A method of evaluating a contact patch of a gear pair

Abstract

A method for evaluating gear pair contact pattern, comprising the following steps: S1: building a three-dimensional model of theoretical parameters, and calculating a theoretical development length of any point; S2: scanning an actual gear tooth profile to obtain an actual development length of any point on a scanning line; S3: making a difference between the actual development length and the theoretical development length of each point on the scanning line to obtain a deviation value; S4: using a Lagrange polynomial interpolation method on the deviation value to obtain a deviation value of any point on the gear tooth profile; S5: selecting different tooth curve lines, identifying the deviation values of the tooth curve lines and all points on the scanning line, connecting the equal deviation values to obtain a contour map; S6: respectively determining a tooth curve line of a driving gear and a driven gear of the gear pair, superimposing the tooth curve lines of the gear pair and the deviation values of the corresponding positions of the scanning line to obtain superimposed values; S7: identifying the superimposed values, connecting the equal superimposed values into a contour map to display the gear pair contact pattern; and S8: evaluating the gear pair according to the contour map obtained in S7.

Description

Technical Field

[0001] This invention relates to the field of gear transmission, and more specifically to a method for evaluating the contact pattern of a gear pair. Background Technology

[0002] The shape of the gear and the quality of its assembly and meshing have a direct impact on the reliability, vibration, and noise of gear transmissions.

[0003] Currently, such as Figure 7 As shown, the gear evaluation method involves using a scanning probe to measure along tooth profile routes 11, 12, and 13 and along tooth direction routes 14, 15, and 16 to obtain the actual numerical values ​​of parameters such as the gear's digital model, profile, and involute. These parameter values ​​are then compared with the values ​​specified in national standards for deviation assessment. However, this method only evaluates the quality of a single gear measurement and cannot provide a systematic evaluation of the contact patterns of gear pairs, making its function relatively limited. The scanning probe measurement is time-consuming, and the limited number of scanning lines leads to inaccurate evaluation of the actual tooth profile and poor evaluation results. To obtain more accurate evaluation results, more scanning lines must be set, which consumes even more time. Furthermore, existing evaluation methods that compare two values ​​involve dozens of data sets, requiring careful comparison by personnel, resulting in low evaluation efficiency and a high risk of errors. It also fails to provide a quick and intuitive understanding of the gear morphology and gear pair fit. Solving these problems requires an accurate, fast, and intuitive method for evaluating gear pair contact patterns. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for evaluating the contact pattern of gear pairs. By interpolating the deviation values ​​of the driving and driven gears of the gear pair respectively, a contour map of the gear pair engagement is obtained, thus solving the problems of limited functionality and low efficiency in gear evaluation methods.

[0005] The objective of this invention is achieved by the following method: a method for evaluating contact patterns of a gear pair, comprising the following steps:

[0006] S1: Based on the designed gear tooth profile shape, establish a three-dimensional model of the theoretical parameters, and calculate the unfolded length of any point on the theoretical tooth profile;

[0007] S2: Scan the actual gear tooth profile that has been machined. The scanning lines are multiple scanning lines on the tooth surface in the tooth direction, and the actual unfolded length of any point on the scanning line is obtained.

[0008] S3: The computer receives the actual unfolded length of any point on the scan line and maps it to the 3D model. It calculates the difference between the actual unfolded length and the theoretical unfolded length of each point on the scan line, obtains the deviation value of the unfolded length of each point, and stores it in the computer.

[0009] S4: Use Lagrange's polynomial interpolation method to obtain the unfolded length deviation value of any point on the gear tooth profile at the same tooth width on each scanning line;

[0010] S5: Select multiple different tooth direction curves as required, identify the unfolded length deviation values ​​of all points on the tooth direction curves and the scan line, connect the equal unfolded length deviation values ​​to obtain the contour map.

[0011] S6: Use step S4 to obtain the unfolded length deviation value of any point of the driving gear and driven gear of the gear pair and determine the tooth direction curve. Superimpose the unfolded length deviation value of the tooth direction curve of the gear pair and the meshing position of the scanning line to obtain the superimposed value of the tooth direction curve and any point on the scanning line.

[0012] S7: Identify the superimposed values ​​and connect equal superimposed values ​​to form a contour map to display the contact spots of the gear pair;

[0013] S8: Evaluate the gear pair based on the contour map obtained in S7.

[0014] The theoretical parameters include the number of teeth, module, pressure angle, helix angle, displacement coefficient, addendum circle diameter, dedendum circle diameter, and center distance of the gear pair.

[0015] The scan line also includes a positioning scan line located at the midpoint of the tooth width and parallel to the theoretical involute.

[0016] The scan lines are all located between the tooth root and the tooth tip and are distributed at equal intervals. The theoretical unfolded length of all points on the same scan line is the same.

[0017] The tooth profile curves are distributed on both sides of the scan line. The scan line and the adjacent tooth profile curves are equidistantly distributed, and the tooth profile curves between two scan lines are also equidistantly distributed. The number of tooth profile curves is determined according to the size of the gear being tested and the required detection accuracy.

[0018] The regions between different closed curves on the contour map are displayed using different colors.

[0019] Using the above scheme, the deviation value at any point is obtained by Lagrange interpolation of the deviation value on the scanning line. A contour map is formed by identifying and connecting the deviation values ​​on the tooth profile curve and the scanning line. By scanning the driving and driven gears of the gear pair separately, and interpolating and superimposing the deviation values, a contour map of the gear pair contact patch is obtained. Using the contour map for observation and evaluation not only allows for a rapid and accurate assessment of the gear pair's fit, but also provides a quick and intuitive understanding of the morphology and quality of individual gears, resulting in high evaluation efficiency and convenient operation.

[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0021] Figure 1 This is a flowchart of the present invention;

[0022] Figure 2 This is a schematic diagram of the scan line distribution of the present invention;

[0023] Figure 3 This is a schematic diagram of the tooth profile distribution of the present invention;

[0024] Figure 4 This is a contour plot of the gear tooth profile of the present invention;

[0025] Figure 5 This is a contour map showing the good contact area of ​​the gear pair in this invention;

[0026] Figure 6 This is a contour map showing the poor contact pattern of the gear pair in this invention;

[0027] Figure 7 This is a schematic diagram of the existing scan line distribution. Detailed Implementation

[0028] like Figures 1 to 6 As shown, a method for evaluating contact patterns in a gear pair includes the following steps:

[0029] S1: Based on the designed gear tooth profile shape, establish a three-dimensional model of theoretical parameters, and calculate the unfolded length of any point on the theoretical tooth profile; the theoretical parameters include the number of teeth, module, pressure angle, helix angle, displacement coefficient, addendum circle diameter, dedendum circle diameter, and center distance of the gear pair.

[0030] S2: The machined actual gear tooth profile is scanned using a probe scanner. The scan lines are multiple scan lines on the tooth surface in the tooth direction. In this embodiment, the scan lines are as follows: Figure 2 The diagram shows six scanning lines: 21, 22, 23, 24, 25, and 26. These scanning lines are all located between the tooth root and the tooth tip and are evenly spaced. The theoretical unfolded length of all points on the same scanning line is the same. The scanning line also includes a positioning scanning line 27 for scanner positioning. This positioning scanning line is located at the midpoint of the tooth width and is parallel to the theoretical involute. During scanning, the actual parameters of the tooth profile of the gear being measured are first obtained through the positioning scanning line 27. The actual parameters are compared with the theoretical parameters to determine whether the scanner has scanned the correct gear being measured. Then, the six scanning lines in the tooth direction are scanned, and the actual unfolded length of any point on the scanning line is obtained through scanning.

[0031] S3: The computer receives the actual unfolded length of any point on the scan line and maps it to the 3D model. It calculates the difference between the actual unfolded length and the theoretical unfolded length of each point on the scan line, taking the value higher than the designed gear tooth profile surface as a positive value and the value lower than the designed gear tooth profile surface as a negative value. The deviation value of the unfolded length of each point is obtained and stored in the computer.

[0032] S4: Use Lagrange's polynomial interpolation method to obtain the unfolded length deviation value of any point on the gear tooth profile at the same tooth width on each scanning line;

[0033] The specific calculation method for determining the deviation of the developed length at any point on the gear tooth profile using Lagrange interpolation is as follows:

[0034] 4-1. Select one point on each scanning line in the tooth direction. The selected points have the same tooth width. Substitute the actual deviation value of the selected points into the formula: x∈[0,+∞), where x is the unfolded length, δ is the deviation value, n is the number of scan lines in the tooth direction, i is a natural number between 1 and n, and j is a natural number between 1 and n, thus obtaining the deviation value relationship expression P(x) at any point of the tooth width;

[0035] 4-2, Using the method in 4-1, we obtain the expression for the deviation value of arbitrary tooth width of the gear tooth profile.

[0036] S5: As Figure 3 As shown, points on the gear tooth profile with the same theoretical unfolded length are used as tooth direction curves. Multiple different tooth direction curves 28 are selected according to the size of the gear being measured and the required detection accuracy. These tooth direction curves are distributed on both sides of the scanning line. The scanning line and adjacent tooth direction curves are equidistantly distributed, and the tooth direction curves between two scanning lines are also equidistantly distributed. The unfolded length deviation values ​​of the tooth direction curves and all points on the scanning line are identified, and lines are drawn connecting equal unfolded length deviation values, such as... Figure 4 As shown, the contour map of a single gear provides a more intuitive view of the microstructure of the machined gear, making it easier for staff to evaluate the machined gear in conjunction with the modification amount designed for the gear.

[0037] S6: Using step S4, obtain the unfolded length deviation value of any point of the driving gear and driven gear of the gear pair and determine the tooth direction curve. Superimpose the unfolded length deviation value of the tooth direction curve of the gear pair and the meshing position of the scanning line to obtain the superimposed value of the tooth direction curve and any point on the scanning line. This superimposed value corresponds to the tooth width.

[0038] S7: Identify the superimposed values ​​and connect equal superimposed values ​​to form a contour map to display the contact patch of the gear pair. The contour map is displayed on the tooth surface of the gear with a smaller tooth width, which facilitates the judgment of the edge load of the gear. The areas between different closed curves on the contour map are displayed in different colors to facilitate the evaluation by the staff.

[0039] S8: Based on the contour map of the gear pair contact patch obtained in S7, compare the contour map with the gear design drawing and then evaluate the gear pair condition in conjunction with the meshing direction 52 of the driving and driven teeth; if the contour map is basically stable and uniformly distributed along the meshing direction 52, such as Figure 5 As shown, the contact morphology of the gear pair is relatively reasonable; if the contour map as a whole contradicts the meshing direction 52, or is biased to one side of the meshing direction 52, such as Figure 6 As shown, the contact morphology of the gear pair is poor.

[0040] This invention provides a method for evaluating gear pair contact patterns. It not only displays the contact pattern of gear pairs using contour maps, enabling rapid and accurate assessment of gear pair contact conditions, but also showcases the microscopic morphology of individual gears through contour maps. This allows for evaluation of machining quality, gear strength, and assessment of the risk of NVH (noise, vibration, and harshness) defects, offering high evaluation efficiency and accuracy. Compared to existing technologies, this method more intuitively displays the gear tooth profile and gear pair contact patterns, allowing operators to quickly and accurately assess gear machining quality and gear pair fit using contour maps.

[0041] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications made to the present invention by those skilled in the art without departing from the spirit of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for evaluating contact patterns in a gear pair, characterized in that, Includes the following steps: S1: Based on the designed gear tooth profile shape, establish a three-dimensional model of the theoretical parameters, and calculate the unfolded length of any point on the theoretical tooth profile; S2: Scan the actual gear tooth profile that has been machined. The scanning lines are multiple scanning lines on the tooth surface in the tooth direction, and the actual unfolded length of any point on the scanning line is obtained. S3: The computer receives the actual unfolded length of any point on the scan line and maps it to the 3D model. It calculates the difference between the actual unfolded length and the theoretical unfolded length of each point on the scan line, obtains the deviation value of the unfolded length of each point, and stores it in the computer. S4: Use Lagrange's polynomial interpolation method to obtain the unfolded length deviation value of any point on the gear tooth profile at the same tooth width on each scanning line; S5: Select multiple different tooth direction curves as required, identify the unfolded length deviation values ​​of all points on the tooth direction curves and the scan line, connect the equal unfolded length deviation values ​​to obtain the contour map. S6: Use step S4 to obtain the unfolded length deviation value of any point of the driving gear and driven gear of the gear pair and determine the tooth direction curve. Superimpose the unfolded length deviation value of the tooth direction curve of the gear pair and the meshing position of the scanning line to obtain the superimposed value of the tooth direction curve and any point on the scanning line. S7: Identify the superimposed values ​​and connect equal superimposed values ​​to form a contour map to display the contact spots of the gear pair; S8: Evaluate the gear pair based on the contour map obtained in S7.

2. The method for evaluating contact patterns of a gear pair according to claim 1, characterized in that: The theoretical parameters include the number of teeth, module, pressure angle, helix angle, displacement coefficient, addendum circle diameter, dedendum circle diameter, and center distance of the gear pair.

3. The method for evaluating the contact pattern of a gear pair according to claim 1, characterized in that: The scan line also includes a positioning scan line located at the midpoint of the tooth width and parallel to the theoretical involute.

4. The method for evaluating gear pair contact patterns according to claim 1, characterized in that: The scan lines are all located between the tooth root and the tooth tip and are distributed at equal intervals. The theoretical unfolded length of all points on the same scan line is the same.

5. The method for evaluating contact patterns of a gear pair according to claim 1, characterized in that: The tooth profile curves are distributed on both sides of the scan line. The scan line and the adjacent tooth profile curves are equidistantly distributed, and the tooth profile curves between two scan lines are also equidistantly distributed. The number of tooth profile curves is determined according to the size of the gear being tested and the required detection accuracy.

6. The method for evaluating contact patterns of a gear pair according to claim 1, characterized in that: The regions between different closed curves on the contour map are displayed using different colors.

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