Road surface covering elements for a chassis dynamometer

Abstract

The invention relates to a method for manufacturing road surface covering elements that can be mounted on rollers of chassis dynamometers, including detection of a surface contour of a road surface covering within an essentially strip-shaped section. The method also includes production of a digital image of the detected section and manufacturing of the road surface covering element according to the digital image by means of a three-dimensional manufacturing technique.

Claims

1. A method for manufacturing road surface covering elements that can be mounted on rollers of chassis dynamometers, including: generating manufacturing data for producing a digital image of a strip-shaped section with vertical values in accordance with the surface contour of a road surface, and manufacturing the road surface covering element according to the digital image by means of a three-dimensional manufacturing technique, wherein: the digital image of the strip-shaped section has a predetermined length in the longitudinal direction and a predetermined width in the transverse direction, and is delimited in the longitudinal direction by a respective longitudinal edge, a digital representation of the surface contour is produced by associating a multitude of points with coordinates in the longitudinal direction of the strip-shaped section and coordinates in the transverse direction of the strip-shaped section within the digital image with a vertical value and the vertical values of the digital representation of the surface contour along the two longitudinal edges of the digital image are adapted to each other in such a way that the vertical values of the digital image of the two longitudinal edges at the same position in the transverse direction differ from each other by less than a predetermined deviation value after the adaptation.

2. The method according to claim 1, wherein the adaptation of the vertical values is carried out within at least one end region of the digital image, which is delimited on one side by one of the two longitudinal edges, and the at least one end region has a predetermined length in the longitudinal direction starting from the longitudinal edge that laterally delimits the end region.

3. The method according to claim 2, wherein the predetermined length of the at least one end region in which the vertical values are adapted is determined as a function of the number of maxima and/or minima of the vertical values in relation to the area or partial area of the digital image of the strip-shaped section and/or the predetermined length is determined as a function of average slope values of the vertical values that are situated in the vicinity of the maxima and/or minima.

4. The method according to claim 1, wherein the two longitudinal edges are digitally assembled so that an annular image of the strip-shaped section is produced, with a transition between the two longitudinal edges.

5. The method according to claim 4, wherein the digital image is assembled in such a way that the transition at the two longitudinal edges is positioned at 0 or 360 and the surface contour is situated on the outer circumference surface of the annular image.

6. The method according to claim 4, wherein the manufacturing of the road surface covering element is carried out by means of a three-dimensional printing technique and/or by means of a three-dimensional milling process and an entirety of the annular image is printed and/or milled in one piece.

7. The method according to claim 4, wherein the manufacturing of the road surface covering element is carried out by means of a three-dimensional printing technique and/or by means of a three-dimensional milling process and an arc element with a predetermined arc length of the annular image is printed and/or milled as an arc-shaped road surface covering element.

8. The method according to claim 4, wherein an entirety of the annular image is printed and/or milled in one piece and the annular road surface covering element is then divided into arc segments.

9. The method according to claim 1, wherein a length scale extending in the longitudinal direction of the digital image is standardized by degree position in such a way that the one longitudinal edge is positioned at 0 and the other longitudinal edge is positioned at 360.

10. The method according to claim 1, wherein the manufacturing data is generated by detecting a surface contour of a strip-shaped section of a road surface covering using an optical detection means, and the surface contour of the strip-shaped section is detected and digitized in such a way that a respective vertical value is determined for each of a predetermined number of points on the strip-shaped section.

11. The method according to claim 1, wherein the manufactured road surface covering element is composed of plastic or an inorganic material.

12. The method according to claim 11, wherein the inorganic material is ceramic or metal.

13. The method according to claim 1, wherein the road surface covering element is produced directly on the roller.

Description

(1) The invention will be described below by way of example with reference to the accompanying schematic drawings. In the drawings:

(2) FIG. 1 is a flowchart of an example of the method according to the invention,

(3) FIG. 2 is a schematic top view of an image and its cross-section,

(4) FIG. 3 is a schematic cross-section of a road surface covering element and an enlarged depiction of a transition, and

(5) FIG. 4 is a schematic cross-section of a road surface covering element that has been divided into a plurality of elements/segments.

(6) FIG. 1 shows a sequence of a manufacturing process according to the invention for road surface covering elements, including the steps: detection of a section 1 of a road surface covering, production of an image 3 of the detected section 1, and production of a (three-dimensional) road surface covering element 5. It can optionally also include adaptation of the longitudinal edges 2a, 2b.

(7) The detection of an essentially strip-shaped section 1 of a road surface covering is carried out by means of an optical detection means 6, for example a laser system or a stereo camera, which travels along a predetermined length L of a section 1 of a road surface covering to be detected and thus a surface contour is detected. For example, the detection takes place by means of scanning, photographing, etc. The predetermined length L of the detected section 1 essentially coincides with the circumference of the rollers U.sub.R of a chassis dynamometer. The detected width B of the detected section 1 of the road surface covering depends on the maximum scannable width, which is predetermined by the optical detection means 6. The predetermined width B of the detected section 1 should essentially coincide with the width B.sub.R of the rollers of a chassis dynamometer. If the maximum detectable width of the optical detection means 6 is less than the predetermined width B of the section 1 to be detected, then the road surface covering to be detected can be detected in a plurality of strip-shaped sections 1, for example one after the other, and then assembled, for example digitally.

(8) The step of the production of a (digital) image 3 of the detected section 1 takes place either integrated with or at the same time as the detection of the section 1, for example by means of a suitable device in the optical detection means 6, or separately. If the step occurs separately, then for example the data of the detected section 1 can be transmitted or sent by the optical detection means 6 to a data processing system (not shown) in which, based on the detected data of the optical detection means 6, the image 3 of the detected section 1 is produced. The image 3 of the detected section 1 is essentially a surface contour or more precisely a vertical value distribution over the area of the detected section 1; in other words, vertical values (z values) of individual points (positions) within the area of the detected section 1 are associated with a particular x/y coordinate (longitudinal/transverse position). In the simplest case, the image 3 of the detected section 1 can be a table or matrix that stores the detected vertical values (z values) for the detected positions/points within the area of the detected section 1. Preferably, the image 3 is a graphic representation of the detected surface contour of the detected section 1, for example an image file or a 3D design file.

(9) FIG. 2 shows a very schematic image 3 of the detected section 1. The upper depiction in FIG. 2 shows a top view of the image 3 with a vertical value distribution that is schematically depicted by means of lighter and darker areas or points. The upper depiction in FIG. 2 also shows the x direction, which is oriented in the longitudinal direction of the strip-shaped copy 3, and the y direction, which is oriented in the transverse direction of the image 3. The upper depiction in FIG. 2 also shows that longitudinal edges 2a, 2b delimit the image 3 in the longitudinal direction. The longitudinal edges 2a, 2b are each adjoined by respective end regions 2c, 2d of the image 3 with a predetermined length in the longitudinal direction (direction). The total length of the image 3 essentially corresponds to the total length of the detected section 1, i.e. the image essentially has the length L. The lower depiction in FIG. 2 is a cross-section (longitudinal profile) of the image 3 at a position that is not further specified in the transverse direction of the image 3. The lower depiction in FIG. 2 also shows an optional standardization by degree position in the longitudinal direction. The value 0 is placed at a (front) longitudinal edge 2a and the value 360 is placed at a (rear) longitudinal edge 2b.

(10) The step of the adaptation of the longitudinal edges 2a, 2b of the image 3 is particularly preferable because the flat, non-curved detected section 1 is transformed into a curved structure. In specific terms, the image 3 is adapted to the radius of the roller. According to the invention, this is achieved in that the two longitudinal edges 2a, 2b are brought together by a curving or bending of the digital image 3. In the simplest case, this is possible, for example, by means of an image processing and/or design program if the image 3 is in graphic form. The bending or curving of the image 3 to the radius of the roller(s) produces a digital annular image 3a. In it, the surface contour of the detected road surface covering is situated on the outer circumference surface of the annular image 3a. Preferably, the two longitudinal edges 2a, 2b are brought together in such a way that the position of a transition 4 between the two longitudinal edges 2a, 2b is situated at 0 or 360.

(11) The transformation of the strip-shaped section into the curved structure can preferably be carried out in such a way that at first, a volume model is generated from the strip-shaped section. This process is preferably carried out by means of a computer.

(12) In addition, a neutral plane in the z direction can be established, i.e. a zero plane in the z direction is defined. In a particularly preferred embodiment, the zero plane can be selected so that it is oriented along a line of the average roughness of surface contour in the z direction. It is also possible, however, for the zero plane to be oriented along a line of the maximum/minimum height of the profile in the z direction or in between.

(13) If the zero plane has been established, it can define the maximum contour height in the z direction, i.e. the zero plane can constitute the (subsequent) contact surface for the vehicle tires. If the zero plane has been determined, for example, by means of the average contour height/roughness of the surface contour in the z direction, then the contour regions that protrude beyond the zero plane in the z direction can be cut away so that across the entire strip-shaped section, there is a distribution of heights in the z direction that are adapted to one another (made uniform). It should be clarified, however, that the expression made uniform as applied to the surface contour does not mean that the contour itself is removed; the expression made uniform merely refers to the maxima in the z direction of the surface contour.

(14) The adaptation of the longitudinal edges/end regions to each other preferably occurs after the establishment of the zero plane.

(15) Furthermore, a bottom edge (in the z direction) can be produced for the generated volume model(s) of the strip-shaped section. To accomplish this, a fixed, constant z value can be determined, for example, along which the bottom edge of the volume model(s) extends.

(16) After the above-mentioned steps of the manufacture of a curved structure/a curved volume model (or a plurality of curved volume models), the volume model can be converted from a non-curved structure into a curved one by means of a computer.

(17) If a plurality of road surface covering elements are to be positioned on a roller, then the method explained above can also be modified such that the strip-shaped section is transformed into a volume model and individual segments, e.g. 6-8 pieces for a roller circumference, are cut out, i.e. the section is divided into e.g. 6-8 segments. The other steps of insertion of a zero plane, the adaptation of the longitudinal edges, the adaptation of the bottom edge, and the curving can, as explained above, also be carried out for the plurality of segments/volume models.

(18) FIG. 3 is a very schematic depiction of the annular image 3. The enlarged detail in FIG. 3 also shows an enlargement of the transition 4 between the two longitudinal edges 2a, 2b. The two longitudinal edges 2a, 2b at the transition 4 are shown spaced apart from each other (in the enlargement in FIG. 3) only for the sake of better visibility. As is also shown in the enlarged depiction in FIG. 3, the transverse profiles (vertical profiles in the transverse direction) of the two longitudinal edges 2a, 2b essentially fit on top of each other; in other words, they (specifically: the vertical values) essentially coincide with one another. The conformity that is shown in FIG. 3 has been produced, for example, by means of a design or graphics program and/or by means of adapting the numerical vertical values. The conformity of the transverse profiles of the two end regions 2a, 2b makes it possible for the transition 4 to produce as little as possible interference noise when a vehicle tire of a motor vehicle being tested rolls over the transition 4. In a particularly preferred embodiment, the end sections 2c, 2d that adjoin the longitudinal edges 2a, 2b (see FIG. 2) are adapted to each other so that the transition 4 even more effectively suppresses interference noise or so that interference noise is avoided.

(19) For the adaptation of the longitudinal edges 2a, 2b and/or end sections 2c, 2d according to the invention, there are several (alternative) possibilities available. A particularly simple method of adaptation includes the fact that the vertical profile in the transverse direction (transverse profile) of the one longitudinal edge 2a, 2b with a negligible depth/length in the longitudinal direction of the image 3 is copied and inserted in place of the other longitudinal edge 2a, 2b, so that the originally detected other longitudinal edge 2b is replaced. For example, the front longitudinal edge 2a is superposed over the rear longitudinal edge 2b and the rear longitudinal edge 2b is thus replaced. Naturally, the reverse is also possible with regard to the front and rear longitudinal edges 2a, 2b. The method makes it possible, when the two longitudinal edges 2a, 2b are brought together to produce the annular image 3a, at least the two profiles of the longitudinal edges 2a, 2b coincide and the adaptation can be carried out rapidly. The copying and replacing can be carried out by means of a graphics program. For example, it is also possible to use the specific numerical vertical values, particularly if the image 3 exists in the form of a data matrix or data table.

(20) In addition, an end section 2c (i.e. its surface contour) can also be copied and inserted in place of the other end section 2d so that the vertical value distribution of the other end section 2d is replaced. By contrast with the method described further above, therefore, not only the (outermost) longitudinal edge 2a, 2b with a negligible depth/length in the longitudinal direction is copied and replaced, but also an (end) section with a defined length in the longitudinal direction. The predetermined length of the end section 2c whose surface contour is being copied can, for example, be determined based on the fact that two positions/points on the two end sections 2c, 2d that are well matched to each other are defined and the end section 2c, 2d to be copied is copied up to this point. This method can also be carried out rapidly and in a non-laborious fashion.

(21) In addition, the surface contours in one of the two end sections 2c, 2d or in both of the end sections 2c, 2d can be adapted, with the surface contour being digitally modified as in the options described above. The predetermined length of the end sections 2c, 2d in which the surface contour is changed can be determined as a function of the number of extreme values (minima and/or maxima) per unit area. In addition or alternatively, slope values that are adjacent to the minima and/or maxima can be used for defining the length of end sections 2c, 2d to be adapted.

(22) A particularly simple method for adapting the surface contouror more precisely the vertical valueswithin the end regions 2c, 2d is based on the fact that a user is shown a visual display of the digital image 3 and uses digital graphics applications to adapt the heights and depths of the image 3 within the two end sections 2c, 2d to one another. In the simplest case, this can take place, for example, manually by means of an image processing program. The adaptation can also take place by means of 3D design tools, for example by means of spline adaptation methods or automated adaptation routines that are based on the adaptation possibilities described above.

(23) Preferably, the predetermined length L.sub.EB of the end sections 2c, 2d can be essentially 1% of the total length L of the image 3 of the detected section 1, particularly with an extreme value density of greater than 5000 extreme values per m.sup.2. Preferably, the predetermined length L.sub.EB of the end regions 2c, 2d can be 10% of the total length L of the image 3 of the detected section 1 if the extreme value density is less than 5000 extreme values per m.sup.2. In this context, extreme values refer to local minima and/or maxima.

(24) In addition, the adaptation of the longitudinal edges 2a, 2b and/or of the end sections 2c, 2d can also be carried out by means of a predetermined deviation value . The deviation value is mathematically calculated based on the quotient of a difference between two vertical values that can be situated adjacent to each other and one of the two vertical values of the difference. With vertical values that are directly adjacent, a very small deviation value is preferred, e.g. less than 1% or less than 5%. This achieves a transition 4 with very good adaptation between the adjoining parts. With vertical values that are not directly adjacent or with less restrictive requirements on the adaptation, the deviation value can also be up to 50%.

(25) In the adaptation, naturally only one of the two end regions 2c, 2d can be adapted to the respective other end region 2c, 2d or both end regions 2c, 2d together can be adapted to each other.

(26) The step of manufacturing the road surface covering element 5 by means of a 3D printing method and/or 3D milling method includes the fact that the digital image 3 or the annular image 3a is produced by means of a suitable 3D printing and/or milling device. 3D printing methods are essentially based on the fact that the three-dimensional image 3 is built up in layers. Depending on the method, the layer thickness can lie between a few micrometers and approx. mm. The layer thickness influences the vertical resolution, with a thicker layer thickness resulting in a lower resolution.

(27) Three-dimensional manufacturing by means of stereolithography in particular produces very smooth surfaces of the three-dimensional road surface covering element 5. The road surface covering element 5 is produced in a basin that is filled with (preferably) liquid synthetic resin and a UV laser periodically hardens the synthetic resin. The hardening is carried out in layers. Overhanging, hardened components of the road surface covering element 5 do not support themselves so that a support structure of another material must be created, which is removed after the road surface covering element 5 is manufactured. Advantageously, stereolithography can also make use of transparent material.

(28) Both plastics and metal can be processed using laser sintering. In laser sintering, a pusher distributes the raw material in powdered form in the predetermined layer thickness on a printing table. Then a laser hardens the powder at the predetermined points by heating it. The process is repeated until the road surface covering element 5 is completely formed. Protruding parts can also be manufactured without a second supporting material. The often rough surface that is produced with laser sintering can be smoothed out by means of a plastic coating.

(29) Road surface covering elements 5 can also be manufactured using a 3D printer that uses a combination of laser sintering and two-dimensional printing with an inkjet printer. The print head, which can also distribute various colors of ink, dispenses ink onto a thin layer of gypsum-like powder; a bonding agent that is mixed in with the ink allows the printed areas to harden. It is thus possible to produce the road surface covering element 5 layer by layer. The finished road surface covering element 5 can be impregnated with synthetic resin in order to achieve an additional stability and/or to improve surface quality.

(30) Road surface covering elements 5 can also be manufactured using the particularly simple and economical-to-implement fused deposition modeling method in which a melted plastic is sprayed from a nozzle so that the desired form of the road surface covering element 5 is drawn in layers with a strip of soft plastic. In a particularly preferred embodiment, ABS plastic is used for this.

(31) All of these 3D manufacturing processes advantageously permit a rapid manufacture of the road surface covering elements 5 with a very precisely detailed reproduction of the surface contour of the road surface covering.

(32) It is also possible to manufacture the road surface covering element 5 by means of a CNC milling cutter, which mills the three-dimensional road surface covering element 5 from a blank preferably made of metal or ceramic. To accomplish this, it is particularly preferable for the image 3or more precisely the annular image 3ato be in the form of a CAD file. In 3D milling, it is advantageous for the road surface covering element 5 to be milled out of a single blank so that very favorable strength values of the road surface covering element 5 are achieved.

(33) As shown in FIG. 3, the 3D manufacturing process can be used to print the annular image 3a in one piece or, as shown in FIG. 4, to print individual arc segments 5a through 5h. In addition, the annular image 3a can also be printed in one piece and then divided. To accomplish this, for example predetermined breaking points can also be produced in the printing process or else the division can be carried out, for example, by sawing or other cutting techniques.

(34) In summary, the method according to the invention makes it possible to rapidly and precisely manufacture an exact reproduction of a surface contour of a road surface covering in the form of a road surface covering element 5 for rollers of chassis dynamometers. The adaptation of the transition 4 between the two longitudinal edges 2a, 2b or end sections 2c, 2d can be carried out with very little work and interference noise that is produced particularly when rolling over a non-adapted transition 4 can be optimally reduced. 1 strip-shaped section of a road surface covering 2a front longitudinal edge of the detected section 2b rear longitudinal edge of the detected section 2c front end section of the detected section 2d rear end section of the detected section 3 image of the detected section 3a annular image 4 transition 5, 5a, 5b, . . . road surface covering segment(s) 6 optical detection means L length of the detected road surface covering section B width of the detected road surface covering section U.sub.R circumference of the rollers of a chassis dynamometer B.sub.R width of the rollers of a chassis dynamometer L.sub.EB length of the end region predetermined deviation value