WO2024003283A1

WO2024003283A1 - A tire

Info

Publication number: WO2024003283A1
Application number: PCT/EP2023/067879
Authority: WO
Inventors: Viviane BOMBLAIN; José Merino Lopez; Elise ROULOT
Original assignee: Compagnie Generale Des Etablissements Michelin
Priority date: 2022-06-30
Filing date: 2023-06-29
Publication date: 2024-01-04
Also published as: FR3137328A1

Abstract

Present invention provides a tire comprising two beads each comprising at least one annular reinforcing structure, at least one carcass reinforcement being anchored in the two beads so as to form in each bead a main portion and a wrapped-around portion, a maximum thickness Tb of the bead filler radially below a turn-up end being greater than a thickness Te of the bead filler at the turn-up end, a maximum thickness Ta of the bead filler radially above the turn-up end measured perpendicular to the main portion is greater than 50% of the maximum thickness Tb, and a tan δ at 23 ˚C of a rubber composition in a region axially outside of the wrapped-around portion is lower than that of the rubber composition constituting the bead filler.

Description

A tire

[001] The present invention relates to a tire. The invention relates in particular to a tire design of the lower sidewall and bead area to improve manufacturing efficiency while maintaining rolling resistance, handling and endurance performance.

[002] The continued interest by the governing bodies of most countries in saving the amount of fuel consumed by vehicles has resulted in a need to reduce vehicle mass. This is true for all components of the vehicle, including the tires. However, vehicles are going faster, supporting heavier loads and cornering at higher speeds than ever before. As the need to reduce tire mass is stronger, the need to support the same or higher loads with the same size tire remains. Another important need exists to reduce the rolling resistance of tires. Rolling resistance relates directly to fuel consumption and, generally speaking, rolling resistance decreases as tire mass decreases. The problem is that a reduction in tire mass is known to generally yield a reduction in the ability of the tire to support loads.

[003] A part of the tire that has increased in mass over the years is the tire beads. The beads react the loads from the tire's contact with a ground surface to the rim of the vehicle. The need of modern vehicles, due to their power and maneuverability, to require higher loads to be reacted by the tire is known in the industry. Increased bead mass is a result of adding additional components and/or making the classical components larger.

[004] EP1144207 discloses a tire with radial body ply reinforcement, anchored in each bead B at an anchoring bead core to form a turn-up, axially on the outside of said turn-up of the body ply reinforcement is arranged a section of vulcanized rubber mixture whereof the secant modulus of elasticity in tension measured for a relative elongation of 10 % is much higher than similar moduli of the other mixtures which constitute the bead B, the main part of said body ply reinforcement between its point of tangency T at the anchoring bead core and a point A located at a radial distance HA from the base D of the bead cores, ranging between 35 % and 65 % of the radial distance HE separating the points of maximum axial width of said body ply reinforcement from said base D, with a substantially rectilinear meridian profile.

[005] JP2010285105 discloses a tire provided in a region of a lower sidewall with the rim protector with a substantially trapezoidal cross section having a top portion projecting most outwardly in the tire axial direction. The inside of the rim protector is equipped with a filling rubber with a substantially crescent shaped cross section, made of a rubber harder than a side wall rubber, and extended radially inward and outward adjacently to the outer surface of a ply folded-back portion. The protector thickness Ta from the middle point on the outer surface of the top portion to the ply folded-back portion is 13.0 mm or more. The percentage of the thickness ta of the filled rubber of this protector thickness Ta is 40-50% of the protector thickness Ta. The radial height hi of the radial outer end of the filling rubber is 50-60% of the height HO of the tire cross section. The radial distance Lv1 of the overlap V1 between the radial inner end of the filled rubber and the radial outer end of a bead apex rubber is 10 mm or more. LIS2012/0160391 discloses a pneumatic tire comprising a carcass has one or more cord reinforced plies and a pair of bead portions, each bead portion comprises at least one annular bead core and at least one apex which extends radially outward of the bead core, the apex may be formed of at least two zones, the material in a first zone of the at least two zones is different from the material in a second zone of the at least two zones, and wherein the first zone extends from a radially inner base of the apex to or towards a radially outer tip of the apex and the second zone is located adjacent a ply. Alternatively, the tire may comprise a first and second apex, the first apex is at least essentially triangular shaped and has a base which extends radially outward of the bead core, wherein the second apex is at least partially located between the first apex and at least one carcass ply turnup end, and the material of the first apex is different from the material of the second apex. EP3202594 discloses a tire, sidewalls each include an outer layer, and an inner layer disposed inward of the outer layer in the axial direction, the inner side end, in the radial direction, of the inner layer extends to a region between a bead and a chafer, when Po represents a contact point, on an outer surface of the tire, at which the outer layer and the chafer contact with each other, an inner side end, in the radial direction, of the outer layer is equal to the contact point Po, in the radial direction, an outer side end of the chafer is disposed outward of the contact point Po, in the radial direction, an inner side end of the inner layer is disposed inward of the contact point Po.

[006] However with the solutions disclosed in these documents, manufacturing efficiency of a tire would be degraded due to increased number of semi-finished product. Thus there is a desire to improve manufacturing efficiency of a tire by reducing number of semifinished product without degrading rolling resistance, handling and endurance performance of such the tire.

[007] Therefore, there is a need for a tire which provides improvement on manufacturing efficiency without degrading rolling resistance, handling and endurance performance.

[008] Definitions:

[009] A “radial direction/orientation” is a direction/orientation perpendicular to axis of rotation of the tire. This direction/orientation corresponds to thickness orientation of the tire.

[010] An “axial direction/orientation” is a direction/orientation parallel to axis of rotation of the tire.

[011] A “circumferential direction/orientation” is a direction/orientation which is tangential to any circle centered on axis of rotation. This direction/orientation is perpendicular to both the axial direction/orientation and the radial direction/orientation.

[012] A “tire” means all types of elastic tire whether or not subjected to an internal pressure.

[013] A “tread” of a tire means a quantity of rubber material bounded by lateral surfaces and by two main surfaces one of which is intended to come into contact with ground when the tire is rolling.

[014] A “ply” is a layer of material such as nylon, polyester or steel in a form of cable, wire or strings arranged mutually parallel with one another with a given pitch coated with a rubber material.

[015] It is thus an object of the invention to provide a tire which provides improvement on manufacturing efficiency by reducing number of semi-finished product without degrading rolling resistance, handling and endurance performance.

[016] The present invention provides a tire comprising two beads designed to come into contact with a mounting rim, each bead comprising at least one annular reinforcing structure, two sidewalls extending radially outwardly from the beads, the two sidewalls meeting in a crown comprising at least one crown reinforcement surmounted by a tread intended to come into contact with ground during rolling, at least one carcass reinforcement extending from the beads through the sidewalls to the crown, the carcass reinforcement being anchored in the two beads by a turn-up around the annular reinforcing structure so as to form in each bead a main portion and a wrapped-around portion, each the wrapped-around portion extending radially on the outside as far as a turn-up end situated at a radial distance Hr from radially innermost point of the annular reinforcing structure of the bead, each the bead comprising a bead filler made of a rubber composition and situated radially on the outside of the annular reinforcing structure and at least partially between the main portion and the wrapped-around portion of the carcass reinforcement, the bead filler extending radially along with the carcass reinforcement as far as a radially outer end of the bead filler situated at a radial distance Hb from radially innermost point of the annular reinforcing structure of the bead, the radial distance Hb being greater than the radial distance Hr, a maximum thickness Tb of the bead filler radially below the turn-up end measured just above the annular reinforcing structure being greater than a thickness Te of the bead filler at the turn-up end measured perpendicular to the main portion of the carcass reinforcement, a maximum thickness Ta of the bead filler radially above the turn-up end measured perpendicular to the main portion of the carcass reinforcement being greater than 50% of the maximum thickness Tb of the bead filler radially below the turn-up end, an outside outline of the bead filler goes from the turn-up end through a combination of one or more arcs centered on the outside of the tire axial direction including or not including a straight line, to a point of the maximum thickness Ta of the bead filler radially above the turn-up end through a combination of one or more arcs centered on the inside of the tire axial direction including or not including a straight line, then as to decrease bead filler thickness toward a position of a tire equator, a tangent delta (tan 5) at 23 °C of a rubber composition in a region axially outside of the wrappedaround portion of the carcass reinforcement measured in accordance with ASTM D5992- 96 is lower than that of the rubber composition constituting the bead filler, the thickness Te of the bead filler at the turn-up end is at most equal to 90% of the maximum thickness Ta of the bead filler radially above the turn-up end, and in that the bead filler is one single profiled product.

[017] This arrangement provides an improvement on manufacturing efficiency by reducing number of semi-finished product without degrading rolling resistance, handling and endurance performance.

[018] Since the bead comprising the bead filler made of the rubber composition and situated radially on the outside of the annular reinforcing structure and at least partially between the main portion and the wrapped-around portion of the carcass reinforcement, the bead filler extending radially along with the carcass reinforcement as far as a radially outer end of the bead filler situated at the radial distance Hb from radially innermost point of the annular reinforcing structure of the bead, the radial distance Hb being greater than the radial distance Hr, and the tangent delta (tan 5) at 23 °C of the rubber composition in the region axially outside of the wrapped-around portion of the carcass reinforcement measured in accordance with ASTM D5992-96 is lower than that of the rubber composition constituting the bead filler, the bead filler can be made as one single profiled semi-finished product at manufacturing. Therefore it is possible to improve manufacturing efficiency of such the tire.

[019] Since the tangent delta (tan 5) at 23 °C of the rubber composition in the region axially outside of the wrapped-around portion of the carcass reinforcement measured in accordance with ASTM D5992-96 is lower than that of the rubber composition constituting the bead filler, a rigidity in the bead is optimized. Therefore it is possible to maintain rolling resistance and endurance performance at the same time.

[020] Since the maximum thickness Tb of the bead filler radially below the turn-up end measured just above the annular reinforcing structure being greater than the thickness Te of the bead filler at the turn-up end measured perpendicular to the main portion of the carcass reinforcement, and the maximum thickness Ta of the bead filler radially above the turn-up end measured perpendicular to the main portion of the carcass reinforcement is greater than 50% of the maximum thickness Tb of the bead filler radially below the turn-up end, a portion of the bead filler radially above the turn-up end allows to optimize lateral stiffness of the tire. Therefore it is possible to maintain handling performance.

[021] In another preferred embodiment, the radially outer end of the bead filler locates lower than or equal to a position of a tire equator.

[022] According to this arrangement, a comfort performance can be maintained by radially upper side of sidewall while also maintaining handling performance by radially lower side of sidewall and increasing manufacturing efficiency.

[023] In another preferred embodiment, the thickness Te of the bead filler at the turn-up end is at most equal to 90% of the maximum thickness Tb of the bead filler radially below the turn-up end or of the maximum thickness Ta of the bead filler radially above the turnup end whichever is smaller, and the thickness Te of the bead filler at the turn-up end is at least equal to 1.0 mm.

[024] If this thickness Te of the bead filler at the turn-up end is more than 90% of the maximum thickness Tb of the bead filler radially below the turn-up end or of the maximum thickness Ta of the bead filler radially above the turn-up end whichever is smaller, there is a risk that a weight of the bead filler becomes important leading degradation of rolling resistance. If this Te of the bead filler at the turn-up end is less than 1.0 mm, there is a risk that a region in the bead filler around the turn-up end becomes a cause of crack initiation leading degradation of endurance performance. By setting this thickness Te of the bead filler at the turn-up end more than 90% of the maximum thickness Tb of the bead filler radially below the turn-up end or of the maximum thickness Ta of the bead filler radially above the turn-up end whichever is smaller, and at least equal to 1.0 mm, it is possible to maintain rolling resistance and endurance performance while increasing manufacturing efficiency.

[025] In another preferred embodiment, the maximum thickness Ta of the bead filler radially above the turn-up end is at least equal to 75% of the maximum thickness Tb of the bead filler radially below the turn-up end.

[026] If this maximum thickness Ta of the bead filler radially above the turn-up end is less than 75% of the maximum thickness Tb of the bead filler radially below the turn-up end, there is a risk that handling performance maintenance/improvement via the portion of the bead filler radially above the turn-up end becomes insufficient. By setting this maximum thickness Ta of the bead filler radially above the turn-up end at least equal to 75% of the maximum thickness Tb of the bead filler radially below the turn-up end, it is possible to maintain handling performance while improving manufacturing efficiency.

[027] In another preferred embodiment, a thickness of the sidewall outside of the bead filler at the maximum thickness Ta of the bead filler radially above the turn-up end is at least equal to 0.5 mm.

[028] If this thickness of the sidewall outside of the bead filler at the maximum thickness Ta of the bead filler radially above the turn-up end is less than 0.5 mm, there is a risk that the sidewall would crack due to extensive continuous flexing leading degradation of endurance performance. By setting this thickness of the sidewall outside of the bead filler at the maximum thickness Ta of the bead filler radially above the turn-up end at least equal to 0.5 mm, it is possible to maintain endurance performance while improving manufacturing efficiency.

[029] This thickness of the sidewall outside of the bead filler at the maximum thickness Ta of the bead filler radially above the turn-up end is preferably at least equal to 0.8 mm, more preferably at least equal to 1.0 mm and still more preferably at least equal to 1.5 mm.

[030] In another preferred embodiment, an elastic modulus G’ of the rubber composition constituting the bead filler in accordance with ASTM D5992-96 measured at 23°C, 10Hz and 10% of strain is at least equal to 20 MPa.

[031] If this elastic modulus G’ of the rubber composition constituting the bead filler in accordance with ASTM D5992-96 measured at 23°C, 10Hz and 10% of strain is less than 20 MPa, there is a risk that the rigidity optimization in the bead becomes inappropriate leading degradation of rolling resistance, endurance and/or handling performance. By setting this elastic modulus G’ of the rubber composition constituting the bead filler in accordance with ASTM D5992-96 measured at 23°C, 10Hz and 10% of strain at least equal to 20 MPa, it is possible to maintain rolling resistance, handling and endurance performance while improving manufacturing efficiency.

[032] This elastic modulus G’ of the rubber composition constituting the bead filler in accordance with ASTM D5992-96 measured at 23°C, 10Hz and 10% of strain is preferably at least equal to 25 MPa and more preferably at least equal to 30 MPa.

[033] In another preferred embodiment, an elastic modulus G’ of the rubber composition in the region axially outside of the wrapped-around portion of the carcass reinforcement measured in accordance with ASTM D5992-96 measured at 23°C, 10Hz and 10% of strain is at most equal to 15 MPa.

[034] If this elastic modulus G’ of the rubber composition in the region axially outside of the wrapped-around portion of the carcass reinforcement measured in accordance with ASTM D5992-96 measured at 23°C, 10Hz and 10% of strain is more than 15 MPa, there is a risk that the rigidity optimization in the bead becomes inappropriate leading degradation of rolling resistance. By setting this elastic modulus G’ of the rubber composition in the region axially outside of the wrapped-around portion of the carcass reinforcement measured in accordance with ASTM D5992-96 measured at 23°C, 10Hz and 10% of strain at most equal to 15 MPa, it is possible to maintain rolling resistance while improving manufacturing efficiency.

[035] This elastic modulus G’ of the rubber composition in the region axially outside of the wrapped-around portion of the carcass reinforcement measured in accordance with ASTM D5992-96 measured at 23°C, 10Hz and 10% of strain is preferably at most equal to 12 MPa, more preferably at most equal to 10 MPa and still more preferably at most equal to 5 MPa.

[036] According to the arrangements described above, it is possible to provide a tire which provides improvement on manufacturing efficiency by reducing number of semifinished product without degrading rolling resistance, handling and endurance performance.

[037] Other characteristics and advantages of the invention arise from the description made hereafter in reference to the annexed drawings which show, as nonrestrictive examples, the embodiment of the invention.

[038] In these drawings:

Fig. 1 is a schematic cross sectional view of a tire according to a first embodiment of the present invention;

Fig. 2 a schematic cross sectional view of a tire according to a second embodiment of the present invention;

Fig. 3 is a schematic cross sectional view of a tire according to prior art;

[039] Preferred embodiment of the present invention will be described below referring to the drawings.

[040] A tire 1 according to a first embodiment of the present invention will be described referring to Fig. 1.

[041] Fig. 1 is a schematic cross sectional view of a tire according to a first embodiment of the present invention. Portions other than shown in this Fig. 1 are typical radial tire construction thus explanation of such portions will be omitted.

[042] The tire 1 is a tire comprising two beads 2 (only one shown in Fig. 1) designed to come into contact with a mounting rim (not shown), each bead 2 comprising at least one annular reinforcing structure 3, two sidewalls 4 (only one shown in Fig. 1) extending radially outwardly from the beads 2, the two sidewalls 4 meeting in a crown 5 comprising at least one crown reinforcement 52 surmounted by a tread 51 intended to come into contact with ground during rolling. The tire 1 further comprising at least one carcass reinforcement 6 extending from the beads 2 through the sidewalls 4 to the crown 5, the carcass reinforcement 6 being anchored in the two beads 2 by a turn-up around the annular reinforcing structure 3 so as to form in each bead 2 a main portion 61 and a wrapped-around portion 62, each the wrapped-around portion 62 extending radially on the outside as far as a turn-up end 63 situated at a radial distance Hr from radially innermost point of the annular reinforcing structure 3 of the bead 2. In this first embodiment, the tire 1 comprises one single carcass reinforcement 6 and two crown reinforcements 52.

[043] As shown in Fig. 1 , each the bead 2 comprising a bead filler 7 made of a rubber composition and situated radially on the outside of the annular reinforcing structure 3 and at least partially between the main portion 61 and the wrapped-around portion 62 of the carcass reinforcement 6, the bead filler 7 extending radially along with the carcass reinforcement 6 as far as a radially outer end of the bead filler 7 situated at a radial distance Hb from radially innermost point of the annular reinforcing structure 3 of the bead 2, the radial distance Hb being greater than the radial distance Hr, a maximum thickness Tb of the bead filler 7 radially below the turn-up end 63 measured just above the annular reinforcing structure 3 being greater than a thickness Te of the bead filler 7 at the turn-up end 63 measured perpendicular to the main portion 61 of the carcass reinforcement 6.

[044] As shown in Fig. 1, a maximum thickness Ta of the bead filler 7 radially above the turn-up end 63 measured perpendicular to the main portion 61 of the carcass reinforcement 6 is greater than 50% of the maximum thickness Tb of the bead filler 7 radially below the turn-up end 63. A tangent delta (tan 5) at 23 °C of a rubber composition in a region axially outside of the wrapped-around portion 62 of the carcass reinforcement 6 measured in accordance with ASTM D5992-96 is lower than that of the rubber composition constituting the bead filler 7. An elastic modulus G’ of the rubber composition constituting the bead filler 7 in accordance with ASTM D5992-96 measured at 23°C, 10Hz and 10% of strain is at least equal to 20 MPa. An elastic modulus G’ of the rubber composition in the region axially outside of the wrapped-around portion 62 of the carcass reinforcement 6 measured in accordance with ASTM D5992-96 measured at 23°C, 10Hz and 10% of strain is at most equal to 15 MPa.

[045] As shown in Fig. 1 , the radially outer end of the bead filler 7 locates lower than or equal to a position of a tire equator where a tire width becomes maximum when mounted onto nominal rim and inflated to nominal pressure, indicated as EQ.

[046] As shown in Fig. 1, the thickness Te of the bead filler 7 at the turn-up end 63 is at most equal to 90% of the maximum thickness Tb of the bead filler 7 radially below the turn-up end 63 or of the maximum thickness Ta of the bead filler 7 radially above the turn- up end 63 whichever is smaller, and the thickness Te of the bead filler 7 at the turn-up end 63 is at least equal to 1.0 mm. And the maximum thickness Ta of the bead filler 7 radially above the turn-up end 63 is at least equal to 75% of the maximum thickness Tb of the bead filler 7 radially below the turn-up end 63. In this first embodiment, the thickness Te of the bead filler 7 at the turn-up end 63 is 3.0 mm, the maximum thickness Tb of the bead filler 7 radially below the turn-up end 63 is 9.0 mm and the maximum thickness Ta of the bead filler 7 radially above the turn-up end 63 is 6.8 mm.

[047] As shown in Fig. 1 , the thickness of the sidewall 4 outside of the bead filler 7 at the maximum thickness Ta of the bead filler 7 radially above the turn-up end 63 is at least equal to 0.5 mm. In this first embodiment, the thickness of the sidewall 4 outside of the bead filler 7 at the maximum thickness Ta of the bead filler 7 radially above the turn-up end 63 is 2.5 mm.

[048] Since the bead 2 comprising the bead filler 7 made of the rubber composition and situated radially on the outside of the annular reinforcing structure 3 and at least partially between the main portion 61 and the wrapped-around portion 62 of the carcass reinforcement 6, the bead filler 7 extending radially along with the carcass reinforcement 6 as far as a radially outer end of the bead filler 7 situated at the radial distance Hb from radially innermost point of the annular reinforcing structure 3 of the bead 2, the radial distance Hb being greater than the radial distance Hr, and the tangent delta (tan 5) at 23 °C of the rubber composition in the region axially outside of the wrapped-around portion

62 of the carcass reinforcement 6 measured in accordance with ASTM D5992-96 is lower than that of the rubber composition constituting the bead filler 7, the bead filler 7 can be made as one single profiled semi-finished product at manufacturing. Therefore it is possible to improve manufacturing efficiency of such the tire by reducing number of semifinished product.

[049] Since the tangent delta (tan 5) at 23 °C of the rubber composition in the region axially outside of the wrapped-around portion 62 of the carcass reinforcement 6 measured in accordance with ASTM D5992-96 is lower than that of the rubber composition constituting the bead filler 7, a rigidity in the bead 2 is optimized. Therefore it is possible to maintain rolling resistance and endurance performance at the same time.

[050] Since the maximum thickness Tb of the bead filler 7 radially below the turn-up end

63 measured just above the annular reinforcing structure 3 being greater than the thickness Te of the bead filler 7 at the turn-up end 63 measured perpendicular to the main portion 61 of the carcass reinforcement 6, and the maximum thickness Ta of the bead filler 7 radially above the turn-up end 63 measured perpendicular to the main portion 61 of the carcass reinforcement 6 is greater than 50% of the maximum thickness Tb of the bead filler 7 radially below the turn-up end 63, a portion of the bead filler 7 radially above the turn-up end 63 allows to optimize lateral stiffness of the tire 1. Therefore it is possible to maintain handling performance.

[051] Since the radially outer end of the bead filler 7 locates lower than or equal to a position of a tire equator, a comfort performance can be maintained by radially upper side of sidewall 4 while also maintaining handling performance by radially lower side of sidewall 4 and increasing manufacturing efficiency by reducing number of semi-finished product.

[052] Since the thickness Te of the bead filler 7 at the turn-up end 63 is at most equal to 90% of the maximum thickness Tb of the bead filler 7 radially below the turn-up end 63 or of the maximum thickness Ta of the bead filler 7 radially above the turn-up end 63 whichever is smaller, and the thickness Te of the bead filler 7 at the turn-up end 63 is at least equal to 1.0 mm, it is possible to maintain rolling resistance and endurance performance while increasing manufacturing efficiency by reducing number of semifinished product.

[053] If this thickness Te of the bead filler 7 at the turn-up end 63 is more than 90% of the maximum thickness Tb of the bead filler 7 radially below the turn-up end 63 or of the maximum thickness Ta of the bead filler 7 radially above the turn-up end 63 whichever is smaller, there is a risk that a weight of the bead filler 7 becomes important leading degradation of rolling resistance. If this Te of the bead filler 7 at the turn-up end 63 is less than 1.0 mm, there is a risk that a region in the bead filler 7 around the turn-up end 63 becomes a cause of crack initiation leading degradation of endurance performance.

[054] Since the maximum thickness Ta of the bead filler 7 radially above the turn-up end 63 is at least equal to 75% of the maximum thickness Tb of the bead filler 7 radially below the turn-up end 63, it is possible to maintain handling performance while improving manufacturing efficiency by reducing number of semi-finished product.

[055] If this maximum thickness Ta of the bead filler 7 radially above the turn-up end 63 is less than 75% of the maximum thickness Tb of the bead filler 7 radially below the turnup end 63, there is a risk that handling performance maintenance/improvement via the portion of the bead filler 7 radially above the turn-up end 63 becomes insufficient.

[056] Since the thickness of the sidewall 4 outside of the bead filler 7 at the maximum thickness Ta of the bead filler 7 radially above the turn-up end 63 is at least equal to 0.5 mm, it is possible to maintain endurance performance while improving manufacturing efficiency by reducing number of semi-finished product.

[057] If this thickness of the sidewall 4 outside of the bead filler 7 at the maximum thickness Ta of the bead filler 7 radially above the turn-up end 63 is less than 0.5 mm, there is a risk that the sidewall 4 would crack due to extensive continuous flexing leading degradation of endurance performance.

[058] This thickness of the sidewall 4 outside of the bead filler 7 at the maximum thickness Ta of the bead filler 7 radially above the turn-up end 63 is preferably at least equal to 0.8 mm, more preferably at least equal to 1.0 mm and still more preferably at least equal to 1.5 mm.

[059] Since the elastic modulus G’ of the rubber composition constituting the bead filler 7 in accordance with ASTM D5992-96 measured at 23°C, 10Hz and 10% of strain is at least equal to 20 MPa it is possible to maintain rolling resistance, handling and endurance performance while improving manufacturing efficiency by reducing number of semifinished product.

[060] If this elastic modulus G’ of the rubber composition constituting the bead filler 7 in accordance with ASTM D5992-96 measured at 23°C, 10Hz and 10% of strain is less than 20 MPa, there is a risk that the rigidity optimization in the bead 2 becomes inappropriate leading degradation of rolling resistance, endurance and/or handling performance.

[061] This elastic modulus G’ of the rubber composition constituting the bead filler 7 in accordance with ASTM D5992-96 measured at 23°C, 10Hz and 10% of strain is preferably at least equal to 25 MPa and more preferably at least equal to 30 MPa.

[062] Since the elastic modulus G’ of the rubber composition in the region axially outside of the wrapped-around portion 62 of the carcass reinforcement 6 measured in accordance with ASTM D5992-96 measured at 23°C, 10Hz and 10% of strain is at most equal to 15 MPa, it is possible to maintain rolling resistance while improving manufacturing efficiency by reducing number of semi-finished product.

[063] If this elastic modulus G’ of the rubber composition in the region axially outside of the wrapped-around portion 62 of the carcass reinforcement 6 measured in accordance with ASTM D5992-96 measured at 23°C, 10Hz and 10% of strain is more than 15 MPa, there is a risk that the rigidity optimization in the bead 2 becomes inappropriate leading degradation of rolling resistance.

[064] This elastic modulus G’ of the rubber composition in the region axially outside of the wrapped-around portion 62 of the carcass reinforcement 6 measured in accordance with ASTM D5992-96 measured at 23°C, 10Hz and 10% of strain is preferably at most equal to 12 MPa, more preferably at most equal to 10 MPa and still more preferably at most equal to 5 MPa.

[065] The annular reinforcing structure 3 may have a shape different than circular shape, for example triangular or polygonal shape, or may be piles described in the document US5660656A. [066] A tire 21 according to a second embodiment of the present invention will be described referring to Fig. 2. Fig. 2 is a schematic cross sectional view of a tire according to a second embodiment of the present invention. The construction of this second embodiment is similar to that of the first embodiment other than the arrangement shown in Fig. 2, thus description will be made referring to Fig. 2.

[067] As shown in Fig. 2, a tire 21 is a tire comprising two beads 22 (only one shown in Fig. 2) designed to come into contact with a mounting rim (not shown), each bead 22 comprising at least one annular reinforcing structure 23, two sidewalls 24 (only one shown in Fig. 2) extending radially outwardly from the beads 22, the two sidewalls 24 meeting in a crown 25 comprising at least one crown reinforcement 252 surmounted by a tread 251 intended to come into contact with ground during rolling. The tire 21 further comprising at least one carcass reinforcement 26 extending from the beads 22 through the sidewalls 24 to the crown 25, the carcass reinforcement 26 being anchored in the two beads 22 by a turn-up around the annular reinforcing structure 23 so as to form in each bead 22 a main portion 261 and a wrapped-around portion 262, each the wrapped-around portion 262 extending radially on the outside as far as a turn-up end 263 situated at a radial distance Hr from radially innermost point of the annular reinforcing structure 23 of the bead 22. In this second embodiment, the tire 21 comprises two carcass reinforcements 26, one with the wrapped-around portion 262 and another without the wrapped-around portion, and two crown reinforcements 52.

[068] As shown in Fig. 2, each the bead 22 comprising a bead filler 27 made of a rubber composition and situated radially on the outside of the annular reinforcing structure 23 and at least partially between the main portion 261 and the wrapped-around portion 262 of the carcass reinforcement 26, the bead filler 27 extending radially along with the carcass reinforcement 26 as far as a radially outer end of the bead filler 27 situated at a radial distance Hb from radially innermost point of the annular reinforcing structure 23 of the bead 22, the radial distance Hb being greater than the radial distance Hr, a maximum thickness Tb of the bead filler 27 radially below the turn-up end 263 measured just above the annular reinforcing structure 23 being greater than a thickness Te of the bead filler 27 at the turn-up end 263 measured perpendicular to the main portion 261 of the carcass reinforcement 26.

[069] As shown in Fig. 2, the radially outer end of the bead filler 27 locates lower than or equal to a position of a tire equator where a tire width becomes maximum when mounted onto nominal rim and inflated to nominal pressure, indicated as EQ.

[070] As shown in Fig. 2, the thickness Te of the bead filler 27 at the turn-up end 263 is at most equal to 90% of the maximum thickness Tb of the bead filler 27 radially below the turn-up end 263 or of the maximum thickness Ta of the bead filler 27 radially above the turn-up end 263 whichever is smaller, and the thickness Te of the bead filler 27 at the turnup end 263 is at least equal to 1.0 mm. And the maximum thickness Ta of the bead filler 27 radially above the turn-up end 263 is at least equal to 75% of the maximum thickness Tb of the bead filler 27 radially below the turn-up end 263. In this first embodiment, the thickness Te of the bead filler 27 at the turn-up end 263 is 2.5 mm, the maximum thickness Tb of the bead filler 27 radially below the turn-up end 263 is 9.0 mm and the maximum thickness Ta of the bead filler 27 radially above the turn-up end 263 is 10.0 mm. [071] As shown in Fig. 2, the sidewall 24 is provided with a rim protector 8 which prevents direct contact between the mounting rim and an obstacle.

[072] Both the carcass reinforcements 26 may comprise wrapped-around portion 262.

[073] The invention is not limited to the examples described and represented and various modifications can be made there without leaving its framework. In particular, the invention may be combined with various known construction in crown.

[074] Fig. 3 is a schematic cross sectional view of a tire according to prior art. In this Fig. 3, a tire 101 comprising two beads 102 (only one shown in Fig. 3) designed to come into contact with a mounting rim (not shown), each bead 102 comprising one annular reinforcing structure 103, two sidewalls 104 (only one shown in Fig. 3) extending radially outwardly from the beads 102, the two sidewalls 104 meeting in a crown 105 comprising two crown reinforcements 1052 surmounted by a tread 1051 intended to come into contact with ground during rolling. The tire 101 further comprising two carcass reinforcements 106 extending from the beads 102 through the sidewalls 104 to the crown 105, one of the carcass reinforcement 106 being anchored in the two beads 102 by a turnup around the annular reinforcing structure 103 so as to form in each bead 102 a main portion 1061 and a wrapped-around portion 1062, each the wrapped-around portion 1062 extending radially on the outside as far as a turn-up end 1063. Each the bead 102 comprising a bead filler 107 made of a rubber composition and consisting of two portions, axially inner portion 107a situated radially on the outside of the annular reinforcing structure 103 and at least partially between the main portion 1061 and the wrapped- around portion 1062 of the carcass reinforcement 106 and extending radially along with the carcass reinforcement 106, and axially outer portion 107b situated axially outside of the wrapped-around portion 1062 and the axially inner portion 107a as far as a radially outer end of the bead filler 107 located close to a tire equator EQ.

[075] In order to confirm the effect of the present invention, two types of tires of Example to which the present invention is applied and one type of tire of Reference were prepared.

[076] The Example 1 was a tire as described in the above first embodiment. The Example 2 was a tire as described in the above second embodiment but without rim protector. The Reference was a tire according to prior art. All the Examples and Reference were made of the same rubber-based material, typical rubber-based material used for passenger car tire. The tire dimension of Examples and References were 235/55R19, mounted onto a rim of 7.5Jx19.

[077] Endurance tests:

[078] The endurance in the running was assessed by a running test of very long duration (40,000 km) on an automatic rolling machine, under a very high load (overload with respect to the rated load) and at the same speed, for a predefined number of kilometers, or a tire failure whichever is earlier. The tires tested were decomposed and were observed via well-trained expert whether there is a break of products in bead.

[079] The results are shown in table 1. In this table 1, results are represented by “O” meaning there is no break of products in bead.

[080] Rolling resistance tests:

[081] Rolling resistance was measured on a drum having a diameter of 1.7m at maximum nominal loads and inflation pressures at about 90 km/h. Rolling resistance as referenced in Table 1 refers to a gap of rolling resistance coefficients expressed in values of kg/T (kilograms of resistance force I ton of load) against Reference.

[082] Handling tests:

[083] A cornering power of unused test tires mounted onto a standard rim and inflated to internal pressure of 185 kPa were measured using a flat belt tire tester. A load of 740 daN was applied while tires driven at a constant speed of 80 kph, lateral force at a slip angle of ±1° was measured, and the lateral forces measured at +1° and at -1° were averaged.

[084] The results are also shown in table 1. In this table 1 , results are represented by an index of 100 for the Reference, higher the number indicates better the performance.

[085] [Table 1]

[086] As seen from table 1 , the Example shows maintenance, or even improvement on endurance, rolling resistance and handling performance while improving manufacturing efficiency by reducing number of semi-finished product, which cannot be achieved by tires disclosed in prior arts. The Example 1 tested on different day still showed -0.02 Kg/T gain in rolling resistance while maintaining other performance concerned reinforcing advantage of the present invention.

[087] Reference signs list [088] 1. 21 tire

[089] 2. 22 bead

[090] 3, 23 annular reinforcing structure

[091] 4, 24 sidewall [092] 5, 25 crown

[093] 51, 251 tread

[094] 52, 252 crown reinforcement

[095] 6, 26 carcass reinforcement

[096] 61, 261 main portion of carcass reinforcement [097] 62, 262 wrapped-around portion of carcass reinforcement

[098] 63, 263 turn-up end

[099] 7, 27 bead filler

[0100] 8 nm protector

Claims

REVENDICATIONS

1. A tire (1) comprising two beads (2) designed to come into contact with a mounting rim, each bead (2) comprising at least one annular reinforcing structure (3), two sidewalls (4) extending radially outwardly from the beads (2), the two sidewalls (4) meeting in a crown (5) comprising at least one crown reinforcement (52) surmounted by a tread (51) intended to come into contact with ground during rolling, at least one carcass reinforcement (6) extending from the beads (2) through the sidewalls (4) to the crown (5), the carcass reinforcement (6) being anchored in the two beads (2) by a turn-up around the annular reinforcing structure (3) so as to form in each bead (2) a main portion (61) and a wrappedaround portion (62), each the wrapped-around portion (62) extending radially on the outside as far as a turn-up end (63) situated at a radial distance Hr from radially innermost point of the annular reinforcing structure (3) of the bead (2), each the bead (2) comprising a bead filler (7) made of a rubber composition and situated radially on the outside of the annular reinforcing structure (3) and at least partially between the main portion (61) and the wrapped-around portion (62) of the carcass reinforcement (6), the bead filler (7) extending radially along with the carcass reinforcement (6) as far as a radially outer end of the bead filler (7) situated at a radial distance Hb from radially innermost point of the annular reinforcing structure (3) of the bead (2), the radial distance Hb being greater than the radial distance Hr, a maximum thickness Tb of the bead filler (7) radially below the turn-up end (63) measured just above the annular reinforcing structure (3) being greater than a thickness Te of the bead filler (7) at the turn-up end (63) measured perpendicular to the main portion (61) of the carcass reinforcement (6), a maximum thickness Ta of the bead filler (7) radially above the turn-up end (63) measured perpendicular to the main portion (61) of the carcass reinforcement (6) being greater than 50% of the maximum thickness Tb of the bead filler (7) radially below the turn-up end (63), an outside outline of the bead filler (7) goes from the turn-up end (63) through a combination of one or more arcs centered on the outside of the tire axial direction including or not including a straight line, to a point of the maximum thickness Ta of the bead filler (7) radially above the turn-up end (63) through a combination of one or more arcs centered on the inside of the tire axial direction including or not including a straight line, then as to decrease bead filler thickness toward a position of a tire equator, the tire being characterized in that a tangent delta (tan 5) at 23 °C of a rubber composition in a region axially outside of the wrapped-around portion (62) of the carcass reinforcement (6) measured in accordance with ASTM D5992-96 is lower than that of the rubber composition constituting the bead filler (7), and in that the thickness Te of the bead filler (7) at the turn-up end (63) is at most equal to 90% of the maximum thickness Ta of the bead filler (7) radially above the turn-up end (63), and in that the bead filler (7) is one single profiled product.

2. The tire (1) according to Claim 1, wherein the radially outer end of the bead filler (7) locates lower than or equal to the position of the tire equator.

3. The tire (1) according to Claim 1 or Claim 2, wherein the thickness Te of the bead filler (7) at the turn-up end (63) is at most equal to 90% of the maximum thickness Tb of the bead filler (7) radially below the turn-up end (63) or of the maximum thickness Ta of the bead filler (7) radially above the turn-up end (63) whichever is smaller, and wherein the thickness Te of the bead filler (7) at the turn-up end (63) is at least equal to 1.0 mm.

4. The tire (1) according to any one of the Claims 1 to 3, wherein the maximum thickness Ta of the bead filler (7) radially above the turn-up end (63) is at least equal to 75% of the maximum thickness Tb of the bead filler (7) radially below the turn-up end (63).

5. The tire (1) according to any one of the Claims 1 to 4, wherein a thickness of the sidewall (4) outside of the bead filler (7) at the maximum thickness Ta of the bead filler (7) radially above the turn-up end (63) is at least equal to 0.5 mm.

6. The tire (1) according to any one of the Claims 1 to 5, wherein an elastic modulus G’ of the rubber composition constituting the bead filler (7) in accordance with ASTM D5992-96 measured at 23°C, 10Hz and 10% of strain is at least equal to 20 MPa.

7. The tire (1) according to any one of the Claims 1 to 6, wherein an elastic modulus G’ of the rubber composition in the region axially outside of the wrapped-around portion (62) of the carcass reinforcement (6) measured in accordance with ASTM D5992-96 measured at 23°C, 10Hz and 10% of strain is at most equal to 15 MPa.