EP3166801A2

EP3166801A2 - Tyre comprising a mark formed by a plurality of linear patterns

Info

Publication number: EP3166801A2
Application number: EP15734417.7A
Authority: EP
Inventors: Olivier Muhlhoff
Original assignee: Michelin Recherche et Technique SA Switzerland; Compagnie Generale des Etablissements Michelin SCA; Michelin Recherche et Technique SA France
Current assignee: Compagnie Generale des Etablissements Michelin SCA
Priority date: 2014-07-11
Filing date: 2015-07-10
Publication date: 2017-05-17
Also published as: CN106536230B; JP2017520463A; BR112016031033A2; FR3023509B1; FR3023509A1; US20170157995A1; CN106536230A; WO2016005573A2; WO2016005573A3

Abstract

The invention relates to a tyre (1) made from rubber-like material, comprising a tread (2) and a sidewall (3), the tread (2) and/or sidewall (3) of the tyre comprising a mark (4). The mark (4) is formed by a plurality of linear patterns that are of the same material as the tyre, said patterns being parallel to one another and spaced apart by a pitch P less than or equal to 1 mm, and each linear pattern having a length. The width of all or part of the linear patterns (41) is varied (Lt) once or more along the length thereof, such as to define the mark.

Description

PNEUMATIC COMPRISING A MARKING COMPRISING A

PLURALITY OF LINEAR PATTERNS

FIELD OF THE INVENTION

[01] The present invention relates to a tire for a motor vehicle having a tread and a sidewall, said tire comprising on the tread and / or said sidewall a marking.

STATE OF THE ART

[02] For aesthetic reasons, the tires have markings on their tread and / or their sidewall which are increasingly made from source images that are printed and which are in particular photographs, or works of art. artists, graphic designers. The source images are composed of different shades of color that can be transposed into different gray levels.

[03] WO 2013/1 13526 discloses a tire having a marking on a sidewall. This marking consists of a realistic representation of a photograph. More particularly, the marking is composed of a plurality of adjacent ribs having a generally triangular section. The space between two adjacent ribs is filled with a complementary material to a certain level of filling. The level of filling of the complementary material locally determines a gray level of the marking. [04] The object of the invention is to propose a solution for producing on a tire complex markings, of photographic representation type, in a simpler and more economical manner than in the prior art. DEFINITIONS

[05] "Pneumatic" means all types of elastic bandages subjected to internal pressure or not.

[06] "Rubber material" means a diene elastomer, that is to say in known manner an elastomer derived from at least in part (ie homopolymer or copolymer) of monomers dienes (monomers carrying two carbon-carbon double bonds, conjugated or not).

[07] "Tread" of a tire means a quantity of rubber material delimited by lateral surfaces and by two main surfaces, one of which, called a tread surface, is intended to come into contact with a road surface. when the tire is rolling.

[08] "sidewall" of a tire means a side surface of the tire disposed between the tread of the tire and a bead of the tire. [09] "Strand" means a filamentary element whose height is at least equal to 2 times the diameter of a disc of the same area as the average section of the strand.

[10] "Slats" means elongate strands having a length at least twice their height. [11] Linear pattern means one or more geometric elements protruding with respect to the tire such as a strand or a lamella, and / or a plurality of geometric elements recessed relative to the tire such as a hole or a streak .

[12] By linear pattern "come from material with the tire" is meant that this pattern is in the same material as the tire.

[13] By "brightness" is meant the parameter that characterizes a surface to reflect more or less light. The luminosity is expressed according to a scale ranging from 0 to 100 according to the color model L * a * b * established by the CIE (International Commission of Lighting) in 1976. The value 100 represents the white or the reflection total; the value 0, black or total absorption. In this color model a * and b * are chromaticity coordinates. The color model L * a * b * thus defines a chromaticity diagram. In this diagram, a * and b * indicate the direction of the colors: + a * goes to red, -a * to green, + b * to yellow, and -b * to blue. The center of the diagram is achromatic. As the values a * and b * increase, and as we move away from the center of the diagram, the saturation increases.

SUMMARY OF THE INVENTION

[14] The invention relates to a rubber tire comprising a tread and a sidewall, said tire comprising on said tread and / or said sidewall a marking. The marking is formed by a plurality of linear patterns integral with the tire. These patterns are parallel to each other and are spaced apart by a pitch P less than or equal to 1 mm. Each linear pattern has a length L. All or part of the linear patterns have in their length L one or more variation (s) of width so as to define the marking.

[15] The invention thus proposes to carry out a complex marking on a tire. This marking is made from a plurality of linear patterns, these patterns having in their length one or more variation (s) of width. Depending on the given width variations, it is possible to give the marking a certain definition and, for example, it is possible to reproduce with sufficient precision the details of a photograph. Since the patterns are formed directly on the tire, it is not necessary to report a complementary material as in the prior art. The realization of the complex marking on the tire is thus simplified.

[16] According to non-limiting embodiments, the tire may further comprise one or more additional characteristics from the following: [17] In a non-limiting embodiment, the marking is a representation of a photograph. [18] Thanks to the invention, it is thus possible to perform complex markings, giving the tire a certain visual attractiveness.

[19] In a non-limiting embodiment, the linear patterns are arranged obliquely in the marking. [20] This makes it possible to obtain an aesthetic effect of marking on the tire. Note that these linear patterns can follow the curvature of the tire surface.

[21] In a non-limiting embodiment, a linear pattern is composed of one or more protruding elements or one or more recessed elements with respect to the tread and / or said sidewall.

[22] This provides a "velvet" pattern at the touch or visual level. [23] In a non-limiting embodiment, all or part of the protruding elements are strands distributed in the linear pattern at a density of at least one strand per square millimeter (mm ² ), each strand having a mean cross-section between 0.0005 mm ² and 1 mm ² .

[24] In a non-limiting embodiment, all or part of the protruding elements are slats substantially parallel to each other, the pitch of the slats in the linear pattern being at most equal to 0.5 mm, each slat having an average width. between 0.02 mm and 0.25 mm. [25] In a non-limiting embodiment, all or part of the protruding elements form side parallelepipeds between 0.05 mm and 0.5 mm, with a height of between 0.05 mm and 0.5 mm, the distance between two adjacent parallelepipeds in the linear pattern being between 0.05 mm and 0.5 mm.

[26] In a non-limiting embodiment, the hollow elements form openings on the tread and / or the sidewall and the linear pattern comprises a plurality of openings, these openings being distributed in the linear pattern according to a density at least equal to one opening per square millimeter (mm ² ), these openings having equivalent diameters of between 0.01 mm and 1.2 mm.

BRIEF DESCRIPTION OF THE DRAWINGS [27] Other features and advantages of the invention will emerge from the following description, given by way of example, without limitation, with reference to the accompanying drawings, in which: FIG. perspective of a portion of a tire having a tread and a sidewall, said side including a marking according to the invention according to a first embodiment; FIG. 2 diagrammatically represents a perspective view of a portion of a tire comprising a tread and a sidewall, said tread comprising a marking according to the invention according to a second embodiment; FIG. 3 diagrammatically represents an enlarged view of the marking of FIG. 1 or FIG. 2, said marking being composed of a plurality of strips each comprising a linear pattern of variable width locally; Figure 4 shows the plurality of bands of Figure 3 without the linear patterns; Fig. 5 shows a band of Fig. 4, said band being composed of a plurality of parts; FIG. 6 represents a part of a band of FIG. 5, said part comprising a linear pattern of variable width; FIG. 7 represents a linear pattern of FIG. 3 according to a first nonlimiting variant of a first embodiment of the linear pattern according to which the linear pattern is composed of protruding elements; FIG. 8 represents a linear pattern of FIG. 3 according to a second nonlimiting variant of a first embodiment of the linear pattern according to which the linear pattern is composed of protruding elements; FIG. 9 represents a linear pattern of FIG. 3 according to a third nonlimiting variant of a first embodiment of the linear pattern according to which the linear pattern is composed of protruding elements; FIG. 10 represents a linear pattern of FIG. 3, according to a second embodiment of the linear pattern according to which the linear pattern is composed of hollow elements; Fig. 11 is an enlarged view of a recess of a recessed member of Fig. 10; Figure 12 is a flowchart of a method of making a marking such as the marking of Figure 3 on a tire from a source image; and Fig. 13 is a flowchart of the method of Fig. 12, said method comprising additional steps.

[28] In the following description, substantially identical or similar elements will be designated by identical references. [29] In Figures 1 and 2 is shown a portion of the tire 1 having a tread 2 and a sidewall 3, said tire 1 comprising on the tread 2 and / or said flank 3 a marking 4. [30] In the nonlimiting example illustrated, said marking 4 represents a unit of meaning which is here an eye.

[31] Figure 1 shows a portion of the tire 1 having a tread 2 and a sidewall 3 according to a first non-limiting embodiment. According to this mode, the flank 3 comprises on its surface 30 the marking 4. [32] Figure 2 shows a portion of the tire 1 having a tread 2 and a sidewall 3 according to a second non-limiting embodiment. The tread 2 has grooves 21 (also called tread patterns) and a tread surface 20 intended to come into contact with the ground. According to this mode, the tread 2 has on its tread 20 the marking 4.

[33] According to the two modes of FIGS. 1 and 2, as illustrated in the enlarged view of the marking (FIG. 3), said marking 4 is composed of a plurality of strips 40, each strip 40 comprising a linear pattern 41 whose Lt width can vary locally. Thus, all or part of the linear patterns 41 have in their length one or more variations of width so as to define said marking 4.

[34] Note also that the variation of said width can reproduce levels of gray Nx. Marking 4, seen by the observer, thus has variations of gray. In a nonlimiting embodiment illustrated in FIG. 3, the width Lt of a linear pattern 41 varies with respect to the median line of a strip 40.

[35] In a non-limiting embodiment, as can be seen in Figure 3, the linear patterns 41 are arranged obliquely in the marking 4. This allows to determine the aesthetics that we want to give the marking. In other non-limiting embodiments, it is conceivable to have linear patterns 41 horizontal or vertical. [36] Note that the linear patterns 41 may have a certain curvature as they follow the surface of the sidewall 3 or the tread 2. They thus conform to the shape of the tire 1.

[37] In a non-limiting embodiment, a pattern 41 is linear throughout the marking 4. It extends over the entire marking 4. Thus, it extends from a first limit of the marking 4 to a second limit , the boundaries of the marking 4 being defined by the four sides of said marking 4 in the example taken from FIG. 3. In the case where the linear pattern is vertical or horizontal, the first limit is opposite the second limit.

[38] Figure 4 illustrates the strips 40 of Figure 3 without the linear patterns 41.

[39] In a non-limiting embodiment, as can be seen in FIG. 4, the strips 40 are arranged obliquely in the marking 4 as the linear patterns 41 illustrated in FIG.

[40] Furthermore, in a non-limiting embodiment, the width Lb of a strip is between 0.03mm and 1mm. This allows a marking at the industrial level in which the object, here the unity of meaning, is visible. Indeed, in the case where said width Lb would be smaller, an observer of the tire would no longer perceive the details of the marking (here of the unity of meaning which is an eye), and therefore, could not know what the marking represents (unity of meaning, or other abstract object). It is the same in the case where said width is too large.

[41] In a non-limiting embodiment, the width Lb is equal to 0.1 mm. This makes it possible to have a good compromise between the definition of the marking obtained, seen by an observer at a minimum distance of 1m, and its resistance to mechanical aggression.

[42] In the example taken from FIG. 4, the strips 40 are generally of the same width Lb. The strips framing the linear patterns, it makes it possible to achieve said patterns more easily at the industrial level. In another non-limiting embodiment, the strips 40 are of different width Lb. [43] FIG. 5 illustrates a band of FIG. 4. Said band 40 is composed virtually of a plurality of parts 50, a part 50 defining a determined gray level Nx which is produced by the local variation of the width Lt of said Linear pattern 41 in said portion 50. Such a portion 50 is shown in Figure 6. As can be seen, the linear pattern 41 varies within said portion 50 and includes a width of size Ltl on one side of the part 50 which is different from the size Lt2 on the other side of the part in the example of FIG. 6. In the nonlimiting example illustrated, the width Lt varies around a center line 43 of the strip 40 (and therefore part 50).

[44] Thus, a gray level Nx is equal to the ratio between the area of said linear pattern 41 in the portion 50 comprising said linear pattern 41, divided by the total area of said portion 50. Thus, the surface proportion of the linear pattern 41 relative to the surface of all of the portion 50 which defines a level of gray Nx.

[45] Thus, by local variation of the width of a linear pattern 41 is meant that the linear pattern 41 is not uniform throughout the band 40. Its width Lt may vary from one part 50 to another or within one part 50. It may be noted that one or more linear patterns 41 may have a constant width Lt all along the strip 40 while the other linear patterns 41 have a width Lt which varies locally.

[46] In non-limiting embodiments, a linear pattern 41 is composed of one or more protruding elements or one or more recessed elements with respect to the tread 3 and / or said sidewall 2. [ 47] Note that in a non-limiting embodiment, a linear pattern 41 (such as strands or slats) is integral with the tread and / or said flank 3, namely it is made in the same rubber material as said tread and / or said sidewall. This produces a marking without adding another material. [48] A linear pattern 41 contrasts with the tread 2 and / or the sidewall 3 so that the marking 4 is clearly visible by an observer of the tire.

[49] Various alternative embodiments of the protruding elements are presented hereinafter. The effect of these elements protruding is to "trap" a large amount of incident light rays that meet the linear pattern 41. In this first embodiment (protruding elements), the linear pattern 41 allows to obtain, from on the one hand, a visual "velvet" type because the protruding elements absorb the light and thus make the linear patterns 41 black and therefore the marking 4 more in contrast with the tire, and secondly, a touch of type "velvet", said elements in protuberance providing a marking 4 pleasant to the touch.

[50] Figure 7 illustrates a portion of the linear pattern 41 according to a first non-limiting embodiment of the first embodiment. In this variant, all or part of the protruding elements are strands 8 distributed in the linear pattern 41 in a density at least equal to one strand per square millimeter (mm ² ), each strand having an average section S of between 0.0005 mm ² and 1 mm ² . It should be noted that the average section of each strand corresponds to the average of sections S measured at regular intervals from the base of the strand. The strands 8 have a generally conical shape with a section decreasing in the height Hb of these strands.

[51] Figure 8 illustrates part of the linear pattern 41 according to a second non-limiting embodiment of the first embodiment. In this variant, all or part of the elements in protrusion are slats 9 substantially parallel to each other, the pitch P of the slats in the linear pattern 41 being between 0.1 mm and 0.5 mm, each slat 9 having an average width between 0.02 mm and 0.25 mm. It will be noted that the average width corresponds to the average of the widths 1 measured at regular intervals in the height H1 of the lamella, the height of each lamella being between 0.05 and 0.5 mm.

[52] In another non-limiting embodiment, the linear pattern 41 is composed only of a single plate 9 whose width may vary locally. [53] In another variant embodiment, the linear pattern 41 comprises a combination of strands 8 and slats 9.

[54] Figure 9 illustrates a portion of the linear pattern 41 according to a third non-limiting embodiment of the first embodiment. In this variant, all or part of the protruding elements form parallelepipeds 10 having a side C of between 0.05 mm and 0.5 mm, with a height Hp of between 0.05 mm and 0.5 mm, the distance Dp between two adjacent parallelepipeds 10 in the linear pattern being between 0.05 mm and 0.5 mm.

[55] In another alternative embodiment, the linear pattern 41 comprises a combination of the raised elements 8, 9 and 10, or 8 and 10, or 9 and 10 described above.

[56] According to the second nonlimiting embodiment, the linear pattern

41 comprises a plurality of recessed elements 12 with respect to the surface where said linear pattern 41 is located, namely the surface 30 of the sidewall 3 in the case illustrated in FIG. 1 or the tread surface 20 of the tread 2 in the case illustrated in Figure 2. In a first non-limiting embodiment, the hollow elements 12 (also called holes) are composed of openings 13 on the surface and associated cavities 14 extending into the depth of the surface 20 and / or 30. [57] Thus, the linear pattern 41 comprises a plurality of openings 13 in the surface, said openings 13 being distributed in the linear pattern 41 in a density at least equal to one opening per square millimeter (mm ² ) and having on the surface diameters Dt equivalents of between 0.01 mm and 1.2 mm.

[58] The openings 13 extend in the depth of the surface to form cavities 14.

[59] The effect of these cavities 14 is to "trap" a large amount of the incident light rays that meet the linear pattern 41, but also to provide greater durability of the texture 5. Indeed, as the cavities 12 are hollow in the surface, the impact of mechanical aggression on the texture, such as friction of a pavement is lower than for protuberances. In this second embodiment, the linear pattern 41 provides a visual type "velvet" because the cavities absorb light and thus make the linear patterns 41 black and therefore the marking 4 more in contrast with the tire.

[60] In a non-limiting embodiment, all or part of the cavities 14 has a depth of at least 0.1mm. In a non-limiting embodiment variant, all or part of the cavities 14 has a depth of between 0.2 mm and 0.6 mm. In this way, it is ensured that a large quantity of incident light rays which meets the texture 5 is trapped by the linear pattern 41 and, since the depth of the cavities is limited, it is also avoided to degrade the mechanical strength of the surface 20 and / or 30.

[61] Figure 10 illustrates the linear pattern 41 according to a non-limiting variant of this second embodiment. In this variant, all or part of the cavities 14 are in the form of cones which extend in the depth of the surface 20 and / or 30 and open on the surface forming circular openings 13. The cavities 13 thus have a section which decreases in the depth of the surface. In this way, the contrast of the linear pattern 41 is improved with respect to the tread and / or the sidewall. It will be noted that in this variant, the openings 13 of the cavities 14 do not touch each other. The openings 13 are separated by intermediate zones 15. In addition, the openings 13 are evenly distributed over all or part of the surface 20 and / or 30 so that the distance d between each opening of the linear pattern 41 is generally similar.

[62] FIG. 11 is a zoom on a cavity 14 of a hollow element 12 of FIG. 10. In one non-limiting embodiment, all or part of the cavities has at least one wall 16 which, according to a view in FIG. section, forms an angle β between 10 ° and 60 ° with respect to a direction Z perpendicular to the linear pattern 41.

[63] Whenever a light ray encounters a wall 16 of the cavity 14, the latter is reflected by said wall 16. The direction of reflection of the light beam depends on the initial direction of this light beam and the angle of inclination of the wall 16. Thus, depending on this initial direction and this angle of inclination, the light beam can be returned to another wall 16 of the cavity. Conversely, the light ray can be returned outside the cavity, for example directly to an observer. In the first case, the light ray "gets lost" in the cavity and it will no longer be perceptible by the eye of an observer. In the second case, the observer can perceive the light ray and the texture may then appear to be lighter and therefore less in contrast with the tread and / or the sidewall. By choosing a cavity 14 having at least one wall 16 which forms an angle β of between 10 ° and 60 °, it is ensured that a large part of the light rays entering the cavity 14 will be absorbed by this cavity under the effect of multiple reflections inside the cavity. In this way, the contrast of the linear pattern 41 with respect to the tread and / or the sidewall is improved, while maintaining the same occupancy rate of the cavities in the linear pattern 41. In addition, with this inclination of wall, the overall strength of the linear pattern is improved overall, especially during repeated friction with the roadway.

[64] In a second non-limiting embodiment of the second embodiment in which the linear pattern 41 is composed of one or more recessed elements, the recessed elements are composed of a plurality of streaks (not shown). extending in the depth of the surface 20 and / or 30. Thus, a linear pattern 41 may be composed of a plurality of streaks of locally variable width or a linear pattern 41 is composed of only one streak (not illustrated) whose width may vary locally. [65] When all or part of a strip 40 does not have a linear pattern 41, a white color is obtained. In this case, the white color is achieved by a smooth surface (that of the tread 2 and / or the sidewall 3) which has a very low surface roughness Ra parameter. In a non-limiting example, the arithmetic mean-deviation parameter Ra representative of the surface roughness is less than 30μιη. This smooth surface returns a maximum of incident light. The amount of light returned by all or part of a strip 40 of white color is thus maximized.

[66] The marking 4 on tire 1 made of rubber material comprising a tread 2 and a sidewall 3 is made from a source image 4 'by means of an MTH manufacturing method illustrated in FIGS. 12 and 13. [67] Note that the source image 4 'is an image in the form of a computer file such as files of type bitmap or jpeg (also called digital image). Moreover, its resolution is generally quite high, for example of the order of 3000 pixels by 3000 pixels. [68] As illustrated in FIG. 12, the MTH production method comprises: a first processing of the source image 4 'into a target image 4 "composed of a plurality of lines 42, all or part of the features presenting in their length one or more width variations Lt so as to define said source image 4 '(illustrated step F 1 (4', 4 ", 42, Lt));

selecting one or more linear patterns 41 (illustrated step SELEC (8,9,10,12,41)); and

performing the marking 4 from said target image 4 ", the marking comprising a plurality of linear patterns 41 (step illustrated GRAV (4, 4", 41).

[69] The steps are described in more detail below.

[70] The first treatment of the source image 4 'will make it possible to obtain a target image 4 "composed of a plurality of lines 42 corresponding to the linear patterns 41 to be made on the tire 1, all or part of the lines 42 presenting in their length one or more width variations Lt so as to define said source image 4 'During this processing, the bands 40 of the target image 4 "are also defined. These strips 40 will thus allow the distribution and positioning of the lines 42 and thus the distribution and positioning of the linear patterns 41 in the marking 4 and help the industrial realization of said marking 4. [71] Thanks to the local variation of the width Lt of the lines 42 on the target image 4 ", thus faithfully reproducing the object of the source image 4 'The local variation of the width Lt of said line 42 will also make it possible to define the level of gray Nx in the end, As seen by an observer, during this step, on the one hand, the aesthetics of the marking 4, which will be carried out on the tire 1, are determined by positioning (oblique, horizontal, vertical) strips 40 in said image. 4 "and on the other hand, the different gray levels of the source image 4 'are produced by means of the lines 42 made in said bands, the different shades of gray being produced by the local variation of the lines 42 in the different parts 50. This processing is done by an appropriate image processing software.

[72] When selecting one or more linear patterns 41, one selects the protuberance or recessed elements previously seen. The selected linear patterns 41 will thus be made on the marking 4 as a function of the lines 42 of the target image 4 "and in particular according to their positioning (oblique, horizontal, vertical), and their variation of their width.

[73] In a non-limiting embodiment, the realization of the marking

4 is carried out by laser etching by means of a laser engraving machine M on a mold or directly on said tire 1 by means of the target image 4 "which is inputted as the input parameter of the machine M.

[74] The etching of the marking 4 is in a first embodiment carried out on a mold. In a second embodiment, it is carried out directly on said tire 1. Thus, the etching of the marking 4 is performed before or after firing of the tire 1. Said etching comprises the etching of a plurality of linear patterns 41 to define the marking 4.

[75] The laser engraving machine M is in a non-limiting example a pulsed laser which comprises in a non-limiting example a power of 50 W and a speed of 1000mm / s and operates at a frequency of 50kHz.

[76] In a non-limiting embodiment, the method further comprises defining a pitch Pa between two linear patterns 41 which is set on the laser engraving machine M (SELEC illustrated (Pb)). Thus, the pitch Pa is defined as input parameter of the machine M. In a non-limiting embodiment, the pitch Pa is between 0.2mm and 1mm. This allows a realization at the industrial level. It will be noted that the smaller the pitch Pa, the more accurate the marking 4 will be. In a non-limiting embodiment, the pitch between two linear patterns Pa (also called etching) corresponds to the width Lb of a strip 40. A pitch Pa between two patterns adjacent linear lines 41 is defined with respect to a median 43 passing through each linear pattern 41 as illustrated in FIG.

[77] This additional step (illustrated in dashed lines) can be performed at any time in the production method, for example after the first treatment.

[78] Note that if the source image 4 'is in color, in a non-limiting embodiment, the method MTH further comprises a transformation of the source image 4' in color into a source image 4 'in levels gray (step shown TRANS_CO (4 ', Nx) in FIG. 13).

[79] Furthermore, in a non-limiting embodiment, the method

MTH further includes trimming the source image 4 '. This makes it possible to better highlight the unity of meaning in the source image 4 'once it is transferred onto the tire (illustrated step DETOUR (4') in FIG. 13).

[80] In a non-limiting embodiment, the method further comprises a second processing (step illustrated F2 (4 ', p, Nx, L *) in FIG. 13) in which parameters p of the source image 4 are adjusted such that at least five percent of the Nx gray levels of said source image 4 'have a brightness value L * of less than 20 and at least five percent of the gray levels Nx of said 4 'source image have a brightness value L * greater than 80. These p parameters are in a non-limiting example contrast and / or brightness and / or the gamma parameter.

[81] Thus, the source image 4 'is adjusted so as to obtain a marking 4 on the tire which is closest to the source image 4', in particular thanks to the adjustment of the gamma parameter (also called gamma correction). It should be noted that the gamma correction can be controlled by means of a histogram of the pixel values of the source image 4 '.

[82] The rubber components of the tires are typically anthracite gray in color. The maximum amplitude of contrast on these materials is low because the maximum brightness is of the order of 25. This step therefore maximizes the contrast made on the tire for an observer, on the support that is the tire with its rubber material. The loss of the maximum amplitude of contrast imposed by the material is thus minimized. [83] Adjusting the contrast parameter makes it easy to see the difference between dark gray levels and light gray levels.

[84] This second treatment makes it possible to obtain a marking 4 on a tire which has a luminosity L * of between 8 and 25. Thus, the lightest areas of the marking 4 come close to the brightness 25 while the darkest areas marking 4 are close to the brightness 8. This produces gray levels on the marking 4 which are sufficiently visible on the tire so as to bring out said marking 4 on the tire.

[85] The step of transforming the color image (shown in dotted lines) is performed before the second processing. The clipping step (shown in dotted lines) can be done before or after the second treatment.

[86] The first treatment previously described is done on the source image

4 'obtained after these three additional steps.

[87] Finally, in a non-limiting embodiment, the method MTH further comprises an adaptation of the resolution RI of said source image 4 'as a function of the desired resolution R2 of the marking 4 on said tire 1 and a step Pa between two linear patterns 41 (step shown in dotted line ADAPT (4 ', RI, 4, R2, Pa) in Figure 13). [88] This makes it possible to master the final rendering before the etching is carried out during simulations and computer processing, as well as to prepare the piloting of the etching machine in adequacy.

[89] The resolution RI is the number of pixels that make up the source image 4 'in height and width. Resolution R2 is the number of millimeters that make up the marking 4 in height and in width on the tire 1, namely the space in millimeters on the tire 1 dedicated to said marking 4.

[90] The source image 4 'must indeed have a resolution RI adapted to the visual effect ultimately sought on the tire 1. [91] The adaptation of said resolution RI according to the resolution R2 comprises the sub-components. following steps :

[92] In a first substep (illustrated CALC (R2 ', R2, Pb) in FIG. 13), the resolution R2' is calculated in pixels of a digital image corresponding to the resolution R2 in millimeters of the image target 4 to be made on the tire 1. [93] For this purpose, the resolution R2 'is equal to said resolution R2 divided by said pitch Pb. Thus, in a nonlimiting example, if the space available to write a marking 4 on the tire 1 is 30mm * 30mm (resolution R2) and that the pitch Pa of the etching is set at 0.3mm (in the example taken the width of a strip 40), this means that it is possible to engrave on the tire a marking corresponding to a resolution image R2 'equal to 30mm / 0.3mm = 100pixels * 100pixels. Thanks to this formula, a transcription of a physical space available on the tire 1 is carried out at a resolution of a digital image.

[94] In a second step (illustrated as MODIF (R1, R2 ') in the figure

13), as a function of the resolution R2 'in calculated pixels corresponding to the resolution R2 of the marking 4, the resolution RI of the source image 4' is modified. Thus, the resolution RI which was at the beginning of 3000 * 3000pixels is modified so as to obtain a new resolution RI equal to 100 * 100pixels. Thus, 30 pixels (= 3000/100) of the source image 4 'with the old resolution RI correspond to 1 pixel of the reduced source image 4' with the new resolution RI. This means that the gray level Nx defined by a pixel in the reduced source image 4 'is equal to the gray level Nx defined by a square of 30 * 30pixels in the source image 4' obtained just after the second processing in the illustrated example of Figure 13.

[95] This additional ADAPT adaptation step (4 ', RI, 4, R2, Pb) is performed before the image processing step FR1 (4', 4 ", 41, Lt). [96] Figure 13 illustrates the process of MTH realization of a marking 4 incorporating these additional steps (transformation of the image into color, trimming and adaptation, step selection).

[97] Thus, in a first step 1), the color source image 4 'is transformed into a source image 4' comprising several levels of gray Nx.

[98] Then, in a second step 2), we cut the image 4 'so as to keep only the unity of meaning, the eye, in the example taken.

[99] In a third step 3), the parameters of said source image 4 'are adjusted. [100] In a fourth step 4), the resolution RI of the source image 4 'is adapted according to the desired resolution R2 of the marking 4 to be made on the tire 1. This step comprises:

[101] - the sub-step 40) of calculating the resolution in pixels R2 'of an image as a function of the resolution in millimeters of the marking 4 on the tire that one wishes to achieve, namely the calculation of the resolution in pixels according to the space dedicated to said marking 4 on the tire;

[102] - the sub-epate 41) to change the resolution RI of the source image 4 'as a function of the calculated pixel resolution R2'. The modification here corresponds to a decrease in the resolution RI. [103] In a fifth step 5), the source image 4 'whose resolution RI has been modified to process the target image 4 "composed of the plurality of bands 40 is processed. The bands 40 and the lines are thus created. 42 of width Lt locally variable in said bands 40, so as to define the object of the source image 4 'and therefore the different levels of gray Nx of the source image 4' whose resolution has been modified. In a sixth step 6), the laser engraving machine M is adjusted with the value of the pitch Pa, namely here with the value of a width Lb of a strip 40.

[105] In a seventh step 7), the protuberance and / or recessed elements constituting the linear patterns 41 are selected. [106] In an eighth step 8), the machine M realizes the linear patterns

41 so as to carry out the marking 4 on the tire 1.

[107] Note that the places where the band 40 does not have a linear pattern 41 correspond to the white color. As the white color is produced by the smooth surface of the tread and / or the side on which the marking 4 is located, the machine M does not engrave these places but only engraves the linear patterns 41.

[108] Thus, thanks to this method of realization MTH, a marking is carried out

4 which is close to the source image 4 'so that an observer of the tire will see a marking of sufficient contrast to recognize the object of the marking. The marking 4 is composed of a plurality of gray levels which form between them a contrast which limits the final contrast obtained that the observer can see at a distance of lm minimum.

[109] The invention is not limited to the examples described and shown and various modifications can be made without departing from its scope.

[110] Thus, according to another non-limiting embodiment, the slats 9 of Figure 8 may be discontinuous. They have a flat part between them. In addition, they may have section differences between them. In addition, the slats may have curvatures or angles, especially in their length. They can also be of variable length.

[111] Thus, according to another variant of non-limiting embodiment, the openings 13 of Figure 10 may have the shape circular, square, or polygonal (for example hexagonal) and the corresponding cavities 14 a cylindrical shape, parallelepipeds, or even polygons. With these two last structures (square or polygonal), it is possible to more easily organize the openings 13 relative to each other so as to limit the area of the intermediate zones 15 between these openings. With such forms of openings, it is possible to arrive more easily at substantial rates of occupancy of the openings. [112] Thus, according to another non-limiting embodiment, the tread 2 of the tire and / or the sidewall 3 may each comprise one or more markings 4.

[113] Thus, according to another non-limiting embodiment, instead of using a velvet type technology to achieve a linear pattern 41, a linear pattern 41 is achieved by simple disbursement performed by laser. In a non-limiting example, the disbursement has a depth of between 0.1 and 0.5 mm.

[114] Thus, according to another nonlimiting variant embodiment, a linear pattern 41 may vary locally in width with respect to a line extending along a strip 40, said line being different from the center line of said strip. 40.

[115] Thus, according to another non-limiting embodiment, the marking 4 may comprise linear patterns which do not extend over the entire marking 4, namely which do not extend from a limit of the marking to a another limit.

[116] In an alternative embodiment, the linear pattern extending from one marking limit to another limit exhibits interruptions. In other words, the linear pattern is discontinuous.

[117] In another alternative embodiment, the discontinuity pitch varies continuously in order to adapt to the curvatures of the tire.

[118] In summary, the method of performing the marking comprises:

a first processing of the source image into a target image composed of a plurality of lines, all or part of the lines having in their length one or more variations of width so as to define said source image;

- the selection of one or more linear patterns;

- Performing the marking from said target image, the marking comprising a plurality of linear patterns.

[119] This method makes it possible to obtain gray levels on the marking which are sufficiently visible on the tire so as to bring out said image on the tire. [120] In a non-limiting embodiment, the method further includes a second process in which parameters of the source image are adjusted such that at least five percent of the gray levels of said source image have a value. less than 20 and at least five percent of the gray levels of said source image have a brightness value greater than 80.

[121] This provides pneumatic marking that is closest to the source image.

[122] In another non-limiting embodiment, the method further comprises an adaptation of the resolution of said source image according to the desired resolution of said marking on said tire and a pitch between two linear patterns.

[123] This makes it possible to adapt the source image to the support of the tire. This makes it possible to transpose a marking in a physical space, here on the tire, into a corresponding computer format image.

[124] In another non-limiting embodiment, the marking is performed by laser etching by means of a laser engraving machine on a mold or directly on said tire.

[125] Thus, the disclosed invention has the following advantages in particular:

It increases the quality of the markings perceived on a tire; - It allows for high quality markings using existing industrial techniques. The cost of implementation is therefore low;

It makes it possible to obtain a marking on a tire that makes it possible to recognize the object of the source image;

It allows an observer of the tire to perceive the marking on the tire, whatever the direction and intensity of the light that illuminates the tire, and not only when the light is grazing; It allows to have precise markings on the tire: it is thus possible to obtain an image on a tire with photorealistic rendering;

It makes it possible to obtain a tire marking which has several shades of gray; and It allows to obtain a maximum of contrast thanks to a linear pattern of the "velvet" type.

Claims

1. tire (1) of rubber material comprising a tread (2) and a sidewall (3), said tire (1) comprising on said tread (2) and / or said sidewall (3) a marking ( 4), characterized in that the marking (4) is formed by a plurality of linear patterns integral with the tire, said patterns being parallel to each other and spaced apart by a pitch P less than or equal to 1 mm, each linear pattern having a length L and in that all or part of the linear patterns (41) has one or more variation (s) of width (Lt) in their length L, so as to define the marking.

2. Pneumatic tire (1) according to claim 1, characterized in that the marking is (4) is a representation of a photograph.

3. Pneumatic tire (1) according to one of claims 1 or 2, characterized in that the linear patterns (41) are arranged obliquely in the marking.

4. Tire (1) according to any one of claims 1 to 3, characterized in that a linear pattern (41) is composed of one or more protruding elements (8, 9, 10) and / or of one or more recessed elements (13) with respect to the tread (2) and / or said sidewall (3).

5. Tire (1) according to claim 4, characterized in that all or part of the protruding elements are strands (8) distributed in the linear pattern (41) in a density at least equal to one strand per square millimeter (mm). ² ), each strand having a mean section of between 0.0005 mm ² and 1 mm ² .

Pneumatic tire (1) according to claim 4 or claim 5, characterized in that all or part of the protruding elements are lamellae (9). substantially parallel to each other, the pitch of the slats in the linear pattern (41) being at most equal to 0.5 mm, each slat having an average width of between 0.02 mm and 0.25 mm.

7. A tire (1) according to any one of claims 4 to 6, characterized in that all or part of the protruding elements form parallelepipeds (10) side (C) between 0.05 mm and 0.5 mm , of height (H) between 0.05 mm and 0.5 mm, the distance between two adjacent parallelepipeds in the linear pattern (41) being between 0.05 mm and 0.5 mm.

Pneumatic tire (1) according to one of Claims 4 to 7, characterized in that all or some of the hollow elements (12) form openings (13) on the tread (2) and / or the sidewall. (3) and the linear pattern (41) comprises a plurality of openings (13), these openings being distributed in the linear pattern (41) in a density at least equal to one opening per square millimeter (mm ² ), these openings having equivalent diameters between 0.01 mm and 1.2 mm.