Patent Application
20140363629
The invention relates to a thermally coated component having a frictionally optimized raceway surface for a frictional counterpart.
It is known from the prior art to optimise the surface properties, such as friction, of components that interact with a frictional counterpart. Components of this type are, for example, the cylinder and piston pairing, the interaction of which is of the utmost relevance with respect to the overall performance of an internal combustion engine, in particular from an ecological and economic perspective. The oil consumption of an internal combustion engine is fundamentally determined by friction, which can be reduced by mechanical surface processing for the introduction of oil-retaining structures. Cutting methods such as honing, in particular laser honing and spiral slide honing, are considered as methods for this processing. Thus, microstructures are introduced as “bags”, in which the oil collects and forms a liquid film that allows the frictional counterpart to virtually float on top and thus reduces the friction to an ideal extent.
The surfaces of such surface-processed components, which interact with a frictional counterpart, often also have material-specific structures that arise, for example, during the production of a coating of the surface and that may be rather undesirable, and processing-specific structures that are beneficial for carrying out the surface processing in the desired manner. It can thus arise that an ostensibly surface-optimized component does not present the expected frictional properties.
Thermally coated components that conform to their genre are known from publications DE 102010049840 A1, DE 102009010790 A1 and DE 19628786 A1.
Based on this prior art, the object of the present invention is to create improved thermally coated components having a frictionally optimized surface of a raceway for a frictional counterpart, which have a reproducible and as pre-determinable an oil retention volume as possible, in order to achieve the desired running characteristics of the frictional counterparts.
This object is solved by a thermally coated component having the features of claim 1, which has a frictionally optimized surface of a raceway for a frictional counterpart.
Developments of the component are embodied in the dependent claims.
The object furthermore arises to create a method for the component coating surface simulation of a thermally coated component, which has a frictionally optimized surface of a raceway for a frictional counterpart.
Such a method is provided by the method having the features of claim 6.
The thermally coated component according to the invention has a frictionally optimized surface of a raceway for a frictional counterpart, which has an oil retention volume VOil of 10 to 800 μm3/mm2.
The oil retention volume VOil does not have to be constant over the length of the raceway and/or the periphery thereof. The oil retention volume VOil is a combination of the oil retention volume of the frictionally optimized processing structure VOil,Processing and the oil retention volume of pores VOil,Pores.
In a preferred embodiment, the frictionally optimized surface of the raceway has an oil retention volume VOil of 50 to 200 μm3/mm2.
The oil retention volume is advantageously a theoretical oil retention volume that can be predefined by a component coating surface simulation.
The surface processing of the frictionally optimized surface can advantageously be a mechanical, in particular cutting, process. Here, honing processing methods are considered, which are known in themselves to the person skilled in the art and which are carried out with a high level of precision; this also occurs on surfaces, as preferred according to the invention, which are thermal spray coatings, in particular coatings that are obtained by wire arc spraying or by the PTWA spraying method (Phase Transfer Wire Arc Spray Coating).
The component according to the invention can be, to name but a few components, a cylinder crankcase or a piston or a connecting rod or a bush such as a cylinder liner; these can essentially have any shape which may operate with low friction in a frictional counterpart or in which a frictional counterpart may operate with oil lubrication.
Advantageously, according to the invention, the theoretical oil retention volume VOil, which is to be between 10 and 800 μm3/mm2, particularly preferably 50 and 200 μm3/mm2, may be pre-defined by means of a component coating surface simulation.
Such a simulation serves for the functionally-relevant, simple, detailed and frictional counterpart-relevant analysis of surfaces.
In a first embodiment of the simulation method, the parameter determination of surface structures of a component coating surface therefore takes place, said surface being in operative connection with a frictional counterpart. Here, the parameter simulates a function between the component coating surface and the frictional counterpart. Therefore, the method enables, by using the parameters by means of simple modules using software technology, the functional behaviour of component coating surfaces to be simulated. There thus arises, from the method according to the invention, the possibility of creating functionally-relevant tolerances depending on the frictional counterpart of the surface that is to be analysed, and thus of optimising play between the contact partners.
The method comprises the following steps:
Firstly, the totality of the surface structures of at least one pre-determined section of the surface of the material is recorded by means of a profile depth determination method. It is represented as an overall profile, wherein the overall profile is recorded as a data set of profile depth values obtained along a line of intersection around a pre-determined measuring baseline, which is allocated to a respective position along the length of the measuring baseline. Then a mathematical morphological calculation programme is applied to the data set of the overall profile and thus the unrolling of a circle with a defined radius on the overall profile is simulated and an unrolling line on top of the overall profile is obtained, which simulates a contour flow of the contact partners on the tool surface. Now the calculation or integration of an overall surface that is delineated by the unrolling line and the overall profile takes place, as well as the definition of the overall surface as a first parameter.
In one development of the method, a second parameter is determined with the first parameter. This comprises the projection of the overall surface into the third dimension with respect to the material surface, and calculating an overall volume as the second parameter.
In a further development, the calculation of the overall surface comprises the determination of a difference between the unrolling line for each profile depth value and the determination of an individual surface between each profile depth value and a corresponding section of the unrolling line as a function of the position of the profile depth value along the line of intersection. Then the individual surfaces are added along the line of intersection.
Furthermore, the first parameter can be standardized in terms of the route and the second parameter can be standardized in terms of the surface. This advantageously serves for the establishment of a basis for comparisons etc. in the case of profile sections of various lengths.
Thus, the function-simulating first parameter can be a measurement for the amount of oil that is relevant for lubrication, and the second parameter projected therefrom can specify a theoretical oil retention volume of the component coating surface. The defined radius of the circle for determining the unrolling line, which for example corresponds to a theoretical flow contour of the piston ring, can be approximately 100 mm for this.
Further parameters can be determined, such as the oil volume of the cover, in particular the porosity, the median pore width and the median pore intersection from the pore profile.
In general, the component coating surface and the frictional counterpart form a static tightness system, in particular along a sealing bead of head gaskets on separating planes of the crankcase and cylinder head, wherein, here, the function-simulating first parameter specifies a theoretical sealing gap. The defined radius of the circle for determining the unrolling line, which corresponds to a theoretical contour flow of the sealing bead, can then be selected for the adjustment of various sealing designs and stresses; it can lie approximately in the range of 1 mm to 100 mm.
Furthermore, further parameters can be determined, in particular a maximum individual joint surface.
By applying the method, tolerances for the function-simulating parameters can be specified in technical product documentation and handling instructions for transgressions can be provided. An optical profile measuring method or a profile method, in particular a profile method according to ISO 3274, is particularly considered as a method for determining the profile depth.
Furthermore, the simulation method can comprise the determination of the parameters for processing and material-specific surface structures that are to be differentiated between. Here, the overall profile of the component coating surface is separated into a material-specific pore profile and a processing profile. The investigation and surface analysis methods known from the prior art evaluate, as a whole, the surfaces of components such as thermal spray coatings of the components according to the invention, for example a running surface of a cylinder piston, and thus no classification of features is possible for the instigator, for example an operator or coater, as to how they have the component surfaces according to the invention. These have passed through several production and/or processing steps in order to acquire their final surface condition. Therefore, with a differentiation method according to the invention for the differentiation of technical surface structures as regards their origin, the proportions of surface structures are to be determined.
The differentiation of the surface structures of the component processed with a surface processing method, having material-inherent surface roughness, for example a honed coating of a piston bearing surface of a cylinder, takes place as follows:
In order to be able to establish the reason of origin or the cause of the structures with regard to their type, a priori knowledge is taken as a basis in order that the structural proportions be able to be separated from one another. Then the structural proportions that have been separated from one another can be supplied for various evaluations.
To that end, after carrying out a profile depth determination method, the totality of the surface structures of a section of the coating surface of the component with material-inherent surface roughness is recorded and represented as an overall profile. The overall profile is compiled as a data set of profile depth values obtained along a line of intersection around a pre-determined measuring baseline.
Then, with the same profile depth determination method, the totality of the surface structures of a section of the surface of a surface-processed technical component that has no material-inherent surface roughness is recorded and represented as a processing profile. This is recorded as a data set of profile depth values obtained along a line of intersection around a pre-determined measuring baseline, which is allocated to a respective position along the length of the measuring baseline.
There then follows the determination of asymmetry of the frequency distribution of all processing profile depth values, which is characteristic for the surface processing method, and the definition of this asymmetry as a characteristic target asymmetry for the surface processing method.
Furthermore, a start line in the overall profile is determined, which runs parallel to the measuring baseline of the overall profile according to the deepest profile depth value, and a first asymmetry of the frequency distribution of the profile depth values of the overall profile, which are tangent to the start line, is determined on the start line. Then, intermediate lines between the start line and the measuring baseline, which are separated from one another, are defined in stages and, based on the start line, the asymmetries of the frequency distributions of the profile depths values of the overall profile, which are tangent to the corresponding intermediate lines, are determined successively.
Based on the start line, the determined asymmetries are compared with the target asymmetry. If the asymmetry of a specific intermediate line of the overall profile concurs with the target asymmetry, all profile depth values are selected that are tangent to this specific intermediate line. Then these profile depth values are represented as a pore profile. Through the selection, it occurs that the “processing profile” arising from the processing method is left over and is, in this respect, separated from the overall profile.
Thus, the structural separation is virtually enabled by the application of a priori knowledge, which is arrived at when a component that has no material-inherent surface roughness undergoes the same processing method as a component that does have surface roughness. It is, for example, investigated as to what characteristics a honed structured has in a component without pores and the separation of the honed structured in a component with pores is derived from this. The method thus enables the separate and targeted analysis of surface structures with attribution to the instigator.
The function-simulating first parameter as a measure for the oil quantity that is relevant for lubrication, and the second parameter projected therefrom, which specifies a theoretical oil retention volume of the material surface, can thus also be determined for respective overall, pore and processing profiles.
Furthermore, in a further embodiment of the method, the continuous representation of the pore profile of the selected profile depth values takes place. The pore profile is depicted particularly clearly when it is shown in a scale that differs from the scale of the measurement section of the overall profile, in particular an enlarged scale. The pores, and thus material unevenness or roughness, are then shown as being linked together, as well as the processing profile.
After the structural separation, both internationally standardized parameters (such as Rz, Ra in μm, ISO 4287) and the function-simulating parameters can be evaluated from the processing profile section and/or the pore profile section and can be used in the present simulation method. Here, the algorithms of the parameters are applied to the digitally present, structurally separated data sets of the processing profile section and/or the pore profile section.
In order to achieve a high level of definition with respect to the separation of the material and processing profiles, the spacing of the intermediate lines from one another and to the start line and the measuring baseline are in the range of 1 nm to 20 nm, preferably in the range of 5 nm to 15 nm and particularly preferably 10 nm.
The figures schematically illustrate the simulation and differentiation methods used for surfaces.
Here are shown:
The simulation method serves for determining parameters for structures of component coating surfaces, which interact with a frictional counterpart, as illustrated in two examples: On the one hand, the determination of theoretical oil retention volumes and other function-simulating parameters for the cylinder raceway/piston ring components is carried out with the aid of
For this, VOil,Total in [μm2/mm3] denotes the theoretical oil retention volume that has been determined for the overall profile, as can be seen in
Further parameters, which can in particular also be determined according to the structural separation, are a pore proportion [%], a median pore width [μm] and a median pore intersection [μm2]. A parameter VOil,Cover [μm2/mm3] describes a theoretical oil retention volume of a cover such as a cylinder cover, cylinder head cover or valve cover.
The basis for the parameter calculation of the processing-specific theoretical oil retention volume VOil,Processing is the separation of the material- and processing-specific surface structures. VOil,Processing is calculated from the processing profile (see
VOil,Processing and VOil,Pores are determined just as VOil,Total, though VOil,Pores on the pore profile and VOil,Processing on the processing profile are determined as is shown in
In the case of mechanical profile methods, a probe tip is moved over the processed component coating surface at a constant speed. The measuring profile arises from the vertical positional displacement of the probe tip relative to the measuring baseline running parallel to the tool surface, said probe tip generally being detected by an inductive displacement measuring system. Here, the data set is obtained from the profile depth values along the measuring line.
The surface differentiation method that is illustrated in pictorial form in
As a basis for the separation of material and processing-caused surface structures, profile sections or measuring profiles are firstly made from processed component surfaces that have no pores and thus only display processed structures. Therefore, such a profile section may be used as a priori knowledge. The data set obtained, with the profile depth values, shall be the basis for the calculation of an asymmetry of the frequency distribution of the profile depth values. The asymmetry specifies the strength of the gradient of the statistical distribution of the profile depth values. The asymmetry determined with the pore-free component is typical of the respective processing method and describes the surface characteristics, such as symmetrical structures or structures that are plateau-like with different intensities, independent of the height characteristics of the structure, so independent of whether the processing was carried out coarsely or delicately. This asymmetry, which is typical of the processing method, is designed as a target asymmetry of the crucial parameters for the structural separation.
An optical or profile method carried out on a processed surface of a pore-afflicted material after obtaining a priori knowledge results in the overall profile section shown in
In stages, starting from the start line SL, intermediate lines ZL are defined in the direction of the measuring baseline GL in pre-determined, preferably adjustable steps of, for example 10 nm, wherein, for each intermediate line ZL (potentially also for the start line SL), the asymmetry of the frequency distribution of the profile depth values is determined, which is tangent to the respective intermediate line (or start line SL). What are meant by “tangential profile depth values” are, in the present case, also the profile depth values that cut intermediate lines.
The asymmetry calculated with respect to each intermediate line ZL is compared to the target asymmetry. For the intermediate line ZL*, whose asymmetry corresponds to the target asymmetry, all structural valleys, so all profile depth values that are cut by the intermediate line ZL*, are selected by the measuring baseline GL, digitally based on the overall profile section, and are depicted coherently in a pore profile section (cf.
The overall profile is combined at the points at which the pore profiles have been removed, such that the processing profile section arises from the overall profile section, as is depicted in
The separation method can be carried out automatically by a computer with corresponding algorithms, which enable the determination of the asymmetries, comparison of the asymmetries with the target asymmetry (which may be filed in a database) and the “sorting” of the profiles sections that the line ZL* cuts with a level of asymmetry that corresponds to the target asymmetry, as well as enabling its combination into the pore profile section and the creation of the processing profile section.
Both the pore profile section and the processing profile section may be the basis for the further evaluation of the surface. Here, the obtained pore profile section and the processing profile section are present as data sets which, as is shown in
Indeed, the surface structure separation does not in itself lead to the evaluation of the surface structures, but rather creates the conditions for a meaningful evaluation. The structural separation can, as described above, proceed automatically and can in particular also be adjusted for various processing methods (by determining the corresponding a priori knowledge). Thus the basis for the evaluation is achieved with parameters and standards. In a different manner from the hitherto known data pre-processing methods, such as filtering, even in the case of surfaces with extreme contrasts such as a highly refined processing in the presence of wide and deep pores, the method according to the invention does not lead to defects, as have so far occurred by covering the processing structure in the case of highly defined pores, whereby the evaluation of the processing structure with parameters was virtually impossible.
Further functional-simulating parameters are the relevant sizes for static sealing systems, for example the theoretical sealing gap that refers to the sealing properties along a sealing bead of head gaskets on the separating planes of the crankcase and cylinder head. The sealing gap is determined on the unfiltered surface overall profile by the unrolling line of a circle described above also being calculated here. Here, the radius is adapted to the properties of the seal. Thus, for example, a smaller radius of approximately 1 mm is selected in the case of several full beads and a thick coating of the metallic layer flat sealing, and a correspondingly larger radius is selected in the case of thinner coating. The gap between the calculated unrolling line and the surface overall profile is a measure for the seal that is to be expected. The sealing gap, denoted as parameter Df, is calculated by adding up all individual gap areas as a total area in μm2. In order to also achieve comparable results in the case of profile sections of different length, this calculated area is standardized to 1 mm.
A further parameter from this family is Dfmax in μm2. This is the largest individual gap area.
There is currently no interposition of human reasoning required for the parameter determination of the function-simulating parameters; the entire determination method proceeds automatically once the measured values and profiles have been input. One feature is the parametrisability (adaptability) to various sealing designs and stresses in the case of the parameters of the theoretical sealing gap.
For all function-simulating parameters, tolerances may be specified in technical product documentation. The action to be taken in case of transgression is, for example, dependent on the supplied documentation such as handling instructions.
In
The measuring profile in
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2012 002 766.4 | Feb 2012 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2012/005344 | 12/21/2012 | WO | 00 | 7/21/2014 |
