RADIAL TIRE

Description

Field of the Invention

[0001] The present invention relates to a pneumatic radial tire. More particularly, the present invention relates to the structure of a radial ply tire for passenger vehicles such as cars but also light trucks, buses, coaches and the like.Background of the Invention

[0002] In an effort to reduce vehicle emissions and to conserve fuel, there continues to be a long felt need to reduce rolling resistance of tires, which can be achieved by reducing the weight of the tires. Reducing tire weight can be accomplished by reducing rubber thickness, for example in the sidewall portion and / or bead portions, and / or by reducing weight of the internal structure of the tire, such as of reinforcing elements. However, any reduction in the weight of the tire should desirably be accomplished in a manner that does not compromise tire performance characteristics and / or service life. In particular, weight reduction can be of particular interest for tires of passenger cars that make up the majority of vehicles in road traffic.

[0003] Therefore, there is a need to provide a lightweight pneumatic radial tire upholding the usual quality in tire performance, such as stiffness and durability. It was found that the pneumatic radial tire achieves these objectives.

[0004] EP 3 599 108 A1 describes a tire in accordance with the preamble of claim 1.Summary of the Invention

[0005] The invention relates to a tire in accordance with claim 1.

[0006] Dependent claims refer to preferred embodiments of the invention.

[0007] Therefore, the present invention preferably relates to a pneumatic radial tire comprising a tire carcass comprising: a tread portion comprising a tread disposed on the tire carcass; a pair of sidewall portions adjacent to the tread portion; a carcass ply P C extending circumferentially about the tire and exhibiting two ply endings, wherein each ply ending comprises a first contact section S 1 adjacent to a turn-up section S T adjacent to a second contact section S 2 , said second contact section forming the end portion of the ply ending; a pair of bead portions adjacent to the sidewall portions, wherein each bead portion comprises a bead core, one or more apex elements and one of the two ply endings of P C , wherein, in each bead portion, the ply ending comprised therein forms a sealed enclosure containing the bead core, said sealed enclosure exhibiting a ply-to-ply contact section S C formed by the first contact section S 1 and the second contact section S 2 , and further exhibiting a surrounding section formed by the turn-up section S T ; wherein, in each bead portion, at least one apex element E A of the one or more apex elements is located axially outwards from the ply-to-ply contact section S C and wherein at least a portion of the axially inward surface of said at least one apex element E A is in direct contact with the axially outward surface of the ply-to-ply contact section S C .Definitions

[0008] In the context of the present invention, the term "in direct contact with" in the expression "at least one apex element E A is in direct contact with the radially outward surface of the ply-to-ply contact section S C " means that there is no material or compound or layer located between the apex element E A and the axially outward surface of ply-to-ply contact section.

[0009] In the context of the present invention, the term "ply-to-ply contact section" refers to a section wherein the first contact section S 1 of P C and the second contact section S 2 of P C are in direct contact with each other to form the sealed enclosure.

[0010] In the context of the present invention, the term "tread portion" relates to a portion / section of the tire carcass onto which the tread is disposed.Brief Description of the Drawings

[0011] The invention will be described by way of example and with reference to the accompanying drawings in which: FIG. 1 is a schematic fragmental cross-sectional view of a preferred embodiment of a tire according to the present invention; FIG. 2 is an enlarged fragmental cross-sectional view of the bead portion of a preferred embodiment of a tire according to the present invention; FIG. 3 is a schematic fragmental cross-sectional view of a preferred embodiment of a tire according to the present invention; FIG. 4 is a schematic fragmental cross-sectional view of an enlarged portion of a tire according to a preferred embodiment of the present invention. FIG. 5 is a spider chart comparing the pneumatic radial tire properties of the present invention compared to a pneumatic radial tire known in the art. Detailed Description of Preferred Embodiments of the Invention

[0012] Disclosed is a pneumatic radial tire comprising a tire carcass comprising a tread portion comprising a tread disposed on the tire carcass; a pair of sidewall portions adjacent to the tread portion; a carcass ply P C extending circumferentially about the tire and exhibiting two ply endings, wherein each ply ending comprises a first contact section S 1 adjacent to a turn-up section S T adjacent to a second contact section S 2 , said second contact section forming the end portion of the ply ending; a pair of bead portions adjacent to the sidewall portions, wherein each bead portion comprises a bead core, one or more apex elements and one of the two ply endings of P C , wherein, in each bead portion, the ply ending comprised therein forms a sealed enclosure containing the bead core, said sealed enclosure exhibiting a ply-to-ply contact section S C formed by the first contact section S 1 and the second contact section S 2 , and further exhibiting a surrounding section formed by the turn-up section S T ; wherein, in each bead portion, at least one apex element E A of the one or more apex elements is located axially outwards from the ply-to-ply contact section S C and wherein at least a portion of the axially inward surface of said at least one apex element E A is in direct contact with the axially outward surface of the ply-to-ply contact section S C .

[0013] Preferably, in each bead portion, the ply ending is turned-up radially outwards and, in the ply-to-ply contact section S C , the second contact section S 2 is located axially outwards from the first contact section S 1 .

[0014] Preferably, in each bead portion, none of the one or more apex elements is contained in the sealed enclosure.

[0015] Preferably, the carcass ply P C comprises a rubber composition and reinforcing cords embedded in the rubber composition.

[0016] Preferably, the reinforcing cords are metal cords, such as steel, or organic fiber cords, more preferably the reinforcing cords are made of organic fibers. More preferably the organic fiber cords are made of one or more of polyester, rayon, nylon, aromatic polyamide, such as aramid, more preferably one or more of polyester and aromatic polyamide, such as aramid. In the context of the present invention, it is believed that using organic fibers such as aramid fibers for reinforcing the ply permits to reduce the weight of the tires which is beneficial for the overall properties of such tires.

[0017] Preferably, the carcass ply P C has a radial ply structure. In other words, it is a "radial ply" which means that said ply has reinforcing cords which are oriented at an angle of between 65° and 90° with respect to the equatorial plane A of the tire.

[0018] When the tire is mounted onto the nominal ETRTO rim and inflated at 2.2 bar, the ply ending height H P in each bead portion is in the range of from 1.0 to 1.75 inches (1 inch = 2.54 cm), more preferably in the range of from 1.24 to 1.6 inches, the ply ending height H P being defined as the radial distance between the bead toe and the end point of the ply ending. In the context of the present invention, the bead toe represents the lowest "point" of the tire in each bead portion.

[0019] Preferably, each bead core has a substantially pentagonal cross-section, more preferably a pentagonal cross-section.

[0020] Preferably, at least two sides of the substantially pentagonal cross-section of the bead core have the same length, more preferably two sides of the substantially pentagonal cross-section of the bead core have the same length.

[0021] Preferably, each bead core comprises an elastomeric composition and bead wires.

[0022] Preferably, each bead wire is made of metallic filaments. Preferably, the metallic filaments of each bead wire are made of steel. Preferably, each bead wire has a diameter in the range of from 0.7 to 1.2 mm.

[0023] Preferably, the bead wires of the bead core are surrounded by the elastomeric composition and arranged next to each other forming a bead core layer.

[0024] Preferably, the bead core comprises more than one bead core layer, the layers being arranged on top of one other for forming the substantially pentagonal bead core cross section.

[0025] Preferably, the shortest layer is the top layer and the far most layer of the top layer is the bottom layer. Preferably, the width of the bottom layer is in the range of from 2 to 6 mm. Preferably, the width of the top layer is in the range of from 0.7 to 2.4 mm.

[0026] Preferably, the maximum axial width of the bead core is in the range of from 3 to 10 mm.

[0027] When the tire is mounted onto the nominal ETRTO rim and inflated at 2.2 bar, the apex height H A in each bead portion is in the range of from 1.1 to 2.5 inches (1 inch = 2.54 cm), preferably in the range of from 1.3 to 2.2 inches, the apex height H A being defined as the maximum radial distance between the bead toe and the at least one apex element E A , with H A > H P , H P being the ply ending height as defined herein above.

[0028] Preferably, each apex element is an extrudate. Preferably, each apex element comprises at least one polymer. It is believed that the apex elements used in the present invention permits to provide a specific rigidity and stiffness to the tire due to its position in the tire and / or chemical composition. Preferably, each bead portion comprises one apex element.

[0029] Preferably, in the bead portions, no reinforcing member is in direct contact with at least a part of the outer surface of the sealed enclosure formed by the ply ending.

[0030] Preferably, no reinforcing member is located in the bead portions.

[0031] Preferably, the reinforcing member is a layer comprising a fabric or metallic wires, such as steel wires. In the context of the present invention, it is believed that reinforcing member(s) (or chipper(s)) are not necessary to reinforce the bead portions thanks to the particular disposition of the ply, the bead core and the one or more apex elements in each bead portion. Reinforcing member and chipper are used interchangeably in the present invention.

[0032] Preferably, the sealed enclosure comprises only the bead core.

[0033] Preferably, the tread comprises one or more grooves and one or more layers of a polymeric composition.

[0034] Preferably, when the tire is mounted onto the nominal ETRTO rim and inflated at 2.2 bar, the tire further comprises an overlay ply and a belt layer, the overlay ply being located between the tread and the belt layer and the belt layer being located between the overlay ply and the carcass ply. Preferably, the belt layer comprises one or more belt plies, wherein at least one belt ply P B of the one or more belt plies has a radial width W PB , in the range of from 80 to 100 percent, more preferably from 85 to 95 percent, more preferably from 88 to 92 percent, W R , W R being the rim width.

[0035] Preferably, the belt layer comprises two belt plies.

[0036] Preferably, when the tire is mounted onto the nominal ETRTO rim and inflated at 2.2 bar, the at least one belt ply P B is arranged in parallel to the carcass ply P C over an axial width W par , wherein W par is in the range of from 80 to 95 percent, more preferably in the range of from 85 to 90 percent, W R with W par < W PB .

[0037] Preferably, when the tire is mounted onto the nominal ETRTO rim and inflated at 2.2 bar, the tread, comprising one or more grooves 12, has a thickness T GB being in the range of from 1 to 3.4 mm, more preferably in the range of from 1.2 to 2.2 mm, more preferably of about 1.5 mm, T GB being defined as the minimal radial distance between the deepest outer surface of the one or more grooves 12 and the outmost surface of the overlay ply.

[0038] Preferably, the at least one belt ply comprises a rubber composition comprising, embedded therein, reinforcing wires.

[0039] Preferably, the reinforcing wires are one or more of metal wires and organic fiber wires, preferably metal reinforcing wires or organic fiber reinforcing wires. Preferably, the metal of the metal reinforcing wires is steel. Preferably, the reinforcing wires are metal reinforcing wires.

[0040] Alternatively, preferably, the reinforcing wires are organic fiber reinforcing wires. Preferably, the organic fiber of the organic fiber reinforcing wires is made of one or more of polyester, rayon, nylon and aromatic polyamide, preferably made of aromatic polyamide, such as aramid. More preferably, the at least one belt ply P B comprises a rubber composition comprising, embedded therein, aramid reinforcing wires. Preferably, the aramid reinforcing wires are arranged in a parallel arrangement, a woven arrangement, or a knitted arrangement.

[0041] Each sidewall portion extends radially upward from each bead portion towards the tread portion.

[0042] Preferably, each sidewall portion comprises a sidewall layer extending from the outer surface of the carcass ply to the outer surface of the sidewall portion and having a thickness T SW , wherein T SW has a minimum value in the range of from 1 to 5 mm, more preferably in the range of from 1.5 to 2.5 mm, more preferably of 2 mm.

[0043] Preferably, the tire is designed for being mounted onto the nominal ETRTO rim, wherein the tire is more preferably inflated at a pneumatic pressure of 2.2 bar.

[0044] Preferably, when the tire is mounted onto the nominal ETRTO rim and inflated at 2.2 bar, the axial ply width W P is in the range of from 95 to 116 percent W R , more preferably from 108 to 116 percent W R , W R being the axial rim width, the axial ply width W P being defined as the maximum axial distance between the carcass ply in the first sidewall portion and the carcass ply in the second sidewall portion.

[0045] Preferably, the pneumatic radial tire of the present invention is a pneumatic radial tire for passenger vehicles such as cars but also light trucks, buses, coaches and the like. More preferably, the pneumatic tire is a pneumatic radial tire for passenger cars.

[0046] FIG. 1 is a schematic fragmental cross-sectional view of a preferred embodiment of a tire according to the present invention. The pneumatic radial tire 1 comprises a tread 3, a pair of sidewall portions, including the sidewall portion 4, the second one being not shown in the figure, adjacent to the tread, a carcass ply 5 (P C ) extending circumferentially about the tire 1 and exhibiting two ply endings or ply ending portions 20, only one is shown in FIG. 1, wherein each such ply ending or ply ending portion 20 comprises a first ply contact section 21 adjacent to and radially outwards of a ply turn-up section 22, said ply turn-up section 22 being adjacent to a second ply contact section 23, said second ply contact section 23 forming the end of the ply ending or ply ending portion 20 and being radially outwards of the ply turn-up section 22, a pair of bead portions adjacent to the sidewall portions 4, wherein each bead portion comprises a bead core 7, an apex element 6 and one of the two ply endings or ply endings portions 20 of the carcass ply 5. Each sidewall portion 4 extends radially upward from each bead portion towards the tread portion.

[0047] In each bead portion, the ply ending or ply ending portion 20 comprised therein forms a sealed enclosure 30 containing the bead core 7, said sealed enclosure 30 exhibiting a ply-to-ply contact section 11 (S C ) formed by the first ply contact section 21 and the second ply contact section 23, and further exhibiting a surrounding section formed by the ply turn-up section 22.

[0048] The apex element 6 is located axially outwards from the ply-to-ply contact section 11 and at least a portion of the axially inward surface of said apex element 6 is in direct contact with the axially outward surface of the ply-to-ply contact section 11.

[0049] Preferably, the apex element 6 extends from radially innermost point 31 to a radially outermost point 32, the radially innermost point 31 overlapping with the bead core 7 when viewed in the axial direction and the radially outermost point 32 being radially outwards of the ply-to-ply contact section 11.

[0050] The tire 1 preferably further comprises an overlay ply 13 and a belt layer or belt package 8 comprising one or more belts 9, preferably two belts 9. The overlay ply 13 is located radially between the tread 3 and the belt layer 8. The belt layer or belt package 8 is located radially between the overlay ply 13 and the carcass ply 5. D represents the radially upmost or outermost point of the second ply contact section 23 of the ply ending or ply ending portion 20 and A represents a symmetric center plan of the tire 1. H P is the height of the end of the ply ending or ply ending portion, which is measured relative to the bead toe 10 in the radial direction. H A is the apex element height, i.e., ending at the radially outermost point 32, and is also measured relative to the bead toe 10.

[0051] FIG. 2 is an enlarged portion of the tire of FIG. 1, showing the bead core 7 having a preferably substantially pentagonal cross-section, the apex element 6 and the ply-to-ply contact section 11. The bead core 7 is the preferably only element in the sealed enclosure.

[0052] FIG. 3 is a schematic fragmental cross-sectional view of a preferred embodiment of the tire according to the present invention. The tire 1 comprises the same elements as in FIG.1 but not all are shown in FIG.3. Said tire 1 is mounted onto the nominal ETRTO rim and inflated at 2.2 bar. Fig. 3 shows the sidewall layer thickness T SW , the radial width W par over which the one or more belts 9 in the belt layer or belt package 8 are arranged in parallel to the carcass ply 5, the axial width W PB of belt layer or belt package 8 and also the axial width of the rim W R .

[0053] FIG. 4 is a schematic fragmental cross-sectional view of a preferred embodiment of an enlarged portion of a tire according to the present invention. As may be seen on FIG. 4, the enlarged portion of the tire 1 focuses on the bead portion. Indeed, the bead portion comprises the bead core 7, the apex element 6 and the carcass ply 5 which encloses the bead core 7.

[0054] The ply-to-ply contact section 11 is in direct contact with at least a portion of the apex element 6.

[0055] Preferably, the ply-to-ply contact section 11 is in direct contact with the axially innermost surface of the apex element 6.

[0056] A portion of the carcass ply 5 radially above and below said ply-to-ply contact section 11 is preferably also in contact with the apex element.

[0057] Preferably, the bead core 7 is the only element in the sealed enclosure 30. The bead core 7 preferably comprises an elastomeric composition and bead wires.

[0058] A difference between Fig. 4 and Figs. 1 and 2 is the shape of the apex element 6.

[0059] FIG. 5 is a spider chart comparing the pneumatic radial tire properties of a tire according to the present invention compared to a pneumatic radial tire known in the art. For the forces and moments and braking, the tested tires have been mounted on a 9.5" rim and inflated at 2.9 bar. For the rolling resistance (RR), the tested tires have been mounted on a 9" rim and inflated at 2.5 bar. As may be taken from Fig. 5, the pneumatic radial tire of the present invention has a lower weight, exhibits reduced (improved) rolling resistance (RR), an improved cornering stiffness and shows lower slip angle at Fy max compared to a tire known in the art which comprises neither a ply-to-ply contact section nor an apex element located radially outwards from the ply-to-ply contact section, wherein at least a portion of the radially inward surface of said apex element is in direct contact with the radially outward surface of the ply-to-ply contact section as required by the present invention. Further, the cords and wires used in the inventive tire were those defined in the present invention and different from those in the prior art tire. Further, it is noted that the dry braking, lateral stiffness, aligning stiffness and Fy max for the tire of the present invention are as good as the tire known in the art.

Claims

1. A pneumatic radial tire comprising a tire carcass, the tire (1) comprising a tread portion comprising a tread (3) disposed on the tire carcass; a pair of sidewall portions (4) adjacent to the tread portion; a carcass ply (5, PC) extending circumferentially about the tire (1) and exhibiting two ply ending portions (20), wherein each ply ending portion (20) comprises a first ply contact section (21, S1) adjacent to a ply turn-up section (22, ST), said ply turn-up section (22, ST) being adjacent to a second ply contact section (23, S2), said second ply contact section (23, S2) forming or including the end of the ply ending portion (20); a pair of bead portions adjacent to the sidewall portions (4), wherein each bead portion comprises a bead core (7), one or more apex elements (6) and one of the two ply ending portions (20) of said carcass ply (5, PC), wherein, in each bead portion, the ply ending portion (20) comprised therein forms a sealed enclosure (30) containing the bead core (7), said sealed enclosure (30) exhibiting a ply-to-ply contact section (11, SC) formed by the first ply contact section (21, S1) and the second ply contact section (22, S2), and further exhibiting a surrounding section formed by the ply turn-up section (22, ST); wherein, in each bead portion, at least one apex element (6, EA) of the one or more apex elements (6) is located axially outwards from the ply-to-ply contact section (11, SC) and wherein at least a portion of the axially inward surface of said at least one apex element (6, EA) is in direct contact with an axially outward surface of the ply-to-ply contact section (11, SC); and; wherein the apex height (HA) is greater than the ply ending height (HP), the ply ending height (HP) being defined as the radial distance between the bead toe (10) and the radial outermost point or end of the ply ending portion (20); characterized in that, when the tire (1) is mounted onto the nominal ETRTO rim and inflated at 2.2 bar, (i) the ply ending height (HP) in each bead portion is in the range of from 2.54 cm to 4.46 cm, the ply ending height (HP) being defined as the radial distance between the bead toe (10) and the radial outermost point or end of the ply ending portion (20); and (ii) the apex height (HA) in each bead portion is in the range of from 2.79 cm to 6,35 cm, the apex height (HA) being defined as the maximum radial distance between the bead toe and the at least one apex element (EA).

2. The pneumatic radial tire of claim 1, wherein, in each bead portion, the ply ending portion (20) is turned-up radially outwards and wherein in the ply-to-ply contact section (11, SC), the second ply contact section (22, S2) is located axially outwards from the first contact section (21, S1).

3. The pneumatic radial tire of claim 1 or 2, wherein, in each bead portion, none of the one or more apex elements (6) is contained in the sealed enclosure (30).

4. The pneumatic radial tire of at least one of the previous claims, wherein each bead core (7) has a substantially pentagonal cross-section, and, optionally, wherein at least two sides of the substantially pentagonal cross-section of the bead core (7) have the same length.

5. The pneumatic radial tire of at least one of the previous claims, wherein each bead core (7) comprises an elastomeric composition and bead wires.

6. The pneumatic radial tire of at least one of the previous claims, wherein, in the bead portions, no reinforcing member is in direct contact with at least a part of the outer surface of the sealed enclosure (30) formed by the ply ending portion (20).

7. The pneumatic radial tire of at least one of the previous claims, wherein the tread (3) comprises one or more grooves (12) and one or more layers of a polymeric composition.

8. The pneumatic radial tire of at least one of the previous claims, wherein, when the tire (1) is mounted onto the nominal ETRTO rim and inflated at 2.2 bar, the tire (1) further comprises an overlay ply (13) and a belt layer or belt package (8) comprising one or more belt plies (9), the overlay ply (13) being located between the tread (3) and the belt layer or belt package (8) and the belt layer or belt package (8) being located between the overlay ply (13) and the carcass ply (5); wherein at least one belt layer or belt ply (9, PB) has an axial width (WPB) in the range of from 80 to 100 percent, preferably 85 to 95 percent, of the axial rim width (WR).

9. The pneumatic radial tire of claim 8, wherein, when the tire (1) is mounted onto the nominal ETRTO rim and inflated at 2.2 bar, (i) the at least one belt layer or ply (9, PB) is arranged in parallel to the carcass ply (5, PC) over an axial width (Wpar), wherein said axial width (Wpar) is in the range of from 80 to 95 percent of said axial rim width (WR) with Wpar < WPB; and / or (ii) the tread (3), comprising one or more grooves (12), has a radial thickness (TGB) being in the range of from 1 to 3.4 mm, said radial thickness (TGB) being defined as the minimal radial distance between the deepest outer surface of the one or more grooves (12) and the radially outmost surface of the overlay ply (13).

10. The pneumatic radial tire of at least one of the previous claims 8 or 9, wherein the at least one belt ply (9, PB) comprises a rubber composition comprising, embedded therein, reinforcing wires or cords, preferably steel or aramid wires or cords.

11. The pneumatic radial tire of at least one of the previous claims, wherein each sidewall portion (4) comprises a sidewall layer extending from the axially outer surface of the carcass ply (5) to the axially outer surface of the sidewall portion and having a thickness (TS), wherein said thickness (TSW) has a minimum value in the range of from 1 to 5 mm.

12. The pneumatic radial tire of at least one of the previous claims, wherein, when the tire (1) is mounted onto the nominal ETRTO rim and inflated at 2.2 bar, the axial carcass ply width (WP) is in the range of from 95 to 116 percent of the rim width (WR), the ply width (WP) being defined as the maximum axial distance between the carcass ply (5) in the first sidewall portion and the carcass ply (5) in the second sidewall portion.

13. The pneumatic radial tire of at least one of the previous claims, wherein the tire (1) is a pneumatic radial tire for passenger cars.