RADIAL TIRE

Abstract

This invention relates to pneumatic radial tires which exhibit improved rolling resistance (provide better fuel economy) and improved performance characteristics. More particularly, this invention relates to the structure of radial ply tires for heavy load vehicles such as trucks, buses, and the like. It is based upon that finding that a defined profile of the outer surface of the sidewall portion can lead to a tire with reduced rolling resistance and a reduced generation of heat. The reduction in rolling resistance is obtained by a specific shaping of the bead portion of the tire which allows a bead mass reduction with an acceptable trade-off with regard to bead durability.

Claims

1. A radial tire, the tire comprising a tread portion, a pair of sidewall portions, a pair of bead portions, wherein each bead portion includes a bead core, a carcass reinforcing ply including a ply turnup placed at each bead core, each ply turnup including a radially outward end forming a ply ending; and a chipper being disposed at each ply turnup with a radially outward chipper end that is radially below the ply ending; wherein the profile of the outer surface of the sidewall portion is at a distance G from the carcass reinforcing ply from the most axially outward point of the said outer surface until point A, and joins the outer surface of the bead portion at the point B wherein the outer surface of the sidewall portion follows two successive curves with a first curve extending from the point A is having a centre of curvature positioned axially outward of the carcass reinforcing ply and a second curve joining the point B having a centre of curvature positioned axially inward of the outer surface of the tire; wherein the profile of the outer surface of the sidewall portion in the portion extending from points A to B is tangent to a circle C1 centred on the ply ending and having a radius R1 ranging from 5 to 15 mm, and wherein the profile of the outer surface of the sidewall portion in the point B is tangent to a circle C2 centred on the radially outward chipper end.

2. The radial tire of claim 1 wherein the circle C2 centred on the radially outward chipper end has a radius R2 which is within the range of 2 mm to 12 mm.

3. The radial tire of claim 1 wherein the ply ending and the radially outward chipper end are separated by a distance of at least 8 mm.

4. The radial tire of claim 1 wherein the distance of the point A from the ply ending is within the range of 10 mm to 30 mm.

5. The radial tire of claim 1 wherein the second curve joining the point B has a radius of curvature R4 that is greater than the radius R2 of the circle C2.

6. The radial tire of claim 1 wherein the two successive curves are arranged end to end.

7. The radial tire of claim 1 wherein the two successive curves are separated by a flat portion.

8. The radial tire of claim 1 wherein the chipper comprises the radially outward chipper end and an opposite chipper end, with the radially outward chipper end being axially outward the opposite chipper end with the height of the opposite chipper end is at least 25 mm; the height of the opposite chipper end is determined in the radial direction and measured from the bead toe.

9. A radial tire, the tire comprising a tread portion, a pair of sidewall portions, a pair of bead portions, wherein each bead portion includes a bead core, a carcass reinforcing ply including a ply turnup at each bead core, each ply turnup including a radially outward end forming a ply ending; and a chipper being disposed at each ply turnup with a radially outward chipper end that is radially below the ply ending; wherein the profile of the outer surface of the sidewall portion is at a distance G from the carcass reinforcing ply from the most axially outward point of the said outer surface until point A, and joins the outer surface of the bead portion at the point B wherein the outer surface of the sidewall portion follows two successive curves with a first curve extending from the point A is having a centre of curvature positioned axially outward of the carcass reinforcing ply and a second curve joining the point B having a centre of curvature positioned axially inward of the outer surface of the tire; wherein the profile of the outer surface of the sidewall portion in the portion extending from points A to B is tangent to a circle C1 centred on the ply ending, and further wherein the distance of the point A from the ply ending is ranging from 10 to 30 mm.

10. The radial tire of claim 9 wherein the profile of the outer surface of the sidewall portion in the point B is tangent to a circle C2 centred on the radially outward chipper end and having a radius R2 ranging from 2 mm to 12 mm.

11. The radial tire of claim 9 wherein the circle C1 centred on the ply ending has a radius R1 ranging from 5 mm to 15 mm.

12. The radial tire of claim 9 wherein the height of the outward ply ending is at least 35 mm with the height of the outward ply ending being determined in the radial direction and measured from the bead toe.

13. The radial tire of claim 9 wherein the distance G is equal to or lower than the radius R1 of the circle C1 centred on the ply ending.

14. The radial tire of claim 9 wherein the second curve extends radially outwardly past the point B.

15. A radial tire, the tire comprising a tread portion, a pair of sidewall portions, a pair of bead portions, wherein each bead portion includes a bead core, a carcass reinforcing ply including a ply turnup at each bead core, each ply turnup including a radially outward end forming a ply ending; and a chipper being disposed at each ply turnup; wherein the profile of the outer surface of the sidewall portions is at a distance G from the carcass reinforcing ply from the most axially outward point of the said outer surface until point A, and joins the outer surface of the bead portion at the point B wherein the outer surface of the sidewall portion follows two successive curves with a first curve extending from the point A is having a centre of curvature positioned axially outward of the carcass reinforcing ply and a second curve joining the point B having a centre of curvature positioned axially inward of the outer surface of the tire; wherein the profile of the outer surface of the sidewall portion in the portion extending from points A to B is tangent to a circle C1 centred on the ply ending, wherein the profile of the outer surface of the sidewall portion in the point B is tangent to a circle C2 centred on a radially outward chipper end; and further wherein the distance of the point A from the ply ending is ranging from 10 mm to 30 mm.

16. The radial tire of claim 15 wherein the circle C1 centred on the ply ending has a radius R1 ranging from 5 mm to 15 mm.

17. The radial tire of claim 15 wherein the circle C2 centred on the radially outward chipper end has a radius R2 ranging from 2 mm to 12 mm.

18. The radial tire of claim 15 wherein the distance G is equal to or lower than the radius R1 of the circle C1 centred on the ply ending.

19. The radial tire of claim 15 wherein the tire has an aspect ratio of at least 60.

20. The radial tire of claim 1 wherein the tire is a heavy load tire and/or has a nominal bead diameter of at least 22.5 inches, and the tire has an aspect ratio of at least 70.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0060] FIG. 1 is a schematic cross-sectional view of an exemplary tire of the prior art.

[0061] FIG. 2 is an enlarged fragmentary view of the bead portion of the tire shown in FIG. 1.

[0062] FIG. 3 is an enlarged fragmentary view of the bead portion of an exemplary embodiment of the tire of the present disclosure.

[0063] Similar numeral refers to similar parts are used throughout the drawings.

DETAILED DESCRIPTION OF THE INVENTION

[0064] An exemplary embodiment of the radial tire of the present disclosure is shown in FIG. 3 and is indicated as reference numeral 21. The general construction of the tire is somewhat similar to that of the prior art tire 1, with the principal differences to be described in detail below. The radial tire 21 (of the subject invention) is preferably a pneumatic radial tire.

[0065] The tire 21 includes a pair of bead portions 23 (only one shown) and a respective bead core 25 embedded in each bead portion 23. The bead core 25 can comprise a wound steel wire coated with rubber or a wound of high modulus organic cord coated with rubber, such as aromatic polyamide. A respective sidewall portion 27 extends radially outward from each bead portion 23 to a ground-contacting tread (not shown). A carcass reinforcing ply 29 that preferably winds around each bead core 25. The carcass reinforcing ply 29 comprises cords preferably, steel cords and/or organic fibre cords. The organic fibre cords can be selected from polyester, rayon, nylon, aromatic polyamide and any combination thereof. A main portion 31 of the carcass reinforcing ply extends radially inward toward the tire rim (not shown) and is turned about each bead core 25 to form a ply turnup 33. The carcass reinforcing ply is also wrapped about a bead apex (not shown). In this manner, the carcass reinforcing ply envelopes the bead core 25 and at least a lower portion of the bead apex in each bead portion 23. The ply turnup 33 terminates at a radially outward end forming a ply ending 35 and may include an end cap (not shown). The carcass reinforcing ply 29 is preferably formed by a single layer of reinforcing elements.

[0066] A chipper 37 is disposed about the radially inward surface of the ply turnup 33. The chipper 37 terminates at a radially outward end 39 and may include an end cap (not shown). The radially outward chipper end 39 is axially outward from the ply ending 35 and is axially outward from an opposite chipper end 41. For example, the height of the outward ply ending 35 is at least 35 mm; for example, at least 38 mm; for example, at least 40 mm; for example, at least 42 mm. The height of the outward ply ending is determined in the radial direction and measured from the bead toe 49.

[0067] The radially outward chipper end 39 is preferably radially below the ply ending 35. In other words, the ply ending 35 extends over height in the sidewall 27 higher than the radially outward chipper end 39. The ply ending 35 and the radially outward chipper end 39 are preferably separated by a distance of at least 8 mm; preferably of at least 10 mm; and more preferably, of at least 12 mm. The ply ending 35 and the radially outward chipper end 39 are preferably separated by a distance of at most 30 mm; preferably of at most 25 mm; and more preferably, of at most 20 mm.

[0068] For example, the height of the radially outward chipper end 39 is at most 40 mm; for example, at most 35 mm; for example, at most 30 mm; for example, at most 25 mm. The height of the radially outward chipper end 39 is determined in the radial direction and measured from the bead toe 49.

[0069] It is preferred that at least one of the ply ending 35 and/or the radially outward chipper end 39 include an end cap so that the ply ending portion and the outward chipper ending portion are not parallel and are separated by a strip of rubber.

[0070] The opposite end 41 of the chipper 37 is also preferably radially below the ply ending 35. The opposite end 41 of the chipper 37 is preferably located in the bead portion 23. The opposite end 41 of the chipper 37 preferably extends over height in the bead portion 23 higher than the radially outward surface of the bead core 25. For example, the height of the opposite chipper end 41 is at least 25 mm; for example, at least 30 mm; for example, at least 35 mm; for example, at least 40 mm. For example, the height of the opposite chipper end 41 is at most 60 mm; for example, at most 55 mm; for example, at most 50 mm; for example, at most 45 mm. The height of the opposite chipper end 41 is determined in the radial direction and measured from the bead toe 49.

[0071] The profile of the outer surface 43 of the sidewall portion 27 of the tire 21 is at a distance G from the carcass reinforcing ply 29 from the most axially outward point of the said outer surface until point A and joins the outer surface of the bead portion 23 at the point B. Between the points A and B, the outer surface 43 follows two successive curves with a first curve 45 extending from the point A and having a centre of curvature positioned axially outward of the carcass reinforcing ply 29; and a second curve 47 joining the point B having a centre of curvature positioned axially inward of the outer surface of the tire. The outer surface of the tire includes the outer surface 43 of the sidewall portion and the outer surface of the bead portions. In a preferred embodiment, the distance G is constant. The distance G is preferably within the range of 2 mm to 10 mm, more preferably ranging from 3 mm to 7 mm. In an embodiment, the distance G is equal to or lower than the radius R1 of the circle C1 centred on the ply ending 35. The distance G is said constant when it does not vary by more than 0.5 mm. The variations in the distance are due to creep phenomena during the manufacture and curing of the tire.

[0072] In an embodiment, the distance between the ply ending 35 and the radially outward chipper end 39 is equal to or lower than the distance of the point A from the ply ending 35; i.e. the distance of the ply ending 35 and the radially outward chipper end 39 is equal to or lower than 30 mm, preferably equal or lower than 28 mm, more preferably equal or lower than 25 mm.

[0073] According to the present disclosure, the profile of the outer surface of the sidewall of the tire in the portion extending from points A to B is tangent to a circle C1 centred on the ply ending 35 and is tangent to a circle C2 centred on the radially outward chipper end 39. With preference, the portion extending from points A to B is a spline comprising two curves (45, 47) showing the radii of curvature reversed and arranged end to end or separated by a flat portion. The spline is preferably tangent to circle C2 in point B and tangent to circle C1 in a point different from point B. The spline is preferably tangent to circle C1 in a point located between points A and B. For example, when the spline comprises a flat portion, the flat portion has a length ranging from 0.5 mm to 2.0 mm; preferably ranging from 0.8 mm to 1.5 mm. For example, when the spline comprises a flat portion, the spline can be tangent to circle C1 in a point located in the flat portion arranged between the first curve 45 and the second curve 47.

[0074] The circle C1 centred on the ply ending 35 has preferably a radius R1 ranging from 5 mm to 15 mm. For example, the radius R1 of the circle C1 is at least 5 mm, or at least 7 mm, or at least 9 mm. For example, the radius R1 of the circle C1 is at most 15 mm, or at most 13 mm, or at most 11 mm.

[0075] The circle C2 centred on the radially outward chipper end 39 has preferably a radius R2 ranging from 2 mm to 12 mm. For example, the radius R2 of the circle C2 is at least 2 mm, or at least 5 mm, or at least 7 mm. For example, the radius R2 of the circle C2 is at most 12 mm, or at most 10 mm, or at most 9 mm, or at most 8 mm.

[0076] In an embodiment, the circle C1 centred on the ply ending 35 has a radius R1 equal to or greater than the radius R2 of the circle C2 centred on the radially outward chipper end 39.

[0077] It is understood that, by comparison to the prior art tire of the same size, the portion of the sidewall of the tire which shows a defined constant gauge is extended in height. As a consequence, the outer surface of the sidewall seems to present an outer cavity. This was found to lead to a tire with a reduced rolling resistance with an acceptable trade-off on bead durability due to a reasonable distance kept between the outer surface of the tire (i.e. the outer cavity) and both the ply ending 35 and the radially outward chipper end 39. Also, a reduction of heat accumulation was seen.

[0078] The shape of the outer surface of the sidewall is tangent to both the circles C1 and C2 centred on the ply ending 35 and the radially outward chipper end 39, this contributes to obtaining a smooth surface between the sidewall and the bead portion that has been shown to avoid the concentration of strain in the rubber and therefore to be favourable to the durability of the tire.

[0079] The trade-off of bead durability according to the disclosure is obtained, among others, by a distance of the point A from the ply ending 35 of at most 30 mm; preferably at most 28 mm and more preferably at most 25 mm. It is preferred that the distance of the point A from the ply ending is at least 10 mm; preferably at least 12 mm; more preferably of at least 15 mm. So that the distance of the point A from the ply ending 35 ranges from 10 mm to 30 mm; preferably ranging from 12 mm to 28 mm and more preferably from 15 mm to 25 mm. According to the disclosure, the distance of point A from the ply ending 35 is less than the distance of point A from the radially outward chipper end 39.

[0080] The first curve 45, extending from the point A, has a radius of curvature R3 that is greater than the radius R1 of the circle C1 and/or that is greater than the radius R2 of the circle C2. The second curve 47, joining the point B, is having a radius of curvature R4 that is greater than the radius R1 of the circle C1 and/or that is greater than the radius R2 of the circle C2. For example, the radius of curvature R3 is higher than the radius of curvature R4. For example, the radius of curvature R3 is ranging from 1.2 to 5 times the radius of curvature R4; preferably, from 1.5 to 4 times.

[0081] The apex is at least partially located in the ply turnup portion immediately adjacent to the bead core 25. The apex not only aids in mating the ply turnup 33 to main portion 31 of the carcass reinforcing ply 29 but also prevents any air pockets from being trapped in the sidewall 27 of the tire 21 during manufacturing.

[0082] The durability of the tire 21 is obtained by the combination of the internal structure of the tire 21 wherein a gap is found between the ply ending 35 and the radially outward chipper end 39, and the shape of the outer surface 43 of the sidewall portion 27 between the points A and B. Also, the smooth shape of the spline forming the outer surface 43 of the sidewall portion 27 that joins the bead portion on point B avoids a concentration of strain in the bead portion 23 and the sidewall portion 27 and facilitates the manufacture of the tire 21.

Example

[0083] A radial tire with a design according to the disclosure was produced and tested. The tire was a 315/70R22.5, wherein 315 is the nominal cross-section given in mm (metric), 70 is the aspect ratio, R is for radial and 22.5 is the nominal bead diameter (also named nominal wheel diameter) given in inches. The radius R1 of circle C1 centred on the ply ending was 9 mm. The radius R2 of circle C2 centred on the radially outward chipper end was 6 mm. The ply ending height was 42 mm. The ply ending and the radially outward chipper end were separated by a distance of 10 mm.

[0084] The rolling resistance and durability of the tire were evaluated.

[0085] The rolling resistance test was run in accordance with ISO 28580 (tire rolling on a drum of 67″ dia).

[0086] Durability test: Tire mounted on a rim 9″×22.5″, at 5000 kg load and 10 bar pressure, rolling on a 67″ dia drum machine at 60 km/h speed.

[0087] The test values were normalized and reported in the below table:

TABLE-US-00001 Standard New design Rolling resistance 100 102 Durability 100 99.5 Weight 100 102

[0088] An improvement in rolling resistance (RR) performance (i.e. normalized value over 100) means lower rolling resistance. An improvement in weight performance (i.e. normalized value over 100) means a lighter tire. An improvement in durability (i.e. normalized value over 100) means higher durability.

[0089] From the results, it can be seen that the performance is rolling resistance and weight of the tire have been improved (+2) whereas no significant loss in the durability performance can be observed (−0.5). The design of the disclosure provides therefore an improved compromise between rolling resistance, durability and weight performance.

[0090] Tests on heat generation by Finite Element Analysis were performed on a tire in the same RR test conditions as ISO 28580. The temperature profile showed that a reduction of the heat generation of several degrees was obtained on the design of the disclosure by comparison to a tire comprising a design according to FIG. 2.

[0091] It is to be understood that the structure of the above-described tire 21 may be altered or rearranged, or components or steps known to those skilled in the art omitted or added, without affecting the overall concept or operation of the disclosure. For example, the teachings herein apply to a broad range of tires and may be useful in tire lines such as, but not limited to, passenger tires, radial medium truck tires, aircraft tires, and off-the-road tires, run-flat tires, and the like. It is preferred that the tire 21 be a heavy load tire. For example, the tire is a commercial truck tire that includes a nominal bead diameter of at least 22.5 inches.

[0092] For example, the tire has an aspect ratio of at least 60; preferably of at least 70. For example, the tire has an aspect ratio ranging from 60 to 90, or from 70 to 90 or from 60 to 80.

[0093] Moreover, the disclosure applies to tires formed with any type of belt structure or tread configuration.

[0094] The disclosure has been described with reference to preferred embodiments. Potential modifications and alterations will occur to others upon a reading and understanding of this description. It is to be understood that all such modifications and alterations are included in the scope of the disclosure as set forth in the appended claims, or the equivalents thereof. While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention.