DE102009004198A1 - Characteristic value determining method for component surface i.e. tribologically loaded component surface, involves determining characteristic value based on average distance between points comprising smaller and greater heights - Google Patents

Abstract

The method involves measuring a surface topography in a dot screen, and generating a topography table that assigns a height value (z) to points (x-0-x-3) of a component surface i.e. tribologically loaded component surface. The point (x-0) with a height (z-0) greater than a preset minimum height (z-min) is determined. The nearest point (x-1) with a height (z-1) smaller than the preset minimum height is determined. The distance between the points is determined. A characteristic value is determined based on an average distance between the determined points.

Description

The The invention relates to a method for determining a characteristic value for the nature of a component surface, in particular a tribologically loaded component surface.

Tribologically stressed surfaces, especially those which are in operation under the action of a lubricant fluid, are often preprocessed to give them specific groove structures. This happens for example by honing or the like. The groove structures have z. B. the task to ensure optimal distribution of the lubricant fluid. In many surfaces, in particular the drainage effect of the grooves is important, so the ability to carry away lubricant from the bearing surfaces of the surface. So far, such surfaces are described by characteristics such as Traganteile, R _Z , R _A and the like. Although such characteristics provide information about height distributions of the surface, but are poorly suited to quantify the drainage effect of the aforementioned groove structure.

From the DE 10 2007 008 604 A1 For example, a method for evaluating structures of surfaces is known in which three-dimensional images of the surfaces, for example by white-light interferometry, are created and subdivided into target and false structures using image processing methods. This allows, in particular, an evaluation of the wear of surfaces, but is computationally expensive and also not optimally suited to quantify groove distributions and thus the drainage effect of surface structures.

Of the The present invention is therefore based on the object, a method of the aforementioned type so that height profiles of Surfaces can be summarized in one measure, which information about the expected drainage effect the surface gives.

These The object is achieved by a method having the features of the patent claim 1 solved.

One Such method for determining a characteristic value for the Texture of a component surface, in particular one tribologically loaded component surface, comprises a first process step, in which a surface topography the component surface to be characterized in a dot matrix is measured. Starting from this measurement becomes a topography table created, which every point (x, y) on the surface assigns a height value (z). For every point (x, y) with a height (z) greater than a given minimum height will now be the closest Point (x, y) with a height (z) smaller than the given one Minimum height determined and the distance between the two points certainly. The final parameter finally becomes determined in the last procedural step that over all previously determined distances between pairs of points averaged becomes.

Of the so certain characteristic value gives thus a middle measure for the extent of plateaus on the surface. With others In words, the characteristic value corresponds to the middle path, the oil drop have to cover the surface, to get from a plateau area into a groove and thus to be dissipated. This sets the characteristic value determined in this way a direct measure of the drainage effect of the surface dar. Time-consuming experiments with experimental surfaces can be omitted, because the surface structure through a simple measurement method can be evaluated. This will be the Development of new tribologically contaminated surfaces for Friction linings, transmission parts and the like considerably simplified and accelerated, which also saves development costs.

To the Measurement is sufficient here relatively small measuring surfaces in the order of a few square millimeters. The dot matrix for measuring the surface topology becomes depending on the desired condition of the surface and can, for example, point distances in the range of 10 to 100 microns. The predetermined minimum height, according to which a distinction is made between plateaus and grooves as a function of a predetermined carrying component of the surface to get voted. The method considers every point which is higher than the selected value of the minimum height as leveled to this minimum height. This assumes that at actual operating load of the surface these points are actually leveled by abrasion or elastic deformation become. Every point below the given minimum height Accordingly, it is considered to be a valley suitable for lubricating fluid dissipate.

In a preferred embodiment, not only the scalar distance between pairs of points is determined in method step c), but rather a complete distance vector with direction information is determined. This makes it possible to determine a characteristic number, which may contain, for example, information about drainage effects in preferred directions, as they occur during the operating load on the surface. For this purpose, in a further preferred embodiment, to determine the characteristic value, a weighted averaging of the specific point distances is carried out as a function of the direction of the determined distance vector. Thus, the sliding direction of the tribologically loaded Area to be considered. For the drainage effect, in particular, a drainage of the lubricant fluid transversely to the sliding direction of the surface is favorable.

In Another preferred embodiment will be in Determining the distances between respective pairs of points the distances determined only in the x and / or y direction. This allows a computationally simple determination the characteristic value, whereby distances from the beginning only in given Preferred directions are taken into account.

In In another preferred embodiment, the in last step certain characteristic value in addition squared and related to the specified minimum height Traganteil the surface to be weighted.

to Measurement of surface topography in the first process step Different methods are available, alternatively or can be put together. The measurement can for example, by mechanical scanning with a needle whose Position determined, for example via a piezoelectric element can be performed. Furthermore, non-contact Measuring methods, such as the use of a laser scanner or a white light inferometer possible. The procedure characterized in particular by the fact that the assessment of the Surface quality done non-destructively can, so that with a once measured component even more Experiments can be performed.

in the Following is the invention and its embodiments will be explained in more detail with reference to the drawing.

The only figure shows a schematic sectional view through a surface and those for the process meaningful parameters.

The figure shows a section through a component surface along a fixed y-coordinate. To determine the characteristic value, the respective height z of the surface is now measured in a defined dot matrix, here the points x ₀ , x ₁ , x ₂ , x ₃ . Each point (x ₀ , ..., x ₃ , y) is thus assigned its own height value (z ₀ , ..., z ₃ ). To determine the surface characteristic value, a minimum height z _{min is} determined and it is checked for each point whether the assigned height z is greater or smaller z _min . For points with z greater than z _min , it is assumed that the surface at this point is leveled to the height z _min . Points with a height value z less than z _min are considered as valleys.

In the example shown in the figure, the heights z ₀ and z _{2 of} the points x ₀ and x _{2 are} greater z _min . x ₀ and x ₂ represent plateaus. The heights of points x ₁ and x ₃ are smaller than z _min , so these points represent valleys.

In order to achieve a quantifiable measure of the drainage capacity of the surface, ie the average distance between plateaus and valleys and thus the average distance that a lubricant fluid drop has to cover in order to go from a plateau to a valley, x will now be included for each point an altitude value z greater z _min the nearest point with a height value z less z _min determined. Thus it is known for each plateau how far a fluid drop must flow in order to get from the respective plateau to the nearest valley. The total drainage capability of the surface is quantified by averaging over all point spacings so determined.

The The nearest valley to each plateau can be irrespective of direction the entire dot matrix can be determined. Alternatively it is possible Specify preferred directions, for example, in the sliding direction correspond to the surface during use. With that you can weighted values for the drainage effect of a surface in predetermined preferred directions are determined. This is special significant if the surface in their later Operating state tribologically loaded only in a preferred sliding direction becomes. The draining effect is particularly good there when the drainage routes perpendicular to the sliding direction are particularly short.

The described method thus allows a simple and non-destructive Quantification of the drainage effect of machined surfaces. In order to may be surface geometries relative to a improved drainage effect can be optimized without consuming Lifetime tests are necessary. Another advantage of the process lies in the fact that it is carried out without contact and nondestructive can be. The characteristic values determined by the method can thus by further experimental investigations on the same surface be supplemented, so that an even more complete Image of surface quality results.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• - DE 102007008604 A1 [0003]

Claims (6)

Method for determining a characteristic value for the Texture of a component surface, in particular one tribologically loaded component surface, with the steps: a) Measuring a surface topography in a dot matrix; b) Generating a topographical table showing each point (x, y) of the Assign a height value (z) to the surface; c) for each point (x, y) with a height (z) greater as a given minimum height: determining the closest Point (x, y) with a height (z) smaller than the given one Minimum height and determining the distance between the two points; d) Determine the characteristic value by averaging over all in step c) certain point distances. Method according to claim 1, characterized in that that in step c) determines a distance vector of the two points becomes. Method according to claim 2, characterized, that in step d) a weighted average of the in step c) specific point distances depending on the direction of the distance vector determined in step c) becomes. Method according to claim 1, characterized, that in step c) the nearest point (x, y) is determined only in the x and / or y direction. Method according to one of the preceding claims, thereby marked that the characteristic value determined in step d) is squared and with the relative to the predetermined minimum amount of support the surface is weighted. Method according to one of the preceding claims, thereby marked that in step a) the surface topography by mechanical scanning and / or by a laser scanner and / or determined by white light interferometry and / or the like becomes.