Method for detecting involute helical gear keyway

Abstract

The application provides a kind of exciting robot keyway detection method of double helical gear, including gear clamping, keyway center surface fitting, workpiece coordinate system construction, digital model coordinate alignment, tooth surface deviation collection and center surface error calculation output.The exciting robot keyway detection method of double helical gear provided by the application acquires keyway two side surface point cloud through three coordinate measuring machine, constructs keyway symmetry center surface, and constructs reference rotary straight line in combination with inner hole axis, to establish accurate workpiece coordinate system.Through alignment with three-dimensional theoretical digital model, the method bypasses the problem that traditional means cannot touch virtual center line of addendum and dedendum, realizes point-to-point deviation comparison on the same tooth left and right tooth surface.Solves qualitative detection depending on artificial experience, changes to quantitative detection based on massive data, eliminates measurement blind area, and ensures the alignment accuracy of exciting gear during assembly.

Description

Technical Field

[0001] This invention belongs to the field of keyway processing technology, specifically relating to a method for detecting the keyway of a herringbone helical gear in a vibrator. Background Technology

[0002] A vibrator is a device that generates controllable periodic vibration force and applies it to a structure or equipment. The alignment accuracy of the keyway and teeth of the vibrator gear directly affects the operating stability of the vibrating screen. A coordinate measuring machine is a three-dimensional precision geometric measurement device. It relies on three mutually perpendicular motion axes of X, Y, and Z, and uses a probe to collect the three-dimensional coordinates of any point on the surface of the workpiece. The size, shape, and position tolerances are calculated by software.

[0003] In existing technologies, the alignment accuracy of the keyways and teeth of herringbone and helical gears used in vibrators is strictly required. Regardless of whether keyway cutting, milling, or wire EDM is used, precise detection of the positional error between the keyway and the teeth is necessary to ensure closed-loop machining quality. However, since the center of the tooth tip and the center of the tooth root of a helical gear are virtual lines in space without a physical contact surface, they cannot be directly detected. Conventional methods such as scribing, height gauges, and dial indicators cannot be used to directly locate points and align lines, making it impossible to directly obtain the relative positional deviation between the keyway and the teeth. The detection results are unreliable and cannot reflect the true machining accuracy of the gear. Summary of the Invention

[0004] This invention provides a method for detecting the keyway of a herringbone helical gear in a vibrator, which aims to solve the problem of unreliable detection results of the alignment accuracy between the inner hole keyway and the teeth of existing herringbone and helical gears used in vibrators.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: to provide a method for detecting the keyway of a herringbone helical gear in a vibrator, comprising the following steps: S1: Place the gear to be inspected on the worktable of the coordinate measuring machine and adjust its posture so that the inner hole axis is collinear with the Z-axis of the coordinate measuring machine; S2: Collect several measuring points on the left and right sides of the keyway and fit them to obtain the symmetrical center plane of the keyway; S3: Collect several measuring points on the inner hole of the gear and fit the inner hole axis; establish the workpiece coordinate system with the inner hole axis as the rotation axis; S4: Import the three-dimensional theoretical digital model of the gear into the coordinate measuring system and align the coordinate system of the theoretical digital model with the coordinate system of the workpiece; S5: Collect several measuring points on the left and right tooth surfaces of the same gear, and calculate the normal deviation of each measuring point relative to the corresponding point of the theoretical digital model after alignment; S6: Based on the normal deviation, the actual tooth thickness symmetry center plane is obtained, the spatial position error between the actual tooth thickness symmetry center plane and the keyway symmetry center plane is calculated, and the detection result is output.

[0006] In one possible implementation, in step S2, at least two measuring points are collected along the keyway axis in the upper, middle and lower layers respectively, and plane fitting is performed on the measuring points on the left and right sides respectively to obtain the symmetry center plane of the keyway.

[0007] In one possible implementation, the upper, middle, and lower layers are uniformly distributed along the keyway axis.

[0008] In one possible implementation, in step S3, two sampling sections, upper and lower, are set along the axial direction of the inner hole. Each section collects several circumferentially distributed inner hole measuring points, and the inner hole axis is obtained by fitting the cylindrical surface.

[0009] In one possible implementation, four circumferentially evenly distributed measuring points are set in each layer, and the measuring points of the upper and lower layers are staggered by 45° in the circumferential direction.

[0010] In one possible implementation, in step S5, 6 to 10 measuring points are collected on each of the left and right tooth surfaces of the same gear tooth, and the normal deviation is the difference between the actual coordinate value of the measuring point along the tooth surface normal direction and the theoretical coordinate value of the corresponding point of the theoretical digital model.

[0011] In one possible implementation, in step S6, the actual tooth thickness symmetry center plane is obtained by fitting the normal deviation using the least squares method.

[0012] In one possible implementation, in step S6, the spatial position error is calculated in the following manner: Calculate the first average value of the normal deviation of all measuring points on the left tooth surface and the second average value of the normal deviation of all measuring points on the right tooth surface, respectively; The difference between the second average value and the first average value is calculated as the offset error of the keyway symmetry center plane relative to the actual gear tooth thickness symmetry center plane.

[0013] In one possible implementation, the sign of the offset error indicates the direction of offset of the keyway symmetry center plane relative to the actual gear tooth thickness symmetry center plane.

[0014] In one possible implementation, the keyway position is deemed acceptable when the absolute value of the offset error is not greater than 0.05 mm.

[0015] In this implementation, compared with existing technologies, a coordinate measuring machine (CMM) is used to collect point clouds from both sides of the keyway, constructing a symmetrical center plane for the keyway. A reference rotation line is then constructed based on the inner hole axis, thereby establishing a precise workpiece coordinate system. By aligning with the three-dimensional theoretical model, this method bypasses the problem of traditional methods being unable to reach the virtual center lines of the tooth tip and root, achieving point-to-point deviation comparison on the left and right tooth surfaces of the same gear. It solves the problem of qualitative inspection relying on manual experience, replacing it with quantitative inspection based on massive amounts of data, eliminating measurement blind spots, and ensuring the alignment accuracy of the vibrator gear during assembly. Attached Figure Description

[0016] Figure 1 A flowchart illustrating the steps of the method for detecting the keyway of a herringbone gear in a vibrator according to an embodiment of the present invention; Explanation of reference numerals in the attached figures: S1. Gear clamping and adjustment; S2. Keyway center surface fitting; S3. Workpiece coordinate system construction; S4. Digital model coordinate alignment; S5. Gear tooth surface deviation acquisition; S6. Center surface error calculation and output. Detailed Implementation

[0017] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0018] It should be noted that the terms "length", "width", "height", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "head", and "tail" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0019] It should also be noted that, unless otherwise explicitly specified and limited, terms such as "installation," "connection," "fixing," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0020] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Additionally, "multiple" and "several" mean two or more, unless otherwise explicitly specified.

[0021] Please refer to the following: Figure 1 The present invention describes a method for detecting the keyway of a herringbone helical gear in a vibrator. The method includes the following steps: S1: Place the gear to be tested on the worktable of a coordinate measuring machine (CMM) and adjust its posture so that the inner hole axis is collinear with the Z-axis of the CMM; S2: Collect several measuring points on the left and right sides of the keyway and fit them to obtain the keyway symmetry center plane; S3: Collect several measuring points on the inner hole of the gear and fit them to obtain the inner hole axis; establish a workpiece coordinate system using the inner hole axis as the rotation axis; S4: Import the three-dimensional theoretical model of the gear into the CMM system and align the coordinate system of the theoretical model with the workpiece coordinate system; S5: Collect several measuring points on the left and right tooth surfaces of the same gear tooth and calculate the normal deviation of each measuring point relative to the corresponding point on the aligned theoretical model; S6: Fit the actual tooth thickness symmetry center plane based on the normal deviation, calculate the spatial position error between the actual tooth thickness symmetry center plane and the keyway symmetry center plane, and output the detection result.

[0022] The method for detecting the keyway of the herringbone helical gear in this embodiment, compared with existing technologies, uses a coordinate measuring machine to collect point clouds from both sides of the keyway, constructs the symmetrical center plane of the keyway, and combines it with the inner hole axis to construct a reference rotation line, thereby establishing a precise workpiece coordinate system. By aligning with the three-dimensional theoretical digital model, this method bypasses the problem of traditional methods being unable to reach the virtual center lines of the tooth tip and tooth root, and achieves point-to-point deviation comparison on the left and right tooth surfaces of the same gear. It solves the problem of qualitative detection relying on manual experience, and replaces it with quantitative detection based on massive data, eliminating measurement blind spots and ensuring the alignment accuracy of the vibrator gear during assembly.

[0023] By aligning the inner bore axis of the gear under test with the Z-axis of the coordinate measuring machine (CMM), the inherent challenge of directly measuring the center of the helical gear tooth tip and root, which are virtual spatial lines, is solved. This transforms the previously inaccessible spatial reference into a measurable physical axis reference, providing a stable spatial reference for subsequent coordinate system establishment. Adjusting the orientation essentially reduces the workpiece's degrees of freedom from six constraints to a single rotational degree of freedom around the Z-axis. The inner bore axis then becomes the sole spatial rotational reference, preventing measurement reference drift caused by arbitrary workpiece placement. By acquiring measurement points on both sides of the keyway and fitting a symmetry center plane, compared to traditional dial indicator alignment which only obtains local linear deviations, the spatial planar characteristics of the keyway along its entire axial length are fully characterized, eliminating the interference of the keyway's own straightness error on the accuracy of the symmetry plane fitting. Establishing a workpiece coordinate system with the inner bore axis as the rotation axis ensures complete unification with the gear's own rotational reference. All subsequent measurement data are based on this same reference, fundamentally eliminating the cumulative errors caused by multiple reference conversions. Importing the 3D theoretical model and aligning the coordinate system enables a digital mapping between the theoretical design state and the actual machining state. This transforms the experience-based judgment that previously required manual comparison of drawings into automatic mathematical calculations by the computer, significantly reducing human interpretation errors. By collecting measurement points on the left and right tooth surfaces of the same gear and calculating the normal deviation, the tooth surface is used as a natural measurement benchmark, avoiding the limitation of the unmeasurable virtual tooth tip center. The tooth thickness symmetry center plane is inferred from the actual tooth surface morphology, essentially reconstructing the virtual tooth reference using the physical tooth surface information. Calculating the spatial position error between the actual tooth thickness symmetry center plane and the keyway symmetry center plane directly reflects the true positional deviation of the keyway relative to the tooth during machining, rather than the approximate value calculated through indirect measurement in traditional methods, thus fundamentally improving the reliability of the inspection results. This method can be applied to the final inspection of various helical gears and herringbone gears with keyways, and is particularly suitable for scenarios such as vibrator gears where the alignment accuracy between the keyway and the tooth is critical.

[0024] In the replacement scheme of the higher-level concept, adjusting the posture to make the inner hole axis collinear with the Z-axis of the measuring machine can be replaced by adjusting the posture to make the inner hole axis collinear with the X-axis or Y-axis of the measuring machine, which only requires corresponding adjustment of the coordinate system definition; the three-dimensional theoretical model can be replaced by two-dimensional theoretical cross-sectional profile data, in which case it is necessary to align and measure multiple cross-sections in the axial direction respectively; the calculation of spatial position error can be replaced by calculating the angle between the two symmetry center planes in the plane perpendicular to the inner hole axis, which is suitable for evaluating angular deviation scenarios.

[0025] This method uses tooth surface measuring points to infer the tooth thickness symmetry center plane, effectively and simultaneously detecting tooth thickness deviation. It achieves combined detection of keyway position and tooth thickness without requiring additional measurement steps, thus improving detection efficiency. Furthermore, since all measurement data are based on the same workpiece coordinate system, if subsequent tracing of the measurement process is needed, the original measuring point coordinates can be directly retrieved for recalculation, meeting the traceability requirements of quality inspection.

[0026] In some embodiments, the above-described S2 may employ, as follows: Figure 1 The structure shown. See also Figure 1 In step S2, at least two measuring points are collected along the keyway axis in the upper, middle and lower layers respectively, and plane fitting is performed on the measuring points on the left and right sides respectively to obtain the symmetry center plane of the keyway.

[0027] By collecting at least two measurement points in the upper, middle, and lower layers along the keyway's axial direction, and performing planar fitting on the left and right sides respectively, the symmetry center plane of the keyway is obtained. This effectively overcomes the influence of possible torsional deformation during keyway machining on the symmetry plane fitting. Traditional methods only measure at a single point at the end or middle of the keyway. If the keyway has axial torsion, the single-point measurement result will deviate significantly from the actual symmetry center plane. The three-layer sampling layout can capture the spatial morphology of the keyway sides from three different axial positions. Even if the keyway has minor torsional deformation, its overall orientation can be accurately restored through the fitting of the planes in each layer. The operation of fitting the planes separately for the left and right sides avoids the symmetry plane skew that may be caused by mixing the measurement points of the two sides for fitting, because mixed fitting assumes that the two sides are coplanar, while the two sides may have parallelism errors in actual machining. Separate fitting better reflects the true machining state. The setting of at least two measurement points in each layer ensures the minimum data requirement for plane fitting and avoids instability in the solution of the plane equation due to insufficient measurement points. This method can be applied to the inspection of gears with long keyways, especially the keyways of herringbone gears, whose axial length is usually large and more prone to torsional deformation.

[0028] In the replacement scheme of the superordinate concept, the three-layer sampling of the upper, middle and lower layers can be replaced with four or more layers of sampling, and the layer spacing can be uniformly or non-uniformly distributed according to the keyway length; the sampling of at least two measurement points per layer can be replaced with sampling of three or more measurement points to improve the plane fitting accuracy; the plane fitting algorithm can be replaced with other fitting algorithms besides the least squares method, such as the Chebyshev approximation method, to adapt to different accuracy requirements.

[0029] In some embodiments, the above-mentioned measuring points can be adopted as follows: Figure 1 The structure shown. See also Figure 1 The upper, middle and lower measuring points are evenly distributed along the keyway axis.

[0030] By uniformly distributing the upper, middle, and lower sampling points along the keyway axis, the weight of each axial position is ensured to be equal during the fitting of the keyway's symmetry center plane, avoiding the problem of the symmetry plane being biased towards a certain area due to uneven distribution of sampling points. If the sampling points are concentrated at one end of the keyway, the fitted symmetry plane will over-reflect the machining error at that end and cannot represent the average state of the entire keyway. Uniform distribution allows the symmetry plane to integrate machining information across the entire length of the keyway, which is more in line with the characteristics of the keyway as an overall functional structure. The uniform distribution also simplifies sampling path planning. Operators do not need to manually calculate the position of each sampling section; they only need to arrange the sampling points at fixed intervals, reducing operational difficulty and errors caused by human intervention. For keyways with slight curvature, uniformly distributed sampling points can more sensitively capture their curvature trend because bending deformation usually changes continuously in the axial direction, and uniform sampling can completely record this change characteristic. This method can be applied to the detection of various straight or oblique keyways, especially suitable for gears with a large keyway length-to-diameter ratio, as the keyways of these gears are more prone to axial deformation.

[0031] In the replacement scheme of the higher-level concept, the upper and lower sampling sections can be replaced with three or more sampling sections, and the interlayer spacing can be adjusted according to the inner hole length; the number of measuring points distributed circumferentially in each layer can be replaced with three or more, and the circumferential distribution angle can be adjusted according to the characteristics of the inner hole roundness error, for example, more measuring points can be used for inner holes with poor roundness; cylindrical surface fitting can be replaced with cylindrical surface evaluation based on the minimum area method to meet the detection requirements of different accuracy levels.

[0032] In some embodiments, the above-mentioned feature S3 can be adopted as follows: Figure 1 The structure shown. See also Figure 1 In step S3, two sampling sections, upper and lower, are set along the axial direction of the inner hole. Each section collects several circumferentially distributed inner hole measuring points, and the inner hole axis is obtained by fitting the cylindrical surface.

[0033] By setting up upper and lower sampling sections along the axial direction of the inner hole, and collecting several circumferentially distributed measuring points in each section, the inner hole axis is obtained through cylindrical surface fitting. Compared with single-layer section fitting or three-point circle determination, this significantly improves the accuracy of inner hole axis determination. Single-layer section fitting can only reflect the roundness error of the inner hole at that section, and cannot reflect the axial straightness deviation of the inner hole. However, setting up two sections can capture the spatial shape of the inner hole from two axial positions. The axis is determined by connecting the centers of the two sections, effectively eliminating the influence of local roundness error of the inner hole on the axis position. The cylindrical surface fitting process comprehensively considers minimizing the sum of the squares of the distances from all measuring points to the ideal cylindrical surface. Compared with the simple center-connection method, it is more resistant to the interference of individual abnormal measuring points on the axis fitting, improving the robustness of axis determination. The setting of several circumferentially distributed measuring points in each layer ensures the integrity of the circumferential information of the cylindrical surface fitting, avoiding distortion of the cylindrical surface shape due to uneven distribution of measuring points. This method can be applied to determine the centerline of various internal hole parts, not only gear internal holes, but also to the coaxiality detection of parts such as bushings and bearing seats.

[0034] In the replacement scheme of the higher-level concept, the upper and lower sampling sections can be replaced with three or more sampling sections, and the interlayer spacing can be adjusted according to the inner hole length; the number of measuring points distributed circumferentially in each layer can be replaced with three or more, and the circumferential distribution angle can be adjusted according to the characteristics of the inner hole roundness error, for example, more measuring points can be used for inner holes with poor roundness; cylindrical surface fitting can be replaced with cylindrical surface evaluation based on the minimum area method to meet the detection requirements of different accuracy levels.

[0035] In some embodiments, the above-mentioned measuring points can be adopted as follows: Figure 1 The structure shown. See also Figure 1 Four measuring points are set up in each layer, evenly distributed in the circumference. The measuring points in the upper and lower layers are staggered by 45° in the circumference.

[0036] By setting four circumferentially evenly distributed measurement points in each layer, with the upper and lower layers staggered by 45° in the circumferential direction, optimal information coverage for fitting the cylindrical surface of the inner hole is achieved with the minimum number of measurement points. The four circumferentially evenly distributed measurement points form a square sampling layout, which can completely reflect the dimensional information of the inner hole in four orthogonal directions within a cross-section. Compared to a triangular layout with three measurement points, this layout is more resistant to the influence of elliptical deformation of the inner hole, because the major and minor axes of the elliptical hole can be precisely captured by the measurement points in the square layout. The 45° stagger of the upper and lower layers of measurement points avoids overlap between the two layers in the same radial direction, resulting in eight evenly distributed sampling points on the circumference of the inner hole. This is equivalent to sampling a cross-section in eight directions, significantly improving the sensitivity of the cylindrical surface fitting to circumferential errors. This layout also effectively eliminates the influence of probe systematic errors, because if systematic errors exist between the upper and lower layers of measurement points in the same radial direction, they will be canceled out by the measurement points in other directions staggered by 45°.

[0037] In the replacement scheme of the upper concept, the four circumferentially evenly distributed measuring points in each layer can be replaced with six or eight measuring points to accommodate larger diameters or poor roundness of inner holes; the 45° offset can be replaced with a 30° or 60° offset, and the specific angle can be adjusted according to the processing characteristics of the inner hole.

[0038] In some embodiments, the above-described S5 may employ, as follows: Figure 1 The structure shown. See also Figure 1 In step S5, 6 to 10 measuring points are collected on each of the left and right tooth surfaces of the same gear tooth. The normal deviation is the difference between the actual coordinate value of the measuring point along the tooth surface normal direction and the theoretical coordinate value of the corresponding point of the theoretical model.

[0039] By collecting 6-10 measurement points on each of the left and right tooth surfaces of the same gear, and calculating the difference between the actual and theoretical coordinates of the measurement points along the tooth surface normal direction as the normal deviation, high-fidelity digital characterization of the tooth surface morphology is achieved. The 6-10 measurement points ensure coverage of the working area of ​​the tooth surface (typically including the tooth tip, tooth middle, and tooth root regions) while avoiding the decrease in measurement efficiency caused by too many measurement points. Each measurement point provides information on the normal deviation of the tooth surface at that location. Through the deviation distribution of these discrete points, the error spectrum of the entire tooth surface can be reconstructed. Using normal deviation instead of coordinate deviation as the evaluation index conforms to the actual force state of gear meshing, because the direction of the tooth surface contact force in gear transmission is the normal direction. The normal deviation directly reflects the geometric error of the tooth surface in the contact direction, which is more significant in engineering than single coordinate deviations in the X / Y / Z directions. This measurement method can capture the microscopic geometric errors of the tooth surface, such as tooth profile error and tooth direction error, in their local manifestations, providing an accurate tooth surface reference for subsequent fitting of the tooth thickness symmetry center plane. This method can be applied to the surface accuracy testing of various involute gears and circular arc gears, and is especially suitable for transmission gears that require high-precision meshing.

[0040] In the replacement scheme of the higher-level concept, 6-10 measuring points can be replaced with the number of measuring points adjusted according to the tooth width. For example, 4-6 measuring points can be used for narrow tooth surfaces, and 10-15 measuring points can be used for wide tooth surfaces. The distribution of measuring points can be replaced with a uniform grid distribution along the tooth height and tooth width directions, or a dense distribution concentrated in the tooth surface contact mark area. The calculation of normal deviation can be replaced with the calculation of deviation along the tooth surface tangent direction, which is suitable for evaluating parameters such as tooth surface roughness.

[0041] In some embodiments, the above-described S6 may employ, as follows: Figure 1 The structure shown. See also Figure 1 In step S6, the actual tooth thickness symmetry center plane is obtained by fitting the normal deviation using the least squares method.

[0042] The least squares method is used to fit the actual tooth thickness symmetry center plane based on the normal deviation. This method achieves optimal statistical estimation results even with measurement noise and microscopic tooth surface errors. The core idea of ​​the least squares method is to minimize the sum of the squares of the normal deviations of all measurement points. This is equivalent to smoothing the measurement data, effectively suppressing the interference of outliers (such as tooth surface impacts or probe mis-triggered points) on the fitting results, and improving the robustness of the determined symmetry center plane. Compared to simply using the average value of the measurement points on the left and right tooth surfaces as the symmetry center, the least squares method considers the contribution of all measurement points and assigns different weights according to the magnitude of the deviation, thus better reflecting the overall average state of the tooth surface. Fitting the symmetry center plane through the normal deviation essentially involves finding a symmetry plane that best matches the measured data of the left and right tooth surfaces. The deviation of this plane from the theoretical tooth thickness symmetry center plane directly reflects the actual positional error of the keyway relative to the tooth, eliminating the cumulative effect of the tooth surface's own shape errors. This method can be applied to various scenarios requiring high-precision determination of the symmetry plane, such as gear pair center distance measurement and spline symmetry detection.

[0043] In the replacement schemes for the higher-level concept, the least squares method can be replaced with the weighted least squares method, assigning different weights to the measurement points based on their positions on the tooth surface; for example, measurement points in the tooth contact area have higher weights. Alternatively, it can be replaced with the least squares method to reduce the impact of outliers. Another option is to replace it with a robust fitting algorithm based on RANSAC, suitable for scenarios with a large number of outlier measurement points. The hidden effect of this technique is that the sum of squared residuals obtained during the least squares fitting process can serve as an indicator for evaluating the quality of the tooth surface machining. The smaller the residual, the higher the precision of the tooth surface machining, which provides a new dimension for the quantitative evaluation of gear quality.

[0044] In some embodiments, the above-described S6 may employ, as follows: Figure 1 The structure shown. See also Figure 1 In step S6, the spatial position error is calculated as follows: the first average value of the normal deviation of all measuring points on the left tooth surface and the second average value of the normal deviation of all measuring points on the right tooth surface are calculated respectively; the difference between the second average value and the first average value is calculated as the offset error of the keyway symmetry center plane relative to the actual tooth thickness symmetry center plane.

[0045] This method provides an intuitive and physically meaningful error characterization method by calculating the first average of the normal deviations of all measuring points on the left tooth surface and the second average of the normal deviations of all measuring points on the right tooth surface, and then taking the difference between the two as the offset error of the keyway symmetry center plane. The first and second averages represent the average normal deviations of the left and right tooth surfaces, respectively, reflecting the overall offset of the tooth surface in the normal direction. The difference between the two is essentially a quantitative indicator of the degree of asymmetry between the left and right tooth surfaces, directly corresponding to the offset of the tooth thickness symmetry center plane relative to the theoretical position. This method avoids complex plane fitting calculations; the offset error can be obtained through simple statistics of the measuring point deviations. The calculation process is concise and efficient, suitable for embedded algorithm implementation in rapid on-site inspection and automated measurement systems. Compared to directly calculating the spatial distance between the two symmetry center planes, this method indirectly obtains the offset through the deviation difference, which can effectively offset some systematic errors (such as probe radius compensation error and probe pre-stroke error), because these systematic errors simultaneously affect the measuring point deviations of the left and right tooth surfaces, canceling each other out in the difference calculation. This method can be applied to online rapid sorting in mass production. Operators do not need to understand complex geometric relationships; they only need to focus on the deviation difference to determine whether the product is qualified.

[0046] In the replacement scheme of the higher-level concept, the average value calculation can be replaced by the median calculation to reduce the impact of outliers; it can also be replaced by a weighted average, which assigns different weights according to the importance of the measuring point on the tooth surface; the difference calculation can be replaced by the absolute value difference, which only focuses on the magnitude of the offset and does not consider the direction; the difference between the deviations of the left and right tooth surfaces can also be converted into angular deviation, which is suitable for evaluating the symmetry error of the tooth direction.

[0047] In some embodiments, the aforementioned offset error can be expressed as follows: Figure 1 The structure shown. See also Figure 1 The sign of the offset error indicates the direction of offset of the keyway symmetry center plane relative to the actual gear tooth thickness symmetry center plane.

[0048] The positive and negative values ​​of the offset error indicate the direction of the offset of the keyway's center of symmetry relative to the actual tooth thickness's center of symmetry, providing directional guidance for error analysis and process adjustment. The definition of the positive and negative signs establishes a connection between the offset direction and the coordinate system, transforming abstract geometric deviations into numerical values ​​with clear physical meaning. Operators can directly determine whether the keyway is offset to the left or right of the tooth thickness's center of symmetry based on the positive or negative sign, without needing complex spatial visualization. This directional indication is crucial for process adjustments in mass production. For example, if the gear offset error produced by a certain machine tool is consistently positive, it indicates a fixed positional deviation in the keyway machining tool. Operators only need to adjust the tool position according to the positive or negative sign, without repeated trial cuts. The introduction of positive and negative signs also facilitates statistical error analysis. For example, calculating the mean and standard deviation of the offset error for a batch of products can assess the stability of the machining process. If the mean is not zero, it indicates a systematic deviation; if the standard deviation is too large, it indicates significant fluctuations in the machining process.

[0049] In the replacement scheme of the higher-level concept, the definition of positive and negative values ​​can be replaced by relating them to the rotation direction of the gear, for example, defining clockwise offset as positive and counterclockwise as negative, which is more in line with the engineering practice of gear transmission; it can also be replaced by relating them to the gear assembly direction, for example, facing the gear input end, offset to the left is positive and offset to the right is negative; it can also use angle values ​​to represent the offset direction, for example, an offset angle of +5° represents a clockwise offset of 5°.

[0050] In some embodiments, the aforementioned offset error can be expressed as follows: Figure 1 The structure shown. See also Figure 1 When the absolute value of the offset error is not greater than 0.05mm, the keyway position is deemed qualified.

[0051] By setting an absolute offset error of no more than 0.05 mm as the threshold for judging the keyway position as acceptable, a clear and quantifiable acceptance standard is provided for the quality control of the herringbone gears of the vibrator. This threshold is not arbitrarily selected, but is based on the actual working characteristics of the vibrator gears: the vibrator generates high-frequency periodic vibrations during operation. If the misalignment error between the keyway and the teeth is too large, it will cause additional radial and axial forces when the gear transmits torque, exacerbating bearing wear and gear fatigue failure. The 0.05 mm limit ensures gear operational stability while balancing machining economy and testing feasibility.

[0052] In the replacement scheme of the higher-level concept, the 0.05mm threshold can be replaced with a dynamic allowable deviation value calculated based on parameters such as gear module, speed, and load. For example, the threshold can be appropriately relaxed for large module and low speed gears, while the threshold should be appropriately tightened for small module and high speed gears. The judgment rule can be replaced with a combination judgment, such as simultaneously satisfying that the absolute value of the offset error is not greater than 0.05mm and the angle between the two symmetrical center planes is not greater than a specific angle. Alternatively, it can be replaced with a statistical judgment, such as that the absolute value of the offset error in more than 90% of a batch of products is not greater than 0.03mm, and the maximum value does not exceed 0.05mm.

[0053] 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 within the protection scope of the present invention.

Claims

1. A method of detecting a key groove of a bevel gear of a shaker, characterized by, Includes the following steps: S1: Place the gear to be inspected on the worktable of the coordinate measuring machine and adjust its posture so that the inner hole axis is collinear with the Z-axis of the coordinate measuring machine; S2: Collect several measuring points on the left and right sides of the keyway and fit them to obtain the symmetrical center plane of the keyway; S3: Collect several measuring points on the inner hole of the gear and fit the inner hole axis; establish the workpiece coordinate system with the inner hole axis as the rotation axis; S4: Import the three-dimensional theoretical digital model of the gear into the coordinate measuring system and align the coordinate system of the theoretical digital model with the coordinate system of the workpiece; S5: Collect several measuring points on the left and right tooth surfaces of the same gear, and calculate the normal deviation of each measuring point relative to the corresponding point of the theoretical digital model after alignment; S6: Based on the normal deviation fitting, obtain the actual tooth thickness symmetry center plane, calculate the spatial position error between the actual tooth thickness symmetry center plane and the keyway symmetry center plane, and output the detection result.

2. The exciter herringbone gear keyway inspection method of claim 1 wherein, In step S2, at least two measuring points are collected along the keyway axis in the upper, middle and lower layers respectively, and plane fitting is performed on the measuring points on the left and right sides respectively to obtain the symmetry center plane of the keyway.

3. The method of claim 2, wherein the method further comprises: determining the keyway profile of the involute helical gear by determining the keyway profile of the involute helical gear using the determined keyway profile of the involute spur gear. The upper, middle, and lower measuring points are evenly distributed along the keyway axis.

4. The method of claim 3, wherein the method further comprises: determining the keyway profile of the involute helical gear by determining the keyway profile of the involute helical gear using the determined keyway profile of the involute spur gear. In S3, two sampling sections, upper and lower, are set along the axial direction of the inner hole. Each section collects several circumferentially distributed inner hole measuring points, and the inner hole axis is obtained by fitting the cylindrical surface.

5. The method for detecting the keyway of a herringbone helical gear in a vibrator as described in claim 4, characterized in that, Each layer of S3 has four circumferentially evenly distributed measuring points, and the measuring points of the upper and lower layers are staggered by 45° in the circumferential direction.

6. The method for detecting the keyway of a herringbone helical gear in a vibrator as described in claim 1, characterized in that, In S5, 6 to 10 measuring points are collected on each of the left and right tooth surfaces of the same gear tooth. The normal deviation is the difference between the actual coordinate value of the measuring point along the tooth surface normal direction and the theoretical coordinate value of the corresponding point of the theoretical model.

7. The method for detecting the keyway of a herringbone helical gear in a vibrator as described in claim 1, characterized in that, In step S6, the actual tooth thickness symmetry center plane is obtained by fitting the normal deviation using the least squares method.

8. The method for detecting the keyway of a herringbone helical gear in a vibrator as described in claim 1, characterized in that, In step S6, the spatial position error is calculated in the following way: Calculate the first average value of the normal deviation of all measuring points on the left tooth surface and the second average value of the normal deviation of all measuring points on the right tooth surface, respectively; The difference between the second average value and the first average value is calculated as the offset error of the keyway symmetry center plane relative to the actual gear tooth thickness symmetry center plane.

9. The method of claim 8, wherein the method further comprises: determining the keyway profile of the involute helical gear by determining the keyway profile of the involute helical gear using the determined profile of the involute helical gear and the determined profile of the involute helical gear key. The positive or negative value of the offset error indicates the offset direction of the keyway symmetry center plane relative to the actual gear tooth thickness symmetry center plane.

10. The method of claim 8, wherein the method further comprises: determining a pitch of the involute helical gear keyway; and determining a pitch of the involute helical gear keyway. When the absolute value of the offset error is not greater than 0.05mm, the keyway position is deemed qualified.

Images