FR3061079A1 - PNEUMATIC COMPRISING FLANK BARS WITH A VARIABLE NO-ARRANGEMENT - Google Patents

Abstract

Tire (1) made of rubber material comprising a tread (4), a first sidewall (6a) and a second sidewall (6b) extending said tread (4) according to an external sidewall profile, the sidewalls (6a, 6b ) having a plurality of hollow areas (9) separated by rubber-like bars (8), the bars and the recesses being arranged one after the other in the circumference of the tire (1), the bars (8) being arranged in the circumference of the tire (1) in at least two sets of different pitch bars (P1, P2).

Description

(© Agent (s): TWENANS.

© TIRE COMPRISING SIDE BARS WITH A VARIABLE STEP ARRANGEMENT.

FR 3,061,079 - A1 (57) Tire (1) made of rubber material comprising a tread (4), a first sidewall (6a) and a second sidewall (6b) extending said tread (4) according to an external profile sidewall, the sidewalls (6a, 6b) comprising a plurality of recess zones (9) separated by bars (8) of rubber material, the bars and the recesses being arranged one after the other in the circumference of the tire (1), the bars (8) being organized in the circumference of the tire (1) in at least two series of different pitch bars (P1, P2).

Tire comprising sidewall bars with a variable pitch arrangement

FIELD OF THE INVENTION The present invention relates to a tire for a motor vehicle comprising a plurality of rubber strips on at least one sidewall.

STATE OF THE ART It is known from document WO2014 / 207093 to provide at least one sidewall of a tire with a plurality of strips of rubber. The rubber strips are produced by molding during a tire curing step. They are thus obtained in the same way as the tread patterns on the tire tread. These rubber strips make it possible to improve the robustness of the sidewall against side impacts, without fundamentally changing the dimensions of this sidewall.

The rubber strips on the sidewall of the tire create an alternation of hollows and bumps on the sidewall of the tire. During a rolling, this alternation of recesses and bumps can cause an excitation of the structure of the tire. At certain driving speeds, this excitation generates vibrations and therefore noise to which the driver of the vehicle or a person external to this vehicle is sensitive.

There is therefore a need to provide a tire with reinforced sidewalls having high mechanical strength while limiting the noise pollution generated by this tire during driving.

STATEMENT OF THE INVENTION To do this, the invention provides a tire made of rubber material comprising a tread, a first sidewall and a second sidewall extending said tread according to an external sidewall profile, the sidewalls comprising a plurality of recess areas separated by bars of rubber material, the bars and the recesses being arranged one after the other in the circumference of the tire, said bars not exceeding the external sidewall profile, in which the bars are organized in the circumference of the tire in at least two different series of pitch bars (P1, P2).

The distance between two adjacent bars is not constant in the circumference of the tire since there are at least two different values of steps P1 and P2. The pitch values are measured between two median lines of consecutive bars, at identical radial positions. There are at least two different distances.

Advantageously, the difference between the values of steps P1 and P2 is at least 5%, and preferably greater than 20%, and more preferably between 25 and 50%.

The variation in pitch between the bars of the series of bars makes it possible to spread the vibration spectrum of the structure of the tire over a wider frequency range. By modifying the pitch, and therefore the distance between the adjacent bars, the interference of the natural frequencies is improved and the perception of the noise by the occupants of the vehicle is reduced.

According to an advantageous embodiment, the difference between the pitch values P1 and P2 results from a difference in width of the bars.

According to another advantageous embodiment, the difference between the pitch values P1 and P2 results from a difference in width between the bars.

Yet another variant implies a variation of these two parameters simultaneously, preferably by ensuring that the rate of volume notching (VTE) is constant. This characteristic makes it possible to make uniform tires, not generating a variation in radial stiffness during driving.

According to an alternative embodiment, the series of bars include at least three different pitch values.

This embodiment allows to hide more vibrations.

According to yet another advantageous variant, each sidewall of the tire comprises a series of bars, the pitch (P1, P2) of the series of bars of each sidewall being different.

By avoiding identical frequencies on the two sides, the vibrational modes are even better controlled.

Advantageously, the bars have a height of between 3 mm and 10 mm, more preferably between 4 mm and 8 mm.

According to another advantageous embodiment, at least two bars of the same side have a different height.

According to another embodiment, the bars have an inclination relative to a radial direction (Z).

According to an advantageous variant, the value of this inclination of the bars is different from one side to the other.

Another characteristic thus contributing to the reduction of vibrations is thus added.

Advantageously, the bars are arranged between a point A and a point E, said point A being disposed at the intersection of the radially outer surface of the tread and the sidewall, and a radial axis ZZ 'distant from the equatorial plane with a length L _A between% (L-60mm) and% (L-10mm), L being the nominal flange size, and said point E being arranged, as desired, within a radius included in: o R ₂ <E <(0.75 Ri + 0.25R ₂ ), R2 being the radius of the top of the rim hook and Ri being the radius of the nominal flange size, or in o 0.95Ri <E <(0 , 75R _a + 0.25 Ri), Ri being the radius of the nominal flange size, and R _A being the radius of point A.

Also advantageously, all or part of the bars is interrupted by a circumferential groove and said groove extends between an area of maximum width of the sidewall and the tread.

The presence of the circumferential groove makes it possible to remove material and thus to lighten the tire, it also makes it possible to mechanically decouple the crown area of the tire from the sidewall area and thus makes it possible to reduce the vibrations.

The bars may be present over the entire circumferential length of the sidewall of the tire.

The bars present on the flanks are made of a material preferably identical to that of the flanks.

The invention also provides a mounted assembly comprising a rim and a tire as defined according to one of the preceding claims.

DESCRIPTION OF THE FIGURES The invention will now be described with the aid of the examples and drawings which follow and which are given by way of illustration only, and in which:

- Figure 1A schematically shows a section in a radial plane of a tire mounted on a rim;

- Figures 1B and 1C show, schematically, sections along the sidewalls of a tire in the circumferential direction to highlight examples of profiles of the sidewall bars;

- Figures 2A, 2B and 2C show, schematically and in three dimensions, a portion of a sidewall and the corresponding tread of examples of tires;

- Figure 3 shows, schematically, an enlarged portion of a sidewall comprising bars;

- Figure 4 shows a sectional view of two adjacent bars, along the axis AA of Figure 3;

- Figures 5A and 5B show, alternatively, a portion of a radially outer part of a sidewall and the corresponding tread in three dimensions;

- Figure 6 is a schematic representation of a tire section showing two angular positions of bars in opposition on each side of the tire.

DETAILED DESCRIPTION OF THE INVENTION

DEFINITIONS The following are denoted by:

- "longitudinal or circumferential direction": tire rolling direction,

- "radial direction": direction intersecting the axis of rotation of the tire and perpendicular to it,

- "axial direction": direction parallel to the axis of rotation of the tire,

- "radially inside": means closer to the axis of rotation,

- "radially outside": means further from the axis of rotation,

- "equatorial plane or median plane": plane perpendicular to the axis of rotation of the tire and which divides the tire into two substantially equal halves,

- "transverse direction of the tire": direction parallel to the axis of rotation,

- "radial or meridian plane": a plane which contains the axis of rotation of the tire.

- By “rubber material” is meant a diene elastomer, that is to say in known manner an elastomer derived at least in part (that is to say homopolymer or a copolymer) from diene monomers (monomers carrying two carbon-carbon double bonds, conjugated or not).

- By "pneumatic" is meant all types of elastic bandages subjected to internal pressure or not.

- “Sidewall of a tire” means a lateral part of the tire disposed between the tread of the tire and a bead of this tire.

- By "external profile" is meant the virtual external envelope connecting the outermost points of the bars of the two sides and in which the bars are included.

- By "average height of the bars", we mean the average height of all the bars of a sidewall.

- By "center line of bar ME" means a virtual longitudinal line passing through a bar passing substantially through its center, so that the bar is subdivided into two substantially equal parts.

- By "pitch" is meant a distance separating two consecutive bars, this distance being measured between two median lines of consecutive bars, at substantially identical radial positions.

- By "median pitch" means the pitch measured substantially at mid-height of the bars.

- By "series of bars" means an assembly comprising at least two bars having characteristics of identical pitch.

- By the terms "partially interrupts", it is meant that the radially upper end of a bar partially cuts the circumferential groove.

- By the terms "completely interrupts", it is meant that the radially upper end of a bar joins the axially outer end of the tread which is closest to it.

- The "groove" is an area of a given width located around point A, and having a longitudinal void rate greater than 70%.

- By the term "regular", it is defined that the bars arranged between the points A-E are arranged plumb with one another in a radial direction, possibly with symmetry, and in a uniform manner.

- By the term "irregular", it is defined that the bars arranged between the points A-E are arranged in an offset manner in two parallel radial directions without symmetry and in a non-uniform manner.

- The radius R _A is a function of the length L _A , itself a function of the length L.

- The nominal tire size L is defined by the tire size of a tire mounted on a rim and inflated; the flange size being, according to the invention, the distance between the outside of the sidewalls of an inflated tire, incorporating the surface relief of the sidewalls. Ri corresponds to the radius of the point located on the outer surface of the side furthest from the median plane.

- REQ is the radius at the widest point of the tire (width = L): R _A > REQ.

DESCRIPTION OF THE FIGURES As shown in FIG. 1A, the tire for general reference passenger vehicle 1 comprises a carcass reinforcement 2 radially internal to a general reference belt reinforcement 3, said belt reinforcement 3 being radially internal. to a tread 4 itself connected to two beads 5 by means of two sides 6a and 6b. The beads 5 are intended to come into contact with a rim 7 (partially shown) having rim hook tops 7b. Each bead comprises at least one circumferential reinforcement element 7a. The sides have, on their surface, a series of bars 8 regularly alternated with recesses 9 (shown in FIGS. 2A, 2B and 2C).

In Figure 1A we can see a bar 8, in section, having a continuous neutral fiber. It is recalled here that a neutral fiber is called a neutral axis which passes substantially through the center of the volume of each bar, and which does not undergo any shortening or elongation when it is subjected to compression and / or depression.

As shown in Figure 1A, the bars 8 are preferably arranged on the surface of the sidewall, over a length of continuous neutral fiber which extends from a point A to a point E. The point E can be arranged at two intervals.

The interval I corresponds to R ₂ <E <(0.75 Ri + 0.25R ₂ ), R2 being the radius of the top of the rim hook and Ri being the radius of the nominal flange size.

The interval II corresponds to 0.95Ri <E <(0.75R _A + 0.25 Ri), Ri being the radius of the nominal flange size, and R _A being the radius of the point A.

According to an exemplary embodiment, the point E is arranged at a radius of 232 mm for a reference tire 205/55 R 16 mounted on rim 6.5 J 16 for which R _A is equal to 298mm, R ₂ is equal to 220mm and Ri is equal to 261mm.

The definition according to the invention of the flange size is adaptable to any type of casing combined with any type of rim.

The point A is arranged at the intersection of the radially outer surface of the tread and the sidewall, and of an axis ZZ 'distant from the equatorial plane AA' with a length L _A of between ¹ Z ( L-60 mm) and ¹ Z (L-10 mm), L being the nominal flange size. For a reference tire 205/55 R 16, R _a is equal to 298mm.

The bars are not rubber elements inserted or added to the rubber of the sidewalls, but are obtained by molding during the baking step. They are obtained in a similar way to that of the sculptures produced on the tread.

FIG. 1B shows that the presence of bars 8 of height H furthermore makes it possible to optimize the thickness of the flank: the thickness "D" of the external flank (in addition the zone situated between the bars) is greater than 0.1 mm and preferably between 0.2 and 2mm, and even more preferably between 0.3 and 1.5 mm. It should be noted that the value of D is independent of the diameter of the cables of the carcass reinforcement. These characteristics provide an increase in the resistance of the reinforcements of the carcass ply and therefore in the robustness of the tire against shocks and various attacks to which the sidewalls are liable to be subjected, without taking into account the other advantages (previously described) obtained by bars themselves.

The bars 8 have a height H of between 3 mm and 10 mm, and more preferably between 4 mm and 8 mm. One of the embodiments of the invention provides that the height H of the bars of the first sidewall 6a differs from the height H of the bars of the second sidewall 6b. The height of the bars 8 of the first side 6a differs by at least 10% and at most 50% and more preferably by at least 20% and at most 35% of the height of the bars 8 of the second side 6b.

Figure 1C illustrates an advantageous embodiment in which the height H of the bars varies along the circumference of a flank. The amplitude of the variations can then be compared to the amplitudes previously indicated when the height varies from one side to the other. We can thus find bars of different heights alternately one by one, as illustrated in the example of Figure 1C, or according to any other type of distribution of bars of different heights. In addition, there may be more than two heights H of bars.

The height H is advantageously the average height, as previously defined. To make the height value measurements, a reference measurement point is preferably used for all of the bars, so as to make the measurements uniformly on each of the bars. We then average the values obtained for all the bars. FIG. 2C illustrates an example making it possible to determine a reference point, using the intersection of the mid-lines (or of neutral fiber) ME-ME and of mid-height of the bars MHB-MHB.

FIG. 2A represents an alternation of bars 8 and of recesses 9, shown in enlarged form in FIGS. 3 and 4.

2B shows a variant of Figure 2A where the bars are arranged at an angle β relative to the radial direction, shown in the figure by the axis RR. According to a preferred embodiment of the invention, the inclination angle β of the webs ¹ side is different from the inclination angle β of the webs of the second flank. FIG. 6 schematically illustrates this embodiment. We observe on the left of the figure, a bar 8 of a first flank 6a arranged at an angle β. The right portion of the figure shows in dotted lines what we could see in transparency on the opposite flank 6b. A bar illustrated in dotted lines is thus inclined at a substantially opposite angle β '.

Furthermore, in an alternative embodiment, at least two bars 8 of the same side have a different radial orientation. The angle β is advantageously between 10 ° and 50 °, and preferably between 20 ° and 30 °.

FIG. 2C illustrates a preferred mode in which the bars 8 are organized in the circumference of the tire 1 in at least two series of bars of different pitch P1 and P2. The difference between the values of step P1 and P2 is at least 5%, and preferably greater than 20%, and more preferably between 25% and 50%. This difference preferably results from a difference in width of the bars, or from a difference in width between the bars. However, one of the preferred solutions involves a variation of these two parameters simultaneously, preferably by ensuring that the rate of volume notching (VTE) is constant. This characteristic makes it possible to make uniform tires, not generating a variation in radial stiffness during driving. According to another variant, the series of bars 8 comprise at least three different values of step. Still alternatively, each sidewall 6a and 6b of the tire comprises a series of bars, the pitch P1 and P2 of the series of bars of each sidewall being different. The measurements of the pitch values are preferably carried out between the mid-lines (or of neutral fiber) ME-ME of two adjacent bars. It is preferable to use the median pitch, that is to say the pitch measured at mid-height of the bars. The half-height position of the bars is illustrated in FIG. 2C, by the line MHB-MHB.

FIG. 4 illustrates an example of a profile of the bars. In this example, the draft angle a is approximately 8 °. Such a clearance angle value allows the tire to be demolded after curing without damaging the final structure.

According to this embodiment, the bars have a ratio [sum of the widths of each bar in the circumferential direction over a radius Ri] / 2mR equal to 30%, halfway up and have no angle relative to the plane radial.

Figure 5A shows a three-dimensional representation of the radially outer part 8a of the bars 8 and its enlargement in Figure 5B of Figure 5A. In these FIGS. 5A and 5B, the part 8a of each bar 8 as well as the recesses 9 are adjacent to a groove 10 disposed, circumferentially, on the surface of the tread 4 at its axially outermost end 4a. The groove 10 is not interrupted in its length. According to this particular embodiment, the groove 10 has an axial width "I" along the axis YY "which can be between 2 and 10mm, and a radial height" h "along the axis ZZ" between 3 and 8mm.

The tire according to the invention is obtained after baking and molding in a baking mold in a conventional manner.

Reference numbers used in the figures

Pneumatic

Carcass reinforcement

Belt reinforcement

Tread

Axially outermost end of the tread

Beads

First Flank

Second flank

Circumferential reinforcement element

Rim hook top

Barrette

Bar end

Hollow

Circumferential groove

Claims (13)

1. A tire (1) made of rubber material comprising a tread (4), a first sidewall (6a) and a second sidewall (6b) extending said tread (4) according to an external sidewall profile, the sidewalls (6a , 6b) comprising a plurality of recess zones (9) separated by bars (8) of rubber material, the bars and the recesses being arranged one after the other in the circumference of the tire (1), said bars ( 8) not exceeding the external sidewall profile, characterized in that the bars (8) are organized in the circumference of the tire (1) in at least two different series of pitch bars (P1, P2). 2. A tire according to claim 1, characterized in that the difference between the values of pitch P1 and P2 is at least 5%, and preferably greater than 20%, and more preferably between 25 and 50%. 3. A tire according to one of claims 1 or 2, characterized in that the difference between the pitch values P1 and P2 results from a difference in width of the bars. 4. A tire according to any one of claims 1 to 3, characterized in that the difference between the pitch values P1 and P2 results from a difference in width between the bars. 5. A tire according to any one of claims 1 to 4, characterized in that the series of bars (8) comprise at least three different values of step. 6. A tire according to any one of claims 1 to 5, characterized in that each sidewall (6a, 6b) of the tire comprises a series of bars, the pitch (P1, P2) of the series of bars of each sidewall being different. 7. A tire according to any one of claims 1 to 6, characterized in that said bars (8) have a height between 3 mm and 10 mm, and more preferably between 4 mm and 8 mm. 8. A tire according to any one of claims 1 to 7, characterized in that at least two bars (8) of the same sidewall have a different height. 9. A tire according to any one of claims 1 to 8, characterized in that the bars (8) have an inclination relative to a radial direction (Z). 10. A tire according to claim 9, characterized in that the value of the inclination of the bars (8) is different from one sidewall to the other. 11. A tire according to any one of claims 1 to 10, characterized in that the bars (8) are arranged between a point A and a point E, said point A being disposed at the intersection of the radially outer surface of the tread and sidewall, and a radial axis ZZ 'distant from the equatorial plane with a length L _A of between% (L-60mm) and% (L-10mm), L being the nominal flange size, and said point E being arranged, as desired, within a radius included in: o R ₂ <E <(0.75 Ri + 0.25R ₂ ), R2 being the radius of the top of the rim hook and Ri being the radius of the size nominal rod, or in o 0.95Ri <E <(0.75R _a + 0.25 Ri), Ri being the radius of the nominal rod size, and R _A being the radius of point A. 12. A tire according to any one of claims 1 to 11, characterized in that all or part of the bars (8) is interrupted by a circumferential groove (10) and in that said groove (10) extends between an area maximum width of the sidewall and the tread (4). 13. Mounted assembly comprising a rim and a tire as defined according to one of claims 1 to 12. 1/3