Positioning device for rod end joint measurement and measurement method

Abstract

The invention discloses a positioning device for rod end joint measurement and a measurement method, and belongs to the technical field of measurement, the positioning device comprises a measurement flat plate and a rod end joint, the measurement flat plate is sleeved with a centering shaft, and the top end of the centering shaft extends out of the measurement flat plate and is used for positioning the rod end joint; one side of the measuring flat plate is connected with an adjusting table through a bolt, the adjusting table is provided with a guide shaft capable of moving up and down, the top end of the guide shaft is provided with a V-shaped notch, the positioning of the rod end joint in the circumferential direction is realized through the V-shaped notch in the guide shaft, and the bottom of the centering shaft is sleeved with a base. In the positioning process of the rod end joint, the interference phenomenon in the axial positioning process when the rod end joint is installed is eliminated, the whole process is automatic, human intervention is reduced, and the measurement efficiency is improved.

Description

Technical Field

[0001] The present invention relates to a positioning device and a measurement method for rod end joint measurement, belonging to the technical field of measurement. Background Art

[0002] Rod end spherical plain bearings belong to an important type of spherical plain bearings. The rod end joint is the main part of the rod end spherical plain bearing, with a complex shape, high processing and measurement difficulties, very low measurement efficiency, and it is impossible to ensure the rapid measurement of various parameters during the production of batch products, bringing difficulties to the quality assurance during batch processing of products. The rod end spherical plain bearing includes a rod end joint and an outer joint housing. Among them, the outer joint housing has a relatively regular shape, is easy to process and control dimensional accuracy. The rod end joint is a part that is difficult to process and measure in the rod end spherical plain bearing, and its quality directly determines the final quality of the rod end spherical plain bearing.

[0003] At present, since one end of the rod end joint is a shaft and the other end is a ball head with a hole, there are many parameters that need to be measured and controlled, including various dimensions and geometric tolerances. The measurement of the rod end joint is generally carried out by various different instruments such as a profilometer, a cylindricity meter, a length measuring instrument, and a coordinate measuring machine. Not only is the measurement efficiency extremely low, but also due to multi-reference positioning, the measurement accuracy is seriously affected, and it is more unsuitable for batch measurement of special-shaped parts.

[0004] Deficiencies of the prior art: 1. Traditional measurement relies on multiple devices such as a profilometer and a cylindricity meter, and the measurement efficiency is extremely low; 2. Multi-reference positioning causes interference to the measurement accuracy; 3. Lack of the ability for rapid clamping and adaptive adjustment for special-shaped parts; 4. The manual centering method is prone to introducing human errors and is difficult to meet the requirements of high-precision batch detection. Summary of the Invention

[0005] The purpose of the present invention is to provide a positioning device and a measurement method for rod end joint measurement to solve the problems raised in the above background art.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions: A positioning device for rod end joint measurement includes a measurement flat plate and a rod end joint. A centering shaft is sleeved on the measurement flat plate. The top end of the centering shaft extends out of the measurement flat plate and is used for positioning the rod end joint. One side of the measurement flat plate is connected with an adjustment table by bolts. A vertically movable guide shaft is arranged on the adjustment table. A V-shaped notch is opened at the top end of the guide shaft. The circumferential positioning of the rod end joint is realized through the V-shaped notch on the guide shaft. The bottom of the centering shaft is sleeved with a base.

[0007] Furthermore, the distance between the upper surface of the centering shaft and the upper surface of the measuring flat plate is 2 - 3 mm.

[0008] Furthermore, a plurality of electromagnetic chucks are arranged in the measuring flat plate, and the plurality of electromagnetic chucks are arranged circumferentially on the measuring flat plate.

[0009] Furthermore, a positioning screw is threadedly connected to the base, and the centering shaft is fixed by rotating the positioning screw to squeeze the centering shaft.

[0010] Furthermore, the base is fixed to the granite measuring table of the coordinate measuring machine through the flange and bolts at the bottom.

[0011] Furthermore, a stepped through hole penetrating up and down is formed in the adjusting table, the guide shaft is located in the stepped through hole, and a compression spring is arranged between the bottom of the inner wall of the stepped through hole and the guide shaft.

[0012] Furthermore, the centering shaft has a shaft shoulder, and the measuring flat plate is centered and positioned through the shaft shoulder of the centering shaft, and an interference fit is provided between the centering shaft and the measuring flat plate.

[0013] A measuring method based on a positioning device for rod end joint measurement, the specific steps include: Fix the base on the granite working table of the coordinate measuring machine through the flange and bolts, and then place the rod end joint on the measuring flat plate; One end of the rod end joint is centered by the protruding shaft end of the centering shaft, and the other end of the rod end joint is placed on the top of the guide shaft. The rod end joint is positioned in the circumferential direction under the cooperation of gravity and the V-shaped notch, ensuring that there is no interference with the full contact between the lower end face of the rod end joint and the upper end face of the measuring flat plate; Determine the coordinate system, and through programming, measure the radius of the ball head generatrix, hole diameter, outer diameter of the ball head, shaft end diameter, width of both end faces, distance between the hole and the shaft end, symmetry between the ball head and both end faces, perpendicularity of the hole to both end faces, dimensional and geometric tolerances of the rod end joint; After replacing the workpiece, quickly position the rod end joint with the coordinate system unchanged, thereby realizing the quick positioning of complex workpieces and the quick and precise measurement of parameters; After measuring the rod end joint multiple times, according to the measurement results, establish a quality prediction model through the automatic calibration algorithm of the three-coordinate system, and use the automatic calibration algorithm of the three-coordinate system to automatically adjust the coordinate system to ensure the accuracy of the measurement data.

[0014] Furthermore, the automatic calibration algorithm of the three-coordinate system can be automatically started according to time or the number of measurements. By arranging multiple calibration points in the measurement space of the rod end joint and measuring the above-mentioned multiple calibration points, and according to the difference between the measurement results and the preset standard values, automatically adjust the coordinate system using the coordinate transformation algorithm to ensure the accuracy of the measurement data.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: The centering of the rod end joint is achieved through the centering shaft, the axial positioning of the rod end joint is realized through the end face of the measuring flat plate, the automatic circumferential positioning of the rod end joint is achieved through the guide shaft, the quick adsorption of the rod end joint is realized through the electromagnetic chuck, and the interference phenomenon during the axial positioning during the installation of the rod end joint is eliminated through the precise movement and flexible rotation of the elastic device composed of the compression spring and the guide shaft in the adjustment table hole; By precisely adjusting the magnetic disk adsorption force according to the rod end joints of different materials and weights, it not only ensures that the rod end joints are stably adsorbed on the measuring flat plate, but also avoids the difficulty of removing the workpiece during measurement or damage to the workpiece caused by excessive adsorption force; By establishing a quality prediction model, a more comprehensive basis is provided for product quality assessment, and the coordinate transformation algorithm is used to automatically adjust the coordinate system to ensure the accuracy of measurement data; The single-piece measurement time is shortened from 15 minutes in the traditional method to within 2 minutes, and the batch detection efficiency is increased by 6 times; The repeat positioning accuracy reaches ±2μm, and the measurement uncertainty of geometric tolerance is reduced to 1 / 3 of the original method; Through the magnetic suction adjustment and fine-tuning mechanism, rod end joints with diameters of φ8 - φ30mm and lengths of 20 - 80mm are compatible; The full-process automation reduces human intervention, and the traceability of measurement data complies with the ISO / IEC 17025 standard. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on the structures shown in these drawings without creative efforts.

[0017] Figure 1 It is a schematic structural diagram of the whole of the present invention; Figure 2 It is a sectional view of the whole structure of the present invention; Figure 3 It is a schematic structural diagram of the measuring flat plate of the present invention; Figure 4 It is a schematic structural diagram of the centering shaft of the present invention; Figure 5 It is a schematic structural diagram of the adjustment table of the present invention; Figure 6 It is a schematic structural diagram of the base of the present invention; Figure 7Front view of the structure of the rod end joint of the present invention; Figure 8 Top view of the structure of the rod end joint of the present invention.

[0018] In the figure: 1, measuring flat plate; 2, centering shaft; 3, adjustment table; 4, guide shaft; 5, rod end joint; 6, compression spring; 7, base; 8, electromagnetic chuck; 9, positioning screw. Specific implementation manner

[0019] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0020] Please refer to Figures 1-8 , the present invention provides a technical solution: As Figure 1 and Figure 2 shown, a positioning device for measuring a rod end joint includes a measuring flat plate 1 and a rod end joint 5. A centering shaft 2 is sleeved on the measuring flat plate 1. The top end of the centering shaft 2 extends out of the measuring flat plate 1 and is used to position the rod end joint 5. One side of the measuring flat plate 1 is connected with an adjustment table 3 by bolts. A vertically movable guide shaft 4 is arranged on the adjustment table 3. A V-shaped notch is opened at the top end of the guide shaft 4. The circumferential positioning of the rod end joint 5 is realized through the V-shaped notch on the guide shaft 4. The bottom of the centering shaft 2 is sleeved with a base 7.

[0021] Among them, one side of the measuring flat plate 1 has a planar structure. The planar structure of the measuring flat plate 1 is connected with the adjustment table 3 by bolts. The upper end face of the measuring flat plate 1 requires high flatness. During measurement, the lower end face of the rod end joint 5 is placed on the upper end face of the measuring flat plate 1 and centered by the protruding shaft end of the centering shaft 2. The other end of the rod end joint 5 is placed in the V-shaped notch at the upper end of the guide shaft 4, realizing the circumferential positioning of the rod end joint 5, and ensuring that there is no interference between the lower end face of the hole end of the rod end joint 5 and the upper end face of the measuring flat plate 1 for full contact.

[0022] When measuring the first rod end joint 5, the positioning device for measuring the rod end joint is fixed on the granite workbench of the coordinate measuring instrument, and the rod end joint 5 is quickly positioned to determine the coordinate system. Through programming, after replacing the workpiece, the rod end joint 5 is quickly positioned through the measuring flat plate 1, the centering shaft 2, and the guide shaft 4, and the coordinate system remains unchanged, thereby realizing the quick positioning of complex workpieces and the quick and precise measurement of various parameters.

[0023] Further, the distance between the upper surface of the centering shaft 2 and the upper surface of the measuring flat plate 1 is 2 - 3 mm. The measuring flat plate 1 has a hole corresponding to the centering shaft 2, and the central axis of the hole on the measuring flat plate 1 is perpendicular to the upper and lower surfaces of the measuring flat plate 1.

[0024] As Figure 3 shown, a number of counterbores are provided on the measuring flat plate 1, and electromagnetic chucks 8 are arranged in the counterbores of the measuring flat plate 1. The several electromagnetic chucks 8 are circumferentially arranged on the measuring flat plate 1. The number of the electromagnetic chucks 8 is 6. The upper end surface of the electromagnetic chuck 8 is slightly lower than the upper end surface of the measuring flat plate 1. The electromagnetic chuck 8 can generate a suction force on the rod end joint 5. Under the action of the suction force of the electromagnetic chuck 8 and the self-gravity of the rod end joint 5, rapid positioning of the rod end joint 5 in the circumferential direction can be achieved. For rod end joints 5 of different materials and weights, the electromagnetic chuck 8 can accurately adjust the disk adsorption force according to the actual situation, which not only ensures that the rod end joint 5 is stably adsorbed on the measuring flat plate 1, but also avoids difficulty in removing the workpiece during measurement or damage to the workpiece due to excessive adsorption force.

[0025] As Figure 6 shown, screw holes are provided on the base 7. The base 7 is threadedly connected with positioning screws 9 through the screw holes. The centering shaft 2 is fixed by squeezing the centering shaft 2 by rotating the positioning screws 9. A V-shaped groove is provided at the lower end of the centering shaft 2, and the V-shaped groove on the centering shaft 2 is aligned with the screw hole on the base 7.

[0026] Further, the bottom of the base 7 is a flange. The base 7 is fixed to the granite measuring table of the coordinate measuring machine through the flange at the bottom and bolts, ensuring rapid and accurate positioning of the rod end joint 5 when batch measuring the rod end joint 5 on the coordinate measuring machine.

[0027] As Figure 5 shown, a stepped through hole penetrating up and down is provided on the adjustment table 3. The central axis of the stepped through hole is parallel to the central axis of the hole on the measuring flat plate 1. The guide shaft 4 is located in the stepped through hole. The cross-section of the guide shaft 4 is in a T-shaped structure. The cylindrical part of the guide shaft 4 corresponds to the small hole of the stepped through hole, so that the guide shaft 4 can move precisely along the axial direction. A compression spring 6 is provided between the bottom of the inner wall of the stepped through hole and the guide shaft 4.

[0028] As Figure 4 shown, the centering shaft 2 has a shaft shoulder. The cross-section of the centering shaft 2 is in a middle-character structure. The measuring flat plate 1 is centered and positioned through the shaft shoulder of the centering shaft 2, and an interference fit is provided between the centering shaft 2 and the measuring flat plate 1.

[0029] A measuring method based on a positioning device for rod end joint measurement, the specific steps include: Fix the base 7 on the granite workbench of the coordinate measuring machine through the flange and bolts, and then place the rod end joint 5 on the measuring flat plate 1; One end of the rod end joint 5 is centered by the protruding shaft end of the centering shaft 2, and the other end of the rod end joint 5 is placed on the top of the guide shaft 4. Under the action of gravity and the cooperation of the V-shaped notch, the circumferential positioning of the rod end joint 5 is realized, ensuring that there is no interference with the full contact between the lower end surface of the rod end joint 5 and the upper end surface of the measuring flat plate 1; Determine the coordinate system. Through programming, measure the spherical head bus radius, aperture, spherical head outer diameter, shaft end diameter, widths of both end faces, distance between the hole and the shaft end, symmetry between the spherical head and both end faces, perpendicularity between the hole and both end faces, dimensional and geometric tolerances of the rod end joint 5; After replacing the workpiece, quickly position the rod end joint 5 with the coordinate system unchanged, thereby realizing the quick positioning of complex workpieces and the quick and precise measurement of various parameters; After measuring the rod end joint 5 multiple times, according to the measurement results, establish a quality prediction model through the three-coordinate system automatic calibration algorithm, and use the three-coordinate system automatic calibration algorithm to automatically adjust the coordinate system to ensure the accuracy of the measurement data.

[0030] As Figure 7 and Figure 8 shown, by adopting this positioning device in cooperation with the coordinate measuring machine, the omnidirectional measurement of the rod end joint 5 can be realized. The rod end joint 5 is the workpiece to be measured and is a special-shaped part. When measuring the rod end joint 5, the points to be measured include: one end of the rod end joint 5 is a shaft with an H plane and a G plane at the shaft end, the other end of the rod end joint 5 is a disc-shaped part, the side surface of the disc is an arc-shaped B plane, the other end has a hole perpendicular to the shaft, the inner wall of the hole is a D plane, the upper and lower ends of the hole are flat surfaces which are A plane and C plane respectively, the E plane in the transition interval between the shaft and the disc-shaped part, the F plane in the transition interval between the shaft end groove and the outer peripheral surface of the shaft. The data to be measured include: the spherical head bus radius R1, aperture D3, spherical head outer diameter D2 of the rod end joint 5, shaft end diameter D1, widths of both end faces L5, distance L1 between the hole and the G plane of the shaft end, symmetry between the spherical head and both end faces, perpendicularity between the hole and both end faces, dimensional and geometric tolerances, as well as the radius R2 at the connection of both ends of the rod end joint 5, the radius R3 of the shaft end groove, the distance L2 from the midpoint of the shaft end groove to the center of the hole, the distance L3 from the connection of the hole end to the center of the hole, and the distance L4 between the upper end surface of the hole end and the center of the connection of both ends.

[0031] It should be noted that when measuring the rod end joint 5 using the existing technology, due to the influence of the clamping tooling itself, it is impossible to achieve a full range of measurements of the rod end joint 5. The type of the clamping tooling needs to be replaced. Each time the clamping tooling is replaced on the coordinate measuring machine, repositioning is required, which also wastes a lot of time. When measuring the rod end joint 5, it is usually necessary to measure multiple batches of rod end joints 5. Therefore, overall, the measurement cycle is relatively long. By using this positioning device, the single-piece measurement time of the rod end joint 5 is shortened from 15 minutes by the traditional method to within 2 minutes, the batch detection efficiency is increased by 6 times, the repeat positioning accuracy reaches ±2μm, the measurement uncertainty of geometric tolerances is reduced to 1 / 3 of the original method, and the full process automation reduces human intervention. The traceability of measurement data complies with the ISO / IEC 17025 standard.

[0032] The coordinate system automatic calibration algorithm of the precision positioning device for multi-parameter rapid measurement on a coordinate measuring machine is an algorithm developed specifically on the coordinate measuring machine and is included in the dedicated measurement data analysis software. During batch measurement, the coordinate system may deviate. The software automatically starts the coordinate system automatic calibration algorithm according to requirements based on time or the number of measurements. By arranging multiple calibration points in the measurement space of the rod end joint 5, the measuring machine measures the multiple calibration points. The software automatically adjusts the coordinate system using the coordinate transformation algorithm according to the difference between the measurement results and the preset standard values to ensure the accuracy of the measurement data, without the need for manual frequent re-calibration of the coordinate system, improving the stability and continuity of the measurement.

[0033] After the coordinate measuring machine obtains the measurement data of the rod end joint 5, the software uses statistical methods and machine learning algorithms to deeply analyze the data. It can not only quickly calculate the radius of the ball head bus, the conventional dimensions of the hole diameter, and geometric tolerances, but also establish a quality prediction model to predict the performance change trend of the rod end joint 5 during subsequent use based on multiple groups of measurement data, providing a more comprehensive basis for product quality assessment.

[0034] Among them, the statistical methods and machine learning algorithms include random forest, which consists of multiple decision trees. The decision tree constructs a tree structure by splitting features.

[0035] For regression problems, the predicted value of the random forest is the average of the predicted values of all decision trees; For classification problems, the predicted value is the result of the majority vote of the decision trees.

[0036] In practical applications, the above algorithms will be optimized and combined according to specific requirements and data characteristics to improve the accuracy of analysis and prediction.

[0037] The following are the core algorithms and corresponding formulas: Dimension calculation Calculation of the radius of the spherical head generatrix: The least squares method is often used to fit the spherical surface equation.

[0038] Let the spherical surface equation be ,

[0039] For the measurement points ( , , ), by minimizing the error function ,

[0040] Solve for the parameter center coordinates of the sphere , , and the radius of the spherical surface .

[0041] Aperture calculation: For the measured data of the hole wall points, a circle fitting algorithm can be used, such as the least squares method to fit the circle equation

[0042] Similarly, the center coordinates ([[]] , ) and the radius are obtained by minimizing the error function.

[0043] Geometric tolerance calculation Roundness error: Based on the minimum zone method, find two concentric circles that enclose the actual circle and have the smallest radius difference. The radius difference is the roundness error. During the calculation, the circle contour data can be transformed to the frequency domain for analysis through Fourier transform, and the error can be calculated after extracting the shape features.

[0044] Cylindricity error: Divide the cylindrical surface into multiple cross-sections, calculate the roundness error of each cross-section, and then comprehensively evaluate the cylindricity error in combination with the positional relationship between the cross-sections. The least squares method or the minimum zone method is commonly used for the calculation.

[0045] Quality prediction model Linear regression: If it is assumed that the quality index is linearly related to multiple dimensional and geometric tolerance features , ,..., , the model formula is ,

[0046] where is the regression coefficient, is the error term. Estimate the regression coefficient by the least squares method to minimize the sum of the squared errors between the actual value and the predicted value .

[0047] Support Vector Machine (SVM): For binary classification problems, find the optimal hyperplane in the feature space , and maximize the margin between the samples and the hyperplane.

[0048] Introduce the kernel function which can handle non - linear problems, and the decision function is ,

[0049] where are Lagrange multipliers.

[0050] Random Forest: Composed of multiple decision trees. The decision trees build the tree structure by splitting features. For regression problems, the predicted value of the random forest is the average of the predicted values of all decision trees; for classification problems, the predicted value is the result of the majority vote of the decision trees.

[0051] In practical applications, according to specific requirements and data characteristics, the above algorithms will be optimized and combined to improve the accuracy of analysis and prediction.

[0052] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A positioning device for rod end joint measurement, characterized in that, It includes a measuring flat plate and a rod end joint. A centering shaft is sleeved on the measuring flat plate. The top end of the centering shaft extends out of the measuring flat plate and is used to position the rod end joint. One side of the measuring flat plate is connected with an adjusting table through bolts. A vertically movable guide shaft is arranged on the adjusting table. A V-shaped notch is opened at the top end of the guide shaft. The circumferential positioning of the rod end joint is realized through the V-shaped notch on the guide shaft. The bottom of the centering shaft is sleeved with a base.

2. The positioning device for rod end joint measurement according to claim 1, characterized in that, The distance between the upper surface of the centering shaft and the upper surface of the measuring flat plate is 2 - 3 mm.

3. The positioning device for rod end joint measurement according to claim 1, characterized in that, A plurality of electromagnetic chucks are arranged in the measuring flat plate, and the plurality of electromagnetic chucks are arranged circumferentially on the measuring flat plate.

4. The positioning device for rod end joint measurement according to claim 1, characterized in that, A positioning screw is threadedly connected to the base. The centering shaft is fixed by rotating the positioning screw to squeeze the centering shaft.

5. A positioning device for rod end joint measurement according to claim 1, characterized in that, The base is fixed to the granite measuring table of the coordinate measuring machine through the flange and bolts at the bottom.

6. The positioning device for rod end joint measurement according to claim 1, characterized in that, A stepped through hole penetrating up and down is opened on the adjusting table. The guide shaft is located in the stepped through hole. A compression spring is arranged between the bottom of the inner wall of the stepped through hole and the guide shaft.

7. The positioning device for rod end joint measurement according to claim 1, wherein, The centering shaft has a shaft shoulder. The measuring flat plate is centered and positioned through the shaft shoulder of the centering shaft. The centering shaft and the measuring flat plate are in interference fit.

8. A measuring method for a positioning device for rod end joint measurement according to any one of claims 1-7, characterized in that, The specific steps include: Fix the base on the granite working table of the coordinate measuring machine through the flange and bolts, and then place the rod end joint on the measuring flat plate; One end of the rod end joint is centered by the protruding shaft end of the centering shaft. The other end of the rod end joint is placed on the top of the guide shaft. The circumferential positioning of the rod end joint is realized under the cooperation of gravity and the V-shaped notch, ensuring that there is no interference between the lower end face of the rod end joint and the upper end face of the measuring flat plate and ensuring full contact. Determine the coordinate system. Through programming, measure the radius of the ball head generatrix, hole diameter, outer diameter of the ball head, shaft end diameter, width of both end faces, distance between the hole and the shaft end, symmetry between the ball head and both end faces, perpendicularity between the hole and both end faces, dimensional and geometric tolerances of the rod end joint. After replacing the workpiece, quickly position the rod end joint with the coordinate system unchanged, thereby realizing the quick positioning of complex workpieces and the quick and precise measurement of parameters. After measuring the rod end joint multiple times, according to the measurement results, establish a quality prediction model through the automatic calibration algorithm of the three-coordinate system, and use the automatic calibration algorithm of the three-coordinate system to automatically adjust the coordinate system to ensure the accuracy of the measurement data.

9. The measuring method of a positioning device for rod end joint measurement according to claim 8, characterized in that The automatic calibration algorithm of the three-coordinate system can be automatically started according to time or the number of measurements. By arranging multiple calibration points in the measurement space of the rod end joint and measuring the above-mentioned multiple calibration points, and according to the difference between the measurement results and the preset standard values, automatically adjust the coordinate system using the coordinate transformation algorithm to ensure the accuracy of the measurement data.

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