WO2018060586A1

WO2018060586A1 - Tyre with partially textured tread

Info

Publication number: WO2018060586A1
Application number: PCT/FR2017/052584
Authority: WO
Inventors: Olivier Muhlhoff; Julien BESSET; Hélène Carentz; Mostapha EL-OULHANI; Masayoshi Nomura
Original assignee: Compagnie Generale Des Etablissements Michelin
Priority date: 2016-09-29
Filing date: 2017-09-26
Publication date: 2018-04-05
Also published as: FR3056447A1

Abstract

A tyre (1) comprising a tread (8), at least one groove (2), at least first and second wear indicators (3) arranged in the groove (2), the groove (2) comprising a texture (4) that is of the same material as a bottom (10) of said groove (2), said texture (4) being an organised arrangement of a plurality of elements, said texture (4) surrounding the wear indicator (3) and contrasting with the contact surface (7) of the wear indicator, and the groove (2) comprising an area with no texture (5) extending circumferentially between said first wear indicator and said second wear indicator.

Description

TIRE PARTIALLY TEXTURED BEARING TIRE TECHNICAL FIELD OF THE INVENTION

The present invention relates to a tire whose top comprises a tread provided with grooves with textured zones.

STATE OF THE PRIOR ART

In order to maintain the level of safety of a vehicle, it is appropriate to control the tire wear level on a regular basis, and preferably before each long journey. For this, the motorist observes the surface of the tire tread and measures the height of the tread. This measurement is facilitated by an element present on any type of tire: the wear indicator. The wear indicator makes it possible to evaluate, on a basis of a reliable reference, the state of wear of the tires. This indicator is typically arranged in the grooves of the tires. Thus, when the tread patterns are at the same height as the wear indicators, (for example, in Europe, at least 1, 6 millimeters high relative to the groove base), it is advisable to replace the tire (s).

The wear indicator is installed at the bottom of the grooves and is generally in rectangular form. It must be visible not only for the user, but also for third parties, for example in order to make it possible to check the compliance of the wear indicators with the legislation. It is therefore important to have effective and reliable visual cues to locate the wear indicators quickly and easily. In some cases, the wear indicators of certain passenger car tires, particularly the models whose chassis is lowered, are less visible insofar as body elements cover the upper part of the tires. In this situation, the wear indicator becomes less visible. The user can then identify the location of the wear indicator by referring to a marker located in the shoulder zone. Such a marker can be constituted by the well-known symbol "TWI" (meaning in English "Tire Wear Indicator", or in French: indicator of wear indicator), or any other symbol easily recognizable by users. In other cases, the grooves of the tread are completely covered with textures absorbing light, making the location of the wear indicator difficult or sometimes very difficult.

For example, patent application US6866076 discloses a tire intended to reduce the resistance to the flow of a fluid in the grooves. For this purpose, the tire has textures at the bottom of the grooves. The grooves of the tire are covered with small grooves or small ribs having a fixed depth in a range of 0.01 to 0.5 millimeters. Thus, the resistance to the flow of water in the groove is reduced. With this type of arrangement, it is possible to improve the performance of the tire, for example in a humid environment. However, with such an arrangement, the wear indicator, disposed among the grooves, is not very visible. Furthermore, the presence of the grooves near the wear indicators can make it difficult to control the height of the wear indicators. Indeed, the grooves are obstacles that can affect the proper positioning of a measuring tool such as a slider, a micrometer, or caliper, which can cause inaccurate measurements.

To overcome these disadvantages, the invention provides different technical means.

SUMMARY OF THE INVENTION

First, a first object of the invention is to provide a tire arranged to facilitate the identification or location of the wear indicators of the tread.

Another object of the invention is to facilitate the verification of conformity of the wear indicators with the legal requirements. Finally, another object of the invention is to allow to easily measure the height of the level of wear of the tire at different locations in the tread. To do this, the invention provides a tire comprising a tread, the tire comprising at least one groove, at least a first and a second wear indicator disposed in the groove, at least the first witness of wear comprising a contact face intended to come into contact with a roadway when the tire reaches a limit wear level, the groove comprising a texture made of material with a bottom of this groove, said texture being an organized arrangement of a plurality of elements, all or part of the elements of the arrangement being the repetition of the same basic element, such as a strand or a lamella, said texture surrounding the wear indicator and in contrast with the contact face of the wear indicator and the groove comprising a textureless zone extending circumferentially between said first wear indicator and said second wear indicator.

Such an embodiment facilitates the reading of the height H of the wear indicator and / or the measurement of the height of the groove at different circumferential positions. A user or a mechanic can therefore proceed with ease to verify the conformity of the depth of the groove with respect to the height of the tread, and this at different points on the tire, and not only at the level of wear indicators. . Moreover, the textured surfaces of the grooves absorb the light. Conversely, the smoother surfaces of the wear indicators allow better reflection of the light. This creates a contrast between the two surfaces and makes more visible wear indicator (s). The user can thus identify or locate the wear indicators of his tires with greater ease, making tire wear control less tedious. According to an advantageous embodiment, the zone without texture is globally linear.

The width of the zone without texture is advantageously between 3% and 50%, preferably between 8% and 30% and even more preferably between 12% and 20% of the width of the groove.

According to another advantageous embodiment, the zone without texture is discontinuous between the two wear indicators.

Advantageously, the groove is further devoid of texture in a radius of between 1 and 20 mm around the wear indicator and more preferably between 3mm and 8mm around the first wear indicator. Advantageously, the texture has a brightness called first brightness (L ^* 1), the contact surface of the wear indicator has a brightness called second brightness (L ^* 2), the difference in brightness between the first and the second brightness being at least 5 units of brightness (on a scale ranging from 0 to 100). Such a difference in brightness makes it possible to create an easily recognizable contrast effect for a user. This contrast effect may advantageously be used to locate a specific point such as a wear indicator, which is classically difficult to identify on a tread without a contrast effect. The first brightness (L ^* 1) is advantageously between 5 and 18 units, and preferably between 8 and 16 units. The values tend towards black, so as to absorb the incident light well.

The brightness of the contact face (or second brightness) is between 20 and 35 units. The values tend towards the white, so as to reflect the incident light well. According to an advantageous embodiment, the wear indicator comprises at least one side face connecting the contact face of the wear indicator to said bottom, said side face being provided at least partially with said texture. The textured side face helps to improve the visibility of the wear indicator in the groove.

According to an advantageous embodiment, the texture comprises a plurality of strands, said strands being distributed in the texture according to a density of at least one strand per mm ² , each strand having an average section S of between 0.0005 mm ² and 1 mm ² .

According to another embodiment, the texture comprises a plurality of blades parallel to each other, the pitch of the blades in the texture being at most equal to 0.5 mm, each blade 12 having an average width between 0.02. mm and 0.5 mm.

In another embodiment, the textures have a rectangular parallelepipedal section C between 0.05 mm and 0.5 mm, height H.sub.p between 0.05 mm and 0.5 mm.

According to yet another embodiment, the texture is formed by a plurality of cavities, said cavities being in the form of cones, said cavities extending in the depth of the surface and opening on this surface forming circular openings. .

DEFINITIONS

By "tire" is meant all types of elastic bandages subjected to internal pressure or not. By "rubber material" is meant a diene elastomer, that is to say in known manner an elastomer derived from at least in part (that is to say homopolymer or copolymer) of diene monomers. (monomers carrying two carbon-carbon double bonds, conjugated or not). By "tread" of a tire is meant a quantity of rubber material delimited by side 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.

By "sidewall" of a tire means a side surface of the tire disposed between the tread of the tire and a bead of the tire. "Texture" means an organized arrangement of a plurality of elements, all or part of the elements of the arrangement being the repetition of the same basic element, for example, a strand or a lamella.

By "strand" is meant a filiform element whose height is at least equal to 2 times the diameter of a disc of the same surface as the average section of the strand.

By "lamellae" is meant elongate strands having a length at least equal to twice their height.

By "brightness" or "luminance" is meant the parameter that characterizes a surface to reflect more or less light. The luminosity is expressed on a scale from 0 to 100 according to the colorimetric model L ^* a ^* b ^* established by the CIE (International Commission on Illumination) in 1976. The value 100 represents white or total reflection; the value 0, black or total absorption. In this color model a ^* and b ^* are chromaticity coordinates. The color model L ^* a ^* b ^* also 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. DESCRIPTION OF THE FIGURES

All the details of embodiment are given in the description which follows, supplemented by FIGS. 1 to 1 1, presented solely for purposes of non-limiting examples, and in which:

- Figure 1 is a partial view of a tread of a tire of the prior art;

FIGS. 2a and 2b illustrate partial views of examples of tire treads according to the invention;

FIGS. 3a and 3b illustrate partial views of other examples of tire treads according to the invention;

- Figure 4 is a sectional view of a wear indicator with one side a textured area and the other a non-textured area;

FIG. 5 is a cross-sectional view of the area without texture of an example of a non-textured wear indicator inserted within a textured groove;

- Figure 6 shows a portion of the texture of the groove according to a first embodiment according to which the texture has protruding elements in the form of strands;

FIG. 7 shows part of the texture of the groove according to a second exemplary embodiment in which the texture has elements in protuberance in the form of lamellae;

- Figure 8 shows a portion of the texture of the groove, according to a third embodiment in which the texture has parallelepiped shaped protruding elements;

- Figure 9 shows a portion of the texture of the groove, according to a fourth embodiment wherein the texture has protruding elements whose shapes and distances between protruding elements are variable;

- Figure 10 shows a portion of the texture of the groove, according to a fifth embodiment wherein the texture has recessed elements conical in this example;

FIG. 11 represents an enlarged view of a cavity of a hollow element of the texture of FIG. DETAILED DESCRIPTION OF THE INVENTION

Figure 1 is a schematic representation of a portion of a tread 8 of a tire 1 of the prior art. The tread 8 provides a ground contact surface consisting of peaks 9 of sculptures. The tread 10 of the tire 1 form grooves 2, or furrows. The grooves 2 serve as a housing for positioning the wear indicators 3. The grooves 2 can also be arranged in different ways to meet specific functions. In the example illustrated, the grooves 2 are circumferential and provided with textures 4 at the bottom 10 of grooves. Such a coating has many functional and visual advantages. However, it is likely to affect the visibility of the wear indicators 3. Thus, according to the invention, and as shown, the wear indicators 3, in particular the contact faces 7 of the wear indicators, are advantageously devoid of textures, and have a surface producing a contrast of brightness with the adjacent surface of the textured grooves. The contrast effect between the bottom of the grooves and the wear indicators 3 makes them visible, thus facilitating their location. Such a feature is particularly advantageous when the tread 8 is in a context where visibility is restricted.

Figures 2a, 2b, 3a and 3b illustrate tread portions 8 example of tires according to the invention. These embodiments provide at least first and second wear indicators 3 arranged in grooves 2 provided with textures 4. At least one of the textured grooves comprises a zone 5 without texture extending circumferentially between a first wear indicator. and a second wear indicator. In the exemplary embodiments of FIGS. 2a and 2b, this zone devoid of texture is globally linear. The exemplary embodiments of FIGS. 3a and 3b show variants in which the zones without texture make zigzag-shaped paths. In Figure 3a, the zigzags are in the form of "Z" successively aligned. In Figure 3b, the zigzags are sinusoidal. Many other variants are also possible. One of the grooves in Figure 3b also provide a arrangement in which the textureless zone is in the form of dots or pins of the same or different sizes distributed along the groove.

The width of the zone without texture is between 3% and 50%, and more preferably between 8% and 30%, and even more preferably between 12% and 20% of the width of the groove. A preferred method of calculation is to measure the width of the groove at the bottom of this groove.

The non-textured zones 5 are advantageously used in order to make it possible to accurately measure the height H of the wear indicator in a certain and repetitive manner during a step of checking the wear indicator during the manufacturing process of the tire. , and to check the tread wear during the life of the tire (see Figure 5). As illustrated in Figure 4, the non-textured wear indicator 3 is arranged in a groove 2 provided with a texture 4. The absence of texture on the wear indicator 3 makes it possible to create a contrast accentuated with respect to the textured groove 2.

A wear indicator 3 may include textured surfaces, such as a side face 6. Figure 5 illustrates such an embodiment. However, it is preferable that the contact face 7 (or functional part) of the wear indicator is untextured so that the contrast with the texture of the groove 4 is accentuated. The integration of non-textured wear indicators 3 into textured grooves 4 has the effect of accentuating the visibility of the wear indicators 3 by contrasting effects, notably of brightness. The wear indicators 3 are thus better visible.

The previously mentioned contrast effect comes from the fact that the brightness of the zones provided with textures is lower than that of the zones devoid of textures. Various arrangements or configurations of textures 4 make it possible to produce such an effect, as described below, in relation with FIGS. 6 to 11. The device for measuring the appropriate brightness is a spectrophotometer CM 700D brand KON ICA-MINOLTA (trademark). This device is suitable for measuring:

the luminosity L ^* 1, L ^* 2 of the zones of the groove (areas covered by the texture, areas not covered by the texture);

a component a ^* that defines a first shade of color between red and green;

a component b ^* that defines a second shade of color between yellow and blue.

Positioning said apparatus on the part of the tire to be measured and said apparatus gives the values of the three parameters L ^* , a ^* , b ^* relating to the texture. These measurements are made with the "SCI" mode (specular reflection mode included) set at an angle of 10 ° and a light setting of type D65 (setting defined by the International Commission on Illumination, CIE). With this device, we quantify the brightness of the textures of the groove 4 which is then compared to the brightness of the non-textured portions of the wear indicator.

The arrangement promoting the visibility of the wear indicators 3 groove bottom 4 previously described can be advantageously used for any type of tire 1. Figures 6 to 1 1 illustrate examples of textures 4 that can be arranged on the groove 2 according to the invention.

FIG. 6 illustrates an embodiment in which the texture comprises a plurality of strands 1 1. The strands 11 are distributed in the texture according to a density of at least one strand per mm ² , each strand having an average section S of between 0.0005 mm ² and 1 mm ² . It is 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 have a generally conical shape with a decreasing section in the Hb height of these strands. [0044] FIG. 7 illustrates an embodiment in which the texture comprises a plurality of blades 12 parallel to one another, the pitch of the blades 12 in the texture being at most equal to 0.5 mm, each blade 12 having an average width. between 0.02 mm and 0.5 mm. Note that the average width corresponds to the average width I measured at regular intervals in the height Hl of the blade, the height of each blade being between 0.05 and 0.5 mm.

In another variant embodiment, the texture comprises a combination of strands 1 1 and / or and blades 12.

The invention is not limited to the examples described and shown and various modifications can be made without departing from its scope. Thus, according to another non-limiting embodiment, the blades 12 of Figure 7 may be discontinuous. They have a flat part between them. In addition, they may have section differences between them. In addition, the blades may have curvatures or angles, especially in their length. They can also be of variable length.

In the example of FIG. 8, the textures have a parallelepipedic section 13 of side C between 0.05 mm and 0.5 mm, with a height Hp of between 0.05 mm and 0.5 mm. distance Dp between two adjacent cavities in the texture being between 0.05 mm and 0.5 mm. In a variant, the section of the textures may be circular, polygonal (for example hexagonal). With square or polygonal structures, it is possible to more easily organize the elements relative to each other so as to limit the area of the intermediate zones between the elements.

In the variant of Figure 9, the elements 14 have shapes and variable distances between them. This variant makes the details of the texture 4 less visible. Figure 10 illustrates a texture according to another non-limiting embodiment. In this variant, the texture is formed by a plurality of cavities 16. The cavities 16 are here in the form of cones which extend into the depth of the surface and open out onto this surface forming circular openings. The cavities 16 thus have a section which decreases in depth. Note that in this variant, the openings 15 of the cavities 16 do not touch. The openings 15 are separated by intermediate zones 17. In addition, the openings 15 are regularly distributed so that the distance d between each opening 15 is generally similar.

Figure 1 1 is an enlarged view of the texture of Figure 10. All or part of the cavities here has at least one wall 18 which, in a sectional view, forms an angle β between 10 ° and 60 ° relative to a direction Z perpendicular to the texture. The figures and their descriptions made above illustrate the invention rather than limiting it.

The reference signs in the claims are not limiting in nature. The verbs "understand" and "include" do not exclude the presence of elements other than those listed in the claims.

Reference numbers used in Pneumatic figures

Groove

Wear indicator

Texture

Zone without texture

Face of the wear indicator

Contact face of the wear indicator

Tread

Tread tread

Groove bottom

strands

blades

Parallelepipedic section

Protruding elements

overtures

cavities

Intermediate areas

Cavity wall

Claims

1. Tire (1) comprising a tread (8), the tire comprising at least one groove (2), at least a first and a second wear indicators (3) arranged in the groove (2), at least the first wear indicator comprising a contact face (7) intended to come into contact with a road surface when the tire reaches a limit wear level, characterized in that the groove (2) comprises a texture (4) made integrally with a bottom (10) of this groove (2), said texture (4) being an organized arrangement of a plurality of elements, all or part of the elements of the arrangement being the repetition of the same basic element, such as a strand or a strip, said texture (4) surrounding the wear indicator (3) and contrasting with the contact face (7) of the wear indicator and in that the groove (2) comprises a zone without texture (5) extending circumferentially between said first wear indicator and said second wear indicator.

2. Tire according to claim 1, in which the zone without texture (5) is generally linear.

3. Tire according to any one of claims 1 to 2, in which the width of the zone without texture is between 3% and 50% of the width of the groove.

4. Tire according to any one of claims 1 to 3, in which the width of the zone without texture is between 8% and 30% of the width of the groove, and more preferably between 12% and 20% of the width of the groove.

5. Tire according to any one of claims 1 to 4, in which the zone without texture is discontinuous between the first and the second wear indicator.

6. Tire according to any one of claims 1 to 5, in which the texture (4) has a so-called first brightness (L ^* 1), the contact face (7) of the wear indicator has a so-called second brightness brightness (L ^* 2), characterized in that the difference in brightness between the first and second brightness is at least 5 brightness units.

7. Tire (1) according to claim 6, in which the first brightness (L ^* 1) is between 5 and 18 units, preferably between 8 and 16 units.

8. Tire (1) according to any one of claims 1 to 7, in which the brightness of the contact face (7) is between 20 and 35 units.

9. Tire (1) according to any one of claims 1 to 8 in which the wear indicator (3) comprises at least one lateral face (6) connecting the contact face (7) of the wear indicator to said bottom

(10), said side face (6) being provided at least partially with said texture (4).

1 1 . Tire (1) according to any one of claims 1 to 10, in which the groove (4) is further devoid of texture within a radius of between 1 and 20 mm around the first wear indicator and more preferably between 3mm and 8mm around the first wear indicator.

12. Tire (1) according to any one of claims 1 to 1 1, in which the texture (4) comprises a plurality of strands (1 1), said strands (1 1) being distributed in the texture according to a density at less equal to one strand per mm ² , each strand having an average section S of between 0.0005 mm ² and 1 mm ² .

13 Tire (1) according to any one of claims 1 to 12, in which the texture (4) comprises a plurality of blades (12) parallel to each other, the pitch of the blades (12) in the texture (4) being at plus equal to 0.5 mm, each blade 12 having an average width of between 0.02 mm and 0.5 mm.

14. Tire (1) according to any one of claims 1 to 13, in which the textures have a parallelepiped section (13) of side C of between 0.05 mm and 0.5 mm, of height Hp of between 0, 05mm and 0.5mm.

15. Tire (1) according to any one of claims 1 to 14, wherein the texture (4) is formed by a plurality of cavities (16), said cavities (16) being in the shape of cones, said cavities are extending into the depth of the surface and opening onto this surface by forming circular openings (15).