Positioning device and measurement method for rod end joint measurement

Abstract

The present invention discloses a positioning device and method for measuring rod end joints, belonging to the field of measurement technology. The device includes a measuring plate and a rod end joint. The measuring plate is provided with a centering shaft, the top end of which extends out of the measuring plate and is used to position the rod end joint. An adjustment platform is bolted to one side of the measuring plate, and a guide shaft that can move up and down is provided on the adjustment platform. The top end of the guide shaft has a V-shaped notch, and the V-shaped notch on the guide shaft is used to position the rod end joint in the circumferential direction. A base is sleeved on the bottom of the centering shaft. During the positioning of the rod end joint, interference during axial positioning during installation of the rod end joint is eliminated. The full process automation reduces human intervention and improves measurement efficiency.

Description

Technical Field

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

[0002] Rod ends are an important type of spherical plain bearing. The rod end joint, the primary component, is complex in shape, making machining and measurement challenging. This results in low measurement efficiency, making it difficult to quickly measure multiple parameters during mass production. This poses a challenge to quality assurance during mass production. Rod ends consist of the rod end joint and the outer sleeve. The outer sleeve has a more regular shape, making it easier to machine and maintain dimensional accuracy. However, the rod end joint is the most difficult component to machine and measure, and its quality directly determines the ultimate quality of the rod end.

[0003] At present, because the rod end joint has a shaft at one end and a ball head with a hole at the other end, many parameters need to be measured and controlled, including various dimensions and form and position tolerances. The measurement of rod end joints is generally carried out using various different instruments such as profilometers, cylindricimeters, length gauges and three-coordinate measuring machines. Not only is the measurement efficiency extremely low, but the positioning due to multiple references seriously affects the measurement accuracy. It is also not suitable for batch measurement of special-shaped parts.

[0004] Deficiencies of existing technology:

[0005] 1. Traditional measurement relies on multiple devices such as profilometers and cylindricity meters, resulting in extremely low measurement efficiency.

[0006] 2. Multi-reference positioning causes interference with measurement accuracy;

[0007] 3. Lack of rapid clamping and adaptive adjustment capabilities for special-shaped parts;

[0008] 4. Manual centering is prone to human error and is difficult to meet the needs of high-precision batch testing. Summary of the Invention

[0009] The object of the present invention is to provide a positioning device and a measuring method for measuring a rod end joint, so as to solve the problems raised in the above background technology.

[0010] In order to achieve the above object, the present invention adopts the following technical solutions:

[0011] A positioning device for measuring a rod end joint comprises a measuring plate and a rod end joint, wherein a centering shaft is sleeved on the measuring plate, the top end of the centering shaft extends out of the measuring plate and is used to position the rod end joint, an adjustment platform is connected to one side of the measuring plate by bolts, and a guide shaft that can move up and down is provided on the adjustment platform, the top end of the guide shaft is provided with a V-shaped notch, and the V-shaped notch on the guide shaft is used to achieve the positioning of the rod end joint in the circumferential direction, and the bottom of the centering shaft is sleeved with a base.

[0012] Furthermore, the distance between the upper surface of the centering shaft and the upper surface of the measuring plate is 2-3 mm.

[0013] Furthermore, a plurality of electromagnetic chucks are provided in the measuring plate, and the plurality of electromagnetic chucks are arranged circumferentially on the measuring plate.

[0014] Furthermore, a positioning screw is threadedly connected to the base, and the centering shaft is fixed by squeezing the centering shaft by rotating the positioning screw.

[0015] Furthermore, the base is fixed to the granite measuring table of the three-coordinate measuring machine through the flange and bolts at the bottom.

[0016] Furthermore, a stepped through hole is provided on the adjustment platform and passes through the adjustment platform from top to bottom. The guide shaft is located in the stepped through hole. A compression spring is provided between the bottom of the inner wall of the stepped through hole and the guide shaft.

[0017] Furthermore, the centering shaft has a shoulder, and the measuring plate is centered and positioned via the shoulder of the centering shaft, and there is an interference fit between the centering shaft and the measuring plate.

[0018] A measurement method based on a positioning device for measuring a rod end joint comprises the following steps:

[0019] Fix the base to the granite table of the coordinate measuring machine through flanges and bolts, and then place the rod end joint on the measuring plate;

[0020] 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 positioning of the rod end joint in the circumferential direction is achieved under the cooperation of gravity and the V-shaped notch, ensuring full contact between the lower end face of the rod end joint and the upper end face of the measuring plate without interference;

[0021] Determine the coordinate system and, through programming, measure the ball head generatrix radius, hole diameter, ball head outer diameter, shaft end diameter, end face width, hole-shaft end distance, symmetry between the ball head and end faces, perpendicularity between the hole and end faces, and form and position tolerances of the rod end joint;

[0022] After the workpiece is replaced, the rod end joint can be quickly positioned without changing the coordinate system, thus achieving rapid positioning of complex workpieces and rapid and precise measurement of parameters;

[0023] After measuring the rod end joints multiple times, a quality prediction model is established based on the measurement results through the three-coordinate system automatic calibration algorithm, and the coordinate system is automatically adjusted using the three-coordinate system automatic calibration algorithm to ensure the accuracy of the measurement data.

[0024] Furthermore, the three-coordinate system automatic calibration algorithm 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 multiple calibration points, the coordinate system is automatically adjusted 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.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The centering shaft is used to center the rod end joint, the end surface of the measuring plate is used to achieve axial positioning of the rod end joint, the guide shaft is used to achieve automatic circumferential positioning of the rod end joint, and the electromagnetic chuck is used to achieve rapid adsorption of the rod end joint. The elastic device composed of the compression spring and the guide shaft can move precisely and flexibly rotate in the adjustment table hole to eliminate interference during axial positioning during installation of the rod end joint.

[0027] By precisely adjusting the magnetic disk adsorption force according to the different materials and weights of the rod end joints, it ensures that the rod end joints are stably adsorbed on the measuring plate, while avoiding the difficulty of removing the workpiece or damage to the workpiece due to excessive adsorption force during measurement;

[0028] By establishing a quality prediction model, a more comprehensive basis is provided for product quality assessment, and the coordinate system is automatically adjusted using a coordinate transformation algorithm to ensure the accuracy of the measurement data;

[0029] The single-piece measurement time is shortened from 15 minutes using traditional methods to less than 2 minutes, and batch inspection efficiency is increased by 6 times;

[0030] The repeatability accuracy reaches ±2μm, and the uncertainty of form and position tolerance measurement is reduced to 1 / 3 of the original method;

[0031] Through magnetic force adjustment and fine-tuning mechanism, it is compatible with rod end joints with diameters of φ8-φ30mm and lengths of 20-80mm;

[0032] Full process automation reduces human intervention, and measurement data traceability complies with ISO / IEC 17025 standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0034] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0035] Figure 2 It is a cross-sectional view of the overall structure of the present invention;

[0036] Figure 3 It is a schematic structural diagram of the measuring plate of the present invention;

[0037] Figure 4 It is a structural schematic diagram of the centering shaft of the present invention;

[0038] Figure 5 It is a structural schematic diagram of the adjustment platform of the present invention;

[0039] Figure 6 It is a structural schematic diagram of the base of the present invention;

[0040] Figure 7 It is a front view of the structure of the rod end joint of the present invention;

[0041] Figure 8 It is a top view of the structure of the rod end joint of the present invention.

[0042] In the figure: 1. Measuring 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. DETAILED DESCRIPTION

[0043] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0044] See also Figures 1-8 , the present invention provides a technical solution:

[0045] like Figure 1 and Figure 2As shown, a positioning device for measuring a rod end joint includes a measuring plate 1 and a rod end joint 5. A centering shaft 2 is sleeved on the measuring plate 1. The top end of the centering shaft 2 extends out of the measuring plate 1 and is used to position the rod end joint 5. An adjustment platform 3 is connected to one side of the measuring plate 1 by bolts. A guide shaft 4 that can move up and down is provided on the adjustment platform 3. The top end of the guide shaft 4 is provided with a V-shaped notch. The V-shaped notch on the guide shaft 4 is used to achieve the positioning of the rod end joint 5 in the circumferential direction. A base 7 is sleeved on the bottom of the centering shaft 2.

[0046] Among them, one side of the measuring plate 1 is a planar structure, and the planar structure of the measuring plate 1 is connected to the adjustment platform 3 by bolts. The upper end surface of the measuring plate 1 is required to have high flatness. When measuring, the lower end surface of the rod end joint 5 is placed on the upper end surface of the measuring plate 1. The centering is carried out through 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 to realize the positioning of the rod end joint 5 in the circumferential direction, which can ensure that the lower end surface of the hole end of the non-interference rod end joint 5 is in full contact with the upper end surface of the measuring plate 1.

[0047] 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 three-dimensional coordinate measuring machine, and the rod end joint 5 is quickly positioned to determine the coordinate system. Through programming, after the workpiece is replaced, the rod end joint 5 is quickly positioned through the measuring plate 1, centering shaft 2, and guide shaft 4. The coordinate system remains unchanged, thereby realizing rapid positioning of complex workpieces and rapid and precise measurement of various parameters.

[0048] Furthermore, the distance between the upper surface of the centering shaft 2 and the upper surface of the measuring plate 1 is 2-3 mm. The measuring plate 1 has a hole corresponding to the centering shaft 2 , and the central axis of the hole on the measuring plate 1 is perpendicular to the upper and lower surfaces of the measuring plate 1 .

[0049] like Figure 3 As shown, the measuring plate 1 is provided with a plurality of countersunk holes, and electromagnetic suction cups 8 are provided in the countersunk holes of the measuring plate 1. The plurality of electromagnetic suction cups 8 are arranged circumferentially on the measuring plate 1. There are 6 electromagnetic suction cups 8, and the upper end surface of the electromagnetic suction cup 8 is slightly lower than the upper end surface of the measuring plate 1. The electromagnetic suction cup 8 can generate suction on the rod end joint 5. Under the suction effect of the electromagnetic suction cup 8 and the gravity of the rod end joint 5 itself, the rod end joint 5 can be quickly positioned in the circumferential direction. For rod end joints 5 of different materials and weights, the electromagnetic suction cup 8 can accurately adjust the magnetic disk adsorption force according to actual conditions, thereby ensuring that the rod end joint 5 is stably adsorbed on the measuring plate 1, and avoiding difficulty in removing the workpiece or damage to the workpiece during measurement due to excessive adsorption force.

[0050] like Figure 6As shown, a screw hole is provided on the base 7, and a positioning screw 9 is threadedly connected to the base 7 through the screw hole. The centering shaft 2 is fixed by squeezing the centering shaft 2 by rotating the positioning screw 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.

[0051] Furthermore, the bottom of the base 7 is a flange, and the base 7 is fixed to the granite measuring table of the three-dimensional coordinate measuring machine through the bottom flange and bolts, ensuring that the rod end joints 5 can be quickly and accurately positioned when the rod end joints 5 are measured in batches on the three-dimensional coordinate measuring machine.

[0052] like Figure 5 As shown, a stepped through hole is provided on the adjustment table 3, which runs through the adjustment table 3 from top to bottom. The central axis of the stepped through hole is parallel to the central axis of the hole on the measuring plate 1. The guide shaft 4 is located in the stepped through hole. The cross section of the guide shaft 4 is T-shaped. The cylindrical portion of the guide shaft 4 corresponds to the small hole of the stepped through hole, so that the guide shaft 4 can move precisely in 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.

[0053] like Figure 4 As shown, the centering shaft 2 has a shoulder, and the cross section of the centering shaft 2 is in a Chinese-shaped structure. The measuring plate 1 is centered and positioned by the shoulder of the centering shaft 2, and the centering shaft 2 and the measuring plate 1 are interference fit.

[0054] A measurement method based on a positioning device for measuring a rod end joint comprises the following steps:

[0055] Fix the base 7 to the granite table of the coordinate measuring machine through flanges and bolts, and then place the rod end joint 5 on the measuring plate 1;

[0056] One end of the rod end joint 5 is centered by the protruding 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. The positioning of the rod end joint 5 in the circumferential direction is achieved under the cooperation of gravity and the V-shaped notch, ensuring that the lower end surface of the rod end joint 5 and the upper end surface of the measuring plate 1 are fully contacted without interference;

[0057] Determine the coordinate system and, through programming, measure the ball head generatrix radius, hole diameter, ball head outer diameter, shaft end diameter, end face width, hole-to-shaft end distance, symmetry between the ball head and end faces, perpendicularity between the hole and end faces, and form and position tolerances of the rod end joint 5;

[0058] After the workpiece is replaced, the rod end joint 5 is quickly positioned without changing the coordinate system, thereby achieving rapid positioning of complex workpieces and rapid and precise measurement of various parameters;

[0059] After measuring the rod end joint 5 multiple times, a quality prediction model is established based on the measurement results through the three-coordinate system automatic calibration algorithm, and the coordinate system is automatically adjusted using the three-coordinate system automatic calibration algorithm to ensure the accuracy of the measurement data.

[0060] like Figure 7 and Figure 8 As shown, by using the positioning device in conjunction with the three-coordinate measuring machine, all-round measurement of the rod end joint 5 can be achieved. The rod end joint 5 is the workpiece to be measured, which is a special-shaped part. When measuring the rod end joint 5, the points that need to be measured include: one end of the rod end joint 5 is the shaft with an H surface and a G surface at the shaft end, the other end of the rod end joint 5 is a disc-shaped part, the side of the disc is an arc-shaped surface B surface, and the other end has a hole perpendicular to the shaft, the inner wall of the hole is the D surface, the upper and lower ends of the hole are flat surfaces respectively A surface and C surface, the E surface of the transition area between the shaft and the disc-shaped part, the shaft end groove and the outer peripheral surface of the shaft The data that need to be measured for the F surface of the transition interval include: the ball head generatrix radius R1 of the rod end joint 5, the hole diameter D3, the ball head outer diameter D2, the shaft end diameter D1, the two end surface width L5, the distance L1 between the hole and the shaft end G surface, the symmetry between the ball head and the two end surfaces, the perpendicularity size and form and position tolerances between the hole and the two end surfaces, as well as the radius R2 of the connection at both ends of the rod end joint 5, the radius R3 of the shaft end groove, the distance L2 from the middle point of the shaft end groove to the center of the hole, the distance L3 from the hole end connection 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 at both ends.

[0061] It should be noted that when measuring the rod end joint 5 using the existing technology, it is impossible to achieve full-scale measurement of the rod end joint 5 due to the influence of the holding fixture itself. The type of clamping fixture needs to be replaced. Each time the clamping fixture is replaced on the three-dimensional coordinate measuring machine, it needs to be repositioned, which will also waste 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, the overall measurement cycle is longer. By adopting this positioning device, the measurement time of a single rod end joint 5 is shortened from 15 minutes of the traditional method to within 2 minutes, the batch inspection efficiency is increased by 6 times, the repeated positioning accuracy reaches ±2μm, and the measurement uncertainty of the form and position tolerance is reduced to 1 / 3 of the original method. The full process automation reduces human intervention, and the traceability of the measurement data complies with the ISO / IEC 17025 standard.

[0062] The coordinate system automatic calibration algorithm of the precision positioning device for rapid three-coordinate multi-parameter measurement is an algorithm developed specifically for the three-coordinate measuring instrument and 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 based on the time or number of measurements as required. By arranging multiple calibration points in the measurement space of the rod end joint 5, the measuring instrument measures the multiple calibration points. According to the difference between the measurement results and the preset standard values, the software automatically adjusts the coordinate system using the coordinate transformation algorithm to ensure the accuracy of the measurement data. There is no need for frequent manual recalibration of the coordinate system, which improves the stability and continuity of the measurement.

[0063] After the three-coordinate measuring machine obtains the measurement data of the rod end joint 5, the software uses statistical methods and machine learning algorithms to conduct an in-depth analysis of the data. It can not only quickly calculate the ball head main line radius, conventional hole diameter dimensions and form and position tolerances, but also establish a quality prediction model. Based on multiple sets of measurement data, it can predict the performance change trend of the rod end joint 5 during subsequent use, providing a more comprehensive basis for product quality assessment.

[0064] Among them, statistical methods and machine learning algorithms include random forests, which are composed of multiple decision trees. Decision trees construct tree structures by splitting features.

[0065] For regression problems, the prediction value of random forest is the average of the prediction values ​​of all decision trees;

[0066] For classification problems, the predicted value is the result of a majority vote of the decision trees.

[0067] In actual applications, the above algorithms will be optimized and combined according to specific needs and data characteristics to improve the accuracy of analysis and prediction.

[0068] The following are the core algorithms and corresponding formulas:

[0069] Size calculation

[0070] Calculation of the spherical head generatrix radius: The least squares method is often used to fit the spherical equation.

[0071] Let the equation of the sphere be

[0072] ,

[0073] For the measurement point ( , , ), by minimizing the error function

[0074] ,

[0075] Solve the parameter sphere center coordinates 、 、 and the spherical radius .

[0076] Aperture calculation: For the measured hole wall point data, a circle fitting algorithm can be used, such as the least squares method to fit the circle equation

[0077]

[0078] Similarly, the coordinates of the circle center are obtained by minimizing the error function ( , ) and radius .

[0079] Geometric tolerance calculation

[0080] Roundness Error: Based on the minimum area method, two concentric circles with the smallest radius difference that enclose the actual circle are found. This radius difference is the roundness error. During calculation, the circular profile data is converted to the frequency domain through Fourier transform analysis, and the shape features are extracted to calculate the error.

[0081] 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 based on the positional relationship between the sections. The least squares method or minimum area method is usually used for calculation.

[0082] Quality prediction model

[0083] Linear regression: If we assume that the quality index With multiple dimensions, geometric tolerance features , ,..., There is a linear relationship, and the model formula is

[0084] ,

[0085] in is the regression coefficient, is the error term. The regression coefficient is estimated by the least square method so that the actual value and predicted value The sum of squared errors is minimized.

[0086] Support Vector Machine (SVM):

[0087] For the binary classification problem, find the optimal hyperplane in the feature space , maximize the margin from the sample to the hyperplane.

[0088] Introducing kernel function It can handle nonlinear problems, and the decision function is

[0089] ,

[0090] in is the Lagrange multiplier.

[0091] Random Forest: This algorithm consists of multiple decision trees, which build a tree structure by splitting features. For regression problems, the prediction value of a random forest is the average of the prediction values ​​of all decision trees; for classification problems, the prediction value is the result of a majority vote of the decision trees.

[0092] In actual applications, the above algorithms will be optimized and combined according to specific needs and data characteristics to improve the accuracy of analysis and prediction.

[0093] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A positioning device for measuring rod end joints, characterized in that: The measuring plate includes a centering shaft sleeved on the measuring plate, the top end of the centering shaft extending out of the measuring plate and used to position the rod end joint, an adjustment platform connected to one side of the measuring plate by bolts, and a guide shaft movable up and down provided on the adjustment platform, the top end of the guide shaft having a V-shaped notch, through which the rod end joint is positioned in the circumferential direction, and a base sleeved on the bottom of the centering shaft; A plurality of electromagnetic chucks are provided in the measuring plate, and the plurality of electromagnetic chucks are arranged circumferentially on the measuring plate; The adjustment platform is provided with a stepped through hole which passes through the step-shaped through hole from top to bottom. The guide shaft is located in the stepped through hole. A compression spring is provided between the bottom of the inner wall of the stepped through hole and the guide shaft.

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

3. A positioning device for measuring a rod end joint according to claim 1, characterized in that: 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.

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

5. A positioning device for measuring a rod end joint according to claim 1, characterized in that: The centering shaft has a shaft shoulder, and the measuring plate is centered and positioned via the shaft shoulder of the centering shaft. The centering shaft and the measuring plate are interference-fitted.

6. A measurement method for a positioning device for measuring a rod end joint based on any one of claims 1 to 5, characterized in that: The specific steps include: Fix the base to the granite table of the coordinate measuring machine through flanges and bolts, and then place the rod end joint on the measuring 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 positioning of the rod end joint in the circumferential direction is achieved under the cooperation of gravity and the V-shaped notch, ensuring full contact between the lower end face of the rod end joint and the upper end face of the measuring plate without interference; Determine the coordinate system and, through programming, measure the ball head generatrix radius, hole diameter, ball head outer diameter, shaft end diameter, end face width, hole-shaft end distance, symmetry between the ball head and end faces, perpendicularity between the hole and end faces, and form and position tolerances of the rod end joint; After the workpiece is replaced, the rod end joint can be quickly positioned without changing the coordinate system, thus achieving rapid positioning of complex workpieces and rapid and precise measurement of parameters; After measuring the rod end joints multiple times, a quality prediction model is established based on the measurement results through the coordinate system automatic calibration algorithm, and the coordinate system is automatically adjusted using the three-coordinate transformation algorithm to ensure the accuracy of the measurement data.

7. A method for measuring a positioning device for measuring a rod end joint according to claim 6, characterized in that: The coordinate system automatic calibration algorithm 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 multiple calibration points, the coordinate system is automatically adjusted using the three-coordinate transformation algorithm based on the difference between the measurement results and the preset standard values ​​to ensure the accuracy of the measurement data.

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