Tooth profile measurement method and tooth profile measurement device

Abstract

To provide a non-contact type measurement optical system capable of drastically shortening a measurement time of a gear, to eliminate the need for screwing into a gap for a rotating gear and searching for a tooth surface, and to prevent shadow from occurring during optical measurement due to tooth form geometry.SOLUTION: A method comprising a step of measuring the geometry of a tooth form (8) with an optical measurement system (4), can adjust the number of apertures of the optical measurement system (4), and adjust and / or increase or decrease the number of apertures of the optical measurement system (4) according to at least one geometric parameter of the tooth form (8) to be measured.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a tooth profile measurement method and a tooth profile measurement device.

Background Art

[0002] Optical measurement systems are becoming increasingly relevant in gear metrology as they approach the accuracy of tactile measurement systems and often operate much faster than tactile measurement systems.

Summary of the Invention

Problems to be Solved by the Invention

[0003] Tactile pitch measurement is one of the standard measurement tasks in gear analysis and gear evaluation. Here, for example, for an involute tooth profile, all distances between involutes are measured on the pitch diameter and at a predetermined measurement height on both the left and right sides of all teeth. There is a distinction between two tactile measurement methods, namely pitch measurement via a point accurately probed on the pitch diameter and measurement of the cross-section of the flank line on the pitch diameter involving averaging of subsequent individual measurement points. Measurement based on the flank line provides a more robust result but at the cost of longer measurement time.

[0004] Subsequently, the measurement results are compared with the reference distances of the reference geometry of the tooth profile, for example, in accordance with general standards such as VDE or company standards or DIN, ISO or AGMA. Here, it is possible to have measurements not directly on the deviating diameter, i.e., the pitch circle diameter, and measurements at one or more measurement heights.

[0005] The measurement time for tactile pitch measurement is long, especially for tooth trace-based measurements, because each cross-section of the tooth trace must be measured accurately with the correct diameter and height for each tooth. The tactile measurement probe must enter each tooth space without collision, make contact with each tooth surface (tooth flanks), and complete two measurements in each tooth space. After measurement in the tooth space, the probe is retracted, the gear rotates one tooth pitch, and the measurement process is repeated in the next space.

[0006] In principle, such pitch measurements can be performed using non-contact optical measurement systems, which require much shorter measurement times. In this case, the gear rotates continuously in front of the optical system, eliminating the need to screw into gaps or explore tooth surfaces. However, the geometry of the tooth profile can cause shadows during optical measurement, preventing the required image quality from being achieved. This applies not only to optical pitch measurement but also to optical measurement of other geometric features of the tooth profile, where shadows can occur during measurement.

[0007] Against this backdrop, the present invention is based on the technical problem of identifying a method and apparatus that enables improved optical gear measurement. [Means for solving the problem]

[0008] The technical problems described above are solved by the independent claims in each case. Further embodiments of the present invention are derived from the dependent claims and the following description.

[0009] According to a first aspect, the present invention relates to a method having the step of measuring the geometry of a tooth profile by an optical measuring system, wherein the numerical aperture of the optical measuring system is adjustable and adapted according to at least one geometric parameter of the tooth profile to be measured. Alternatively or additionally, the numerical aperture of the optical measuring system is increased and / or decreased according to at least one geometric parameter of the tooth profile to be measured.

[0010] By adjusting or adapting the numerical aperture to the tooth profile geometry, shadows, particularly during optical measurements, can be completely avoided or reduced. Therefore, although the maximum possible measurement resolution may decrease for optical measurements due to the reduced numerical aperture, essentially complete imaging with sufficient backscatter illumination intensity is guaranteed because shadows are completely avoided or reduced during optical measurements.

[0011] When the term "measurement of tooth profile geometry" is used, it specifically refers to the metrological determination of the actual values ​​of one or more geometric parameters of a tooth profile, such as profile shape, flank shape, number of teeth, outer diameter, tooth pitch, gap width, module, helix angle, spiral angle, tip cone, root cone, tip relief, root relief, end relief, profile crowning, and width crowning. For this purpose, for example, individual points on the tooth surface of a tooth profile and / or profile lines and / or tooth traces can be measured.

[0012] The adjustment and / or increase and / or decrease of the numerical aperture is carried out, in particular, based on at least one known baseline value of at least one geometric parameter of the tooth profile being measured. In actual operation, completely unknown tooth profiles are rarely measured. For example, data on the baseline geometry of a tooth profile is typically stored in data memory for measurements performed during production as part of the quality control process.

[0013] Adjusting the numerical aperture can be performed in an automated manner, particularly based on at least one known reference value of at least one geometric parameter of the tooth profile being measured. This reference value may be, for example, one or more geometric parameters of the tooth profile, such as outer diameter, number of teeth, helix angle, spiral angle, pitch direction, spiral direction, module, tooth pitch, or gap width.

[0014] The geometric parameters may be the tooth pitch or gap width of the tooth profile.

[0015] In particular, this is the tooth pitch at the height of the pitch circle diameter of the tooth profile, such as the normal pitch or face pitch on the pitch circle. Alternatively, the tooth pitch may be defined by the height of the tip circle diameter or root circle diameter of the tooth profile.

[0016] Similarly, the gap width of the tooth profile may be defined by the height of the pitch circle in the cross section perpendicular to the tooth or in the pressure surface cross section. Alternatively, the gap width may be defined by the height of the tip circle diameter or root circle diameter of the tooth profile.

[0017] The gap width is the distance between two adjacent tooth surfaces of opposing tooth profiles, for example, the distance between the left tooth surface of the first tooth and the right tooth surface of the second adjacent tooth. The gap width may be, for example, the tooth gap width at the height of the pitch circle diameter, or the tooth gap base width in the root region of the tooth profile. Furthermore, the gap width may be the tooth gap width at the height of the apical circle diameter.

[0018] The numerical aperture may be selected to be larger in tooth profiles with a larger tooth pitch than in tooth profiles with a smaller tooth pitch. In other words, a clear width of the tooth space is considered for specific measurement tasks, particularly to prevent or minimize shadowing during optical measurements.

[0019] One or more geometric parameters of the tooth profile may be considered to adjust the aperture, and in particular, one or more of the following parameters may be selected: profile shape, flank shape, number of teeth, outer diameter, tooth pitch, gap width, module, helix angle, spiral angle, tip cone, root cone, tip relief, root relief, end relief, profile crowning, width crowning, etc.

[0020] According to one embodiment of this method, it may be provided that the edge beam of the optical measurement system is not shadowed by one or more teeth of the tooth profile. The numerical aperture is increased or decreased to match the geometry of the tooth profile and / or so that the measurement point is fully imaged.

[0021] According to one embodiment of this method, it may be provided that the first tooth surface and / or first profile section of the tooth profile is measured with a larger numerical aperture than when measuring the second tooth surface and / or second profile section of the tooth profile. The numerical aperture may therefore be set to be larger or smaller depending on the tooth height at which the measurement points detected for each measurement section are located. When the measurement points are located near the tip of the tooth, they can be measured with a higher numerical aperture than measurement points located deeper in the tooth space, i.e., near the root of the tooth, in order to avoid or reduce shading.

[0022] Alternatively or additionally, adjustment of the numerical aperture along the measurement path during measurement may be provided. For example, the numerical aperture may be increased or decreased along the measurement path. For example, the numerical aperture may be increased or decreased stepwise or continuously along the measurement path.

[0023] Alternatively or additionally, the aperture can be provided to periodically increase and decrease over the rotation angle of the tooth profile. As the tooth profile being measured rotates, for example, in front of an optical measurement system during measurement, the tooth head, tooth surface, and root segment alternate sequentially. Thus, the aperture may be adjusted stepwise, for example, over two or more steps, or continuously.

[0024] Alternatively or additionally, the numerical aperture may be kept constant during optical measurement. For example, for a measurement task, the maximum possible numerical aperture may be determined so that no shadow occurs for any of the measured points to be detected. In other words, for each of the measured points to be detected, a respective maximum numerical aperture may be determined, and the minimum aperture may be selected from these values. It is true that some of the measured points may not be measured with the maximum possible aperture for these specific measured points. However, high imaging quality is guaranteed for all measured points.

[0025] In particular, the numerical aperture may be automatically adjusted.

[0026] According to one embodiment of this method, it may be provided that the numerical aperture for a measured point is set based on the light intensity detected by the image sensor, and in particular, the aperture is set so that the maximum intensity is detected at a constant illuminance of the light source.

[0027] Alternatively or additionally, it may be provided that the numerical aperture is determined computationally, in particular based on a predetermined reference geometry of the tooth profile and a predetermined measurement angle. If the reference geometry and the measurement angle, i.e., the inclination of the optical axis of the optical measurement system with respect to the measured tooth profile, are known, the numerical aperture may be adapted computationally, for example, so that the edge beam of the optical cone of the optical measurement system does not become shadowed during optical measurement. Furthermore, a defined tolerance range of the tooth profile may be added to the reference geometry as an allowable value taking it into account.

[0028] According to one embodiment of the tooth profile, the optical measurement system comprises a confocal sensor, and the geometry of the tooth profile is detected by confocal distance measurement, in particular by confocal chromatic distance measurement.

[0029] Alternatively or additionally, it may be provided that the geometry of the tooth profile is measured by a tactile measurement system.

[0030] In particular, it may be possible to perform measurements using both tactile and optical measurement systems. Specifically, individual measurement points detected by tactile methods may function as reference points or support points for evaluating optically measured measurement points.

[0031] According to a second aspect, the present invention relates to a method comprising the steps of measuring the geometry of a first tooth profile according to the method according to the present invention described above, and measuring the geometry of a second tooth profile according to the method according to the present invention described above, wherein the first tooth profile has a different geometry from the second tooth profile, the first tooth profile is measured at a first numerical aperture, the second tooth profile is measured at a second numerical aperture, and the first numerical aperture is different from the second numerical aperture.

[0032] For example, when measuring two sets of tooth profiles with different geometries sequentially using the same measuring instrument, the numerical aperture may be adjusted to suit the specific tooth profile in order to avoid or reduce shadowing during each optical measurement.

[0033] For example, the first and second tooth profiles may differ with respect to their module, helix angle, or other features that determine their respective geometries.

[0034] In a third aspect, the present invention relates to an apparatus for measuring a tooth profile, comprising an optical measuring system for measuring the geometry of a tooth profile, a receptacle for holding the tooth profile to be measured, and a controller for controlling the measurement sequence, wherein the controller is configured to carry out the method according to the present invention.

[0035] For example, the device may be a coordinate measuring machine, which is a gear measuring machine. The gear measuring machine may have a spindle for holding and rotating the tooth profile to be measured.

[0036] The gear measuring machine may have multiple CNC control axes.

[0037] An optical measuring system may be provided with a lens system in which the focal length is adjustable. Alternatively or additionally, the optical measuring system may have a lens in which the focal length is adjustable, a so-called adaptive lens.

[0038] The device may have a tactile measurement system for measuring the geometry of the tooth profile. Alternatively or additionally, the optical measurement system may have a confocal sensor, in particular a confocal chromatic sensor. [Brief explanation of the drawing]

[0039] The present invention will be described in more detail below with reference to the drawings illustrating exemplary embodiments. The drawings are schematically shown below. [Figure 1] The present invention relates to a device for measuring tooth shapes. [Figure 2] Optical measurement with shadows. [Figure 3] Optical measurement without citation. [Figure 4] Optical measurement system. [Figure 5A] An optical measurement system with adaptive lenses. [Figure 5B] An optical measurement system having a lens system. [Modes for carrying out the invention]

[0040] Figure 1 shows a device 2 for measuring tooth profiles. Device 2 has an optical measurement system 4 for measuring the geometry of the tooth profile. Device 2 has a tactile measurement system 5 for measuring the geometry of the tooth profile. Device 2 has a receptacle 6 for holding the tooth profile 8 to be measured and a controller 10 for controlling the measurement sequence.

[0041] The controller 10 is configured to perform a method according to the present invention, which includes a step of measuring the geometry of a tooth profile 8 by an optical measurement system 4, and can set the numerical aperture of the optical measurement system 4, and adjust the numerical aperture of the optical measurement system to suit and / or increase or decrease according to at least one geometric parameter of the tooth profile 8 to be measured.

[0042] At least one reference value for at least one geometric parameter is stored in a data memory 11 which is part of the controller 10 or accessible by the controller 10. The reference value may be, for example, a reference value known from the tooth profile design of the tooth profile to be measured.

[0043] The tooth profile may be rotated around axis C. The optical measurement system 4 may be translated in the x, y, and z directions. The axis movement may be controlled by the controller 10.

[0044] Figure 2 shows the optical measurement of the tooth profile 8 using the optical measurement system 4. Here, the edge beam 12 of the optical cone 14 is shadowed by the tooth tips 16 of the teeth 18 of the tooth profile 8 and therefore does not contribute to imaging the measurement point 20. According to the present invention, such shadowing is avoided, in particular, partially or completely.

[0045] The numerical aperture is therefore adapted to the geometry of the tooth profile 8 shown in Figure 3, taking into account, for example, the tooth pitch 15 and / or gap width 13 of the tooth profile 8. As can be seen from Figure 3, the numerical aperture of the optical measurement system 4 is reduced so that the edge beam 12 of the optical cone 14 is no longer shadowed by the tooth tip 16 of the tooth 18.

[0046] The optical measurement system 4 is a device for confocal chromatic distance measurement.

[0047] The numerical aperture NA of the optical system 4 is defined in a known way as the product of the refractive index of the sine of half the aperture angle 24 on the target side of the optical system 4, which is 1 for air, for example (Figure 4).

[0048] To reduce the numerical aperture, the distance 22 from the optical fiber 30 to the collimator lens 26 may be reduced, thereby reducing the illuminance of the focusing lens 28. In order to still maximize the optical output, the focal point of the collimator lens 26 must be on the fiber output 32 of the optical fiber 30 coupled to the light source 34 and must be harmonized with the numerical aperture of the optical fiber 30.

[0049] For this purpose, the collimator lens 26 may be designed as an adaptive lens 26 with adjustable focal length, as shown in Figure 5A.

[0050] Alternatively or additionally, this can be achieved by a variable focal length lens system 36, as shown in Figure 5B.

Claims

1. A method comprising the step of measuring the geometry of a tooth profile (8) using an optical measurement system (4), The numerical aperture of the optical measurement system (4) is adjustable. A method for adjusting and / or increasing or decreasing the numerical aperture of the optical measurement system (4) according to at least one geometric parameter of the tooth profile (8) to be measured.

2. The aforementioned geometric parameter is the tooth pitch (15) or gap width (13) of the tooth profile (8). The method according to claim 1.

3. The edge beam (12) of the optical measurement system (4) is not obscured by the teeth (18) of the tooth profile (8). The method according to claim 1 or 2.

4. The first tooth surface and / or first profile section of the tooth profile (8) is measured with a larger numerical aperture than when measuring the second tooth surface and / or second profile section, and / or The numerical aperture is adjusted along the measurement path during the measurement. The method according to any one of claims 1 to 3.

5. The numerical aperture of the measurement point is set based on the light intensity detected by the image sensor, and in particular, the aperture is set such that the maximum intensity detected by the image sensor is detected at a constant illuminance of the light source (34), and / or The number of apertures is determined by calculation, particularly based on a predetermined reference geometry and a predetermined measurement angle of the tooth profile (8). The method according to any one of claims 1 to 4.

6. The optical measurement system (4) has a confocal sensor, The geometry of the tooth profile (8) is detected by confocal distance measurement and / or The geometry of the tooth profile (8) is measured by a tactile measurement system (5). The method according to any one of claims 1 to 5.

7. The geometry of the first tooth profile is measured according to the method according to any one of claims 1 to 6. The geometry of the second tooth profile is measured according to the method according to any one of claims 1 to 6. A method having a step, The first tooth profile has a different geometry from the second tooth profile. The first tooth profile is measured at the first numerical aperture, The second tooth profile is measured using a second numerical aperture. A method wherein the first numerical aperture is different from the second numerical aperture.

8. A device for measuring tooth shapes, It has an optical measurement system (4) for measuring the geometry of the tooth profile (8), It has a receptacle (6) that holds the tooth shape (8) to be measured, It has a controller (10) for controlling the measurement sequence, An apparatus wherein the controller is configured to perform the method according to one of claims 1 to 7.

9. The optical measurement system (4) has a lens system (36) with adjustable focal length, and / or The optical measurement system (4) has a lens (26) with an adjustable focal length. The apparatus according to claim 8.

10. The tactile measurement system (5) is provided for measuring the geometry of the tooth profile (8), and / or The optical measurement system (4) has a confocal sensor. The apparatus according to claim 8 or 9.

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