Method for determining expected noise emission of gear pair

Abstract

The invention relates to a method for determining an expected noise emission of a gear pair, in which method a tooth flank of a gear in the gear pair is measured and a deviation of the measured tooth flank surface from a predefined target contour of the surface is determined from the measured data thus obtained, and in which method the noise emission of the gear pair is determined on the basis of the deviation. The gear pair is simulated in the form of a contact analysis under the action of a load, the contact analysis being not based on the overall deviation, but only on a specific selected part of the deviation in the supplementary space.

Description

[0001] The invention relates to the field of transmission engineering and gear technology. It is known that the meshing of two torque-transmitting gears in a transmission, i.e. a gear pair, creates the risk of unwanted noise emissions, in particular in gear drives of electric vehicles. The strategy currently adopted by vehicle manufacturers is essentially to require very high-quality gears to be produced in accordance with ISO 1328, since it is known that the high precision grades of the gears used not only increase the service life but also improve the noise by reducing vibration excitation (so-called NVH, noise, vibration and harshness performance).

[0002] There are many factors that influence the formation of noise, and when designing gear pairs for transmissions, despite high quality requirements, unwanted noise can still occur. Therefore, it is very common that after designing and manufacturing gears that operate within the desired tolerances, the formation of undesirable noise is detected by simulation or actual testing of the transmission in use under load through contact analysis.

[0003] In this respect, the invention relates in particular to a method for determining the expected noise emission of a gear pair, in which method the tooth flanks of a gear in the gear pair are measured and the deviation of the measured tooth flank surface from a predefined target profile of the surface is determined based on the measurement data obtained therefrom, and in which method, based on the deviation, the gear pair is simulated in the form of a contact analysis under load.

[0004] In view of the above problems, the present invention is based on the object of contributing to providing a low-noise gear pair for a transmission device.

[0005] From a process engineering point of view, the solution of the invention is the following: The contact analysis is not based on the deviation as a whole, but only on a specific selected part of the deviation in the complementary space.

[0006] Within the scope of the invention, it has been recognized that the data provided by a gear testing machine characterizing the surface deviation from the ideal target tooth flank are not well suited in this form to provide conclusions about the expected noise emission formation. According to the invention, it is therefore provided to work with a complementary space. A potential design alternative would be the frequency domain, for example by Fourier transformation, taking into account the resulting spectral weights of the individual spatial frequencies, and other transformations that decompose the measured data into spectral components. In addition, the invention is based on the recognition that the waviness with a wavelength in the order of magnitude of the tooth geometry (such as the height in the profile direction or the tooth width) plays an important role in the noise formation. Modern research has been discussing this for some time, but it is still controversial. The influence of the waviness does not seem to be obvious: it seems logical that the waviness of the tooth flank could or should be the cause of the unwanted vibration excitation and therefore the cause of the noise formation, but it is not clear as to the exact and quantitative correlation of such excitation with the amplitude and length of the waviness, and there are obviously other experiments according to which a specifically adjusted waviness may also have a positive influence on the noise formation.

[0007] Finally, the invention is based on the recognition that pure simulations only at the level of calculating and simulating the target tooth surface modification (including fluctuations) have only limited information value, since they have no specific reference to the actually manufactured tooth part, and the overall data with a specific reference to the manufactured tooth part are not a good starting point for the target analysis, due to the simultaneous collaborative influence of many influencing factors in the form of tooth defects present in production, the influence of which overlaps in the test data of the tooth measurement.

[0008] However, by means of the method according to the invention, the portion specifically selected for further analysis is specifically related to the tooth manufacturing process because it originates from test data of the tooth and the influence of the specifically selected portion in the supplementary space can be determined more reliably because other influences are at least partially suppressed.

[0009] Further advantageous configurations of the method are specified in the dependent claims.

[0010] For example, for tooth measurement data obtained from surface measurements of the surface (3D topography data), a two-dimensional complementary space can also be considered. However, the measurement can also directly provide measurement data along a (one-dimensional) path (2D test data). In a preferred design, a one-dimensional complementary space is used. In the spatial domain, a path on the tooth flank is provided for this purpose.

[0011] In one variant of the method, the direction of the path can be determined with reference to the geometrical dimensions of the tooth flank, for example by a certain angle to the flank line direction or to the contour direction, see also below. In another preferred variant, the path direction is set to the direction along which the waviness is expected to occur. In this case, the direction is preferably selected according to the specifications such as feed marks and notches obtained by fine machining of the tooth, in particular by hard fine machining, i.e. as the meshing conditions during fine machining vary.

[0012] In principle, measurement data taken on one side surface, such as the left side surface or the right side surface, are sufficient. However, for the spatial domain, the tooth measurement data are preferably used not only for one tooth side surface, but also for several tooth side surfaces, in particular for all tooth side surfaces (each with the same name), respectively for tooth side surfaces with different names. The path on the tooth side surface should preferably have a directional component in the direction of the profile, in particular it should be a main directional component, in particular a path extending in the direction of the profile. That is, for the present invention, profile shape deviations are of particular interest, because it has been found that profile shape deviations have a greater influence on noise emissions than profile shape deviations. On the other hand, the influence of profile shape deviations must be taken into account, and in this regard, the present invention also proposes that there may be a mandatory directional component for the path in the direction of the side line, which directional component may also be the main directional component. It is also envisaged to use a contact path on a gear of a gear pair that meshes with the path. As a way of displaying the contact path, it is also possible to choose a method of displaying the rolling length (length on the meshing line) known from gear engineering, instead of displaying the contact path in the direction of the profile by following the profile on a direct route.

[0013] The frequency domain is preferably used as the complementary space, preferably by means of a Fourier transformation, for example by means of a Fourier series expansion. This produces corresponding spectral weights for the deviation data measured at a particular frequency in the frequency domain.

[0014] The specific selected part may then include a single frequency or a group of selected frequencies such as higher harmonics, but may also include ghost frequencies described later. Since the selection is based on actual real measured data, the individual frequency peaks in the frequency domain generally do not appear to be very sharply centralized as is customary in simulations. However, it is preferred to include adjacent frequencies, provided that their spectral weights are above a predetermined limit. A person skilled in the art will be able to easily select the threshold appropriately from the characterization in the frequency domain; for example, to achieve this purpose, adjacent frequencies are considered, and the next and only one adjacent frequency may also be considered, up to the third or fourth and only one adjacent frequency.

[0015] In a variant, the so-called meshing frequencies with a number of desired harmonics can be included, i.e. frequencies that can be derived from the movement frequency of the gear pair in meshing and are expected, since some of these frequencies are inevitably present anyway. These frequencies are included together with their real amplitudes (i.e. their real spectral weights determined from the measured deviations). However, the meshing frequencies can also be partially or completely excluded in order to specifically select other frequencies to test their influence.

[0016] Furthermore, so-called ghost frequencies may also be included, ie frequencies which are independent of the frequency / wavelength which can be derived from the movement frequency of the meshing gear pair and from the tooth geometry of the gear pair.

[0017] In another preferred variant, it is envisaged that one or more frequencies are specifically selected based on feedback from noise measurements of actual transmissions, for example from a transmission manufacturer's end-of-line test site. It may happen that the manufacturer has experimentally discovered the presence of a specific interfering frequency in an actual transmission and wants to determine its source. In the simplest case, where the frequency can already be clearly identified based on the measurement data, the source is relatively clear. However, the source may be in the form of another frequency or several frequencies (beat frequency, convolution). Therefore, the method may include a targeted search for frequencies and frequency combinations that produce the obtained feedback frequency (by superposition / convolution) and checking the measured spectrum for the presence of these individual frequencies in the combination / combinations. These frequencies can then be selected to test their influence, regardless of the frequencies that are not taken into account because they are not selected. This may result in the selection of frequencies whose amplitudes are not so obvious in the measured spectrum and are therefore not easily identified as harmful in the spectrum.

[0018] In terms of operation, it is certainly intended that the operator personally determine the specific selected part partially or completely, for example by means of corresponding inputs. This can be done graphically via a touch screen or multi-touch screen, for example by setting intervals or windows.

[0019] However, it is also envisaged to provide a selection procedure which determines in part or in full a specific selected portion. Such a selection procedure can scan the Fourier spectrum for frequencies which are above a threshold value in terms of spectral weight, determine these frequencies and select them individually or in pairs or also in a plurality of combinations for further analysis. This means that a corresponding test grid can be specified which is then automatically checked. Those frequency portions which exhibit a measurable and possibly recurring influence on the noise emission can then be identified at the end of such an automatic or semi-automatic contact analysis.

[0020] In a preferred embodiment, the transmission error is determined as part of a load-based contact analysis. However, other characteristics may also be determined, such as force excitation, Hertzian pressure, losses, etc. The mating gear used to simulate the contact analysis may be an ideal "master gear" or a mating gear that has also been measured.

[0021] In another variant, according to the invention, the simulated portion can be superimposed on the selected portion, for example another frequency with amplitude, wavelength and phase.

[0022] Furthermore, the vibration excitation is preferably determined with the aid of the so-called NVH (Noise, Vibration, Harshness) performance, and a concrete representation of the expected noise emission is preferably also formed, for example with the aid of a visual representation such as a Campbell diagram.

[0023] To generate the measurement data, conventional gear testing machines with non-contact sensors or tactile sensors can be used.

[0024] It goes without saying that the specified target contour of the tooth surface may already include tooth flank modifications such as crowns, setbacks or the like.

[0025] The invention is protected not only in terms of process engineering, 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 device comprising a tooth testing device for determining measurement data, which can be located, but not necessarily, at the same location as the analysis device.

[0026] Further features, details and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings, in which:

[0027] Figure 1 is an indicative representation of the profile deviation of the tooth flank,

[0028] Figure 2 shows a hypothetical corrugated deviation,

[0029] Figure 3 shows the measured shape deviation and the superposition of three frequency components,

[0030] Figure 4 shows the representation of the measurement signal taking all tooth flanks into account and its representation in the complementary space of the left and right flanks,

[0031] Figure 5 Shown with Figure 4 The complementary spatial representation at the bottom right matches the purely schematic representation of the expected noise, and

[0032] Figure 6A schematic representation of a test rig for measuring the tooth flanks of a gear wheel by laser scanning is shown.

[0033] To briefly explain what is called contour deviation, Figure 1 This is clearly shown. Thus, the tooth flanks 4 of the teeth 2 of the toothing extend in the toothing width direction and in the profile direction (height direction) ( Figure 1 , left), the deviation from the contour can be determined at the head K and the root F ( Figure 1 , middle), and for the theoretically ideal tooth flank shape TH, the profile measurement result M shown as an example should be within the specified tolerance window T ( Figure 1 , right). Therefore, the difference between curves M and TH characterizes the deviation between the measured tooth flank and the theoretically specified target flank.

[0034] If the hypothetical virtual corrugated deviation is input into Figure 2 As shown in the measurement result diagram, it can be seen that the corrugated deviation can definitely fall within the tolerance range ( Figure 2 In addition, Figure 2 In FIG. 1 , the three illustrated dimension arrows represent parameters that can define the waveform and its position, such as wavelength ( Figure 2 The vertical distance arrow between approximately 18 mm and 14 mm in the figure), the position of the high point relative to the head ( Figure 2 The upper distance arrow in the figure is approximately between 18 mm and 20 mm) and the (double) amplitude of the wave ( Figure 2 ). Figure 2 In the figure, the vertical axis corresponds to the rolling length (the length on the incoming line), here it is the vertical axis of the left side.

[0035] exist Figure 3 On the left, the shape deviation measured in the contour direction compared to the target contour is shown. After Fourier transformation, we obtain Figure 3 The coefficients of the frequencies f1, f2, and f3 given in the middle have corresponding amplitudes, which are inversely transformed into the spatial domain to produce Figure 3 The sinusoid with constant amplitude and only one frequency is shown in the middle. For example, the contact analysis can then be based only on the part consisting of these three frequencies. The corresponding superposition of these three frequencies, inversely transformed and displayed in the spatial domain, yields Figure 3 The curve shown on the right; still in Figure 3 Other irregularities and parts that are discernible in the measurement signal on the left are no longer included.

[0036] If the profile deviations of, for example, all teeth in a segment are measured and combined according to the rolling path, then after removing the overlapping areas, we obtain Figure 4Deviations in bold for the left side at the top left and for the right side at the bottom right in the figure; associated representations after Fourier analysis in the complementary space (frequency domain). The marked first to fourth harmonics of both sides can be seen, although their amplitudes are different. Furthermore, it can be seen that for a particular selection, adjacent coefficients for mapping harmonics can be included; in this selected exemplary embodiment, these are two adjacent frequency coefficients in the frequency domain.

[0037] In addition, you can Figure 4 The representation in the frequency domain on the right shows that there are coefficients with spectral weights above a certain threshold, which fall outside the harmonics and are Figure 4 These frequencies are referred to as ghost frequencies in the context of this application, since, in contrast to the so-called "meshing harmonics", they have nothing to do with the frequencies / wavelengths that can be derived from the movement frequency of the gear pair in meshing and from the tooth geometry of the gear pair.

[0038] If, for example, four marked harmonics are selected as specific selected portions, and optionally zero, one or more ghost frequencies are also selected, the impact of each individually recorded ghost frequency on the noise emission can be obtained individually by performing a simulated contact analysis based only on the corresponding specific selected portion, and with the amplitude as it exists in the actual gear and is known after the measurement has been performed.

[0039] exist Figure 5 The diagram shows that Figure 4 The lower right figure shows a comparison between the spectral weights and the determination of the noise emissions. Figure 5 The lower figure of the Campbell diagram is shown only very schematically for illustration purposes, but the area outlined by the ellipse shows the connection with the three considered ghost frequencies, which is not shown in the Campbell diagram of the left tooth flank ( Figure 4 , above).

[0040] Thus, the noise emission can be analyzed based on real measured data with particular reference to the tooth section, which is not affected by other types of disturbances, since it is based only on a certain selected part of the above-mentioned deviation and not on the deviation as a whole.

[0041] Figure 6The basic principle of a gear testing machine is shown, in which the tooth flank 12 of a toothing 10 is clamped on a workpiece spindle 20 so as to be rotatable about a toothing axis W and, while rotating in a direction R, is measured by means of a laser sensor 6 whose field of view 8 falls in the region of the toothing. It will be appreciated that other testing machines may also be used, for example machines in which the laser sensor 6 may be arranged so as to be adjustably positionable in up to three spatial directions, as described in WO 2019 / 083932 A1, which is incorporated by reference in this respect.

[0042] The load-based contact analysis itself can be performed using evaluation software known to the person skilled in the art, such as the KISSsoft software known to the applicant. The implementation of the software can be realized, for example, by a software interface, in which the above-mentioned reduction of the two-dimensional measurement data to one-dimensional measurement data, the subsequent transformation into Fourier space and only a specific selection of a part of the transformed deviations in Fourier space are performed. It goes without saying that, instead of such a software interface, the already existing known evaluation software can also be extended for contact analysis and still require measurement data of the gear testing machine as input data. However, some variants are also envisaged in which some of the above-mentioned steps can still be performed on the test machine itself, which, for example, has already generated and delivered the resulting frequency spectrum.

[0043] The invention is not limited to the exemplary embodiments, but rather the features of the following claims and the above detailed description, either alone or in combination, may be essential for the implementation of the invention in its various embodiments.

Claims

1. A method for determining the expected noise emission of a gear pair, in which method the tooth flanks of a gear in the gear pair are measured and the deviation of the measured tooth flank surface from a predefined target profile of the surface is determined based on the measurement data obtained therefrom, and in which method the gear pair is simulated in the form of a contact analysis under load based on the deviation, It is characterized in that The contact analysis is not based on the deviation as a whole, but only on certain selected parts of the deviation in the complementary space.

2. The method according to claim 1, wherein: The deviation data along the path on the tooth flank are determined from the surface deviation taking into account several flanks, in particular all flanks, of the gear wheel of the same name.

3. The method according to claim 2, wherein: The path has a directional component, in particular a main directional component, in the direction of the profile and in particular extends in the direction of the profile or is a contact path of the gear pair.

4. The method according to claim 2 or 3, wherein: The complementary space is a one-dimensional space, wherein an associated spatial domain corresponds to the path.

5. A method according to any one of the preceding claims, wherein: The surface deviation is subjected to a Fourier analysis, in particular a one-dimensional Fourier analysis of the path according to one of claims 2 to 4 .

6. A method according to any one of the preceding claims, wherein: The particular selected portion comprises a portion of the spectrum of a selected frequency or a group of selected frequencies.

7. The method according to claim 6, wherein: For a selected frequency, the spectral weight of its immediate surroundings is also selected.

8. A method according to any one of the preceding claims, wherein: For the fundamental frequency / wavelength at least one, and in particular several, closest harmonics are selected.

9. A method according to any one of the preceding claims, wherein: The selected frequency(s) are input and their amplitudes obtained from the transformed measured deviations.

10. A method according to any one of the preceding claims, wherein: A frequency is selected or also selected that is independent of a frequency / wavelength that can be derived from the movement frequency of the gear pair in meshing and from the tooth geometry of the gear pair.

11. A method according to any one of the preceding claims, wherein: The deviation is displayed to an operator, and the operator determines the specific selected portion partially or entirely according to the input.

12. The method according to claim 11, wherein: The display is a graphic display, in particular via a touch screen, in particular a multi-touch screen, and the input is effected in particular by setting intervals or windows.

13. A method according to any one of the preceding claims, wherein: The specific selected portion is determined in part or in whole by a selection procedure.

14. A method according to any one of the preceding claims, wherein: A rotational path error is determined during the contact analysis.

15. A method according to any one of the preceding claims, wherein: The contact analysis is used to form a visual representation of the expected noise emissions, for example by means of a Campbell diagram or the like.

16. A method according to any one of the preceding claims, wherein: The measurement is performed by means of a touch sensor and / or by means of a contactless sensor, for example by optical means, for example by laser scanning. 17 . A software program for carrying out a contact analysis according to claim 1 , when an analysis device is executed on a computing unit.

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

19. A measuring and analyzing device comprising a gear testing device for measuring a tooth flank surface and an analyzing device according to claim 18.

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