the wheel shaft, and the cam is configured to move the two ends of the camshafts relative to the first end of the wheel shaft.

[0006] Furthermore, the correction mechanism includes a second stepper motor and a correction front fork, the second stepper motor is arranged in a slide seat, a second screw is provided at the output end of the second stepper motor, the slide seat is provided with a guide groove at one end of the centering wheel, the correction front fork is slidably connected to the guide groove, the correction front fork is a U-shaped structure, the centering wheel is arranged in the U-shaped notch of the correction front fork, and the correction front fork is threadedly connected to the second screw.

[0007] Furthermore, the power mechanism includes a first stepper motor and a connecting block, wherein the connecting block is arranged between the two groups of slides and connected to the slides on both sides, and the output end of the first stepper motor is provided with a first screw rod, which is threadedly connected to the connecting block.

[0008] Furthermore, the clamping wheel and the centering wheel both include bearings and rings made of high-strength wear-resistant material that are interference-fitted with the bearings.

[0009] Furthermore, the surface of the high-strength wear-resistant material ring is provided with oblique lines.

[0010] Another object of the present invention is to provide a control system for a self-centering double-jaw clamp for turning slender shafts, using the above-mentioned self-centering double-jaw clamp, including an eddy current displacement sensor and a controller, the eddy current displacement sensor is arranged on both sides of the shell along the axial direction of the clamped workpiece, the controller is electrically connected to the eddy current sensor, the first stepper motor and the second stepper motor respectively, the eddy current sensor respectively collects the displacement of the detection position on both sides of the shell, the controller is used to calculate the number of pulses sent to the second stepper motor according to the displacement obtained by the detection, and the second stepper motor adjusts the position of the centering wheel according to the number of pulses.

[0011] Preferably, the number of pulses is obtained by the following steps:

[0012] S1, the eddy current displacement sensors on both sides measure the displacements of two positions δ1 and δ2, the displacement signals are converted into voltage signals V1 and V2 by the signal converter, and the voltage signals are input into the controller and converted into digital quantities d1 and d2.

[0013]

[0014] Where n is the number of sampling bits, V ref is the ADC reference voltage value, V max is the voltage range of the converter output, δ max is the maximum value of the measured displacement; i represents the number of the eddy current sensor, and its values ​​are 1 and 2.

[0015] S2, filtering: Use the moving average filtering method to filter the collected displacement data δ i The signal is filtered to remove interference signals.

[0016]

[0017] Where M is the midpoint of the average value, which is 7. i is the filtered output signal, i.e., the support offset.

[0018] S3, control output: support offset y calculated according to formula (3) i, calculate the number of pulses that need to be sent to the second stepper motor, the formula is as follows:

[0019]

[0020] Where β is the step angle of the stepper motor (in degrees), s is the lead of the thread, λ is the subdivision coefficient of the stepper motor driver, △y i is the specific support offset. At the beginning of cutting, the eddy current displacement sensor is reset to zero, so y i is 0, when the workpiece is deformed, y i >0,△y i =y i -0.

[0021] Another object of the present invention is to use a self-centering double-jaw clamp for turning slender shafts. The self-centering double-jaw clamp is used to clamp the slender shaft workpiece for turning to reduce the bending deformation of the slender shaft workpiece caused by the cutting force.

[0022] Preferably, the aspect ratio of the slender shaft workpiece is: 40<L / D<50, and the length L of the slender shaft workpiece is between 1000mm and 3000mm.

[0023] Compared with the shortcomings and deficiencies of the prior art, the present invention has the following beneficial effects.

[0024] 1. The present invention provides a self-centering double-jaw clamp for turning slender shafts. During the clamping stage, a three-point clamping structure is formed by a clamping wheel and a centering wheel. The double-jaw structure improves the support stiffness for the workpiece shaft, the support and clamping stiffness within a certain range of the cutting tool, and the support stiffness of the workpiece. During the turning stage, the self-centering double-jaw clamp moves with the turning tool, and the position of the centering wheel is fine-tuned through a correction mechanism, thereby reducing the bending deformation of the workpiece shaft caused by the cutting force, which is beneficial to improving the processing quality of the workpiece shaft.

[0025] 2. Both the clamping wheel and the centering wheel are made of high-strength wear-resistant material rings with oblique textures on the surface, which helps to reduce the sliding friction caused by the rotation of the workpiece axis and the axial movement of the self-centering double-jaw clamp with the turning tool.

[0026] 3. The present invention provides a control system for a self-centering double-jaw clamp for turning slender shafts. The eddy current sensor is used to obtain the displacement of the monitoring position. The controller calculates the number of pulses sent to the second stepper motor through the displacement, thereby controlling the second stepper motor to adjust the position of the centering wheel, effectively compensating for or controlling the inconsistency of the deformation of the workpiece shaft.

[0027] 4. The present invention also applies the self-centering double-jaw clamp to turning slender shaft workpieces. In view of the problem that the slender shaft workpiece has a large aspect ratio and poor rigidity during the turning process, the self-centering double-jaw clamp can provide supporting rigidity on the one hand, and on the other hand, can effectively reduce the bending deformation of the slender shaft workpiece during the turning process. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The invention discloses a structural schematic diagram of a self-centering double-jaw clamp for turning a slender shaft.

[0029] Figure 2 It is a structural schematic diagram of the clamping mechanism in the present invention.

[0030] Figure 3 It is a structural schematic diagram of the clamping jaws provided with a vibration reduction damper in the present invention.

[0031] Figure 4 It is a schematic diagram of the connection structure between the power mechanism and the clamping mechanism in the present invention.

[0032] Figure 5 It is a schematic diagram of the connection structure between the correction mechanism and the slide seat in the present invention.

[0033] Figure 6 It is a structural schematic diagram of the measuring mechanism in the present invention.

[0034] Figure 7 It is a schematic diagram of the surface structure of the high-strength wear-resistant material ring in the present invention.

[0035] Figure 8 It is a control flow chart in the present invention.

[0036] In the figure: 100, clamping mechanism; 101, shell; 102, slide seat; 1021, trapezoidal part; 1022, slope; 1023, slide groove; 103, clamping claw; 1031, first end; 1032, second end; 1033, third end; 104, clamping wheel; 1041, high-strength wear-resistant material ring; 105, centering wheel; 106, spring; 107, vibration damper; 108, correction mechanism; 1081, second stepping motor; 1082, second screw; 1083, correction front fork; 200, power mechanism; 201, first stepping motor; 202, first screw; 203, connecting block; 300, measuring mechanism; 301, sensor base; 302, V-shaped pressure block; 303, first eddy current displacement sensor; 304, second eddy current displacement sensor. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0038] Reference Figure 1-Figure 8 The present invention provides a self-centering double-jaw clamp for turning a slender shaft, comprising a clamping mechanism 100 and a power mechanism 200. The clamping mechanism 100 comprises a housing 101, a slide 102 and a clamping jaw 103. The slide 102 has a trapezoidal portion 1021 at one end, the small end surface of the trapezoidal portion 1021 extends to the other end, and a centering wheel 105 is provided at the end. The trapezoidal portion 1021 has symmetrical slopes 1022 on both sides, and the slopes 1022 are provided with slide grooves 1023. The clamping jaws 103 are symmetrically arranged on both sides of the slide 102, and the clamping jaws 103 on both sides form a jaw shape. The shape of the clamping jaw 103 is similar to the shape of the number 3. The clamping jaw 103 has a first end 1031, a second end 1032 and a third end 1033 arranged in sequence, and the first end 1031, the second end 1032 and the third end 1033 are connected by The arched connecting arm is connected, the first end 1031 is provided with a clamping wheel 104, the second end 1032 located in the middle is penetrated by a pin shaft, the second end 1032 is rotatably matched with the pin shaft, both ends of the pin shaft are connected to the shell 101, the third end 1033 is located in the slide groove 1023, and is slidably matched with the slide groove 1023, a spring 106 is provided between the third end 1033 and the slide seat 102, the spring 106 is used to limit the pulling of the third end 1033, so that the slide seat 102 is closely matched with the clamping claw 103 during the push and return process of sliding relative to the shell 101, the slide seat 102 and the clamping claw 103 are partially arranged in the shell 101, the shell 101 is used to limit the support of the slide seat 102 and the clamping claw 103, the shell 101 is slidably connected with the slide seat 102, and two groups of slide seats 102 and clamping claws 103 are arranged in parallel in the shell 101.

[0039] In one embodiment, a vibration damper 107 is disposed at the first end 1031 of the clamping jaw 103 , and the vibration damper 107 is used to reduce the vibration of the clamping wheel 104 .

[0040] In one embodiment, the clamping wheel 104 includes a bearing, which is arranged at the first end 1031 through a support shaft. A high-strength wear-resistant material ring 1041 is provided on the outer side of the bearing. The high-strength wear-resistant material ring 1041 is interference fit with the bearing. The high-strength wear-resistant material ring 1041 is specifically a ring structure made of polytetrafluoroethylene material. The surface of the high-strength wear-resistant material ring 1041 has oblique texture. During the turning process of the workpiece shaft, the self-centering double-jaw clamp can move axially with the turning tool. The self-centering double-jaw clamp not only has radial rotation but also axial movement relative to the workpiece. The oblique texture structure on the surface of the high-strength wear-resistant material ring 1041 is beneficial to reducing the sliding friction in the combined direction of the axial movement and the radial rotation.

[0041] The power mechanism 200 drives the slide 102 to slide relative to the shell 101, and the slope 1022 acts on the third end 1033. The second end 1032 is movably penetrated by a pin shaft, thereby driving the first end 1031 to move, that is, the clamping wheels 104 located at the first ends 1031 on both sides open and close, and cooperate with the centering wheel 105 to clamp the workpiece shaft.

[0042] The power mechanism 200 includes a connecting block 203 and a first stepper motor 201. The connecting block 203 has the same shape and size as the slide 102. The connecting block 203 is located between the two groups of slides 102, and the slide 102 and the connecting block 203 are fixed by a connecting pin. A first screw 202 is provided at the output end of the first stepper motor 201. The first screw 202 passes through the housing 101 and is threadedly connected to the connecting block 203. Under the action of the first stepper motor 201, the two groups of slides 102 are driven to move through the connecting block 203, thereby driving the two groups of clamping wheels 104 to open and close.

[0043] In one embodiment, the clamping mechanism 100 also includes a correction mechanism 108. When clamping the workpiece shaft, the centering wheel 105 cooperates with the clamping jaw 103 to make the axis of the workpiece shaft coincide with the center axis of the machine tool. During the turning process, the correction mechanism 108 is used to fine-tune the centering wheel 105 to correct the deformation of the workpiece shaft. Especially when the workpiece shaft is a slender shaft workpiece, the bending deformation of the slender shaft workpiece caused by the cutting force during the processing can be reduced, thereby achieving the purpose of improving the turning accuracy of the slender shaft workpiece. The correction mechanism 108 is embedded in the slide 102, and includes a correction front fork 1083 and a second stepper motor 1081. The output end of the second stepper motor 1081 is provided with a second screw 1082. The correction front fork 1083 is in a U-shaped structure. The centering wheel 105 is provided at the U-shaped notch at the front end of the correction front fork 1083. The centering wheel 105 is connected to the correction front fork 1083 through a support shaft. The rear end of the correction front fork 1083 is provided with a second threaded hole. The second screw 1082 is threadedly connected to the second threaded hole. The end of the slide 102 located at the centering wheel 105 is provided with a guide groove. The correction front fork 1083 is slidably provided in the guide groove. The second stepper motor 1081 drives the correction front fork 1083 to move through the second screw 1082 to adjust the position of the centering wheel 105. The centering wheel 105 has the same structure as the clamping wheel 104, which will not be described in detail.

[0044] The present invention also provides a control system for a self-centering double-jaw clamp for turning slender shafts, including a measuring mechanism 300 and a controller. The measuring mechanism 300 includes an eddy current displacement sensor, a sensor base 301 and a V-shaped pressure block 302. The sensor base 301 is axially arranged on both sides of a housing 101 along the axis of the clamped workpiece. The eddy current displacement sensor is arranged on the sensor base 301. The V-shaped pressure block 302 is used to fix the eddy current displacement sensor to the sensor base 301.

[0045] The controller is electrically connected to the eddy current displacement sensor, the first stepper motor 201 and the second stepper motor 1081 respectively. The eddy current displacement sensor transmits the detection data to the controller. The controller controls the first stepper motor 201 to push the connecting block 203, thereby driving the two sets of slides 102 to cooperate with the clamping jaws 103, so that the clamping wheel 104 and the centering wheel 105 cooperate to clamp and fix the workpiece shaft. At the same time, in the process of turning the workpiece shaft, the controller controls the second stepper motor 1081 to slightly adjust the position of the centering wheel 105 according to the detection data to reduce the bending deformation of the workpiece shaft caused by the cutting force.

[0046] The controller uses a microcontroller unit (Microcontroller Unit), namely MCU.

[0047] The control method of the control system of the self-centering double-jaw clamp for turning a slender shaft comprises the following steps:

[0048] S1, displacement signal acquisition: The eddy current displacement sensor converts the displacement of the measuring point into a voltage signal and performs signal conditioning. The voltage signal is transmitted to the ADC converter to convert the voltage signal into a digital signal.

[0049] The eddy current displacement sensors on both sides measure the displacements δ1 and δ2 of the left and right positions of the two supports. The displacement signals are converted into voltage signals V1 and V2 by the signal converter, and the voltage signals are input into the controller and converted into digital quantities d1 and d2.

[0050] The eddy current displacement sensor has a built-in ADC converter, which is an analog-to-digital converter. i Value and displacement δ i The relationship is as follows:

[0051]

[0052] Where n is the number of sampling bits, V ref is the ADC reference voltage value. These two values ​​are determined by the ADC performance parameters; V max is the voltage range of the converter output. The converter output voltage used in this design is 0~3.0V, so V max is 3.0, δ max is the maximum value of the measured displacement, which is determined by the eddy current displacement sensor and the ADC converter; i represents the eddy current sensor number, and its values ​​are 1 and 2.

[0053] The controller calculates the actual displacement based on the digital signal.

[0054] From formula (1), we can get the displacement δ measured by the eddy current sensor: i is the digital quantity d to be converted i The relationship is as follows:

[0055]

[0056] S2, filtering: Since there are interference signals in the sensor measurement, the interference signals should be filtered out as much as possible. The moving average filtering method is used to filter the collected displacement data δ i The signal is filtered.

[0057]

[0058] Where M is the midpoint of the average value, which is 7. i is the filtered output signal, i.e., the support offset.

[0059] S3, control output: support offset y calculated according to formula (3) i , calculate the number of pulses that need to be sent to the second stepper motor 1081, the formula is as follows:

[0060]

[0061] Where β is the step angle of the stepper motor (in degrees), s is the lead of the thread, λ is the subdivision coefficient of the stepper motor driver, △y i is the specific support offset. At the beginning of cutting, the eddy current displacement sensor is reset to zero, so y i is 0, when the workpiece is deformed, y i >0,△y i =y i -0.

[0062] The moving range of the centering wheel is controlled within ±5mm.

[0063] The present invention also provides an application of a self-centering double-jaw clamp for turning a slender shaft, and the self-centering double-jaw clamp and the control system are applied to turning a slender shaft workpiece.

[0064] The aspect ratio of the slender shaft workpiece is: 40<L / D<50, and the length L of the slender shaft is between 1000mm and 3000mm.

[0065] In the initial clamping stage of the slender shaft workpiece, the controller drives the first stepper motor 201, and the first stepper motor 201 drives the first screw 202 to rotate, and pushes the slide 102 forward through the connecting block 203. Under the action of the slope 1022 and the slide groove 1023, the jaws 103 on both sides open and then contract, and cooperate with the centering wheel 105 to achieve preliminary clamping of the slender shaft workpiece. The controller resets the measurement values ​​of the first eddy current displacement sensor 303 and the second eddy current displacement sensor 304 on both sides to zero respectively.

[0066] During the turning phase of the slender shaft workpiece, the first eddy current displacement sensor 303 and the second eddy current displacement sensor 304 respectively obtain the displacement values ​​δ of the detection positions on both sides. i (i is the eddy current sensor number), the displacement signal is transmitted to the controller, and after calculation by the controller, the pulse number is sent to the second stepper motor 1081, so as to slightly adjust the centering wheel 105 to offset the deformation of the slender shaft workpiece caused by the cutting force during cutting, which is beneficial to improve the processing accuracy.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A self-centering double-jaw fixture for turning a slender shaft, characterized in that: The invention comprises a clamping mechanism and a power mechanism, wherein the clamping mechanism comprises a shell, a slide seat and a clamping jaw, the slide seat has a trapezoidal portion, and the slope surfaces on both sides of the trapezoidal portion are symmetrically provided with sliding grooves, the clamping jaws are symmetrically arranged on both sides of the slide seat, and the clamping jaws are in a "3"-shaped structure, and the clamping jaws have a first end, a second end and a third end which are arranged in sequence, the first end is provided with a clamping wheel, the second end is penetrated by a pin shaft hinged therewith, both ends of the pin shaft are connected to the shell, the third end is slidably matched with the sliding groove, a spring is arranged between the slide seat and the third end, a centering wheel is arranged on the other end of the slide seat relative to the trapezoidal portion, the centering wheel and the clamping wheels on both sides form a three-point clamping structure, the shell seat is provided with two groups of slide seats at intervals, the slide seat is slidably matched with the shell, the power mechanism is used to drive the slide seat to move, the slide seat is provided with a correction mechanism, and the correction mechanism is used to adjust the position of the centering wheel.

2. The self-centering double-jaw clamp for turning a slender shaft according to claim 1, characterized in that: The correction mechanism includes a second stepper motor and a correction front fork, the second stepper motor is arranged in a slide seat, a second screw is provided at the output end of the second stepper motor, a guide groove is provided at one end of the slide seat located on a centering wheel, the correction front fork is slidably connected to the guide groove, the correction front fork is a U-shaped structure, the centering wheel is arranged in the U-shaped notch of the correction front fork, and the correction front fork is threadedly connected to the second screw.

3. The self-centering double-jaw clamp for turning a slender shaft according to claim 1, characterized in that: The power mechanism includes a first stepper motor and a connecting block, wherein the connecting block is arranged between two groups of slides and connected to the slides on both sides, and a first screw is arranged at the output end of the first stepper motor, and the first screw is threadedly connected to the connecting block.

4. The self-centering double-jaw clamp for turning a slender shaft according to claim 1, characterized in that: The clamping wheel and the centering wheel both include a bearing and a high-strength wear-resistant material ring that is interference-fitted with the bearing.

5. The self-centering double-jaw clamp for turning a slender shaft as claimed in claim 4, characterized in that: The surface of the high-strength wear-resistant material ring is provided with oblique lines.

6. A control system for a self-centering double-jaw clamp for turning a slender shaft, using the self-centering double-jaw clamp according to any one of claims 1 to 5, characterized in that: It includes an eddy current displacement sensor and a controller. The eddy current displacement sensor is arranged on both sides of the shell along the axial direction of the clamped workpiece. The controller is electrically connected to the eddy current sensor, the first stepper motor and the second stepper motor respectively. The eddy current sensor respectively collects the displacement of the detection positions on both sides of the shell. The controller is used to calculate the number of pulses sent to the second stepper motor according to the displacement obtained by the detection. The second stepper motor adjusts the position of the centering wheel according to the number of pulses.

7. The control system of the self-centering double-jaw clamp for turning a slender shaft according to claim 6, characterized in that: The pulse quantity is obtained by the following steps: S1, the eddy current displacement sensors on both sides measure the displacements of two positions δ1 and δ2, the displacement signals are converted into voltage signals V1 and V2 by the signal converter, and the voltage signals are input into the controller and converted into digital quantities d1 and d2. Where n is the number of sampling bits, V ref is the ADC reference voltage value, V max is the voltage range of the converter output, δ max is the maximum value of the measured displacement; i represents the number of the eddy current sensor, and its values ​​are 1 and 2. S2, filtering: Use the moving average filtering method to filter the collected displacement data δ i The signal is filtered to remove interference signals. Where M is the midpoint of the average value, which is 7. i is the filtered output signal, i.e., the support offset. S3, control output: support offset y calculated according to formula (3) i , calculate the number of pulses that need to be sent to the second stepper motor, the formula is as follows: Where β is the step angle of the stepper motor (in degrees), s is the lead of the thread, λ is the subdivision coefficient of the stepper motor driver, △y i is the specific support offset. At the beginning of cutting, the eddy current displacement sensor is reset to zero, so y i is 0, when the workpiece is deformed, y i >0,△y i =y i -0.

8. Application of a self-centering double-jaw clamp for turning a slender shaft, using the self-centering double-jaw clamp described in claims 1 to 5, characterized in that: The self-centering double-jaw clamp is applied to clamping a slender shaft workpiece for turning to reduce the bending deformation of the slender shaft workpiece caused by cutting force.

9. Use of the self-centering double-jaw fixture for turning a slender shaft as claimed in claim 8, characterized in that: The aspect ratio of the slender shaft workpiece is: 40<L / D<50, and the length L of the slender shaft workpiece is between 1000mm and 3000mm.

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