Optical gear measurement method and apparatus

Abstract

To provide a method and a device which enable improved optical measurement of a toothing of a component.SOLUTION: A method includes the step of: measuring a toothing (4) of a component (2) by an optical measuring system (18), wherein measuring points are detected; and evaluating the measuring points, wherein the step of evaluating the measuring points has at least the following steps: grouping the measuring points into flank groups by filtering; modeling profile segments from the measuring points of the flank groups, wherein each flank group is assigned a profile segment; and determining one or more geometric parameters of the toothing on the basis of the profile segments.SELECTED DRAWING: Figure 2B

Description

[Technical Field]

[0001] The object of the invention is a method comprising the following method steps: providing a component, the component having a tooth profile with a predetermined nominal geometry; providing a measuring device, the measuring device having an optical measuring system; measuring the tooth profile of the component by means of the optical measuring system, whereby measurement points are detected; and evaluating the measurement points. The invention further relates to an apparatus for carrying out such a method. [Background technology]

[0002] Optical measurement systems are becoming increasingly important in gear measurement technology because they are increasingly approaching the accuracy of tactile measurement systems and often operate much faster than tactile systems.

[0003] Tactile pitch measurement is one of the standard measuring tasks in gear analysis and evaluation. Here, for example, in the case of an involute tooth profile, all distances between the involutes are measured on the left side of every tooth and on the right side of every tooth, in each case on the pitch diameter and at a predefined measurement height. A distinction is made between two tactile pitch measurement methods: pitch measurement by point probing, which measures exactly at the pitch diameter, and measurement methods in which a section of the flank line is measured at the pitch diameter and then the individual measurement points are averaged. Using the flank line requires longer measurement times but provides more reliable measurement results.

[0004] The measurement results are then compared with reference distances of a reference geometry of the tooth profile and evaluated, for example according to VDE or company standards or general standards such as DIN, ISO or AGMA. Measurements of deviating diameters, i.e. diameters not directly on the pitch diameter, and at one or more measurement heights are possible.

[0005] The measurement time for tactile pitch measurement is relatively long, especially for flank line-based measurements, because each section of the flank line must be measured for each tooth with the correct diameter and height. The tactile probe must enter each tooth space without collision, contact each tooth flank, and complete two measurements for each tooth space. After completing the measurement within a tooth space, the probe is retracted, the gear is rotated one tooth, and the next tooth space is measured.

[0006] Such pitch measurements can in principle be carried out with a non-contact optical measuring system with much shorter measurement times, in which case the gear rotates continuously in front of the optical system and no gap penetration or tactile probing of the flanks is necessary. However, known evaluation strategies used to evaluate tactile measurements lead to deviating or falsified results in relation to optical measurements, since the recorded measurement points of tactile measurements and those of optical measurements differ significantly from each other, especially in terms of their number and quality.

[0007] Tactile measurement systems, for example, have such high accuracy for each specific measurement point that one or a few measurement points are often sufficient to determine a geometric feature, whereas optical measurement systems, while having lower accuracy for each individual measurement point, detect significantly more measurement points.

[0008] Additionally, optical and tactile measurement systems differ in their interaction with the part being measured. For example, Figure 1A shows a schematic representation of the measurement of a surface profile P having surface structures in the range of about 10 micrometers as indicated by a tip. In this case, the focused beam FS of the optical measurement system has a focal diameter d FS is only 20 micrometers, for example, so that the measurement is performed within the surface profile P. In contrast, in the tactile measurement of the same surface profile P according to FIG. 1B, the diameter d of the sensing ball K used for sensing is K is, for example, 500 μm and the focal diameter dFS , resulting in smoothing or morphological filtering. Furthermore, tactile measurements do not detect dust or airborne particles, which in optical measurements can result in measurement points far away from the surface being measured.

[0009] Therefore, an evaluation strategy optimized for measuring points with a tactile measuring system, if applied to measuring points recorded with an optical measuring system, will lead to deviations or falsification of the measurement results, making it difficult to compare optical and tactile measurement results.

[0010] Against this background, the present invention is based on the technical problem of providing a method and an apparatus which allows an improved optical measurement of the tooth profile of a part, in which in particular an improved intercomparability with the measurement results of tactile measurements can be achieved. Summary of the Invention

[0011] The above mentioned technical problem is solved by a method according to claim 1 and a device according to claim 10. Further embodiments of the invention are set out in the dependent claims and the following description.

[0012] According to a first aspect, the present invention relates to a method comprising the following method steps: providing a part, the part having a tooth profile with a predetermined reference geometry; providing a measuring device, the measuring device having an optical measuring system; measuring the tooth profile of the part by means of the optical measuring system, wherein measurement points are detected; and evaluating the measurement points, characterized in that the evaluation of the measurement points comprises at least the following steps: grouping the measurement points into flank groups by filtering, modeling profile segments from the measurement points of the flank groups, wherein each flank group is assigned a profile segment, and determining one or more geometric parameters of the tooth profile based on the profile segments.

[0013] Filtering the measurement points and grouping the results allows for improved modeling of the profile segment, since only a subset of the measurement points is evaluated instead of all of them. The modeled profile segment therefore more accurately reflects the actual shape of the part, allowing for a more accurate determination of one or more geometric parameters of the tooth profile.

[0014] When the term "profile segments" is used in this document, they may extend at least partially in the profile direction and / or flank direction of the teeth of the tooth profile. In particular, the profile segments may represent the profile lines and / or flank lines of the teeth of the tooth profile. In particular, the profile segments may map the profile lines of the teeth of the tooth profile. In particular, the profile segments may map the flank lines of the teeth of the tooth profile.

[0015] When a tooth profile is referred to in this document, it may be a toothed gear pinion or wheel. The tooth profile may therefore be arranged for torque and speed transmission and conversion. Alternatively, the tooth profile may be part of a spline.

[0016] The tooth profile may be an involute or cycloidal tooth profile. The tooth profile may be a rack and pinion or a Wild-Haber-Novikoff tooth profile.

[0017] Grouping the measurement points into flank groups by filtering may include the following method steps: radial filtering of the measurement points, in which a plurality of measurement points of a flank group, in particular all measurement points of a flank group, are located between a predetermined minimum radius and a predetermined maximum radius. In this way, for example, head and / or root regions of the tooth profile can be masked out, screened out, or deleted, unless they are to be taken into account for determining one or more geometric parameters of the tooth profile. In particular, the maximum radius may be smaller than the radius of the tip circle of the tooth profile. The minimum radius may be larger than the radius of the root circle of the tooth profile.

[0018] The grouping of measurement points into flank groups by filtering may alternatively or additionally comprise the following method steps: a profile-specific filtering step of the measurement points, in which a plurality of measurement points of a flank group, in particular all measurement points of a flank group, are each at a minimum distance not exceeding a predetermined distance from a predetermined nominal geometry of the tooth profile. Thus, as long as the minimum distance of a measurement point to the predetermined nominal geometry of the tooth space is greater than the predetermined distance, the measurement point is masked out, screened out, not assigned to a flank group, or deleted. In other words, a band or envelope can be placed around the flank of the nominal geometry, and all measurement points within the band or envelope are assigned to the respective flank group. In particular, profile-specific filtering makes it possible to screen out, hide, or delete measurement points that result from disturbance variables, such as dust, suspended particles, impurities, etc.

[0019] It may be provided that both radial filtering and profile-specific filtering are performed. In particular, the profile-specific filtering may be performed after the radial filtering.

[0020] Also, profile-specific filtering may be performed before radial filtering, or profile-specific filtering and radial filtering may be performed at least partially simultaneously.

[0021] The grouping of measurement points into flank groups by filtering may alternatively or additionally comprise the following method step: a kinematic filtering step of the measurement points, in which a plurality of measurement points of a flank group, in particular all measurement points of a flank group, fulfill the condition that, at the time of detection of each measurement point, the magnitude of acceleration of the machine axes of the measuring device performing the measurement operation is smaller than a predetermined threshold. In particular, measurement points detected at the start or end of the measurement in a state where one or more machine axes are more strongly accelerated and / or jerking occurs can be masked out, screened out, or deleted in this way. In other words, the run-in and / or run-out of the measurement can be masked out, screened out, or deleted. In particular, at the time of detection of each measurement point, no measurement points in the flank group have a magnitude of acceleration of the machine axes performing the measurement operation that is greater than a predetermined threshold.

[0022] The grouping of the measurement points into flank groups by filtering may alternatively or additionally comprise the following method step: a qualitative filtering step of the measurement points, in which a plurality of measurement points of a flank group, in particular all measurement points of a flank group, fulfill the condition that during the imaging of the respective measurement point, the exposure time does not fall below a predetermined exposure time and / or the intensity does not fall below a predetermined intensity. In this way, measurement points that have not been reliably imaged can be masked out, culled out or deleted.

[0023] In particular, there are cases where the brightness of each measurement point must not fall below a predetermined average brightness during imaging.

[0024] The exposure time and the brightness can also be calculated as a coefficient, for example in the simplest case as a product or a sum or a quotient, with the result that the quality of the image of the respective measurement point can be evaluated. In particular, it may be the case that several measurement points of a flank group, in particular all measurement points of the flank group, satisfy the condition that the coefficient does not fall below a predetermined minimum value or that the coefficient is within a predetermined range during the imaging of the respective measurement point.

[0025] The grouping of measurement points into flank groups by filtering may include the following test step: checking whether the number of flank groups corresponds to twice the number of teeth on the tooth profile. If the filtering produces a number of flank groups that does not correspond to twice the number of teeth, the filtering should be adjusted. This is because, after filtering, exactly one flank group with measurement points should be assigned to each tooth flank of the tooth profile. As long as the number of flank groups produced by the filtering does not correspond to twice the number of teeth on the tooth profile, the filtering may be adjusted and the test step may be performed again.

[0026] Alternatively or additionally, the grouping of measurement points into flank groups by filtering may comprise a test step of checking whether the number of measurement points in the respective flank group exceeds a predetermined minimum number. In particular, the subsequent modeling step of the profile segments can be meaningfully carried out only if there is a sufficient number of measurement points for each flank group. As long as the number of measurement points in the respective flank group is below the predetermined minimum number, the measurement may be repeated with modified measurement parameters and the number of measurement points may be checked again.

[0027] Alternatively or additionally, the grouping of measurement points into flank groups by filtering may comprise a test step of checking whether the measurement points of the respective flank group have a predetermined distribution. It can thus be checked to what extent adjacent points exceed a maximum distance from each other and / or fall below a minimum distance from each other. The aim is therefore to achieve a measurement point distribution that is as homogeneous as possible. If the distribution is too uneven, the measurement parameters can be changed and the measurement can be repeated and the distribution checked again.

[0028] One or more of the aforementioned testing steps may be performed prior to modeling, which may improve subsequent modeling steps.

[0029] According to one embodiment of the method, modeling of profile segments from measurement points of flank groups, to each flank group a profile segment is assigned, comprises one of the following method steps: modeling at least one profile segment as a high-order mathematically non-linear function, or modeling a number of profile segments each as a high-order mathematically non-linear function, or modeling all profile segments each as a high-order mathematically non-linear function.

[0030] Thus, curve or profile segments can be modeled from the measured points by equalization and / or interpolation calculations, and each of these curve or profile segments can be described as a high-order mathematical non-linear function.

[0031] In this document, the term high-order nonlinear function specifically refers to quadratic functions, polynomial functions, power functions, etc. The selection of the appropriate function depends on the type of tooth profile, i.e., whether the tooth profile is an involute, cycloid, rack and pinion, or Wild-Haber-Novikoff.

[0032] According to one embodiment of the method, the step of modeling profile segments from measurement points of the flank groups may comprise a plausibility check by the following method steps, in which each flank group is assigned a profile segment: creating a left averaged compensation profile segment from the profile segments of the left flank group; and checking the deviation of at least one profile segment of the left flank group from the left averaged compensation profile segment. Thus, the left averaged compensation profile segment may be formed by averaging or superimposing all profile segments of the left flank group. If the deviation exceeds a predetermined threshold, adjustment of filtering and / or adjustment of measurement parameters may be performed.

[0033] The measurement parameters are in particular the axial positions, axial velocities, axial accelerations of the machine axes performing the measurement operation and / or parameters of the optical measurement device, such as exposure time, scanning frequency, illumination intensity, measurement angle, focal diameter, etc.

[0034] Alternatively or additionally, according to one embodiment of the method, the modeling of the profile segments from the measurement points of the flank groups may comprise a likelihood check by the following method step, in which each flank group is assigned a profile segment: checking the deviation of at least one profile segment of the left flank group from another profile segment of the left flank group. If the deviation exceeds a predetermined threshold, an adjustment of the filtering and / or an adjustment of the measurement parameters may be performed.

[0035] Alternatively or additionally, according to one embodiment of the method, the modeling of the profile segments from the measurement points of the flank groups may comprise a likelihood check by the following method steps, in which each flank group is assigned a profile segment: creating a right-averaged compensation profile segment from the profile segments of the right flank group; and checking the deviation of at least one profile segment of the right flank group from the right-averaged compensation profile segment. Thus, the right-averaged compensation profile segment may be formed by averaging or superimposing all profile segments of the right flank group. If the deviation exceeds a predetermined threshold, adjustment of the filtering and / or adjustment of the measurement parameters may be performed.

[0036] Alternatively or additionally, according to one embodiment of the method, the modeling of the profile segments from the measurement points of the flank groups may comprise a likelihood check by the following method step, in which each flank group is assigned a profile segment: checking the deviation of at least one profile segment of the right flank group from another profile segment of the right flank group. If the deviation exceeds a predetermined threshold, an adjustment of the filtering and / or an adjustment of the measurement parameters may be performed.

[0037] Alternatively or additionally, according to one embodiment of the method, the modeling of the profile segments from the measurement points of the flank groups may comprise a likelihood check by the following method step, in which each flank group is assigned a profile segment: checking the deviation of the left averaged compensated profile segment from a predetermined reference geometry. If the deviation exceeds a predetermined threshold, an adjustment of the filtering and / or an adjustment of the measurement parameters may be performed.

[0038] Alternatively or additionally, according to one embodiment of the method, the modeling of the profile segments from the measurement points of the flank groups may comprise a likelihood check by the following method step, in which each flank group is assigned a profile segment: checking the deviation of the right averaged compensation profile segment from a predetermined reference geometry. If the deviation exceeds a predetermined threshold, an adjustment of the filtering and / or an adjustment of the measurement parameters may be performed.

[0039] Alternatively or additionally, according to one embodiment of the method, the modeling of the profile segments from the measurement points of the flank groups may comprise a likelihood check by the following method step, in which each flank group is assigned a profile segment: checking the deviation of at least one profile segment from a predetermined reference geometry and / or from a compensation shape, which is determined from the profile segments of the flank group. For example, the compensation shape may be determined from the profile segments of the flank group using a least-squares method. If the deviation exceeds a predetermined threshold, adjustment of the filtering and / or adjustment of the measurement parameters may be performed.

[0040] Alternatively or additionally, according to one embodiment of the method, the modeling of profile segments from the measurement points of the flank groups comprises a likelihood check by the following method step, in which each flank group is assigned a profile segment: checking the deviation between a first profile segment of a tooth of the tooth profile of the first measurement and a second profile segment of the same tooth profile of the second measurement. That is, as long as one or more teeth are measured or modeled twice or more than once, it may be checked whether the model is closed, i.e. whether the model can be repeatedly mapped onto itself.

[0041] According to one embodiment of the method, the three-dimensional measurement points of at least one flank group, several flank groups or all flank groups may be projected onto a two-dimensional plane, in particular before the profile segments are created, and modeling of the profile segments from the measurement points may be performed in the two-dimensional plane, in particular as two-dimensional profile segments.

[0042] When referring to a "three-dimensional measurement point," this means that three spatial coordinate values ​​are assigned to each measurement point, for example, x, y, and z values ​​in a Cartesian coordinate system xyz. By means of projection onto a two-dimensional plane, one of these values ​​becomes equal for all measurements and therefore has the same value for all measurements. For the projection, a known reference geometry of the tooth profile, such as the helix angle, can be taken into account, so that the projection plane corresponds, for example, to a profile or face, and / or the measurement point is projected along the assigned flank line of the reference geometry.

[0043] Alternatively, the three-dimensional profile segments of a flank group, the three-dimensional profile segments of multiple flank groups, or the three-dimensional profile segments of all flank groups may be projected onto a two-dimensional plane.

[0044] Tooth pitch is one of one or more geometric parameters of the tooth profile, and tooth pitch is a pitch measurement circle The pitch deviation may be one of one or more geometric parameters of the tooth profile, such as pitch single deviation, pitch total deviation, pitch jump, etc.

[0045] While the measurement points are being recorded, the part may be moved relative to the optical measurement system. In particular, the part may be rotated about an axis. In particular, the part may be rotated about an axis while the optical measurement system is stationary and / or displaced by one or more linear axes.

[0046] During detection of the measurement points, the part may be continuously moved relative to the optical measurement system, in particular the part may be continuously rotated about an axis while the optical measurement system is stationary and / or displaced about one or more linear axes.

[0047] The focal diameter of the optical measurement system may be less than 50 microns, especially less than 20 microns.

[0048] The optical measurement system may have a point sensor configured for optical distance measurement. In particular, individual measurement points can be measured one after the other by the point sensor. The individual measurement points can be recorded by the point sensor separately and independently from further measurement points. That is, the point sensor may be able to acquire a single measurement point without acquiring further measurement points. Each individual measurement point can be assigned three spatial coordinate values, i.e., an x-value, a y-value, and a z-value in, for example, a Cartesian coordinate system xyz.

[0049] A point sensor for optical distance measurement may have resolution in the depth direction.

[0050] For example, looking along the optical axis of a point sensor in a depth measurement range along the optical axis, the depth, i.e. the distance between the optically probed surfaces or tooth faces along the optical axis, can be measured in a given coordinate system, e.g. the distance to another geometric reference point such as the origin of the given coordinate system or the position of a lens, etc. It may also be the case that the distance measurement is made one-dimensionally along the optical axis and three-dimensional measurements are calculated based on the position of the optical measurement system.

[0051] That is, looking along the optical axis of the point sensor, it is possible to measure the distance between optically probed surfaces or tooth flanks along the optical axis of a particular coordinate system, e.g., the distance to the origin of a desired coordinate system or to another geometric reference point, such as the position of a lens, in a depth measurement range of several centimeters or millimeters, or even less than one millimeter. The distance information from the point sensor can be used to generate, in particular, three-dimensional measurement points, provided with information about the axial positions of a coordinate measuring machine equipped with the optical point sensor. The distance measurement can be a one-dimensional measurement along the optical axis, and the three-dimensional coordinates are calculated based on the position of the optical measuring machine.

[0052] The point sensor may operate according to one of the following measurement principles: laser triangulation, confocal or confocal-chromatic distance measurement, interferometric distance measurement, double frequency comb spectroscopy or similar principles.

[0053] An optical measurement system may have a single point sensor for optical distance measurement.

[0054] An optical measurement system may have two or more point sensors for optical distance measurement.

[0055] The point sensors may be arranged in a line or in a grid of rows and columns. One or more point sensors may operate according to one of the following measurement principles: laser triangulation, confocal or confocal-chromatic distance measurement, interferometric distance measurement, double-frequency comb spectroscopy, or similar principles. Each point sensor is therefore configured in the manner described above specifically for optical distance measurement, and in particular has a depth resolution along the optical axis. The point sensors can simultaneously record measurement values.

[0056] In particular, the optical measurement system does not have a camera.In particular, the optical measurement system does not have a camera for two-dimensional imaging.

[0057] In particular, the camera may not be used to create measurement points by image or pixel analysis or image processing. In particular, the camera for two-dimensional imaging is not used to obtain measurement points by image or pixel analysis or image processing.

[0058] Measurement points are recorded in particular on each tooth surface of the tooth system at a certain distance from the edge region of each tooth surface.

[0059] The optical axis of the optical measurement system may enclose an angle with the tooth surface that is not equal to 90° during acquisition of a measurement point on the tooth surface, i.e., the normal to the tooth surface originating from the measurement point may not be oriented parallel to the optical axis.

[0060] Multiple measurement points may be recorded on each tooth flank along the tooth width, i.e., along the tooth trace direction. Several measurement points may be recorded as individual measurement points on each tooth flank along the tooth width, i.e., along the tooth trace direction, with the first individual measurement point in the tooth trace direction being recorded before the second individual measurement point in the tooth trace direction.

[0061] The terms tooth surface and flank are used interchangeably herein.

[0062] The determination of one or more geometric parameters of the tooth profile based on the profile segments may be performed analogously to the evaluation of the tactile measurements and / or in evaluation software for evaluating the tactile measurements. Thus, filtering and modeling allow evaluation algorithms that are specifically optimized for tactile measurements to be applied to the results of the optical measurements.

[0063] According to a second aspect, the invention relates to an apparatus having a measuring device, which includes an optical measuring system, a holder for holding a component, and a control and evaluation unit adapted to perform the method according to the invention.

[0064] The measuring device may be a coordinate measuring device, which may have numerically controlled axes for implementing relative movements between the part to be measured and the optical measuring device before, during and / or after the measurement.

[0065] The coordinate measuring machine may have an axis of rotation for rotating the part to be measured about its own axis during measurement.

[0066] A coordinate measuring machine can have at least one linear axis, two or more linear axes, three or more linear axes, or exactly three linear axes for moving the optical measurement system relative to the part being measured.

[0067] In addition to the optical measuring system, the coordinate measuring machine can also have a tactile measuring system for touching the part with a measuring probe and measuring it tactilely. [Brief explanation of the drawings]

[0068] The invention is explained in more detail below with reference to the drawings which show exemplary embodiments, the drawings being in each case represented diagrammatically.

[0069] [Figure 1A] FIG. 1A is a schematic diagram of an optical measurement system. [Figure 1B] FIG. 1B is a schematic diagram of a tactile measurement system. [Figure 2A] FIG. 2A is a schematic diagram of the part being measured. [Figure 2B] FIG. 2B is a schematic diagram of an optical measurement of the part being measured in FIG. 2A. [Figure 3A] FIG. 3A is a schematic diagram of measurement points for optical measurement. [Figure 3B] FIG. 3B is an enlarged view of the measurement points of the optical measurement of FIG. 3A. [Figure 3C] FIG. 3C is a schematic diagram of the measurement points of the optical measurement of FIG. 3B before radial filtering. [Figure 3D] FIG. 3D is a schematic illustration of the measurement points of the optical measurement of FIG. 3B after radial filtering. [Figure 3E] FIG. 3E is a schematic diagram of the measurement points of the optical measurement of FIG. 3D before profile-specific filtering. [Figure 3F] FIG. 3F is a schematic diagram of measurement points of two flank groups of the optical measurement of FIG. 3D with profile-specific filtering. [Figure 3G] FIG. 3G is a schematic diagram of a modeled profile segment of two flank groups with reference geometry. [Figure 3H] FIG. 3H is a schematic diagram of a modeled profile segment. [Figure 3I] FIG. 3I is a schematic diagram of a modeled profile segment with reference geometry and compensation geometry. [Figure 3J] FIG. 3J is a schematic diagram of the measurement points of the flank group of the optical measurement of FIG. 3D after radial filtering and after profile-specific filtering. [Figure 4A] FIG. 4A is a schematic illustration of the deviation of the left profile segment relative to the left averaged compensated profile segment. [Figure 4B] FIG. 4B is a schematic illustration of the deviation of the right profile segment relative to the right averaged compensation profile segment. [Figure 4C]FIG. 4C is a schematic illustration of the deviation of a left profile segment relative to another left profile segment. [Figure 4D] FIG. 4D is a schematic illustration of the deviation of a right profile segment relative to another right profile segment. [Figure 4E] FIG. 4E is a schematic illustration of the deviation of the left averaged compensation profile segment from the reference geometry. [Figure 4F] FIG. 4F is a schematic illustration of the deviation of the right averaged compensation profile segment from the reference geometry. [Figure 5] FIG. 5 is a flow chart of a method according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0070] 2A shows a part 2 having a tooth profile 4. The part 2 is a helical spur gear 2 having an involute tooth profile 4. The tooth pitch of the tooth profile 4 is measured on the helical gear 2. For this purpose, the flank line portion 8 of the left flank 10 and the flank line 12 of the right flank 14 are measured on each tooth 6 of the tooth profile 4. By way of example, the flank line portion 8 on the left flank 10 and the flank line portion 12 on the right flank 14 of two adjacent teeth 6 are shown.

[0071] The spur gear 4 is measured (step (I)) by a measuring device 16 having an optical measuring system 18. During the measurement, the spur gear 2 rotates continuously about its own axis, which may in particular be aligned parallel to the z-axis of a Cartesian coordinate system xyz. It is clear that other Cartesian or polar coordinate systems may also be used.

[0072] In addition to the rotation about the z-axis, a linear relative translation in the z-direction occurs, resulting in a measurement path, shown by the dashed line, which covers the flank line portions 8, 12 of all teeth 6 to be measured, so that the optical measurement system 18 measures the complete tooth profile including the tip, flank and root of each tooth.

[0073] Thus, a plurality of measurement points 20 are obtained, which are shown in Fig. 3A in a cross-section. Fig. 3B is an enlarged view of the measurement points 20 of the tooth in a cross-section, in which a cross-section of a predetermined reference geometry 22 of the tooth profile 4 is shown in the form of a profile line 22. Each individual measurement point 24 of the plurality of measurement points 20 is defined by an x-value, a y-value and a z-value, i.e., its position in space according to the Cartesian coordinate system xyz.

[0074] In the next step, the measurement points 20 are grouped into flank groups 26 by filtering (step (II)).

[0075] 3C and 3D show the radial filtering of the measurement points 20, where all measurement points 20 of a flank group 26 are filtered out along a predetermined circle R having a minimum radius. MIN and a given circle R with maximum radius MAX It is placed between the circle R MIN The radius of the root circle FK of tooth profile 4 is larger than the radius of the circle R MAX The radius of the tip circle KK of the tooth profile 4 is smaller than the radius of the tip circle KK of the tooth profile 4. Furthermore, the pitch circle TK is drawn.

[0076] Applying the radial filtering shown in Figure 3C to the measurement points, R MIN and R MAX All measurement points outside the filter band enclosed by R can be filtered out, masked out, or deleted. The measurement points 20 remaining after radial filtering are shown in FIG. 3D. For more clarity, R MIN and R MAX Those regions of the reference profile 22 that do not lie between are also masked out.

[0077] This radial filtering already defines the number of flank groups 26, which may also be called contiguous measurements 26. The result of the radial filtering is further illustrated in Figure 3J, which shows the flank groups 26 for all teeth 6 of the tooth profile 4, where only two flank groups 26 are labeled.

[0078] Next, it is checked whether the number of flank groups 26 corresponds to twice the number of teeth of the tooth profile 4, which in this case is equal to 18 (step (III)). In this example, 36 flank groups have been generated, so the check reveals that the number of flank groups 26 corresponds to twice the number of teeth. Therefore, the radial filtering check is successful, and there is no need to adjust the radial filtering. Therefore, each individual left flank and each individual right flank of the tooth profile is associated with one flank group 26 and one continuous measurement section 26, respectively.

[0079] Furthermore, it is checked whether each of the respective flank groups has a sufficient number of measurement points and whether these measurement points of each flank group are sufficiently evenly distributed (step (III)).

[0080] In the next step, profile-specific filtering is performed, so that all measurement points 20 of each flank group 26 have a respective minimum distance, not exceeding a predetermined distance, to a predetermined reference geometry 22 of the tooth profile 4. This means that each of the flank groups 26 is filtered again (step (IV)), as will be explained below with reference to Figures 3E and 3F.

[0081] 3E and 3F, for each flank group 26, those measurement points 20 that are not within the band bounded by lines P+ and P− are culled out, masked out, or deleted, where P+ and P− are substantially offset profile lines of the target profile. Figure 3F shows the flank group 26 after applying profile-specific filtering.

[0082] Further, kinematic filtering of the measurement points 20 is performed, and all measurement points 20 of the flank group 26 satisfy the condition that, at the time of detection of each measurement point 20, the amount of acceleration of the mechanical axis A of the measuring device 16 performing the measurement operation is smaller than a predetermined threshold, the mechanical axis A being the spindle axis A performing the rotation, which extends along the z-axis and on which the part 2 is mounted (step (IV)).

[0083] In addition, qualitative filtering of the measurement points 20 is performed to ensure that all measurement points 20 in the flank group 26 do not fall below a predetermined exposure time and / or a predetermined brightness during imaging of each measurement point 24 (step (IV)).

[0084] Next, for each flank group 26, profile segments 28, 30 are modeled in each case as higher-order mathematically nonlinear functions, with the profile segment of the left flank 10 designated as profile segment 28 and the profile segment of the right flank 14 designated as profile segment 30 (FIGS. 3G, 3H). In the above manner, profile segments 28, 30 can be created for each height z to represent the measured tooth surface (step (V)).

[0085] Alternatively or additionally, the three-dimensionally defined measurement points of all flank groups may be projected onto a two-dimensional plane before filtering, and a modeling of a profile segment from the measurement points in the two-dimensional plane may be performed as a two-dimensional profile segment. Projecting the measurement points along the flank lines onto the two-dimensional plane allows for averaging according to the tactile measurement.

[0086] The determination of one or more geometric parameters of the tooth profile based on the profile segments 28, 30 can be performed similarly to the evaluation of the tactile measurements, in particular by evaluation software for evaluating the tactile measurements to determine the tooth pitch based on the flank lines 8, 12 and other geometric parameters of the tooth profile (step (vi)).

[0087] Alternatively or additionally, the flank lines 8, 12, respectively, can be generated directly by filtering and modeling using the methods described above.

[0088] Prior to evaluation and determination of the geometric parameters of the tooth profile, a likelihood check of the modeled profile segments can be performed using one or more of the following method steps:

[0089] Creating a left averaged compensation profile segment 280 from the profile segments 28 of the left flank group 26, and checking the deviation of at least one profile segment 28 of the left flank group 26 from the left averaged compensation profile segment 280 (FIG. 4A).

[0090] Creating a right averaged compensation profile segment 300 from the profile segments 30 of the right flank group 26 and checking the deviation of at least one profile segment 30 of the right flank group 26 from the right averaged compensation profile segment 300 (FIG. 4B).

[0091] Checking the deviation of at least one profile segment 28 of the left flank group 26 from another profile segment 28 of the left flank group 26 (FIG. 4C).

[0092] Checking the deviation of at least one profile segment 30 of the right flank group 26 from another profile segment 30 of the right flank group 26 (Figure 4D).

[0093] Checking the deviation of the left averaged compensation profile segment 280 from a predetermined reference geometry and checking the deviation of the right averaged compensation profile segment 300 from a predetermined reference geometry (FIG. 4E; FIG. 4F).

[0094] Checking the deviation of at least one profile segment 28, 30 from a predetermined reference geometry 22 and / or from a compensating shape 400, where the compensating shape 400 has been determined from the profile segments 28, 20 of the flank group 26 (FIG. 3I). In the schematic representation of FIG. 3I, the reference geometry 22 and the compensating shape 400 are depicted as coinciding, but in reality they do not coincide exactly. [Explanation of symbols]

[0095] 2 parts 4 Tooth profile 6 teeth 8 Frankline Club 10 Left Flank 12 Frankline Club 14 Right Flank 16 Measuring equipment 18 Optical Measurement System 20 measurement points 22 Reference Geometry 24 measurement points 26 Frank Group 28 Profile Segments 30 Profile Segments 280 Left Averaging Compensation Profile Segment 300 Right Averaging Compensation Profile Segment 400 compensation shape A Machine axis P Surface Profile FS Focused Beam K Sensing Ball d FS Focal diameter of the focused beam d K Sensing ball diameter TK pitch circle FK Root Circle KK Tip Circle R MIN Circle with minimum radius for radial filtering R MAX Circle with maximum radius for radial filtering First Limitation of P+ Profile-Specific Filtering A second limitation of P-profile-specific filtering xx axis yy axis zz axis

Claims

1. 1. A method comprising: providing a part (2), said part (2) having a tooth profile (4) with a predetermined reference geometry (22); providing a measurement device (16), said measurement device (16) including an optical measurement system (18); measuring the tooth profile (4) of the part (2) by the optical measuring system (18), wherein measurement points (20) are detected; and evaluating the measurement points (20), The step of evaluating the measurement points (20) comprises: grouping said measurement points (20) into flank groups (26) by filtering; modeling profile segments (28, 30) from the measurement points (20) of the flank groups (26), one profile segment (28, 30) being assigned to each flank group (26); determining one or more geometric parameters of the tooth profile based on the profile segments (28, 30); The method includes at least

2. The step of grouping the measurement points into flank groups by filtering comprises: - a step of radial filtering of the measurement points, wherein a plurality of the measurement points of the flank group, in particular all the measurement points of the flank group, are located between a predetermined minimum radius and a predetermined maximum radius; - a step of profile-specific filtering of the measurement points, wherein a plurality of the measurement points of the flank group, in particular all of the measurement points of the flank group, are each at a minimum distance not exceeding a predetermined distance from a predetermined reference geometry of the tooth profile; - a step of kinematic filtering of the measurement points, in which a plurality of the measurement points of the flank group, in particular all of the measurement points of the flank group, satisfy the condition that, at the time of detection of each measurement point, the amount of acceleration of the machine axis of the measuring device performing the measurement operation is smaller than a predetermined threshold value; - a step of qualitative filtering of the measurement points, in which a plurality of the measurement points of the flank group, in particular all of the measurement points of the flank group, satisfy the condition that during the imaging of each of the measurement points, the exposure time does not fall below a predetermined exposure time and / or the brightness does not fall below a predetermined brightness; The method of claim 1 , comprising one or more of:

3. The step of grouping the measurement points into flank groups by filtering comprises: checking whether the number of flank groups corresponds to twice the number of teeth of the tooth profile; checking whether the number of said measurement points in each flank group exceeds a predetermined minimum number; checking whether the measurement points of each flank group have a predetermined distribution; and one or more of the test steps: The testing step is in particular carried out before the modeling step, 3. The method according to claim 1 or 2.

4. said modeling a profile segment from said measurement points of said flank group comprising: modeling at least one profile segment as a high-order mathematical non-linear function; modeling each of several profile segments as a high-order mathematical nonlinear function; modeling every profile segment as a high-order mathematical nonlinear function; and A profile segment is assigned to each flank group, The method according to any one of claims 1 to 3.

5. modeling a profile segment from the measurement points of the flank group; creating a left averaging compensation profile segment from the profile segments of the left flank group and checking the deviation of at least one profile segment of the left flank group from the left averaging compensation profile segment; checking the deviation of at least one profile segment of the left flank group from another profile segment of the left flank group; creating a right averaging compensation profile segment from the profile segments of the right flank group and checking the deviation of at least one profile segment of the right flank group from the right averaging compensation profile segment; checking the deviation of at least one profile segment of the right flank group from another profile segment of the right flank group; checking the deviation of the left averaged compensation profile segment from a specified reference geometry; checking the deviation of the right averaged compensation profile segment from a specified reference geometry; - checking the deviation of at least one profile segment from a predetermined reference geometry and / or from a compensation shape, said compensation shape being determined from said profile segments of said flank group; checking the deviation between a first profile segment of a tooth of the tooth profile of the first measurement and a second profile segment of the same tooth profile of the second measurement; The method of any one of claims 1 to 4, further comprising a likelihood checking step with one or more of:

6. If the deviation exceeds a predetermined threshold, the filtering and / or measurement parameters are adjusted. The method of claim 5.

7. three-dimensional measurement points of at least one, some or all of the flank groups are projected onto a two-dimensional plane, in particular before the profile segments are created, and said modeling of the profile segments from said measurement points is carried out in said two-dimensional plane, in particular as two-dimensional profile segments, or The three-dimensional profile segments of the flank group, some of the flank group, or all of the flank group are projected onto a two-dimensional plane; The method according to any one of claims 1 to 6.

8. the tooth pitch is one of the one or more geometric parameters of the tooth profile, and the tooth pitch is determined on a pitch measurement circle; and / or Pitch deviation is one of the one or more geometric characteristics of the tooth profile. The method according to any one of claims 1 to 7.

9. the part is continuously moved relative to the optical measurement system during acquisition of the measurement points; and / or the focal diameter of the optical measurement system is 50 micrometers or less, in particular 20 micrometers or less, and / or determining one or more geometric parameters of the tooth profile based on the profile segments is performed similarly to the evaluation of a tactile measurement and / or in evaluation software for the evaluation of the tactile measurement, The method according to any one of claims 1 to 8.

10. 10. An apparatus comprising a measuring device, wherein the measuring device comprises an optical measuring system, has a holder for holding a part, and has a control and evaluation unit adapted to perform the method according to any one of claims 1 to 9.

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