RADIAL TIRE

Abstract

A radial tire includes a pair of bead cores, a carcass layer having one or more carcass plies extending from one of the bead cores to another of the bead cores, a tread portion circumferentially encircling the toroidal form of the carcass layer, and a belt structure. The belt structure includes a radially innermost main belt layer, a first, unreinforced cushion layer disposed on a radially outer side of the main belt layer, a second, unreinforced cushion layer disposed on a radially outer side of the first cushion layer, and a protective belt layer disposed between a radially outer side of the second cushion layer and a radially inner side of the tread portion. A radially outermost layer of the main belt layer has reinforcement cords with a specified diameter. The first cushion layer has a radial thickness between 0.5 and 4.0 times the specified diameter.

Claims

1. A radial tire comprising: a pair of bead cores; a carcass layer having one or more carcass plies extending from one of the bead cores to the other of the bead cores in a toroidal form; a tread portion circumferentially encircling the toroidal form of the carcass layer; and a belt structure having a radially innermost main belt layer, a first, unreinforced cushion layer disposed on a radially outer side of the main belt layer, a second, unreinforced cushion layer disposed on a radially outer side of the first cushion layer, and a protective belt layer disposed between a radially outer side of the second cushion layer and a radially inner side of the tread portion, a radially outermost layer of the main belt layer having reinforcement cords with a specified diameter, the first cushion layer having a radial thickness between 0.5 and 4.0 times the specified diameter.

2. The radial tire as set forth in claim 1 wherein the first cushion layer has a radial thickness between 0.5 and 2.5 times the specified diameter.

3. The radial tire as set forth in claim 1 wherein the first cushion layer has an axial width between 0.5 and 1.1 times a maximum overall axial width of the belt structure.

4. The radial tire as set forth in claim 1 wherein the first cushion layer has an axial width between 0.5 and 0.9 times a maximum overall axial width of the belt structure.

5. The radial tire as set forth in claim 1 wherein the second cushion layer has a radial thickness between 1.5 and 5.0 times the specified diameter.

6. The radial tire as set forth in claim 1 wherein the second cushion layer has a radial thickness between 1.5 and 3.5 times the specified diameter.

7. The radial tire as set forth in claim 1 wherein the reinforcement cords of the radially outermost layer of the main belt layer have a plurality of organic fiber, merged cords.

8. The radial tire as set forth in claim 1 wherein the protective belt layer has organic fiber cords.

9. The radial tire as set forth in claim 1 wherein the carcass layer has organic fiber cords.

10. The radial tire as set forth in claim 1 wherein the main belt layer has a first axial width and the protective belt layer has a second axial width, a ratio of the second axial width to the first axial width being between 0.25 and 1.20.

11. A tread for a radial tire comprising: a plurality of circumferentially extending tread grooves; one circumferentially extending center rib defined by two of the tread grooves, a radially outer surface of the center rib having a first radius of curvature; two circumferentially extending intermediate ribs defined by the tread grooves, a radially outer surface of each intermediate rib having a second radius of curvature; and two circumferentially extending shoulder ribs defined by the tread grooves, a radially outer surface of each shoulder rib having a third radius of curvature and a different fourth radius of curvature, the third radii each being disposed adjacent one of the tread grooves, the fourth radii each being disposed adjacent an axial outer edge of the tread, the second radii each being greater than the first radius.

12. The tread as set forth in claim 11 wherein the first radius is greater than each of the third radii.

13. The tread as set forth in claim 11 wherein the first radius is greater than each of the fourth radii.

14. The tread as set forth in claim 11 wherein the third radii are greater than each of the fourth radii.

15. The tread as set forth in claim 11 wherein the second radii are greater than each of the fourth radii.

16. A radial tire comprising: a pair of bead cores; a carcass layer having one or more carcass plies extending from one of the bead cores to the other of the bead cores in a toroidal form; a tread portion circumferentially encircling the toroidal form of the carcass layer; and a belt structure having a radially innermost main belt layer, a first, unreinforced cushion layer disposed on a radially outer side of the main belt layer, a second, unreinforced cushion layer disposed on a radially outer side of the first cushion layer, and a protective belt layer disposed between a radially outer side of the second cushion layer and a radially inner side of the tread portion, the tread portion including a plurality of circumferentially extending tread grooves, one circumferentially extending center rib defined by two of the tread grooves with a radially outer surface with a first radius of curvature, two circumferentially extending intermediate ribs defined by the tread grooves with a radially outer surface of each intermediate rib having a second radius of curvature, and two circumferentially extending shoulder ribs defined by the tread grooves, the second radii each being greater than the first radius.

17. The radial tire as set forth in claim 16 wherein the main belt layer has a first axial width and the protective belt layer has a second axial width, a ratio of the second axial width to the first axial width being between 0.50 and 0.90.

18. The radial tire as set forth in claim 16 wherein an organic fiber cord of the main belt layer includes aramid and an organic fiber cord of the protective belt layer includes nylon.

19. The radial tire as set forth in claim 16 wherein a ratio of an axial width of the first cushion layer to a maximum axial width of the belt structure is between 0.5 and 1.1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0096] The present invention will be described by way of example and with reference to the accompanying drawings, in which:

[0097] FIG. 1 is a schematic sectional view of an example radial tire according to the present invention.

[0098] FIG. 2 is a schematic detail view of part of the radial tire of FIG. 1.

[0099] FIG. 3 is a schematic detail view of another part of the radial tire of FIG. 1.

DESCRIPTION OF AN EXAMPLE OF THE PRESENT INVENTION

[0100] One example for carrying out the present invention will be described with reference to FIGS. 1-3 below. An example aircraft radial tire 10 may have a bead portion 12 with two bead cores 14, each having a circular cross section. A carcass layer 16 may include six or more example carcass plies (not shown) in which rubber-coated organic fiber cords may be arranged in a radial direction forming sidewalls 19 retained by the bead cores 14. Note that, since other structures, such as a flipper, a chafer, a chipper, etc. may be similar to conventional structures and are not illustrated in FIG. 1.

[0101] The carcass layer 16 may utilize an example organic fiber cord having a tensile fracture strength of 6.3 cN/dtex or higher, an elongation percentage of 0.2 to 1.8 percent when a load is 0.2 cN/dtex in the elongating direction, an elongation percentage of 1.4 to 6.4 percent when a load is 1.0 cN/dtex in the elongating direction, and an elongation percentage of 2.1 to 8.6 percent when a load is 2.9 cN/dtex in the elongating direction. The organic fiber cord of the carcass layer 16 may be an aromatic polyamide fiber with an inner-layer coefficient of 0.12 to 0.85, or 0.17 to 0.51, and an outer-layer coefficient of 0.4 to 0.85.

[0102] The carcass layer 16 may utilize another example organic fiber cord having a tensile fracture strength of 6.3 cN/dtex or higher, an elongation percentage of 0.2 to 2.0 percent when a load is 0.3 cN/dtex in the elongating direction, an elongation percentage of 1.5 to 7.0 percent when a load is 2.1 cN/dtex in the elongating direction, and an elongation percentage of 2.2 to 9.3 percent when a load is 3.2 cN/dtex in the elongating direction. The organic fiber cord of the carcass layer 16 may be an aromatic polyamide fiber with an inner-layer coefficient of 0.12 to 0.85, or 0.17 to 0.51, and an outer-layer coefficient of 0.4 to 0.85.

[0103] The organic fiber cord of the carcass layer 16 may be a merged, or hybrid, cord including aromatic polyamide fiber and aliphatic polyamide fiber. The weight ratio of the aromatic polyamide fiber and the aliphatic polyamide fiber may be from 100:27 to 100:255. Additionally, nylon may be used for part or all of the merged cord.

[0104] A belt structure 20, on a radially outer side of the carcass layer 16, may include a main belt layer 26 disposed on a radially inner side of the belt structure and a protective belt layer 28 provided on a radially outer side of the belt structure. The belt structure may have a maximum overall axial width BW. The main belt layer 26 may have a larger first axial width BW and the protective belt layer 28 may have a smaller second axial width CPW. A ratio of the second axial width and the first axial width may be between 0.25 and 1.20, or between 0.75 and 0.95.

[0105] The main belt layer 26 may be formed of a plurality of belt plies, from 2 to 16, or 8. The widths of the belt plies may be the same as each other or varying widths. The inclination angle of the organic fiber cord, or cord angle, may be between 1 and 45 degrees, or 10 and 45 degrees, with respect to the equatorial plane. The density of multiple organic fiber cords may be in a range of 4.0 cords/10 mm to 10.0 cords/10 mm, or 7.0 cords/10 mm.

[0106] The organic fiber cord(s) of the main belt layer 26 of the belt structure 20 may be a merged, or hybrid, cord including aromatic polyamide fiber and aliphatic polyamide fiber. The weight ratio of the aromatic polyamide fiber and the aliphatic polyamide fiber may be from 100:27 to 100:255. Additionally, nylon may be used for part or all of the example merged cord.

[0107] The protective belt layer 28 of the belt structure 20 may have an axial width CPW less than the axial width BW of the belt structure 20, or 0.25 BW to 1.2 BW, or 0.5 BW to 0.8 BW. The protective belt layer 28 may be formed of one or more belt plies. Additionally, the belt ply or plies 26 or the ply or plies of the protective belt layer 28 may be formed with one or more organic fiber cords coated with rubber to form band-like thin bodies wound such that, whenever the thin bodies are wound once, or 360, the thin bodies may reciprocate between both axial ends of the plies and the thin bodies may be inclined at an angle of 0 to 25 degrees with respect to the equatorial surface, and this winding may be carried out many times while offsetting the thin bodies as substantially the same distance as their widths in the circumferential direction such that no gap is generated between the thin bodies (this is called endless zigzag-wound belt, hereinafter), as disclosed in US 2017/0253085, hereby incorporated by reference in its entirety. As a result, the organic fiber cord(s), extending in substantially the circumferential direction in a zigzag manner, may be embedded in the entire region of the belt ply or plies substantially uniformly by changing the bending direction at the both axial ply ends. The angle of the organic fiber cord(s) of the main belt layer 26 may be less than the angle of the organic fiber cord(s) of the protective layer 28.

[0108] In the protective belt layer 28, the organic fiber cord(s) may have an elastic modulus equal to or less than that of the elastic modulus of the organic fiber cords included in the main belt layer 26. Example organic fiber cords for the protective layer 28 may include an aliphatic polyamide fiber, such as nylon, or a merged cord with an aromatic polyamide fiber, such as aramid, and an aliphatic polyamide fiber, such as nylon. The protective layer 28 may include an endless zigzag-wound belt having an inclination angle of the organic fiber cord being in a range of 0 to 25 degrees with respect to the equatorial plane, or an angle of 10 degrees.

[0109] In accordance with one feature of the present invention, as shown in FIGS. 2-3, the cords 261 of the radially outermost belt ply 26 may have a uniform diameter C.sub.d. The minimum thickness t.sub.1 of a first, unreinforced (e.g., lacking cord reinforcement, etc.) rubber layer 30, or first cushioning layer, radially between the cord(s) of the main belt layer 26 and a second, unreinforced rubber layer 32, or second cushioning layer, may be in a range of 0.5 C.sub.d to 4.0 C.sub.d or 1.0 C.sub.d to 2.5 C.sub.d. The first rubber layer 30 may have an axial width CW of 0.5 BW to 1.1 BW or 0.5 BW to 0.9 BW. The radial thickness of axially outer edges of the first rubber layer 30 may taper radially inward (FIG. 2). The first, unreinforced rubber layer 30 may also comprise multiple layers with an overall thickness within the above ranges. Tread buffing during tire retreading may occur at the second rubber layer 32.

[0110] The minimum thickness t2 of the second rubber layer 32 between the first rubber layer 30 and the protective layer 28 may be in a range of 1.5 C.sub.d to 5.0 C.sub.d or 1.5 C.sub.d to 3.5 C.sub.d. The second, unreinforced rubber layer 32 may also comprise multiple layers with an overall thickness within the above ranges. If the thickness t.sub.2 of the second rubber layer 32 is too small, when retreading the tire 10, it may become difficult to remove the rubber layers 32 without damaging the radially inner main belt layer 26. Conversely, if the thickness of the rubber layers 30, 32 is too large, not only the weight of the tire 10 increases, but also heat generation of the tread layer 18 increases, which are both disadvantageous for the performance of the tire. The thickness t.sub.2 of the second rubber layer 32 may allow removal of the protective layer 28 during retread operations.

[0111] In accordance with another feature of the present invention, as shown in FIG. 1, the tread layer 18 may include circumferentially extending tread grooves 181 separating two circumferentially extending shoulder ribs 182, 186, two circumferentially extending intermediate ribs 183, 185, and one circumferentially extending center rib 184. The radially outermost surface of the center rib 184 may have a radius of curvature TR.sub.1. The radially outermost surfaces of the intermediate ribs 183, 185 may have radii of curvature TR.sub.2. The radially outermost surfaces of the shoulder ribs 182, 186, adjacent the grooves 181, may have a radius of curvature TR.sub.3. The radially outermost surfaces of the shoulder ribs 182, 186, adjacent the axially outer portions of the sidewalls 19, may have a radius of curvature TR.sub.4. TR.sub.2 may be larger than TR.sub.1. Further, TR.sub.2 may be larger than TR.sub.1, TR.sub.1 may be larger than TR.sub.3, and TR.sub.3 may be larger than TR.sub.4.

[0112] The tire 10 according to the present invention has been described in detail. However, the present invention is not limited to the above example, and various modifications of the example may also apply. Numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the present invention may be practiced otherwise than as specifically and exemplarily described herein.

[0113] Further, variations in the present invention are possible in light of the description of it provided herein. 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. It is, therefore, to be understood that changes may be made in the particular examples described which will be within the fully intended scope of the present invention as defined by the following appended claims.