WO2018122484A1

WO2018122484A1 - Tyre with sidewall bars arranged with a variable pitch

Info

Publication number: WO2018122484A1
Application number: PCT/FR2017/053464
Authority: WO
Inventors: Olivier Muhlhoff; Yann Chaylard; Hervé FERIGO; Frédéric VALLENCE; Mathieu Vandaele
Original assignee: Compagnie Generale Des Etablissements Michelin
Priority date: 2016-12-27
Filing date: 2017-12-08
Publication date: 2018-07-05
Also published as: FR3061079A1

Abstract

A pneumatic tyre (1) made of a rubber material comprises a tread (4), a first sidewall (6a) and a second sidewall (6b) adjoining the tread (4) with an outer sidewall profile, the sidewalls (6a, 6b) comprising a plurality of sipes (9) separated by rubber bars (8), the bars and the sipes being located next to each other around the circumference of the tyre (1), the bars (8) being arranged around the circumference of the tyre (1) in at least two series of bars having different pitches (P1, P2).

Description

Pneumatic tire with side bars with variable pitch arrangement

FIELD OF THE INVENTION

The present invention relates to a tire for a motor vehicle having a plurality of rubber bars on at least one sidewall. STATE OF THE ART

It is known from WO2014 / 207093 to provide at least one sidewall of a tire with a plurality of rubber bars. The strips of rubber are made by molding during a step of baking the tire. They are thus obtained in the same way as the sculptures on the tread of the tire. These rubber strips make it possible to improve the strength of the sidewall with respect to lateral shocks, without fundamentally changing the dimensions of this sidewall. The rubber bars on the sidewall of the tire create an alternation of depressions and bumps on the sidewall of the tire. During a rolling, this alternation of hollows and bumps can cause an excitation of the tire structure. At certain speeds of travel, this excitation generates vibrations and therefore noise to which is sensitive the driver of the vehicle or a person external to the vehicle.

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

SUMMARY OF THE INVENTION To do this, the invention provides a tire of rubber material comprising a tread, a first sidewall and a second sidewall extending said tread according to an outer sidewall profile, the sidewalls having a plurality of hollow areas. separated by strips of rubber material, the bars and the recesses being arranged one after the other in the circumference of the tire, said webs not exceeding the outer sidewall profile, in which the webs are arranged in the circumference of the tire in at least two sets of different step 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 pitch P1 and P2. The step values are measured between two median lines of consecutive bars, at identical radial positions. There are at least two different distances.

[0007] Advantageously, the difference between the pitch values P1 and P2 is at least 5%, and preferably greater than 20%, and more preferably between 25 and 50%.

The variation of pitch between the bars of the series of bars allows to spread the vibration spectrum of the tire structure over a wider frequency range. By modifying the pitch, and therefore the distance between the adjacent bars, the interference of the eigenfrequencies 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 involves a variation of these two parameters simultaneously, preferably by ensuring that the rate of notch volume (TEV) is constant. This characteristic makes it possible to make uniform tires that do not generate a variation in radial stiffness during taxiing.

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

This embodiment allows to hide more vibration.

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

By avoiding identical frequencies on both sides, vibratory modes are even better controlled. Advantageously, the strips have a height of between 3 mm and 10 mm, more preferably between 4 mm and 8 mm.

According to yet another advantageous embodiment, less 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 flank to the other. This adds another characteristic contributing to the reduction of vibration.

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 of a length L _A between ½ (L-60mm) and ½ (L-10mm), where L is the nominal flange size, and

said point E being disposed, optionally, in a radius included in:

o R ₂ <E <(0.75 Ri + 0.25R ₂ ), where R2 is the radius of the top of the rim hook and Ri is the radius of the nominal rim size, or

o 0.95Ri <E <(0.75R _A + 0.25 Ri), Ri being the radius of the nominal coil size, and R _A being the radius of point A. [0022] Also advantageously, all or part of bars are interrupted by a circumferential groove and said groove extends between a zone of maximum width of the sidewall and the tread.

The presence of the circumferential groove allows to remove the material and thus lighten the tire, it also allows to mechanically decouple the tire top area of the sidewall and thus reduces vibration.

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

The bars on the sides 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 in 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 solely by way of illustration, and in which:

- Figure 1A shows, schematically, 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 flanks;

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

- Figure 3 shows, schematically, an enlarged portion of a side including bars;

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

- Figures 5A and 5B show, in a variant, a portion of a radially outer portion 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 sidewall of the tire.

DETAILED DESCRIPTION OF THE INVENTION

DEFINITIONS [0028] Hereinafter referred to as:

- "longitudinal or circumferential direction": rolling direction of the tire, - "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 inner to' means closer to the axis of rotation, - 'radially outside' means more distant 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" means a plane which contains the axis of rotation of the tire.

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

- "Pneumatic" means all types of elastic bandages subjected to internal pressure or not.

- "Sidewall of a tire" means a side portion of the tire disposed between the tread of the tire and a bead of the tire.

- "External profile" means the virtual outer envelope connecting the outermost points of the bars of the two sides and in which the bars are included. - "Average height of the bars" means the average height of all the bars of a sidewall.

"Middle line of ME bar" means a longitudinal virtual line passing through a bar passing substantially through its center, so that the bar is subdivided into two substantially equal parts. "Pitch" means a distance separating two consecutive bars, this distance being measured between two median lines of consecutive bars, at substantially identical radial positions.

- By "not median" means the pitch measured substantially halfway up the bars.

"Series of bars" means an assembly comprising at least two bars having identical pitch characteristics.

The term "partially interrupts" means that the radially upper end of a bar partially cuts the circumferential groove.

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

- The "groove" is an area of a given width located around the 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 disposed plumb with each other in a radial direction, with possibly symmetry, and uniformly.

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 flange size L is defined by the flange size of a tire mounted on the rim and inflated; the flange size being, according to the invention, the distance between the outside of the flanks of an inflated tire, by incorporating the surface relief of the flanks. Ri corresponds to the radius of the point on the outer surface of the flank 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 general-purpose passenger car tire 1 comprises a radially inner carcass reinforcement 2 to a general reference belt reinforcement 3, said belt reinforcement 3 being radially interior to a strip of reinforcement. bearing 4 itself connected to two beads 5 via two sides 6a and 6b. The beads 5 are intended to come into contact with a rim 7 (partially shown) having rim hook heels 7b. Each bead comprises at least one circumferential reinforcing element 7a. The flanks comprise, on their surface, a series of strips 8 regularly alternated with recesses 9 (shown in Figures 2A, 2B and 2C). In Figure 1A can be seen 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 in the center of the volume of each bar, and which undergoes neither shortening nor elongation when it is subjected to compression and / or depression.

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

The interval II corresponds to 0.95Ri <E <(0.75R _A + 0.25 Ri), Ri being the radius of the nominal coil size, and R _A being the radius of the point A. According to an exemplary embodiment, the point E is disposed at a radius of 232 mm for a reference tire 205/55 R 16 mounted on a rim 6.5 J 16 for which RA is equal to 298 mm, R ₂ is equal to 220 mm and Ri is 261 mm.

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

Point A is disposed at the intersection of the radially outer surface of the tread and the sidewall, and an axis ZZ 'distant equatorial plane AA' of length L _A between ½ (L -60 mm) and ½ (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 in the rubber flanks, but are obtained by molding during the baking step. They are obtained in a manner similar to that of the sculptures made on the tread. FIG. 1B shows that the presence of the bars 8 of height H further makes it possible to optimize the thickness of the sidewall: the thickness "D" of the outside edge (in addition the zone situated between the bars) is greater at 0.1 mm and preferably between 0.2 and 2 mm, 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 strength of the reinforcements of the carcass ply and therefore the robustness of the tire in the face of the shocks and the various aggressions to which the sidewalls are likely to be subjected, without counting the other advantages (previously described) obtained by the barrettes 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 embodiment 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 sidewall 6a differs by at least 10% and at most 50% and more preferably at least 20% and at most 35% of the height of the bars 8 of the second sidewall 6b.

FIG. 1C illustrates an advantageous embodiment in which the height H of the bars varies along the circumference of a sidewall. The amplitude of the variations can then be comparable to the previously indicated amplitudes when the height varies from one flank to the other. It is thus possible to find bars of different heights alternating one by one, as shown in the example of FIG. 1C, or according to any other type of distribution of the bars of different heights. In addition, there may be more than two heights H of bars.

The height H is preferably the average height, as previously defined. In order to carry out the height value measurements, a reference measurement point is preferably used for all the bars, so that measurements are made uniformly on each of the bars. The values obtained for all the bars are then averaged. Figure 2C illustrates an example for determining a reference point, using the intersection of the mid-height (or neutral) ME-ME and mid-height lines of the MHB-MHB arrays.

Figure 2A shows an alternation of bars 8 and recesses 9, shown enlarged in Figures 3 and 4.

Figure 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 RR axis. According to a preferred embodiment of the invention, the angle β of inclination of the flank webs ¹ is different from the angle tilting β of the bars of the second flank. Figure 6 schematically illustrates this embodiment. On the left of the figure, a strip 8 of a first sidewall 6a is arranged at an angle β. The right portion of the figure shows in dotted lines that we could see in transparency on the opposite side 6b. A bar illustrated in dotted line 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 embodiment in which the bars 8 are organized in the circumference of the tire 1 in at least two series of pitch bars P1 and P2 that are different. The difference between the pitch values 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 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 volume notch rate (VTE) is constant. This characteristic makes it possible to make uniform tires that do not generate a variation in radial stiffness during taxiing. According to another variant, the series of bars 8 comprise at least three different values of pitch. In another variant, 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 made between the middle (or neutral) ME-ME lines of two adjacent bars. The median pitch, that is to say the pitch measured halfway up the bars, is preferably used. The position of mid-height of the bars is illustrated in Figure 2C, by the line MHB-MHB. FIG. 4 illustrates an example of the profile of the bars. In this example, the draft angle α is about 8 °. Such a clearance angle value allows a release of the tire after firing without deterioration of the final structure.

According to this embodiment, the strips have a ratio [sum of the widths of each strip in the circumferential direction over a radius Ri] / 2nR equal to 30%, at mid-height and have no angle with respect to the plane. radial.

Figure 5A shows a three-dimensional representation of the radially outer portion 8a of the bars 8 and its enlargement in Figure 5B of Figure 5A. In these Figures 5A and 5B, the portion 8a of each bar 8 and 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 10 mm, and a radial height "h" along the axis ZZ' of between 3 and 8 mm.

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

Reference numbers used in Pneumatic figures

Carcass reinforcement

Belt reinforcement

Tread

a Axially outermost end of the tread

First Flank

b Second flank

a circumferential reinforcement element

b Rim hook top

barrette

a Bar end

Hollow

Circumferential groove

Claims

1. 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 material webs (8), the webs and the recesses being arranged one after the other in the circumference of the tire (1), said webs (8) not exceeding the outer sidewall profile, characterized in that the webs (8) are arranged in the circumference of the tire (1) in at least two different sets of pitch bars (P1, P2).

2. A tire according to claim 1, characterized in that the difference between the pitch values 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 step 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 pitch.

6. A tire according to any one of claims 1 to 5, characterized in that each side (6a, 6b) of the tire comprises a series of bars, the pitch (P1, P2) 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 of 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 side 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 side to the other.

1 1. Tire according to any one of claims 1 to 10, characterized in that the webs (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 the sidewall, and a radial axis ZZ 'distant from the equatorial plane with a length L _A of between ½ (L-60mm) and ½ (L-10mm), where L is the nominal flange size, and

said point E being disposed, optionally, in a radius included 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 the point A.

12. A tire according to any one of claims 1 to 1 1, characterized in that all or part of the webs (8) is interrupted by a circumferential groove (10) and in that said groove (10) extends between a zone of maximum width of the sidewall and the tread (4).

13. Mounted assembly comprising a rim and a tire as defined in one of claims 1 to 12.