Method for determining the expected noise emissions of a gear pair

Abstract

The invention relates to a method for determining the expected noise emissions of a gear pair, in which method the tooth flanks of a gear of the pair are measured and from the measurement data thereby obtained the deviation of the measured tooth flank surfaces from a predefined target profile of this surface is determined, and in which method on the basis of this deviation a simulation in the form of a contact analysis under load is carried out for the gear pair, wherein the contact analysis is based not on the deviation as a whole but rather on only a portion of the deviation specifically selected in the complementary space.

Description

[0001] METHOD FOR DETERMINING THE EXPECTED NOISE EMISSIONS OF A GEAR PAIR

[0002] The invention lies in the field of transmission and gearing technology. It is well known that the meshing of two torque-transmitting gears, i.e., a gear pair, in a transmission creates the risk of unwanted noise emissions, particularly in gear drives of electric vehicles. The current strategy of vehicle manufacturers is essentially to demand high to very high quality for the production of gears according to ISO 1328, since high precision of the gears used is known to not only increase service life but also improve noise through reduced vibration excitation (so-called NVH, noise vibration-harshness performance).

[0003] There are numerous factors influencing noise development, and when designing a gear pair for a gearbox, unwanted noise can still occur despite the required high quality. It is quite possible that after designing and manufacturing the gears, which are within the desired tolerances, simulation, or practical testing of the gearbox under load, unwanted noise development is detected through contact analysis.

[0004] In this respect, the invention specifically relates to a method for determining the expected noise emissions of a gear pair, in which the tooth flanks of one gear of the pair are measured and the deviation of the measured tooth flank surfaces from a predetermined target profile of this surface is determined from the measurement data obtained, and in which a simulation in the form of a contact analysis under load is carried out for the gear pair on the basis of this deviation.

[0005] Due to the above-mentioned problems, the invention is based on the object of contributing to providing low-noise gear pairs for transmissions.

[0006] From a process engineering point of view, this invention is achieved by the fact that the contact analysis is not based on the deviation as a whole but only on a specifically selected portion of the deviation in the complementary space.

[0007] Within the scope of the invention, it was recognized that the data supplied by gear testing machines, which represent the surface deviation from the ideal target tooth flank, are not well suited in this form to making statements about the expected noise emission development. According to the invention, it is therefore intended to work via the complementary space. One potential design option would be a frequency space, for example through Fourier transformation, and the consideration of the resulting spectral weights for the individual spatial frequencies, but also other transformations to decompose the measured data into spectral components. Furthermore, the invention is based on the recognition that waviness with wavelengths of the order of magnitude of the gear geometries such as height in the profile direction or gear width plays a significant role in noise development.This has been discussed in modern research for some time, but is controversial. The effects of waviness appear to be ambiguous: While it seems logical that waviness on the tooth flank can or should be the cause of unwanted vibration excitation and thus noise generation, the precise and quantitative extent to which such excitation is related to the amplitude and length of the waviness remains unclear. There are apparently also experiments that suggest that a deliberately adjusted waviness can also have a positive effect on noise generation.

[0008] Finally, the invention is based on the realization that pure simulations only at the calculation and simulation level of targeted tooth flank modifications, including waviness, have only a lower informative value because they have no concrete reference to actually manufactured gears, whereas holistic data with a concrete reference to manufactured gears are also not a good starting point for a targeted analysis due to the simultaneous interaction of numerous influencing factors in the form of gear errors introduced during production due to numerous causes, the effects of which overlap in the test data of the gear measurement.

[0009] By means of the inventive approach, however, the portion specifically used for further analysis is specifically tied to the gear manufacturing process, since it is derived from the test data for this gear, and yet the influence of the portion specifically selected in the complementary space can be determined more reliably, since other effects are at least partially masked out.

[0010] Further advantageous process designs are specified in the subclaims.

[0011] For example, a two-dimensional complementary space could also be considered for the surface measurement data of the gear teeth (3D topography data). However, the measurement could also directly provide measurement data along a (one-dimensional) path (2D inspection data). In a preferred design, a one-dimensional complementary space is used. In spatial space, a path across the tooth flank is provided for this purpose.

[0012] In one method variant, the direction of the path can be defined with reference to the geometric dimensions of the tooth flanks, for example, via an angle to the tooth trace direction or the profile direction, see also below. In a likewise preferred variant, the path direction is set in a direction along which waviness is to be expected. In this context, the direction is preferably selected depending on specifications obtained from fine machining, in particular hard fine machining of the teeth, such as feed markings and scoring, i.e. depending on the engagement conditions during fine machining. In principle, the measurement data taken from one flank, for example a left or right flank, are sufficient.However, for the spatial domain, the gear measurement data is preferably used not just for one tooth flank, but for several tooth flanks, in particular all tooth flanks (each with the same name), and correspondingly for the tooth flank with a different name. The path across the tooth flank should preferably have a directional component in the profile direction, in particular the predominant directional component, in particular be a path running in the profile direction. This means that the profile form deviation is of particular interest to the invention, since it has been found that this has a greater influence on noise emissions than flank form deviations. On the other hand, the influence of flank form deviations must certainly be taken into account, and in this respect, the invention also provides for the possibility of a mandatory directional component of the path in the tooth trace direction, which directional component can also be the predominant directional component.It is also being considered to use the path to represent the contact path on a gear of the meshing gear pair. Instead of representing the contact path in the profile direction, the pitch length (length along the line of contact), well-known from gear technology, could be used to represent the contact path in the profile direction.

[0013] The frequency domain is preferably used as the complementary space, preferably via the Fourier transform, such as the Fourier series expansion. This yields the corresponding spectral weight of the measured deviation data for each frequency in the frequency domain.

[0014] The specifically selected portion can then comprise a single frequency or a group of selected frequencies, such as higher harmonics, but also the ghost frequencies described later. Since the selection is based on actual, real measured data, the very sharp centering of individual frequency peaks that is typical of simulations does not usually result in the frequency domain. Nevertheless, the immediately adjacent frequencies can preferably be included, provided their spectral weight lies above a predetermined limit. The person skilled in the art will easily be able to select this threshold appropriately from a representation in the frequency domain; for example, the neighboring frequencies, possibly even the next-but-one neighboring frequencies, up to the third or fourth-nearest neighboring frequencies, can also be considered.In one variant, so-called mesh frequencies with a number of desired harmonics can be included. These frequencies can be derived from the motion frequencies of the meshed gear pair and are expected, as some of them are unavoidably present anyway. These frequencies are included with their real amplitude, i.e., their real spectral weight, as determined from the measured deviation. However, the mesh frequencies can also be partially or entirely excluded in order to specifically select other frequencies to test their effects.

[0015] In addition, so-called ghost frequencies can also be included, i.e. frequencies that have no relation to frequencies / wavelengths that can be derived from the movement frequencies of the gear pair in engagement and from the toothing geometries of the gear pair.

[0016] In a similarly preferred variant, one or more frequencies can be specifically selected based on feedback from a noise measurement on the actual transmission, for example from an end-of-line test facility of a transmission manufacturer. For example, a manufacturer may experimentally identify a particular interference frequency on the actual transmission and wish to determine its origin. In the simplest case, where this frequency is already prominently identified in the measurement data, the origin is relatively clear. However, the origin may be present (beat, convolution) in the form of another frequency or multiple frequencies. The method may therefore include a targeted search for frequencies and frequency combinations that (through superposition / convolution) result in the obtained feedback frequency, as well as a review of the measured spectrum for the presence of these individual frequencies in the combination(s).These can then be selected to test their effect independently of the frequencies not considered because they were not selected. This may result in frequencies being selected whose amplitudes appear less pronounced in the measured spectrum and which, as such, would not be readily recognized as harmful in the spectrum.

[0017] From an operating perspective, it is certainly intended that the operator determines the specifically selected portion in part or in full, for example by making a corresponding input. This could be done graphically via a touchscreen or multi-touchscreen, for example by setting intervals or windows. However, it is also planned to provide selection programs that determine the specifically selected portion in part or in full. Such a selection program could scan the Fourier spectrum for frequencies whose spectral weight lies above a threshold, determine these frequencies, and select them individually for further analysis, in pairs, or in multiple combinations. This means that a corresponding test grid can be specified, which is then automatically tested.At the end of such an automatic or semi-automatic contact analysis, the frequency components that show a measurable and possibly recurring influence on the noise emissions can be identified.

[0018] In a preferred embodiment, the transmission error is determined during the load-bearing contact analysis. However, other properties such as force excitation, Hertzian stress, loss, etc. can also be determined. The mating gear for simulating the contact analysis can be an ideal master gear or a similarly measured mating gear.

[0019] In a further variant, a simulated component could be superimposed on the component selected according to the invention, for example a further frequency with amplitude, wavelength and phase.

[0020] In addition, the vibration excitations are preferably determined by means of a so-called NVH (noise-vibration-harshness) performance, and a concrete representation of the expected noise emissions is preferably created, for example by means of a visual representation such as a Campbell diagram.

[0021] A standard gear testing machine with a non-contact or tactile sensor can be used to generate the measurement data.

[0022] It goes without saying that the specified target profile of the gear surface may already include tooth flank modifications such as crowning, set, etc.

[0023] The invention is also protected not only in terms of process technology, but also in the form of a software program which, when executed, carries out a contact analysis according to the invention, as well as by a corresponding analysis device and a measuring and analysis apparatus which includes a tooth testing device for determining the measurement data, which can be located at the same location as the analysis device, but does not have to be.

[0024] Further features, details and advantages of the invention will become apparent from the following description with reference to the accompanying figures, of which

[0025] Fig. 1 is an explanatory diagram of the profile deviation on a tooth flank,

[0026] Fig. 2 shows a fictitious wave-shaped deviation,

[0027] Fig. 3 shows a measured shape deviation and a superposition of three frequency components,

[0028] Fig. 4 shows representations of measurement signals taking into account all tooth flanks and their representation in the complementary space for left and right flanks,

[0029] Fig. 5. shows a purely schematic representation of expected noises matching the complementary space representation in Fig. 4 bottom right, and

[0030] Fig. 6 shows a schematic representation of a testing device for measuring the tooth flanks of a gear by laser scanning.

[0031] For a brief explanation of the so-called profile deviation, this is clearly shown in Fig. 1. The tooth flank 4 of a tooth 2 of a gear extends in the tooth width direction and in the profile direction (height direction) (Fig. 1, left). Deviations from the profile can be determined at the tip K and root F (Fig. 1, middle). And for a theoretically ideal tooth flank form TH, the profile measurement M shown as an example should be within a specified tolerance window T (Fig. 1, right). The difference between the curves M and TH thus represents the deviation between a measured tooth flank and a theoretically specified target flank.

[0032] If a fictitious virtual wave-shaped deviation is entered into a measurement diagram, as shown in Fig. 2, it can be seen that wave-shaped deviations can certainly lie within the tolerance range (outer limit lines in Fig. 2). Furthermore, the three dimensional arrows shown in Fig. 2 represent parameters that could define a wave shape and its position, such as the wavelength (vertical distance arrow approximately between 18 and 14 mm in Fig. 2), position of a high point relative to the tip (upper distance arrow in Fig. 2 approximately between 18 and 20 mm), and (double) amplitude of the wave (horizontal distance arrow in Fig. 2). In the diagram in Fig. 2, the vertical axis corresponds to the rolling length (length on the entry line), here for a left flank. In Fig. 3 (left), a form deviation measured in the profile direction compared to a target profile is shown. After Fourier transformation, one obtains the values ​​shown in Fig.The frequencies fi, f2, and f3 indicated in the center of Fig. 3 are coefficients with corresponding amplitudes, the back-transformation of which into the spatial domain results in the sinusoids shown in Fig. 3, center, with constant amplitude and only one frequency. For example, the contact analysis could then be based only on the component from these three frequencies. A representation of the corresponding superposition of these three frequencies, back-transformed and displayed in the spatial domain, results in the curve shown in Fig. 3 on the right; further irregularities and components that are still recognizable in the measurement signal in Fig. 3 on the left are no longer included.

[0033] If the profile deviations of all teeth are measured in one section, for example, and these are combined according to the pitch path, the deviation shown in bold in Fig. 4 for the left flank at the top left and for the right flank at the bottom left is obtained after removing the overlapping areas; the corresponding representations after Fourier analysis in the complementary space (frequency domain). The marked first to fourth harmonics can be seen on both flanks, although their amplitudes are different. Furthermore, it can be seen that the immediately adjacent coefficients for representing the harmonics can be included for the specific selection; in this selected embodiment, these are the two immediately adjacent frequency coefficients in the frequency domain.

[0034] Furthermore, it can be seen from the representation in the frequency domain in Fig. 4 on the right that there are coefficients with spectral weight above a certain threshold, which lie outside the harmonics and which are circled in Fig. 4. These frequencies are referred to as ghost frequencies in this application, since they have no relation to frequencies / wavelengths that can be derived from the motion frequencies of the gear pair in mesh and from the toothing geometries of the gear pair, in contrast to the so-called "mesh harmonics".

[0035] If, for example, the four marked harmonics are selected as the specifically selected component and optionally none, one or more of the ghost frequencies are selected, the influence of each individually recorded ghost frequency on the noise emissions can be individually obtained by only basing the simulated contact analysis on the corresponding specifically selected component, at an amplitude similar to that found in the actual gear and known from measurements. The illustration in Fig. 5 shows a comparison between the spectral weight as shown in Fig. 4, bottom right, and the result of a noise emission determination. The lower diagram in Fig. 5 is a Campbell diagram and is shown only very schematically for illustrative purposes, but with the elliptically bordered areas it illustrates the relationship to the three ghost frequencies considered, which can be seen in the Campbell diagram for the left tooth flank (Fig.4, above) is not shown.

[0036] Accordingly, analyses for noise emissions are possible based on real measurement data with a specific reference to the gearing, which are unaffected by disturbances of other kinds, since only the specifically selected part of the deviation described above and not the deviation as a whole is taken into account.

[0037] Fig. 6 also shows the basic principle of a gear testing machine in which the tooth flanks 12 of a gear 10, which are clamped on a workpiece spindle 20 so as to be rotatable about the gear axis W and are measured while rotating in the direction R by means of a laser sensor 6 whose field of view 8 lies in the area of ​​the gear. It is understood that other testing machines can also be used, for example a machine in which the laser sensor 6 can be arranged so as to be adjustable in up to three spatial directions, as described, for example, in WO 2019 / 083932 A1, which is incorporated by reference in this regard.

[0038] The load-dependent contact analysis itself can be performed using evaluation software familiar to those skilled in the art, for example, the KISSsoft software from the applicant. A software implementation could, for example, be realized via a software interface in which the above-described reduction of the two-dimensional measurement data to one dimension, subsequent transformation into Fourier space, and the specific selection of only a portion of the transformed deviation in Fourier space are performed. It is understood that, instead of such a software interface, existing, known evaluation software can also be extended for contact analysis, requiring the measurement data from the gear testing machine as input data.However, variants are also being considered in which some of the steps described above can still be carried out on the testing machine itself, which, for example, already creates and transmits the resulting frequency spectrum.

[0039] The invention is not limited to the embodiments, but the features of the following claims and the above description may be essential, individually or in combination, for the realization of the invention in its various embodiments.

Claims

Patent claims 1. Method for determining the expected noise emissions of a gear pair, in which the tooth flanks of one gear of the pair are measured and the deviation of the measured tooth flank surfaces from a predetermined target profile of this surface is determined from the measurement data obtained, and in which a simulation in the form of a contact analysis under load is carried out for the gear pair on the basis of this deviation, characterized in that the contact analysis is not based on the deviation as a whole, but only on a specifically selected portion of the deviation in the complementary space.

2. Method according to claim 1, wherein deviation data are determined from the surface deviation by including several, in particular all, flanks of the gear with the same name along a path over the tooth flank.

3. Method according to claim 2, wherein the path has a directional component in the profile direction, in particular a predominant directional component, and in particular runs in the profile direction or is the contact path of the gear pair.

4. Method according to claim 2 or 3, wherein the complementary space is one-dimensional, with an associated spatial space corresponding to the path.

5. Method according to one of the preceding claims, wherein the surface deviation is subjected to a Fourier analysis, in particular one-dimensional with respect to the path according to one of claims 2 to 4.

6. Method according to any of the preceding claims, wherein the specifically selected component comprises a spectral component of a selected frequency or a group of selected frequencies.

7. Method according to claim 6, wherein the spectral weight of its immediate surroundings is selected for a selected frequency.

8. Method according to one of the preceding claims, wherein at least one, in particular several, nearest harmonics are selected for a fundamental frequency / wavelength.

9. Method according to one of the preceding claims, wherein the selected frequency(ies) with their amplitude as obtained from the transformed measured deviation is / are included.

10. Method according to one of the preceding claims, wherein frequencies are selected or co-selected which have no relation to frequencies / wavelengths derivable from the movement frequencies of the gear pair in engagement and from the gear geometries of the gear pair.

11. Method according to one of the preceding claims, wherein the deviation is displayed to an operator and the operator determines the specifically selected proportion in part or in whole by an input.

12. Method according to claim 11, wherein the display is graphical, in particular via a touchscreen, in particular a multi-touchscreen, and the input is in particular by setting intervals or windows.

13. Method according to one of the preceding claims, wherein the specifically selected proportion is determined partly or entirely by a selection program.

14. Method according to one of the preceding claims, wherein the rotational path error is determined during contact analysis.

15. Method according to one of the preceding claims, wherein contact analysis is used to create a visual representation of the expected noise emissions, for example by means of a Campbell diagram or similar.

16. Method according to one of the preceding claims, wherein the measurement is carried out by means of a touch sensor and / or without contact, for example optically, for instance by laser scanning.

17. Software program for performing a contact analysis according to one of the preceding claims, if an analysis device is executed on a computing unit.

18. Analysis device configured to perform a contact analysis of a gear pair according to any one of claims 1 to 16.

19. Measuring and analysis device comprising a gear testing device for measuring tooth flank surfaces and an analysis device according to claim 18.

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